Classified abstracts 779–920

Classified abstracts 779-920 Classified abstracts 779-785 on this page

Editor's note

The label immediately following the title of each item denotes country or origin of publication, and that at the end of each abstract indicates country of origin of work (where known).

I. General v a c u u m science and engineering 14. KINETIC THEORY O F GASES 14 779. Causes and consequences of non-uniform gas distributions in vacuum systems.* (USA) The term "non-uniform gas distributions" refers to the variation of flux, density, and pressure with position in a vacuum system. Six common causes of non-uniformity 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 alternative 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. C Moore, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 246--254. 14 780. Surface smoothness in thermal transpiration at very low pressures.* (USA) 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 Tz=77.4°K, hot temperature T~= 295°K, pressure range 10-' to 100 torr. The results agreed closely with those obtained when an aperture joined the cold and hot regions. In particular, the ideal limiting low PJP2=(T,/T2)t/2 was found at very low pressures, P, and P2 being the pressures at T, and Ts 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 HCI. J P Hobson, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 257-259. 14 781. The velocity distribution after impact for molecules having very different masses. (Germany) Oil molecules in the vapour jet of a diffusion pump have a collective velocity superimposed on the Maxwellian thermal velocity distribution. The velocity distribution after collision with a gas molecule of much smaller mass is of importance in the comprehension of the effect of a diffusion pump. Calculations using a rigid-elastic sphere model for molecules of very different masses, indicate that lighter gas molecules would have a distribution after one impact which is practically MaxweUian, if the system considered has the collective velocity corresponding to that of an oil vapour jet. M Wutz, Vakuum-Technik, 17 (8), Oct 1968, 193-202 (in German). 16. GASES AND SOLIDS 16 : 21 Influence of the temperature history of condensed argon on its hydrogen adsorptivity at low temperatures. See abstract number 815. 16:22 Mass spectrometric investigation of the ion desorption in U H V gauges. See abstract number 829. 16 : 34 Adsorption and the loss of Moon's atmosphere. See abstract number 904.

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782. Diffusion of nitrogen through Zr-AI alloys in vacuum.* (USA) Sorption of nitrogen by a Zr-AI alloy has been measured at constant temperature (300°C and 500°C) and for nitrogen pressures in the range l i f e to 1 torr. The pumping speed of the Zr-AI 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, eg 10 .6 torr. During this recovery process nitrogen compounds at the surface migrate towards the interior of the Zr-AI 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 behaviour of Zr-AI based getter pumps during and after high throughput applications. P della Porta et al, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 40-44. 16 : 21 783. Impurity effects on heterogeneous nucleation from the vapour I U mercury on Pyrex glass.* (USA) The thermal accommodation coefficient (TAC) and critical supersaturation for nucleation (act) of mercury vapour on Pyrex glass were studied over a wide range of vapour pressure and temperature conditions for both rigorously outgassed blown Pyrex surfaces, and for the same surfaces contaminated by the adsorption of water vapour or CO. Measurements were made by observing mass spectrometrically the mercury vapour flux leaving a substrate exposed to a flux of mercury atoms from a static vapour at fixed temperature and pressure. By appropriate manipulation of the substrate temperature both the TAC and a= could be measured at essentially the same time and under identical conditions of vapour pressure, vapour temperature, and substrate contamination. Observed values of the TAC ranged from 0.6 to 1.0 depending on substrate condition. The a= ranged from slightly more than unity to about seven over the temperature range from 263°K to 225°K. Impurity adsorption generally increased act, but not greatly. Results are interpreted in terms of the effect of impurity adsorption on the TAC and the substrate-nucleus contact angle. A Kinawi and J B Hudson, J Vac Sci Technol, 6 (1), Jan-Feb, 1969, 6873. 16 784. Adsorption of nitrogen on a Pyrex glass surface at very low pressures.* (USA) 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 relations between the amount of adsorption (10~-10 ta molecules/cm*-), the temperature, and the pressure are well expressed by the DubininRadushkevich equation. Analysis of desorption curves gave the activation energy of desorption as a function of the amount of adsorption (6Kcal/mole at an adsorption of 1 × 10 t° molecules/cm ~) and the product of the condensation coefficient and the mean adsorption time was obtained as a function of temperature (0.1 see at 90°K). Y Tuzi and T Saito, J Vac Sci Technol, 6 (I), Jan-Feb 1969, 238-240. 16 : 37 785. Nonequilibrium chemical reactivity of polycrystalline iron foils.* (USA) It is shown that continuous oxide films form on iron specimens in contaminated hydrogen atmospheres in which the metal is the 377

Classified abstracts 786-797 thermodynamically favoured 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. T Gabor and J M BIocber, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 73-78. 16:47 786. Phonic desorption.* (USA) The desorptlon 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 non-bakeable systems, an ultrasonic transducer was attached to a small system and the desorption products observed with a quadrupole gas analyzer. Water vapour, CO, COs, and hydrocarbons were observed to desorb. The apparatus and results are presented with a simple theory that describes the results. D R Deaison, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 214-217. 16 787. Sticking probability of atomic hydrogen on graphite.* (USA) Standard ultrahigh vacuum and flash filament techniques were used to measure the sticking probabilities of atomic and molecular hydrogen 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. G A Beitel, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 224-228. 16 788. Adsorption of nitrogen, hydrogen, oxygen, and carbon monoxide on a beryllium film.* (USA) Results of measurements of sticking coefficients of nitrogen, hydrogen, oxygen, and carbon monoxide on beryllium thick films at room temperature are described. Beryllium was vapour 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 × 10t4 molecules/cm ~. 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-e torr range a sticking coefficient of 0.1 was measured with a total coverage of 4.0 × 10ta molecules/cm=; in the 10-7 torr range a sticking coefficient of 0.5 was measured with a total coverage of 2.4× 10~4 molecules/cm =. J T Hurd and R O Adams, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 229233. 16 789. Observations of reactions in solids and formation of surface layers with the emission electron microscope.* (USA) 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. C Zaminer et al, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 269-272. 16 790. Adsorption of Cs on tungsten: measurements on single-crystal planes. (USA) Measurements were made with an emission tube using a 10-stage Cu-Be dynode electron multiplier and a simple bellows arrangement for moving the emitter. The adsorption of immobilely deposited and thermally equilibrated Cs layers was studied on the (110), (211), (100), (111), (103) and (115) regions of a tungsten field emitter. The workfunction-vs- coverage data permit resolution into absorbate charge and effective dipole length, at least on the high work-function planes. The results indicate ionic adsorption on (110) and probably (211) at low coverage, with charge diminishing on all planes as 0 increases. Z Sidorski et al, J Chem Phys, 50 (6), 15 March 1969, 2382-2391. 378

16 791. Adsorption of CO on tungsten: field emission from single planes. (USA) These measurements were carried out with an emission tube with initial pressures below 10-8 torr and with CO admitted at approximately 20 torr. Four types of measurements were carried out: workfunction changes on heating full virgin (20°K) layers; redosing of heated virgin layers; incremental dosing at 100°K; and onset of CO diffusion into various crystallographic regions. T Engel and R Gomer, J Chem Phys, 50 (6), 15 March 1969, 2428-2437. 16 792. Role of work function in electron ejection by metastable atoms. Helium and argon on (111) and (110) tungsten. (USA) A tungsten single crystal, cut to expose the (I 11) and (110) planes, was used to examine the influence of the work function on electron ejection by beams of helium or argon metastable atoms. The (111) and (110) planes have work functions that differ by about 1.5 eV. The electron yield of the (111) surface, with incident helium metastable atoms, is about 1.5 ~ higher than that of the (110) surface, while with argon the difference is about 4~o. The ejected-electron energy distributions are discussed. D A MaeLennan and T A Delchar, J Chem Phys, 50 (4), 15 Feb 1969, 1772-1778. 16 793. Adsorbate effects in electron ejection by rare-gas metastable atoms. (USA) The effect of adsorbed-gas layers on the ejection of electrons by raregas metastable atoms was studied for the (11 I) and (110) planes of a tungsten single crystal. The ejected-electron yields are discussed for nitrogen, carbon monoxide and hydrogen as adsorbates. The results a;e discussed in terms of a model in which bonding electrons from the adsorbed atom participate in the ejection process, the degree of participation depending on the surface density of the adsorbed atoms as well as their size and position on the surface. T A Deicbar et al, J Chem Phys, 50 (4), 15 Feb 1969, 1779-1787. 16 794. Gas adsorption studies on the (100) plane of vanadium by lowenergy electron diffraction. (USA) Gas adsorption studies were conducted on the (100) plane of a vanadium single crystal using low-energy electron diffraction (LEED). The crystal was exposed to hydrogen and to oxygen, in the pressure range from 10-6-10 9 torr, with the substrate held at temperatures between 25°-1400°C. A number of conclusions are summarized, including the fact that adsorption of hydrogen is random, ie, amorphous, the adsorption of oxygen is ordered, a (1 x 1) structure is formed and when the temperature is raised to II00°C, a ( 2 × 2 ) structure is formed. Other effects due to heating are discussed. K K Vijae and P F Packman, J Chem Phys, 50 (3), 1 Feb 1969, 13431349. 16 795. Automatic weighing of adsorbed gases, evaluation of surface area and pore size distribution. (Great Britain) An automatic apparatus has been constructed for weighing in different atmospheres at pressures between 10 -e torr and 1000 torr and temperatures between 76 and 1500°K. In the pressure range between 10 mtorr and 800 torr an adsorption isotherm can be measured in 100 isobaric steps upwards, and subsequently the desorption isotherms can be determined by the same stepwise measurement downwards. (W Germany) E Robens and G Sandstode, J Sci Instrum, Set 2, 2 (4), 1969, 365-368. 16:47 796. Re-deposition of vacuum outgassed products. (USA) A quartz crystal microbalance with a sensitivity of 10-gg/cm 2 is used to determine the quantity of material re-deposited from an outgassing material source in a vacuum environment. The vacuum system used is free of organic background. Results of test on 18 materials are presented. C S Griner, Rep NASA-TM-X-53801, Nov 1968, 42 pages (Sci Tech Aerospace Reps, 7 (4), 617, N69-14242). 16 : 33 797. Experimental investigation of gas-surface re-emission distribution using continuum source molecular beam techniques. (USA) Experimental studies of wall re-emission distributions are described for argon, helium, and nitrogen gas beams incident on the (1(30) planes of single crystal aluminium, silver and lithium fluoride.

