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Oct 1984

Volume 2, Issue 4, pp. 1443-1613


A model for atomic mixing and preferential sputtering effects in SIMS depth profiling

B. V. King and I. S. T. Tsong

J. Vac. Sci. Technol. A 2, 1443 (1984); http://dx.doi.org/10.1116/1.572380 (5 pages) | Cited 13 times

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The development of altered surface layers due to preferential sputtering can be modeled by an algorithm based on the diffusion theory of atomic mixing using a depth‐dependent diffusion coefficient. Application of the model to typical SIMS depth profiles of buried layers indicates that the effects of atomic mixing and preferential sputtering can be separated by analysis of the shift and broadening of the measured peaks.
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64.75.-g Phase equilibria
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
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)
66.30.J- Diffusion of impurities

Effects of gaseous oxygen on SIMS analysis of oxygen‐isotopes in metal oxides

Kazunori Sato, Yasunobu Inoue, Masaaki Ohno, and Mayumi Someno

J. Vac. Sci. Technol. A 2, 1448 (1984); http://dx.doi.org/10.1116/1.572381 (5 pages)

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The influence of an O2 atmosphere on oxygen‐isotope analysis by means of secondary ion mass spectrometry (SIMS) was studied in detail using various standard metal oxides enriched with a stable isotope18O. The secondary ion intensities of 16O− and 18O− were examined under different 16O‐oxygen pressures and primary Ar+ beam currents. The deviation in the isotope ratio became prominent at an oxygen pressure over about 1×10−4 Pa, and in the sequence of CuO<ZnO<NiO, Co3O4<Cr2O3<TiO2. A decrease in beam current resulted in the enhancement of this oxygen effect. When pure metals such as Cu, Zn, Ni, Co, Cr, and Ti were sputtered in an 16O2 atmosphere, the secondary ion intensities of 16O− changed with oxygen pressures in a similar way to those of 16O− emitted from 18O‐oxides consisting of the corresponding metal atoms. It was shown that the oxygen effects among the oxides are closely related to the bonding strength between metal and oxygen atoms; the stronger interaction being responsible for the larger oxygen effects.
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82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
07.75.+h Mass spectrometers
82.20.Tr Kinetic isotope effects including muonium
33.15.Fm Bond strengths, dissociation energies

Ratioed scatter diagrams. An erotetic method for phase identification on complex surfaces using scanning Auger microscopy

R. Browning

J. Vac. Sci. Technol. A 2, 1453 (1984); http://dx.doi.org/10.1116/1.572382 (4 pages) | Cited 1 time

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By ratioing multiple Auger intensities and plotting a two‐dimensional occupational scatter diagram while digitally scanning across an area, the number and elemental association of surface phases can be determined. This can prove a useful tool in scanning Auger microscopic analysis of complex materials. The technique is illustrated by results from an anomalous region on the reaction zone of a SiC/Ti–6A1–4V metal matrix composite material. The anomalous region is shown to be a single phase associated with sulphur and phosphorus impurities. Imaging of a selected phase from the ratioed scatter diagram is possible and may be a useful technique for presenting multiple scanning Auger images.
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82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics

Effects of oxygen in ion‐beam sputter deposition of titanium oxides

H. Demiryont and J. R. Sites

J. Vac. Sci. Technol. A 2, 1457 (1984); http://dx.doi.org/10.1116/1.572383 (4 pages) | Cited 12 times

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Oxides of titanium, 200–400 nm thick, were deposited by ion‐beam sputtering of a metallic target. The ion beam consisted of an argon–oxygen mixture where the oxygen percentage was varied from 5% to 50%. Ellipsometry and spectrophotometry were used for optical characterization, x‐ray photoelectron spectroscopy to examine the atomic bonding patterns. For each wavelength, the refractive index showed a maximum when the oxygen fraction was near 30%. At 633 nm, the maximum was 2.52. Such films were dense, amorphous, stoichiometric TiO2 with a visible optical absorption of a few tenths of a percent. With less oxygen, films were also transparent, but contained increasing amounts of a titanium suboxide. With substantially less oxygen, opaque cermets were formed. When the oxygen percentage was increased above 40%, the refractive index of the films was less than the maximum, the films apparently contained voids, but they were otherwise stoichiometric.
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68.60.-p Physical properties of thin films, nonelectronic
81.15.Cd Deposition by sputtering
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
75.20.Ck Nonmetals

