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Jan 1980

Volume 17, Issue 1, pp. 1-538


Frontiers in microelectronics and thin film components

C. B. Duke

J. Vac. Sci. Technol. 17, 1 (1980); http://dx.doi.org/10.1116/1.570431 (8 pages) | Cited 2 times

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This paper is the text of an address delivered by the outgoing president of the American Vacuum Society at the Society’s annual meeting in 1979. Following a brief outline of the mission, functions, and organization of the Society, a discussion of trends in the fabrication of modern microelectronics is presented together with an outline of the Society’s activities which contribute toward these trends. The address concludes with a consideration of the consequences of these trends for the American Vacuum Society and an indication of the unique roles of a multidisciplinary organization like the American Vacuum Society in the American Institute of Physics.
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01.30.Bb Publications of lectures (advanced institutes, summer schools, etc.)
07.30.-t Vacuum apparatus
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Quantitative examination of individual atomic events on solids

Gert Ehrlich

J. Vac. Sci. Technol. 17, 9 (1980); http://dx.doi.org/10.1116/1.570515 (6 pages) | Cited 8 times

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The behavior of individual atoms on solids has long been of interest for understanding the physical and chemical properties of surfaces. Now, through the use of the field ion microscope, it is possible to directly image single atoms on metal surfaces and to examine their properties quantitatively. Such studies are reviewed, with special emphasis on: (1) surface structure and its effect on diffusion; (2) the details of the jump process; (3) interactions between atoms leading to cluster formation; and (4) the properties of clusters.
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.37.Vj Field emission and field-ion microscopy
66.30.-h Diffusion in solids

Chemistry of solid–solid interfaces — A review of its characterization, theory, and relevance to materials science

M. P. Seah

J. Vac. Sci. Technol. 17, 16 (1980); http://dx.doi.org/10.1116/1.570464 (9 pages) | Cited 7 times

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The chemistry of solid–solid interfaces in metals is reviewed in relation to its characterization, theory, and relevance to materials science. The current techniques for measuring interface segregation, AES, STEM with x‐ray analysis, and mass‐resolved field desorption microscopy, are outlined and their advantages discussed. The expression of quantitative measurements from these techniques is unified. The behavior of segregation is discussed for the experimental variables—localization, crystal orientation, chemical system, time, and temperature. The theories to describe segregation in binary and ternary systems are then presented together with the analysis of the kinetics of segregation. The importance of these different aspects arises in a number of segregation sensitive materials properties. These will be described together with remedial procedures that result from the characterizations.
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
82.20.Hf Product distribution
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination

Sulfur and oxygen chemistry at free surfaces and grain boundaries of iron alloys

M. T. Thomas, D. R. Baer, R. H. Jones, and S. M. Bruemmer

J. Vac. Sci. Technol. 17, 25 (1980); http://dx.doi.org/10.1116/1.570406 (4 pages) | Cited 3 times

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This paper reports a study of grain boundary and free surface segregation in iron alloys. Scanning Auger electron spectroscopy has been used to analyze the extent and spatial distribution of the segregants. It is found that there is a similarity between free surface and grain boundary segregation for vacuum‐melted (vm) and zone‐refined (zr) materials. S and O are the primary segregants to grain boundaries for vm samples, while N is the predominant segregant for zr material. When O and S are the primary segregated elements, a site competition between them is observed on both the free surface and at grain boundaries. On the free surface the site competition is dependent on grain orientation.
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

AES study of sulfur surface segregation on polycrystalline copper

B. Singh, R. W. Vook, and E.‐A. Knabbe

J. Vac. Sci. Technol. 17, 29 (1980); http://dx.doi.org/10.1116/1.570418 (5 pages) | Cited 5 times

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The surfaces of four polycrystalline copper samples were examined under UHV conditions by AES: OFHC Cu, 99.99% Cu, 99.9999% Cu, and 0.086 wt. % Ag in OFHC Cu. Surface chemical compositions in the range of 25°–600°C were determined. Sulfur concentrations on the surfaces at various temperatures were also measured as a function of time. In almost all cases the sulfur concentration increased as (time)1/2. This process was interpreted in terms of a model based on diffusion controlled ’’outgassing’’ in which the sulfur segregated to the surface instead of vaporizing. The activation energies for this process for the four samples ranged from 0.18 to 0.31 eV/atom. RHEED data from an OFHC Cu sample indicated that sulfur formed an orthorhombic Cu2S structure on the surface. Around 500°C the Ag–Cu alloy experienced a complex, rapid stage of segregation of sulfur. Above this temperture range the surface sulfur concentration dropped rapidly, reaching zero at 600°C.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
66.30.J- Diffusion of impurities
64.75.-g Phase equilibria

Summary Abstract: Electrical and compositional properties of grain boundaries in multigrained silicon using surface analysis techniques

L. L. Kazmerski, P. J. Ireland, and T. F. Ciszek

J. Vac. Sci. Technol. 17, 34 (1980); http://dx.doi.org/10.1116/1.570384 (2 pages)

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Abstract Unavailable
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82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
61.72.-y Defects and impurities in crystals; microstructure
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
84.60.Jt Photoelectric conversion

Matrix effect in SIMS analysis using an O2+ primary beam

Ming L. Yu and Wilhad Reuter

J. Vac. Sci. Technol. 17, 36 (1980); http://dx.doi.org/10.1116/1.570390 (4 pages) | Cited 9 times

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We have observed large matrix effects in the secondary ion emission from alloys when bombarded with an O+2 beam. Binary alloys of Ni with Cr, Fe, and Cu were studied. Chromium, which reacted most strongly with oxygen, induced the largest enhancement of the Ni+ ionization probability. Iron enhanced the Ni+ ionization probability to a lesser extent, whereas copper resulted in a decrease of the Ni+ ionization probability. Ni also induced a small enhancement of the ionization probability of Cr. We find a strong correlation of the mean free energy of formation of the metal‐oxide bond with the observed trends in the ionization probabilities. These matrix effects can cause artifacts in the depth profiling of metal film structures where interdiffusion at the interface leads to the formation of alloys or intermetallic compounds. This is indeed observed when interfaces of Ni–Fe and Ni–Cr films are studied by SIMS.
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82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Characterization of AlxGa1−xAs–GaAs layer structures by scanning Auger electron microscopy

A. van Oostrom, L. Augustus, W. Nijman, and W. Leswin

J. Vac. Sci. Technol. 17, 40 (1980); http://dx.doi.org/10.1116/1.570468 (4 pages) | Cited 2 times

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Crater‐edge and conventional depth profiling have been used to characterize epitaxial films of AlxGa1−xAs grown by LPE on GaAs (100) substrates. In order to reduce damage low energy (?500 eV) argon ions were used. From the high energy Auger transitions values of x were derived with an accuracy Δx=0.01. Minimum chemical interface widths were observed of 2.5 nm, independent of depth below the surface.
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79.20.Fv Electron impact: Auger emission
68.55.-a Thin film structure and morphology
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Sputter‐induced roughness in thermal SiO2 during Auger sputter profiling studies of the Si–SiO2 interface

C. F. Cook, C. R. Helms, and D. C. Fox

J. Vac. Sci. Technol. 17, 44 (1980); http://dx.doi.org/10.1116/1.570480 (3 pages) | Cited 11 times

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We have used transmission electron microscopy replica techniques in conjunction with Auger sputter profiling (ASP) to study the effect of sputtering on the morphology of SiO2 surfaces. 1 keV Ar ions incident 49° from the surface normal induce a ridge and valley structure with the ridges running normal to the ion beam direction. The degree of roughness is proportional to the amount of SiO2 removed by sputtering and appears to have no effect on the width of the Si–SiO2 interface as seen by ASP.
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68.35.Ja Surface and interface dynamics and vibrations
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Summary Abstract: Synthesis and catalytic reactions of Zr(BH4)4 on Al2O3 characterized by inelastic electron tunneling spectroscopy

H. E. Evans and W. H. Weinberg

J. Vac. Sci. Technol. 17, 47 (1980); http://dx.doi.org/10.1116/1.570488 (2 pages) | Cited 1 time

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Abstract Unavailable
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68.35.Ja Surface and interface dynamics and vibrations
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
79.60.Dp Adsorbed layers and thin films
79.70.+q Field emission, ionization, evaporation, and desorption

Electrochemistry of single‐crystal surfaces

Arthur T. Hubbard

J. Vac. Sci. Technol. 17, 49 (1980); http://dx.doi.org/10.1116/1.570493 (6 pages) | Cited 3 times

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Well‐defined surfaces functioning as electrodes in solution are yielding electrochemical information from which the role of surface structure can be seen clearly for the first time. Techniques, results, and conclusions of recent work in this new area are reviewed and analyzed. Experimental procedures for transferring the surface between vacuum and solution without contamination have been perfected. Low‐index planes and ordered overlayers are surprisingly stable toward electrolytic solutions. Electrode reactions are sensitive to substrate orientation and superlattice structure. Practical polycrystalline electrodes behave as mixtures of low‐index planes; accordingly, the import of well‐defined surface experimentation extends to nonideal materials.
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61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
82.45.-h Electrochemistry and electrophoresis
82.80.Fk Electrochemical methods
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

AES and XPS study of plutonium oxidation

D. T. Larson

J. Vac. Sci. Technol. 17, 55 (1980); http://dx.doi.org/10.1116/1.570503 (4 pages) | Cited 7 times

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The initial oxidation of plutonium metal at 27°C has been studied using AES and XPS. Initially a ’’clean’’ plutonium surface was prepared by prolonged Ar+ bombardment followed by 500°C anneal and Ar+ bombardment cleaning cycles. Changes occurring in the plutonium Auger electron spectra in the energy range of 40–120 eV and the 4f5/2, 4f7/2 (core levels), and valence band XPS peaks were monitored during oxygen exposures of 10 to 1.8×108L. Examination of the 4f7/2 level revealed two oxidation states which are attributed to a suboxide an PuO2. The 4f7/2 binding energies for the two oxidation states and plutonium metal are 426.1, 424.4, and 422.2 eV, respectively. It was observed that oxidation proceeded in two steps. In the first step there was a rapid reaction of oxygen with the formation of a suboxide. In the second stage, the uptake of oxygen leveled off with conversion of the suboxide to PuO2.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
79.20.Fv Electron impact: Auger emission
33.60.+q Photoelectron spectra
81.05.Bx Metals, semimetals, and alloys

Extended appearance potential fine structure analysis of oxidized metal surfaces

M. L. den Boer, T. L. Einstein, W. T. Elam, Robert L. Park, L. D. Roelofs, and G. E. Laramore

J. Vac. Sci. Technol. 17, 59 (1980); http://dx.doi.org/10.1116/1.570504 (4 pages)

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Like EXAFS, extended appearance potential fine structure (EAPFS) probes the immediate neighborhood of a particular element and thus, unlike most other structural probes, does not require long‐range order. Furthermore, the use of low‐energy electron makes the technique surface sensitive. Because no dipole selection rules apply to electron excitation, explicit calculation must determine the angular momentum of the outgoing final‐state electron and thus the feasibility of Fourier inversion of the data. For excitation of the O 1s core, we find the outgoing electron is overwhelmingly s‐wave. Reaction of Al(100) with about 1‐1/2 equivalent monolayers of oxygen disorders the surface completely (i.e., extinguishes the LEED pattern). For this surface, analysis of the O 1s edge gives an O–Al distance of 1.98±0.05 Å, the longer of the two Al–O spacings in bulk Al2O3, which indicates that the oxygen goes under the top layer of Al. For a thick oxide layer on Ni(100), diffraction effects precluded use of the O 1s edge. From Ni 2p data, for which the angular momentum selection is weaker, we can extract the bulk Ni–O distance by using plausible phase shifts.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
61.05.J- Electron diffraction and scattering

Summary Abstract: Atom probe FIM—A thin film characterization technique

S. V. Krishnaswamy, R. Messier, Yee S. Ng, and T. T. Tsong

J. Vac. Sci. Technol. 17, 63 (1980); http://dx.doi.org/10.1116/1.570505 (2 pages)

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Abstract Unavailable
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68.37.Vj Field emission and field-ion microscopy
68.55.-a Thin film structure and morphology
07.75.+h Mass spectrometers

Advanced undergraduate experiments in vacuum physics and mass spectrometry

I. Golecki and J. Rossel

J. Vac. Sci. Technol. 17, 66 (1980); http://dx.doi.org/10.1116/1.570506 (3 pages) | Cited 4 times

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A comprehensive high‐vacuum system has been set up and operated in an advanced undergraduate laboratory for students majoring in physics and microelectronics. The aim of the experiment is to provide the students with both practical experience and basic theoretical understanding of the production and measurement of low pressures. The students measure the pumping speed of a rotary forepump and of an oil diffusion pump, as a function of pressure, using procedures adopted by the AVS. A hot‐cathode ionization gauge and a thermocouple gauge are calibrated against a McLeod (absolute) manometer for several gases. The compositions of ambient air, of an isotopic mixture of neon, and of the residual gases in an oil‐diffusion‐pumped system are determined with the aid of a mass spectrometer. The influence of a liquid‐nitrogen‐cooled surface is assessed. Helium leak detection is demonstrated, and the response and sensitivity of the mass spectrometer as a leak detector are evaluated.
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01.50.Pa Laboratory experiments and apparatus
47.80.-v Instrumentation and measurement methods in fluid dynamics
07.30.Hd Vacuum testing methods; leak detectors

Microfabrication at the University of Cincinnati

A. Naumaan, K. P. Roenker, and J. T. Boyd

J. Vac. Sci. Technol. 17, 69 (1980); http://dx.doi.org/10.1116/1.570507 (3 pages)

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This paper outlines a two quarter laboratory course in integrated circuit design and fabrication offered by the Department of Electrical and Computer Engineering at the University of Cincinnati. Included in this course is an introduction to the operation and use of a wide range of vacuum system technology. The course also covers integrated circuit device design and layout, computerized mask generation, hands‐on processing, and evaluation of the finished IC chips. Traditional instruction is supplemented by video tapes of both lectures and demonstrations of the use of various pieces of equipment. Labortory facilities include high‐vacuum systems containing diffusion, ion and turbomolecular pumps used in several chemical vapor deposition systems, sputtering systems, and in an ion implantation system. The laboratory also features leak detection equipment, diffusion furnaces, photolithographic equipment, and a scanning electron microscope. Senior graduate students are given responsibility for routine maintenance of laboratory equipment including vacuum systems.
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85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
01.40.Di Course design and evaluation
07.30.-t Vacuum apparatus
07.05.Bx Computer systems: hardware, operating systems, computer languages, and utilities

Solid surfaces, surface processes, and solid/gas interactions

A. W. Czanderna

J. Vac. Sci. Technol. 17, 72 (1980); http://dx.doi.org/10.1116/1.570508 (5 pages)

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An overview of the topical coverage of a one‐semester, three‐hour course on solid surfaces, surface processes, and the solid/gas interface is presented. The main topical areas embracing the nature of the surface phase include topography, shape, depth, composition, purity, and structure, and the methods used to elucidate these parameters. The various theoretical and experimental categories for understanding adsorbate–adsorbent interactions are considered with particular attention focused on physical and chemical adsorption, desorption, and thermal desorption. Surface processes include surface diffusion and chemisorption as a precursor to oxidation and catalysis. The general emphasis of the course is on the experimental aspects of studying surfaces and the harmonious blending of backgrounds in physics, chemistry, materials, mathematics, and engineering for applied and fundamental surface science. The course is designed for graduate students and well qualified seniors majoring in science or engineering, or the equivalent, and has been taught several times.
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82.80.-d Chemical analysis and related physical methods of analysis
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
81.65.-b Surface treatments
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics

Study of the initial stages of pack aluminization

J. R. Rairden and M. R. Jackson

J. Vac. Sci. Technol. 17, 77 (1980); http://dx.doi.org/10.1116/1.570509 (4 pages)

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The kinetics of the pack aluminizing of René 80 have been studied with emphasis on the early stages of the process. NH4F activated packs containing 2% Al and 5% Ni–40 Al were evaluated. It was found that for the 2% Al (high activity) pack that a weight gain of ∠5.6 mg/cm2 was reached during the initial 10 min of processing; thereafter, there was essentially no further weight gain. In contrast, the 5% Ni–40 Al (low activity) pack showed a gradual weight gain to ∠3.0 mg/cm2 during the 185 min process. Electron microprobe analyses of the coatings were used to characterize the composition profiles of the coatings formed in the two packs. The outer region of coatings formed in a 2% Al pack are of relatively uniform composition for the elements measured: Ni, Co, Cr, and Al. In contrast, the coatings formed in a 5% Ni–40 pack showed sharp compositional gradients in the outer region.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Microstructure and chemistry of aluminide coating of Ni–Cr and Ni–Co–Cr alloys

