JVA Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

Sep 1988

Volume 6, Issue 5, pp. 2853-3019


The National Bureau of Standards primary high‐vacuum standard

C. R. Tilford, S. Dittmann, and K. E. McCulloh

J. Vac. Sci. Technol. A 6, 2853 (1988); http://dx.doi.org/10.1116/1.575612 (7 pages) | Cited 9 times

Full Text: | Download PDF

Show Abstract
The theory, design, operating procedures, and estimated errors are discussed for an orifice‐flow‐type pressure standard currently in use at the National Bureau of Standards. This standard is used to define pressures between 10−7 and 10−1 Pa. Including the uncertainty of the flowmeter, the estimated total uncertainty varies from 2.6% at the highest pressures, to 1.4% at midrange, and 8.2% at the lowest pressures. Representative calibration results are presented for four different types of hot‐cathode ionization gauges.
Show PACS
07.30.Dz Vacuum gauges
07.30.Hd Vacuum testing methods; leak detectors

Automated system for measuring leak standards

John M. Ball

J. Vac. Sci. Technol. A 6, 2860 (1988); http://dx.doi.org/10.1116/1.575613 (5 pages)

Full Text: | Download PDF

Show Abstract
An inexpensive, automatic measurement system for standard leaks has been developed and tested. The principal of operation is pressure rise in a measurement chamber held at a low pressure. This design minimizes temperature effects, considerably improving performance over what would be achievable using a similar technique at atmospheric pressure. Provision is made for determining working measurement volume by expansion from a calibrated reference volume incorporated in the piping. Demonstrated operating range is ∼10−8–10−4 atm cm3/s (10−13–10−9 mol/s) regardless of the gas being used. The sensing element is an industrial grade capacitance diaphragm manometer. A very inexpensive home computer performs all control and calculations. The accuracy and performance of this system have been verified through comparison to other leak calibrators.
Show PACS
07.30.Hd Vacuum testing methods; leak detectors
07.30.Bx Degasification, residual gas

Matrix calculation of pressures in high‐vacuum systems

Haruo Hirano, Yukihito Kondo, and Nagamitsu Yoshimura

J. Vac. Sci. Technol. A 6, 2865 (1988); http://dx.doi.org/10.1116/1.575614 (5 pages)

Full Text: | Download PDF

Show Abstract
A matrix analysis method has been applied to two high‐vacuum systems: an outgassing pipe and an electron microscope. These vacuum systems were analyzed as linear vacuum circuits with pressure sources, current sources, and conductances by using a digital computer. The pressures at six points along an outgassing pipe were calculated for two different models. A 5% difference of pressures was noted between the models. Pressures throughout an electron microscope high‐vacuum system were also successfully calculated by a computer. The pressure varied over three orders of magnitude depending on position.
Show PACS
07.30.Hd Vacuum testing methods; leak detectors
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

A spherical ionization gauge for use in a high magnetic field

N. Ogiwara and M. Maeno

J. Vac. Sci. Technol. A 6, 2870 (1988); http://dx.doi.org/10.1116/1.575615 (6 pages) | Cited 1 time

Full Text: | Download PDF

Show Abstract
This paper describes a new type of hot filament ionization gauge for measurement of neutral gas density in a high magnetic field. The notable feature of the gauge is its spherical symmetry. The ion current varies linearly with the pressure from 10−4 to 1 Pa for N2 and Ar. The sensitivity changes by no more than +20% in a magnetic field of up to 1.2 T. The main reasons for this small change in the sensitivity are as follows: (i) The probability of ionization of gas molecules is almost independent of a high magnetic field, because the spherical symmetry causes electrons to be emitted from the filament to the region in which the electric field is almost parallel to the magnetic field; (ii) the probability of ion collection is independent of a magnetic field.
Show PACS
07.30.Dz Vacuum gauges

Modeling of impurity release rates during wall conditioning of a vacuum vessel by electric discharge

K. Dimoff, C. Boucher, K. J. Parbhakar, and A. K. Vijh

J. Vac. Sci. Technol. A 6, 2876 (1988); http://dx.doi.org/10.1116/1.575616 (7 pages)

Full Text: | Download PDF

Show Abstract
An analytic expression is derived for the time behavior of impurity levels measured by residual gas analyzer during the conditioning of a vacuum vessel wall by an electric discharge in molecular hydrogen at low pressure. Physical pumping and diffusive outgassing of impurity‐related molecules from within the vessel wall suffice to give a time dependence which follows the measurement process more precisely than the phenomenologically deduced t−δ law, where 0.7≤δ≤2.
Show PACS
07.30.Bx Degasification, residual gas
52.40.Hf Plasma-material interactions; boundary layer effects