Classified abstracts 798-810 Effective re-emission temperatures were found to depend on reflection angle. K Jakus, Rep AS-68-7, Sept 1968, 177 pages (Sci Tech Aerospace Reps, 7 (4), 651, N69-14816). 18. GASEOUS ELECTRONICS 18:22 X-ray emission in the energy range 100 eV-1000 eV. See abstract number 834. 18 798. Mass spectrometric sampling of glow discharges.* (USA) Continuous mass spectrometric sampling of the transient behaviour of various gas species from a d c glow discharge originally filled with CO=, and mixtures of CO=-H=, (pressure range 50-1000 p, 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 programme to investigate the gaseous electronics aspect of sealed CO= laser operation. J J Sullivan and R G Buser, J Vac Sci Technol, 6 (I),Jan-Feb 1969,103108. 18 799. An investigation of the electrical breakdown of a plasma-electrode system. (Great Britain) Electrical breakdown between a pair of electrodes immersed in a flowing plasma corresponds to the transition between low- and highcurrent conduction regimes. In the work reported, which involved cold electrodes in contact with the plasma produced by an electromagnetic shock tube, it was found that the minimum breakdown voltage corresponds to 2 MV cm -1 over a wide range of plasma conditions. D G Fearn, Brit J Appl Phys, Ser 2, 2 (4), 1969, 527-533. 18 800. A theoretical model for gas separation in a glow discharge: Cataphoresis. (USA) A theoretical model for transient and steady-state cataphoresis is developed starting with the macroscopic equations of continuity. It is found that the steady-state separation increases with decreasing initial impurity concentration. F H Shair and D S Remer, J Appl Phys, 39 (12), 1968, 5762-5768. 18 801. Dynamic sheath growth in a mercury plasma. (Great Britain) The growth of a positive ion sheath has been measured in a mercury plasma of density 101°-1014 cm -=. The sheath was formed on a plane electrode, the potential of which changed at a rate of up to 3 kV ps -1 and reached a maximum value of 10 kV. R H Varey and K F Sander, BritJApplPbys, Set 2, 2 (4), 1969, 541550. 18 802. A plasma jet as cathode for an argon laser. (Great Britain) The construction and some operational characteristics of an argon laser in which the discharge operates between a water-cooled copper anode and a plasma jet which acts as a cathode is described. A Maitland, Brit J Appl Phys, Ser 2, 2 (4), 1969, 535-539. 18 803. Instantaneous electron temperature in a mercury-argon ac discharge. (Great Britain) Measurements have been made of the instantaneous electron temperature in the positive column of a mercury-argon discharge operated at a constant discharge current of 0.23 A from 150 to 6000 Hz ac supplies. Modulation of the electron temperature with twice the frequency of the power source was obtained in the same phase, but with a small percentage modulation, as compared with that of the light output. (Japan) K Husebe, Brit J ApplPhys, Set 2, 2 (4), 1969, 611-612. 18 804. Vacuum ultraviolet radiation emitted from arc-jet plasmas of argon or nitrogen. (USA) Vacuum ultraviolet emission in the range from 2000 to 700 A was observed for both argon and nitrogen plasmas, produced by a Gerdien-type arc-jet freely expanding into a vacuum cell. The experi-

mental set-up centres about a simple, one-metre, concave grating spectrograph mounted within a tank purged with helium. G E Staats et al, Rep AD-675552, Oct 1968, 51 pages (Sci Tech Aerospace Reps, 7 (2), 353, N69-11857). 18 805. An investigation of radio frequency plasmoid discharges. (USA) A proposed model of the dark sheath observed in low pressure rf discharges in electronegative gases is developed. This model is based on the concept of delayed emission of excited ions allowing these ions to be swept from certain regions of the discharge where the static field is large before radiative excitation can occur. M D Kregel, Rep New Mexico State Univ, Univ Microfilms No 685524, 101 pages (Sci Tech Aerospace Reps, 7 (2), 351, N69-11434). 18:33 806. A new technique for measurements of radial distribution of excited species in plasmas and its application to capillary discharges in argon. (USA) The paper describes a novel technique for obtaining the radial profiles of individual emission lines from a plasma directly in the form of a recorded trace of intensity vs radial position. The special resolution and instrumental distortion effects are discussed. C E Webb, J Appl Phys, 39 (12), 1968, 5441-5470. 18 807. Space-charge wave propagation in cylindrical plasma columns. (USA) A theoretical and experimental study of space charge wave propagation in the positive column of a cesium arc discharge which was coaxially centred in a slotted waveguide is presented. Measurements on the temperature and calculations on the pressure and degree of ionization indicated the positive column to be very weakly ionized and at low pressure. G A Articolo, Rep Temple Univ, Univ Microfihn No 68-4496, 336 pages (Sci Tech Aerospace Reps, 7 (2), 354, N69-11952).

II. Vacuum apparatus and auxiliaries 20. P U M P I N G SYSTEM 20 808. Ultimate pressure limitations.* (USA) 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 material. 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. D G Bills, J Vac Sci Techno/, 6 (I), Jan-Feb 1969, 166-173. 20 809. Vacuum system for high-radiation environment at the RPI Linac laboratory.* (USA) Vacuum system components on the Linear Accelerator at the Rensselaer Polytechnic Institute, New York, must operate in radiation fields averaging 5 x 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. J l-laken et al, J Vac Sci Technol, 6 (l), Jan-Feb 1969, 202-204. 20 810. Performance of a large vacuum chamber during a continuous 10,000-h, 2200°F materials test.* (USA) A 4-ft-diameter by 12-ft vertical vacuum chamber was operated at l - 5 x 108 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 litres/sec and ion pumping capacity of 2400 litres/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

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Classified abstracts 811-819 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. C W Cunningham, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 204-208. 21. P U M P S AND P U M P FLUIDS 21 : 16 Impurity effects on heterogeneous nucleation from the vapour I l l mercury on Pyrex glass. See abstract number 783. 21 811. Mulficomponent getter films for getter-ion pumps.* (USA) Since the first commercial application of getter-ion pumping, single metals, such as titanium, have usually been employed for this purpose. However, data obtained several years ago for bulk gettering, ie 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 getter-ion pumps. Results of experiments using the titanium-zirconium system in a sputter-ion pump are presented including residual gas analyses. 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. L D Hall, J Vac Sci Tecbnol, 6 (I), Jan-Feb 1969, 44-45. 21 812. New developments in getter-ion pumps in the USSR.* (USA) 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 litre/sec and find application in thin-film technology, electron tube manufacture, the metallurgy of extra-pure metals, and 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. M V Kuznetsov et al, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 34-39. 21 813. Enhancement of noble gas pumping "for a sputter-ion pump.* (USA) 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 muitiholed tantalum plate combined with conventional flat titanium cathode gives a pumping speed for argon about 40 per cent 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 per cent of that for nitrogen. Both pumps, however, showed some 20 to 25 per cent 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 multi-holed tantalum plates was also tested, which did show an argon pumping speed twice us 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 hr at 2 × 10-s torr with a constant throughput of argon. S Komiya and N Yogi, J Vac Sci Technol, 6 (I), Jan-Feb 1969, 54-57. 21 814. A novel diode sputter-ion pump.* (USA) A new 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 per cent o f t b e 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. L T Lamont, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 47-51.

