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Jan 1969

Volume 6, Issue 1, pp. 1-272


Characterization, Control, and Use of Dielectric Charge Effects in Silicon Technology

J. R. Szedon and R. M. Handy

J. Vac. Sci. Technol. 6, 1 (1969); http://dx.doi.org/10.1116/1.1492613 (12 pages) | Cited 3 times

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The charge behavior of dielectric films on silicon is particularly important in device and integrated circuit technology because of surface effects. Models for ionic migration, fixed-interface charge, and injection trapping are reviewed for insulators used in silicon technology: thermally-grown silicon dioxide and chemical vapor-deposited silicon dioxide and silicon nitride. The distinctive characteristics of insulator charge related to these mechanisms are applied in the case of reactively sputtered SiO2 and Ta2O5. Ion migration and injection-trapping behavior are found under certain conditions of preparation for both materials. A degree of interface charge control is indicated in the study of sputtered silicon dioxide. More work is needed to establish the future utility of these materials.
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77.55.-g Dielectric thin films
85.40.Ls Metallization, contacts, interconnects; device isolation

Alternating Current Electrical Properties of Evaporated Molybdenum Oxide Films

J. G. Simmons and G. S. Nadkarni

J. Vac. Sci. Technol. 6, 12 (1969); http://dx.doi.org/10.1116/1.1492614 (6 pages) | Cited 8 times

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The limitations of dc measurements on doped thin film metal-insulator-metal structures are discussed, particularly in regard to the identification of the band structure of such systems. It is shown that the use of ac techniques provides a much wider scope of measurements which can be used to determine information about the energy diagram of thin film insulators. Furthermore such measurements have prominent characteristics which may be related to the band structure of the sample. The technique has been applied to evaporated Au–MoO3–Au samples, the capacitance of which are found to be extremely temperature sensitive; capacitance changes of 50:1 over 100 °C temperature range are reported. At low temperature the capacitance corresponds to the geometric capacitance, but at high temperatures is independent of the film thickness. The results are explained in terms of Schottky barriers at the Au–MoO3 interfaces, and the energy diagram of the system clarified. The doping density in the MoO6 is estimated to be about 1018 cm−3.
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73.40.Rw Metal-insulator-metal structures
77.55.-g Dielectric thin films
73.30.+y Surface double layers, Schottky barriers, and work functions

Photoresist Materials and Applications

R. O. Lussow

J. Vac. Sci. Technol. 6, 18 (1969); http://dx.doi.org/10.1116/1.1492615 (7 pages)

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Photoresists can be classified as either positive resists or negative resists depending on their mode of interaction with light. With the exception of photomasking, the process handling considerations for these two classes are similar. Photoresist performance is highly dependent on processing techniques. Typical processing procedures are discussed along with process problems and performance limitations of currently available materials. General materials chemistry of typical photoresists is discussed, and possible photomechanisms, development mechanisms, and adhesion mechanisms are considered. Substrates to which a resist is applied introduce another variable for consideration when evaluating resist performance.
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85.40.Hp Lithography, masks and pattern transfer

Use of Internal Photoemission for Characterizing Dielectric Films

Alvin M. Goodman

J. Vac. Sci. Technol. 6, 24 (1969); http://dx.doi.org/10.1116/1.1492616 (1 page)

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Abstract Unavailable
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
77.55.-g Dielectric thin films

Dielectric Materials in Semiconductor Devices

T. L. Chu

J. Vac. Sci. Technol. 6, 25 (1969); http://dx.doi.org/10.1116/1.1492617 (9 pages) | Cited 4 times

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Dielectric films are used extensively in semiconductor technology for masking against the diffusion of dopants into semiconductors, fabrication of active and passive components, electrical isolation between components, and surface passivation of devices. Silica is the most widely used dielectric in silicon devices at present, the preparation and properties of silica films are reviewed. However, silica is structurally porous, resulting in the high permeability of silica films toward impurities and the migration of impurity ions in silica films. Considerable efforts have been made to investigate other dielectrics during the past few years. The preparation and properties of several important dielectric films are discussed. Silicon nitride and aluminum oxide have been shown to be superior to silica in several respects. Various silica-silicon nitride and silica-alumina combinations have provided new and improved devices.
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77.55.-g Dielectric thin films
85.30.-z Semiconductor devices
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

New Developments in Getter—Ion Pumps in the U.S.S.R.

M. V. Kuznetsov, A. S. Nasarov, and G. F. Ivanovsky

J. Vac. Sci. Technol. 6, 34 (1969); http://dx.doi.org/10.1116/1.1492618 (6 pages) | Cited 1 time

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A series of sublimation titanium getter-ion pumps with directly heated titanium evaporators has been described by the authors in earlier publications. The pumps have pumping speed capability of 500–5000 liter∕sec. The pumps find an application in thin-film technology, in the manufacture of vacuum electron tubes, in the metallurgy of extra-pure metals, and in particle accelerators. The present work reports results of the development of sublimation pumps which offer higher capacity and can operate under more rigid temperature conditions.
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07.30.Cy Vacuum pumps

Diffusion of Nitrogen through Zr–Al Alloys in Vacuum

P. della Porta, B. Kindl, Ch. Ruetsch, and M. J. Schönhuber

J. Vac. Sci. Technol. 6, 40 (1969); http://dx.doi.org/10.1116/1.1492619 (5 pages) | Cited 2 times

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Sorption of nitrogen by a Zr–Al alloy has been measured at constant temperatures at 300 °C and 500 °C and for nitrogen pressures in the range 10−6 to 1 Torr. The pumping speed of the Zr–Al alloy for nitrogen decreases as the nitrogen pressure is increased and increases with temperature. For a constant nitrogen pressure the pumping speed tends to decrease with time owing to increase in surface concentration. After sorption has been completed the pumping speed can be partially or entirely restored to its initial value by maintaining the active surface at the operating temperature under a low nitrogen partial pressure, e.g., 10−6 Torr. During this recovery process nitrogen compounds at the surface migrate towards the interior of the Zr–Al alloy. The data obtained facilitate, at least qualitatively, the measurement of the diffusion of nitrogen from the surface to the bulk metal as a function of time at constant temperature. The data can also be used to predict the behavior of Zr–Al based getter pumps during and after high throughput applications.
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66.30.J- Diffusion of impurities
07.30.Cy Vacuum pumps

Multicomponent Getter Films for Getter-Ion Pumps

Lewis D. Hall

J. Vac. Sci. Technol. 6, 44 (1969); http://dx.doi.org/10.1116/1.1492620 (4 pages) | Cited 1 time

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Since the first commercial application of getter-ion pumping, a single metal, such as titanium, has usually been employed for this purpose. However, data obtained several years ago for bulk gettering, i.e., volume absorption of gases by heated materials, showed considerable increases in gettering rates for certain binary alloy compositions over the rate for either component alone. These results suggest that comparable effects might be observed in getterion pumps. This paper reports the results of experiments on the use of two reactive metals in a sputter-ion pump. Residual gas analyses are given and conclusions stated for titanium-zirconium and certain gases. The data indicate the superiority of two-component films, compared with titanium, for pumping in the milliTorr range. The differences in base pressures and residual gas spectra were minor.
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07.30.Cy Vacuum pumps

A Novel Diode Sputter-Ion Pump

Lawrence T. Lamont

J. Vac. Sci. Technol. 6, 47 (1969); http://dx.doi.org/10.1116/1.1492621 (5 pages) | Cited 1 time

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A new diode sputter-ion pump employing cathode posts which protrude within the anode cell is described. For suitable post geometry and material, stable pumping of argon at equilibrium speeds in excess of 25% of the nitrogen speed of the pump has been demonstrated. Effects of post geometry and material are explored with respect to optimizing argon speed. Pumping of noble gases is analyzed in terms of the “high-energy neutrals” hypothesis. Memory effects are shown to be reduced due to the enhancement of permanent pumping mechanisms. Field emission from the post results in greatly enhanced starting at extreme high vacuum.
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07.30.Cy Vacuum pumps