A precision table for ultrahigh vacuum made of aluminum alloys

H. Saeki, J. Ikeda, and H. Ishimaru

J. Vac. Sci. Technol. A 6, 2883 (1988); http://dx.doi.org/10.1116/1.575617 (4 pages) | Cited 2 times

Full Text: | Download PDF

Show Abstract
Recently an ultrahigh vacuum environment has been necessary to reduce impurities in the production of high‐density integrated circuits. In particular, tables permitting precise positioning with low outgassing rates have been required for thin‐film processing equipment and surface analysis systems using spot beams. An X–Y–θ three‐axis table made of aluminum alloys with a special surface treatment for ultrahigh vacuum environments has been developed. The stroke of the X and Y axes is 75 mm, and the rotational range of the θ axis is 360°. The X and Y axes are driven by built‐in stepping motors, connected directly to aluminum alloy ballscrews. The stator of the motor is made using stainless‐steel sheath cable. The screws and nuts of the ballscrews are coated with TiC, and the balls are coated with Ag. The characteristics of the table have been investigated in atmosphere before and after baking. The measured error motions for the X axis were pitch ±2.3 μm/75 mm and yaw±1.4 μm/75 mm; and for the Y axis were pitch ±0.78 μm/75 mm and yaw ±0.22 μm/75 mm. The resolution and repeatability for the X and Y axes was 15 μm ±2 μm/pulse, and for the θ axis was 1.8° ±0.09°/pulse. The mechanical characteristics were maintained after baking. The table moved in an ultrahigh vacuum environment of the order of 10−11 Torr as it had in atmosphere.
Show PACS
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials
85.40.Hp Lithography, masks and pattern transfer

Correlation of interface chemistry and growth mode of Ce on polyimide (pyromellitic dianhydride–oxydianiline)

J. G. Clabes

J. Vac. Sci. Technol. A 6, 2887 (1988); http://dx.doi.org/10.1116/1.575618 (6 pages)

Full Text: | Download PDF

Show Abstract
Interface properties such as chemical bonding and structure play an important role in adhesion of metals in polymers. Ce, a highly reactive metal, was chosen for these experiments in order to promote enhanced chemistry at the interface to polyimide [pyromellitic dianhydride–oxydianiline (PMDA–ODA)] and to distinguish anticipated reaction products on the basis of their valency. We have studied the progression of interface formation upon metal deposition over a wide coverage range, in situ, by high‐resolution x‐ray photoelectron spectroscopy, monitoring the polyimide‐ and Ce‐related core levels and changes in the valence‐band regime. The interaction is completely dominated by compound formation which differentiates this metal–polymer (MP) system from others studied thus far. The results suggest less selectivity towards the PMDA moiety, indicative of parallel reaction pathways. One can therefore conclude that charge transfer is not a necessary prerequisite of subsequent compound formation for this MP interface. The termination of this spontaneous reaction process at room temperature is evidenced by the peculiar nucleation of unreacted metal at surface defects and the growth of huge planar islands. No other MP system has exhibited such distinct behavior.
Show PACS
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.35.Dv Composition, segregation; defects and impurities

Study of the enhanced oxidative degradation of polymer films at polymer/copper (oxide) interfaces using depth profile and inert marker techniques

Michael C. Burrell, Julie Fontana, and John J. Chera

J. Vac. Sci. Technol. A 6, 2893 (1988); http://dx.doi.org/10.1116/1.575447 (4 pages) | Cited 1 time

Full Text: | Download PDF

Show Abstract
The degradation of poly(ester imide) films on metal substrates was monitored by determining the changes in polymer film thickness using x‐ray photoelectron spectroscopy combined with ion sputter depth profiling. Thin films (1000–7000 Å) of poly(ester imide) wire enamel were spin coated onto metal substrates and aged in air at 200 °C for several hours. For films on copper substrates, thermal oxidative degradation of the polymer led to thinning of the film (2.5–3 Å/min), whereas films on aluminum substrates did not exhibit a decrease in thickness. The catalytic effect of copper upon the degradation of the polymer occurs primarily at the copper (oxide)/polymer interface, as revealed by the location of an inert gold marker layer within the polymer film before and after aging.
Show PACS
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.65.-b Surface treatments
81.05.Bx Metals, semimetals, and alloys
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

An x‐ray photoemission spectroscopy study of chemical interactions at silver/plasma modified polyethylene interfaces: Correlations with adhesion

