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New rapid method of measurement for very small surface areas of solids. (Japan)
Classified abstracts 364-503 Classified abstracts 364-371 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 vacuum science and engineering 12. MEASUREMENT OF LOW PRESSURES 12:22 364. International standards and development trends in measurement of total pressure. (Germany) A review covering recent advances in the measurement of total pressure over the whole vacuum range is presented. The pressure range, in which vacuum technique is involved, covers 15 orders of magnitude. There is no known measuring principle which could be applied over the whole vacuum range. A brief analysis of literature published on total pressure measurement during the three years from 1967 to 1969 shows that 50 per cent of publications concern the problems of hot cathode ionization gauges, and that research and development is more concerned with improvement of the known measuring methods than in the development of new methods. Mechanical manometers, particularly liquid level manometers and their measuring errors are briefly discussed. Advances in total pressure measurement based on the hot cathode ionization gauge are considered in some detail. The main sources of disturbance, namely the x-ray photoeffect, ion desorption due to electron bombardment of the grid, and chemical reactions occurring on surface of the hot cathode, are discussed. Improved hot cathode ionization gauges with a modulator, external collector, suppressor electrodes, and ion extraction mechanism, are covered. Also, ionization gauges with separated electron source and ionization space regions are dealt with. The calibration of vacuum gauges is discussed. H Thurandt, Experi Tech Phys, 18 (1-2), 1970, 1-11 (in German). 16. GASES AND SOLIDS 16 365. New rapid method of measurement for very small surface areas of solids. (Japan) The surface area of solids, having surface areas in the range 10 to 100 cm 2, may be rapidly and precisely measured by a new device using xenon adsorption. The apparatus includes a sputter-ion pumped vacuum system capable of 10-9 torr and two pressure measurement sections designated "adsorption cell" (250 cc) and "reference cell" (160 cc) respectively. After the sample has been outgassed and cooled to liquid nitrogen temperature, xenon gas is admitted into the adsorption cell from the reference cell which stores the xenon gas at between 2 and 5 × 10-2 cc STP. The amount of adsorbed gas may be estimated from the change in pressure in each section. A BET plot with four or five points may be obtained in half an hour and reproducibility of the surface area value has been found to be better than two per cent. Typical results obtained on glass and quartz surfaces are in good agreement with those of other workers. K Watunabe and T Yamashina, J Vac Soc Japan, 13 (10), 1970, 327-332 (in Japanese). 16 366. Adsorption of oxygen on tungsten and its application to the measurement of oxygen partial pressure. (France) Oxygen adsorbs on tungsten much more strongly than other gases. The resultant increase in the work function was measured as a function of oxygen perssure and tungsten temperature, using an ionization gauge. For a constant emission current, it can be shown that there is a linear dependence between the filament heating current and the oxygen pressure. The effect of other gases is negligible. P Batzies, Le Vide, 25 (148-149), July~Oct 1970, 198-202 (in French). 16 367. Apparatus for the study of the electron impact desorpfion of ions and neutrals from solid surfaces. (USA) A cylindrical magnetic spectrometer for the study of the electron impact desorption of ions and neutrals from solid surfaces is described. 240
The instrument has an energy resolution of approximately 4 per cent and sufficient sensitivity to allow the measurement of the ion energy distributions for systems in which the ion yield is 10-9 ions per electron or greater. In addition, the apparatus allows the determination of the mass-to-charge ratio of the emitted ions. The design of the apparatus and experimental procedures are discussed. Examples of typical measurements are reported. M Nishijima and F M Propst, J Vac Sci Technol, 7 (3), May/June 1970, 410-419. 16 368. Kinetics of electron impact desorption of ions and neutrals from polycrystalline tungsten. (USA) A cylindrical magnetic spectrometer has been constructed to study electron impact desorption of ions and neutrals from solid surfaces. The apparatus has been applied to the study of polycrystalline tungsten with Oz, CO, CO=, N=, H=, and H=O adsorbed. This paper reports the results of the measurements of the kinetics of the adsorption and desorption processes, the states of adsorption which are observed, the total desorption cross sections for these states, and electronic and thermal conversion between states. M Nishijima and F M Propst, J Vac Sci Technol, 7 (3), May/June 1970, 420-428. 