M. R. Jackson and J. R. Rairden

J. Vac. Sci. Technol. 17, 81 (1980); http://dx.doi.org/10.1116/1.570510 (4 pages) | Cited 1 time

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Alloys of composition Ni–20Cr, Ni–35Cr, Ni–50Cr, Co–35Cr, Ni–5Co–20Cr, and Ni–20Co–20Cr have been aluminided by pack cementation. Morphology of the coatings varies considerably among the different alloys. The most striking differences are the avoidance of formation of Kirkendall‐type voids in the Ni–Co–Cr alloys, and the degree of continuity of the α‐Cr layer formed. Both features need to be controlled to avoid coating loss by cracking and spallation. From the appropriate phase diagrams, the sequence of morphologies formed by aluminization can be rationalized. The relation of total aluminum deposition to alloy composition results from phase equilibria and phase solubilities, and phase diagrams can be used to rationalize this relation as well.
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81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
81.30.Bx Phase diagrams of metals, alloys, and oxides
81.40.Gh Other heat and thermomechanical treatments

Thermal passivation of AISI 316 stainless steel in controlled vacuum

G. Hulquist and C. Leygraf

J. Vac. Sci. Technol. 17, 85 (1980); http://dx.doi.org/10.1116/1.570511 (4 pages) | Cited 2 times

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By means of vacuum annealing in the range 525–775 K and under well controlled oxidative conditions the chemical composition of protective films of an AISI 316 stainless steel has been modified in order to increase the resistance to crevice corrosion. Independent of surface pretreatment the increase in critical potential for crevice corrosion in a neutral sodium chloride solution after thermal passivation in controlled vacuum is at least 250 mV. Due to selective oxidation of chromium and nickel during such thermal treatments the beneficial effect in corrosion resistance is attributed to a marked chromium film enrichment and a less marked nickel film enrichment. In combination with any chemical surface pretreatment, which aims at reducing the amount of certain nonmetallic inclusions where localized corrosion attacks frequently start, this thermal surface treatment will result in a protective film with extraordinarily high corrosion resistance. The vacuum annealing process presented is suggested to act as the finishing manufacturing step in certain applications where the steel article is not subjected to any further high temperature annealing.
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81.65.-b Surface treatments
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Summary Abstract: Applications of the vacuum microbalance

A. W. Czanderna

J. Vac. Sci. Technol. 17, 90 (1980); http://dx.doi.org/10.1116/1.570512 (2 pages)

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Abstract Unavailable
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06.30.Dr Mass and density
07.30.Hd Vacuum testing methods; leak detectors
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Physical adsorption studies with the vacuum microbalance

E. Robens

J. Vac. Sci. Technol. 17, 92 (1980); http://dx.doi.org/10.1116/1.570513 (6 pages) | Cited 5 times

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The survey deals with the application of gravimetric measuring techniques to the investigation of physical adsorption processes. The principal topics covered in this paper are the definition of the term ’’adsorption’’; the types of surfaces under investigation; the most important measuring procedures, i.e. measuring isotherms, measuring isobars, and evaluating the results; the advantages, limitations, and typical errors involved in gravimetry compared with competing methods; and limitations and development perspectives of gravimetric investigations of physisorption.
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68.43.-h Chemisorption/physisorption: adsorbates on surfaces
06.30.Dr Mass and density
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
81.70.-q Methods of materials testing and analysis

Microgravimetric/infrared studies: a review

M. J. D. Low

J. Vac. Sci. Technol. 17, 98 (1980); http://dx.doi.org/10.1116/1.570514 (6 pages)

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Infrared spectroscopic techniques are widely used to study solid surfaces and the changes occurring upon them. Similarly, microgravimetric methods are widely used for analogous purposes. However, the two techniques are only rarely employed simultaneously with the same sample; common practice is to use one sample for infrared and another sample for gravimetric study. The various factors leading to the lack of easy compatibility of the two techniques are outlined and examples of combined gravimetric/infrared experiments are reviewed.
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82.80.-d Chemical analysis and related physical methods of analysis
78.30.-j Infrared and Raman spectra
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics

Microgravimetric and infrared study of the adsorption of 1‐butene on delta alumina

D. Bianchi, J. L. Gass, G. Pajonk, and S. J. Teichner

J. Vac. Sci. Technol. 17, 104 (1980); http://dx.doi.org/10.1116/1.570446 (4 pages)

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The adsorption of 1‐butene has been studied gravimetrically on delta alumina which has been dehydroxylated at various temperatures, using a RH Cahn Electrobalance. For temperatures of dehydroxylation between 25° and 250°C delta alumina is inactive in the isomerization of 1‐butene. Simultaneously only reversibly adsorbed on OH groups species has been detected by IR analysis, resembling to 1‐butene. For higher temperatures of dehydroxylation the solid is active in isomerization and two new adsorbed species have appeared: one is reversibly adsorbed and the other is irreversibly adsorbed. The former has the structure of 1‐butene whereas the latter has lost all unsaturated character. Poisoning experiments performed with NH3 demonstrate that these two species are adsorbed on Al3+ ions and the second one also on O2− ions. The irreversibly adsorbed species is responsible for the deactivation of the catalyst.
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68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
78.30.-j Infrared and Raman spectra

Oxidation studies with the vacuum microbalance in complex environments

Earl A. Gulbransen

J. Vac. Sci. Technol. 17, 109 (1980); http://dx.doi.org/10.1116/1.570447 (5 pages)

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Vacuum microbalance methods incorporating oxygen consumption and gas‐flow measurements have expanded the usefulness of the simple weight‐change methods. It will be shown that (1) the combined methods can be used to evaluate oxide film formation and oxide volatility, (2) the combined methods permit an evaluation of the transition between chemically controlled and gas‐diffusion‐controlled oxidation, (3) sample size can also be used to evaluate the transition between chemically controlled and gas‐diffusion‐controlled oxidation, (4) gas flow can be used to extend the study of rapid oxidation reactions to rates of oxidation approaching the collision rate of oxygen with the metal surface, and (5) thermochemical analysis of the condensed and volatile oxides was very useful in the analysis of high temperature oxidation processes.
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82.20.Pm Rate constants, reaction cross sections, and activation energies
82.53.-k Femtochemistry
82.60.Hc Chemical equilibria and equilibrium constants
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Summary Abstract: Kinetics for the hydriding of a plutonium‐l w/o gallium alloy powder

J. L. Stakebake

J. Vac. Sci. Technol. 17, 114 (1980); http://dx.doi.org/10.1116/1.570448 (1 page)

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Abstract Unavailable
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82.20.Rp State to state energy transfer
81.05.Bx Metals, semimetals, and alloys
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.60.Nh Thermodynamics of nucleation

Summary Abstract: Interaction of oxygen with Ni thin films: AES, ELS, work function, and gravimetric measurements

C. Benndorf, B. Egert, C. Nöbl, H. Seidel, and F. Thieme

J. Vac. Sci. Technol. 17, 115 (1980); http://dx.doi.org/10.1116/1.570449 (2 pages) | Cited 1 time

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Abstract Unavailable
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81.05.Bx Metals, semimetals, and alloys
68.55.-a Thin film structure and morphology
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
73.30.+y Surface double layers, Schottky barriers, and work functions

Computer‐automated measurement of high‐temperature vapor pressures by the simultaneous Knudsen torsion‐effusion method

H. Bradford Thompson and Jimmie G. Edwards

J. Vac. Sci. Technol. 17, 117 (1980); http://dx.doi.org/10.1116/1.570450 (3 pages) | Cited 1 time

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Data acquisition from high‐temperature vapor‐pressure measurements by the simultaneous mass‐effusion, torsion‐effusion method has been automated by interfaces to a laboratory computer. The apparatus consists of a torsion‐effusion pendulum suspended from a vacuum semimicrobalance. Rate of mass effusion is monitored by an analog interface to a retransmitting potentiometer on the chart recorder of the semicrobalance. Torque is measured by a digital interface to an array of photodetectors which register the torsion‐pendulum position by a reflected‐light method. Output from the balance is handled by one channel of an analog multiplexer and an analog‐to‐digital converter (ADC). The output from the ADC and the output from the torsion pendulum are fed to two channels of a digital multiplexer. With stored information about the torsion pendulum and the effusion cell, the computer calculates real‐time vapor pressures from both simultaneous measurements, and then the apparent molecular weight of the vapor. Early results from study of the vapor pressure over PbIn2S4(s)/Pb2In6S11(s) are presented.
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07.05.Bx Computer systems: hardware, operating systems, computer languages, and utilities
07.20.Ka High-temperature instrumentation; pyrometers
64.70.Hz Solid-vapor transitions
82.60.Cx Enthalpies of combustion, reaction, and formation

Investigations of hydrogen gettering by means of mass spectrometry and microgravimetry

H. D. Röhrig, K. D. Fischmann, and W. Haubold

J. Vac. Sci. Technol. 17, 120 (1980); http://dx.doi.org/10.1116/1.570451 (5 pages) | Cited 1 time

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Experiments were conducted on different bulk getter materials (Ti, Zr, Ce) in order to study their potential in a new gas purification concept for high‐temperature gas‐cooled reactors. Since the removal of hydrogen and tritium represents the main problem, the measurements concentrated on plateau pressures of the metal hydrides, the kinetics of absorption, passivation, and hydrogen isotope effects. The apparatus used for model investigations with H2 and D2 is a UHV device involving two hot metal beds one of which consists of a microbalance system, various total pressure gauges, and a quadrupole mass spectrometer. The absorption rates were found to be linear with pressure, which is consistent with gas kinetic theory. Plateau pressure measurements down to 10−8 mbar confirm extrapolated literature data, while an observed significant isotope effect near ambient temperature may be understood as a specific passivation effect.
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07.30.Bx Degasification, residual gas
07.75.+h Mass spectrometers
06.30.Dr Mass and density
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Helium scattering measurements of the Ag(111) surface phonon dispersion

Steven C. Yerkes and David R. Miller

J. Vac. Sci. Technol. 17, 126 (1980); http://dx.doi.org/10.1116/1.570452 (4 pages) | Cited 1 time

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Energy and intensity measurements have been performed on 23 meV He atoms scattered from 135 K Ag(111) to yield information on the surface dispersion relation. The preliminary results are in qualitative agreement with the linear Rayleigh phonon dispersion curve expected from continuum theory and experiment. The scattering probability falls exponentially with increasing phonon frequency but shows a distinct maximum at an angle dependent on incident beam angle and energy.
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68.35.Ja Surface and interface dynamics and vibrations
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
63.20.D- Phonon states and bands, normal modes, and phonon dispersion

Granular aluminum superconducting bolometer as a molecular beam detector

M. J. Cardillo, G. E. Becker, G. D. Kubiak, V. Narayanamurti, and M. A. Chin

J. Vac. Sci. Technol. 17, 130 (1980); http://dx.doi.org/10.1116/1.570453 (4 pages) | Cited 1 time

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We have tested a granular aluminum superconducting thin film bolometer as a detector of molecular beams. The bolometer is mounted on a liquid He cryostat and designed to operate in a bakeable UHV scattering chamber. The element is shown to be a sensitve detector of the total thermal energy of the molecular beam flux and if operated in tandem with a mass spectrometer allows the average internal energy to be determined.
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85.25.-j Superconducting devices
29.27.-a Beams in particle accelerators
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment

Angle‐resolved and variable impact energy electron vibrational excitation spectroscopy of molecules adsorbed on surfaces

W. Ho, N. J. DiNardo, and E. W. Plummer

J. Vac. Sci. Technol. 17, 134 (1980); http://dx.doi.org/10.1116/1.570454 (7 pages) | Cited 17 times

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Discrete energy losses occur when a beam of low energy electrons (<30 eV) is scattered from surfaces. For a gas–solid interface, inelastic scattering can occur through excitation of molecular vibrations. Chemical identification, molecular structures and bonding sites can be inferred from the energies of the characteristic losses. The angle and impact energy dependence of the mode intensity can give additional information which in many cases further elucidates the bonding. A consistent picture of the vibrational excitation mechanisms is derived which leads to the identification of helpful selection rules. Discussion will center on the simplest chemical adsorbate of H on W(100) and Ni(111). The application of the basic ideas to diatomic and polyatomic adsorbates will be mentioned briefly.
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68.35.Ja Surface and interface dynamics and vibrations
79.20.Kz Other electron-impact emission phenomena
63.20.K- Phonon interactions

Summary Abstract: Vibrational spectra of formate and acetate species on copper (100)

Brett A. Sexton

J. Vac. Sci. Technol. 17, 141 (1980); http://dx.doi.org/10.1116/1.570455 (2 pages) | Cited 1 time

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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
68.90.+g Other topics in structure, and nonelectronic properties of surfaces and interfaces; thin films and low-dimensional structures (restricted to new topics in section 68)
68.03.Fg Evaporation and condensation of liquids
68.35.Ja Surface and interface dynamics and vibrations

Summary Abstract: Kinetics of carbon deposition from Co on Ru(110) and Ni(100)

D. W. Goodman, R. D. Kelley, T. E. Madey, and J. M. White

J. Vac. Sci. Technol. 17, 143 (1980); http://dx.doi.org/10.1116/1.570456 (1 page)

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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.20.Pm Rate constants, reaction cross sections, and activation energies
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Summary Abstract: Spectroscopic studies of molecular oxygen adsorbed on Pt(111)

Galen B. Fisher, Brett A. Sexton, and John L. Gland

J. Vac. Sci. Technol. 17, 144 (1980); http://dx.doi.org/10.1116/1.570457 (1 page) | Cited 12 times

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79.60.Jv Interfaces; heterostructures; nanostructures
68.35.Ja Surface and interface dynamics and vibrations
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Infrared study of the interaction between delta alumina and 1‐butene

D. Bianchi, G. Pajonk, and S. J. Teichner

J. Vac. Sci. Technol. 17, 145 (1980); http://dx.doi.org/10.1116/1.570458 (4 pages) | Cited 1 time

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A new type of IR cell has been recently developed in this laboratory in order to register exclusively the spectrum of the adsorbed reacting phase during the isomerization of 1‐butene, between 25° and 110°C. The spectra of the adsorbed phases were of three kinds : two of them are of an olefinic structure and are exhibited by a phase adsorbed reversibly; the third one is of an nonolefinic type and belongs to the phase irreversibly adsorbed. This species is involved in the deactivation of the catalyst during isomerization of 1‐butene whereas one of the two first ones is intermediate in this reaction.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
78.30.Jw Organic compounds, polymers
64.70.K- Solid-solid transitions

Stability and reactivity of (5×20) and (1×1) Pt(100) surfaces

P. R. Norton, D. K. Creber, and J. A. Davies

J. Vac. Sci. Technol. 17, 149 (1980); http://dx.doi.org/10.1116/1.570459 (5 pages) | Cited 3 times

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Pt(100)–(5×20) adsorbs hydrogen to significant coverages only below T∠260 K. At ∠190 K the coverage is sufficient to produce a LEED pattern with very strong integral order beam but some weak fractional order beams are visible. For the present purposes this pattern is designated (1×1). The most strongly adsorbed hydrogen species do not desorb from the (1×1) surface below ∠380–390 K. The difference in behavior between the (5×20) and (1×1) surfaces is attributed to a ∠30% decrease in the heat of adsorption of hydrogen on the (5×20) compared to the (1×1) surface. At 120 K both surfaces exhibit similar initial sticking coefficients. The absolute coverages of adsorbed D at 195 K were measured by nuclear microanalysis. Argon‐ion‐induced damage increases the temperature at which the (1×1) surface reconstructs such that at doses exceeding 3×1015 Ar+ cm−2 (5 keV), the surface does not reconstruct below 770 K. This appears to be the temperature at which the random step structure, indicated by the LEED data, anneals out. In the presence of adsorbed H, a dose of only 2×1014 Ar+ cm−2 (5 keV) increases the phase (1×1)→(5×20) transition temperature to ≳ 390 K (from ∠350 K for an undamaged surface), so that it is possible to desorb the hydrogen leaving a clean (1×1) surface. A sputtered surface (∠5×1014 Ar+ cm−2; 5 keV) was examined by Rutherford backscattering and less than 2×1014 Pt cm−2 were displaced from their bulk lattice positions.
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81.30.-t Phase diagrams and microstructures developed by solidification and solid-solid phase transformations
64.70.K- Solid-solid transitions
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics

Surface segregation of a NiCu alloy as studied by a computerized atom‐probe FIM

Yee S. Ng, S. B. McLane, and T. T. Tsong

J. Vac. Sci. Technol. 17, 154 (1980); http://dx.doi.org/10.1116/1.570460 (5 pages) | Cited 7 times

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Using the computerized energy compensated time‐of‐flight atoms‐probe (AP‐FIM), we have obtained an absolute composition depth profile of a NiCu alloy with single atomic layer spatial resolution. For bulk composition of 3.1%±0.5% Cu at 650°±20°C, the topmost layers of the (111) and (001) planes are enriched to (17%±2.7%) and (36.6%±7.5%) Cu, respectively. Slight depletion of Cu is observed in the near surface layers. Both an irregular solution model and a regular solution model with surface enthalpy relaxation are found to agree semiquantitatively with our results. A comparison with the results from other surface techniques is also made.
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
61.66.Dk Alloys
79.70.+q Field emission, ionization, evaporation, and desorption

Local field effects in photoabsorption

A. Zangwill and Paul Soven

J. Vac. Sci. Technol. 17, 159 (1980); http://dx.doi.org/10.1116/1.570461 (5 pages) | Cited 2 times

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We present the results of a calculation of the photoabsorption of xenon using a local‐density‐functional self‐consistent‐field formalism for both the ground state of the system and the time‐dependent local fields induced by the external radiation field. The results are in good agreement with experiment, and are cast in such a way as to explicitly show the collective effects important in photoabsorption.
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32.80.-t Photoionization and excitation
31.15.V- Electron correlation calculations for atoms, ions and molecules

Chemisorption of oxygen and aluminum on the GaAs (110) surface from ab initio theory

John J. Barton, Coenraad A. Swarts, William A. Goddard, and T. C. McGill

J. Vac. Sci. Technol. 17, 164 (1980); http://dx.doi.org/10.1116/1.570462 (5 pages) | Cited 4 times

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We have applied quantum chemical methods to the structure of the clean GaAs (110) surface and the chemisorption of oxygen and aluminum. We find that results for small clusters give geometries for the clean surface in agreement with those observed experimentally. We propose that an intermediate stage of oxidation would exist in which the O atom binds to a surface As. Our studies indicate that the initial site for Al chemisorbed on GaAs (110) has the Al bonded to the surface Ga. Geometries and chemical shifts are reported for both O and Al on GaAs (110). The chemical shifts are in agreement with recent experimental results.
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73.20.-r Electron states at surfaces and interfaces
73.40.-c Electronic transport in interface structures
73.30.+y Surface double layers, Schottky barriers, and work functions

Bonding, shake‐up energies and shake‐up intensities in Cr(NO)4

G. Loubriel

J. Vac. Sci. Technol. 17, 169 (1980); http://dx.doi.org/10.1116/1.570463 (3 pages) | Cited 1 time

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We report the results of SCF‐xα‐multiple scattering calculations of the electronic structure of Cr(NO)4 in its neutral ground state and in several positive‐ion states. This allows a description of the bonding of NO to the Cr atom, explains how the screening of core holes (created in a XPS measurement) is effected and yields the N1S shake‐up spectrum. There is good agreement with the experimental valence region photoemission spectra peak positions and with the shake‐up peak positions and intensities.
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33.90.+h Other topics in molecular properties and interactions with photons (restricted to new topics in section 33)
31.15.xw Valence bond calculations

Auger lineshape analysis of molecules and solids

Dwight R. Jennison

J. Vac. Sci. Technol. 17, 172 (1980); http://dx.doi.org/10.1116/1.570423 (4 pages) | Cited 10 times

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Considerable recent theoretical work has shown that core–valence–valence Auger lineshape analysis may often be successfully made in terms of the molecular orbital structure of the molecule or the band structure of the solid. This approach assumes a priori that the final state hole motion is uncorrelated. Limitations to this approach include the highly correlated final states observed in ionic and narrow band solids (as Cu). Complications to this approach include the initial state valence screening of the core hole which affects the Auger decay probabilities. However, much useful information about the local density of states (local chemical environment) may be extracted in covalent and metallic materials. Examples from molecular (CH4, C2H4, C2H6, and C3H8) and solid state (Cu and Be) spectra are presented and the state of our understanding of lineshape analysis is summarized.
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79.20.Fv Electron impact: Auger emission
31.15.xw Valence bond calculations
33.70.Jg Line and band widths, shapes, and shifts
71.20.-b Electron density of states and band structure of crystalline solids

Aims and recent accomplishments of surface theory

Peter J. Feibelman

J. Vac. Sci. Technol. 17, 176 (1980); http://dx.doi.org/10.1116/1.570424 (6 pages)

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The goals of surface science include the understanding of surface bonding, structure, transport, and chemistry. However, our present activities are mainly focused on the most basic problem, viz., what are the constituents of a given surface, where are they located and how are they bonded? Theorists are approaching this surface characterization problem from two sides. To make better use of the data available from the many experimental surface probes, we are developing an understanding of the force laws which govern the motion of probe particles near surfaces, and we are studying intensively the relation between the excitation and ground state spectra of a solid. In order to develop a predictive capability regarding surface structure, we are studying a variety of intrinsic surface properties including the nature of bonds at transition metal surfaces, the meaning of bond locality in extended systems, and generally the electronic factors underlying the forces which govern surface geometry. These studies often raise technical issues such as the validity of using local exchange correlation potentials and the applicability of cluster calculations to the analysis of extended surface situations, which, however, should not obscure the main thrust of current work — empirical and predictive surface structure determination. These points will be illustrated with examples from recent research and ways in which experimental surface work might assist theoretical efforts will be indicated.
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
73.20.-r Electron states at surfaces and interfaces
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
01.30.Bb Publications of lectures (advanced institutes, summer schools, etc.)

Piezoelectric quartz crystal microbalance (PQCMB) for sorption studies under dynamic conditions

V. Mecea and R. V. Bucur

J. Vac. Sci. Technol. 17, 182 (1980); http://dx.doi.org/10.1116/1.570425 (4 pages) | Cited 3 times

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Construction of the measuring cell and of the auxiliary electric and electronic equipments of a PQCMB is described. The cell is designed for equilibrium and kinetic studies on the thin solid (metallic) layer/gas interface with inert carrier gas (dynamic conditions). Special attention is given to the temperature constancy: the auxiliary equipment of PQCMB is thermostated to within ±0.5°C, the cell to within ±0.005°C. Under these conditions a short‐term stability of the frequency better than ±0.01 Hz is obtained, at a nominal frequency of 5.023 MHz, i.e., better than ±2 ppb; the weighing limit is about 5×10−11 g. The long‐term stability attained under the same conditions is about ±0.02 Hz. The conditions for using the PQCMB in UHV‐surface studies within 80 and 400 K are briefly discussed.
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06.30.Dr Mass and density
07.50.-e Electrical and electronic instruments and components
68.08.-p Liquid-solid interfaces
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
07.20.-n Thermal instruments and apparatus

Summary Abstract: On the accuracy of low‐energy electron diffraction

W. N. Unertl

J. Vac. Sci. Technol. 17, 186 (1980); http://dx.doi.org/10.1116/1.570426 (2 pages) | Cited 1 time

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Abstract Unavailable
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61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
34.80.-i Electron and positron scattering

Summary Abstract: Chemisorption of water on Rh(111)

J. J. Zinck and W. H. Weinberg

J. Vac. Sci. Technol. 17, 188 (1980); http://dx.doi.org/10.1116/1.570427 (2 pages) | Cited 15 times

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68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Structure of the clean Re(101̄0) surface

H. L. Davis and D. M. Zehner

J. Vac. Sci. Technol. 17, 190 (1980); http://dx.doi.org/10.1116/1.570428 (4 pages) | Cited 12 times

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Existing LEED data from the clean Re(101̄0) surface have been analyzed by comparing with the results of fully dynamical calculations for numerous models. The analysis indicates that this surface has the second layer atoms located directly below the centers of the geometric rectangles of the first layer. This geometry is one of the two possible terminations of the truncated bulk crystal. Further, the analysis indicates that the interlayer spacing between the 1st and 2nd atomic layers is contracted by about 17% from its bulk value, while the spacing beteeen the 2nd and 3rd layers may be slightly expanded. Since the data employed in the analysis consisted of only two diffracted beams, the above conclusions should be considered as tentative and accepted with reasonable caution. However, this is the first reported LEED analysis for the (101̄0) surface of an hcp metal. So it is of interest to determine whether our conclusions will be verified for Re and/or similar results found for other hcp metals.
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61.66.Bi Elemental solids
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)

1979 LEED analysis of Cu(100)

J. R. Noonan and H. L. Davis

J. Vac. Sci. Technol. 17, 194 (1980); http://dx.doi.org/10.1116/1.570429 (4 pages) | Cited 7 times

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The crystallography of the Cu(100) surface is reexamined by a LEED I–V profile analysis in order to investigate the effects of applying current experimental and computational techniques. The study produces a very small multi‐beam reliability factor of 0.068, and it is concluded that the first interlayer spacing of Cu(100) is within 2% of the bulk value. The work also demonstrates that agreement between calculational and experimental I–V profiles can be significantly improved by the simple process of data averaging the experimental profiles which should be symmetrically equivalent.
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61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
61.66.Bi Elemental solids

Changes induced on the surfaces of small Pd clusters by the thermal desorption of CO

D. L. Doering, H. Poppa, and J. T. Dickinson

J. Vac. Sci. Technol. 17, 198 (1980); http://dx.doi.org/10.1116/1.570430 (3 pages) | Cited 1 time

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The stability and adsorption/desorption properties of supported Pd crystallites less than 5 nm in size were studied by Auger electron spectroscopy and repeated flash thermal desorption of CO. The Pd particles were grown epitaxially on heat‐treated, UHV‐cleaved mica at a substrate temperature of 300°C and a Pd impingement flux of 4×1013 atoms/cm2 s. Auger analysis allowed in situ measurement of relative particle disperion and contamination, while FTD monitored the CO desorption properties. The results show that significant changes in the adsorption properties can easily be detected. Changes in the Pd Auger signal and the desorption spectrum during the first few thermal cycles are believed to be due to particle coalescence and facetting. The rate of this change is dependent on the temperature and duration of the desorption. Significant reductions in the amplitude of the desorptions peak occur during successive CO desorptions are attributed to increases of surface carbon, induced by the desorption of CO (an effect not observed on large single crystals). The contamination process could be reversed by heat treatment in oxygen or hydrogen.
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68.43.-h Chemisorption/physisorption: adsorbates on surfaces
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
81.40.Gh Other heat and thermomechanical treatments

Summary Abstract: Effect of ion and electron bombardment on the Auger electron surface spectra of Wustite, Magnitite, and Hematite powders

D. Buczek and S. Sastri

J. Vac. Sci. Technol. 17, 201 (1980); http://dx.doi.org/10.1116/1.570432 (2 pages) | Cited 3 times

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The effects of ion and electron bombardment on the auger electron surface spectra of wustite, magnetite and hematite powders are reported.
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79.20.Fv Electron impact: Auger emission
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)

Atom‐probe field‐ion microscopy of a high intensity gallium ion source

Robert J. Culbertson, G. H. Robertson, Y. Kuk, and T. Sakurai

J. Vac. Sci. Technol. 17, 203 (1980); http://dx.doi.org/10.1116/1.570433 (4 pages) | Cited 15 times

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The emission characteristics of a liquid‐metal ion source have been investigated with a magnetic‐sector atom‐probe field‐ion microscope. The emission is classified into low, intermediate, and high intensity emission regimes. In the high intensity emission regime the emission is approximately 99% Ga+, but Ga++ and molecular gallium ions are also present. The relative intensities of Ga+, Ga++, Ga2+, and Ga3+ were measured as a function of total current in the high intensity emission regime. Energy distributions of these four species were also measured at various total currents. Spectral analysis of the optical emission from the ion source indicate that the light is due to radiation from neutral atomic gallium. It is concluded that a considerable amount of gas phase neutral gallium is in the vicinity of the emitter. Also, the ionization of atomic gallium takes place at the emitter surface, while the molecular ions are formed far from the surface.
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68.37.Vj Field emission and field-ion microscopy
29.25.Lg Ion sources: polarized
29.25.Ni Ion sources: positive and negative
61.25.Mv Liquid metals and alloys
41.75.Ak Positive-ion beams
41.75.Cn Negative-ion beams

Summary Abstract: Quantitative analysis of step densities using a two‐dimenional random probability model

T. ‐M. Lu, S. R. Anderson, M. G. Lagally, and G.‐C. Wang

J. Vac. Sci. Technol. 17, 207 (1980); http://dx.doi.org/10.1116/1.570434 (2 pages) | Cited 4 times

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61.72.-y Defects and impurities in crystals; microstructure
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)

Summary Abstract: Investigation of the metal‐support interaction in coprecipitated nickel on alumina methanation catalysts using x‐ray photoelectron spectroscopy

R. B. Shalvoy, P. J. Reucroft, and B. H. Davis

J. Vac. Sci. Technol. 17, 209 (1980); http://dx.doi.org/10.1116/1.570435 (2 pages)

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The use of x‐ray photoelectron spectroscopy in the study of metal‐support interaction in nickel on alumina methanation catalysts is reported. Although these interactions give thermal stability, they also make the catalysts more difficult to reduce. (AIP)
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82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
79.60.Jv Interfaces; heterostructures; nanostructures
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Soft x‐ray appearance potential spectroscopy study of pure rare‐earth metals with a sealed‐off analyzer tube

Z. Y. Hua, J. Zhuge, C. S. Fan, H. X. Chen, X. L. Pan, and J. L. Huang

J. Vac. Sci. Technol. 17, 211 (1980); http://dx.doi.org/10.1116/1.570436 (3 pages)

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A comparative study of the soft x‐ray appearance potential spectra of various pure rare‐earth metals has been carried out with a specially designed sealed‐off analyzer tube. It is shown that for lanthanide elements with even number of 4f‐electrons (except Eu) no spectrum is found in a region of accelerating potential from 50 to 1400 V. The most sensitive peaks are M5 (3d5/2) and M4 (3d3/2), which can serve as ’’finger prints’’ to identify the rare‐earth metals. The ratio of the M5/M4 peak heights might be classified into three groups, according to their various values. Satellite peaks also exist, although no satisfactory explanation has yet been given. The purity of most samples is checked by a Mattauch–Herzog type mass spectrometer or by the proton‐induced x‐ray emission (PIXE).
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78.70.En X-ray emission spectra and fluorescence
82.80.Dx Analytical methods involving electronic spectroscopy
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
61.05.C- X-ray diffraction and scattering

Summary Abstract: Quantitative determination of the surface composition of sulfur‐bearing anion mixtures by Auger electron spectroscopy

N. H. Turner, J. S. Murday, and D. E. Ramaker

J. Vac. Sci. Technol. 17, 214 (1980); http://dx.doi.org/10.1116/1.570437 (2 pages) | Cited 1 time

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82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
79.20.Fv Electron impact: Auger emission
79.60.Jv Interfaces; heterostructures; nanostructures

Enhanced photoexcitation from the surface of aluminum

Harry J. Levinson, E. W. Plummer, and P. Feibelman

J. Vac. Sci. Technol. 17, 216 (1980); http://dx.doi.org/10.1116/1.570438 (3 pages) | Cited 5 times

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The enhancement of photoionization cross sections due to the spacially varying photon field at the surface of a metal has been observed by measuring the cross section for the surface state and Fermi level on Al(001) for photon energies between 9 and 23 eV. The data are in excellent agreement with the results of a self‐consistent jellium calculation which takes into account the induced short wavelength longitudinal fields at the surface of the metal. These fields are much more effective than the transverse fields in providing the momentum necessary for photoexcitation and this mechanism dominates all others, including direct vertical transitions, in the energy range considered. The implications of this effect on photoemission studies of surface and bulk properties will be discussed.
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79.60.Bm Clean metal, semiconductor, and insulator surfaces
73.20.-r Electron states at surfaces and interfaces

Summary Abstract: Lifetime broadening in electron spectroscopy of core levels in solids

J. C. Fuggle and S. Alvarado

J. Vac. Sci. Technol. 17, 219 (1980); http://dx.doi.org/10.1116/1.570439 (1 page) | Cited 1 time

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79.60.-i Photoemission and photoelectron spectra
32.70.-n Intensities and shapes of atomic spectral lines

Summary Abstract: New evidence for dimer reconstruction on Ge(100) and Si(100)

J. E. Rowe and S. B. Christman

J. Vac. Sci. Technol. 17, 220 (1980); http://dx.doi.org/10.1116/1.570440 (2 pages) | Cited 1 time

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73.20.-r Electron states at surfaces and interfaces
81.65.-b Surface treatments