L. J. Gerenser

J. Vac. Sci. Technol. A 6, 2897 (1988); http://dx.doi.org/10.1116/1.575448 (7 pages) | Cited 13 times

Full Text: | Download PDF

Show Abstract
Plasma treatment is a convenient way to modify the surface (∼25–50 Å) of a polymer for improved adhesion of vacuum deposited metals. X‐ray photoemission analysis of plasma modified polyethylene (PE) indicates no detectable chemical effects for argon plasmas, whereas oxygen and nitrogen plasmas create new chemical species which alter the chemical reactivity of the PE surface for vacuum deposited Ag. The adhesion strength of vacuum deposited Ag on PE is shown to increase in the following order: untreated<argon plasma<oxygen plasma<nitrogen plasma treated PE. Changes in chemical bonding and nucleation of submonolayer vacuum deposited Ag on plasma treated PE correlate with Ag/PE adhesion. Changes in the PE core levels after submonolayer deposition of Ag are interpreted as due to the formation of Ag–O–C and Ag–N–C species on oxygen and nitrogen plasma treated PE, respectively. In contrast, no chemical bonding effects are observed on untreated or argon plasma treated PE. The Ag valence‐band structure suggests that the plasma induced species act as nucleation and chemical bonding sites resulting in a much smaller average cluster size for vacuum deposited Ag. Interfacial analysis of peeled thin films of vacuum deposited Ag on PE suggests the locus of failure changes from interfacial adhesive failure for untreated and argon plasma treated PE to cohesive failure of the PE for oxygen and nitrogen plasma treated PE.
Show PACS
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.35.Gy Mechanical properties; surface strains
81.40.Pq Friction, lubrication, and wear
73.20.At Surface states, band structure, electron density of states

The Au/Si(111)7×7 interface: Correlation between electronic and morphological properties by high‐resolution electron energy‐loss spectroscopy, ultraviolet photoemission spectroscopy, and transmission electron microscopy

G. Mathieu, R. Contini, J. M. Layet, P. Mathiez, and S. Giorgio

J. Vac. Sci. Technol. A 6, 2904 (1988); http://dx.doi.org/10.1116/1.575449 (6 pages) | Cited 2 times

Full Text: | Download PDF

Show Abstract
We have studied the diffusive Au/Si(111)‐7×7 interface by surface sensitive techniques (high‐resolution electron energy‐loss and ultraviolet photoemission spectroscopies) and by transmission electron microscopy (TEM). The combination of the spectroscopic methods with TEM allows us to propose a new morphological description of the layer growing at room temperature, namely, that there are crystallites of pure Au embedded in an amorphous AuxSi1−x alloy matrix.
Show PACS
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Fx Diffusion; interface formation
68.35.Dv Composition, segregation; defects and impurities

Hydrogen adsorption on some a‐Ge1−xCx:H films prepared by radio‐frequency sputtering

Ruth Shinar

J. Vac. Sci. Technol. A 6, 2910 (1988); http://dx.doi.org/10.1116/1.575450 (4 pages) | Cited 1 time

Full Text: | Download PDF

Show Abstract
Auger and electron energy‐loss spectroscopy (EELS) were used to study the interaction of hydrogen atoms with clean, Ar+ sputter‐etched amorphous germanium (a‐Ge), hydrogenated amorphous germanium (a‐Ge:H), and some hydrogenated amorphous germanium carbide (a‐Ge1−xCx:H) films prepared by rf sputtering. The EEL spectra indicate preferential sputtering of hydrogen bonded to germanium by ion etching in a‐Ge:H as well as in a‐Ge0.9C0.1:H and the creation of new surface Ge–H bonds following exposure to atomic hydrogen. No such information could be obtained from EELS studies for films containing 25 at. % or more carbon. However, Auger line‐shape measurements of Ge and C in a‐Ge1−xCx:H, before and after exposure to dissociated hydrogen, yield the same conclusions for x≤0.5. There is no evidence of preferential removal of hydrogen bonded to carbon by Ar+ etching or of formation of new C–H surface bonds in the alloy films by hydrogen adsorption. The preferential removal of hydrogen bonded to Ge but not to C may explain the relatively high density of bulk C–H bonds in rf sputter‐deposited a‐Ge1−xCx:H films.
Show PACS
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Cd Deposition by sputtering

Residual stress anisotropy, stress control, and resistivity in post cathode magnetron sputter deposited molybdenum films

R. E. Cuthrell, D. M. Mattox, C. R. Peeples, P. L. Dreike, and K. P. Lamppa

J. Vac. Sci. Technol. A 6, 2914 (1988); http://dx.doi.org/10.1116/1.575451 (7 pages) | Cited 3 times

Full Text: | Download PDF

Show Abstract
As part of the program to develop a large‐area thin‐film pulse heater for a lithium ion source, the residual stress in post cathode magnetron sputter deposited molybdenum films has been studied. It was found that in films prepared in the low‐pressure sputtering regime, the residual film stress is very sensitive to the gas pressure during sputtering and that the film stresses are highly anisotropic. The transition pressure for changing from compressive to tensile residual stress, as defined by Thornton and Hoffman, depends on the relationship between the measurement direction in the film and the post cathode orientation. In order to deposit a nearly stress‐free film a pressure cycling technique was developed which deposited alternate film layers containing tensile and compressive stresses. Film resistivity and thermal coefficient of resistivity measurements were made during the pulse heating of the molybdenum films.
Show PACS
68.60.Bs Mechanical and acoustical properties
81.15.Cd Deposition by sputtering
73.61.At Metal and metallic alloys

