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502. Electronic properties of the Si-SiO2 interface as a function of oxide growth conditions. I. Surface states. (Germany)
Classified abstracts 492-502 24. VALVES
24
492. Vacuum lock valve. (USSR) Construction of a vacuum lock valve is described, in which the axis of transmission opening of 900 mm diameter is vertical. The weight of the valve disc is used to seal a rubber gasket in the valve seat- A small mechanism is used for lifting the disc. The valve is intended for use in combination with an oil diffusion pump. M I Dmitruk and A D Runov, Prib Tekh Eksper, No 2, March-April 1972, 154-156 (in Russian).
III.
Vacuum
30. EVAPORATION
applications AND SPUTTERING
30 493. Influence of sorbed water on optical characteristics of single films and multilayer interference systems. (USSR) Using the direct spectroscopic method of multiple disturbed total inner reflection, the water content in thin films of SiOz, MgF, and ZnS is determined. The films were prepared by evaporation in vacuum at 2 x 10e5 torr on substrates heated to 50-60°C. Resistive evaporators were used for evaporation of MgF, and ZnS and an electron beam evaporator with ring cathode was used for deposition of the SiOt. It is found that after exposure to air with relative humidity of 60 to 70 per cent in the vacuum chamber, all the investigated films are fully saturated with water after several minutes. Changes in the optical properties of single films and multiple interference systems are due to the increase in the refractive index caused by filling of the micropores in the films by water from the atmosphere. A F Perveev et al, Optika Spektroskop, 32 (3), March 1972, 607-612 (in Russian). 30 494. Investigation of early stages of growth of SiO films on tungsten. (USSR) The nucleation and growth of dielectric films of SiO on tungsten are investigated in a field electron emission microscope, as a function of substrate temperature (in the range 720 to 960°K at a constant condensation rate of about 1 x lo-’ monolayer/s). It is found that a critical coverage of two monolayers is necessary for nucleation and film growth to begin. Nuclei are formed on facei with a high density of steps. At 720°K formation of film oroceeds at a high relative oversatur&ion of lo6 and it begins wiih formation of nuclei, which rapidly grow and merge into a continuous film. The minimum size of nucleus, which was clearly visible on field emission patterns, was equal to 50 A. At 840°K together with formation of nuclei on faces with high indices, the condensate possessing high mobility forms a SiO film of cubic structure on the closely packed faces (112) and (001). At 980°K after formation of a critical coverage and formation of film on (112) faces, equilibrium between condensation and reevaporation is observed in the third monolayer. The experiments were performed at residual gas pressure of lo+’ torr. I L Sokolskaya and S A Shakirova, Radiotekh Elektron, 17 (3), March 1972, 592-298 (in Russian). 30 495. Nature of inhomogeneities in amorphous films based on oxides. (USSR) Inhomogeneities in dielectric films based on AlzOs, alumin osilicate and borosilicate glass are investigated by measurement of residual polarization in vacuum at 10M3 torr in the range -170 to 200°C. Al203 films were prepared by electrochemical oxidation, the films of glass were deposited by thermal evaporation in vacuum. It is found that sorbed water considerably influences the density of surface charges on AIZOj and borosilicate glass films. A I Korobov et al, Radiotekh Elektron, 17 (2), Feb 1972, 393-398 (in Russian). 30 4%. Breakdown of dielectric films. (USSR) Electrical breakdown of Laz03 and NdzOJ films, with evaporated aluminium contacts, is investigated. It is found that dielectric films of oxides of rare-earth metals have high electrical strength and they can be successfully used in thin-fllm capacitors. D I Chemobrovkin et al, Radiotekh Elektron, 17 (2), Fe6 1972, 428430 (in Russian).