Summary Abstract: Photoelectron spectra of metal molecular clusters

Charles F. Brucker and Thor N. Rhodin

J. Vac. Sci. Technol. 17, 221 (1980); http://dx.doi.org/10.1116/1.570441 (2 pages)

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36.40.-c Atomic and molecular clusters
33.60.+q Photoelectron spectra
82.30.Vy Homogeneous catalysis in solution, polymers and zeolites
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Surface defects and thermodynamics of chemisorbed layers

M. G. Lagally, T. ‐M. Lu, and D. G. Welkie

J. Vac. Sci. Technol. 17, 223 (1980); http://dx.doi.org/10.1116/1.570442 (8 pages) | Cited 4 times

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Chemisorbed overlayers on single crystal surfaces can in many cases be considered as lattice gases. The general features of temperature–coverage phase diagrams resulting from attractive or repulsive adatom interactions in such systems are discussed in analogy with binary solid solutions. The effect of surface and overlayer defects on the determination of phase boundaries is considered. The use of low‐energy electron diffraction (LEED) to study surface defects and overlayer phase diagrams is briefly summarized.
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68.08.-p Liquid-solid interfaces
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
64.70.-p Specific phase transitions
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)

Summary Abstract: O/Ni(111): Adlayer phases and binding sites

L. D. Roelofs, T. L. Einstein, P. E. Hunter, A. R. Kortan, Robert L. Park, and R. M. Roberts

J. Vac. Sci. Technol. 17, 231 (1980); http://dx.doi.org/10.1116/1.570443 (2 pages) | Cited 2 times

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Abstract Unavailable
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
64.60.-i General studies of phase transitions
73.90.+f Other topics in electronic structure and electrical properties of surfaces, interfaces, thin films, and low-dimensional structures (Restricted to new topics in section 73)

Photoemission method for the study of surface kinetics: CO on Mo(100)

S. Semancik and P. J. Estrup

J. Vac. Sci. Technol. 17, 233 (1980); http://dx.doi.org/10.1116/1.570444 (6 pages) | Cited 3 times

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Using a photoelectron spectrometer, a technique has been developed to continuously monitor changes that may occur in an adlayer when heated. After identifying adsorbate‐induced features in UV photoemission (UPS) spectra from a chemisorption system, the intensities of individual features are recorded as a function of temperature and/or time. Kinetic parameters can be extracted from the rates of these intensity changes. The thermally activated decomposition of CO on Mo(100) has been used to demonstrate the technique here. Preliminary results show that this process does not obey simple first‐order kinetics. Analysis of isothermal data gives a coverage‐dependent dissociation activation energy with Edis?0.60 eV for 0?0.5, and a frequency factor near 1013 s−1.
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82.20.Pm Rate constants, reaction cross sections, and activation energies
79.60.-i Photoemission and photoelectron spectra
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Summary Abstract: Temperature‐dependent ordering processes in the adsorption system CO/Ru(001)

F. M. Hoffman, A. Ortega, H. Pfnür, D. Menzel, and A. M. Bradshaw

J. Vac. Sci. Technol. 17, 239 (1980); http://dx.doi.org/10.1116/1.570445 (2 pages)

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68.43.-h Chemisorption/physisorption: adsorbates on surfaces
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
78.30.-j Infrared and Raman spectra
61.85.+p Channeling phenomena (blocking, energy loss, etc.)

Surface diffusion of adsorbed species: A review

David A. King

J. Vac. Sci. Technol. 17, 241 (1980); http://dx.doi.org/10.1116/1.570400 (7 pages) | Cited 19 times

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Advances made in the study of the diffusion of adsorbed species on single crystal surfaces are summarized. An appraisal of the techniques and methods of data treatment which have been developed for both macroscopic (single crystals cut to expose a given crystal plane) and microscopic (field emitter) surfaces is presented, and a brief survey is made of the data obtained for precursor, molecularly chemisorbed, and dissociatively chemisorbed states. The influence of lateral interactions between adatoms on diffusion parameters is explicitly examined in relation to recent results for O adatoms on W{110}. Finally, a brief survey is given of the importance of diffusion in other surfaces processes, such as the formation of ordered overlayers and adsorption and desorption kinetics.
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68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
66.30.-h Diffusion in solids
68.55.-a Thin film structure and morphology
68.37.Vj Field emission and field-ion microscopy

Direct (TEM) observation of the catalytic oxidation of amorphous carbon by Pd particles

R. D. Moorhead, H. Poppa, and K. Heinemann

J. Vac. Sci. Technol. 17, 248 (1980); http://dx.doi.org/10.1116/1.570401 (3 pages) | Cited 3 times

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The catalytic oxidation of amorphous carbon substrates by Pd particles is observed by in situ transmission electron microscopy. Various modes of selective attack of the carbon substrate in the immediate neighborhood of Pd particles are observed, which can be correlated with different degrees of particle mobility. Using amorphous substrates we have been able to demonstrate that the particle‐substrate interaction is influenced by the structure of the particle. This has not previously been noted.
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82.30.Vy Homogeneous catalysis in solution, polymers and zeolites
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Summary Abstract: Screening effects and plasmon gains in the KLL and KLV Auger spectra of Na, Mg, Al, and Si

J. C. Fuggle and R. Lässer

J. Vac. Sci. Technol. 17, 251 (1980); http://dx.doi.org/10.1116/1.570402 (2 pages)

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79.20.Fv Electron impact: Auger emission
32.80.Hd Auger effect (including Coster-Krönig transitions)

Positronium emission from metal surfaces

I. J. Rosenberg, A. H. Weiss, and K. F. Canter

J. Vac. Sci. Technol. 17, 253 (1980); http://dx.doi.org/10.1116/1.570403 (3 pages) | Cited 5 times

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Positronium (Ps, a positron–electron bound pair) emission as a result of slow positron (30–1000 eV) bombardment of Cu, Al, Ni, and Ag surfaces has been investigated as a function of incident positron energy, sample temperature, and surface contamination. The fraction of 30 eV positrons that were reemited as Ps at 380 K with <5% surface contamination ranged from 0.43 to 0.47. The emission fraction is found to increase with both increasing surface contamination and incident positron energy. Both thermally activated and nonthermally activated Ps emission is suggested by the data. A one‐step thermal activation model applied to the data yields activation energies of 0.44±0.04, 0.46±0.04 and 0.75±0.05 eV for Al(100), Ag(polycrystalline), and Ni(100), respectively.
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36.10.Dr Positronium
25.30.-c Lepton-induced reactions
68.90.+g Other topics in structure, and nonelectronic properties of surfaces and interfaces; thin films and low-dimensional structures (restricted to new topics in section 68)

Summary Abstract: Hydrogen adsorption on Si(100) surface studied by MeV ion scattering

T. Narusawa and W. M. Gibson

J. Vac. Sci. Technol. 17, 256 (1980); http://dx.doi.org/10.1116/1.570404 (1 page)

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Abstract Unavailable
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68.43.-h Chemisorption/physisorption: adsorbates on surfaces
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
61.85.+p Channeling phenomena (blocking, energy loss, etc.)

Summary Abstract: Review of the present status of the Alcator C Tokamak

Alcator Group

J. Vac. Sci. Technol. 17, 258 (1980); http://dx.doi.org/10.1116/1.570405 (2 pages)

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Abstract Unavailable
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52.55.Fa Tokamaks, spherical tokamaks
52.55.Hc Stellarators, torsatrons, heliacs, bumpy tori, and other toroidal confinement devices
52.50.Gj Plasma heating by particle beams
52.55.Pi Fusion products effects (e.g., alpha-particles, etc.), fast particle effects
28.52.-s Fusion reactors

Review of the ISX‐B experimental program

M. J. Saltmarsh

J. Vac. Sci. Technol. 17, 260 (1980); http://dx.doi.org/10.1116/1.570407 (8 pages) | Cited 2 times

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The ISX‐B tokamak is a modestly sized device that is designed to explore questions closely related to the design of future tokamak devices, such as the Engineering Test Facility (ETF). The major program emphasis is on high‐β plasma operation using neutral beams to heat plasmas with noncircular cross sections. In addition, substantial efforts are under way or planned in the areas of plasma‐wall interactions, coated limiter studies, electron–cyclotron heating, ripple injection, impurity flow reversal, pellet injection, and the application of a bundle divertor. The current status and future plans for these programs are reviewed.
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28.52.-s Fusion reactors
52.55.Fa Tokamaks, spherical tokamaks
52.55.Hc Stellarators, torsatrons, heliacs, bumpy tori, and other toroidal confinement devices
52.50.Gj Plasma heating by particle beams
52.70.-m Plasma diagnostic techniques and instrumentation

Summary Abstract: Inside look at PDX

D. K. Owens

J. Vac. Sci. Technol. 17, 268 (1980); http://dx.doi.org/10.1116/1.570408 (2 pages)

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Abstract Unavailable
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52.55.Fa Tokamaks, spherical tokamaks
52.55.Hc Stellarators, torsatrons, heliacs, bumpy tori, and other toroidal confinement devices
52.50.Gj Plasma heating by particle beams
52.70.-m Plasma diagnostic techniques and instrumentation
28.52.-s Fusion reactors

Design and operational characteristics of the cryopump high‐vacuum system for the 25 000‐l target chamber of the Helios Laser Facility

N. G. Wilson and Keith N. Watts

J. Vac. Sci. Technol. 17, 270 (1980); http://dx.doi.org/10.1116/1.570409 (4 pages)

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A vacuum system utilizing two 25 000 l/s (H2O) two‐stage (20 and 70 K) helium refrigerator (cold gas) cryopumps and a 1500 l/s turbomolecular pump has been provided for a 25 000‐l‐volume stainless steel chamber as a part of the Helios Laser Facility. Design goals for the performance of the vacuum system are to produce a chamber pressure of less than 1.33×10−4 Pa after two hours pumping from atmospheric pressure. Details of the vacuum system configuration, and typical operating conditions are described. Observations made during operation indicate the cryopumps utilized initially produce expected pumping performance followed by variable performance (pumping speed and ultimate pressure) depending upon pumping history. The turbomolecular pump utilized has demonstrated reproducible pump speed and ultimate pressure. Both pumps produce some vibration which can cause interference with critical components in the target chamber; vibration damping/attenuation has been successfully employed for the turbomolecular pump with similar techniques being studied for use with the cryopumps. Reliability of the machines utilized has been excellent with only routine maintenance required in the first year of operation. Considerable instability in ionization gauges (Bayard–Alpert type) has been experienced where the expected gauge sensitivity of 10 per Torr has been observed to vary from 7.5 to ≳11.
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07.30.Cy Vacuum pumps
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials
07.30.-t Vacuum apparatus

Characteristics of a bakeable ion‐cryopumped UHV system

M. Michaud and L. Sanche

J. Vac. Sci. Technol. 17, 274 (1980); http://dx.doi.org/10.1116/1.570410 (3 pages) | Cited 12 times

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This paper describes an UHV system for studying condensed films or free metal surfaces at temperature near 14 K. The system consists of a commercial cryopump, and 80 1/s ion pump, a sorption pump and a 30 l chamber having one square meter of internal surface. The standard nonbakeable components in the cryopump have been modified at the factory. The charcoal is now held in contact with 14 K cryopanel by means of small copper rods and a brass screen; all connections are made by Conflat flanges; and the indium gaskets have been replaced by silver ones. With the exception of the charcoal and the electrical feedthroughs, the system is entirely metallic. A base pressure in the 10−11 Torr range can be reached after a 24 h bakeout period at 250°C. During this period, only the ion pump is operative. Between experiments, the cryopump can be periodically turned off and regenerated by pumping the desorbing gases with the ion pump. The base pressure can be restored 4 h after restarting the cryopump.
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07.30.Cy Vacuum pumps
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment

Summary Abstract: Cryopump for a vacuum microbalance

E. Robens

J. Vac. Sci. Technol. 17, 277 (1980); http://dx.doi.org/10.1116/1.570411 (2 pages)

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Abstract Unavailable
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07.30.Cy Vacuum pumps
06.30.Dr Mass and density
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment

Methane outgassing from a Ti sublimation pump

D. Edwards

J. Vac. Sci. Technol. 17, 279 (1980); http://dx.doi.org/10.1116/1.570412 (3 pages) | Cited 2 times

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A Ti sublimation pump together with a small 20 l/s ion pump is typically used as the pump for UHV systems. It is well known that the Ti surface will not pump methane and that the ion pump pumping speed for CH4 is only 1 l/s in the low 10−11 Torr range. Thus it is important to identify and if possible reduce the sources of CH4 outgassing. In this study we report the first quantitative measurements of the methane outgassing rate from a 1500 cm2 Ti sublimation chamber both before and after the Ti evaporation. The contrast to the very low CH4 outgassing rate from the chamber before the Ti is flashed (<10−12 Torr l/s) the CH4 outgassing rate after the Ti evaporation is considerable (4×10−11 Torr l/s) with a very slow decrease with repect to time, and has been found to be significant in terms of the ISABELLE requirements. To essentially eliminate the methane outgassing from the Ti getter chamber, it has been determined sufficient to heat the Ti chamber for four hours at 100 C after the Ti evaporation has been completed. Using a similar procedure a reasonably rapid processing of the ISABELLE vacuum system to an ultrahigh vacuum condition should be possible after an atmospheric exposure.
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07.30.Bx Degasification, residual gas
29.20.db Storage rings and colliders
64.70.Hz Solid-vapor transitions

Low‐energy ion erosion studies of machine faceted stainless steel

J. K. G. Panitz and D. J. Sharp

J. Vac. Sci. Technol. 17, 282 (1980); http://dx.doi.org/10.1116/1.570413 (4 pages) | Cited 1 time

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Type 304 annealed stainless‐steel substrates with a variety of machine faceted surface finishes have been eroded by low‐energy (250–1000 eV) hydrogen, and argon ion beams. The dimensions of the machine faceted features studied range from that of the annealed crystalline grain size (approximately 0.0125 cm) to 0.25‐cm macrostructures. Relative erosion rates have been measured and analyzed as a separable function of angular dependent sputtered particle emission and particle recapture. It was found that the formation of a faceted topography on the surface of components exposed to low‐energy, light‐ion erosion can significantly reduce the effective ion erosion yield.
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81.05.Bx Metals, semimetals, and alloys
41.75.Ak Positive-ion beams
41.75.Cn Negative-ion beams
52.55.Fa Tokamaks, spherical tokamaks
52.55.Hc Stellarators, torsatrons, heliacs, bumpy tori, and other toroidal confinement devices

Glow discharge conditioning of the PDX vacuum vessel

H. F. Dylla, S. A. Cohen, S. M. Rossnagel, G. M. McCracken, and Ph. Staib

J. Vac. Sci. Technol. 17, 286 (1980); http://dx.doi.org/10.1116/1.570414 (5 pages) | Cited 5 times

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A glow discharge technique has been developed and applied to the conditioning of the large (38 m3) Poloidal Divertor Experiment (PDX) vacuum vessel. The discharge parameters and working gas (H2) were chosen to maximize C and O removal and minimize metal sputtering. The glow discharge was produced by biasing one or two internal anodes at 400 V to sustain a discharge current of 2–4 A per anode. Purified H2 at a pressure of 3×10−2 Torr was flowed through PDX at ∠10 Torr l/s. The effectiveness of the glow discharge conditioning was monitored by measuring impurity gas (CH4, C2H4, and CO) exhaust rates by mass spectrometry and C and O surface removal rates by in situ AES and XPS. Initial glow discharge operation was accompanied by frequent arcing which subsequently decreased with time. Low Zeff (?2) high‐power discharges were obtained in PDX after 120 h of glow discharge treatment, during which more than 100 equivalent monolayers of C and O were removed from the vessel.
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07.30.Hd Vacuum testing methods; leak detectors
52.80.Hc Glow; corona
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

X‐ray photoelectron spectroscopy (XPS) studies of oxygen and carbon bonding to tokamak walls

Ph. Staib, H. F. Dylla, and S. M. Rossnagel

J. Vac. Sci. Technol. 17, 291 (1980); http://dx.doi.org/10.1116/1.570415 (3 pages) | Cited 1 time

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The binding energies of surface atoms of stainless steel samples exposed to hydrogen plasma discharges in PDX are measured using x‐ray photoelectron spectroscopy. After glow discharge conditioning the O1s line is completely shifted to a higher binding energy which is an indication of the formation of hydroxides. The Fe2p lines show a partial reduction of iron. After high power discharges, the oxygen concentration increases and the binding energy of the deposited O atoms corresponds to a metallic oxide. The deposited limiter material Ti is also completely oxidized. For both kinds of discharges the binding energies of Cr2p and C1s remain essentially unmodified.
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81.05.Bx Metals, semimetals, and alloys
79.60.-i Photoemission and photoelectron spectra
68.08.-p Liquid-solid interfaces
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
52.70.-m Plasma diagnostic techniques and instrumentation