Structural, ferroelectric, and pyroelectric properties of highly c‐axis oriented Pb1−xCaxTiO3 thin film grown by radio‐frequency magnetron sputtering

Eiso Yamaka, Hirohito Watanabe, Hideki Kimura, Hiroyuki Kanaya, and Haruo Ohkuma

J. Vac. Sci. Technol. A 6, 2921 (1988); http://dx.doi.org/10.1116/1.575452 (8 pages) | Cited 20 times

Full Text: | Download PDF

Show Abstract
Thin films of ferroelectric Pb1−xCaxTiO3 (x=0.0–0.4) were formed on MgO, Pt/MgO, SrTiO3, and Pt/SrTiO3 substrates by rf magnetron sputtering. Characterization of the films by x‐ray diffraction, x‐ray precession, scanning electron microscopy, and electron probe microanalysis showed them to be epitaxially grown with their c‐axis oriented perpendicular to the substrate. The decrease in the Curie temperature Tc and the increase in the pyroelectric coefficient dPs/dT with an increase in Ca doping were successfully explained by assuming that the Ca ions occupied Pb ion sites. Pyroelectric infrared detectors using Pb0.7Ca0.3TiO3 thin‐film elements gave better performance than the detectors using PbTiO3 ceramic elements. The internal bias field EB and fixed polarization PB were observed to be a function of both the Ca content and temperature in ferroelectric hysteresis curves as well as in hysteresis curves of the dielectric constant as a function of the applied electric field. These phenomena were explained by the difference in thermal behavior between the sputtered films and the substrates at temperatures below Tc.
Show PACS
81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology
77.80.-e Ferroelectricity and antiferroelectricity
77.70.+a Pyroelectric and electrocaloric effects

Capillary array dosing and angular desorption distribution measurements: A general formalism

A. Winkler and J. T. Yates

J. Vac. Sci. Technol. A 6, 2929 (1988); http://dx.doi.org/10.1116/1.575453 (4 pages) | Cited 46 times

Full Text: | Download PDF

Show Abstract
The flux of molecules from a source intercepted by a target has been calculated. The obtained formalism can be applied to capillary array dosing as well as angular distribution measurements in thermal desorption from single‐crystal surfaces. A critical comparison of the theoretical results with recently obtained experimental data is presented.
Show PACS
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
07.77.-n Atomic, molecular, and charged-particle sources and detectors
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Thermal desorption of deuterium and helium implanted in oxide overlayers on molybdenum

Y. Baba and T. A. Sasaki

J. Vac. Sci. Technol. A 6, 2933 (1988); http://dx.doi.org/10.1116/1.575454 (5 pages)

Full Text: | Download PDF

Show Abstract
The thermal desorption behaviors of deuterium and helium implanted in oxidized molybdenum have been investigated. Both ions are hardly trapped in metallic molybdenum, whereas the trapping efficiency grows with increasing oxidation temperature of molybdenum. There exist two different trapping sites in molybdenum trioxide: interstitial sites and oxygen vacancies. The ions trapped at interstitial sites desorb without surface chemical changes, whereas desorption of ions trapped in oxygen vacancies accompanies the recovery of the surface chemical state, i.e., Mo(IV)→Mo(VI). The activation energies for the detrapping processes of deuterium trapped at interstitial sites and in oxygen vacancies are determined to be 0.45 and 1.0 eV, respectively.
Show PACS
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
81.05.Bx Metals, semimetals, and alloys
61.72.jd Vacancies
61.72.jj Interstitials
61.72.up Other materials

Experimental tests of the steady‐state model for oxygen reactive ion etching of silicon‐containing polymers