Method for Determining Getter Activity in Vacuum Devices

J. J. Maley and J. J. Moscony

J. Vac. Sci. Technol. 6, 51 (1969); http://dx.doi.org/10.1116/1.1492622 (4 pages)

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A commonly accepted method for determining the activity of a barium getter film within vacuum devices requires the measurement of pressure over the film. The getter pumping speed may be calculated from this measurement when the gas inlet rate and manifold pressure are known. In this work an attempt is made to evaluate the utility of determining getter activity as a function of emission decay of an oxide cathode. Mass spectrometer and emission decay data obtained from experiments carried out using either new or operated color picture tubes indicate that decay to an arbitrary level of 80%, induced by slow oxygen-poisioning, occurs rapidly within a narrow pressure range. This indicates that determination of oxygen getter capacity based on oxide-cathode emission decay may serve as an alternate method for comparing relative getter film activities.
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07.30.Kf Vacuum chambers, auxiliary apparatus, and materials

Enhancement of Noble Gas Pumping for a Sputter-Ion Pump

Souji Komiya and Nobuaki Yagi

J. Vac. Sci. Technol. 6, 54 (1969); http://dx.doi.org/10.1116/1.1492623 (4 pages)

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Enhancement of noble gas pumping has been observed for cathodes of different configuration and material. On the basis of the fact that erosion proceeds at the central portion of a cathode exposed to a Penning discharge, while sputtered material piles up at the circumferential area of the cathode, the ratio of the number of sputtered atoms per unit time to the number of impinging gas ions per unit time has been considered to be the controlling factor. A multiholed tantalum plate combined with conventional flat titanium cathode gives a pumping speed for argon about 40% as large as the pumping speed for nitrogen. With a flat tantalum cathode in one side and a flat titanium cathode in the opposite, the pumping speed for argon was about 27% of that for nitrogen. Both pumps, however, showed some 20% to 25% less speed for nitrogen compared with a conventional pump having a pair of flat titanium cathodes. A pump equipped with multiholed copper plates instead of multiholed tantalum plates was also tested, which did show an argon pumping speed twice as large as that of a conventional pump. During a long test run for the so-called argon instability, the multiholed tantalum pump did not show an appreciable pressure pulse at least for 700 h at 2×10−5 Torr with a constant throughput of argon.
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07.30.Cy Vacuum pumps

Influence of the Temperature History of Condensed Argon on its Hydrogen Adsorptivity at Low Temperatures

J. Hengevoss

J. Vac. Sci. Technol. 6, 58 (1969); http://dx.doi.org/10.1116/1.1492624 (5 pages) | Cited 1 time

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Adsorption of hydrogen on to multimolecular layers of condensed argon at the temperature of 9 °K was investigated. Before adsorbing hydrogen the condensed argon has been temperature cycled in different ways. It was found, that the adsorption capacity of the solid argon was 20 times higher when first condensed at 6 °K and subsequently heated to 9 °K than if it had first been condensed at 20 °K and subsequently cooled to 9 °K. Furthermore a loss in adsorption capacity was established, if solid argon condensed at 9 °K has been tempered at higher temperatures during only a few seconds. This result implies that structure and density of the solid argon depends on the temperature at which it has been built up. Presumably the argon molecules condensing at low temperatures only form loose packed layers because their surface mobility is very small in this case.
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68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics

Direct Observation of Epitaxy on MgO

H. Sato, S. Shinozaki, and L. J. Cicotte

J. Vac. Sci. Technol. 6, 62 (1969); http://dx.doi.org/10.1116/1.1492625 (3 pages) | Cited 5 times

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Abstract Unavailable
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)

Nucleation Studies Using Electron Transparent NaCl Substrates

R. F. Miller and R. W. Hoffman

J. Vac. Sci. Technol. 6, 65 (1969); http://dx.doi.org/10.1116/1.1492626 (4 pages)

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A technique has been developed for fabricating NaCl substrates sufficiently thin to be used as transmission substrates for electron microscopy. These small cleavage flakes, a few microns on a side, have been generally found in (100) orientations, and were placed on carbon-coated grids for observation in the microscope. A preliminary study has been made of the observed diffraction contrast features, in relation to the nucleation of gold on the rocksalt surfaces.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)

Impurity Effects on Heterogeneous Nucleation from the Vapor III—Mercury on Pyrex Glass

Anwar A. Kinawi and John B. Hudson

J. Vac. Sci. Technol. 6, 68 (1969); http://dx.doi.org/10.1116/1.1492627 (6 pages)

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The thermal accommodation coefficient (TAC) and critical supersaturation for nucleation (αcr) of mercury vapor on Pyrex glass have been studied over a wide range of vapor pressure and temperature conditions for both rigorously outgassed blown Pyrex surfaces, and for the same surfaces contaminated by the adsorption of water vapor or CO. Measurements were made by observing mass spectrometrically the mercury vapor flux leaving a substrate exposed to a flux of mercury atoms from a static vapor at fixed temperature and pressure. By appropriate manipulation of the substrate temperature both the TAC and αcr could be measured at essentially the same time and under identical conditions of vapor pressure, vapor temperature, and substrate contamination. Observed values of the TAC ranged from 0.6 to 1.0 depending on substrate condition. The αcr ranged from sightly more than unity to about seven over the temperature range from 263 °K to 225 °K. Impurity adsorption generally increased αcr, but not greatly. Results are interpreted in terms of the effect of impurity adsorption on the TAC and the substrate-nucleus contact angle.
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68.08.-p Liquid-solid interfaces
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Nonequilibrium Chemical Reactivity of Polycrystalline Iron Foils

T. Gabor and J. M. Blocher

J. Vac. Sci. Technol. 6, 73 (1969); http://dx.doi.org/10.1116/1.1492628 (6 pages)

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It is shown that continuous oxide films form on iron specimens in contaminated hydrogen atmospheres in which the metal is the thermodynamically favored phase; the explanation being that (1) oxygen in the gas does not come to equilibrium with the hydrogen but reacts with the iron, (2) the high activation energy of nucleation prevents reduction at the oxide-gas interface, and (3) hydrogen cannot diffuse through the continuous oxide film to the oxide-metal interface. The nonequilibrium nature of the oxidation is demonstrated by the finding that simultaneously with the formation of the continuous oxide films, bulk iron oxides on iron specimens become reduced. Also, reduction of the continuous oxide films proceeds readily when iron nuclei are formed by the addition of small quantities of iron carbonyl to the hydrogen stream.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
81.65.Mq Oxidation

Partial Pressure Calibration For Residual Gas Analyzers

Charles F. Morrison

J. Vac. Sci. Technol. 6, 79 (1969); http://dx.doi.org/10.1116/1.1492629 (4 pages)

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The method of reference transfer is applied to the full range partial pressure calibration of residual gas analyzers (RGA). Partial pressures are transferred across the upper orifice of a 10× pressure divider in such a way that a mathematically interrelated series of increasing partial pressures is generated. A gas flow measurement is used to establish the value of the partial pressure when it is in the 10−5 to 10−7 Torr region. For gases not residual to the vacuum system, calibration can begin at pressure levels limited primarily by electronic sensitivity and noise. Independence of RGA peak heights from interference by certain other gases was observed over a wide range of partial pressures of the several gases. Using this same equipment, inert gas fixed leaks were calibrated for just the inert gas components of their effluent.
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07.30.Bx Degasification, residual gas