30 497. Investigation of the thermoelectric quality of bismuth Iihns. (USSR) Results of an experimental investigation of the thermoelectric quality of thin bismuth films, as a function of their thickness, are presented. The bismuth films, 200 to 8400 A thick were prepared by thermal evaporation in vacuum at 10e6 torr on polymer layers at room temperature. V M Abrosimov et al, Rediotekh Elektron, 16 (9), 1971, 1741-1742 (in Russian). 30 498. Preparation of electroluminescent vapourdeposited thin 6lms of ZnS, and some of their properties. (Czechoslovakia) The experimental results obtained in vapour depositing elcctroluminescent thin films of ZnS are presented. The ZnS films were evaporated on glass substrates with Sn02 layers in a quartz tube at pressure of 1 x 10e5 torr. Activator was evaporated on the deposited film and introduced in the film by thermal treatment in vacuum. Top electrodes of evaporated Au or Al were used. High-resistance electroluminescent films with direct and alternating electroluminescence were obtained, one blue with self-activated samples and with a maximum in the vicinity of 4600 A, and another yellow with layers activated with manganese and with a maximum in the vicinity of 5800 A. Measurement of the frequency dependence showed that a pronounced luminance maximum exists at a certain frequency, characteristic for a given combination of ZnS and activator. 0 Vanek, Elektrotech Gas, 23 (4), 1972, 228-241 (in Slovak). 30 499. Temperature oscillation of the coe@cient of thermal expansion in CuS semiconductor Glm. (USSR) Experimental data on thermal expansion in the range 60 to 300°K in CuS film with thickness of 500 A are reported. The sample was prepared by evaporation in vacuum at 10e5 torr of CuS with gradual enrichment with sulphur. The sample was annealed in sulphur at 150°C. It is found that the coefficient of thermal expansion of the film oscillates as a function on temperature. F Yu Aliev et al, Pisrna ZhETF, 15 (l), 1972, 24-26 (in Russian). 30 500. Method of measuring the evaporation rate of materials. (USSR) A method of measuring the evaporation rate of a wide range of materials on evaporation in vacua at high temperatures, without having to weigh the sample repeatedly, is described. The evaporation rate is determined by comparing the rate of change of the total pressure in the vacuum chamber with the effective pumping speed of the same vacuum system at some specific pressure. V P Kosteruk, USSR Patent No 324564, appl24th April 1970, publd 24th March 1972. 30 501. Structure of amorphous GaAs. (USSR) Electron-graphical investigations of short-range-order structure in amorphous GaAs films, evaporated by a focused laser beam on glass substrates kept at 105,130 and 29O”K, have been performed. Composition of vapours during the evaporation process is studied with the aid of a mass spectrometer. Yu G Poltavtsev et al, Kristallografira, 17 (l), 1972, 203-206 (in Russian). 30 502. Electronic properties of the Si-SiO, interface as a function of oxide growth condltlons. I. Surface states. (Germany) The effect of growth and annealing conditions on the surface state distribution at the interface between silicon and thermally grown SiO, is investigated. (111) silicon slices, mechanically and chemically polished, were cleaned and outgassed at 900°C under low9 torr for 2 h and then oxidized at 1240°C for 6 h in oxygen at 100 torr. A well pronounced minimum is observed in the surface states distribution of dry grown MOS samples. Some states are created during oxidation (V-states). These acceptor-like states disappear after oxygen annealing at lower temperatures. Other states (0 states) appear during this last treatment. Their properties are less sharply defined. Their capture cross section is higher than for V-states. Vacuum annealing of the completed sample leads to some reconstruction of the interface. (France) J L Pautrat and J C Ptister, Phys Stat Sol (a), 11 (l), May 1972,287296. 299
24
492. Vacuum lock valve. (USSR) Construction of a vacuum lock valve is described, in which the axis of transmission opening of 900 mm diameter is vertical. The weight of the valve disc is used to seal a rubber gasket in the valve seat- A small mechanism is used for lifting the disc. The valve is intended for use in combination with an oil diffusion pump. M I Dmitruk and A D Runov, Prib Tekh Eksper, No 2, March-April 1972, 154-156 (in Russian).
III.
Vacuum
30. EVAPORATION
applications AND SPUTTERING
30 493. Influence of sorbed water on optical characteristics of single films and multilayer interference systems. (USSR) Using the direct spectroscopic method of multiple disturbed total inner reflection, the water content in thin films of SiOz, MgF, and ZnS is determined. The films were prepared by evaporation in vacuum at 2 x 10e5 torr on substrates heated to 50-60°C. Resistive evaporators were used for evaporation of MgF, and ZnS and an electron beam evaporator with ring cathode was used for deposition of the SiOt. It is found that after exposure to air with relative humidity of 60 to 70 per cent in the vacuum chamber, all the investigated films are fully saturated with water after several minutes. Changes in the optical properties of single films and multiple interference systems are due to the increase in the refractive index caused by filling of the micropores in the films by water from the atmosphere. A F Perveev et al, Optika Spektroskop, 32 (3), March 1972, 607-612 (in Russian). 30 494. Investigation of early stages of growth of SiO films on tungsten. (USSR) The nucleation and growth of dielectric films of SiO on tungsten are investigated in a field electron emission microscope, as a function of substrate temperature (in the range 720 to 960°K at a constant condensation rate of about 1 x lo-’ monolayer/s). It is found that a critical coverage of two monolayers is necessary for nucleation and film growth to begin. Nuclei are formed on facei with a high density of steps. At 720°K formation of film oroceeds at a high relative oversatur&ion of lo6 and it begins wiih formation of nuclei, which rapidly grow and merge into a continuous film. The minimum size of nucleus, which was clearly visible on field emission patterns, was equal to 50 A. At 840°K together with formation of nuclei on faces with high indices, the condensate possessing high mobility forms a SiO film of cubic structure on the closely packed faces (112) and (001). At 980°K after formation of a critical coverage and formation of film on (112) faces, equilibrium between condensation and reevaporation is observed in the third monolayer. The experiments were performed at residual gas pressure of lo+’ torr. I L Sokolskaya and S A Shakirova, Radiotekh Elektron, 17 (3), March 1972, 592-298 (in Russian). 30 495. Nature of inhomogeneities in amorphous films based on oxides. (USSR) Inhomogeneities in dielectric films based on AlzOs, alumin osilicate and borosilicate glass are investigated by measurement of residual polarization in vacuum at 10M3 torr in the range -170 to 200°C. Al203 films were prepared by electrochemical oxidation, the films of glass were deposited by thermal evaporation in vacuum. It is found that sorbed water considerably influences the density of surface charges on AIZOj and borosilicate glass films. A I Korobov et al, Radiotekh Elektron, 17 (2), Feb 1972, 393-398 (in Russian). 30 4%. Breakdown of dielectric films. (USSR) Electrical breakdown of Laz03 and NdzOJ films, with evaporated aluminium contacts, is investigated. It is found that dielectric films of oxides of rare-earth metals have high electrical strength and they can be successfully used in thin-fllm capacitors. D I Chemobrovkin et al, Radiotekh Elektron, 17 (2), Fe6 1972, 428430 (in Russian).