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21 : 16 815. Influence of the temperature history of condensed argon on its hydrogen adsorpfivity at low temperatures.* (USA) Adsorption of hydrogen on multimolecular layers of condensed argon at 9°K was investigated. Before adsorbing hydrogen the condensed argon had 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 for solid argon condensed at 9°K if tempered at higher temperatures for only a few seconds. This result implies that the structure and density of 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. J Heogevoss, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 58-62. 21 : 31 816. Method for determining getter activity in vacuum devices.* (USA) 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. 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 tubes indicate that decay to an arbitrary level of 80 per cent, induced by slow oxygen-poisoning, occurs rapidly within a narrow pressure range. This implies that determination of oxygen getter capacity based on oxide-cathode emission decay may serve as an alternate method for comparing relative getter film activities. J J Maley and J J Moscony, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 51-54. 21 817. Backstreaming measurements above liquid-nitrogen traps.* (USA) Gravimetric measurements of diffusion-pump backstreaming rates were made above liquid-nitrogen-cooled traps. Experiments were made of over 500-h duration, with 6-inch and 35-inch 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 liquidnitrogen trap, and a special cold cap over the upper nozzle is described, which permits important improvements in system speed without signficant increase in the backstreaming rate. M H Habinnian, J Vac Sci Technol, 6 (l), Jan-Feb 1969, 265-268, 21 818. High vacuum pump for removing water during industrial processes.* (USA) 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 oilsealed pump incorporating special construction details, insulation to prevent undue heat loss, special lubricating and sealing fluid, and a packaged oil-temperature control now provides a unit capable of removing water from a process a.t any pressure level. This pump is capable of reaching final pressures well below 100/~ without the use of auxiliary equipment, and can handle any water load within pump capability at all pressure levels up to 1 atm. R V D Strong and C Francksen, J Vac Sci Technol, 6 (l), Jan-Feb 1969, 263-265. 21 : 34 819. Effect of ultrahigh vacuum on the friction between metals and granular soils.* (LISA) An apparatus has been developed to measure the friction between metals and granular materials in ultrahigh vacuum. Pressures below 10-9 torr have been routinely reached with a vacuum system consisting of a turhomolecular, a getter-ion, and a liquid-N2-cooled titanium sublimation pump. The frictional resistance between steel and ground

Classified abstracts 820-899 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/cm 2 for the various materials and conditions. L L Karafiath and G Molar, J Vac Sci Technol, 6 (I), Jan-Feb 1969, 198-201. 21 : 27 820. Improvement in the sensitivity of helium leak detectors by means of specially designed turbomolecular pump. (Germany) By incorporating a turbomolecular pump into the pumping system of a helium mass spectrometer leak detector unit, the partial pressure of helium in the leak detector tube was increased by a factor of 100 compared to the helium partial pressure in the vacuum chamber. The vanes on the turbomolecular pump are arranged on the rotor axle so that there is a central gap opposite which the pump inlet is situated. Gas flow after entry into the pump is in both axial directions and the flow from both ends of the pump is led off to a common outlet. W Becker, Vakuum-Tecbnik, 17 (8), Oct 1968, 203-205 (in German). 21 : 33 821. Cryopumping for vacuum jackets of liquid nitrogen dewars. (Great Britain) It is common practice to obtain a vacuum in the jackets of glass helium dewars by filling the jackets at room temperature with a few torr of nitrogen or air. This technique was successfully applied to the outer jacket of the nitrogen dewar, by filling it with a few torr of carbon dioxide. (USA) L Finegold, Cryogenics, 9 (2), 1969, 134-135. 21 822. Development and evaluation of a cryodeposit sorption pump capable of pumping helium. (USA) A small cryogenically cooled pump has been developed which is capable of pumping all gases including helium and hydrogen. Its low base pressures makes it suitable for use in ultrahigh vacuum systems, and its high pumping speed for all gases is maintained up to pressures in the range 10 -6 torr. The pump operates by sorbing the normally noncondensable gases in a layer of argon cryofrost which is predeposited on its liquid-helium cooled surface. As with any sorption pump, the sorbent eventually becomes saturated, and the sorbate partial pressure starts to rise. However, unlike most sorbent pumps, this one can be reactivated simply by recoating the surface with a fresh layer of sorbent in situ. Sorption isotherms have been obtained for He on 4.2°K cryodeposits of Ns, A, O2, and COs over a pressure range from 10 -8 to I0 -3 torr. R Dawhara, Rep AD-675207, Sept 1968, 42 pages (Sci Tech Aerospace Reps, 7 (2), 301, N69-12171). 21 : 34 823. Investigation of the effects of fluorine on cryopanel materials for space chamber propulsion tests. (USA) The extent of corrosion by fluorine on several cryopanel materials was evaluated for conditions approximating those which might be expected in a space simulation chamber during rocket engine tests. Four torr of fluorine gas pressure was applied at room temperature and specimens were temperature cycled between 77°K and ambient. The chamber was periodically pumped to high vacuums. Noticeable changes occurred in the surface appearance of the samples. P G Waldrep and D M Trayer, Rep AD-675305, Sept 1968, 44 pages (Sci Tech Aerospace Reps, 7 (2), 313, N69-12572). 21 : 34 824. Nitrogen tetroxide corrosion studies of cryopanel materials for space chamber propulsion testing. (USA) The corrosive action of nitrogen dioxide gas and nitrogen tetroxide cryodeposit on several cryopanei metals was investigated. The specimen temperatures were periodically cycled between 77 and 300°K. The nitrogen dioxide gas pressure at ambient temperature was 4 torr. P G Waldrep and D M Trayer, Rep AD-676031, Oct 1968, 60 pages (Sci Tech Aerospace Reps, 7 (2), 312, N69-12218).

22. GAUGES 22 825. Inverse pressure dependence of the quadrupole ionization gauge.* (USA) A non-magnetic ionization gauge has been developed in which electrons oscillate 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 d c

potential of 27 V towards the other end where there is a disc-shaped electrode at the same potential as the cathode. This causes the electrons to travel back and forth between the ends until they suffer a collision. A quadrupole system serves to keep the electrons from reaching the electrodes and the wall. The system is excited by an 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 centre 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=lO -5 to 10-1° torr the ion current i follows the relationship pi.n=c, n was found to be 1.31 -40.02 for electron emissions of 10, 50, 100, and 500uA. The constant c was 2.88x 10-17 for 10uA, 2.63x 10-ae for 50~A, and in the case of 100~A it was 5.37 x 10-15. H Schwarz an!i H A Tourtellotte, J Vae Sci Technol, 6 (1), Jan-Feb 1969, 260-262. 22 : 27 826. Partial pressure calibration for residual gas analyzers.* (USA) 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 o f a 10x 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 10-6 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 R G A 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. C F Morrison, J Vac Sci Tecbnol, 6 (1), Jan-Feb 1969, 79-82. 22 : 27 827. Residual gas analysis and leak detection by time-of-flight measurements on neutral metastable atoms and molecules.* (USA) The design and construction of a residual gas analyzer which is sensitive to N,, He, A, Ne, and other molecules which have energetic metastable states is described. The presence of these gases is revealed by measuring the time-of-fiight 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-s torr litres/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. D A Crosby and J C Zorn, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 82-84. 22 : 47 828. A magnetron-type ion source for low-pressure residual gas analysis.* (LISA) A conventional electron bombardment ion source operating at 10-100 /+A emission is difficult to outgas sufficiently to allow accurate analysis of the residual gas at pressures below 10-1= 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 x 10-' A/torr is obtained for Ns. The two major peaks at low pressure are H= (1.5 × 10-la torr) and mass 28 (3 x 10-t4 torr). No electronically desorbed ions were observed with background ion currents down to less than 10- ~ torr. W D Davis, J Vac Sci Technal, 6 (1), Jan-Feb 1969, 85-88. 22:16 829. Mass spectrometric investigation of the ion desorption in UHV gauges.* (USA) Electron-induced ion desorption from platinum, platinum-iridium, and molybdenum was 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, H20, CO, and Oa. Ion yields, which were obtained under various

381

Classified abstracts 830-840 conditions, are given. Interaction between coadsorbed species caused changes in the electronic desorption probabilities from the values observed for the separately adsorbed species. Recommendations are made for optimal operation of ionization gauges in order to minimize ion desorption. W K Huber and G Rettinghaus, J Vae Sci Technol, 6 (1), Jan-Feb 1969, 89-92. 22 830. A mass spectrometer without memory effect or gas analysis in ultrahigh vacuum.* (USA) The described Omegatron mass-spectrometer is equipped with an internal heating device. All inner metal parts of the Omegatron gauge are made of noble metal and can be maintained, during the measurements, at a maximum temperature of 500°C. For cleaning and degassing the gauge the temperature of the metal parts may 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 electrodepotentials even after many heating-cycles. H Gentsch, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 93-96. 22:47 831. Some properties of the Monopole mass spectrometer.* (USA) 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, and for various extrance/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) s, 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. P H Dawson and N R Whetten, J Vac Sci Technol, 6 (I), Jan-Feb 1969, 97-99. 22 : 47 832. Some causes of poor peak shapes in quadrupole field mass analyzers.* (USA) 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. The analytical method of yon Busch and Paul was extended to the three-dimensional quadrupole mass spectrometer, and, using numerical computation of ion trajectories, the extent as well as the position of the resonances were calculated. New experimental data are presented showing the occurrence of nonlinear resonances and the agreement between theory and experiment. The effect of adjustments in electrode spacing on peak shapes was investigated. The results demonstrate that an analysis of the non-linear 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. N R Whetten and P H Dawson, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 100--103. 22 833. An orbitron-type ionization gauge with an external electron source. (Great Britain) An orbitron-type ionization gauge, in which electrons are injected into the radial electrostatic field from an external electron gun, is described. The gauge has a sensitivity of up to 20,000 torr -1 and does not exhibit the troublesome ion current instabilities frequently observed with the orbitron. R K Fitch et al, Vacuum, 19 (5), May 1969, 227-229. 22 : 18 834. X-ray emission in the energy range 100 eV- 1000 eV. (Germany) The x-ray emission from a target bombarded by electrons of energy between 100 and 1000 eV, was measured for various elements as target materials. The x-ray detector was a molybdenum ring-shaped collector and measurements were carried out at 10-8 torr. The variation in x-ray yield from element to element was found to be a periodic function of the atomic number, Z. The relationship between the 382

