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3882. Differentially pumped 6 in. metal sealed gate valve. (USA)
Classified abstracts 3881-3890 22. G A U G E S A N D M E A S U R E M E N T O F LOW PRESSURES
25. H E A T I N G E Q U I P M E N T A N D T H E R M O M E T E R S
22 3881. Simple vacuum gauge using TaN thin films in the pressure range of 10 s to 10 -3 Pa. (USA) Experiments investigating the use of TaN thin films for measurements of pressure over a wide range have proved to give good results, because the TaN thin films have large effective heat conducting areas available to increase the sensitivity, suitable resistance and large temperatures coefficients of resistance. These experiments led to the construction of a film system consisting of a TaN thin film deposited on a miniature 7059 Corning glass substrate by reactive plasma sputtering. With this system, it is possible to measure pressure changes in the range of l0 s to l0 -3 Pa. A detailed description of the characteristics of the TaN film gauge as well as the'calibration curves are given. (Japan). T Shioyama et al, J Vac Sci Technol, 15 (2), 1978, 761-763.
25 3887. Glow discharge processing vs bakeout for aluminum storage ring vacuum chambers. (USA) Experiments were carried out on laboratory and prototype scale systems in order to establish the feasibility of argon discharge processing the PEP storage ring aluminium vacuum chambers. Electroninduced desorption rates showed significant reductions following bakeout and/or argon glow discharge treatment ( > l0 t9 ions c m - ~). Data are presented and discussed in relation to advantages and problems associated with: water removal, argon trapping and subsequent release, electron energy dependence, discharge distribution and surface plasma chemical effects. N R Dean et al, J Vac Sci Teehnol, 15 (2), 1978, 758-760.
III. Vacuum applications 23. P L U M B I N G , V A C U U M VALVES, BAFFLES A N D TRAPS 23 3882. Differentially pumped 6 in. metal sealed gate valve. (USA) Vacuum valves rely on an ability to make and remake intimate contact between their seal and seat materials over their entire main seal perimeters. In many applications, valves must be operable in the presence of small amounts of particulate matter. In such applications, a common failure mode for both metal and elastomer sealed valves results from the inadvertent incorporation of foreign particles into the main seal area during their operation. The use of a back-up seal with differential pumping of the intermediate space is a well-known technique for reducing the effect of small leaks. A modification to allow differential pumping of the main seal of a 6 in. metal sealed valve described previously is discussed. Experimental results obtained with a modified valve are presented. D J Harra, J Vac Sci Technol, 15 (2), 1979, 779-782. 23 3883. Precision molecular flow measurement and control for single and multigas systems. (USA) This paper presents recent advances in precision molecular flow measurement and control for single backfill gases as well as describing the important factors to be considered in multigas flow and ratio control of several gases at pressures above 0.0133 Pa. A comprehensive theoretical analysis is given describing the variables to be considered in practical systems. Theoretical and experimental data are presented on a new design of molecular flow element specifically designed for vacuum flow applications of any gas, including corrosive types. Single and multigas measurement and control applications using the new flow element with electronic manometer measurement and control instrumentation include reactive sputtering, reactive ion etching, and plasma reactor deposition and etching systems. R A Kiesling et al, J Vac Sci Technol, 15 (2), 1978, 771-774. 23 3884. Versatile electrical feedthrough for probe measurements in vaeuo. (USA) An electrical feedthrough, operating at 10 -6 torr, for use in vacuum systems utilizing Swagelock or Wilson-type seals is described. It features a pair of centre conductors with a coaxial shield and can be used with a variety of detachable probes. D N Spectur et al, Rev scient Instrum, 49 (7), 1978, 1010-1011. 23 3885. Fast hydrogen gas injection system for plasma physics experiments. (USA) A system has been developed for fast injection of hydrogen gas into a vacuum system, which can produce feedback controlled flows in the range 0.1-10 tort I/s. The unit uses a fast pressure transducer as a flow sensor. The flow will respond to an external programming voltage whose time variation is as short as several milliseconds. K H Burrell, Rev scient Instrum, 49 (7), 1978, 948-954. 23 3886. Fast valve for gas injection into vacuum. (USA) A simple, fast, reliable magnetically driven gas valve for use in plasma experiments is described. The pressure rise time has been measured to be ~ 1 torr/~s at the valve opening. A Fisher et al, Rev scient lnstrum, 49 (6), 1978, 872-873.