Residual Gas Analysis and Leak Detection by Time-of-Flight Measurements on Neutral Metastable Atoms and Molecules

David A. Crosby and Jens C. Zorn

J. Vac. Sci. Technol. 6, 82 (1969); http://dx.doi.org/10.1116/1.1492630 (3 pages) | Cited 1 time

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We have designed and built a residual gas analyzer which is sensitive to N2, He, A, Ne, and other molecules which have energetic metastable states. The presence of these gases is revealed by measuring the time of flight of metastable, electrically neutral molecules between a pulsed electron gun and an Auger surface detector. When used as a residual gas analyzer, the present instrument can detect partial pressures of 10−7 Torr or greater; when used as a leak detector with helium tracer gas, the instrument can detect leak rates of 10−5 Torr liters∕sec or larger. The sensitivity of the present instrument can be markedly improved with obvious refinements. The metastable time-of-flight analyzer will operate in a 10−4 Torr environment and it has other advantages which may make it a valuable complement to the more conventional methods of leak detection and residual gas analysis.
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07.30.-t Vacuum apparatus

A Magnetron-Type Ion Source for Low-Pressure Residual Gas Analysis

W. D. Davis

J. Vac. Sci. Technol. 6, 85 (1969); http://dx.doi.org/10.1116/1.1492631 (4 pages)

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A conventional electron bombardment ion source operating at 10–100 μA emission is difficult to outgas sufficiently to allow accurate analysis of the residual gas at pressures below 10−12 Torr. In addition, the ions formed by electron bombardment of the surface may contribute specific mass peaks or a broad background of scattered ions to the mass spectrum. By using a magnetron-type ion source to increase the electron path, both these effects can be substantially reduced. The results obtained using this type ion source on a 5-cm radius magnetic sector instrument are described. Using an electron emission of 4×10−8 A, an ion current of 2×10−4 A∕Torr is obtained for N2. The two major peaks at low pressure are H2 (1.5×10−13 Torr) and mass 28 (3×10−14 Torr). No electronically desorbed ions have yet been observed and the background ion current is less than 10−17 Torr.
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07.77.Ka Charged-particle beam sources and detectors
07.30.Bx Degasification, residual gas

Mass Spectrometric Investigation of the Ion Desorption in UHV Gauges

W. K. Huber and G. Rettinghaus

J. Vac. Sci. Technol. 6, 89 (1969); http://dx.doi.org/10.1116/1.1492632 (4 pages)

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Electron-induced ion desorption from platinum, platinum-iridium, and molybdenum is studied by means of a quadrupole mass spectrometer, in order to determine its influence on the measurement of pressure by ionization gauges. Adsorbed species studied were H, H2O, CO, and O2. Ion yields, which were obtained under various conditions, are given. Interaction between coadsorbed species caused changes in the electronic desorption probabilities from the values observed for the separately adsorbed species. Suggestions are given for proper operation of ionization gauges in order to minimize ion desorption.
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07.30.Dz Vacuum gauges
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics

A Mass Spectrometer without Memory Effect for Gas Analysis in Ultrahigh Vacuum

H. Gentsch

J. Vac. Sci. Technol. 6, 93 (1969); http://dx.doi.org/10.1116/1.1492633 (4 pages) | Cited 1 time

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The described Omegatron mass-spectrometer is equipped with an internal heating device. All inner metal parts of the Omegatron gauge axe made of noble metal and can be held during the measurements at a maximum temperature of ≈ 500 °C. For cleaning and degassing the gauge the temperature of the metal parts can be increased up to 900 °C. All parts of the gauge made of base metals are enamelled. The fact that the memory effect can be held down by the entirely heatable Omegatron is a new and important criterion for measurements of partial pressures in the ultrahigh vacuum range. A further advantage of the heatable Omegatron-box is the remarkable constancy of ion transmission which is obtained at constant electrode-potentials even after many heating-cycles.
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07.75.+h Mass spectrometers
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials

Some Properties of the Monopole Mass Spectrometer

P. H. Dawson and N. R. Whetten

J. Vac. Sci. Technol. 6, 97 (1969); http://dx.doi.org/10.1116/1.1492634 (3 pages) | Cited 2 times

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Monopole mass spectrometer characteristics have been analyzed by determining ion trajectories under various operating conditions. The trajectories were obtained by numerical integration of the equations of motion. Peak shapes were derived for ions spending 20 rf cycles in the field, for various entrance∕exit slit ratios, with ion injection parallel to the instrument axis. Comparison with earlier results shows that resolutions at half-height can be expressed as (n∕p)2, where n is the number of cycles an ion spends within the field and p is constant for a given exit slitwidth. Ion injection at an angle to the instrument axis was also considered. Peaks then showed much less spread on the low mass side. For ions entering the field at a fixed angle, the peaks may exhibit a central dip if the exit slitwidth is too small.
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07.75.+h Mass spectrometers

Some Causes of Poor Peak Shapes in Quadrupole Field Mass Analyzers

N. R. Whetten and P. H. Dawson

J. Vac. Sci. Technol. 6, 100 (1969); http://dx.doi.org/10.1116/1.1492635 (4 pages) | Cited 2 times

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The performance of quadrupole field mass analyzers can be degraded by imperfections in the field. The imperfections may be the result of geometrical errors in the electrode structure or time errors in the applied waveforms. von Busch and Paul considered the nonlinear resonances resulting from these errors for the quadrupole mass filter using an analytical treatment of the ion motion. The authors extended this work to the three-dimensional quadrupole mass spectrometer, and using numerical computation of ion trajectories calculated the extent as well as the position of the resonances. In this paper, new experimental data are presented showing the occurrence of nonlinear resonances and the agreement between theory and experiment. The effect of adjustments in electrodes spacing on peak shapes was investigated. The results demonstrate that an analysis of the nonlinear resonances can provide an indication of the errors that are present. A new type of instability was found in the three-dimensional quadrupole, and a tentative explanation is presented.
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07.75.+h Mass spectrometers
41.85.-p Beam optics

Mass Spectrometric Sampling of Glow Discharges

John J. Sullivan and Rudolf G. Buser

J. Vac. Sci. Technol. 6, 103 (1969); http://dx.doi.org/10.1116/1.1492636 (6 pages) | Cited 2 times

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Continuous mass spectrometric sampling of the transient behavior of various gas species from a dc glow discharge originally filled with CO2, and mixtures of CO2-H2, (pressure range 50–1000 μ, discharge current 50–200 mA) have been studied by means of a specially constructed mass spectrometer (90° magnetic deflection) gas-sampling system. The sampling technique employed differential pumping of the mass spectrometer by a constricted ion-getter pump using a variable entrance aperture (valve) to the sampling system. The response of the system to time-varying concentrations is derived and the realization of optimum conditions discussed. This work is part of a program to investigate the gaseous electronics aspect of sealed CO2 laser operation.
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52.70.Nc Particle measurements
52.80.Hc Glow; corona
42.55.Lt Gas lasers including excimer and metal-vapor lasers

RF Sputtering of Multilayer Thin Films

L. Herte, A. Lang, and D. O. Myers

J. Vac. Sci. Technol. 6, 109 (1969); http://dx.doi.org/10.1116/1.1492637 (3 pages)

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Thin-film deposition rates and uniformity are presented for a large area rf diode of conventional style, with optimized parameters producing 1500 Å∕min copper and 500 Å∕min SiO2 without external magnetic field. Measurements of rate and corresponding uniformity were also made for Si3N4, Al2O3, nickel, molybdenum, and gold, where the thickness uniformity inside a 5-in.-diam. circle was ±2.5% for nickel and ±2% for SiO2. The sputtering apparatus consists of two 8-in.-diam water-cooled targets fed with 2.5 kW rf power, spaced 1-in. away from the substrate table. Influence of forward-coupled rf power on rate is also discussed.
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81.15.Cd Deposition by sputtering
85.40.Sz Deposition technology