16 369. Physisurption of nitrogen on 304 stainless steel at very low pressures. (USA) Physisorption isotherms have been measured for nitrogen on 304 stainless steel in the temperature range 77-90 K and in the pressure range 10-9-10 -4 tort. A static technique was used to obtain the isotherms whereby the pressure change of nitrogen in a constant volume system was measured on immersion of the test surface in different cryogenic baths. The Dubinin-Radushkevich equation provided a good correlation of the data and the extrapolated value for monolayer coverage of 6.6× 1014 molecules/cm2 indicated a roughness factor near unity for stainless steel. The isoteric heat of adsorption of nitrogen on stainless steel remained constant at about 4.4 kcal/mole in the range of surface coverages from 0.02-0.08. M Troy and J P Wightman, J Vac Sci Technol, 7 (3), May/June 1970, 429433. 16 370. Multiple collision method of measuring sticking coefficients and studying reflections on oxide surfaces. (USA) A new method of measuring sticking coefficients using multiple surface collisions of vapour is presented. Metal vapours pass from a cup into a long hollow, right cylindrical tube where they come to rest after one or more strikes on the inner surface of the tube. Analysis of the data are made by Monte Carlo statistical calculations of the behaviour of atoms in a similar (though hypothetical) tube and using various assumptions regarding sticking coefficients and types of reflections. The sticking coefficient for silver on Pyrex in a residual vacuum of approximately 10-5 torr and 20°C is 0.68 -4- 0.02. Reflections from Pyrex surfaces are shown, within experimental uncertainty, to be satisfactorily diffuse. R F Benck et al, J Vac Sci Technol, 7 (3), May/June 1970, 403409. 16 371. Gas discharge cleaning of vacuum surfaces. (USA) The efficiency of glow discharges in He, Ne, and Ar for the removal of H20, CO, and CO= from the surface of vacuum systems has been demonstrated. However, re-emission of the rare gas and of hydrogen atoms trapped in the surface during the discharge cause the total outgassing rate not to be significantly reduced. In general, as the pressure of the discharge increases, the efficiency of cleaning decreases, and this has been correlated with a decrease in the number of energetic ions hitting the surfaces. R P Gorier and G M McCracken, J Vae Sci Technol, 7 (5), Sept~Oct 1970, 552-558.
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 vacuum science and engineering 12. MEASUREMENT OF LOW PRESSURES 12:22 364. International standards and development trends in measurement of total pressure. (Germany) A review covering recent advances in the measurement of total pressure over the whole vacuum range is presented. The pressure range, in which vacuum technique is involved, covers 15 orders of magnitude. There is no known measuring principle which could be applied over the whole vacuum range. A brief analysis of literature published on total pressure measurement during the three years from 1967 to 1969 shows that 50 per cent of publications concern the problems of hot cathode ionization gauges, and that research and development is more concerned with improvement of the known measuring methods than in the development of new methods. Mechanical manometers, particularly liquid level manometers and their measuring errors are briefly discussed. Advances in total pressure measurement based on the hot cathode ionization gauge are considered in some detail. The main sources of disturbance, namely the x-ray photoeffect, ion desorption due to electron bombardment of the grid, and chemical reactions occurring on surface of the hot cathode, are discussed. Improved hot cathode ionization gauges with a modulator, external collector, suppressor electrodes, and ion extraction mechanism, are covered. Also, ionization gauges with separated electron source and ionization space regions are dealt with. The calibration of vacuum gauges is discussed. H Thurandt, Experi Tech Phys, 18 (1-2), 1970, 1-11 (in German). 16. GASES AND SOLIDS 16 365. New rapid method of measurement for very small surface areas of solids. (Japan) The surface area of solids, having surface areas in the range 10 to 100 cm 2, may be rapidly and precisely measured by a new device using xenon adsorption. The apparatus includes a sputter-ion pumped vacuum system capable of 10-9 torr and two pressure measurement sections designated "adsorption cell" (250 cc) and "reference cell" (160 cc) respectively. After the sample has been outgassed and cooled to liquid nitrogen temperature, xenon gas is admitted into the adsorption cell from the reference cell which stores the xenon gas at between 2 and 5 × 10-2 cc STP. The amount of adsorbed gas may be estimated from the change in pressure in each section. A BET plot with four or five points may be obtained in half an hour and reproducibility of the surface area value has been found to be better than two per cent. Typical results obtained on glass and quartz surfaces are in good agreement with those of other workers. K Watunabe and T Yamashina, J Vac Soc Japan, 13 (10), 1970, 327-332 (in Japanese). 