Transient getter scheme for the Tokamak Fusion Test Reactor

J. L. Cecchi, S. A. Cohen, and J. J. Sredniawski

J. Vac. Sci. Technol. 17, 294 (1980); http://dx.doi.org/10.1116/1.570416 (4 pages)

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The ability of the Tokamak Fusion Test Reactor (TFTR) to attain the largest fusion power gain depends critically on minimizing plasma contamination and controlling the densities of the reacting deuterium and tritium. Experiments on a number of tokamaks have demonstrated that gettering over an appreciable surface area (? 10%) of the vacuum vessel greatly facilitates both of these objectives. One particular problem in implementing a surface pumping system in TFTR, however, is a restriction on the maximum allowable tritium content of the getter. This restriction could require regeneration of the absorbed tritium after as few as 50 machine pulses. We have developed a scheme utilizing SAES Zr/Al getter modules which obviates the need for such frequent interruptions of machine operation by taking advantage of the pulsed operation of TFTR. With the Zr/Al getter at temperatures between 500°–600°C it is possible to achieve a quasisteady state in the tritium loading where the quantity of tritium desorbed between pulses is equal to the quantity which is absorbed during a pulse. Since frequent thermal cycling is not required, this scheme also reduces the possibility of Zr/Al getter material fatigue.
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28.52.-s Fusion reactors
07.30.Bx Degasification, residual gas
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Thermal responses of first wall limiters in the Tokamak Fusion Test Reactor

Robert Budny

J. Vac. Sci. Technol. 17, 298 (1980); http://dx.doi.org/10.1116/1.570417 (3 pages) | Cited 1 time

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A model was used for the heat flux to estimate the thermal responses and the sublimation rates of several first wall limiters proposed for the Tokamak Fusion Test Reactor. The critical parameter is the thickness of the scrape‐off layer, or outer skin of the plasma. The thinner this is, the hotter the limiter will become after repeated discharges. The minimum tolerable thickness is about 0.5 cm for copper or graphite tiles over Nitronic 33 steel backing plates. For thicknesses less than this the steel will be too hot; the sublimation rates of most of the proposed first wall coatings for the tiles are sufficiently low to not contaminate the plasma.
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52.40.Hf Plasma-material interactions; boundary layer effects
52.55.Fa Tokamaks, spherical tokamaks
52.55.Hc Stellarators, torsatrons, heliacs, bumpy tori, and other toroidal confinement devices
52.55.Pi Fusion products effects (e.g., alpha-particles, etc.), fast particle effects

Summary Abstract: In situ surface analysis station for the PDX tokamak

S. M. Rossnagel, S. A. Cohen, H. F. Dylla, and Ph. Staib

J. Vac. Sci. Technol. 17, 301 (1980); http://dx.doi.org/10.1116/1.570419 (2 pages)

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Abstract Unavailable
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52.70.Nc Particle measurements
28.50.Ma Auxiliary generators
52.40.Hf Plasma-material interactions; boundary layer effects

UHV compatible chopper system

Donald E. Voss and Samuel A. Cohen

J. Vac. Sci. Technol. 17, 303 (1980); http://dx.doi.org/10.1116/1.570420 (3 pages) | Cited 2 times

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A time‐of‐flight system utilizing a novel mechanical chopper has been developed to measure the energy spectrum of neutral deuterium atoms emitted from a tokamak plasma. The chopper system consists of a motor, a magnetically levitated shaft, and a chopper disk. The disk is rigidly attached to a 159 g shaft assembly and the set is supported against gravity in vacuum by permanent magnets and a stabilizing servosystem (patented by Cambridge Thermionic Corp., Cambridge, MA). All components are UHV compatible to avoid contamination to the tokamak and to the electron multiplier detector. The 25.4‐cm‐o.d., 0.005‐cm‐thick, 20 g, 301 stainless‐steel chopper disk has 24 0.025‐cm‐wide slots photoetched at an 11.4‐cm radius. An effective aperture time of 0.55 μs is achieved during typical steady‐state operation at 22500 rpm with a vacuum pressure of 2×10−8 Torr.
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52.70.Nc Particle measurements
06.30.Ft Time and frequency
07.07.Tw Servo and control equipment; robots

Thermal desorption measurements of hydrogen–isotope retention in the Alcator‐A tokamak

A. M. Razdow, E. S. Marmar, S. A. Cohen, and H. F. Dylla

J. Vac. Sci. Technol. 17, 306 (1980); http://dx.doi.org/10.1116/1.570421 (4 pages) | Cited 1 time

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Results are presented for deuterium retention measurements in type 304 stainless steel exposed in the edge plasma of the Alcator‐A tokamak. Stainless steel samples, at 300 K, with surface conditions characterized by Auger electron spectroscopy, were introduced into the limiter shadow region for exposure to deuterium plasmas, and then withdrawn into an appended UHV chamber for thermal desorption measurements. For unoxidized samples exposed at the vacuum vessel wall radius, 1×1015 D cm−2 was retained after exposure to high density (?e=3×1014 cm−3) discharges. Exposure to consecutive series of N discharges produced retention proportional to N1/2.
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28.52.-s Fusion reactors
52.40.Hf Plasma-material interactions; boundary layer effects
52.70.Nc Particle measurements

Properties and applications of ion‐implanted alloys

S. M. Myers

J. Vac. Sci. Technol. 17, 310 (1980); http://dx.doi.org/10.1116/1.570422 (5 pages) | Cited 1 time

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Ion implantation is a controlled and versatile means for near‐surface alloying of metals. Supersaturated solutions, meastable compounds, amorphous phases, and equilibrium alloys have been produced. Uses include the investigation of metastable phases, characterization of alloying reactions ocurring in conventional materials, and improvement of surface properties such as hardness, wear, and corrosion. A brief review is given of the physical processes occurring during ion implantation, the types of alloys which result, and representative applications.
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61.66.Dk Alloys
61.72.U- Doping and impurity implantation
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
61.72.jd Vacancies
61.72.jj Interstitials

Survey of ion plating sources

Talivaldis Spalvins

J. Vac. Sci. Technol. 17, 315 (1980); http://dx.doi.org/10.1116/1.570377 (7 pages) | Cited 3 times

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Ion plating is a plasma deposition technique where ions of the gas and the evaporant have a decisive role in the formation of a coating in terms of adherence, coherence, and morphological growth. The range of materials that can be ion plated is predominantly determined by the selection of the evaporation source. Based on the type of evaporation source, gaseous media, and mode of transport, the following will be discussed: resistance, electron beam, reactive ion beam evaporation, and sputtering. Ionization efficiencies and evaporant energies in the glow discharge determine the percentage of atoms which are ionized under typical ion plating conditions. The plating flux consists of a small number of energetic ions and a large number of energetic neutrals. The plating flux energy distribution ranges from thermal energies up to the voltage applied to the discharge. The various reaction mechanisms which contribute to the exceptionally strong adherence—formation of a graded substrate/coating interface are not fully understood; however, the controlling factors are evaluated. The influence of process variables on the nucleation and growth characteristic are illustrated in terms of morphological changes which for example affect the mechanical and tribological properties of a coating.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
52.80.Hc Glow; corona

Effects of hydrogen incorporation in some deposited metallic thin films

Donald E. Meyer

J. Vac. Sci. Technol. 17, 322 (1980); http://dx.doi.org/10.1116/1.570378 (5 pages) | Cited 3 times

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Incorporation of gases in thin films, either added purposely or inherently present due to deposition system or process, can have significant effects on thin film stress and electromigration. Aluminum thin films which effects on thin film stress and electromigration. Aluminum thin films which were deposited in high partial pressures of hydrogen mostly in the atomic state were observed to have unusually long mean times to failure for current densities above 1×106 A/cm2. The role of hydrogen in increasing film conductivity and decreasing grain boundary diffusion is discussed.
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68.60.-p Physical properties of thin films, nonelectronic
81.40.Rs Electrical and magnetic properties related to treatment conditions
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Chemical state of ion‐implanted nitrogen in Fe18Cr8Ni steel

I. L. Singer and J. S. Murday

J. Vac. Sci. Technol. 17, 327 (1980); http://dx.doi.org/10.1116/1.570379 (3 pages) | Cited 11 times

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Auger electron spectroscopy (AES) and x‐ray photoelectron spectroscopy (XPS), in conjunction with ion milling, were used to determine the chemical state of nitrogen implanted at relatively high doses (1016–1018/cm2) into type‐304 steel. Nitrogen atoms were bonded in the nitrided state, at all doses, according to both AES and XPS. As the nitrogen concentration increased, the lineshape of the Cr MVV Auger spectra evolved from that of metallic Cr to Cr nitride; at highest doses, the Fe MVV lineshape could be identified as Fe nitride. Auger and XPS spectra of implanted 304 and thermally nitrided 304 were virtually identical at comparable nitrogen concentrations. The Cr(2p3/2) binding energies of both, however, were about 1 eV lower than found in Cr nitride but 0.5 eV higher than in metallic Cr.
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82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
61.72.U- Doping and impurity implantation
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients

Practical selection of elastomer materials for vacuum seals

R. N. Peacock

J. Vac. Sci. Technol. 17, 330 (1980); http://dx.doi.org/10.1116/1.570380 (7 pages) | Cited 6 times

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Proper selection of polymer seal materials must consider restraints imposed by the application and the properties of available materials. Data and concepts presented enable the working vacuum technician to make an educated selection considering chemical and mechanical properties, outgassing, permeation, and nuclear radiation damage. Early reports on the new perfluoroelastomer Kalrez have shown problems with compression set and adhesion, but these difficulties may have resulted from improper groove design.
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07.30.Kf Vacuum chambers, auxiliary apparatus, and materials

Development of bakeable seals for large noncircular ports on the Tokamak Fusion Test Reactor

R. B. Fleming, R. W. Brocker, D. H. Mullaney, and C. A. Knapp

J. Vac. Sci. Technol. 17, 337 (1980); http://dx.doi.org/10.1116/1.570381 (5 pages)

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The Tokamak Fusion Test Reactor (TFTR), being constructed at the Princeton Plasma Physics Laboratory, has a total of 60 large ports of rectangular and racetrack shape that must be equipped with demountable seals. The largest port is a rectangle about 0.74×0.89 m. Seals must be compatible with a 10−8 Torr base pressure, be bakeable to 250°C, and be capable of remote demounting and resealing. A literature search and initial experiments showed that conventional commercially available sealing approaches were not useful, partly because of the large sizes and the noncircular shapes. Successful tests were made with ’’Helicoflex’’ seals. These seals consisted of a helical Inconel wire, surrounded by a stainless steel jacket that is covered with a soft metal, and were compressed between flat flange surfaces. General results were: a silver covering performed better than aluminum; with a smooth flange surface, higher compression produced better results; and performance was improved by striations produced in flange surfaces along the direction of the seal axis.
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07.30.Hd Vacuum testing methods; leak detectors
52.55.Fa Tokamaks, spherical tokamaks
52.55.Hc Stellarators, torsatrons, heliacs, bumpy tori, and other toroidal confinement devices
28.52.-s Fusion reactors

Ultrahigh vacuum system for ISABELLE full cell

R. Skelton, J. Briggs, T. S. Chou, C. Foerster, and P. Stattel

J. Vac. Sci. Technol. 17, 342 (1980); http://dx.doi.org/10.1116/1.570382 (3 pages)

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A vacuum system consisting of a 40 m long 8.8‐cm‐diam stainless steel tube, pumped by seven pumping stations, has been assembled using automatic welding methods. All components have been fired at 950°C in a vacuum furnace at a pressure <1×10−4Torr. Each pumping station contains a Ti‐sublimator, a 20 1/s ion pump and a UHV gauge. After assembly, the entire system was baked out at 250°C for 24 h. A pressure <1×10−11Torr was reached after titanium flash. In this paper we will discuss: (a) surface treatment of stainless for 10−11 Torr operation, (b) bake out and conditioning cycle to read 1×10−11 Torr, and (c) leak checking at low pressures.
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07.30.Hd Vacuum testing methods; leak detectors
29.20.db Storage rings and colliders

Influence of end‐effects on optimum injection condition for electrons in an orbitron device

M. Feidt and D. Prulmier

J. Vac. Sci. Technol. 17, 345 (1980); http://dx.doi.org/10.1116/1.570383 (6 pages)

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Optimum ionizing efficiency in an orbitron is strongly dependant on end‐effects; they disturb the radial electrostatic field, affect the sensitivity of the device and, at the same time, the optimum positioning of the electron emitter. The ionizing efficiency also depends on space charge effects. The influence of end‐effects in an orbitron varies considerably with the electronic current: it is relatively important for small current (for instance in an ionization gauge for ultrahigh vacuum), and less important at high electronic current (as in an ionic pump).
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07.30.Hd Vacuum testing methods; leak detectors
52.20.Dq Particle orbits
41.75.Fr Electron and positron beams
52.80.Vp Discharge in vacuum

New design of modulated Bayard–Alpert gauge

Z. Y. Hua, X. L. Yang, S. X. Qiu, and J. L. Zhuge

J. Vac. Sci. Technol. 17, 351 (1980); http://dx.doi.org/10.1116/1.570385 (4 pages)

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The fundamental equations of the modulated Bayard–Alpert gauge (MBAG) introduced by Redhead are briefly discussed. X‐ray effects from the modulator may be weakened appreciably by using a ’’pin‐to‐pin’’ (PTP) collector–modulator structure; the figure‐of‐merit (Q), which measures the degree of extension of the lowest measurable pressure with respect to a Bayard–Alpert gauge (BAG), can be directly determined from the experimental results. A new operating mode is proposed such that the modulator potential does not switch from the grid potential to the collector potential, but varies always positively with respect to the cathode with an alternating voltage of very low frequency (typically 1 Hz) superimposed on a chosen dc potential. The collector current is then detected by a two‐phase lock‐in amplifier. The modulator–collector capacitance of the PTP gauge is only 1.7×10−5 F. The figure‐of‐merit Q calibrated is about 100 so that the lowest measurable pressure of this gauge is in the order of 10−10 Pa (10−12 Torr).
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07.30.Dz Vacuum gauges
07.30.Hd Vacuum testing methods; leak detectors
07.50.-e Electrical and electronic instruments and components

Self‐modulating ion gauge

D. Edwards and C. Lanni

J. Vac. Sci. Technol. 17, 355 (1980); http://dx.doi.org/10.1116/1.570386 (2 pages)

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A Bayard–Alpert ionization pressure gauge has been modified by shortening the collector wire thereby reducing the x‐ray limit from ∠2.5×10−11 to ∠0.6×10−11 Torr. In addition it has proven possible to modulate this gauge and thus make an in situ determination of the x‐ray limit without the introduction of a modulation electrode. Thus a self‐modulating, low x‐ray limit ion gauge has been developed at reasonably low cost and seems particularly suited to the ISABELLE ultrahigh vacuum system.
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07.30.Dz Vacuum gauges
29.20.db Storage rings and colliders

Characterization of commercial black chrome coatings

D. M. Fell, L. L. Tongson, S. V. Krishnaswamy, R. Messier, and I. S. T. Tsong

J. Vac. Sci. Technol. 17, 358 (1980); http://dx.doi.org/10.1116/1.570387 (4 pages) | Cited 4 times

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A comparative study of the optical properties and chemical composition of three commercially prepared black chrome solar absorber coatings has been made. In all these samples, the visible and IR spectra were nearly the same and showed no peaks corresponding to hydrated chromium oxides. The chemical composition was obtained by AES and sputter‐induced photon spectrometry (SIPS). The hydrogen profiles by SIPS indicated the presence of H (or OH) at varying levels in these coatings. Although the AES and SIPS analyses showed significant compositional profile differences among samples, their optical properties were quite comparable.
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68.55.-a Thin film structure and morphology
78.66.-w Optical properties of specific thin films
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
68.60.-p Physical properties of thin films, nonelectronic