Crystallographic Orientation of Zinc Oxide Films Deposited by Triode Sputtering

N. F. Foster

J. Vac. Sci. Technol. 6, 111 (1969); http://dx.doi.org/10.1116/1.1492638 (4 pages) | Cited 14 times

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Zinc oxide films for thin film piezoelectric transducer applications have been deposited by triode sputtering onto gold film surfaces. Films sputtered under relatively hydrocarbon-free conditions showed the “normal” orientation with the c axis perpendicular to the substrate surface. The addition of hydrocarbon vapors to the sputtering gas at the beginning of the deposition resulted in films at least partly oriented with the c-axis parallel to the substrate surface, and the simultaneous application of a reverse bias to the substrate holder produced films essentially completely oriented with this parallel orientation. Under oblique deposition conditions the average c axis direction in the film plane was directed towards the target, yielding good piezoelectric shear mode transducers with a uniform polarization. It is suggested that the hydrocarbon vapors polymerize in the discharge, covering the substrate with an organic film on which zinc oxide grows with the parallel orientation, and that alignment of the c-axis in the oblique deposition arises from preferential growth of crystallites oriented with their c axis towards the target.
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68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering

Epitaxial Thin Films of ZnO on CdS and Sapphire

G. A. Rozgonyi and W. J. Polito

J. Vac. Sci. Technol. 6, 115 (1969); http://dx.doi.org/10.1116/1.1492639 (5 pages) | Cited 17 times

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The technique for obtaining polycrystalline thin films of ZnO by sputtering of the compound has been perfected so that epitaxial films can be obtained on sapphire and CdS. Dependence of the crystalline perfection of the films on substrate temperature, deposition rate, and substrate polish has been studied in detail. Substrate temperatures from 100 ° to 500 °C and deposition rates from 1 to 100 Å∕min were studied. Film structure was evaluated by x-ray diffraction and reflection electron diffraction. Electrical and optical measurements were made to determine the resistivity, Hall mobility, optical absorption edge, and refractive index of films. It was found that these properties of the films were very similar to bulk crystal data except for the Hall mobility which was lower by almost two orders of magnitude. The poor mobility is attributed to scattering by defects introduced during the high-energy sputtering process.
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81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology
73.61.Ga II-VI semiconductors
78.66.Hf II-VI semiconductors

Electrical Characterization of Radio-Frequency Sputtering Gas Discharge

J. S. Logan, N. M. Mazza, and P. D. Davidse

J. Vac. Sci. Technol. 6, 120 (1969); http://dx.doi.org/10.1116/1.1492640 (4 pages) | Cited 10 times

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In the design of rf sputtering systems, the electrical equivalent of the gas discharge must be known. For this purpose, an experiment was conducted in which the electrical impedance (capacitance and conductance) of an rf sputtering gas discharge was determined as a function of pressure, magnetic field strength, and rf power input. The method of measurement involved the use of a matching network, an incident and reflected power meter, and a Boonton radio-frequency admittance meter. Values of conductance and capacitance for the discharge were deduced from measurements on the matching network after termination of the discharge. Results show that both capacitance and conductance increase strongly with increasing magnetic field. Capacitance changed from 0.97×10−13 F∕cm2 to 2.5×10−13 F∕cm2 between zero and 156 G. Conductance changed from 1.6×10−6 mho∕cm2 to 3.9×10−6 mho∕cm2 in the same interval. Pressure dependence was strongest at zero magnetic field, changing both capacitance and conductance approximately 30% between 7.5 and 30 mTorr (argon). At high magnetic field, there was very little effect. No appreciable change was observed between 1.1 and 6.5 W∕cm2 power application. Design equations are given for a simple matching network, and a design example is presented to demonstrate application.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
52.70.Ds Electric and magnetic measurements
52.80.Pi High-frequency and RF discharges

Substrate Bombardment During RF Sputtering

I. Brodie, L. T. Lamont, and D. O. Myers

J. Vac. Sci. Technol. 6, 124 (1969); http://dx.doi.org/10.1116/1.1492641 (4 pages) | Cited 8 times

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It is shown, that for the conditions relevant to the “peak” type of rf sputtering arrangement, and in fact most rf sputtering devices, that ions are essentially unaware of the existence of the rf fields and respond only to the dc fields generated. This enables the sputtering parameters to be viewed in a simple, physical way and calculations based on this approach are shown to be fairly exact. A deduction from the theory is that the majority of the secondary electrons released by ion bombardment of the target plates strike the substrate table with considerable energy. A special gridded probe in the substrate table enabled the simple theory to be verified quantitatively and also verified the existence of the high-energy electrons. By controlling substrate bombardment during sputtering with another grid arrangement, the effects of this high-energy electron bombardment on film adherence and appearance was demonstrated.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

High Capacity Sputtering Apparatus

E. C. Muly and A. J. Aronson

J. Vac. Sci. Technol. 6, 128 (1969); http://dx.doi.org/10.1116/1.1492642 (3 pages)

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The design, construction, and evaluation of a compact, economical four-element sputtering system to be used for handling quantities of substrates and multiple target materials is described. This system operates without the aid of a magnetic field. Details are also given of an accurate large area uniformity measuring technique employing interferometry which does not require the use of optical flats.
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81.15.Cd Deposition by sputtering

Problems Encountered During Deposition of Optical Thin Films with Reproducible Characteristics in an Automatic Coater

H. K. Pulker and E. Girardet

J. Vac. Sci. Technol. 6, 131 (1969); http://dx.doi.org/10.1116/1.1492643 (4 pages)

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Investigations have shown that it is possible to control optical layers with high precision by means of a quartz crystal monitor (measurement of the deposited mass). This was possible by using a very precise quartz crystal monitor and by a thorough investigation of the phenomena of condensation on the substrate and also of the effect caused by interaction of residual gas on the film during the deposition process. On the basis of this experience a fully automatic control unit has been developed which may be used for the production of optical layers as well as for electronic applications.
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81.15.Aa Theory and models of film growth
42.79.Wc Optical coatings

The Photometallic Process

J. F. Burgess and D. L. Schaefer

J. Vac. Sci. Technol. 6, 134 (1969); http://dx.doi.org/10.1116/1.1492644 (4 pages)

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The photometallic process is a new method of producing images in thin films of metals, semiconductors, and dielectrics. The process depends on the photogeneration of reactive material in situ which reacts with the thin film to produce a pattern.
A polymer layer containing a photodecomposable material is coated on a thin film. A pattern of light on the surface causes preferential photodecomposition and these products react with the thin film, removing it where exposed to light. The coating and reaction products are removed in a solvent rinse. A positive copy of the light image is thus obtained in the thin film. Since very close control of the photodecomposition is possible, images with continuous grey scale or various depths of reaction are possible. The process is exemplified by a description of the photoetching of gold, nichrome, and silicon dioxide. Other materials for which the process has been demonstrated are listed. A discussion of thin-film parameters, coating parameters, and proposed reaction mechanisms is presented. Among other applications, the process has potential use in microelectronic circuit fabrication.
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82.50.Bc Processes caused by infrared radiation
82.50.Hp Processes caused by visible and UV light