C. W. Jurgensen, A. Shugard, N. Dudash, E. Reichmanis, and M. J. Vasile

J. Vac. Sci. Technol. A 6, 2938 (1988); http://dx.doi.org/10.1116/1.575455 (7 pages) | Cited 11 times

Full Text: | Download PDF

Show Abstract
A steady‐state model based on a silicon material balance has been proposed to predict the oxygen reactive‐ion‐etching resistance of organosilicon polymers. This model assumes that the rate determining step is sputtering of SiO2 film that forms on the surface of the organosilicon polymer. It predicts the etching rate of organosilicon polymers relative to the sputtering rate of SiO2 , based on the mass density of silicon in the polymer. The steady‐state etching rate of a silyl novolac polymer is accurately predicted by the model over a wide range of etching conditions. Silyl methacrylates etch at the predicted rate under high‐bombardment‐energy conditions typical of trilevel processing, but exceed the predicted rate under low‐bombardment‐energy conditions. Surface analysis shows that the SiO2 film thickness continues to increase with time under these conditions, invalidating the steady‐state approximation. Low silicon content (4.1 wt. %) polymers do not etch according to the model but form highly porous oxides that continuously accumulate on the surface of the polymer.
Show PACS
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.65.-b Surface treatments
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.55.-a Thin film structure and morphology

Preparation of nitride films by Ar+‐ion bombardment of metals in nitrogen atmosphere

Y. Baba, T. A. Sasaki, and I. Takano

J. Vac. Sci. Technol. A 6, 2945 (1988); http://dx.doi.org/10.1116/1.575456 (4 pages) | Cited 12 times

Full Text: | Download PDF

Show Abstract
A preparation of thin nitride films on metal surfaces was presented. The nitrogenation was carried out by bombarding the metals with 8‐keV Ar+ ions in nitrogen at 1.0×10−3 Pa. Among the 13 metals examined, the nitrides of nine metals were produced. The approximate thickness of the TiN film was ∼7 nm, which is comparable to the range of the Ar+ ion. The saturated values of the surface N/Me (Me:metal) are different among various metals examined, and are related to the chemical reactivity of the metal with nitrogen. The N/Ti ratio was inversely proportional to the Gibbs energy of nitride formation. These results suggest that the nitride was produced not only through the knock‐on collision by the Ar+ ions but also through the thermochemical reaction at the nitrogen–metal interface, which is promoted by the ion bombardment.
Show PACS
81.05.Bx Metals, semimetals, and alloys
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

The effect of excitation frequency on emission spectra of polymerization plasmas

E. Lopata and J. Countrywood

J. Vac. Sci. Technol. A 6, 2949 (1988); http://dx.doi.org/10.1116/1.575457 (4 pages) | Cited 2 times

Full Text: | Download PDF

Show Abstract
The excitation frequency is known to have an effect on the rate of deposition of polymer thin films produced by a glow discharge process. This has been attributed to changes in the electron energy distribution function (EEDF). Any appreciable change in the EEDF would be expected to be revealed by plasma emission spectroscopy. Our findings are herein reported for deposition plasmas containing C3 H6 and Ar at dc, 40‐kHz, and 27.12‐MHz excitation frequencies; included are data on film deposition rate and optical clarity which also vary with excitation frequency.
Show PACS
81.15.Rs Spray coating techniques
82.35.-x Polymers: properties; reactions; polymerization
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.80.Hc Glow; corona

Auger electron spectroscopy technique for nitrogen depth profiling in titanium compounds

R. Pantel, D. Levy, and D. Nicolas

J. Vac. Sci. Technol. A 6, 2953 (1988); http://dx.doi.org/10.1116/1.575458 (4 pages) | Cited 4 times

Full Text: | Download PDF

Show Abstract
Although Auger electron spectroscopy is one of the most used techniques for surface and thin‐film analysis, its application to TiN is very problematic. This is due to the overlapping of the principal nitrogen Auger transition (380 eV) with the Ti (383 eV) one. Therefore nitrogen detection in Ti compounds is very difficult. Generally an indirect nitrogen concentration evaluation is obtained using a ratio of two Auger peak amplitudes [‘‘Ti+N’’ (383 eV), Ti (418 eV)]. However this technique is inaccurate in alloys other than TiNx (ternary compounds or multilayers such as TiNxOy or TiNx/TiOy). In this paper we present a direct N detection based on the use of a secondary nitrogen Auger transition N KL1L2 (369 eV). Using a high‐resolution cylindrical mirror analyzer this peak is separated from the Ti peaks. This simple procedure allows automatic depth profiling when combined with ion milling. We then present applications on Ti/Si and Ti/SiO2 structures rapidly annealed in N2 (650 °C, 100 s).
Show PACS
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.35.Dv Composition, segregation; defects and impurities
68.55.Nq Composition and phase identification

