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3134. Molecular fractionation and jet stills
Classified abstracts 3127-3136 31 3127. The regulation of pressure in a radio-frequency sputtering device. (France) In order to obtain reproductible results in RF sputtering we describe here an experimental device which permits us to adjust the pressure, in the range from 2.10 -3 to 6.10-'* torr, with a precision of +0.1 10 -'~ torr. This device associated with an UHV unit is used to evaporate thin films of various materials, the thickness of which is a lineal" function of sputtering duration. L Protin, Vide, 31 (185), 1976, 167-174 (hl French). 31 3128. Influence of the manufacturing parameters on film structure and properties of reactively sputtered vanadium dioxide films. (France) The resistance-temperature characteristic is primarily influenced by the grain size of the films. It has been shown that the resistivity jump, transition temperature and the width of hysteresis loop may be changed by means of control of grain size. The shift of transition temperature explained on the basis of interior stresses in thin films caused by the film structure. (Germany) D Biihling and L Miehalowsky, Vide, 31 (185), 1976, 185-188.
33. NUCLEONICS 33 3129. Secondary electron emission from solid hydrogen and deuterium resulting from incidence of keV electrons and hydrogen ions. (USA) The secondary electron emission (SEE) coefficient 8 was measured for solid hydrogen and deuterium resulting from the normal incidence of 0.5-3-keV electrons and 4-10-keV H +, H2 +, H3 +, and D3 + ions. The SEE coefficients for solid hydrogen are 60-70% of those for solid deuterium, and the coefficients are small, in contrast to what is expected for insulating materials. One explanation is that the secondary electrons lose energy inside the target material by exciting vibrational and rotational states of the molecules, so that the number of electrons that may escape as secondary electrons is rather small. The losses to molecular states will be largest for hydrogen, so that the SEE coefficients are smallest for solid hydrogen, as was observed. For the incidence of ions, the values of 8 for the different molecular ions agree when the number of secondary electrons per incident atom is plotted versus the velocity or the stopping power of the incident particles. Measurements were also made for oblique incidence of H + ions on solid deuterium for angles of incidence up to 75 °. A correction could be made for the emission of secondary ions by also measuring the current calorimetrically. At largest energies, the angular dependence corresponds to 8(0) = ,~(0) (cos0)- ~. (Denmark) H Sorensen, J Appl Phys, 48 (6), 1977, 2244-2251. 33 3130. Extraction of an ion beam from a diverter-type plasma source. (USA) A multiple-aperture ion source using a diverter plasma source has been developed. The density profile of the source plasma is uniform to :k7% across a diameter of 5.6 cm. An ion beam of 4 keV, 0.2 A has been extracted from the ion source. The experimentally obtained perveance is about half of the theoretical value. The ion source has the potential to be a high-current ion source. (Japan) K Yatsu et al, Rev Set Instrum, 48 (5), 1977, 571-572.
34. ELECTRONICS AND HIGH ALTITUDE PHYSICS AND TECHNOLOGY 34 3131. Measurements of the velocity spectrum of a thermal Sin-atomic beam by means o f an optical spectrometer. (Germany) By means of an optical spectrometer which is based on the velocityselective excitation of particles by a tunable dye laser, velocity measurements have been performed on a thermal Sm-atomic beam. For this reason the resonant transitions 4f%s 2 7 F o - 4f%s6p 7F7 and 4f%s z 7F l -- 4f55d6s 2 VH2 have been investigated. The isotope shifts and hyperfme splittings of the four terms have been measured. It could be shown that only the transition 4f%s 2 7F t -- 4f55d6s z 7H2 is suited for velocity measurements based on the Doppler shift of absorption lines. (Austria) Von W Husinsky et al, Vakuum-Tech, 26 (4), 1977, 99-103 (in German).