Initial stages of oxidation of the Pt3Ti(111) and (100) single crystal surfaces

U. Bardi and P. N. Ross

J. Vac. Sci. Technol. A 2, 1461 (1984); http://dx.doi.org/10.1116/1.572384 (10 pages) | Cited 6 times

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The process of segregation of titanium oxides onto the surface of Pt3Ti upon the exposure to oxygen at different pressures and temperatures was studied by LEED and AES. Oriented [111] and [100] monocrystals as well as polycrystals were synthesized for study. Qualitatively similar behavior was observed with all three types of surfaces, with three stages of oxidation observed on each surface. A layer of stoichiometry close to TiO segregated onto the surface in the initial stage of oxidation, depleting the subsurface region of the alloy in Ti. The TiO formed a compact, epitaxial monolayer which completely blocked the metallic surface for chemisorption by carbon monoxide. Further oxidation caused formation of a multilayer of TiO1.2, an oxide with an orthorhombic structure derived from TiO by removing Ti atoms to form an ordered vacancy lattice. Finally, oxidation at the relatively extreme conditions of atmosphere pressure at high (>1000 K) temperature caused formation of thick TiO2 (rutile) overlayers.
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81.05.Bx Metals, semimetals, and alloys
64.75.-g Phase equilibria
66.30.J- Diffusion of impurities

Electron microscope study of very thin mixed Cu/CuO films

L. Paoletti, P. A. Rosa, P. Picozzi, and S. Santucci

J. Vac. Sci. Technol. A 2, 1471 (1984); http://dx.doi.org/10.1116/1.572385 (4 pages) | Cited 1 time

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The oxidation kinetics and morphology of very thin (<10 nm) mixed Cu/CuO films obtained by exposing very thin discontinuous Cu films to atomic oxygen plasma were investigated by electron diffraction and dark field electron microscopy. The oxidation process is characterized by an initial stage of oxide logarithmic growth which goes on until about 50% of the initial Cu is oxidized. The morphology of the films during the oxidation evolves from a situation characterized by discontinuous metallic islands covered with an oxide layer to another one in which metallic grains are embedded in a continuous oxide film.
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81.05.Bx Metals, semimetals, and alloys
68.55.-a Thin film structure and morphology
68.60.-p Physical properties of thin films, nonelectronic

Paramagnetic centers at vacuum crushed annealed silicon on exposure to oxygen and parabenzoquinone

M. F. Chung and D. Haneman

J. Vac. Sci. Technol. A 2, 1475 (1984); http://dx.doi.org/10.1116/1.572386 (6 pages) | Cited 1 time

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When silicon is crushed in ultrahigh vacuum (UHV) the well known electron paramagnetic resonances signal called A, at g=2.0055, and width 5–7 G is produced. Upon annealing to above the 700 °C regions, A is gradually replaced by A1, a new signal at g=2.0020 with width about 10 G and height about 1% of A. Heating above 900 °C destroys A1 and all subsequent gas effects. Exposure of silicon with A1 to oxygen or parabenzoquinone (PBQ), causes A1 to increase and the appearance of a new sharp signal C at g=2.0024 and width about 2 G. However in the case of oxygen only, another new signal called E, at g=2.0000, and width about 1 G, appears on pumping out the oxygen. This is reversible. The behavior under variations of gas exposure and of microwave power indicated that the signals are all associated with cracks and fissures, and that C is probably due to ‘‘free’’ electrons along lines of O2 or PBQ at fissure ends. The similarity of A with the EPR signal from amorphous hydrogenated silicon is now ascribed to A resulting from classical dangling bonds at the ends of fissures where the strain prevents surface reconstructions on the crack surfaces.
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76.30.-v Electron paramagnetic resonance and relaxation
81.40.Rs Electrical and magnetic properties related to treatment conditions
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

The segregation of impurities at the (110) surface of an Fe–10 at. % single crystal

