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920. Thin polysiloxane films—new insulating material for cryogenic electronics
Classified abstracts 919-930 30 919. Determination of impurity concentration in thin semiconductor films. (Czechoslovakia) A correction for the determination of the carrier concentration bulk value in thin semiconductor films is derived. Calculations and measurements have been made for thin CdSe films with thickness of 250 to 330 nm deposited in vacuum of 10u6 torr. V Snejdar and J Jerhot, Cz& J Phys, A 22 (4), 1972, 339-340 (in Czech). 30 920. Thin polysiloxane films-new insulating material for cryogenic electronics. (USSR) Using the method of polymerization of silicone organic compounds in plasma of glow discharge, thin polysiloxane films with high volume re&tivity and high electric strength-have been prepared. _ B V Tkachuk et al. Dielectrics. Inter-disciol Scient Coil., Nr 2., 1972. 65-68 (in Russian).’ 30 921. Evaporation of GaAs thin films on sapphire substrates. (Czechoslovakia) Evaporation of GaAs thin films on sapphire substrates in ultrahigh vacuum is investigated. Problems of stoichiometry are solved using the three temperature method. Ga is evaporated by an electron gun and As is evaporated from a spiral heated quartz ampoule. A pumping system with 2000 I/s oil diffusion pump and liquid nitrogen trap is used. R Harman and J Urmin, Proc 5th Czech Conf Electron Vacuum Phys, Czech Acud Sci, Brno 1972, I I a-2. 30 922. The conditions for preparation of continuous single crystal Al film. (Czechoslovakia) High-purity aluminium was evaporated in vacuum of 3.5 x IO-’ torr on mica substrates. Single crystal continuous Al films are obtained at a substrate temperature bf 55O”C, with evaporation rate 120 A/s. and eauivalent thickness of 3600 8. The influence of residual gases ‘on the films after their preparation is also studied. V Stary, Proc 5th Czech Conf Electron Vacuum Phys, Czech Acad Sci, Brno 1972, II a-3. 30 923. Voltage controlled negative resistance in M-I-M structures. (Czechoslovakia) The dependence of the forming process and voltage controlled negative resistance on temperature and ambient oxygen pressure was studied on Al-AIZOJ-Au sandwich structures. It is found that owing to upper electrode discontinuity ambient oxygen enters the Al,O, layer easily and can be chemisorbed there. This process influences strongly conductivity of the A1203 layer. I Emmer, Proc 5th Czech Conf Electron Vacuum Phys, Czech Acad Sci, Brno 1972, I a-10. 30 924. Transmission electron microscopy of some semiconductor epitaxial layers. (Czechoslovakia) The vapour phase homoepitaxial growth of silicon and gallium arsenide is studied, for (11 I) orientation of the silicon and GaAs substrates, by means of transmission electron microscopy. Microinhomogeneities have been observed in silicon films. GaAs layers grown on A(lll) faces showed no defects, while the layers grown on B(111) planes showed stacking faults. (Poland) Z Liliental et al, Proc 5th Czech Conf Electron Vacuum Phys, Czech Acud Sci Brno 1972, I1 b-1. 81. EVACUATION
AND SEALING
31 925. Directly-heated plane cathode. (USSR) A new form of directly-heated plane cathode distinguished by a high resistance to change of shape is described. The current-carrying elements are made in the form of plates symmetrically disposed with respect to the centre of the core, their contours forming the turns of a multiple-threaded spiral approaching the core along the tangents. The width of the current-carrying elements diminishes on passing towards the core, their cross sections being equal at the points of intersection. The width and thickness of the core rings and the width and thickness of the current-carrying elements are chosen so that the cross-sectional area of the core ring may be several times smaller
than that of the current-carrying elements. These geometrical conditions interact with the thermal characteristics of the materials in such a way that the whole unit retains its shape on raising it to the highest working temperatures, thus inter alia stabilizing the emission current. G V Kudelin, USSR Patent, No 347,829, appld 4 Jan 1971, publd 28 Aug 1972. 31 926.