Electron energy‐loss spectroscopy of molybdenum disilicide

R. S. Rastogi, V. D. Vankar, M. C. Bhatanagar, and K. L. Chopra

J. Vac. Sci. Technol. A 6, 2957 (1988); http://dx.doi.org/10.1116/1.575459 (3 pages)

Full Text: | Download PDF

Show Abstract
Thin films of molybdenum disilicide prepared by solid‐state diffusion of Mo/Si(111) have been investigated by electron energy‐loss spectroscopy for their valence level and core level electron excitations. In the valence band, interband transitions around 2.2, 3.9, and 5.3 eV have been observed. These transitions have been interpreted as electron excitations of the metal d band and Mo(4d)–Si(3p) levels. These transitions are in excellent agreement with the available experimental and theoretical data on MoSi2 electronic band structure. In the core levels, the electron excitations corresponding to the Si(2p) core level are shifted towards higher energy while that of the Mo(3d) are shifted towards lower energy. These shifts indicate a change in the bonding nature of Mo–Si during silicidation.
Show PACS
71.20.Nr Semiconductor compounds
71.20.Ps Other inorganic compounds

Axial distribution of optical emission in a planar magnetron discharge

Lan Gu and M. A. Lieberman

J. Vac. Sci. Technol. A 6, 2960 (1988); http://dx.doi.org/10.1116/1.575460 (5 pages) | Cited 34 times

Full Text: | Download PDF

Show Abstract
We measure the axial distribution S of optical emission in a dc planar magnetron discharge for various currents I, voltages V, and magnetic fields B. We develop an integral equation model of the distribution, which is in good agreement with the measurements. At fixed I, we find that the position Δ from the cathode of the peak in emission Smax scales as the ion Child law sheath thickness Δ∝V7/8/B1/4, and that for small B’s, Smax ∝B/V1/2.
Show PACS
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.80.-s Electric discharges
84.40.Fe Microwave tubes (e.g., klystrons, magnetrons, traveling-wave, backward-wave tubes, etc.)

Hydrogen pumping and release by graphite under high‐flux plasma bombardment

Y. Hirooka, W. K. Leung, R. W. Conn, D. M. Goebel, B. Labombard, R. Nygren, and K. L. Wilson

J. Vac. Sci. Technol. A 6, 2965 (1988); http://dx.doi.org/10.1116/1.575461 (13 pages)

Full Text: | Download PDF

Show Abstract
Inert gas (helium or argon) plasma bombardment has been found to increase the surface gas adsorptivity of isotropic graphite (POCO‐graphite), which can then getter residual gases in a high‐vacuum system. The inert gas plasma bombardment was carried out at a flux ≊1×1018 ions s−1 cm−2 to a fluence of the order of 1021 ions/cm2 and at temperatures around 800 °C. The plasma bombarding energy was varied between 100 and 200 eV. The gettering speed of the activated graphite surface is estimated to be as large as 25 l s−1 cm−2 at total pressures between 10−6 and 10−7 Torr. The gettering capacity estimated is 0.025 Torr l/cm2 at room temperature. The gettering capability of graphite can be easily recovered by repeating inert gas plasma bombardment. The activated graphite surface exhibits a smooth, spongelike morphology with significantly increased pore openings, which correlates with the observed increase in the surface gas adsorptivity. The activated graphite surface has been observed to pump hydrogen plasma particles as well. From calibrated H‐alpha measurements, the dynamic hydrogen retention capacity is evaluated to be as large as 2×1018 H/cm2 at temperatures below 100 °C and at a plasma bombarding energy of 300 eV. The graphite temperature was varied between 15 and 480 °C.
Due to the plasma particle pumping capability, hydrogen recycling from the activated graphite surface is significantly reduced, relative to that from a presaturated surface. A presaturated surface was also observed to reproducibly pump a hydrogen plasma to a concentration of 9.5×1017 H/cm2. The hydrogen retention capacity of graphite is found to decrease with increasing temperature. At temperatures between 450 and 480 °C, the hydrogen retention estimated for the activated surface and presaturated surface is 7.9×1017 and 2.7×1017 H/cm2, respectively. A transient pumping mechanism associated with the spongelike surface morphology is conjectured to explain the large hydrogen retention capacity. Hydrogen release behavior under helium and argon plasma bombardment was also investigated, and the result indicated the possibility of some in‐pore retrapping effect. The effective plasma impact desorption cross sections are evaluated in the plasma bombarding energy range from 15 to 300 eV. A significant fraction (70%–80%) of preimplanted hydrogen was observed to release under inert gas plasma bombardment to a fluence of 6×1019 ions/cm2. The graphite surface, once saturated, can be reactivated via plasma‐impact hydrogen desorption, regardless of the helium and argon bombarding energy in the range examined here.
Show PACS
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Temporal evolution of collisionless sheaths

