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Sep 1965

Volume 2, Issue 5, pp. 221-272


Diffusion-Controlled Sorption in High-Density Discharges

H. S. Maddix and M. A. Allen

J. Vac. Sci. Technol. 2, 221 (1965); http://dx.doi.org/10.1116/1.1492431 (7 pages) | Cited 1 time

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An experimental technique is described for obtaining reproducible sorption measurements in high-density discharges. Data are given for the sorption of argon, neon, and helium at the quartz walls of an electrodeless discharge for a surface temperature range of −35 ° to 750 °C. The complex dependence of sorption on temperature and discharge power is described in terms of sticking times, depth of ion penetration, diffusion coefficients, and flux rates. A theory is presented which gives good agreement with experiment. Maximum diffusion of gas into the walls occurs when the product of sticking time and ion flux is equal to the number of available trapping sites at the surface. The average depth of ion penetration in quartz was calculated from the theory and data to be in the range of 3 to 7×10−8 cm for helium, neon, and argon ions with bombarding energies of 12 to 17 eV.
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52.40.Hf Plasma-material interactions; boundary layer effects
52.80.-s Electric discharges

Combustion of Diffusion-Pump Fluids in Oxygen Atmospheres

C. W. Solbrig and W. E. Jamison

J. Vac. Sci. Technol. 2, 228 (1965); http://dx.doi.org/10.1116/1.1492432 (6 pages)

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The use of oxygen as an emergency pressurizing and life-support gas in man-rated space chambers presents a combustion hazard with oil diffusion pumped systems. This study determined the ignition characteristics of five commonly used pump fluids in pure oxygen atmospheres at low pressures in combustion-bomb experiments. The results were verified in tests in diffusion pumped systems. Spontaneous ignition studies were conducted with DC-705, DC-704, Convalex 10, Convoil 20, and tricresyl phosphate in the temperature range 600 ° to 900 °F at pressures from 0.01 to 400 Torr, and concentrations from fuel rich to fuel lean. Verification tests were conducted with DC-705, DC-704, and Convalex 10 in a 6-in. diffusion-pumped system by pressurizing the system to 8 psia with pure oxygen and observing for spontaneous and spark initiated combustion. Additional verification tests with DC-705 and DC-704 were conducted in a 35-in. diffusion pump.
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82.33.Vx Reactions in flames, combustion, and explosions
07.30.Cy Vacuum pumps

Insulation of High Voltage Across Solid Insulators in Vacuum

John P. Shannon, Sanborn F. Philp, and John G. Trump

J. Vac. Sci. Technol. 2, 234 (1965); http://dx.doi.org/10.1116/1.1492433 (6 pages) | Cited 15 times

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Surface conductivity and flashover in vacuum were studied using constant potentials up to 350 kV. Since discharges along the solid-vacuum interface appear to originate at or near the junction of the cathode electrode and the solid dielectric, methods of reducing the electric field at this critical region were explored. The more favorable approaches showed higher initial flashover values and could be conditioned to support more than 200 kV across borosilicate glass insulators in an interelectrode gap of 25 mm. The importance of intimate contact at the cathode-to-glass junction was confirmed.
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61.72.Mm Grain and twin boundaries
81.05.Bx Metals, semimetals, and alloys
81.15.Cd Deposition by sputtering