F. Bezuidenhout, J. du Plessis, and P. E. Viljoen

J. Vac. Sci. Technol. A 2, 1481 (1984); http://dx.doi.org/10.1116/1.572387 (5 pages) | Cited 4 times

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Measurement of the nonequilibrium surface concentration in a Fe–10 at. % Si (110) sample as an function of temperature reveals specific interrelated segregation behavior. A review of the initial processes in this single crystal shows the existence of certain interactions. In agreement with work on the other ternary systems, evidence has been found that carbon and silicon show a repulsive interaction in the segregation process. At lower temperatures the surface free energy favors the carbon and above a transition temperature, the silicon on the surface. On the other hand, silicon and phosphorus cosegregate, which is indicative of an attractive interaction. This has the effect that much less phosphorus is available for segregation to the surface or grain boundaries than in a pure Fe–P system. The LEED pattern for the silicon covered surface is the same as for a 1% Si sample viz. a c(7×1) superstructure with reference to the c(a×(2a)1/2) surface net, where a is the unit cell parameter in the [001] direction. Elongation of the spot in one direction indicates a change of order in the [001] direction in agreement with the silicon island formation. The pattern of the phosphorus covered surface shows a maximum surface coverage by phosphorus in good agreement with the observed value as determined by AES.
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61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients
64.75.-g Phase equilibria
66.30.J- Diffusion of impurities
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)

Negative resistance switching in near‐perfect crystalline silicon film resistors

P. Kenyon and H. Dressel

J. Vac. Sci. Technol. A 2, 1486 (1984); http://dx.doi.org/10.1116/1.572388 (5 pages)

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This paper describes negative resistance switching in n‐type silicon film resistors which contain linear arrays of grain boundaries. These linear arrays have been predictably located in the active region by a laser recrystallization procedure. The grain boundaries are made to bisect the resistors. Effects of parameters such as grain boundary number and grain‐dopant concentration have been examined. We show that quasisaturated and asymmetrical I–V characteristics are exhibited by our resistors. This is evidence that the voltages across the depletion region and across the grain boundary layer are not equally divided on each side of the junction, and that dopants are nonuniformly incorporated in the grains during laser recrystallization.
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84.32.Ff Conductors, resistors (including thermistors, varistors, and photoresistors)
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
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Electrical transport properties of polycrystalline rf sputtered CdS thin films

I. Mártil, G. González‐Díaz, and F. Sánchez‐Quesada

J. Vac. Sci. Technol. A 2, 1491 (1984); http://dx.doi.org/10.1116/1.572389 (4 pages) | Cited 8 times

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Temperature dependence, in the range 150–450 K, of the resistivity and Hall mobility were studied on polycrystalline sputtered CdS thin films. The room‐temperature values of analyzed samples for resistivities and Hall mobilities ranged between 1–108 Ω cm and 2–8 cm2/V s. The results showed a major scattering mechanism controlled by the intergrain barrier height, the carriers being thermally activated. A temperature dependence of the barrier height ϕB=ϕ0 (1+αT) has been observed which allows fitting a general expression for Hall mobility of the form μH=11.6 exp(26.8 ϕ0) exp(−ϕ0/kT). A theoretical calculation of the μ0 parameter has been performed. The results show good agreement with the experimental data.
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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

Explosive recrystallization during pulsed laser irradiation

J. Narayan, S. J. Pennycook, D. Fathy, and O. W. Holland

J. Vac. Sci. Technol. A 2, 1495 (1984); http://dx.doi.org/10.1116/1.572390 (3 pages) | Cited 8 times

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The phenomenon of explosive recrystallization has been studied in Si+ and Cu+ implanted amorphous silicon layers by electron microscopy and Rutherford backscattering techniques (RBS). Cross‐section and plan‐view electron microscopy techniques (TEM) have been used to obtain a detailed characterization of microstructures associated with the explosive mode of recrystallization. RBS and analytical TEM studies on segregation of copper provided information on the mechanism of explosive recrystallization involving a thin liquid film interposed between crystallized and uncrystallized regions.
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81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
79.20.Ds Laser-beam impact phenomena
64.75.-g Phase equilibria
81.30.-t Phase diagrams and microstructures developed by solidification and solid-solid phase transformations

Adhesion of evaporated titanium to polyethylene: Effects of ion bombardment pretreatment

P. Bodö and J.‐E. Sundgren

J. Vac. Sci. Technol. A 2, 1498 (1984); http://dx.doi.org/10.1116/1.572460 (5 pages) | Cited 3 times

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Titanium films, 1 μm thick were electron‐beam evaporated onto polyethylene (PE) that had been pretreated in situ by 2 keV Ar+ bombardment. A measure of the film adhesion was obtained by measuring the pull strength required to remove the Ti films. A strong dependence of the adhesion on the ion dose was found. The pull strength had a maximum of approximately 20 MPa after a dose of 6×1014 ions/cm2 but decreased for higher ion doses. Without any ion bombardment prior to deposition, the adhesion was very poor with a pull strength of approximately 2 MPa. XPS analysis was used to examine the effect of the ion bombardment on the chemistry of the PE substrate and the Ti/PE interface. Untreated PE samples were contaminated with surface impurities and probably also with low molecular weight hydrocarbons. As the adhesion is maximized, most of the impurities are removed by the ion bombardment. The strong adhesion is suggested to be due to formation of a carbidelike Ti–C interfacial layer, detected by XPS.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.65.-b Surface treatments
46.55.+d Tribology and mechanical contacts
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Wetting of metal surfaces with a liquid metal using a plasma interaction technique