30. EVAPORATION A N D DEPOSITION I N VACUO 30 3888. Interface states at the Ga-GaAs interface. (USA) A variable-excitation energy photoemission study has been made of the occupied states near the G a - G a A s (110) interface as the interface is formed. Using a combination of valence and core-level spectroscopy, new aspects of the interface electronic structure have been deduced. Using valence-band spectroscopy, interface states are found to appear as the Ga film is built up. Using core-level spectroscopy, one finds chemical shifts in both the Ga and As 3d levels. T h e ~ . s shift indicates that surface charge redistribution from the As t o ~ e Ga occurs at the interface. / R Z Bachrach and A Bianconi, J Vac Sci Technol, 15 (2), 1978, 525-528. 30 3889. de-bias-dependent dielectric dispersion properties of evaporated silicon oxide films. (GB) The measurements of low-frequency dielectric dispersion properties of evaporated silicon oxide films under high dc biasing voltage are reported. The results show that the total conductance consists of frequency-dependent and independent parts. The latter part agrees with the differential conductance derived from the dc 1- V characteristics and it increases with increasing dc biasing voltage. The former part, which contributes to the relaxation phenomena, decreases with increasing of dc biasing voltage. The results of the de-bias-dependent relaxation phenomena are interpreted by using the two-site hopping model, which is consistent with the results of an electrically excited thermally stimulated current (ETSC) and an absorption current. (Japan). Hiroshi Adachi et al, J Phys D: Appl Phys, 11 (10), 1978, 1421-1424. 3O 3890. Debye-like dielectric dispersion properties of evaporated silicon oxide films at very low frequencies. (GB) Dielectric dispersion properties of evaporated silicon oxide films sandwiched between Al electrodes are reported for the frequency range from 0.1 Hz to 20 kHz and the results are analysed by comparing them with the ETSC (electrically excited thermally stimulated current) and the dc current-voltage characteristics. It is shown that the total conductance measured by the ac bridge method is constructed of dc and ac conductivities, as expressed by the empirical relation a(to) = an= + o,=(to). Only the ac conductivity is related to the dielectric dispersion properties, which is Debye-like; that is, the imaginary part of the complex dielectric constant deduced from the ac conductivity has a maximum around the relaxation frequency, which is determined from the frequency dependence of the capacitance. The activation energy and the frequency factor of the relaxation frequency are in good agreement with those deduced from the ETSC results. At a frequency moderately higher than the relaxation frequency, the ac conductivity obeys the empirical relation a==oo toO x 66. The frequency range over which the empirical relation holds is about four decades, which is much narrower than the results of Frost and Jonscher (1975). As far as the experimental results are concerned, there are no contradictions in the interpretation that the dc and ac conductances are originated from mutually independent mechanisms. (Japan). Hireshi Adachi et al, J Phys D: Appl Phys, 11 (8), 1978, 1211-1220. 187
25. H E A T I N G E Q U I P M E N T A N D T H E R M O M E T E R S
22 3881. Simple vacuum gauge using TaN thin films in the pressure range of 10 s to 10 -3 Pa. (USA) Experiments investigating the use of TaN thin films for measurements of pressure over a wide range have proved to give good results, because the TaN thin films have large effective heat conducting areas available to increase the sensitivity, suitable resistance and large temperatures coefficients of resistance. These experiments led to the construction of a film system consisting of a TaN thin film deposited on a miniature 7059 Corning glass substrate by reactive plasma sputtering. With this system, it is possible to measure pressure changes in the range of l0 s to l0 -3 Pa. A detailed description of the characteristics of the TaN film gauge as well as the'calibration curves are given. (Japan). T Shioyama et al, J Vac Sci Technol, 15 (2), 1978, 761-763.
25 3887. Glow discharge processing vs bakeout for aluminum storage ring vacuum chambers. (USA) Experiments were carried out on laboratory and prototype scale systems in order to establish the feasibility of argon discharge processing the PEP storage ring aluminium vacuum chambers. Electroninduced desorption rates showed significant reductions following bakeout and/or argon glow discharge treatment ( > l0 t9 ions c m - ~). Data are presented and discussed in relation to advantages and problems associated with: water removal, argon trapping and subsequent release, electron energy dependence, discharge distribution and surface plasma chemical effects. N R Dean et al, J Vac Sci Teehnol, 15 (2), 1978, 758-760.