Intrinsic Stress in Evaporated Metal Films

E. Klokholm

J. Vac. Sci. Technol. 6, 138 (1969); http://dx.doi.org/10.1116/1.1492645 (3 pages) | Cited 11 times

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Recently the author proposed a model for the origin of the observed intrinsic tensile stresses in thin metal films. The model predicts a large stress S relatively independent of thickness, in films when the ratio of the melting to the substrate (absolute) temperatures, Tm∕Ts, exceeds 4. Conversely, S will be small when Tm∕Ts, is smaller than 4 and should decrease with increasing film thickness. The stress has been measured in Al, Cu, and Ni films as a function of Tm∕Ts and the data obtained verifys the above predictions. For Tm∕Ts much larger than 4, S in Al films is 2×109 dyn∕cm2; in Cu, 7×109 dyn∕cm2; and in Ni, 9×109 dyn∕cm2. As Tm∕Ts becomes less than 4 the stress in each case is small, and decreases with increasing film thickness.
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68.60.Bs Mechanical and acoustical properties
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

High Current Vacuum System For Multilayer Filter Deposition

W. L. Cornelius and J. G. Martner

J. Vac. Sci. Technol. 6, 140 (1969); http://dx.doi.org/10.1116/1.1492646 (5 pages)

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The development of a high-current vacuum system suitable for deposition of multilayer acoustical and optical filters is described. Eight interchangeable sources using either a “wick” heater, a double coil, or a basket-type heater are arranged for sequential deposition of low- and high-temperature metals and dielectrics. Electrical contacts to the sources are externally operated to change sources. A liquid N2 cold can is situated on top of the evaporating source and it serves to funnel the vapor stream toward the target. This arrangement saves time and unrecoverable material since it considerably reduces spillage of vapor on the interior.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
07.30.-t Vacuum apparatus

Deformation of Optical Surfaces by Film Stress

Richard J. Scheuerman

J. Vac. Sci. Technol. 6, 145 (1969); http://dx.doi.org/10.1116/1.1492647 (3 pages)

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The development of stress in evaporated dielectric and metal films used as optical coatings has been investigated experimentally by two interferometric techniques. Stress data on a number of materials commonly used in the coating of reflective optics are presented, and the stress behavior in coatings deposited on stationary substrates at normal incidence is compared to those deposited on rotating substrates at high angles of incidence. Analysis of the effect of film stress upon the figure of optical surfaces is given, and examples are presented illustrating how this effect may be minimized.
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68.60.Bs Mechanical and acoustical properties
42.79.Wc Optical coatings

Adhesion Mechanism of Gold-Underlayer Film Combinations to Oxide Substrates

K. E. Haq, K. H. Behrndt, and Ilse Kobin

J. Vac. Sci. Technol. 6, 148 (1969); http://dx.doi.org/10.1116/1.1492648 (5 pages) | Cited 2 times

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The adhesion between glass or oxidized Si substrates and evaporated gold films in combination with an adherent intermediate layer of Ta, Si, Ge, or Cr has been investigated. The experimental results regarding changes of adhesion as a function of the relative thickness of the Au and underlayer films as well as time, environment, and treatment after deposition are described in detail. They can be explained in terms of the thermodynamic properties of the respective Au-underlayer systems: In the case of Au–Si and Au–Ge, alloying and diffusion processes play the dominant role while, for Au–Ta, oxidation of Ta is responsible for adhesion changes. Most importantly, in the Au–Cr system, none of the above processes are effective, at least up to 450 °C. Consequently, no loss of adhesion was observed for periods of one month and thicknesses of the Cr layer of only about 10 Å.
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68.35.Gy Mechanical properties; surface strains

Electronic Structure of Clean Metallic Interfaces

C. B. Duke

J. Vac. Sci. Technol. 6, 152 (1969); http://dx.doi.org/10.1116/1.1492649 (15 pages) | Cited 3 times

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A review of the theory of clean metallic interfaces is presented. First, the contributions to the potential at a metallic interface due to bulk electron–electron, bulk electron–ion, and surface interactions, are illustrated for a metal–vacuum interface. We then review the description of this potential by phenomenological models and by dynamical models. Its description by a particular dynamical model, the local-density approximation for an electron fluid in an average positive background, is developed and compared with earlier models. The model is extended to describe bimetallic interfaces. Its major prediction is that the redistribution of charge at a bimetallic or metal semiconductor junction relative to the isolated metal–vacuum interfaces of its components causes substantial modifications of the potential at the interface. This effect suffices to describe the systematics of metal–semiconductor contacts without introducing surface states.
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73.20.At Surface states, band structure, electron density of states
73.40.Ns Metal-nonmetal contacts

Ultimate Pressure Limitations

D. G. Bills

J. Vac. Sci. Technol. 6, 166 (1969); http://dx.doi.org/10.1116/1.1492650 (8 pages) | Cited 4 times

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Present limitations on attaining low pressures are examined in detail. Evidence for the existence of pumping mechanisms at very low pressures is reviewed and it is shown that the present difficulties in achieving pressures much below 10−12 Torr in room temperature systems appear to be due to inadequate or improper processing of the system materials. Curves showing the partial pressure as a function of time and temperature for volume, surface, dissolved, and permeating gases in a typical system are given. It is concluded on the basis of present evidence that pressures in the 10−16 Torr range should be routinely possible provided the entire system is designed and operated to minimize permeation and is carefully processed to remove dissolved gases.
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07.30.-t Vacuum apparatus

Ionic Entrapment in Tungsten Monocrystals; A Survey of Effects Observed in Thermal Desorption

E. V. Kornelsen

J. Vac. Sci. Technol. 6, 173 (1969); http://dx.doi.org/10.1116/1.1492651 (2 pages) | Cited 1 time

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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics

Field Emission as a Tool for the Study of the Electronic Structure of Solids

L. W. Swanson

J. Vac. Sci. Technol. 6, 175 (1969); http://dx.doi.org/10.1116/1.1492652 (2 pages)

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79.70.+q Field emission, ionization, evaporation, and desorption
73.20.At Surface states, band structure, electron density of states

Preparation and Superconducting Properties of Thin Films of Transition Metal Interstitial Compounds

J. R. Gavaler, J. K. Hulm, M. A. Janocko, and C. K. Jones

J. Vac. Sci. Technol. 6, 177 (1969); http://dx.doi.org/10.1116/1.1492653 (4 pages) | Cited 32 times

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The importance of geometrical parameters in determining the superconducting properties of a material has recently been a topic of considerable theoretical interest. Experimental investigation in this area so far has been restricted principally to thin-film structures of the non-transition elements, compared of materials possessing relatively small superconducting non-parameters (K). In this paper we discuss some recent studies on thin-film structures of transition metal compounds having both high critical temperatures (Tc≳14 °K) and large upper critical fields (Hc2≳100 kOe). The materials in this work have the rocksalt structure (B1) and are based upon the compound niobium nitride, NbN. The films were prepared by reactive sputtering in argon-nitrogen atmospheres in an ultrahigh vacuum system with a background pressure ≲5×10−10 Torr. Variation of the nitrogen partial pressure over the range 10−3 to 10−6 Torr was used to obtain different film compositions.
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74.78.-w Superconducting films and low-dimensional structures
81.15.Cd Deposition by sputtering
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)

Magnetic “Ternary Permalloy” Memory Films

Frank M. Uno and Robert F. Vieth

J. Vac. Sci. Technol. 6, 180 (1969); http://dx.doi.org/10.1116/1.1492654 (4 pages)

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Ternary paramagnetic additions to Permalloy have been used to produce magnetic films with salient modifications of the coercive and anisotropy properties. Films from 4000 Å to 12 000 Å were deposited on glass substrates by application of electron-beam evaporation techniques. Vanadium, Gadolinium, Cobalt, Titanium, and Chromium are shown to be the most advantageous additions for selectively controlling memory characteristics (coercive force, hard axis anisotropy, and dispersion). Nondestructive readout (NDRO) and destructive readout (DRO) memory subsystems have been designed and built using these films in conjunction with a ferrite keeper. The NDRO memory employs an ultralow dispersive read film which utilizes vanadium, and a storage film with high coercivity containing cobalt. The DRO memory eliminates the storage film and operates with a modified read film.
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75.50.Ss Magnetic recording materials
75.70.Ak Magnetic properties of monolayers and thin films
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Electrical Properties of Titanium, Zirconium, and Hafnium Films from 300 °K to 1.3 °K