Characterization of black Ge selective absorbers

P. Swab, S. V. Krishnaswamy, and R. Messier

J. Vac. Sci. Technol. 17, 362 (1980); http://dx.doi.org/10.1116/1.570388 (4 pages) | Cited 9 times

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We have prepared structurally anisotropic black Ge films by rf sputtering and postdeposition etching. By careful control of various sputtering condition such as rf power, gas pressure, deposition time, and other parameters such as nature and roughness of the substrate and etching time, we can alter the morphology of these films and optimize the selective absorbing properties. Postdeposition etching in 30% H2O2 has reduced the reflectance from approximately 45% to less than 1% in the best case. This etching behavior is also observed for films immersed in water for several weeks at room temperature. This is explained on the basis of oxidation through aligned voids. The etching behavior of various films and correlation between the resulting microstructure and optical properties is discussed. Further, the various microstructures are classified and understood using the structure zone models.
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68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering
61.43.Fs Glasses
61.43.-j Disordered solids
78.66.-w Optical properties of specific thin films
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures

Oxygen chemisorption on tin oxide: Correlation between electrical conductivity and EPR measurements

Shih–Chia Chang

J. Vac. Sci. Technol. 17, 366 (1980); http://dx.doi.org/10.1116/1.570389 (4 pages) | Cited 36 times

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Chemisorption of oxygen on tin oxide is studied. Correlations between electric conductivity and electron paramagnetic resonance (EPR) measurements are reported.
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68.08.-p Liquid-solid interfaces
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
72.80.-r Conductivity of specific materials
76.30.-v Electron paramagnetic resonance and relaxation

Preparation of thin films for solar energy utilization

D. M. Mattox

J. Vac. Sci. Technol. 17, 370 (1980); http://dx.doi.org/10.1116/1.570391 (4 pages) | Cited 1 time

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Thin film deposition techniques have made and are making a significant contribution to solar energy utilization. Commercial applications of thin films include photothermal selective absorbers formed by electroplating, chemical conversion, and vacuum processing; solar reflectors formed by vacuum processes; heat reflectors formed by vacuum processes and spray pyrolysis; and antireflection coating formed by vacuum processes and chemical leaching and the metallization of photovoltaic cells. CdS/Cu2S photovoltaics formed by vacuum processes and spray pyrolysis are also close to commercial utilization. Principal concerns in thin films applications include economics of fabrication and environmental stability of the thin film materials. At the present time, for many applications the best and most economical film deposition technology is not yet defined. One of the major problems with thin film evaluation is the lack of acceptable testing procedures particularly as related to lifetime. Research and development is continuing in the application of sophisticated thin films to photovoltaic conversion and other applications. This paper reviews the status of thin film in solar energy utilization.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
84.60.Jt Photoelectric conversion
85.60.Dw Photodiodes; phototransistors; photoresistors

Summary Abstract: Spray‐on antireflection coatings for silicon solar cells

Werner Kern and Edwin Tracy

J. Vac. Sci. Technol. 17, 374 (1980); http://dx.doi.org/10.1116/1.570392 (2 pages) | Cited 1 time

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Abstract Unavailable
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42.79.Wc Optical coatings
78.66.-w Optical properties of specific thin films
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
72.40.+w Photoconduction and photovoltaic effects
42.25.Hz Interference

Importance of the interface in noncrystalline (poly and amorphous) conductor–insulator–semiconductor (CIS) solar cells

R. Singh and K. Rajkanan

J. Vac. Sci. Technol. 17, 376 (1980); http://dx.doi.org/10.1116/1.570393 (4 pages)

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In recent years a new class of photovoltaic device, namely the conductor–insulator–semiconductor (CIS) solar cell, has emerged. The top layer in these devices may be a transparent metal film, oxide‐semiconductor or a combination of them leading to a wide variety of metal‐insulator‐semiconductor (MIS) and semiconductor–insulator–semiconductor (SIS) solar cells. Due to improved understanding of the interface between the top layer and the single crystal base semiconductor, efficiencies above 17% have been realized in these structures. However, CIS‐type solar cells made on nonrecrystallized poly and amorphous semiconductors are usually of low efficiency. In this paper we show that the native grown oxide may not be capable of forming a good interface and deposited dielectrics are required for noncrystalline CIS solar cells. We present the criteria for selecting the insulating layer.
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84.60.Jt Photoelectric conversion
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.61.Ng Insulators
73.40.Ty Semiconductor-insulator-semiconductor structures

Compressive stress and inert gas in Mo films sputtered from a cylindrical‐post magnetron with Ne, Ar, Kr, and Xe

D. W. Hoffman and John A. Thornton

J. Vac. Sci. Technol. 17, 380 (1980); http://dx.doi.org/10.1116/1.570394 (4 pages) | Cited 25 times

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Previous work by the present authors on metal films sputtered from cylindrical‐post magnetron sources has established the existence of an abrupt transition in internal stress and other properties that occurs as the working pressure is lowered. High compressive stress, maximum reflectance, minimum resistivity, entrapped inert gas, and dense, Zone‐T microstructure were found in a wide variety of pure metals and alloys when sputtered in argon at sufficiently low pressures. The present study reports this same phenomenon for a single metal (Mo) sputtered in a variety of gases (Ne, Ar, Kr, Xe). In this case the transition pressure varies inversely with the mass of the sputtering gas, from less than 0.3 Pa for xenon to over 0.9 Pa for neon. The concentration of inert gas in the films also varies inversely with the mass, increasing by two orders of magnitude from krypton to neon. Deposition through a narrow slit‐aperature established that the entrapped gas comes from the sputtering cathode (backscattered, neutralized ions) by line‐of‐sight trajectories. Moreover, right‐angle scattering of gas from the sides of the cylindrical‐post magnetron, as viewed by a given substrate, becomes increasingly prominent for the heavier gasses, and is shown to be a principal factor in causing compressive stresses. The evidence indicates that compressive stress and the presence of entrapped inert gas in the films are both by‐products of inert gas bombardment of the condensing material during deposition. A significant correlation is found between the variation in transition pressure and the decreased scattering cross sections reported in the literature for energetic inert gas particles, such as those scattered from sputtering targets of greater mass.
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68.60.-p Physical properties of thin films, nonelectronic
81.15.Cd Deposition by sputtering
84.40.Fe Microwave tubes (e.g., klystrons, magnetrons, traveling-wave, backward-wave tubes, etc.)

Influence of residual gases on the properties of dc magnetron‐sputtered aluminum–silicon

R. S. Nowicki

J. Vac. Sci. Technol. 17, 384 (1980); http://dx.doi.org/10.1116/1.570395 (4 pages) | Cited 4 times

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The influence of trace residual gases on the film specularity, grain size, and resistivity of aluminum–1.5% silicon alloy was investigated. Oxygen and nitrogen are shown to be the major contributors to loss of film specularity. The reflectance is decreased from ca. 90% to 10%–20% when oxygen or nitrogen are present in the sputtering system at about 5×10−3 Pa above the vacuum system residual pressure (8×10−5 Pa in this case). Hydrogen is shown to have no significant effect on reflectance at this level of contamination. The resultant grain size variations show only small changes when correlated with each contaminant. However, there appears to be a separate, crystalline phase which appears with hydrogen and nitrogen. Additionally, film analysis by nuclear reaction techniques shows some direct correlation between loss of reflectance and carbon content. The results are discussed with regard to microelectronic device processing.
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81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology
78.30.Er Solid metals and alloys
78.40.Kc Metals, semimetals, and alloys
34.50.-s Scattering of atoms and molecules

Summary Abstract: Copper distribution in sputtered Al/Cu films

D. R. Denison and L. D. Hartsough

J. Vac. Sci. Technol. 17, 388 (1980); http://dx.doi.org/10.1116/1.570396 (1 page) | Cited 1 time

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66.90.+r Other topics in nonelectronic transport properties of condensed matter (restricted to new topics in section 66)
68.55.-a Thin film structure and morphology
68.70.+w Whiskers and dendrites (growth, structure, and nonelectronic properties)
68.90.+g Other topics in structure, and nonelectronic properties of surfaces and interfaces; thin films and low-dimensional structures (restricted to new topics in section 68)

Resputtering effects in Ba(Pb, Bi)O3 perovskites

L. R. Gilbert, R. Messier, and S. V. Krishnaswamy

J. Vac. Sci. Technol. 17, 389 (1980); http://dx.doi.org/10.1116/1.570397 (3 pages) | Cited 6 times

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A resputtering effect in Ba(Pb, Bi)O3 has been found to vary from complete film and partial substrate erosion to slightly altered film surface microstructure and bulk composition. It is strongly dependent on the sputtering conditions; only the films prepared at the higher gas pressures (≳200 mTorr) show no resputtering, apparently due to gas phase interactions. The most striking result, other than the obvious surface erosion, is the Ba deficiency, ranging from 10 to 70 at. %, that is directly related to the degree of resputtering. Similar results have been seen for other alkaline earth perovskites.
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81.15.Cd Deposition by sputtering
79.20.-m Impact phenomena (including electron spectra and sputtering)
77.55.-g Dielectric thin films
74.78.-w Superconducting films and low-dimensional structures

Quantitative analysis of Ti–W films

L. D. Hartsough, A. Koch, J. Moulder, and T. Sigmon

J. Vac. Sci. Technol. 17, 392 (1980); http://dx.doi.org/10.1116/1.570398 (4 pages) | Cited 3 times

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Resistivity of bias‐sputtered Ti–W films was found to depend on the Ti:W ratio in the films, which was controlled by rf substrate bias. Auger depth profiles gave Ti:W about half the expected values. Films deposited at 0, 150, and 300 V bias chosen for further study were analyzed by atomic absorption (AAS), Rutherford backscattering (RBS), and Auger electron (AES) spectroscopies. Large discrepancies were found between techniques. AES tends to give low Ti:W ratios because of preferential Ti sputtering during analysis. The RBS and AES data were used to determine the differential sputtering yield of Ti and W from the film and thus provide a basis for quantitative analysis from AES data. The yield ratio was found to vary linearly with composition of the altered surface layer as r=3.0–4.0 (Ti:W). Advantages, disadvantages, and factors affecting the accuracy of each technique are discussed.
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68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering
73.61.At Metal and metallic alloys

Sputtering of single and multiple component materials

Peter Sigmund

J. Vac. Sci. Technol. 17, 396 (1980); http://dx.doi.org/10.1116/1.570399 (4 pages) | Cited 10 times

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This article summarizes the basic assumptions underlying conventional sputtering theory and their implications. An attempt will be made to specify those areas where existing theory appears to be confirmed as well as other areas where considerable uncertainties prevail. Specific comments concern the significance of spike phenomena as opposed to linear collision cascades, sputtering of compounds, recoil implantation, and atomic mixing.
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81.15.Cd Deposition by sputtering
79.20.-m Impact phenomena (including electron spectra and sputtering)
41.75.Ak Positive-ion beams
41.75.Cn Negative-ion beams
34.50.Lf Chemical reactions

Source of radiation damage to MOS devices during S‐GunR metallization

J. L. Vossen, J. J. O’Neill, G. W. Hughes, F. A. Taft, and R. Snedeker

J. Vac. Sci. Technol. 17, 400 (1980); http://dx.doi.org/10.1116/1.570465 (3 pages) | Cited 5 times

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A study of radiation damage to MOS capacitors metallized using an S‐Gun magnetron sputtering source has shown that hole traps are created that cannot be annealed out at metal–sinter temperatures up to 500°C. These hole traps can be thermally emptied by 500°C annealing but subsequent high–energy irradiation results in larger flatband–voltage shifts for S‐Gun metallized capacitors than for evaporated Al capacitors. Precoating the oxides with 100 Å of evaporated Al resulted in a reduction in this damage. Precoating with 300 Å of evaporated Al eliminated the damage entirely. To determine whether magnetron sputtering damage was due to electron bombardment or vacuum ultraviolet (VUV) irradiation, oxides were precoated with 100 and 300 Å of evaporated aluminum and then irradiated with 600 eV electrons to a dose of 500 μC/cm2. This was the estimated maximum dosage that could occur during magnetron–sputtering metallization. The electron induced flatband shift could be annealed completely at 450°C for 40 min in forming gas. After subsequent 1 MeV electron irradiation to a dose of 106 rad the threshold‐voltage shifts for 600 eV electron bombarded samples were the same as for those not bombarded. Since 600 eV electron bombardment damage can be annealed completely while magnetron‐sputtering damage cannot we conclude that S‐Gun damage is caused by VUV photons. In actual MOS integrated circuits a polysilicon gate of any reasonable thickness should be adequate for absorbing the photons of energy ?8 eV that create radiation damage in SiO2, and no damage should occur.
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61.80.-x Physical radiation effects, radiation damage
68.55.-a Thin film structure and morphology
73.40.Ns Metal-nonmetal contacts
52.25.Os Emission, absorption, and scattering of electromagnetic radiation

Effect of H2 on an argon discharge for planar magnetron sputtering

S. Maniv and W. D. Westwood

J. Vac. Sci. Technol. 17, 403 (1980); http://dx.doi.org/10.1116/1.570466 (4 pages) | Cited 4 times

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A planar magnetron has been operated in Ar/H2 mixtures to determine whether H2 has a significant effect on the sputtering characteristics as it does in diode systems. An Al target was sputtered in dc and rf discharges at powers up to 2.3 kW and H2/Ar ratios from 0 to 1.1. At a fixed argon flow, the total pressure increased from 0.6 to 1.3 Pa as the H2 flow rate increased to 4.4 cc/min. For the same rf power, the target self‐bias voltage was independent of the H2 partial pressure but the dc impedance did increase with H2 flow; to maintain a current of 3A, the dc voltage had to be increased from 370 to 450 V as the H2 flow rate increased to 5.0 cc/min. The deposition rate of Al was measured by a quartz microbalance as a function of power and no significant decrease in rate was evident up to the highest H2/Ar ratio. In diode sputtering, a ratio of 0.01 causes a 10% decrease in rate. A set of reactions for the formation and removal of Ar+, H+, and ArH+ have been used to model the relative ion concentrations. A correlation between the model and experimental results suggests that the H+ concentration is significant in the diode case and causes a decrease in sputtering rate but it is negligibly small in the magnetron discharge due to the much higher electron density and the electron trapping.
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81.15.Cd Deposition by sputtering
84.40.Fe Microwave tubes (e.g., klystrons, magnetrons, traveling-wave, backward-wave tubes, etc.)