M. H. Cho, N. Hershkowitz, and T. Intrator

J. Vac. Sci. Technol. A 6, 2978 (1988); http://dx.doi.org/10.1116/1.575462 (9 pages) | Cited 30 times

Full Text: | Download PDF

Show Abstract
We have performed experimental measurements to determine the temporal evolution of Langmuir sheaths near an electrode to which a negative step bias is applied in a collisionless argon plasma. The plasma was produced by a hot‐filament discharge in a multidipole device. Plasma potential data were obtained using emissive probes with two different techniques: time resolved sampling and time averaged techniques. The sheath is found to initially form close to the electrode, to extend to a maximum separation, and to contract to a steady‐state value. The time scale required to reach a steady state is close to the time scale of the presheath relaxation. Characteristics of sheaths in rf plasmas are also measured using a parallel‐plate plasma capacitor. It is observed that the plasma potential profile has significant variation with frequency, even for frequencies as low as 1 kHz which are far below the ion plasma frequency (∼1 MHz).
Show PACS
52.70.Ds Electric and magnetic measurements

Diagnostics by optical emission spectroscopy in the vicinity of the substrate during magnetron sputtering of Ti

T. Pech, J. P. Chabrerie, and A. Ricard

J. Vac. Sci. Technol. A 6, 2987 (1988); http://dx.doi.org/10.1116/1.575463 (5 pages) | Cited 3 times

Full Text: | Download PDF

Show Abstract
The spatial distribution of excited states for neutral Ti and Ar, as well as for ionized Ti, have been investigated in Ar discharges at 0.27 Pa, in the neighborhood of a grounded substrate, at variable temperatures θs (up to ∼500 °C), for given values of the magnetron current (up to 4 A). Pronounced local variations of excited states, with a maximum of spectral line intensities Iλ at ∼ 1 mm from the substrate, characterizing a fairly thin anode sheath, have been detected. The secondary electron emission from the anode is only weakly influenced by θs. The Iλ intensities increase with the power P, faster for Ti and Ti+ than for Ar: ITi∝P1.6, ITi+∝P2.3, and IAr∝P0.8.
Show PACS
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
81.15.Cd Deposition by sputtering
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.80.Hc Glow; corona

An electrohydrodynamic formalism for ion and droplet formation in stressed conducting fluids

N. M. Miskovsky, M. Chung, P. H. Cutler, T. E. Feuchtwang, and E. Kazes

J. Vac. Sci. Technol. A 6, 2992 (1988); http://dx.doi.org/10.1116/1.575464 (6 pages) | Cited 4 times

Full Text: | Download PDF

Show Abstract
An electrohydrodynamic surface capillary wave theory is developed for ion and droplet formation in electrically stressed conducting viscous fluids. This theory can be used to describe properties of electrohydrodynamic sources such as the liquid metal ion sources. Using the mathematical models of Chung et al., and Grossman and Muller, we have obtained the first‐order corrections of the Navier–Stokes equation for a three‐dimensional axially symmetric fluid. Formal solutions are developed for the eigenmodes describing the deformation of the surface as a function of applied electric field with both radial and longitudinal components. It is argued that the spatial variation of the complex mode amplitudes yield both the size and directional distribution of the emitted particles. The real part of the eigenfrequency associated with the excited eigenmode is related to the temporal behavior of instabilities on the fluid surface. From this one obtains the growth and decay rates of the time‐dependent ion and droplet emission. Finally, by applying the dynamical Laplace–Young stress condition, the critical fields necessary for the onset of instability of the fluid surface are obtained.
Show PACS
47.65.-d Magnetohydrodynamics and electrohydrodynamics
68.03.Kn Dynamics (capillary waves)
68.05.-n Liquid-liquid interfaces

Bounce‐coated ablation layers on fusion targets

R. Q. Gram, C. K. Immesoete, H. Kim, and L. Forsley

J. Vac. Sci. Technol. A 6, 2998 (1988); http://dx.doi.org/10.1116/1.575465 (4 pages) | Cited 2 times

Full Text: | Download PDF

Show Abstract
The current effort to achieve high compression of deuterium–tritium fuel by the Laboratory for Laser Energetics utilizes targets which are coated with uniform ablation layers of parylene. These layers are applied to the targets while they bounce on the vertically vibrating surface of a resonator. The low‐power plasma required to prevent targets from sticking to each other and to the vibrating surface increases the deposition rate by a factor of 2 to 4. Careful control of plasma conditions is required to maintain bouncing while avoiding overly rapid polymerization, defect growth, embrittlement, and other adverse effects in the parylene layers. Ablation layer quality is studied as a function of parylene monomer pressure, argon pressure, and plasma power, and the optimum operating region is discussed. Automatic control of these parameters is described. A tensile strength of 36 MPa is achieved in the bounce‐coated parylene layers, adding considerable strength to polymer shell targets. The permeability of these layers to Ar and He is measured.
Show PACS
79.20.Ds Laser-beam impact phenomena
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
28.52.-s Fusion reactors