P. E. Friebertshauser and J. W. McCamont

J. Vac. Sci. Technol. 6, 184 (1969); http://dx.doi.org/10.1116/1.1492655 (4 pages) | Cited 1 time

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Electrical properties of titanium, zirconium, and hafnium films prepared by electron beam evaporation have been measured from 300 °K to 1.3 °K as a function of substrate temperature, film thickness, and substrate material (single-crystal sapphire, Corning 7059 glass, and fused quartz). Zirconium films in the thickness range 2000 Å to 12 000 Å have superconductive transition temperatures near 1.3 °K for films deposited at substrate temperatures of 100 °C and below. Expitaxial growth of titanium is observed on single-crystal sapphire substrates in the temperature range 200 °C to 400 °C on at least two orientations of sapphire. Epitaxial titanium films have a resistance ratio (R300 °K∕R4.2 °K) of 24 at a thickness of 12 000 Å and of 8 at 400 Å. This is nearly twice those of the corresponding polycrystalline films on Corning 7059 glass or fused quartz. Films of zirconium and hafnium have an enhanced resistance ratio on sapphire substrates only when deposited at a substrate temperature of 400 °C. Their resistivities at 300 °K are about twice the bulk values for films 7000 Å thick or greater. Superconductivity was not observed for either titanium or hafnium films down to 1.3 °K. Only the hexagonal close-packed crystal structure was found for all three film materials.
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73.61.At Metal and metallic alloys
74.78.-w Superconducting films and low-dimensional structures
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Complex Impedance Characteristics of Low-Resistance Bismuth Films

Lorn L. Howard

J. Vac. Sci. Technol. 6, 188 (1969); http://dx.doi.org/10.1116/1.1492656 (6 pages)

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A structure-determined electrical impedance in the infrared region between 2 and 15 μ was postulated for thin bismuth films a few years ago and an equivalent circuit was determined for films having initial resistances of 90 Ω∕square. The circuit was derived from resistance and infrared transmission measurements. Theory developed subsequently indicated that if reflectance measurements also could be made and if these measurements gave values falling within a certain range, the postulated impedance could be established with certainty. These measurements have been made; the theory and the data are presented. In addition, equivalent circuits are given for films having initial resistance values lying between 34 and 300 Ω∕square.
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73.61.At Metal and metallic alloys
78.66.Bz Metals and metallic alloys

Destructive Breakdown in Thin Films of SiO, MgF2, CaF2, CeF3, CeO2, and Teflon

Paul P. Budenstein, Paul J. Hayes, J. Lynn Smith, and Wallace B. Smith

J. Vac. Sci. Technol. 6, 193 (1969); http://dx.doi.org/10.1116/1.1492657 (2 pages)

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Abstract Unavailable
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77.22.Jp Dielectric breakdown and space-charge effects
77.55.-g Dielectric thin films

Dielectric Properties of Reactively Sputtered Films of Aluminum Nitride

A. J. Noreika, M. H. Francombe, and S. A. Zeitman

J. Vac. Sci. Technol. 6, 194 (1969); http://dx.doi.org/10.1116/1.1492658 (4 pages) | Cited 21 times

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Films of AlN, up to 5 μ in thickness, have been grown by diode reactive sputtering under conditions in which the initial residual gas pressure was less than 10−9 Torr. Measurements of resistivity, capacitance, and dielectric loss were made on film sandwich structures in which the electrodes were sputtered films of tantalum and evaporated films of gold and aluminum. In general, the dielectric properties were superior to those reported for ceramic AlN, with film resistivities in the range 1013 Ω-cm and dissipation factors lower than 0.005. Measurements could be made on samples with tantalum electrodes at temperatures up to 500 °C. The results indicate that the capacitance and dissipation factor show smaller changes with temperature for the sputtered films than for bulk material. Some of the consequences of the film structure in relation to dielectric breakdown and piezoelectric properties are discussed.
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77.55.-g Dielectric thin films
73.61.Ng Insulators
77.22.Gm Dielectric loss and relaxation
81.15.Cd Deposition by sputtering

Effect of Ultrahigh Vacuum on the Friction between Metals and Granular Soils

Leslie L. Karafiath and George Mohr

J. Vac. Sci. Technol. 6, 198 (1969); http://dx.doi.org/10.1116/1.1492659 (4 pages) | Cited 1 time

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An apparatus has been developed to measure the friction between metals and granular materials in ultrahigh vacuum. Pressures below p=10−9 Torr have been routinely reached with the vacuum system consisting of a turbomolecular, a getter-ion, and a liquid-N2-cooled titanium sublimation pump. The frictional resistance between steel and ground basalt in two particle size ranges was measured under various normal loads. The experiments showed that the ultrahigh vacuum did not affect the coefficient of friction significantly, but increased the frictional resistance by an adhesion ranging from 6 to 24 g∕cm2 for the various materials and conditions.
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62.20.Qp Friction, tribology, and hardness
07.30.-t Vacuum apparatus

Vacuum System for High-Radiation Environment at the RPI Linac Laboratory

J. Haken, J. F. Lewis, and R. J. Krasse

J. Vac. Sci. Technol. 6, 202 (1969); http://dx.doi.org/10.1116/1.1492660 (3 pages)

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Vacuum system components on the RPI Linear Accelerator must operate in radiation fields averaging 5×105 rad∕sec. Experience gained since the start of operations eight years ago indicates the special problems of constructing, maintaining, and modifying systems for high-radiation environments.
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29.20.-c Accelerators
07.30.-t Vacuum apparatus

Performance of a Large Vacuum Chamber During a Continuous 10 000-h, 2200 °F Materials Test

C. W. Cunningham

J. Vac. Sci. Technol. 6, 204 (1969); http://dx.doi.org/10.1116/1.1492661 (5 pages)

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A 4-ft-diam by 12-ft vertical vacuum chamber was operated at 1–5×10−8 Torr to contain a 10 000-h, 2200 °F boiling-potassium refractory metal test. This test required what is believed to be a record 11 000 h of continuous operation of a large size sublimation and getter-ion pumped chamber containing high-temperature test equipment. Sublimation pumping capacity of 20 000 liters∕sec and ion pumping capacity of 2400 liters∕sec were provided. An unexpected exponential increase in ion pump current from 0.35 to 35.0 mA in 8500 h was experienced before “hi-potting” and alternate operation of the two ion pumps was used to reduce the current increase. This test unexpectedly demonstrated that during long term operation, excessive ion pump currents may force early pump maintenance or cause premature test termination. Argon, nitrogen, and hydrogen remained the principal gases throughout the test period. Lesser amounts of methane and carbon dioxide were present. Other organic compounds and water remained at, or decreased to, very low concentrations.
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07.30.Kf Vacuum chambers, auxiliary apparatus, and materials

Optical Surface Degradation from Combined Ultraviolet Radiation and Outgassed Materials