Radio frequency magnetron sputtering of thick film amorphous beryllium

R. J. Burt, S. F. Meyer, and E. J. Hsieh

J. Vac. Sci. Technol. 17, 407 (1980); http://dx.doi.org/10.1116/1.570467 (4 pages) | Cited 3 times

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Thick film coatings of beryllium, needed for the low‐Z ablator layer in proposed laser fusion targets, have been prepared using high rate magnetron rf sputtering. The requirements for these Be coatings include thicknesses from 5 to 50 μm, complete freedom from surface defects, and an average surface roughness of 100 nm or less. These specifications are difficult to achieve if crystalline growth occurs during sputtering, since the surface roughness of thick grainy films can be on the order of micrometers. We have sputtered very smooth, dense Be films up to 25 μm thick with surface roughness less than 100 nm. X‐ray diffraction analysis of impurity doped films indicates an amorphous‐like structure. Impurity stabilized amorphous Be with smooth surfaces is reported on both 15°C cooled copper and nominal 200°C glass substrates. The sputtering parameters (substrate temperature, deposition rate, argon pressure, and impurity gas levels) affecting surface roughness and film structure are discussed in terms of SEM, AES, and x‐ray diffraction results.
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81.15.Cd Deposition by sputtering
61.05.C- X-ray diffraction and scattering
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Effects of deposition parameters on the properties of superconducting rf reactively sputtered NbN films

S. A. Wolf, I. L. Singer, E. J. Cukauskas, T. L. Francavilla, and E. F. Skelton

J. Vac. Sci. Technol. 17, 411 (1980); http://dx.doi.org/10.1116/1.570469 (4 pages) | Cited 15 times

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Thin films of NbN were reactively rf sputtered using a range of substrate temperatures and nitrogen partial pressures. The effects of these deposition parameters was to change the morphology rather than the stoichiometry of the sputtered films. Auger composition analysis, x‐ray diffractometry, resistivity, resistivity ratio, superconducting critical temperature (Tc), and critical magnetic field [Hc2(T)] data were all used to determine the microstructure of the films and how it related to the measured properties. The best metallic films had Tc’s?16 K, Hc2(T)’s of 18 T and were prepared at 600°C using 1 Pa argon, 0.03 Pa N2, and a target power density of 9.8 W/cm2. All the films had carbon impurities at concentrations estimated to be between 1 and 15%. X‐ray analysis indicated the presence of a face‐ centered‐cubic structure, assumed to be the Bl phase, in addition to a second phase in one of the samples. The best superconducting films had several percent carbon. Those films prepared with an excess nitrogen partial pressure had negative temperature derivatives of resistance indicating a granular column void type microstructure. Films prepared with a deficient nitrogen partial pressure had very low Tc0’s (<4.2 K). A film prepared at ambient temperature had the least carbon, was nearly stoichiometric NbN, but had degraded Tc and enhanced Hc2(0).
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74.25.-q Properties of superconductors
81.15.Cd Deposition by sputtering
61.66.Dk Alloys
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Closed loop control of thin film sputter deposition processes using glow discharge mass spectroscopy

T. C. Tisone, B. F. T. Bolker, and T. S. Latos

J. Vac. Sci. Technol. 17, 415 (1980); http://dx.doi.org/10.1116/1.570470 (5 pages) | Cited 3 times

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Sputtering in general can be viewed as reactive sputtering due to the presence of virtual leaks in addition to the normally considered controlled gas leaks. A method is needed to reproducibly control critical film properties for practical manufacturing situations, especially in the case where the incorporation of precise amounts of a reactive gas like O2 or N2 are desired in a deposited film. These considerations have led to the development of a closed loop control system which uses glow discharge mass spectroscopy (GDMS) to detect plasma ions and thus act as a transduction element for feedback control to a servo leak valve. An LSI–ll microprocessor provides real time control of the desired process signals. GDMS control is more reproducible than merely controlling gas flow or monitoring gas partial pressure since the former does not account for virtual leaks, and the latter does not always reveal the reactive species present in the plasma. The general theory behind this approach is discussed, along with consideration of the system design and hardware. System control is achieved by using an algorithm based on ratios of ion signals in order to eliminate nonreproducibility caused by variation in the multiplier gain of the GDMS. Representative GDMS spectra and the techniques for determining optimum control signals are presented. In the Ta system, to control small amounts of O2, the Ta+/TaO+ ratio is used; and for control of N2, the Ta+/TaN+ ratio is satisfactory. For Ta films reactively sputtered in either O2 or N2, GDMS control ratios are well correlated with resultant film composition and electrical properties. Comparisons between GDMS control ratios of TaO cermet films and their respective Auger profiles, microprobe measurements, ρ and TCR are shown. Validity of this closed loop control concept is further demonstrated by the fact that three sputtering systems, including one in manufacturing, are now in operation and during a two‐year period have provided similarly reproducible films to a ±5% level.
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81.15.Cd Deposition by sputtering
07.07.Tw Servo and control equipment; robots
07.75.+h Mass spectrometers
52.80.Hc Glow; corona

Summary Abstract: Investigation and prevention of sputter target cracking using acoustic emission testing

A. B. Cistola

J. Vac. Sci. Technol. 17, 420 (1980); http://dx.doi.org/10.1116/1.570471 (1 page)

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Abstract Unavailable
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81.15.Cd Deposition by sputtering
43.35.Sx Acoustooptical effects, optoacoustics, acoustical visualization, acoustical microscopy, and acoustical holography
43.40.Le Techniques for nondestructive evaluation and monitoring, acoustic emission
43.35.-c Ultrasonics, quantum acoustics, and physical effects of sound

Adhesion of nickel films on graphite

J. R. Snyder, M. A. Smith, and L. L. Levenson

J. Vac. Sci. Technol. 17, 421 (1980); http://dx.doi.org/10.1116/1.570472 (4 pages) | Cited 1 time

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Nickel dots from 0.8 to 1.6 mm in diameter and up to 500 nm thick were evaporated onto the stepped (0001) basal surface of stress‐annealed pyrolytic graphite. Leads were soldered or glued to the as‐deposited dots and increasing stress normal to the graphite basal planes was applied to the leads until rupture occurred, usually ≳1 MPa. The distribution of stress‐at‐failure data followed Weibull failure statistics. Auger electron spectroscopy (AES) of the fracture surface of dots ?200 nm thick showed only graphite. In‐depth AES revealed that nickel carbide was present at the nickel–graphite interface. Samples annealed at 400°C for 2 h had a lower characteristic tensile strength than unannealed samples and separated at the interface where AES detected no nickel carbide.
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68.60.-p Physical properties of thin films, nonelectronic
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Modification of evaporated chromium by concurrent ion bombardment

D. W. Hoffman and M. R. Gaerttner

J. Vac. Sci. Technol. 17, 425 (1980); http://dx.doi.org/10.1116/1.570473 (4 pages) | Cited 23 times

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Bombardment of thermally evaporated chromium films with energetic inert gas ions during deposition (ion peening) causes marked changes in properties when the dose exceeds a minimum critical value. The property changes are characterized by a sharp reversal of intrinsic stress from high‐tensile to high‐compressive values, increases in the optical reflectance and optical density to levels approaching pure bulk chromium, and enhanced resistance to oxidation on heating. Observations of the shift in critical ion dose with accelerating voltage and ionic mass (argon and xenon) indicate that the ion peening transition may be controlled by the transfer of momentum to the depositing film. This observation is found to be consistent with results obtained in low‐pressure, cylindrical post‐magnetron sputtering, which ion peening was devised to simulate.
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68.60.-p Physical properties of thin films, nonelectronic
61.80.Jh Ion radiation effects
34.50.-s Scattering of atoms and molecules
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Acoustic emission and electron emission during deformation of anodized aluminium

J. T. Dickinson, D. B. Snyder, and E. E. Donaldson

J. Vac. Sci. Technol. 17, 429 (1980); http://dx.doi.org/10.1116/1.570474 (4 pages) | Cited 9 times

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Tribostimulated exoelectron emission provides a sensitive way to characterize anodic films on aluminium. This paper describes the detection of acoustic emission (AE) and electron emission (EE) during the tensile deformation of anodized aluminum. It is shown that the observed bursts of AE are associated with cracking of the oxide, that AE and EE count rates vs strain are closely related, and that most EE occurs very soon after AE events. Evidence is also presented for a component of EE unrelated to AE which is attributed to chemi‐emission.
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68.60.-p Physical properties of thin films, nonelectronic
68.35.Gy Mechanical properties; surface strains
68.35.Iv Acoustical properties
79.75.+g Exoelectron emission
81.40.Lm Deformation, plasticity, and creep

Effect of impurities on the PtSi–Si interface and the PtSi surface

C. A. Crider, J. M. Poate, J. E. Rowe, T. T. Sheng, and S. D. Ferris

J. Vac. Sci. Technol. 17, 433 (1980); http://dx.doi.org/10.1116/1.570475 (4 pages) | Cited 1 time

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Platinum silicides have been prepared by depositing Pt thin films under UHV and controlled impurity ambients. The interfaces and surfaces have been characterized by Rutherford backscattering spectroscopy, cross sectional TEM techniques and SEM. Clean depositions yielded planar interfaces whereas increasing oxygen contamination produced nonuniform interfaces and surfaces. No differences in interfacial and surface uniformity, reaction rates, and phase growth sequence were observed between samples cleaned with normal device processing steps and UHV sputter cleaned and annealed samples provided the Pt films were impurity free. The influence of interfacial oxides on silicide kinetics has also been determined.
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
68.55.-a Thin film structure and morphology
81.20.-n Methods of materials synthesis and materials processing
82.20.Pm Rate constants, reaction cross sections, and activation energies

Quantitative characterization of high strength aluminum foils vapor deposited on curved surfaces

R. W. Springer, B. L. Barthell, and D. Rohr

J. Vac. Sci. Technol. 17, 437 (1980); http://dx.doi.org/10.1116/1.570476 (4 pages) | Cited 4 times

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The pulsed Gas Process (PGP) has been used to produce Al/AlxOy The pulsed Gas Process (PGP) has been used to produce Al/AlxOy layered coatings on a cylindrical surface. Previous work1 has shown that the yield strength and surface morphology of aluminum films deposited at normal incidence is quite sensitive to the spacing of the oxygen gas pulse. The mechanical testing data follow a Hall–Petch equation for the yield strength. This gives an ideal range of conditions for test on curved surfaces. Free standing aluminum foils on the order of 20–35 μm thick have been deposited using PGP variations on a rotating cylindrical substrate with varying angles of deposit. The results show porosity in the unpulsed material, and fully dense material in highly pulsed material deposited at ±60° or less settings. The fully dense material shows ductility and the yield strength is reduced by a factor of 0.84 over the predicted flat plate strength.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.70.-q Methods of materials testing and analysis
68.55.-a Thin film structure and morphology
68.60.-p Physical properties of thin films, nonelectronic

Growth of single‐crystal metastable InSb1−xBix and (GaSb)1−xGex semiconducting films

K. C. Cadien, J. L. Zilko, A. H. Eltoukhy, and J. E. Greene

J. Vac. Sci. Technol. 17, 441 (1980); http://dx.doi.org/10.1116/1.570477 (4 pages) | Cited 4 times

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Epitaxial metastable InSb1‐xBix alloys with InBi concentrations up to 12 mol % and (GaSb)1−xGex alloys with compositions across the pseudobinary phase diagram have been grown on GaAs substrates by multitarget rf sputtering. The InSb1−xBix film were n‐type while the (GaSb)1−xGex films were p‐type. Polycrystalline films from both alloy systems grown on Corning 7059 glass substrates exhibited strong (220) preferred orientation with lattice constants obeying Vegard’s law. Annealing experiments showed that the InSb1−xBix films were metastable in two directions on the In–Sb–Bi ternary phase diagram—the solid solubility of tetragonal InBi in zinc blende structure InBi was increased by more than a factor of 4 and the width of the InSb–InBi pseudobinary ’’line compound’’ phase field was increased to ?0.5%. Both InSb1−xBix and (GaSb)1−xGex films were found to be stable to decomposition during long anneals which, in the case of InSb1−xBix, were within 100°C of the equilibrium liquidus temperature. Annealing studies carried out on (GaSb)0.38Ge0.62 showed that such films transform from the as‐deposited (220) oriented alloy to GaSb–rich and Ge–rich phases in which the solute concentrations continuously decrease until an equilibrium two phase alloy is obtained. The activation energy for this process is 3.1 eV.
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68.55.-a Thin film structure and morphology
64.60.My Metastable phases
81.15.Cd Deposition by sputtering

Electrothermal model of switching in amorphous silicon films

S. K. Dey

J. Vac. Sci. Technol. 17, 445 (1980); http://dx.doi.org/10.1116/1.570478 (4 pages) | Cited 5 times

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The pulse repetition frequency dependence of the delay time, td, in amorphous silicon films produced by electron‐beam evaporation in a Ti–Si–Ti sandwich structure has been found to give two opposite trends. Below about 1 kHz, td increases as the frequency is increased but is independent of the pulse duration. Above 1 kHz, td decreases with frequency and is also reduced in magnitude by increasing the pulse width. In this paper, an electrothermal mechanism of switching has been used to explain the above phenomenon satisfactorily. The predictions of the model as regards td decreasing with increasing over‐voltage and increasing film thickness, the threshold voltage exhibiting a half‐power law relationship with thickness and its temperature dependence, and the effect of space–charge injection around the electrodes are confirmed by experiments. Finally, a view of switching combining both thermal and electronic elements is presented.
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73.40.Sx Metal-semiconductor-metal structures
73.61.Cw Elemental semiconductors
73.61.Ey III-V semiconductors
73.61.Ga II-VI semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Comparison of the early stages of condensation of Cu and Ag on Mo(100) with Cu and Ag on W(100)

F. Soria and H. Poppa

J. Vac. Sci. Technol. 17, 449 (1980); http://dx.doi.org/10.1116/1.570479 (4 pages) | Cited 6 times

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The adsorption and condensation of Cu and Ag, up to several monolayers in thickness, onto Mo(100) has been observed at pressures below 2 ×10−10 Torr in a study that used combined LEED, Auger, TDS, and work function measurements in a single experimental setup. The results show that Cu behaves similarly on Mo(100) and W(100) substrates, while some differences are found for Ag adsorption.
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68.55.-a Thin film structure and morphology
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Low‐energy electron diffraction study of the surface defect structure of Ag (111) epitaxially grown on mica

D. G. Welkie, M. G. Lagally, and R. L. Palmer

J. Vac. Sci. Technol. 17, 453 (1980); http://dx.doi.org/10.1116/1.570481 (5 pages) | Cited 3 times

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The use of low‐energy electron diffraction (LEED) for the quantitative determination of finite‐domain size effects in surfaces and for the separation of domain size effects and strain effects is demonstrated for the first time. Measurements are made of the angular distribution of intensity in diffracted beams observed in LEED from Ag (111) thin film grown epitaxially on mica. The broadening in these beams beyond that due to the finite instrumental resolution is analyzed in terms of three mechanisms limiting the long‐range order on the surface: steps, mosaic structure, and strain parallel to the surface. It is demonstrated that no steps exist, and that the considerable broadening that is present is due to mosaic structure rather than strain. The average size of this mosaic structure, as well as the average misorientation of domains, is determined.
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
61.72.-y Defects and impurities in crystals; microstructure
68.55.-a Thin film structure and morphology

Mixed valent ytterbium‐aluminium thin films

G. G. Tibbetts and W. F. Egelhoff

J. Vac. Sci. Technol. 17, 458 (1980); http://dx.doi.org/10.1116/1.570482 (3 pages)

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The criteria for the formation of thin mixed valent films have been studied by depositing thin layers of Yb on an Al(100) substrate and carefully controlling the interdiffusion. X‐ray photoemission (XPS) of pure Yb surface layers shows only the divalent character of the filled f14 shell. Formation of a mixed valent state begins when interdiffusion becomes substantial above 150°C. Further heating above 350°C causes the Yb to revert to the divalent state despite the fact that a charge transfer mechanism would predict the presence of a substantial trivalent component. It is clear that the divalent component is not predominant on the surface of our mixed valent film since low intensity ion sputtering converts the trivalent component to the divalent. Finally, we observe an increase in the divalent character of an alloy of stochiometry YbAl3 at low temperatures smaller than that predicted by theory.
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68.55.-a Thin film structure and morphology
68.60.-p Physical properties of thin films, nonelectronic
79.60.Jv Interfaces; heterostructures; nanostructures
66.30.Ny Chemical interdiffusion; diffusion barriers

Summary Abstract: Characterization of the habit planes of small single crystal particles

K. Heinemann, H. Poppa, and M. J. Yacaman

J. Vac. Sci. Technol. 17, 461 (1980); http://dx.doi.org/10.1116/1.570483 (1 page) | Cited 1 time

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61.66.Bi Elemental solids
07.60.Ly Interferometers
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
07.05.Bx Computer systems: hardware, operating systems, computer languages, and utilities

Study of thin Nb oxide films

Pramod C. Karulkar and James E. Nordman

J. Vac. Sci. Technol. 17, 462 (1980); http://dx.doi.org/10.1116/1.570484 (4 pages) | Cited 8 times

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Niobium films oxidized to thicknesses less than 30 Å by using different oxidation techniques (e.g. thermal, dc glow discharge, and rf glow discharge) were studied by XPS. Chemical shifts in the binding energies of Nb 3d (3/2) and Nb 3d (5/2) levels were used to identify the various oxides of Nb. Niobium films oxidized by thermal or dc glow discharge oxidation showed an outermost layer of Nb2O5. A pure Nb signal could be seen when the oxide films were thin. Suboxides could not be seen directly in XPS data. The composition of the oxide films produced by an rf glow discharge oxidation was found to depend on the rf peak to peak voltage and under certain conditions the XPS spectra clearly showed the existence of NbO. A discrepancy was observed between the oxide thicknesses estimated from the XPS data and the relative values of resistances of Nb–Nb oxide–Pb tunnel junctions fabricated by using these oxide films as barriers. The results are briefly discussed in terms of the difference in the oxidation processes and their importance in junction fabrication.
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68.60.-p Physical properties of thin films, nonelectronic
73.61.Ng Insulators
73.40.Rw Metal-insulator-metal structures
81.65.-b Surface treatments

HF vapor phase etching (HF/VPE): Production viability for semiconductor manufacturing and reaction model

D. F. Weston and R. J. Mattox

J. Vac. Sci. Technol. 17, 466 (1980); http://dx.doi.org/10.1116/1.570485 (4 pages) | Cited 5 times

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A nonplasma silicon dioxide etch process using anhydrous hydrogen fluoride at reduced pressures has been investigated. This technique involves the interaction of HF vapor with negative photoresist which catalizes subsequent etching beneath the photoresist. Etching in nonphotoresist coated areas can be eliminated by a short in situ plasma pretreatment followed by HF etching at 190 °C, 10 Torr, and 500 sccm in a commercial etch system. Experimental details as well as a proposed reaction mechanism will be presented.
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52.40.Hf Plasma-material interactions; boundary layer effects
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
89.20.Bb Industrial and technological research and development