x-ray yield and the quantum energy levels associated with the target material is discussed. H J Van Ark and J van de Rotte, Vakuum-Technik, 17 (7), Sept 1968, 173-177 (in German). 22 835. A new method of operating an omegntron to improve performance: the time separation of processes. (Great Britain) The sensitivity of an omegatron mass spectrometer is limited by the space-charge effect due to the electronic and ionic charges, although under normal conditions a partial compensation of these charges occurs. A new operation mode of the omegatron, characterized by the time separation of the ionization and ion collection processes, is proposed. Experimental data are reported and discussed. (Romania) G Comsa and A lVlireea, J Sci Instrum, Ser 2, 2 (4), 1969, 336-338. 22 836. The output and sensitivity of vacuum ganges using a heated element in a Wheatstone bridge. (Great Britain) An analytical approach to design methods for Pirani and related gauges is presented, with particular reference to bridge classification and gauge sensitivity. It is shown that, using this approach, a useful insight may be gained into me interclepen0ence of the element and its associated bridge. The technique may be used over the whole range for which the output is pressure dependent, with equal facility for both metallic and thermistor elements. E M McKay, J Sci Instrum, Ser 2, 2 (4), 1969, 305-310. 23. P L U M B I N G 23 837. Dynamic high vacuum seal. (USA) A rotary test chamber is described with special emphasis on the large diameter seals used. The seals used Teflon O-rings, consisting of a Teflon sleeve and a Viton insert. Two such O-rings were used, one as a face seal and the other as a radial seal, the space between them being differentially pumped. P C MeLeod, Res Develop, 19 (12), 1968, 45-47. 23 • 34 838. Development of bearings for nuclear reactors, in space. (USA) Bearings were developed to operate in reactor control components in a space environment at pressures from as low as 10 -x2 tort to as high as 10 -a torr in the temperature range from 950 to 1500°F, with a life requirement of 1 to 5 years. W J Knrzeka, JPL Proc of the 3rd Aerospace Mech Syrup, Rep NASA-CR-97758, Oct 1968, p 85-91 (Sci Tech Aerospace Reps, 7 (2), 333, N69-11811). 24. VALVES 24 839. Bellows-sealed valve for reactive gases at moderately high temperatures. (USA) An all metal valve is described, which was constructed for use with reactive gases such as fluorine. The construction of the valve includes brazed parts, but the brazing was performed without the use of any

flux. G C Straty, Rev Sci lnstrum, 40 (2), 1969, 238-239. 27. LEAK DETECTORS AND LEAK DETECTION

27:21 Improvement in the sensitivity of helium leak detectors by means of specially designed turbomolecular pump. See abstract number 820. 27 : 22 Partial pressure calibration for residual gas analyzers. See abstract number 826. 27 : 22 Residual gas analysis and leak detection by time-of-flight measurements on neutral metastable atoms and molecules. See abstract number 827. 27 840. Measuring small gas flows into vacuum systems.* (USA) A new mass flowmeter is described, the operation of which is based on the thermal capacity principle. Temperature differences originating from the gas flow are sensed thermoelectrically and the output displayed on a millivolt meter, recorder or other read-out device. Multiple-element transducers have permitted a maximum sensitivity

Classified abstracts 841-848 of 1 mV/0.5 std cm3/min to be achieved. Use impedance potentiometer gives a device suitable low as 0.005 std cmS/min, which is 4-1 per cent stability and accuracy. C E Hawk and W C Baker, J Vac Sci Technol, 255-257.

of a 0-1 mV, highfor measurements as in terms of linearity, 6 (1), Jan-Feb 1969,

27 841. Fine and gross leak testing of hermetically sealed components. (USA) Improved methods of fine and gross leak testing of electronic components are described, which show that refinement can be achieved by better control of the test parameters involved. Optimum techniques for fine leak detection employing a mass spectrometer helium leak detector and back-pressurization of components have been developed. In order to pinpoint gross leaks a positive and efficient back-pressurization bubble test, employing an inert fluid, has also been developed and evaluated. The criteria and standards used during visual inspec tion for the acceptance or rejection of components were investigated and correlations of visual defects with leakage behaviour established. The concept of "relative hermeticity" of a component is defined in relation to the critical partial pressures of both the filler gas in the component and external gases which have entered the component. P A Panza, Rep FSR-AD9-OI-68-2, Nov 1968, 142 pages (Sci Tech Aerospace Reps, 7 (2), 302, N69-12512).

28. HEATING E Q U I P M E N T AND T H E R M O M E T E R S 28 : 33 842. Pyroelectric thermometer for use at low temperatures. (USA) The pyroelectric coefficients, dc dielectric constants and volume resistivities of three ferroelectric ceramic materials were measured over the temperature range 4.2 to 300°K. Expressions are derived for the temperature responsivity and figure of merit. S B Lang et al, Rev Sci lnstrum, 40 (2), 1969, 374-384.

III. Vacuum applications 30. EVAPORATION AND SPUTTERING 30 : 37 Pressure effects on the friction coefficient of thin-film solid lubricants. See abstract number 912. 3O 843. Magnetic "Ternary Permalloy" memory films.* (USA) Ternary paramagnetic additions to Permalloy have been used to produce magnetic films with salient modifications of the coercive and anisotropy properties. Films from 4000 A to 12,000 A 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 N D R O memory employs an ultralow dispersive read film which utilizes vanadium, and a storage film with high coercivity containing cobalt. The D R O memory eliminates the storage film and operates with a modified read film. F M UnoandRFVieth, J VacSciTechnol, 6 (l),Jan-Feb 1969,180-183 3O 844. Alternating current electrical properties of evaporated molybdeaum oxide films.* (USA) The limitations of dc measurements on doped thin film metalinsulator-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 much wider scope in the range of measurements which may 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 of the MoO~ is estimated to be about 10zs cm -3. J G Simmons and G S Nadkarni, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 12-17. 30 845. Electrical properties of titanium, zirconium, and hafnium films from 300°K to 1.3°K. * (USA) 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 A to 12,000 A have superconductive transition temperatures near 1.3°K for films deposited at substrate temperatures of 100°C and below. Epitaxial growih 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 A and of 8 at 400 A. This is nearly twice those of the corresponding polycrystalline films on Coming 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 A thick or greater. Superconductivity was not observed for either titanium or hafnium films down to 1.3°K. Only the hexagonal closepacked crystal structure was found for all three film materials. J W McCamont and P E Friebertshauser, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 184-187. 30 846. Complex impedance characteristics of low-resistance bismuth films.* (USA) A structure-determined electrical impedance in the infrared region between 2 and 15 # was postulated for thin bismuth films a few years ago and an equivalent circuit was determined for films having initial resistances of 90 ohms/square. The circuit was derived from resistance and infrared transmission measurement. 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 ohms/square. L L Howard, J Vac Sci Tecbnol, 6 (l), Jan-Feb 1969, 188-193. 30 847. Epitaxial thin films of ZnO on CdS and sapphire.* (USA) The technique for obtaining polycrystalline thin films of ZnO by sputtering of the compound has been perfected so that cpitaxial films can be obtained on sapphire and CdS. Dependence of the crys talline perfection of the films on substrate temperature, deposition rate, and substrate polish has been studied in detail. Substrate temperatures from I00 ° to 500°C and deposition rates from I to I00 A/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. G A Rozgonyi and W J Polito, J Vac Sci Technol, 6 (I), Jan-Feb 1969, 115-119. 30 848. Problems encountered during deposition of optical thin films with reproducible characteristics in an automatic coater.* (USA) 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. H K Pulker and E Girardet, J Vae Sci Technol, 6 (I), Jan-Feb 1969,131134.

383

Classified abstracts 849-858 30

849. High current vacuum system for muitilayer filter deposition.* (USA) 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 trap is situated on top of the evaporating source and it serves to funnel the vapour stream toward the target. This arrangement saves time and unrecoverable material since it considerably reduces spillage or vapour on the interior. W L Cornelius and J G Martner, J Vac Sci Technol, 6 (l), Jan-Feb 1969, 140-144. 3O 850. Deformation of optical surfaces by film stress.* (USA) 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 behaviour 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 profile of optical surfaces is given, and examples are presented illustrating how this effect may be minimized. R J Scheuerman, J Vac Sci Technol, 6 (I), Jan-Feb 1969, 145-147. 30 851. Adhesion mechanism of gold-underlayer film combinations to oxide substrates.* (USA) 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 l0 A. K E Haq et al, J Vac Sci Technol, 6 (I), Jan-Feb 1969, 148-152. 3O 852. Intrinsic stress in evaporated metal films.* (USA) Using a model, recently proposed by the author, for the origin of the observed intrinsic tensile stresses in thin metal films, a large stress S is predicted which is 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 AI, Cu, and Ni films as a function of Tm/Ts and the data obtained verifies the above predictions. For Tm/Ts much larger than 4, S in Al films is 2× 10' dyn/cm=; in Cu, 7× l0 g dyn/ cm 2, and in Ni, 9 × l0 g dyn/cm g. As Tm/Ts becomes less than 4 the stress in each case is small, and decreases with increasing film thickness. E KIokholm, J Vac Sci Technol, 6 (I), Jan-Feb 1969, 138-140. 3O 853. Dielectric properties of reactively sputtered films of aluminium nitride.* (USA) Films of AIN, up to 5/, thickness, have been grown by diode reactive sputtering under conditions in which the initial residual gas pressure was less than 10-g 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 aluminium. In general, the dielectric properties were superior to those reported for ceramic aluminium nitride, with film resistivities in the range 10-xg ohm-era and dissipation factors lower than 0.004. 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. A J Noreika et al, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 194-197.