Density of Thin Evaporated Aluminum Films

Thomas E. Hartman

J. Vac. Sci. Technol. 2, 239 (1965); http://dx.doi.org/10.1116/1.1492434 (4 pages) | Cited 4 times

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The mass per unit area of evaporated aluminum films was measured with a piezoelectric quartz crystal microbalance. The thickness of the films was measured by multiple beam interferometry. The density of the films was determined from the sensitivity of the microbalance for a set of aluminum films ranging in thickness from a few hundred to a few thousand angstroms. The sensitivity of the microbalance was determined for a set of AT-cut quartz crystals ranging in fundamental frequency from 2 to 10 Mc∕sec. The density of the thinner films is less than the thicker films but rapidly approaches a value of 2.61±0.03 g∕cm3 for films in excess of 500 Å. This value is about 3% less than the value of 2.70 g∕cm3 for bulk aluminum. The aluminum films were evaporated in a pressure of 2×10−6 Torr with normal incidence on unheated glass and quartz substrates. The low density of the films cannot be explained on the basis of oxide formation in the residual atmosphere. The most likely explanation is that the films are porous which is partially confirmed by surface replication transmission electron micrographs.
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68.60.Wm Other nonelectronic physical properties
68.55.-a Thin film structure and morphology

Structure and Annealing Behavior of Metal Films Deposited on Substrates near 80 °K. II. Gold Films on Glass

R. W. Vook and F. Witt

J. Vac. Sci. Technol. 2, 243 (1965); http://dx.doi.org/10.1116/1.1492435 (7 pages) | Cited 6 times

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An in situ x-ray investigation of gold films has been carried out. Films were deposited on glass near 80 °K in high vacuum. Measurements were made on the as-deposited films as well as after annealing at temperatures up to 370 °C. In the as-deposited films the following results were obtained: (1) The lattice parameter perpendicular to the film surface was a few tenths of a percent less than the bulk value. (2) The films contained large numbers of intrinsic stacking faults and twins. (3) Nonuniform strains of the order of a few percent were also present. (4) The true crystallite sizes were estimated to be between several hundred and one thousand angstroms, where the estimate depended mainly on how the twin fault density was measured. (5) These films were (111) oriented with the strongest texture occurring in the thinnest film. When the films were annealed, changes in integrated x-ray intensity and line shapes were observed to occur near −15 °C. After room-temperature anneals, the imperfection densities had annealed out to such an extent that no contributions to line broadening and peak shifts could be detected. Grain growth occurred also upon annealing the films. A tendency towards the formation of a (100) texture was observed. The relative amount of growth occurring in the various (hkl) oriented crystallites was explained qualitatively in terms of surface and strain energies, the latter resulting from the difference in thermal expansion coefficients between film and substrate.
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68.55.-a Thin film structure and morphology
68.60.Dv Thermal stability; thermal effects
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Vacuum Breakdown in the Presence of Thermionic Cathodes

I. Brodie

J. Vac. Sci. Technol. 2, 249 (1965); http://dx.doi.org/10.1116/1.1492436 (8 pages) | Cited 3 times

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Experimental studies of field emission and breakdown with nickel electrodes contaminated by the presence of barium oxide and barium dispenser thermionic cathodes are presented. By comparing field emission and breakdown characteristics in a planar diode system and a cylindrical projection tube, it is demonstrated that minute quantities of material evaporating from the thermionic cathodes activate the tips of already existing whiskers on the nickel thus making them field emit more profusely. Breakdown is apparently caused by whisker disruption which can now occur at lower fields than that to which the surface had previously been conditioned. It is also possible that the new whiskers are formed by preferential condensation of the evaporation products. The areas from which electrons are emitted from the whisker tips usually contain only a few atoms and the regions from which electrons stream from the solid into the vacuum can be resolved in many of the electron images formed on the screen.
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85.45.Bz Vacuum microelectronic device characterization, design, and modeling
79.70.+q Field emission, ionization, evaporation, and desorption

Problem of Measuring Hydrogen Pressure in Ultrahigh-Vacuum Systems

T. W. Hickmott

J. Vac. Sci. Technol. 2, 257 (1965); http://dx.doi.org/10.1116/1.1492437 (2 pages) | Cited 2 times

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Abstract Unavailable
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07.30.Bx Degasification, residual gas

Abstracts of invited papers presented at the Thin-Film Division Symposium

J. Vac. Sci. Technol. 2, 271 (1965); http://dx.doi.org/10.1116/1.1492438 (2 pages) | Cited 1 time

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Abstract Unavailable
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.-a Thin film structure and morphology
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