T. S. Sudarshan, M. H. Lim, L. Park, and S. H. Chang

J. Vac. Sci. Technol. A 2, 1503 (1984); http://dx.doi.org/10.1116/1.572461 (6 pages)

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Materials such as tungsten, molybdenum, stainless steel, etc., which have low solubility in mercury (Hg) are difficult to be wetted or coated with the liquid metal. This paper describes a general technique for wetting and coating such metals with Hg. The method involves plasma etching the substrate and making the liquid metal interact with the plasma before it contacts the substrate surface, by delivering it to the substrate through the glow discharge, to successfully wet the above metals. Elkonite (70% W and 30% Cu) was also wetted successfully by this technique. A model has been presented to qualitatively explain the observed results. The discharge is postulated to create reactive species on the substrate surface and to produce reactive Hg species as Hg travels through the plasma. Further, the surface free energies of the substrate and the liquid metal are altered suitably to favor wetting and surface complexing as described by Young’s equation.
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81.05.Bx Metals, semimetals, and alloys
64.75.-g Phase equilibria
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

Modifications in the phase transition properties of predeposited VO2 films

F. Cardillo Case

J. Vac. Sci. Technol. A 2, 1509 (1984); http://dx.doi.org/10.1116/1.572462 (4 pages) | Cited 24 times

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Thin films of the phase transition material vanadium dioxide (VO2) were deposited by thermal oxidation of e‐beam evaporated vanadium on a variety of bulk materials. Substrate effects on transition temperature are confirmed as being due to a mismatch between film and substrate thermal expansion coefficients. Decreasing tensile stress results in a lowering of VO2 transition temperature. Effects of low‐energy Ar+ bombardment on the electrical and optical properties of these predeposited VO2 films were investigated. Bombardment energies in the range 138–500 eV at 1.0–1.3 mA/cm2 for 120–180 s were provided by a Commonwealth Millatron. The higher Ar+ energies resulted in collapse of the VO2 optical transmittance hysteresis loop, while low‐energy Ar+ ions caused both a downward shift in the transition temperature and a decrease in hysteresis loop width, suggesting a dependence of these quantities on intrinsic stress. In addition, large decreases in cold‐state resistivity are reported and attributed to a reduction of the surface oxide by the low energy argon beam.
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61.80.Fe Electron and positron radiation effects
81.40.Tv Optical and dielectric properties related to treatment conditions
81.40.Rs Electrical and magnetic properties related to treatment conditions
68.60.-p Physical properties of thin films, nonelectronic

Gain degradation mechanism for channel electron multipliers

M. Lichtensteiger and C. Webb

J. Vac. Sci. Technol. A 2, 1513 (1984); http://dx.doi.org/10.1116/1.572463 (3 pages) | Cited 1 time

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The gain of channel electron multipliers (CEM) decreases rapidly during experiments which involve exposure of samples to ∼10−8 Torr H2O during electron bombardment—an environment which very effectively oxidizes semiconductors. In subsequent experiments it was found that reoxidation of samples of CEM glass (it is subject to reduction treatment during manufacture) occurs when it is exposed to the same set of conditions. We discuss the possible influence of this on the gain degradation commonly observed as a function of total counts.
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84.47.+w Vacuum tubes
81.40.Rs Electrical and magnetic properties related to treatment conditions

A residual gas analyzer compatible with reactive and radioactive gases

J. von Seggern, S. Berger, M. Erdweg, and W. O. Hofer

J. Vac. Sci. Technol. A 2, 1516 (1984); http://dx.doi.org/10.1116/1.572464 (5 pages)

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A conventional residual gas analyzer was equipped with an ion‐electron converter as particle detector and tested in tritium‐containing environments. Substantial advantages can be asserted for this setup: high dynamic range, easy regenerability by baking without detrimental effects on the multiplier, insensitivity to exposure to reactive gases, and inexpensive replacement.
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07.30.Kf Vacuum chambers, auxiliary apparatus, and materials
07.75.+h Mass spectrometers
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Cleaning and conditioning of the walls of plasma devices by glow discharges in hydrogen