384

30 854. RF sputtering of multilayer thin films.* (USA) Thin-film deposition rates and uniformity are presented for a large area rf diode of conventional style, with optimized parameters producing 1500 A/min copper and 500 A/min SiO= without external magnetic field. Measurements of rate and corresponding uniformity were also made for Si3N~, Al=Oa, nickel, molybdenum and gold, where the thickness uniformity inside a 5-inch-diameter circle was =1=2.5% for nickel and d=2% for SiO2. The sputtering apparatus consists of two 8-inch diameter water-cooled targets fed with 2.5 kW rf power, spaced 1-inch away from the substrate table. Influence of forward-coupled rf power on rate is also discussed. L Herte et al, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 109-114. 3O 855. Electrical characterization of radio-frequency spattering gas discharge.* (USA) 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) o f a n rfsputtering gas discharge was determined asa 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/cm ~ to 2.5 × I0 -t3 F/cm 2 between zero and 156 G. Conductance changed from 1.6 x 10-6 mho/cm 2 to 3.9× 10 6 mho/cm = in the same interval. Pressure dependence was strongest at zero magnetic field, changing both capacitance and conductance approximately 30 per cent between 7.5 and 30 retort (argon). At high magnetic field, there was very little effect. No appreciable change was observed between I.l and 6.5 W/cm 2 power application. Design equations are given for a simple matching network, and a design example is presented to demonstrate application. J S Logan et al, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 120-123. 3O 856. Substrate bombardment during RF sputtering.* (USA) For the conditions relevant to the "peak" type of rf sputtering arrangement and most rf sputtering devices, it is shown 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. 1 Brodie et al, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 124-127. 3O 857. High capacity sputtering apparatus.* (USA) 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. E C Muly and A J Aronson, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 128-130. 3O 858. Preparation and superconducting properties of thin films of transition metal interstitial compounds.* (USA) Some recent studies on thin-film structures of transition metal compounds having both high critical temperatures (To> 14°K) and large upper critical fields (H 2~ 100 kOe), are discussed. The materials in all have the rocksalt structure 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 x 10 -1° torr. Variation of the nitrogen partial

Classified abstracts 859-870 pressure over the range 10-a to 10 -6 torr was used to obtain different film compositions. J R Gavaler et al, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 177-180. 30 : 33 859. Nucleation studies using electron transparent NaCI substrates.*

(USA) A technique was developed for fabricating NaCI 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 carboncoated 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. R F Miller and R W Hoffman, J Vac Sci Teclmol, 6 (1), Jan-Feb 1969, 65-68. 30 860. Characterization, control, and use of dielectric charge effects in silicon technology.* (USA) The charge behaviour of dielectric films on silicon is particularly important in device and integrated circuit technology because of surface defects. Models for ionic migration, fixed-interface charge, and injection trapping are reviewed for insulators used in silicon technology: thermally-grown silicon dioxide and chemical vapourdeposited silicon dioxide and silicon nitride. The distinctive characteristics of insulator charge related to these mechanisms are applied in the case of reactively sputtered SiP2 and Ta2Os. Ion migration and injection-trapping behaviour 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. J R Szedon and R M Handy, J Vac Sci Technol, 6 (I), Jan-Feb 1969, 1-12. 30 861. Fabrication of evaporated foil capacitors. (Germany) The increasing demand for low-voltage capacitors has led to a greater interest in thin film techniques as a means of manufacture for capacitors. The difficulties of high vacuum, vapour deposition increase with decreasing film thickness. Some problems associated with production scale operations for vacuum deposited foil capacitors are discussed with particular reference to process equipment and control. (Finland). A Tiilikka, Vakuum-Technik, 17 (8), Oct 1968, 206-208 (in German). 3O 862. Dielectric materials in semiconductor devices.* (USA) 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 aluminium 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. T L Chu, J Vac Sci Technol, 6 (I), Jan-Feb 1969, 25-33. 30 863. The Photometallic process.* (USA) 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. The thin film is coated with a polymer layer containing a photodecomposable material so that a pattern of light on the surface causes preferential photodecomposition and the products react with the thin film, removing it in the exposed areas. The coating and reaction products are removed by a solvent rinse, giving a positive copy of the light image 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. The thin-film parameters, coating parameters, and proposed reaction mechanisms are

discussed. Among other applications, the process has potential use in microelectronic circuit fabrication. d F Burgess and D L Schaefer, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 134-137. 30 864. Photoresist materials and applications.* (USA) Photoresists can be classifed as either positive resists or negative resists depending on their mode of interaction with light. With the exception of photo masking, 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. R O Lussow, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 18-24. 30 : 33 865. Superconductivity of/~-tungstea films. (USA) Evaporated tungsten films were found to have a superconducting transition temperature of 3.2°K as compared to. the bulk value of 0.01°K. Structural study of the electron-beam-evaporated W films was carried out by both x-ray and electron diffraction techniques. Some relationship between the structure of the film and the evaporation conditions (pressure, evaporation rate) is determined. S Basavaiah and S R Pollack, J Appl Phys, 39 (12), 1968, 5548-5556. 30 866. Controlled electron beam evaporation of beryllium. (Great Britain) A new method of controlling electron beam evaporation of beryllium utilizing the light emitted by the vapour as a measure of evaporation rate is described. This method has been used to give films with thickness accuracies to three per cent. (USA) P S McLeod and C W Nordin, J Sci Instrum, Set 2, 2 (4), 1969, 381. 30 867. Silicone carbide films, evaporated in vacuum on synthetic micas. (Japan) The SiC was evaporated by electron beam gun. The pressure in the system was less than 5 < 10 s tort, and the evaporation rate was 5.5 A/see. The substrate temperature varied from room temperature up to 1000~C. Y Onuma, Japan J Appl Phys, 8 (3), 1969, 401. 30 868. Thickness measurements of silicon dioxide films over small geometries. (USA) A simple nondestructive interferometric technique to measure the thickness of transparent films on reflecting substrates in the range of 100 to 20,000 A is described. Measurements can be made over areas as small as 0.1 mil in diameter. L J Fried and H A Froot, J ApplPhys, 39 (12), 1968, 5732-5735. 30 869. Optical properties of vacuum-evaporated selenium and tellurium. (USA) The optical properties of evaporated films of Se and Te at room temperature have been determined in the energy range from 5-25 eV. Films for reflectance measurements were prepared by vacuum evaporation in situ, from stainless steel boats. During evaporation the pressure was in the range of 10 e tort. J D Hayes et al, J ApplPhys, 39 (12), 1968, 5527-5532. 30 : 33 870. Some observations on the appearance and properties of the photovoltaic effect in thin layers of tellurium deposited obliquely in a vacuum. (Great Britain) The studies, made during the formation of the tellurium on two similar specimens simultaneously deposited in vacuum (10 -s torr) on a glass substrate at room temperature under different deposition rates (10-500 A s -1) have shown that in general both the photovoltaic effect and the electrical conductivity increase with increase of the layer thickness. A model is proposed to explain the phenomena. (Romania) C Gheorghita-Oancea et al, Brit J Appl Phys, Ser 2, 2 (4), 1969, 617620.