J. F. Scannapieco and R. N. Griffin

J. Vac. Sci. Technol. 6, 209 (1969); http://dx.doi.org/10.1116/1.1492662 (6 pages)

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Among problems, which have been encountered in testing and flight of spacecraft, have been those related to the outgassing of materials in vacuum. Two of the major problems caused by outgassing are electrical corona discharge, and condensation onto critical surfaces. The surfaces of a spacecraft most susceptible to damage by condensation of a foreign material are those used for thermal control and those used in optical systems. This paper describes the techniques used to determine the effects of outgassed materials condensed on MgF2 over-coated aluminum mirrors while the mirrors were irradiated with ultraviolet light in vacuum. Mirror temperatures as low as −60 °C were used to determine the point at which condensation was incipient. The measurements performed on these mirrors included reflectance at Lyman α (1216 Å) and infrared analysis of the deposit. The initial results obtained with this system demonstrate that Lyman α reflectance is essentially unaffected by heavy condensates of some materials but almost completely destroyed by very thin deposits of other materials.
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07.87.+v Spaceborne and space research instruments, apparatus, and components (satellites, space vehicles, etc.)
42.70.-a Optical materials

Phonic Desorption

Dean R. Denison

J. Vac. Sci. Technol. 6, 214 (1969); http://dx.doi.org/10.1116/1.1492663 (4 pages) | Cited 3 times

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The desorption of materials from the walls of a vacuum vessel by means of phonic energy has been observed. To study this effect and its application to improved pumpdown of nonbakeable systems, an ultrasonic transducer was attached to a small system and the desorption products observed with a quadrupole gas analyzer. Water vapor, CO, CO2, and hydrocarbons were observed to desorb. The apparatus and results are presented with a simple theory that describes the results.
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68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
43.35.-c Ultrasonics, quantum acoustics, and physical effects of sound
07.30.Bx Degasification, residual gas

Outgassing of Multifoil Insulation Materials in Sealed Vacuum Systems

R. L. Reid, W. D. DeWitt, and N. C. Gibbon

J. Vac. Sci. Technol. 6, 217 (1969); http://dx.doi.org/10.1116/1.1492664 (5 pages)

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Multifoil vacuum insulation systems provide maximum thermal protection with a minimum of insulation. In order to obtain the maximum thermal performance in such systems, a good vacuum level must be maintained with the insulation system. In order to determine the amount of getter required to maintain the vacuum environment, the rate of offgassing of the insulation materials must be known. This paper presents the results of offgassing rate measurements on typical multifoil insulation materials in the temperature range of 100 ° to 1800 °F. Rates were determined for aluminum foil, tantalum foil, nickel foil, copper foil, glass-fiber paper, aluminum-opacified glass-fiber paper, quartz paper, copper-opacified quartz paper, and quartz cloth. These materials were subjected to periods of vacuum pumping at temperatures 100 °F in excess of the offgassing measurement temperatures. The composition of the offgas was also measured. The 100 °F over-temperature bakeout was generally effective in suppressing the offgassing rates to acceptably low levels. Because of the bakeout period, some materials became adsorbers when the temperature was reduced. All rates are presented as a function of the time of pumping at the over-temperature so that the length of the bakeout period can be determined for a given desired offgassing rate.
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07.30.Kf Vacuum chambers, auxiliary apparatus, and materials

Dynamical Origin of Three-Dimensional Low-Energy Electron Diffraction Intensities

R. M. Stern, H. Taub, and A. Gervais

J. Vac. Sci. Technol. 6, 222 (1969); http://dx.doi.org/10.1116/1.1492665 (2 pages)

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61.05.jd Theories of electron diffraction and scattering

Sticking Probability of Atomic Hydrogen on Graphite

George A. Beitel

J. Vac. Sci. Technol. 6, 224 (1969); http://dx.doi.org/10.1116/1.1492666 (5 pages) | Cited 2 times

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Standard ultrahigh vacuum and flash filament techniques were used to measure the sticking probabilities of atomic and molecular hydrogen sH and sm, respectively, on graphite. Atomic hydrogen was produced by a hot tungsten filament. Graphite samples were specially fabricated ribbons which could be flashed to 2500 °K. The quantity of atomic hydrogen sorbed was found to be only dependent on the temperature of the graphite and the total number of incident hydrogen atoms. Thus it is possible to use a graphite ribbon as an atomic hydrogen detector.
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68.43.-h Chemisorption/physisorption: adsorbates on surfaces
07.30.Bx Degasification, residual gas

Adsorption Of Nitrogen, Hydrogen, Oxygen, and Carbon Monoxide on a Beryllium Film

J. T. Hurd and R. O. Adams

J. Vac. Sci. Technol. 6, 229 (1969); http://dx.doi.org/10.1116/1.1492667 (5 pages) | Cited 4 times

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Results of measurements of sticking coefficients of nitrogen, hydrogen, oxygen, and carbon monoxide on beryllium thick films at room temperature are described. Beryllium was vapor deposited onto glass substrates and the sticking coefficient of the impinging gas molecules was measured as a function of quantity adsorbed. No adsorption was observed with either nitrogen or hydrogen. A sticking coefficient of 0.4 for oxygen was measured with a total coverage of 8.4×1014 molecules∕cm2. Carbon monoxide displayed some pressure dependence and the initial sticking coefficient was found to be roughly proportional to the square root of the pressure. In the 10−8 Torr range a sticking coefficient of 0.1 was measured with a total coverage of 4.0×1013 molecules∕cm2; in the 10−7 Torr range a sticking coefficient of 0.5 was measured with a total coverage of 2.4×1014 molecules∕cm2.
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68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Electrostatic Charge Distribution on Ultrahigh Vacuum Cleaved Silicates

J. J. Grossman

J. Vac. Sci. Technol. 6, 233 (1969); http://dx.doi.org/10.1116/1.1492668 (4 pages)

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Recent measurements of relatively strong long-range electrostatic attractive forces, produced by ultrahigh vacuum cleavage of silicates, prompted the design and fabrication of a special UHV system to measure the charge distributions. The system is described in this paper, together with preliminary results from the experiment. Charge distributions found to date have varied from dipolar to octapolar shapes on the face of cylindrical samples in excess of 1 esu∕cm2. A relationship appears to exist between the orientation of the multipolar distributions and the crystallographic axes. Results from the first cleavages of orthoclase (nominally, KAlSi3O8) at 10−10 Torr indicate that there are at least two discharging mechanisms: first, the charge decays to one half its initial (extrapolated to zero) value in 1.5 h due to gas adsorption; second, it then decays very slowly with a half-life of at least 76 days. Irradiation with uv light causes discharge. When the pressure in the system is raised towards atmospheric with dry nitrogen, the charge is stable (to a first order of approximation) up to pressures in the 10-μ range. Discharge in bursts, as the pressure is raised, is readily explained by the Paschen sparking potential relation for gaseous discharges.
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77.22.-d Dielectric properties of solids and liquids

Origin of the Angular Dependence of Secondary Emission of Electrons

H. Taub and R. M. Stern

J. Vac. Sci. Technol. 6, 237 (1969); http://dx.doi.org/10.1116/1.1492669 (1 page) | Cited 3 times

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Abstract Unavailable
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79.20.Hx Electron impact: secondary emission

Adsorption of Nitrogen on a Pyrex Glass Surface at Very Low Pressures

Y. Tuzi and T. Saito

J. Vac. Sci. Technol. 6, 238 (1969); http://dx.doi.org/10.1116/1.1492670 (4 pages) | Cited 3 times

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The adsorption of nitrogen on a Pyrex glass surface has been studied in the region of 77 ° to 120 °K by using a dynamic method. The relation among the amount of adsorption (109∼1013 molecules∕cm2), the temperature, and the pressure are well expressed by the Dubinin-Radushkevich equation. Analysis of desorption curves gives the activation energy of desorption Ed as a function of the amount of adsorption, and sτ as a function of temperature, where s and τ are the condensation coefficient and the mean adsorption time of nitrogen molecules, respectively. For example, Ed is ca. 6 kcal∕mole at the amount of adsorption of 1×1010 molecules∕cm2 and sτ is ca. 0.1 sec at 90 °K.
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68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics

Auger Electron Spectrometer as a Tool for Surface Analysis (Contamination Monitor)

Norman J. Taylor

J. Vac. Sci. Technol. 6, 241 (1969); http://dx.doi.org/10.1116/1.1492671 (5 pages) | Cited 2 times

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The advances in reliable ultrahigh vacuum systems and techniques over the past ten years have made it possible to maintain a solid surface in an environment in which minimum monolayer formation times are of the order of many hours or even days. As a result, increased emphasis is now being placed on the preparation of clean surfaces or surfaces of known composition. Such preparation is necessary prior to the meaningful study of the various properties of the surface, either crystallographic or electronic. The practical applications of such studies may be found, for example, in photoemitters, secondary emitting surfaces, and thermionic emitters. By means of Auger electron analysis it is becoming increasingly possible to determine the composition of surface contaminants. With such knowledge, appropriate cleaning procedures may be employed and their effectiveness monitored. After briefly describing the Auger effect and a practical spectrometer based on electron bombardment induced Auger emission, some experiments on surface treatment and analysis are described. Observations are made on 304 stainless steel, gallium arsenide, and tungsten.
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07.81.+a Electron and ion spectrometers
61.05.-a Techniques for structure determination

Causes and Consequences of Nonuniform Gas Distributions in Vacuum Systems

Boude C. Moore

J. Vac. Sci. Technol. 6, 246 (1969); http://dx.doi.org/10.1116/1.1492672 (9 pages) | Cited 2 times

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The term “nonuiform gas distributions” refers to the variation of flux, density, and pressure with position in a vacuum system. Six common causes of nonuniformity are listed. Diffuse reflections cannot always be assumed. An approximate analysis of cylindrical systems is presented, based on iteration of Clausing’s flux patterns for open-ended tubes. The method allows rapid comparison of flux uniformity for alternate geometries. The disturbances in the patterns caused by orifice inlets and by orifice pumps are estimated. Spherical geometries are contrasted with cylindrical; the flux being not only uniform over a sphere, but calculated with greater certainty.
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07.30.-t Vacuum apparatus

Measuring Small Gas Flows Into Vacuum Systems

Charles E. Hawk and William C. Baker

J. Vac. Sci. Technol. 6, 255 (1969); http://dx.doi.org/10.1116/1.1492673 (3 pages) | Cited 4 times

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A description of a new mass flowmeter for measuring small flow rates into vacuum systems on a continuous, direct reading, and instantaneous basis. The theory, operation, and characteristics are described including typical performance results in practical applications.
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07.30.Kf Vacuum chambers, auxiliary apparatus, and materials
47.80.-v Instrumentation and measurement methods in fluid dynamics

Surface Smoothness in Thermal Transpiration at Very Low Pressures

J. P. Hobson

J. Vac. Sci. Technol. 6, 257 (1969); http://dx.doi.org/10.1116/1.1492674 (3 pages) | Cited 12 times

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The thermal transpiration ratio for helium has been measured by the absolute method with a leached pyrex tube joining the cold and hot regions. Cold temperature was T1=77.4 °K, hot temperature T2=295 °K, pressure range 10−7 to 100 Torr. The results agreed closely with those obtained when an aperture joined the cold and hot regions. In particular, the ideal limiting law P1∕P2=(T1∕T2)1∕2 was found at very low pressures, P1 and P2 being the pressures at T1 and T2 respectively. This result is in contrast to that found with smooth Pyrex tubes where unpredictable deviations from the ideal law were found. It is concluded that leaching the surface produces atomic roughness which forces all reflections to be cosine reflections, leading to the ideal law. The use of a leached tube permits precise thermal transpiration corrections in simple glass apparatus. The glass was leached for 100 h at 100 °C in 0.05 N HCl.
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47.60.-i Flow phenomena in quasi-one-dimensional systems
47.45.Dt Free molecular flows

Inverse Pressure Dependence of the Quadrupole Ionization Gauge

Helmut Schwarz and H. A. Tourtellotte

J. Vac. Sci. Technol. 6, 260 (1969); http://dx.doi.org/10.1116/1.1492675 (3 pages)

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A nonmagnetic ionization gauge has been developed in which electrons are oscillating back and forth along the axis of the tube as in a Penning type ion gauge. The electrons are emitted from a hot hairpin filament at one side of a cylindrical tube and are accelerated by a dc potential of 27 V towards the other end. At the other end there is a disk-shaped electrode which has the same potential as the cathode. This causes the electrons to travel back and forth between the ends until they suffer a collision. A quadruple system serves to keep the electrons from reaching the electrodes and the wall. The system is excited by a rf oscillator of 200 MHz and 165 V peak voltage which is tuned in such a way that only electrons will not deviate from stable trajectories along the center of the tube. A closed screen surrounds the whole electrode structure. It is at a slightly negative potential and serves as the ion collector. Within the pressure range p=10−5 to 10−10 Torr the ion current i follows the relationship pin=c. n was found to be 1.31 ± 0.02 for electron emissions of 10, 50, 100, and 500 μA. The constant c was c=2.88×10−17 for 10 μA, 2.63×10−16 for 50 μA, and in the case of 100 μA it was 5.37×10−15.
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07.30.Dz Vacuum gauges

High Vacuum Pump for Removing Water During Industrial Processes

R. V. D. Strong and Charles Francksen

J. Vac. Sci. Technol. 6, 263 (1969); http://dx.doi.org/10.1116/1.1492676 (3 pages)

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Industrial processes frequently require the use of vacuum to remove water from products at reduced temperatures and pressures. Rotary oil-sealed pumps are often used for this duty, but unless auxiliary equipment is utilized the pumps load up with water and cannot reach required final low pressures. A new modification of the rotary oil-sealed pump incorporating special construction details, insulation to prevent undue heat loss, special lubricating and sealing fluid, and a packaged oil-temperature heating and chilling unit with oil-circulating pump and automatic oil-temperature control, now provides a unit capable of removing water from a process at any pressure level. This pump is capable of reaching final pressures well below 100μ without the use of auxiliary equipment, and can handle any water load within pump capability at all pressure levels up to 1 atm.
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07.30.Cy Vacuum pumps

Backstreaming Measurements Above Liquid-Nitrogen Traps

M. H. Hablanian

J. Vac. Sci. Technol. 6, 265 (1969); http://dx.doi.org/10.1116/1.1492677 (4 pages) | Cited 1 time

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Gravimetric measurements of diffusion-pump backstreaming rates were made above liquid-nitrogen-cooled traps. Experiments were made of over 500-h duration, with 6-in. and 35-in. pumps, with and without a water-cooled baffle and a creep barrier. The surfaces collecting the backstreaming oil were cooled to liquid-nitrogen temperature to prevent errors due to re-evaporation. Design compromises are discussed as related to the requirement of maximum pumping speed and minimum backstreaming. The results indicate that opaque water-cooled baffles have substantial redundancy in the design. A combination of a water-cooled partial baffle, a liquid-nitrogen trap, and a special cold cap over the upper nozzle is described, which permits important improvements in system speed without significant increase in the backstreaming rate.
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07.30.Cy Vacuum pumps

Observations of Reactions in Solids and Formation of Surface Layers with the Emission Electron Microscope

Ch. Zaminer, R. Graber, and L. Wegmann

J. Vac. Sci. Technol. 6, 269 (1969); http://dx.doi.org/10.1116/1.1492678 (4 pages)

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In an emission electron microscope the grain growth of a tungsten wire and the reaction with oxygen and hydrocarbons at high temperatures are observed using thermionic emission. Below the thermionic temperature range the reaction between evaporation layers of thin films was studied with photoemission micrographs.
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79.40.+z Thermionic emission
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.37.-d Microscopy of surfaces, interfaces, and thin films
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