F. Waelbroeck, J. Winter, and P. Wienhold

J. Vac. Sci. Technol. A 2, 1521 (1984); http://dx.doi.org/10.1116/1.572465 (16 pages) | Cited 2 times

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Surface conditioning by rf‐assisted dc glow (RG) discharges has been studied in a stainless steel vessel in order to optimize the rate of surface deoxidization via water formation. This is the simplest way to decontaminate the almost carbon‐free surfaces of plasma devices which have been exposed to air after a prolonged operation in hydrogen. This rate depends strongly on the wall temperature TW, the pump speed Sp, the discharge current IRG, and the hydrogen pressure P2. It is small at ambient temperature; the conditioning should be made at TW>100 °C. Surface oxygen is removed, even at room temperature, when 1% to 2% of methane is added to the hydrogen. Carbon monoxide is formed and evacuated. The addition of He or Ne does not accelerate the oxygen removal from reoxidized surfaces. An equation derived from a simplified model describes the parametric dependences of the water release well. The occurrence of arcs during RG discharges depends on wall conditioning; they are not observed after a prolonged bakeout at 200 °C. The problems which arise when a residual gas analyzer is used to measure the partial pressures of water, carbon oxides, and hydrocarbons in hydrogen are addressed, and a conditioning technique which reduces the resulting errors is described.
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81.05.Bx Metals, semimetals, and alloys
52.75.-d Plasma devices
07.30.Bx Degasification, residual gas

Relation between the RF discharge parameters and plasma etch rates, selectivity, and anisotropy

C. B. Zarowin

J. Vac. Sci. Technol. A 2, 1537 (1984); http://dx.doi.org/10.1116/1.572466 (13 pages) | Cited 16 times

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By extending earlier ideas and introducing new ones in this paper, we relate observable rf discharge parameters to the plasma etch characteristics of rate, selectivity, and anisotropy. The ion energy transport ‘‘ellipsoid’’ generated by the electric field across the plasma sheath is shown to induce anisotropic etch reactions and, under certain circumstances, to ‘‘enhance’’ the intrinsic chemical etch selectivity. The plasma sheath electric field is shown to be determined by observable rf discharge parameters. The rf discharge is reduced to an equivalent circuit, which relates the time averaged plasma body and sheath electric fields to the rf discharge parameters of plasma geometry, current or power and discharge excitation frequency. We find two regimes of excitation frequency, for otherwise identical conditions, generating much larger sheath electric fields below than above the ion plasma frequency (∼1 MHz). Fixing the plasma geometry and etch gas chemical composition is identified as central to obtaining simply behaved and reproducible etch characteristics. At comparable etch anisotropy, the only practical distinction between the etch characteristics of ‘‘high’’ pressure ‘‘plasma etching’’ and ‘‘low’’ pressure ‘‘reactive ion etching,’’ is that the former is capable of significantly higher etch rates and selectivities than the latter.
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52.75.-d Plasma devices
81.65.-b Surface treatments
52.80.-s Electric discharges

Target erosion and deposition rates in planar magnetron sputtering

M. Gurvitch

J. Vac. Sci. Technol. A 2, 1550 (1984); http://dx.doi.org/10.1116/1.572467 (2 pages) | Cited 4 times

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Erosion grooves are known to develop on a surface of a planar magnetron sputtering target in the course of its use, causing the rate of deposition per unit power applied to the target (rate efficiency) to decrease with progressing erosion. It is shown that for a given target material there is a reproducible empirical correspondence between the rate efficiency and the groove depth. Once established, this correspondence offers a simple way for estimating thicknesses of the films deposited onto stationary and rotating substrates.
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81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology

A pattern edge profile simulation for oblique ion milling

Noriyoshi Yamauchi, Toshiaki Yachi, and Tsutomu Wada

J. Vac. Sci. Technol. A 2, 1552 (1984); http://dx.doi.org/10.1116/1.572468 (6 pages) | Cited 3 times

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An oblique ion milling simulation method is proposed in which etching and redeposition at the pattern side wall are taken into account. The effective etching rate at the pattern side wall is determined as the difference between the etching rate given by the angular dependency and the redeposition rate. The redeposition rate is assumed to be proportional to the etching rate of the material to be etched at the flat surface. A pattern edge profile simulation is carried out for an oblique ion milling of silicon. The simulation results agreed well with the experimental results with a relatively large ion beam incident angle.
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81.65.-b Surface treatments
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Evaporative coating of a sphere from a point source