30 497. Investigation of the thermoelectric quality of bismuth Iihns. (USSR) Results of an experimental investigation of the thermoelectric quality of thin bismuth films, as a function of their thickness, are presented. The bismuth films, 200 to 8400 A thick were prepared by thermal evaporation in vacuum at 10e6 torr on polymer layers at room temperature. V M Abrosimov et al, Rediotekh Elektron, 16 (9), 1971, 1741-1742 (in Russian). 30 498. Preparation of electroluminescent vapourdeposited thin 6lms of ZnS, and some of their properties. (Czechoslovakia) The experimental results obtained in vapour depositing elcctroluminescent thin films of ZnS are presented. The ZnS films were evaporated on glass substrates with Sn02 layers in a quartz tube at pressure of 1 x 10e5 torr. Activator was evaporated on the deposited film and introduced in the film by thermal treatment in vacuum. Top electrodes of evaporated Au or Al were used. High-resistance electroluminescent films with direct and alternating electroluminescence were obtained, one blue with self-activated samples and with a maximum in the vicinity of 4600 A, and another yellow with layers activated with manganese and with a maximum in the vicinity of 5800 A. Measurement of the frequency dependence showed that a pronounced luminance maximum exists at a certain frequency, characteristic for a given combination of ZnS and activator. 0 Vanek, Elektrotech Gas, 23 (4), 1972, 228-241 (in Slovak). 30 499. Temperature oscillation of the coe@cient of thermal expansion in CuS semiconductor Glm. (USSR) Experimental data on thermal expansion in the range 60 to 300°K in CuS film with thickness of 500 A are reported. The sample was prepared by evaporation in vacuum at 10e5 torr of CuS with gradual enrichment with sulphur. The sample was annealed in sulphur at 150°C. It is found that the coefficient of thermal expansion of the film oscillates as a function on temperature. F Yu Aliev et al, Pisrna ZhETF, 15 (l), 1972, 24-26 (in Russian). 30 500. Method of measuring the evaporation rate of materials. (USSR) A method of measuring the evaporation rate of a wide range of materials on evaporation in vacua at high temperatures, without having to weigh the sample repeatedly, is described. The evaporation rate is determined by comparing the rate of change of the total pressure in the vacuum chamber with the effective pumping speed of the same vacuum system at some specific pressure. V P Kosteruk, USSR Patent No 324564, appl24th April 1970, publd 24th March 1972. 30 501. Structure of amorphous GaAs. (USSR) Electron-graphical investigations of short-range-order structure in amorphous GaAs films, evaporated by a focused laser beam on glass substrates kept at 105,130 and 29O”K, have been performed. Composition of vapours during the evaporation process is studied with the aid of a mass spectrometer. Yu G Poltavtsev et al, Kristallografira, 17 (l), 1972, 203-206 (in Russian). 30 502. Electronic properties of the Si-SiO, interface as a function of oxide growth condltlons. I. Surface states. (Germany) The effect of growth and annealing conditions on the surface state distribution at the interface between silicon and thermally grown SiO, is investigated. (111) silicon slices, mechanically and chemically polished, were cleaned and outgassed at 900°C under low9 torr for 2 h and then oxidized at 1240°C for 6 h in oxygen at 100 torr. A well pronounced minimum is observed in the surface states distribution of dry grown MOS samples. Some states are created during oxidation (V-states). These acceptor-like states disappear after oxygen annealing at lower temperatures. Other states (0 states) appear during this last treatment. Their properties are less sharply defined. Their capture cross section is higher than for V-states. Vacuum annealing of the completed sample leads to some reconstruction of the interface. (France) J L Pautrat and J C Ptister, Phys Stat Sol (a), 11 (l), May 1972,287296. 299