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Classified abstracts 871-884 30 871. Epitaxinl silicon and gallium ursenide thin films on insulating ceramic substrates. (USA) A state-of-art literature survey is presented on the epitaxial deposition of silicon and gallium arsenide thin films on ceramic substrates. A series of charts identifying the various variables as reported in the literature is presented. J T Milek, Rep AD-675578, Aug 1968, 156 pages (Sci Tech Aerospace Reps, 7 (2), 266, N69-11873). 30 872. Vacuum deposition of thin films by means of a COg laser. (USA) The use of a high power CO= laser is proposed for the vacuum deposition of thin films, and results of experiments with such a method are related. The best results were obtained with pressed tablets of sintered material. (W Germany) G Groh, J Appl Phys, 39 (12), 1968, 5804-5805. 3O 873. The temperature of substrates used in the preparation of thin films by vapour deposition. (Australia) A considerable discrepancy has been observed between the substrate temperature and the hearth temperature in an evaporation assembly, when the substrate is maintained at elevated temperatures. Calibration curves for the substrate temperature in terms of the hearth temperature have been determined for the system with substrates of single crystal rocksalt and mica. J N King, Rep ARL/ME-55, (Aeronautical Research Labs, Melbourne), June 1968, 13 pages (Sci Tech Aerospace Reps, 7 (2), 311, N69-12145). 30:41 874. Optical properties of dilute silver-indium alloys in the ultraviolet. (USA) The optical constants of silver and five dilute silver-indium alloys were determined from reflectance and transmittance measurements in the spectral region between 3.35 and 4.28 eV on vacuum evaporated films. The concentrations ranged from 0.5 to 4.1 per cent In, and the film thicknesses between 1000 and 1600 A. R M Morgan, Rep State Univ of Iowa, Univ Microfilms, No 68-5967, 108 pages (Sci Tech Aerospace Reps, 7 (2), 306, N69-11348). 30 875. Metal films sputtered at low voltages. (USA) Metal films sputtered at low voltages possess abnormally high resistivities. It was found that this is caused by the microcrystalline structure of the film rather than by residual oxygen or water vapour in the system. An explanation is proposed. W W Lee, J Appl Phys, 39 (12), 1968, 5366-5368. 30 876. Charge phenomena in dc reactively sputtered SiO= films. (USA) The SiO= films were deposited in a d c reactive sputtering apparatus using a polycrystalline silicon disc target of 4.5 inch diameter. A permanent magnet, located immediately beneath the substrate holder generated a magnetic induction field of a few hundred gauss in the glow discharge region. The system was evacuated by an oil diffusion pump with a liquid-nitrogen trap. The charge behaviour of the SiO= films has been studied, and the results are discussed. S Y Wu and N P Formigoni, J Appl Phys, 39 (12), 1968, 5613-5618. 30 877. Preparation, structure, and properties of sputtered, highly nitrided tantalum films. (USA) Highly nitrided films of tantalum have been prepared by cathodic sputtering of high-purity tantalum in a pure nitrogen atmosphere. The effect of cathode current density and film thickness on the film structure, crystal structure, composition, resistivity, current-voltage characteristics, and optical energy gap were investigated. H J Coyne and R N Tauber, J Appl Phys, 39 (12), 1968, 5585-5593. 30 : 37 878. Changes in properties of thin metallic film coatings by mechanical and thermal treatment. (USA) The possibility of raising the density of films of zinc, cadmium and copper to that of the bulk material is demonstrated. The experiments were carried out on zinc and cadmium films sputtered on quartz substrates at reduced pressures. It was found that the increase in density of the films follows the same pattern as in the case of powders. I K Sinishchuk, Rep AD-677353, Nov 1967, 10 pages (Sci Tech Aerospace Reps, 7 (4), 676, N69-14497).

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31. EVACUATION AND SEALING 31 : 21 Method for determining getter activity in vacuum devices. See abstract number 816. 31 879. A vacuum hot-press for toxic materials. (Great Britain) A small vacuum hot-press is described which is easily operated and maintained with a Harwell M k II glove box. The vacuum envelope is an 11.5 in. long 1.75 in. diameter silica tube. A sliding vacuum seal is incorporated at one end of the envelope. (Australia) J W Kelly, J Sci Instrum, Ser 2, 2 (4), 1969, 369. 32. NUCLEONICS 32 880. A sectored isochronous ring for accelerating heavy ions. (Holland) An accelerator capable of accelerating heavy ions to energies around 7 MeV/nucleon is proposed. It consists of a pre-stripper (an electrostatic accelerator, a cyclotron or a linac) and an isochronous cyclotron with separated magnets. Various factors relevant to the design are discussed. (W Germany) G Schatz, Nuclear lnstrum Methods, 67 (1), 1969, 103-108. 32 881. Soviet Particle Accelerators. Analytical review. (USA) The report reviews Soviet work on particle accelerators, including research, development, construction and operation of the devices and associated equipment. The material is based on Soviet publications from 1962-1967. A Polashkin, Rep AD-675120, Oct 1968, 298 pages (Sci Tech Aerospace Reps, 7 (2), 274, N69-12433). 32 882. Properties of the ARL magneto-plasma device. Part 1: System operation and plasma generation. (USA) The vacuum system and the magnetic field generating system of the magneto-plasma device are described. The end plate heating sytems (ionizer), the Cs-injection system and the semi-automatic interlock are also discussed. H S Anton and W Fritz, Rep AD-675993, May 1968, 28 pages (Scl Tech Aerospace Reps, 7 (2), 355, N69-12226). 32 883. A Geiger-Muller counter for ultrahigh vacuum systems. (USA) A counter is described which has a 25 per cent efficiency for t4C beta radiation, is bakeable, and has been used in ultrahigh vacuum systems with ultimate pressures below l × l0 -I° tort. K Klier, Rev Sci lnstrum, 40 (2), 1969, 372-374. 33. GENERAL PHYSICS AND ELECTRONICS 33 : 16 Experimental investigation of gas-surface re-emission distribution using continuum source molecular beam techniques. See abstract number 797. 33 : 18 A new technique for measurements of radial distribution of excited species in plasmas and its application to capillary discharges in argon. See abstract number 806. 33:21 Cryopumping for vacuum jackets of liquid nitrogen dewars. See abstract number 821. 33 : 28 Pyroelectric thermometer for use at low temperatures. See abstract number 842. 33 : 30 Nucleation studies using electron transparent NaCI substrates. See abstract number 859. 33 : 30 Superconductivity of fl-tungsten films. See abstract number 865. 33 : 30 Some observations on the appearance and properties of the photovoltaic effect in thin layers of tellurium deposited obliquely in a vacuum. See abstract number 870. 33 884. Auger electron spectrometer as a tool for surface analysis (contamination monitor).* (USA) By means of Auger electron analysis it is becoming increasingly possible to determine the composition of surface contaminants. With

Classified abstracts 885-898 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. N J Taylor, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 241-245. 33 885. Electrostatic charge distribution on ultrahigh vacuum cleaved silicates.* (USA) 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 U H V 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 octupolar shapes on the face of cylindrical samples in excess of 1 esu/cm*. A relationship appears to exist between the orientation of the multipolar distributions and the crystallographic axes. Results from the first cleavages of orthoclase (nominally, KAISi3Os) at 10-1° 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. On raising the pressure with dry nitrogen, the charge is stable (to a first order of approximation) up to pressures in the 10 micron range. Discharge in bursts, as the pressure is raised, is readily explained by the Paschen sparking potential relation for gaseous discharges. J J Grossman, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 233-236. 33 886. Comparison of measurements of rubidium atomic beam intensity by U H V microbalance, quartz oscillator and platinum foil gauge at low temperature. (Germany) Two series of experiments were carried out, each of which involved simultaneous intensity measurements by two independent methods. In the first, a magnetically compensated microbalance and quartz oscillator were combined, the resonating quartz oscillator serving as the pan of the microbalance at temperatures of about 180°K. The second arrangement involved a measuring cell containing the quartz oscillator and a platinum foil device calibrated for surface ionization, both operating at 80°K. Taking account of the temperature changes occurring in the quartz oscillator during deposition, the atomic beam intensities measured by these methods agreed to within 4-2 per cent. Changes in the weighing sensitivity of the quartz crystal oscillator with decreasing temperature, indicated by theory, could not be detected experimentally. D Hillecke, Vakuum-Technik, 17 (7), Sept 1968, 167-172 (in German). 33 887. Metastuble species produced by electron excitation of Nz, H2, N20 and CO2. (USA) A molecular beam is crossed by an electron beam to produce rectastable molecules and fragments which are detected by electron ejection from a CsaSb cathode in a chamber operating at ultrahigh vacuum. Excitation functions for the production of H2 (C 8s IIu) molecules and of photons from H~ are reported. The time-of-flight distribution of the slow group of H (2S) atoms from Hs has been measured and this differs from a previously reported distribution. Threshold-energy and kinetic-energy measurements were made on the electronically excited fragments produced in the dissociative excitation of COs and N20. R Clampitt and A S Newton, J Chem Phys, 50 (5), I March 1969, 19972001. 33 888. Exposure-dependent surface recombination efliciencies of atomic oxygen. (USA) Surface recombination efficiencies (7') on metals were measured as a function of exposure time in steady Oseen flows which provide a stepfunction increase, or pulse, in oxygen-atom concentration. The relationship between the surface and free stream concentration of oxygen atoms was obtained by means of the mathematical analogy between heat and mass transfer. It was possible to use relatively high partial pressures of atomic oxygen and carrier gas (1 per cent atomic oxygen in a flow pressure of 4--6 mm Hg of an Ar-Ot mixture), which are important to the accuracy of the measurements of many of the parameters involved. The final values of 7' found were: 0.12, 0.03, 0.017, 0.0085, 0.007 and 0.005 for Ag, Cu, Fe, Ni, AI and Au, respectively. A L Myerson, J Chem Phys, 50 (3), 1 Feb 1969, 1228-1234.