D. M. Strayer, H. W. Jackson, and J. R. Gatewood

J. Vac. Sci. Technol. A 2, 1558 (1984); http://dx.doi.org/10.1116/1.572469 (9 pages) | Cited 1 time

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To optimize the procedure for evaporating a metal film onto a sphere, calculations of the film thickness distribution for various motions of the sphere have been carried out. These calculations, including shadowing effects of sphere support rods, are presented in this paper. Also, an apparatus and procedure for the evaporative coating of a sphere are described. A comparison of measured thickness with the calculated values is made for one example of sphere motion. The implications of the calculated results for coating techniques are discussed.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.60.-p Physical properties of thin films, nonelectronic

Pulsed series discharges in crossed fields generated in vacuum switches for pressure‐measurement application

Katsuhiro Kageyama

J. Vac. Sci. Technol. A 2, 1567 (1984); http://dx.doi.org/10.1116/1.572470 (9 pages) | Cited 1 time

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Formative processes of the series crossed‐field discharges in vacuum switches were investigated, and pulsed discharges were found feasible for switch‐pressure measurement, when solid surfaces within switches are clean. The fact that a vacuum switch is a small, sealed device, causes problems in switch‐pressure measurement, to which serious conditions for performance are charged. To solve the problems, pulsed discharges were investigated. The discharge in a switch, identified previously as a series discharge consisting of an inverted magnetron and a magnetron, was generated by rectangular high voltage at amplitude Vd. Discharge currents in formative phases were measured and analyzed. Formative processes were revealed to be composed of triggering and growth. At a large Vd value, the discharges are triggered immediately after the stepped voltage application. Instantaneous discharge triggering assures high reliability in pressure measurement. At small Vd values, times required for triggering are delayed and scattered. In the growth phase, discharge currents proceed to increase in a reproducible pattern, and become saturated. Then they begin to decrease, resulting from pressure decreases due to the pumping effect of discharges. A current increase in the growth phase is always quick, and a decrease after saturation is slow. Magnitudes of the saturation currents are distributed concentratedly. This causes good precision in measurement, typically with errors less than 10% of the measured values. The time intervals necessary to establish the pulsed discharges and the pumping effect to change pressures were analyzed. The measurement range was found to cover a low pressure, down to 1×10−4 Pa, with a pressure decrease of less than 20%, when pumping speed is 4.2 l/s, which is the maximum experimental value. Thus, pulsed series crossed‐field discharges were found to be feasible for switch‐pressure measurements, when switch interior surfaces are clean.
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52.80.Vp Discharge in vacuum
84.32.Dd Connectors, relays, and switches
52.80.Sm Magnetoactive discharges (e.g., Penning discharges)
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials

Gas pressure in the end plug regions of the TMX‐U thermal barrier experiment

W. C. Turner, W. E. Nexsen, S. L. Allen, E. B. Hooper, A. L. Hunt, D. D. Lang, D. S. Margolies, W. L. Pickles, and T. C. Simonen

J. Vac. Sci. Technol. A 2, 1576 (1984); http://dx.doi.org/10.1116/1.572471 (7 pages) | Cited 1 time

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We consider briefly the upper bound on background pressure (0.5 to 1.0×10−6 Torr) that is required for operation of the thermal barrier end plugs of TMX‐U and propose a rate equation for pressure buildup that includes terms for neutral beam injection and wall reflux. During early operation of TMX‐U the background pressure exceeded this upper bound; in addition, axial end plugging of plasma losses seemed limited by the excessive pressure. Modifications to the vacuum system to decrease this pressure to the desired range are described. Furthermore, wall reflux is shown to depend linearly on pressure. We conclude with an example of the dramatic increase in time duration of axial plugging of plasma losses with the reduced background pressure.
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52.55.Jd Magnetic mirrors, gas dynamic traps
07.30.Bx Degasification, residual gas
52.40.Hf Plasma-material interactions; boundary layer effects