On the pressure distribution of a ring accelerator: A Green’s function approach

K. Kanazawa

J. Vac. Sci. Technol. A 6, 3002 (1988); http://dx.doi.org/10.1116/1.575466 (4 pages)

Full Text: | Download PDF

Show Abstract
A method of calculating a pressure distribution in a one‐dimensional cyclic vacuum system is presented using Green’s function. The method is similar to one used in accelerator physics to investigate the motion of a particle in the guide field of a ring accelerator. The quantity which corresponds to the betatron function of an accelerator appears and it contains full information on the pumping characteristics of the system.
Show PACS
07.30.Hd Vacuum testing methods; leak detectors

Direct observations of island oxidation in nickel–cobalt alloys

E. E. Hajcsar, Z. Z. He, P. R. Underhill, and W. W. Smeltzer

J. Vac. Sci. Technol. A 6, 3006 (1988); http://dx.doi.org/10.1116/1.575467 (2 pages)

Full Text: | Download PDF

Abstract Unavailable
Show PACS
81.05.Bx Metals, semimetals, and alloys
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Dv Composition, segregation; defects and impurities

Oxidation at the polyimide/Cu interface

S. A. Chambers and K. K. Chakravorty

J. Vac. Sci. Technol. A 6, 3008 (1988); http://dx.doi.org/10.1116/1.575468 (4 pages) | Cited 2 times

Full Text: | Download PDF

Show Abstract
We have used x‐ray photoelectron spectroscopy in a normal emission configuration to investigate the chemistry of formation of the buried polyimide on Cu interface. We find that oxidation of the Cu surface begins within an hour of the curing process, and that Cu atoms in contact with the polyimide overlayer are completely oxidized to CuO after being stored in air for several days. This conclusion is in stark contrast with that drawn for the inverse system, Cu on polyimide, which has been shown to be essentially unreactive in vacuum over a time scale of several hours. We suggest that the key difference between the two systems is a very slow corrosion reaction perhaps involving trace amounts of chloride ion, water trapped in the polyimide overlayer, and the Cu surface. In contrast, the same experiment involving a Au substrate shows no evidence of reaction over a time frame of weeks.
Show PACS
81.05.Bx Metals, semimetals, and alloys
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.65.-b Surface treatments

The oxygen Auger line in ZnO and MgO

S. Z. Weisz, O. Resto, Y. Goldstein, G. Yaron, and A. Many

J. Vac. Sci. Technol. A 6, 3012 (1988); http://dx.doi.org/10.1116/1.575469 (3 pages)

Full Text: | Download PDF

Show Abstract
High‐resolution measurements reveal a double‐peak structure in the oxygen KLL main line of ZnO which is absent in MgO. We suggest that part of this fine structure is due to contributions from interatomic transitions and, as such, corresponds to two maxima in the valence‐band density of states of ZnO.
Show PACS
79.20.Fv Electron impact: Auger emission
71.20.Nr Semiconductor compounds
71.20.Ps Other inorganic compounds

Automated x‐ray photoelectron spectroscopy x‐ray source motor drive for ion sputtering applications

R. J. Streber, T. R. Pian, and D. A. Smullen

J. Vac. Sci. Technol. A 6, 3015 (1988); http://dx.doi.org/10.1116/1.575470 (2 pages)

Full Text: | Download PDF

Show Abstract
The x‐ray source on a commercial x‐ray photoelectron spectroscopy system has been retrofitted with an automated stepper motor drive. This device increases the x‐ray flux to the sample during sputter depth profiling and reduces the data collection time by as much as a factor of  4. In this note we discuss the mechanical, electrical, and computer modifications necessary to implement the device.
Show PACS
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
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.)

A simple ultrahigh vacuum shape memory effect shutter mechanism

A. P. Jardine, M. Ahmad, R. J. McClelland, and J. M. Blakely

J. Vac. Sci. Technol. A 6, 3017 (1988); http://dx.doi.org/10.1116/1.575471 (2 pages)

Full Text: | Download PDF

Abstract Unavailable
Show PACS
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials
62.20.F- Deformation and plasticity

A simple ultrahigh vacuum compatible sample cooling system

E. E. Chaban, P. H. Citrin, and F. Sette

J. Vac. Sci. Technol. A 6, 3018 (1988); http://dx.doi.org/10.1116/1.575472 (2 pages) | Cited 2 times

Full Text: | Download PDF

Show Abstract
A simple and inexpensive system is described for obtaining efficient and rapid cooldown of samples studied in ultrahigh vacuum. In most cases the design is easily adaptable to existing sample manipulators without sacrificing other desirable features.
Show PACS
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials
07.30.Hd Vacuum testing methods; leak detectors
Close

© 2013 AVS Science & Technology of Materials, Interfaces, and Processing Help | Contact
close