33 889. Ultrahigh vacuum reflectometer for use with extreme ultraviolet synchrotron radiation. (USA) An ultrahigh vacuum reflectometer is described which may be used to study reflectance, transmittance and photoemission on samples evaporated in situ. The system operates down to 5× 10-1° torr. (Germany) B Feaerbacher et al, Rev Sci Instrum, 40 (2), 1969, 305-306. 33 890. Mass spectrometric studies of the vaporization of refractory metals in oxygen at low pressures. (USA) The kinetics of formation of the various gaseous species resulting from the interaction at high temperatures (1600-3000°K) of refractory metals with oxygen at low pressures (7 × 10-s-I × 10-a torr) was studied by mass spectometry. Re, Ta, Nb, V and Zr were investigated. L H Rovner et al, Rep AD-675319, July 1968, 62 pages (Sci Tech Aerospace Reps, 7 (2), 254, N69-12461). 33 891. A simple quadrupole mass spectrometer. (USA) A very simple design of quadrupole mass spectrometer is one in which the rods are fed directly into holes in the supporting end plates. In the version described, the rods are of quartz and the end plates of stainless steel. A R Fairbairn, Rev Sci lnstrum, 40 (2), 1969, 380-381. 33 892. Some logarithmic properties of photomultipliers. (USA) The logarithmic properties of a photomultiplier are investigated. An exponential current generator for the calibration of logarithmic amplifiers is described. The dynamic range of the generator is about 4 decades with an output current of 250 mA. (Israel) D Maydan and M Shaanan, Rev Sci Instrum, 40 (2), 1969, 218-223. 33 893. Waveguide window and nonmetallic vacuum can for low temperature EPR. (USA) A low temperature microwave window and an electrically nonconductive vacuum can is described. The window is made of brass and Mylar sheet sealed with Stycast, and the vacuum can is of Stycast. B C Thompson and A W Nolle, Rev Sci lnstrum, 40 (2), 1969, 374. 33 894. A digital vacuum torque magnetometer for the temperature range 300-1000°K. (Great Britain) An automatic torque magnetometer is described in which a modified ballistic galvanometer is used as a torque head. A compact vacuum furnace enables measurements to be made in the temperature range 300-1000°K and in fields up to 12 kOe using a 7-inch electromagnet. E J Fletcher et al, J Sci lnstrum, Ser 2, 2 (4), 1969, 311-3 i 4. 33 895. A simple scanning electron microscope. (USA) A simple scanning microscope has been built which uses a field emission electron gun, without the aid of auxiliary lenses. The design and operation of the microscope are described. A V Crewe et al, Rev Sci lnstrum, 40 (2), 1969, 241-246. 33 896. The interaction of low energy atmospheric ions with controlled surfaces. (USA) The ejection of electrons associated with the Auger neutralization of N ( + ) 2 , H ( + ) 2 and N ( + ) ions at the (100) face of a tungsten crystal and a polycrystalline molybdenum surface has been studied. A detailed description is given of the ion beam used in these studies. R H Price, Rep AD-675206, Sept 1968, 120 pages (Sci Tech Aerospace Reps, 7 (2), 279, N69-12053). 33 897. The scattering of high energy argon atoms from a well characterized (100) tungsten surface. (USA) A scattered number flux distribution for nearly monoenergetic high energy (0.25 to 2.0 eV) argon beams impinging on the (100) face of a single crystal of tungsten were obtained as part of a basic study of direct comparison with existing and forthcoming theoretical analyses. The scattering studies were performed in an ultrahigh vacuum environment. D R O'Keefe, Rep NASA-CR-98691, July 1968, 86 pages (Sci Tech Aerospace Reps, 7 (4), 650, N69-14599). 33 898. Estimate of the temperature rise of micron-sized silver particles in the electron microscope due to electron-beam heating. (USA) 387

Classified abstracts 899-907 It is shown that the heat loss by radiation does not significantly contribute to the temperature rise of micron-sized silver particles on a carbon film, if the temperature is below the melting point of the particle. The temperature is strongly influenced by the distance of the particle from the heat sink, eg other metallic particles. G H Gessinger et al, J Appl Phys, 39 (12), 1968, 5593-5587. 34. HIGH ALTITUDE AND SPACE TECHNOLOGY 34:21 Effect of ultrahigh vacuum on the friction between metals and granular soils. See abstract number 819. 34:21 Investigation of the effects of fluorine on cryopanel materials for space chamber propulsion tests. See abstract number 823. 34 : 21 Nitrogen tetroxide corrosion studies of cryopanel materials for space chamber propulsion testing. See abstract number 824. 34 : 23 Development of bearings for nuclear reactors in space. See abstract number 838. 34 : 37 Ultrahigh vacuum adhesion of comminuted basalt rock to metals. See abstract number 907. 34 : 47 899. Optical surface degradation from combined ultraviolet radiation and outgassed materials.* (USA) 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 MgF2overcoated aluminium mirrors while the mirrors were irradiated with ultraviolet light in vacuum. Mirror temperatures as low as - 6 0 ° C were used to determine the point at which condensation was incipient. The measurements performed on these mirrors included Lyman reflectance and infrared analysis of the deposit. The initial results obtained with this system demonstrate {hat Lyman reflectance is essentially unaffected by heavy condensates of some materials but almost completely destroyed by very thin deposits of other materials. J F Scannapieco and R N Griffin, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 209-214. 34 900. Space environment operation of experimental hydrazine reactors. (USA) Experimental investigations relating the low temperature, high vacuum hydrazine ignition properties of Shell 405 catalyst with the concentration of adsorbed gas species (02, N2, H2 and NHs) present on the catalyst surface are reported. The laboratory investigations revealed that: (1) Shell 405 catalyst retains strongly chemisorbed oxygen which will not desorb significantly in high vacuum, even at elevated temperatures. (2) Adsorbed hydrogen does not readily desorb in vacuum at temperatures below 600°C. (3) Nitrogen adsorption is extremely low, and adsorbed ammonia tends to decompose above 300°C. Three catalyst surface conditions were investigated in high vacuum ignition tests: a surface containing chemisorbed oxygen, a clean surface, and a surface containing chemisorbed hydrogen. R A Carlson et al, Rep NASA-CR-97838, 1968, 74 pages (Sci Tech Aerospace Reps, 7 (2), 363, N69-12432). 34 901. Rapid (explosive) decompression emergencies in pressme-suited subjects. (USA) A review is presented of the biochemical factors determining lung damage following explosive decompression of space suits in vacuum test chambers. Critical variables, such as ratio of free volume of suit to area of orifice, pressure ratio and pressure differential are outlined. Calculations were made of orifices caused by catastrophic disruption of typical soft and hard space suits at seal sites, and predictions were made as to the likelihood of lung damage, based on the location of the seal disruption and open]closed glottis conditions. It was concluded that all seal areas should be designed for slow propagation of disruptive processes, and that preparation of therapeutic

388

devices and facilities for handling explosive decompression emergencies would be advisable. It was found that the use of gases other than 3.7 psia O.~ in the suits alters the hazard, the higher the percentage of helium in the mixture the less is the hazard. E M Roth, Rep NASA-CR-1223, Nov 1968, 129 pages (Sci Tech Aerospace Reps, 7 (4), 609, N69-13969). 34 902. Controlled-leakage sealing of bearings for fluid lubrication in a space vacuum environment. (USA) An example of sealing hydrodynamic bearings to the extreme requirements of space vehicles for extended periods of time is analyzed. H I Silversher, Rep NASA-CR-97798, Oct 1968, 93-99 (Sci Tech Aerospace Reps, 7 (2), 300, N69-11812). 34 903. Vibration/vacuum screening of space lubricants. (USA) Selected solid-film lubricants and self lubricating retainer materials were evaluated for use on small ball bearings operating in a simulated space environment. Test conditions include a combination of vacuum (10 -7 torr), low and moderately elevated temperatures and severe vibration (28 g rms, 85 g rms peak). F J Clauss and S P Drake, Rep NASA-CR-92435, Dec 1967, 96pages (Sci Tech Aerospace Reps, 7 (4), 669, N69-14737). 34 : 16 904. Adsorption, and the loss of Moon's atmosphere. (USA) The various theories pertaining to the total absence of atmosphere on the moon are surveyed. To explain this phenomenon, it is proposed that consideration be given to the process of gas adsorption by the lunar surface. A M Gutrin et al, Rep NASA-CR-97793, Nov 1968, 4pages (Sci Tech Aerospace Reps, 7 (2), 372, N69-11957). 34 905. Application of a low density plasma-jet wind tunnel to aerodynamics in the ionosphere. (Japan) In order to simulate flight conditions in the ionosphere and to investigate a low density, high enthalpy, high speed flow with chemical reaction, a low density plasma-jet wind tunnel was constructed at the Department of Aeronautical Engineering of Kyoto University. Performance tests were carried out in nitrogen and argon plasma jets. The results indicate that the over-all Mach number and Reynolds number performance of this wind tunnel lies in the transition region. It is also shown that the plasma-jet wind tunnel satisfied the conditions of a neutral dominated continuum flow in the required aerodynamic flow regimes in the ionosphere. G Kamimoto and M Nishida, J Vac SocJapan, 12 (2), 1969, 50-57 (in

Japanese). 37. METALLURGY, INORGANIC CHEMISTRY, ANALYTICAL CHEMISTRY 37 : 16 Nonequilibrium chemical reactivity of polycrystalline iron foils. See abstract number 785. 37 : 30 Changes in properties of thin metallic film coatings by mechanical and thermal treatment. See abstract number 878. 37 906. Electronic structure of clean metallic interfaces.* (USA) The theory of clean metallic interfaces is reviewed firstly with regard to the interface potential for a metal-vacuum interface. The various models applied to this potential are surveyed and a dynamic model i~ developed involving the local density approximation for an electron fluid in an average positive background. This model is extended to describe bimetallic interface. The major prediction obtained 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 for a systematic description of metal-semiconductor contacts without introducing surface states. C B Duke, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 152-166. 37 : 34 907. Ultrahigh vacuum adhesion of comminuted basalt rock to metals. (USA) The strength and nature of the forces of adhesion between soils of basaltic composition and 304 stainless steel and 2024 T-4 aluminium in an ultrahigh vacuum of 10-t° torr were determined experimentally.