666
35. PROCESSING OF MATERIALS 35 3132. Electron-beam melting of Ti-6AI,4V. (USA) A program to recycle Ti-6AI-4V machine chip scrap by electronbeam (EB) melting is described. The advantages of utilizing EB melting arc described in terms of the selection of raw materials, the unique characteristics of the EB hearth furnace, the alloying and refining reactions that are promoted, and the unique character of tile solidification process. Experimental results are presented on a manufacturing technology program sponsored by the Air Force Materials Laboratory in which machined chips, sponge, and alloy elements are recycled into specification grade Ti-6AI-4V bar stock. T Landig et al, J Vac Sci Technol, 14 (3), 1977, 808-814. 35 3133. Reduction of niobium pentoxide in a hydrogen discharge. (USA) When exposed to "active hydroget( from a microwave discharge, white ~-niobium pentoxide becomes gray-black. This reduction product has been examined by several techniqttes, including Auger electron spectroscopy. It is fotmd that the material within a few tenths of a micrometer from the surface is reduced to niobium dioxide, and that the remaining Nb,O.~ remains unchanged. (Canada) M R Wertheimer and J P Bailon, J Vac Sci Technol, 14 (2), 1977, 699-704. 35 3134. Molecular fractionation and jet stills. (USA) Working equations are derived for tile quantitative design of stills for molecular distillation. The distillation rates and the separation efficiencies in the molecular stills are correlated to the exposure time and the renewal rate of the evaporating surface. A method of interconnecting a number of jet stills to form a molecular fractionator and an example of step-by-step design procedure are also presented. (Taiwan) Jer Ru Maa, J Vac Sci Techm~l, 14 (2), 1977, 723-730. 35 3135. Outgassing from epoxy resins and methods for its reduction. (GB) Due to the ease of moulding light components of any shape, excellent electrical insulation and nonrnagnetic properties of epoxy resins, their use in vacuum systems is quite wide spread. However, their relatively high outgassing rates--approximately one hundred times that of unbaked glass or metals and one million times that of baked glass and metals--is a serious drawback and can cause formidable vacuum problems unless this aspect is duly considered in the design. This effect is usually manifested in impracticably high pumping speeds which would be required to attain pressures below 10 -5 torr (10 -3 Pa), in systems using large surface areas of epoxy. In situations where large epoxy surfaces are unavoidable, some means of reducing the outgassing rate would be desirable. This paper presents the results of many trials in this direction. It was found that outgassing rate can be reduced by an aquadag coating (by a factor of 5), by a vacuum evaporated aluminium coating (by a factor of 10) or by cladding with aluminium or stainless steel foils (by a factor of 20). However, these surface treatments would obviously affect the surface dependent electrical properties of the epoxy. (India) A K Gupta et al, Vaclttlm, 27 (2), 1977, 61-63.
36. VACUUM INSTRUMENTATION FOR SURFACE STUDIES 36 3136. Photoemission and LEED study of indium phosphide with a determination of minority carrier diffusion length. (USA) Photoemission measurements were taken in indium phosphide from the band gap to 1.8 eV photon energies. The surface activation procedure using cesium and oxygen is described. The condition of the surface was monitored for its crystallinity by a low-energyelectron-diffraction (LEED) camera, and for its purity by Auger electron spectroscopy. The work functions were measured by the electron beam retarding potential method to determine the consequence of the activation processes. The result of the LEED analyses and the work-function measurements indicate that the activation takes place on the surface in a patchy form. The results of the photoemission data are analyzed in light of the three-step diffusion model photoemission theory. From the data of the photoemission, the bulk diffusion length is determined to be 530 nm and the surface escape probability to be less than 0.025. Correlating the results of
33. NUCLEONICS 33 3129. Secondary electron emission from solid hydrogen and deuterium resulting from incidence of keV electrons and hydrogen ions. (USA) The secondary electron emission (SEE) coefficient 8 was measured for solid hydrogen and deuterium resulting from the normal incidence of 0.5-3-keV electrons and 4-10-keV H +, H2 +, H3 +, and D3 + ions. The SEE coefficients for solid hydrogen are 60-70% of those for solid deuterium, and the coefficients are small, in contrast to what is expected for insulating materials. One explanation is that the secondary electrons lose energy inside the target material by exciting vibrational and rotational states of the molecules, so that the number of electrons that may escape as secondary electrons is rather small. The losses to molecular states will be largest for hydrogen, so that the SEE coefficients are smallest for solid hydrogen, as was observed. For the incidence of ions, the values of 8 for the different molecular ions agree when the number of secondary electrons per incident atom is plotted versus the velocity or the stopping power of the incident particles. Measurements were also made for oblique incidence of H + ions on solid deuterium for angles of incidence up to 75 °. A correction could be made for the emission of secondary ions by also measuring the current calorimetrically. At largest energies, the angular dependence corresponds to 8(0) = ,~(0) (cos0)- ~. (Denmark) H Sorensen, J Appl Phys, 48 (6), 1977, 2244-2251. 33 3130. Extraction of an ion beam from a diverter-type plasma source. (USA) A multiple-aperture ion source using a diverter plasma source has been developed. The density profile of the source plasma is uniform to :k7% across a diameter of 5.6 cm. An ion beam of 4 keV, 0.2 A has been extracted from the ion source. The experimentally obtained perveance is about half of the theoretical value. The ion source has the potential to be a high-current ion source. (Japan) K Yatsu et al, Rev Set Instrum, 48 (5), 1977, 571-572.