Performance of Zr–Al getter pumps under transient load conditions

L. C. Emerson, P. K. Mioduszewski, and J. E. Simpkins

J. Vac. Sci. Technol. A 2, 1583 (1984); http://dx.doi.org/10.1116/1.572472 (6 pages)

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Testing of the pump limiter concept in the Impurity Study Experiment (ISX‐B) tokamak will involve the use of Zr–Al nonevaporable getter pumps capable of handling intermittent pulses of hydrogen and/or deuterium in the presence of carbon and oxygen impurity concentrations of several percent. To study the pumping characteristics under these conditions we have installed a Zr–Al cartridge pump in a vacuum chamber equipped with a fast gas puff feed system, a quadrupole residual gas analyzer, and a high speed ion gauge for transient pressure measurements. In this paper we report on the performance of the pump over a wide range of gas loads up to that sufficient to provide tens of monolayers of coverage of the getter surface. With flow rates up to 13 Torr l/s, pumping speeds for hydrogen were measured to be 1200–1500 l/s at pressures up to 10 mTorr. The measurements were carried out with gas pulses ranging in length from 50 ms to over 1 s and under conditions that provided a constant pumping speed for impurity species.
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07.30.Cy Vacuum pumps
52.55.Fa Tokamaks, spherical tokamaks
52.55.Hc Stellarators, torsatrons, heliacs, bumpy tori, and other toroidal confinement devices
07.30.Bx Degasification, residual gas

A new helium sniffing device for locating very fine leaks

Y. Murakami, Y. Shimomura, T. Abe, and K. Obara

J. Vac. Sci. Technol. A 2, 1589 (1984); http://dx.doi.org/10.1116/1.572473 (4 pages) | Cited 1 time

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A new helium sniffing method for leak checking large vacuum vessels is described. The low sensitivity problem of the conventional helium sniffing method has been overcome by increasing the gas draw rate from around leaks into the detector up to about 0.1 Pa m3/s. The devised system consists of a flexible stainless steel capillary tube 0.6 mm i.d. and 10 m long, a sorption pump using molecular sieve, and a helium leak detector in series. This method is particularly useful for locating very fine leaks down to 10−11 Pa m3/s. Relevant theoretical considerations and experimental results are presented.
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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

Spectroscopic characterization of fluorinated silicon single crystal surfaces

N. D. Shinn, J. F. Morar, and F. R. McFeely

J. Vac. Sci. Technol. A 2, 1593 (1984); http://dx.doi.org/10.1116/1.572474 (2 pages) | Cited 9 times

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Spectroscopic studies of Si(100) fluorinated by the dissociative chemisorption of XeF2 at 80 K are reported. LEED and XPS measurements suggest the formation of a disordered fluorosilyl layer after low fluorine doses. Separate EELS experiments identified a fluorine induced 800 cm−1 loss, suggesting that SiF is the major surface fluorosilyl species. Vibrational evidence for coadsorbed hydrogen, due to side reactions during fluorination, is also found. Recent synchrotron soft x‐ray photoemission spectra support the SiF identification and also demonstrate dramatic crystallographic effects in comparative Si(111) studies.
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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
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Fluorine detection sensitivity in electron stimulated desorption

Mario de Moraes and David Lichtman

J. Vac. Sci. Technol. A 2, 1595 (1984); http://dx.doi.org/10.1116/1.572475 (2 pages) | Cited 2 times

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82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics

In situ cleaning of nickel field‐ion surfaces by neon ion bombardment

G. L. Kellogg

J. Vac. Sci. Technol. A 2, 1597 (1984); http://dx.doi.org/10.1116/1.572476 (2 pages) | Cited 2 times

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Neon ion bombardment followed by field evaporation is shown to be a simple, effective procedure for cleaning the surface of nickel field‐ion samples. The neon ions are generated by reversing the tip polarity and establishing a field emission current in the presence of the neon imaging gas. The procedure removes surface impurities which are resistant to field desorption at the evaporation field of nickel. The experimental conditions required to clean a nickel surface are presented.
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81.05.Bx Metals, semimetals, and alloys
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

The operation of a capacitance manometer at 300 °C

S. J. Buckman, J. Gascoigne, and K. B. Roberts

J. Vac. Sci. Technol. A 2, 1599 (1984); http://dx.doi.org/10.1116/1.572477 (2 pages)

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The performance of a capacitance manometer operated at 300 °C is described. Calibration against a deadweight primary pressure standard indicates that the stability over a period of 3 months is better than 0.25% of the measured pressure over the pressure range 15–1000 Torr (2.04–131.6 kPa).
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07.30.Dz Vacuum gauges