Classified abstracts 908-918 For fine grained soils, forces up to 495 dynes/cm = were measured. H E Selheimer and S W Johnson, Rep AD-675138, Sept 1968, 12 pages (Sci Tech Aerospace Reps, 7 (2), 373, N69-12167). 37 908. Production of nickel-copper bimetal by vacuum rolling. (USA). M-I copper and 99.99 nickel sheets, 10 mm thick, vacuum annealed at 700 and 900°C respectively, were slowly cooled, assembled into 20 × 40 × 100 m m packets, pack rolled in vacuum (10 -s torr) at 7501050°C. The influence of vacuum, and temperature on the bond strength is studied. A A Aleksandrov, Rep AD-677247, Nov 1967, p 5-11 (Sci Tech Aerospace Reps, 7 (4), 675, N69-14358). 37 909. Certain factors of optimal influence in electrical discharge machining. (USA) The electrical discharge machining process has become an important manufacturing tool in the field of metal removal. Experimental results show that a workpiece with a medium grind finished surface and under a moderate magnetic field shows significant improvement in metal removal. S S Thomas, Rep Purdae Univ, Univ Microfilms No 68-6369, 115 pages (Sci Tech Aerospace Reps, 7 (2), 301, N69-11996). 37 910. Creep at elevated temperatures and high vacuum. (USA) High temperature, low pressure creep experiments on copper and silver wires show that the surface preparation can effect the creep rate markedly. Tests on copper samples in the argon-bombarded state show a much higher creep rate than after oxidation. K Schroder et al, Rep NASA-CR-97760, Nov 1968, 25 pages (Sci Tech Aerospace Reps, 7 (2), 310, N69-11963). 37 911. Determination of the solubility of oxygen in sodium by vacuum distillation. (USA) The solubility of O,., in Na was determined over the range 125 to 300°C by vacuum distillation. A least-squares fit of the experimental data yielded a correlating equation log y=4.25 -3499[T, where y is wt per cent O=. V J Rutkauskas, Rep LA-3879, July 1968, 12 pages (Sci Tech Aerospace Reps, 7 (4), 624, N69-14704). 37 : 30 912. Pressure effects on the friction coefficient of thin-film solid lubricants. (USA) Thin solid films on harder backings are widely used as dry-film lubricants. The mechanism of lubrication is discussed and it is concluded that the shear strength vs pressure curves of materials are important for defning this mechanism. R C Bowers and W A Zisman, J ApplPhys, 39 (12), 1968, 5385-5395. 39. MISCELLANEOUS APPLICATIONS 39 913. Principles of polycarbonate vacuum-forming. (USA) Thermoforming techniques and equipment are discussed. The two least complex forming-techniques are identified as straight forming into a female mould and drape-forming over a male mould. Mould materials and mould considerations such as stripping, shrinkage and heating are described. R L Pote, New Trends in Thermoplastic sheet processing, (General Electric Co, PittsfieM), 1968, 61-69, (Sci Tech Aerospace Reps, 7 (2), 317, N69-12497).

IV. Materials and techniques used in vacuum technology 40. GASES AND VAPOURS

40 914. Saturated liquid densities of oxygen, nitrogen, argon and parahydrogen. (USA) Integrated tables of pressure, volume and temperature for the saturated liquid, from triple point to the critical point, of oxygen, nitrogen, argon and parahydrogen are presented. Estimates of the uncertainty of the tabulated data are given. H M Roder et al, Rep NBS-TN-361, Jan 1968, 80 pages (Sci Tech Aerospace Reps, 7 (4), 625, N69-14863).

41. METALS AND ALLOYS 41 : 30 Optical properties of dilute silver-indium alloys in the ultraviolet. See abstract number 874. 42. GLASS, CERAMICS AND REFRACTORY OXIDES 42 : 46 915. Research and development programme of thermionic conversion of heat to electricity. (USA) Efforts in the following areas are reported: 1. The development of cesium metallizing-coating for pure alumina ceramics, 2. the development of molybdenum-alumina cermet structures for use as emittercollector seal insulators, 3. the evaluation and development of methods of bonding the metallic surface of insulators to structural parts, 4. long-time testing of materials and seals at high temperature in both vacuum and cesium vapour environments. Anon, General Electric Co Rep AD-674883, GEST-2062-V-2, July 1968, 1 i 5 pages (Sci Tech Aerospace Reps, 7 (2), 216, N69-12129). 42 916. An investigation for fabricating and evaluating the properties of chemically vapour-deposited alumina and magnesia. (USA) The chemical vapour deposition technique for aluminium oxide was investigated and transparent, theoretically dense, alpha-aluminium oxide was produced. By varying tile deposition conditions, white opaque material could be produced. R C Ellis, Rep AD-676150, Oct 1968, 123 pages (Sci Tech Aerospace Reps, 7 (2), 309, N69-11865). 46. GLASS BLOWING, GLASS-TO-METAL AND CERAMICTO-METAL SEALING T E C H N I Q U E S 46 : 42 Research and development programme of thermionic conversion of heat to electricity. See abstract number 915. 46 917. A study of the relationship of atom movements, wettability and adhesion in the glass- metal oxide-metal systems. (USA) The relationship between wettability, atom movements and adhesion in the glass-metal oxide-metal system has been investigated by the measurement of contact angles, electron probe analysis of the transition zone and by mechanical adhesion testing. Several glasses joined to kovar were studied. T N Fogarty, Rep Lehigh Univ, Univ Microfilms No 69-4883, 114 pages (Sci Tech Aerospace Reps, 7 (4), 616, N69-14183). 47. OUTGASSING DATA, VAPOUR PRESSURE DATA, GETTERING, RESIDUAL GASES IN VACUUM SYSTEMS, RESIDUAL GAS ANALYSIS 47:16 Phonic desorption. See abstract number 786. 47 : 16 Re-deposition of vacuum outgassed products. See abstract number 796. 47 : 22 A magnetron-type ion source for low-pressure residual gas analysis. See abstract number 828. 47 : 22 Some properties of the Monopole mass spectrometer. See abstract number 831. 47 : 22 Some causes of poor peak shapes in quadrupole field mass analyzers. See abstract number 832. 47 : 34 Optical surface degradation from combined ultraviolet radiation and outgassed materials. See abstract number 8990 47 918. Outgassing of muitifoil insulation materials in sealed vacuum systems.* (USA) The results of outgassing rate measurements on typical multifoil insulation materials in the temperature range of I00 ° to 1800°F were presented. Rates were determined for aluminium foil, tantalum foil, nickel foil, copper foil, glass-fibre paper, aluminium-opacified glassfibre paper, quartz paper, copper-opacified quartz paper, and quartz cloth. These materials were subjected to periods of vacuum pumping at temperatures IO0°F in excess of the outgassing measurement

389

Classified abstracts 919-920 temperatures. The composition of the desorbed gas was also measured. The 100°F over-temperature bakeout was generally effective in suppressing the outgassing 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 overtemperature so that the length of the bakeout period can be determined for a given desired outgassing rate. R L Reid et al, J Vac Sci Technol, 6 (1), Jan-Feb 1969, 217-221. 47 919. Beimviour of materials in vacuum. (USA) The report describes the techniques used to determine the effects of outgassed materials condensed on MgF~ overcoated aluminium mirrors while the mirrors were irradiated with ultraviolet in vacuum. Mirror temperatures as low as --60°C were used to determine the point at which condensation was incipient. J F Scannapieeo and R N GrilF~n, Rep NASA-CR-97815, Sept 1968, 87 pages (Sci Tech Aerospace Reps, 7 (2), 315, N69-12243).

390

47 920. Some observations on the outgassing of stainless steel following different methods of cleaning. (Great Britain) The quantity and temperature dependence of gas released by stainless steel in vacuum following various forms of cleaning have been investigated using a high resolution mass spectrometer. Each sample was heated over a period of four hours to a temperature of 450°C at which it was maintained for 16 hours. After cooling it was exposed to the air for 24 hours and the amount of gas readsorbed was investigated. R S Barton and R P Gorier, Rep CLM-R-93, March 1968, 15 pages (Sci Tech Aerospace Reps, 7 (4), 678, N69-14752).

*These papers were presented at the Proceedings of the Fifteenth National Vacuum Symposium of the American Vacuum Society and the Thin-Film Symposium of the Thin-Film Division of the American Vacuum Society, which was held from 28 October-I November 1968 at Pittsburgh, Pennsylvania, USA.