34. ELECTRONICS AND HIGH ALTITUDE PHYSICS AND TECHNOLOGY 34 3131. Measurements of the velocity spectrum of a thermal Sin-atomic beam by means o f an optical spectrometer. (Germany) By means of an optical spectrometer which is based on the velocityselective excitation of particles by a tunable dye laser, velocity measurements have been performed on a thermal Sm-atomic beam. For this reason the resonant transitions 4f%s 2 7 F o - 4f%s6p 7F7 and 4f%s z 7F l -- 4f55d6s 2 VH2 have been investigated. The isotope shifts and hyperfme splittings of the four terms have been measured. It could be shown that only the transition 4f%s 2 7F t -- 4f55d6s z 7H2 is suited for velocity measurements based on the Doppler shift of absorption lines. (Austria) Von W Husinsky et al, Vakuum-Tech, 26 (4), 1977, 99-103 (in German).
666
35. PROCESSING OF MATERIALS 35 3132. Electron-beam melting of Ti-6AI,4V. (USA) A program to recycle Ti-6AI-4V machine chip scrap by electronbeam (EB) melting is described. The advantages of utilizing EB melting arc described in terms of the selection of raw materials, the unique characteristics of the EB hearth furnace, the alloying and refining reactions that are promoted, and the unique character of tile solidification process. Experimental results are presented on a manufacturing technology program sponsored by the Air Force Materials Laboratory in which machined chips, sponge, and alloy elements are recycled into specification grade Ti-6AI-4V bar stock. T Landig et al, J Vac Sci Technol, 14 (3), 1977, 808-814. 35 3133. Reduction of niobium pentoxide in a hydrogen discharge. (USA) When exposed to "active hydroget( from a microwave discharge, white ~-niobium pentoxide becomes gray-black. This reduction product has been examined by several techniqttes, including Auger electron spectroscopy. It is fotmd that the material within a few tenths of a micrometer from the surface is reduced to niobium dioxide, and that the remaining Nb,O.~ remains unchanged. (Canada) M R Wertheimer and J P Bailon, J Vac Sci Technol, 14 (2), 1977, 699-704. 35 3134. Molecular fractionation and jet stills. (USA) Working equations are derived for tile quantitative design of stills for molecular distillation. The distillation rates and the separation efficiencies in the molecular stills are correlated to the exposure time and the renewal rate of the evaporating surface. A method of interconnecting a number of jet stills to form a molecular fractionator and an example of step-by-step design procedure are also presented. (Taiwan) Jer Ru Maa, J Vac Sci Techm~l, 14 (2), 1977, 723-730. 35 3135. Outgassing from epoxy resins and methods for its reduction. (GB) Due to the ease of moulding light components of any shape, excellent electrical insulation and nonrnagnetic properties of epoxy resins, their use in vacuum systems is quite wide spread. However, their relatively high outgassing rates--approximately one hundred times that of unbaked glass or metals and one million times that of baked glass and metals--is a serious drawback and can cause formidable vacuum problems unless this aspect is duly considered in the design. This effect is usually manifested in impracticably high pumping speeds which would be required to attain pressures below 10 -5 torr (10 -3 Pa), in systems using large surface areas of epoxy. In situations where large epoxy surfaces are unavoidable, some means of reducing the outgassing rate would be desirable. This paper presents the results of many trials in this direction. It was found that outgassing rate can be reduced by an aquadag coating (by a factor of 5), by a vacuum evaporated aluminium coating (by a factor of 10) or by cladding with aluminium or stainless steel foils (by a factor of 20). However, these surface treatments would obviously affect the surface dependent electrical properties of the epoxy. (India) A K Gupta et al, Vaclttlm, 27 (2), 1977, 61-63.
36. VACUUM INSTRUMENTATION FOR SURFACE STUDIES 36 3136. Photoemission and LEED study of indium phosphide with a determination of minority carrier diffusion length. (USA) Photoemission measurements were taken in indium phosphide from the band gap to 1.8 eV photon energies. The surface activation procedure using cesium and oxygen is described. The condition of the surface was monitored for its crystallinity by a low-energyelectron-diffraction (LEED) camera, and for its purity by Auger electron spectroscopy. The work functions were measured by the electron beam retarding potential method to determine the consequence of the activation processes. The result of the LEED analyses and the work-function measurements indicate that the activation takes place on the surface in a patchy form. The results of the photoemission data are analyzed in light of the three-step diffusion model photoemission theory. From the data of the photoemission, the bulk diffusion length is determined to be 530 nm and the surface escape probability to be less than 0.025. Correlating the results of