Design of chromel–alumel thermocouple gauges

Celso M. Aldao and Daniel G. Löffler

J. Vac. Sci. Technol. A 2, 1601 (1984); http://dx.doi.org/10.1116/1.572478 (2 pages) | Cited 1 time

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The operation principle of thermocouple gauges is well known [Ref. 1: D. R. Denison, Methods of Experimental Physics, (Academic, New York, 1979)] but values of the physical parameters needed for the design of these instruments are not readily available in the literature. We have measured the electrical resistivity, thermal conductivity, and emissivity for chromel and alumel wires as functions of temperature. These functions can be used to design thermocouple gauges presenting maximum sensitivity in a particular pressure range or to modify the sensitivity of commercial instruments for a specific application.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.20.Dt Thermometers

The use of sliding metal electrical contacts in UHV

S. M. Newstead, R. A. A. Kubiak, and E. H. C. Parker

J. Vac. Sci. Technol. A 2, 1603 (1984); http://dx.doi.org/10.1116/1.572479 (1 page)

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A simple and versatile method of contacting to sliding stainless steel rods is described. Compact linear motions are made possible, in which the supports of a component also act as electrical feeds. Problems associated with insulated flexible connectors are thus eliminated. The contacts have worked reliably in a III–V MBE system environment.
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07.30.Kf Vacuum chambers, auxiliary apparatus, and materials
73.40.Ns Metal-nonmetal contacts
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

A UHV compatible and miniaturized evaporator used as a controlled source of high melting point metal vapor

B. Bellamy and C. Colomer

J. Vac. Sci. Technol. A 2, 1604 (1984); http://dx.doi.org/10.1116/1.572480 (3 pages) | Cited 4 times

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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
07.30.Hd Vacuum testing methods; leak detectors
06.60.Ei Sample preparation (including design of sample holders)

A simple bearing for horizontal rotation of heavy equipment in UHV

W. Stocker and K. H. Rieder

J. Vac. Sci. Technol. A 2, 1606 (1984); http://dx.doi.org/10.1116/1.572481 (1 page)

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Three metal carbide spheres located approximately equidistant on a support with a V‐shaped circular groove allow easy horizontal rotation of a heavy mass in UHV via a turntable residing on the three spheres with vertical axis in the center of the support.
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06.60.Vz Workshop procedures (welding, machining, lubrication, bearings, etc.)

Modulated electron beam

R. A. Anderson

J. Vac. Sci. Technol. A 2, 1607 (1984); http://dx.doi.org/10.1116/1.572432 (1 page)

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An easily installed modification to an electron gun power supply allows the electron beam to be modulated with an externally applied, audio‐frequency signal. Full on–off chopping is accomplished with an input amplitude of only 10 V rms. The modification does not interfere with normal operation of the electron gun.
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41.75.Fr Electron and positron beams
07.77.-n Atomic, molecular, and charged-particle sources and detectors
84.30.Jc Power electronics; power supply circuits
07.50.Ek Circuits and circuit components

A low‐cost cryogenic temperature controller for a VG ESCALAB V system

D. Shuttleworth and F. L. Simmonds

J. Vac. Sci. Technol. A 2, 1608 (1984); http://dx.doi.org/10.1116/1.572433 (2 pages)

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A modification to a VG temperature controller is described which allows for the control of subambient temperatures of sample manipulators used in ESCALAB instruments. The system developed provides stable temperature control over several hours.
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07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials

Book Review: A history of engineering and science in the Bell System: Physical science (1925–1980)

R. M. White

J. Vac. Sci. Technol. A 2, 1610 (1984); http://dx.doi.org/10.1116/1.572434 (1 page)

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01.30.Ee Monographs and collections
01.65.+g History of science
89.20.Bb Industrial and technological research and development

Book Review: The LMTO method—Muffin tin orbitals and electronic structure

W. A. Harrison

J. Vac. Sci. Technol. A 2, 1610 (1984); http://dx.doi.org/10.1116/1.572435 (3 pages)

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01.30.mm Textbooks for graduates and researchers
71.15.-m Methods of electronic structure calculations

Erratum: Use of discharge intensity for evaluation of pumping characteristics of a sputter ion pump [J. Vac. Sci. Technol. A 2, 195 (1984)]

M. Pierini

J. Vac. Sci. Technol. A 2, 1613 (1984); http://dx.doi.org/10.1116/1.572436 (1 page)

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Abstract Unavailable
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07.30.Cy Vacuum pumps
99.10.Cd Errata
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