Observations of stresses in thin films of palladium and platinum silicides on silicon

J. Angilello, F. d’Heurle, S. Petersson, and A. Segmüller

J. Vac. Sci. Technol. 17, 471 (1980); http://dx.doi.org/10.1116/1.570486 (5 pages) | Cited 8 times

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The silicides of Pt (PtSi) and of Pd (Pd2Si and PdSi) were formed by the interaction of metallic thin films with single crystal substrates of Si. The stresses in the silicide films were measured at room temperature from the bending of the Si substrates, obtained via an x‐ray diffraction technique. The stresses vary approximately linearly with the heat treatment temperatures, without pronounced relationship with the different phase formations. For both Pd2Si and PtSi, the stress levels are correlated with the measured lattice parameter. Approximate values of elastic constants and expansion coefficients are derived.
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68.55.-a Thin film structure and morphology
66.30.-h Diffusion in solids
64.70.K- Solid-solid transitions
68.03.-g Gas-liquid and vacuum-liquid interfaces
68.05.-n Liquid-liquid interfaces

Bonding and diffusion at Al and Au interfaces with CdS

L. J. Brillson, R. S. Bauer, R. Z. Bachrach, and J. C. McMenamin

J. Vac. Sci. Technol. 17, 476 (1980); http://dx.doi.org/10.1116/1.570487 (5 pages) | Cited 9 times

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Al and Au interfaces with UHV‐cleaved CdS(101̄0) surfaces have been probed via soft x‐ray photoemission spectroscopy. We find that Al produces a highly localized reaction at the metal‐semiconductor interface, while Au promotes interface diffusion. These bonding differences appear to be characteristic of ionic semiconductor–metal interfaces in general.
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66.30.Ny Chemical interdiffusion; diffusion barriers
73.30.+y Surface double layers, Schottky barriers, and work functions
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
73.40.Cg Contact resistance, contact potential

Thermal diffusion of chromium in polycrystalline CdSe films

S. J. Ingrey, F. R. Shepherd, and W. D. Westwood

J. Vac. Sci. Technol. 17, 481 (1980); http://dx.doi.org/10.1116/1.570489 (4 pages) | Cited 3 times

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The effect of thermal annealing of CdSe and multilayer Cr/CdSe thin films has been studied by Auger spectroscopy and nuclear reaction analysis. Films with thicknesses from 0.05 to 0.3 μm were deposited by evaporation onto glass and platinum substrates and annealed for up to 120 min at temperatures between 240° and 400°C in flowing nitrogen. Auger spectra were obtained as the films were sputtered by 3 keV Ar+ in a scanning Auger microprobe. There was no significant change in the composition of the CdSe films except when CdSe and Cr films were in contact. For example, Cr diffused through a 0.3‐μm overlayer in a few minutes at 300°C. There was an associated increase in the oxygen content of the film. This was confirmed by nuclear reaction analysis using16O (d,p)17O reaction. In the absence of Cr, there was no significant oxygen uptake. Diffusion profiles were obtained by Auger depth studies and an activation energy of 1.2±0.2 eV determined from the temperature dependence. Since Cr is an n‐type dopant in CdSe, the diffusion probably affects the electrical properties and, thus, may have an important effect on CdSe thin film transistors which use Cr as a source‐drain metallization.
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68.60.-p Physical properties of thin films, nonelectronic
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
25.55.-e 3H-, 3He-, and 4He-induced reactions
61.05.C- X-ray diffraction and scattering

Effect of thermal annealing on thin film transistors processed by photoengraving

F. R. Shepherd, H. Nentwich, W. D. Westwood, and S. J. Ingrey

J. Vac. Sci. Technol. 17, 485 (1980); http://dx.doi.org/10.1116/1.570490 (4 pages) | Cited 2 times

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Thin film transistors (TFTs) are of current interest for addressing large‐area flat panel displays. In most cases, in‐vacuum mechanical masking and successive evaporations in a single pumpdown have been used to define the necessary patterns. While this has the advantage of minimizing contamination of the film interfaces, complex and expensive equipment is needed to fabricate high resolution patterns over large areas. We have, therefore, investigated the use of conventional vacuum deposition and photoengraving processes, similar to those used in silicon integrated circuit technology, and have successfully fabricated CdSe TFTs in which the gate and source‐drain levels have been defined by photoengraving. Al and Cr metallizations and Al2O3 dielectric layers have been used. Well‐saturated transistors with switching ratios of ∠104 and electron mobilities of ∠50 cm2 V−1 s−1 are achieved only after the fabricated structure is thermally annealed. Since some thermal annealing appears to be essential in all of the reported TFT processes, the physical significance of thermal annealing has been investigated. A model involving activated diffusion is presented and the effect of different annealing conditions on transistor characteristics discussed.
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85.30.-z Semiconductor devices
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Epitaxial growth of Si on (1̄012) Al2O3 by partially ionized vapor deposition

S. Shimizu and S. Komiya

J. Vac. Sci. Technol. 17, 489 (1980); http://dx.doi.org/10.1116/1.570491 (3 pages) | Cited 2 times

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The epitaxial growth of silicon on (1̄012) sapphire by partially ionized vapor deposition is investigated with a RHEED–AES system. The measurement of the epitaxial temperature and the observation of the RHEED pattern during epitaxial growth are carried out under varying ionization conditions for the silicon ions; i.e., average ion energy of 30 and 180 eV and fractions of silicon ions mixed with silicon atoms ranging from 0 to 7%. When a silicon molecular beam is deposited without ionization for thickness from 2 to 10 nm, (100) oriented and two different {110} oriented islands are observed in the RHEED pattern at substrate temperatures between 870 and 1020 K. The RHEED pattern, however, shows no change for selective epitaxy when the silicon molecular beam is partially ionized up to 7%. A decrease in epitaxial temperature by as much as 150 K is observed at a fraction of silicon ions of 1%, but no further change is observed at higher fractions up to 7% for ion energies of either 30 eV or 180 eV.
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68.55.-a Thin film structure and morphology
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
68.90.+g Other topics in structure, and nonelectronic properties of surfaces and interfaces; thin films and low-dimensional structures (restricted to new topics in section 68)
68.60.-p Physical properties of thin films, nonelectronic

Geometrical and electronic structure of Si(001) and Si(111) surfaces: A status report

D. E. Eastman

J. Vac. Sci. Technol. 17, 492 (1980); http://dx.doi.org/10.1116/1.570492 (9 pages) | Cited 16 times

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A critical review of recent studies of the geometrical and electronic structure of the Si(001) and Si(111) surfaces is given. Emphasis is placed on low‐energy electron diffraction (LEED) studies of the geometrical structure, photoelectron spectroscopy studies of the electronic structure, and theoretical studies of the electronic and geometric structure of the Si(111)–(2×1), Si(111)–(7×7), Si(111)–(1×1)X, and Si(001)–(2×1) surfaces.
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
73.20.-r Electron states at surfaces and interfaces

Surface atomic geometry of covalently bonded semiconductors: InSb(110) and its comparison with GaAs(110) and ZnTe(110)

C. B. Duke, R. J. Meyer, A. Paton, J. L. Yeh, J. C. Tsang, A. Kahn, and P. Mark

J. Vac. Sci. Technol. 17, 501 (1980); http://dx.doi.org/10.1116/1.570494 (5 pages) | Cited 4 times

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The first determination of the atomic geometry of the (110) surface of InSb is reported. The structure is determined by comparing dynamical calculations of elastic low‐energy electron diffraction (ELEED) intensities with those measured at T=150 K. Initial candidate structures were obtained from an energy‐minimization calculation and from a kinematic analysis of room‐temperature ELEED intensities. Neither candidate proved fully compatible with the measured intensities so another search for the correct structure was performed using dynamical calculations. This procedure yields as the most probable surface structure for InSb(110) one in which the top layer undergoes both a rigid rotation of 28.8° and a 0.05 Å contraction toward the substrate. The Sb atoms move outward and the In atoms inward, giving a relative vertical shear of 0.78 Å in this uppermost layer. In the second layer, the In moves outward 0.09 Å and the Sb inward 0.09 Å. The resulting structure is analogous to that of covalently bonded GaAs(110) but different from that of ZnTe(110) which exhibits a more ionic bonding. We infer that highly covalent zincblende‐structure compound semiconductors exhibit reconstructions of their (110) surfaces characterized by (1) large bond rotations in the uppermost layer, with the anion moving outward and cation inward, (2) small bond‐length alterations (i.e., a few percent or less), and (3) distortions from the bulk geometry which penetrate at least two atomic layers in from the surface.
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73.20.-r Electron states at surfaces and interfaces
79.20.Fv Electron impact: Auger emission
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
81.65.-b Surface treatments

Surface structures of GaAs(110)

Zhang Kai‐Ming and Yeh Ling

J. Vac. Sci. Technol. 17, 506 (1980); http://dx.doi.org/10.1116/1.570495 (3 pages) | Cited 2 times

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The rotational relaxation of the GaAs(110) surface is considered. A cluster model is used fo simulating the crystal surface, and some quasi‐atoms are added in order to saturate the dangling bonds in the cluster boundary. The stable relaxation geometry of the GaAs(110) surface is determined by minimizing the total energy of the cluster calculated by the Extended Hückel Method. According to the calculation, a value of 18° for the tilted angle of the surface bond is suggested which is in fairly good agreement with that given by the partial yield photoelectron spectroscopy. The density of states for the cluster is also calculated, it is shown that for this relaxation model there are no empty cation states existing within the band gap.
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
71.20.-b Electron density of states and band structure of crystalline solids
71.10.-w Theories and models of many-electron systems

Summary Abstract: Intermediate oxidation state of Si(111): Core photoelectron absorption versus chemical shifts

R. S. Bauer and R. Z. Bachrach

J. Vac. Sci. Technol. 17, 509 (1980); http://dx.doi.org/10.1116/1.570496 (2 pages) | Cited 7 times

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Abstract Unavailable
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81.65.-b Surface treatments
73.40.Ns Metal-nonmetal contacts

Bonding of Al and Ga to GaAs(110)

Perry Skeath, I. Lindau, C. Y. Su, P. W. Chye, and W. E. Spicer

J. Vac. Sci. Technol. 17, 511 (1980); http://dx.doi.org/10.1116/1.570497 (6 pages) | Cited 4 times

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The interfacial electronic states associated with Al and Ga overlayers on cleaved GaAs (110) surfaces are studied by ultraviolet photoemission spectroscopy (UPS) and low energy electron diffraction (LEED). Deposition of Al or Ga can produce valence‐band spectra nearly devoid of new structure. Sb produces quite significant changes in the surface valence band and is shown as a contrasting example. Pseudopotential calculations from the literature for Al‐ and Ga‐ordered overlayers are found to be in somewhat better agreement with the data than the corresponding tight‐binding calculations, particularly in the adatom states which lie above the GaAs valence‐band maximum (VBM), although neither calculation gives a good description of the observed overlayer states. It is shown that Al and Ga most likely form two‐dimensional clusters or rafts on the surface at submonolayer coverage which are not in registry with the GaAs surface lattice. A comparison is made with results by other workers for Al, Ga, and In on GaAs and Si.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.61.At Metal and metallic alloys
81.65.-b Surface treatments
73.40.-c Electronic transport in interface structures

Nitridation of silicon (111): Auger and LEED results

J. F. Delord, A. G. Schrott, and S. C. Fain

J. Vac. Sci. Technol. 17, 517 (1980); http://dx.doi.org/10.1116/1.570498 (4 pages) | Cited 9 times

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Clean silicon (111) (7×7) surfaces at up to 1050°C have been reacted with nitrogen ions and neutrals produced by a low energy ion gun. The LEED patterns observed are similar to those previously reported for reaction of silicon (111) (7×7) with NH3. The nitrogen KLL peak exhibits no shift or change in shape with nitride growth. At the same time the magnitude of the elemental silicon LVV peak at 92 eV decreases progressively as a new peak at 84 eV increases. The position of both peaks appears to be independent of the degree of nitridation. Since the Auger spectra are free of oxygen and other impurities, these features can be attributed only to silicon, nitrogen, and their reaction products. Characteristic features of the Auger spectra are related to LEED observations and to the growth of microcrystals of Si3N4.
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79.20.Fv Electron impact: Auger emission
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
73.61.Ng Insulators

Comparative study of wet and dry oxides on polycrystalline GaAs by AES, SIMS, and XPS

L. L. Kazmerski, P. J. Ireland, S. S. Chu, and Y. T. Lee

J. Vac. Sci. Technol. 17, 521 (1980); http://dx.doi.org/10.1116/1.570499 (4 pages) | Cited 1 time

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Complementary Auger electron spectroscopy (AES), secondary ion mass spectroscopy (SIMS), and x‐ray photoelectron spectroscopy (XPS) are used to evaluate low‐temperature wet and dry oxides and the oxide/semiconductor interfaces on polycrystalline GaAs. The dry oxides are found to be primarily Ga2O3 and are relatively uniform in composition. The wet oxides are less uniform and mixed, with a more abrupt transition region that the dry oxide/GaAs interface. XPS data confirm the presence of Ga2O3 in the dry oxide. In comparison, Ga2O3, As2O5 are detected in the wet oxide layer. SIMS shows higher trace impurity concentrations in the wet oxide with some buildup at the oxide/GaAs interface. The relative performance of solar cells fabricated from these structures is discussed.
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81.05.Bx Metals, semimetals, and alloys
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Evidence for grain boundary passivation by oxidation in polycrystalline GaAs solar cells

L. L. Kazmerski and P. J. Ireland

J. Vac. Sci. Technol. 17, 525 (1980); http://dx.doi.org/10.1116/1.570500 (4 pages) | Cited 2 times

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The chemistry and composition of grain boundaries in polycrystalline GaAs grown by liquid phase epitaxy (LPE) and molecular beam epitaxy (MBE) are examined using complementary Auger electron spectroscopy (AES), secondary ion mass spectroscopy (SIMS) and x‐ray photoelectron spectroscopy (XPS). The effects of an unintentional residual‐oxygen partial pressure during LPE growth are investigated in terms of grain boundary passivation. Depth‐compositional data verify the grain boundary localization of oxides using an in situ, UHV fracturing technique. Indications of distributions of these oxides over the grain boundary are presented. The performances of Au Schottky barrier solar cells fabricated from the polycrystalline LPE and MBE GaAs are compared and differences are explained in terms of grain boundary activity.
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84.60.Jt Photoelectric conversion
81.65.-b Surface treatments
61.72.Mm Grain and twin boundaries

Phosphosilicate glass flow for integrated optics

A. Naumaan and J. T. Boyd

J. Vac. Sci. Technol. 17, 529 (1980); http://dx.doi.org/10.1116/1.570501 (4 pages) | Cited 1 time

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We have carried out an investigation of the use of phosphosilicate glass (PSG) flow for integrated optical circuits. PSG layers of thicknesses ranging from 4 to 22 μm were chemically vapor deposited on V‐grooves in silicon substrates having a depth of 175 μm. The effect on the flow of (1) P2O5 concentration in PSG layers (5–10 mol %), (2) ambient during flow (dry O2, wet O2, POCl3, and wet N2), (3) temperature (1000°–1200°C) and (4) time (30–120 min) of the process has been determined. The extent of flow, as measured by curvature of the rounded corners, has been plotted against PSG layer thickness and reflow time. Radii of curvature up to 36 μm through 70° bends have been measured.
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42.82.-m Integrated optics
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

X‐ray lithography — A review and assessment of future applications

Henry I. Smith and D. C. Flanders

J. Vac. Sci. Technol. 17, 533 (1980); http://dx.doi.org/10.1116/1.570502 (3 pages) | Cited 6 times

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The radiation used in x‐ray lithography spans a rather broad range, from about 4 to 50 Å. At the short wavelength end, transmission through mask membranes and vacuum windows is high, and minimum linewidth is of the order of 1/2 μm. At the long wavelength end, mask selection is limited, exposure is done in vacuum and minimum linewidth is about 100 Å. At intermediate wavelengths, one can make numerous tradeoffs among resolution, system configuration, masks and resists. X‐ray lithography at the AlK wavelength (8.34 Å) is compared with scanning electron beam lithography from the point of view of exposure time, assuming a step‐and‐repeat strategy. The use of gap adjustment to compensate for homogeneous substrate distortion may be an important advantage of x‐ray lithography relative to other parallel exposure techniques.
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07.68.+m Photography, photographic instruments; xerography
07.85.-m X- and γ-ray instruments
41.75.Fr Electron and positron beams
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