16 366. Adsorption of oxygen on tungsten and its application to the measurement of oxygen partial pressure. (France) Oxygen adsorbs on tungsten much more strongly than other gases. The resultant increase in the work function was measured as a function of oxygen perssure and tungsten temperature, using an ionization gauge. For a constant emission current, it can be shown that there is a linear dependence between the filament heating current and the oxygen pressure. The effect of other gases is negligible. P Batzies, Le Vide, 25 (148-149), July~Oct 1970, 198-202 (in French). 16 367. Apparatus for the study of the electron impact desorpfion of ions and neutrals from solid surfaces. (USA) A cylindrical magnetic spectrometer for the study of the electron impact desorption of ions and neutrals from solid surfaces is described. 240
The instrument has an energy resolution of approximately 4 per cent and sufficient sensitivity to allow the measurement of the ion energy distributions for systems in which the ion yield is 10-9 ions per electron or greater. In addition, the apparatus allows the determination of the mass-to-charge ratio of the emitted ions. The design of the apparatus and experimental procedures are discussed. Examples of typical measurements are reported. M Nishijima and F M Propst, J Vac Sci Technol, 7 (3), May/June 1970, 410-419. 16 368. Kinetics of electron impact desorption of ions and neutrals from polycrystalline tungsten. (USA) A cylindrical magnetic spectrometer has been constructed to study electron impact desorption of ions and neutrals from solid surfaces. The apparatus has been applied to the study of polycrystalline tungsten with Oz, CO, CO=, N=, H=, and H=O adsorbed. This paper reports the results of the measurements of the kinetics of the adsorption and desorption processes, the states of adsorption which are observed, the total desorption cross sections for these states, and electronic and thermal conversion between states. M Nishijima and F M Propst, J Vac Sci Technol, 7 (3), May/June 1970, 420-428. 16 369. Physisurption of nitrogen on 304 stainless steel at very low pressures. (USA) Physisorption isotherms have been measured for nitrogen on 304 stainless steel in the temperature range 77-90 K and in the pressure range 10-9-10 -4 tort. A static technique was used to obtain the isotherms whereby the pressure change of nitrogen in a constant volume system was measured on immersion of the test surface in different cryogenic baths. The Dubinin-Radushkevich equation provided a good correlation of the data and the extrapolated value for monolayer coverage of 6.6× 1014 molecules/cm2 indicated a roughness factor near unity for stainless steel. The isoteric heat of adsorption of nitrogen on stainless steel remained constant at about 4.4 kcal/mole in the range of surface coverages from 0.02-0.08. M Troy and J P Wightman, J Vac Sci Technol, 7 (3), May/June 1970, 429433. 16 370. Multiple collision method of measuring sticking coefficients and studying reflections on oxide surfaces. (USA) A new method of measuring sticking coefficients using multiple surface collisions of vapour is presented. Metal vapours pass from a cup into a long hollow, right cylindrical tube where they come to rest after one or more strikes on the inner surface of the tube. Analysis of the data are made by Monte Carlo statistical calculations of the behaviour of atoms in a similar (though hypothetical) tube and using various assumptions regarding sticking coefficients and types of reflections. The sticking coefficient for silver on Pyrex in a residual vacuum of approximately 10-5 torr and 20°C is 0.68 -4- 0.02. Reflections from Pyrex surfaces are shown, within experimental uncertainty, to be satisfactorily diffuse. R F Benck et al, J Vac Sci Technol, 7 (3), May/June 1970, 403409. 16 371. Gas discharge cleaning of vacuum surfaces. (USA) The efficiency of glow discharges in He, Ne, and Ar for the removal of H20, CO, and CO= from the surface of vacuum systems has been demonstrated. However, re-emission of the rare gas and of hydrogen atoms trapped in the surface during the discharge cause the total outgassing rate not to be significantly reduced. In general, as the pressure of the discharge increases, the efficiency of cleaning decreases, and this has been correlated with a decrease in the number of energetic ions hitting the surfaces. R P Gorier and G M McCracken, J Vae Sci Technol, 7 (5), Sept~Oct 1970, 552-558.