III. Vacuum applications 23. P L U M B I N G , V A C U U M VALVES, BAFFLES A N D TRAPS 23 3882. Differentially pumped 6 in. metal sealed gate valve. (USA) Vacuum valves rely on an ability to make and remake intimate contact between their seal and seat materials over their entire main seal perimeters. In many applications, valves must be operable in the presence of small amounts of particulate matter. In such applications, a common failure mode for both metal and elastomer sealed valves results from the inadvertent incorporation of foreign particles into the main seal area during their operation. The use of a back-up seal with differential pumping of the intermediate space is a well-known technique for reducing the effect of small leaks. A modification to allow differential pumping of the main seal of a 6 in. metal sealed valve described previously is discussed. Experimental results obtained with a modified valve are presented. D J Harra, J Vac Sci Technol, 15 (2), 1979, 779-782. 23 3883. Precision molecular flow measurement and control for single and multigas systems. (USA) This paper presents recent advances in precision molecular flow measurement and control for single backfill gases as well as describing the important factors to be considered in multigas flow and ratio control of several gases at pressures above 0.0133 Pa. A comprehensive theoretical analysis is given describing the variables to be considered in practical systems. Theoretical and experimental data are presented on a new design of molecular flow element specifically designed for vacuum flow applications of any gas, including corrosive types. Single and multigas measurement and control applications using the new flow element with electronic manometer measurement and control instrumentation include reactive sputtering, reactive ion etching, and plasma reactor deposition and etching systems. R A Kiesling et al, J Vac Sci Technol, 15 (2), 1978, 771-774. 23 3884. Versatile electrical feedthrough for probe measurements in vaeuo. (USA) An electrical feedthrough, operating at 10 -6 torr, for use in vacuum systems utilizing Swagelock or Wilson-type seals is described. It features a pair of centre conductors with a coaxial shield and can be used with a variety of detachable probes. D N Spectur et al, Rev scient Instrum, 49 (7), 1978, 1010-1011. 23 3885. Fast hydrogen gas injection system for plasma physics experiments. (USA) A system has been developed for fast injection of hydrogen gas into a vacuum system, which can produce feedback controlled flows in the range 0.1-10 tort I/s. The unit uses a fast pressure transducer as a flow sensor. The flow will respond to an external programming voltage whose time variation is as short as several milliseconds. K H Burrell, Rev scient Instrum, 49 (7), 1978, 948-954. 23 3886. Fast valve for gas injection into vacuum. (USA) A simple, fast, reliable magnetically driven gas valve for use in plasma experiments is described. The pressure rise time has been measured to be ~ 1 torr/~s at the valve opening. A Fisher et al, Rev scient lnstrum, 49 (6), 1978, 872-873.
30. EVAPORATION A N D DEPOSITION I N VACUO 30 3888. Interface states at the Ga-GaAs interface. (USA) A variable-excitation energy photoemission study has been made of the occupied states near the G a - G a A s (110) interface as the interface is formed. Using a combination of valence and core-level spectroscopy, new aspects of the interface electronic structure have been deduced. Using valence-band spectroscopy, interface states are found to appear as the Ga film is built up. Using core-level spectroscopy, one finds chemical shifts in both the Ga and As 3d levels. T h e ~ . s shift indicates that surface charge redistribution from the As t o ~ e Ga occurs at the interface. / R Z Bachrach and A Bianconi, J Vac Sci Technol, 15 (2), 1978, 525-528. 30 3889. de-bias-dependent dielectric dispersion properties of evaporated silicon oxide films. (GB) The measurements of low-frequency dielectric dispersion properties of evaporated silicon oxide films under high dc biasing voltage are reported. The results show that the total conductance consists of frequency-dependent and independent parts. The latter part agrees with the differential conductance derived from the dc 1- V characteristics and it increases with increasing dc biasing voltage. The former part, which contributes to the relaxation phenomena, decreases with increasing of dc biasing voltage. The results of the de-bias-dependent relaxation phenomena are interpreted by using the two-site hopping model, which is consistent with the results of an electrically excited thermally stimulated current (ETSC) and an absorption current. (Japan). Hiroshi Adachi et al, J Phys D: Appl Phys, 11 (10), 1978, 1421-1424. 3O 3890. Debye-like dielectric dispersion properties of evaporated silicon oxide films at very low frequencies. (GB) Dielectric dispersion properties of evaporated silicon oxide films sandwiched between Al electrodes are reported for the frequency range from 0.1 Hz to 20 kHz and the results are analysed by comparing them with the ETSC (electrically excited thermally stimulated current) and the dc current-voltage characteristics. It is shown that the total conductance measured by the ac bridge method is constructed of dc and ac conductivities, as expressed by the empirical relation a(to) = an= + o,=(to). Only the ac conductivity is related to the dielectric dispersion properties, which is Debye-like; that is, the imaginary part of the complex dielectric constant deduced from the ac conductivity has a maximum around the relaxation frequency, which is determined from the frequency dependence of the capacitance. The activation energy and the frequency factor of the relaxation frequency are in good agreement with those deduced from the ETSC results. At a frequency moderately higher than the relaxation frequency, the ac conductivity obeys the empirical relation a==oo toO x 66. The frequency range over which the empirical relation holds is about four decades, which is much narrower than the results of Frost and Jonscher (1975). As far as the experimental results are concerned, there are no contradictions in the interpretation that the dc and ac conductances are originated from mutually independent mechanisms. (Japan). Hireshi Adachi et al, J Phys D: Appl Phys, 11 (8), 1978, 1211-1220. 187