Method of cleaning an electrical vacuum apparatus in the course of evacuation. (USSR) A method of cleaning the surfaces of parts inside the envelopes of electrical vacuum devices in the actiual course of evacuation is described. This is achieved by placing the device in a high-frequency field (e.g., 100 MC/S), amplitude- or frequency-modulated so as to produce ultrasonic oscillations of the discharge plasma. The ultrasonic waves help in removing adsorbed atoms and molecules, even from those parts of the internal surfaces not in direct contact with the plasma, i.e., not subjected to electron or ion bombardment. All this may be done while the electrical vacuum device is actually being evacuated, only very simple additional apparatus being required. Yu S Spiridonov, USSR Patent, No 352,335, appld 14 Dee 1970, publd 6 Ott 1972. 31 927. Envelope of an electrical vacuum device. (USSR) The envelope of an electrical vacuum device here proposed differs from conventional models in that it is partly made of glass and partly of sital, the transition between the two materials involving local recrystallization of the glass. As there are then no perceptible seams between the sections, the mechanical strength is greater, the parts may be made accurately coaxial, and gas evolution is reduced. The sital section differs from the glass in having greater heat resistance, hardness, and tensile strength, as well as in dielectric prooerties. The smoothness of the transition prevents rupture under the;mal shock. L E Gurevich and G N Belkina, USSR Patent. No 342.243. > -, aoold rr- 1March 1968, publd 29 June 197i. 31 928. Method of making a barium gas absorber. (USSR) A method of making a barium gas absorber for use in the degassing of electronic instruments is described. Before insertion into the instrument the gas absorber is itself degassed at 450°C for 5 h at lo- 5 mm Hg and allowed to cool in a nitrogen atmosphere, so that its surface is passivated. The original degassing reduces the gas content by a factor of two and the nitrogen treatment prevents its oxidation in the brief interval before insertion in the electronic instrument. As the gas adsorber is now more capable of absorbing residual gases, the removal of these from the electron instrument takes place more efficiently. V A Sorokoumov et al, USSR Patent, No 331m442, appld 1 June 1970, publd I2 April 1972. 31 929. Frontal cathode. (USSR) A cathode with a stepped structure of its working surface, designed to increase current take-off, is described. Emitting elements in the form of, for example, hollow cylinders fit into the steps, their edges lying on an imaginary spherical surface, the axis of symmetry of which passes through the axis of the cathode. This enables the working surface of the cathode to be substantially increased without increasing its diameter, gaining, in effect, the advantages of a hollow cathode. The number and size of the steps are chosen to match the intended cathode size, due allowance being made for the configuration of the electric field around the emitting surface. One such cathode with an effective working surface of 80 cm* gives a current of lOOO1500 A, the heating power being about 200 W. A M Ivlev, USSR Patent, No 355,689, appld 26 Jan 1970, publd 3 Nov 1972. 31 930. Cathode. (USSR) A “quasi-cold” cathode with a high secondary electron emission coefficient and a fairly high thermionic emission, capable of working at 7O&looo”C in uhf instruments, is described. The cathode is made of a platinum alloy containing 0.5-3 wt ‘A magnesium. For a cathode containing l-1.5’% Mg the maximum secondary emission coefficient is 2.6 and the work function 3.6 eV. The work function remains stable for 1000 h at 1200 K. The secondary emission coefficient remains stable for the same time under bombardment with 469
AND SEALING
31 925. Directly-heated plane cathode. (USSR) A new form of directly-heated plane cathode distinguished by a high resistance to change of shape is described. The current-carrying elements are made in the form of plates symmetrically disposed with respect to the centre of the core, their contours forming the turns of a multiple-threaded spiral approaching the core along the tangents. The width of the current-carrying elements diminishes on passing towards the core, their cross sections being equal at the points of intersection. The width and thickness of the core rings and the width and thickness of the current-carrying elements are chosen so that the cross-sectional area of the core ring may be several times smaller
than that of the current-carrying elements. These geometrical conditions interact with the thermal characteristics of the materials in such a way that the whole unit retains its shape on raising it to the highest working temperatures, thus inter alia stabilizing the emission current. G V Kudelin, USSR Patent, No 347,829, appld 4 Jan 1971, publd 28 Aug 1972. 31 926.
Method of cleaning an electrical vacuum apparatus in the course of evacuation. (USSR) A method of cleaning the surfaces of parts inside the envelopes of electrical vacuum devices in the actiual course of evacuation is described. This is achieved by placing the device in a high-frequency field (e.g., 100 MC/S), amplitude- or frequency-modulated so as to produce ultrasonic oscillations of the discharge plasma. The ultrasonic waves help in removing adsorbed atoms and molecules, even from those parts of the internal surfaces not in direct contact with the plasma, i.e., not subjected to electron or ion bombardment. All this may be done while the electrical vacuum device is actually being evacuated, only very simple additional apparatus being required. Yu S Spiridonov, USSR Patent, No 352,335, appld 14 Dee 1970, publd 6 Ott 1972. 31 927. Envelope of an electrical vacuum device. (USSR) The envelope of an electrical vacuum device here proposed differs from conventional models in that it is partly made of glass and partly of sital, the transition between the two materials involving local recrystallization of the glass. As there are then no perceptible seams between the sections, the mechanical strength is greater, the parts may be made accurately coaxial, and gas evolution is reduced. The sital section differs from the glass in having greater heat resistance, hardness, and tensile strength, as well as in dielectric prooerties. The smoothness of the transition prevents rupture under the;mal shock. L E Gurevich and G N Belkina, USSR Patent. No 342.243. > -, aoold rr- 1March 1968, publd 29 June 197i. 31 928. Method of making a barium gas absorber. (USSR) A method of making a barium gas absorber for use in the degassing of electronic instruments is described. Before insertion into the instrument the gas absorber is itself degassed at 450°C for 5 h at lo- 5 mm Hg and allowed to cool in a nitrogen atmosphere, so that its surface is passivated. The original degassing reduces the gas content by a factor of two and the nitrogen treatment prevents its oxidation in the brief interval before insertion in the electronic instrument. As the gas adsorber is now more capable of absorbing residual gases, the removal of these from the electron instrument takes place more efficiently. V A Sorokoumov et al, USSR Patent, No 331m442, appld 1 June 1970, publd I2 April 1972. 31 929. Frontal cathode. (USSR) A cathode with a stepped structure of its working surface, designed to increase current take-off, is described. Emitting elements in the form of, for example, hollow cylinders fit into the steps, their edges lying on an imaginary spherical surface, the axis of symmetry of which passes through the axis of the cathode. This enables the working surface of the cathode to be substantially increased without increasing its diameter, gaining, in effect, the advantages of a hollow cathode. The number and size of the steps are chosen to match the intended cathode size, due allowance being made for the configuration of the electric field around the emitting surface. One such cathode with an effective working surface of 80 cm* gives a current of lOOO1500 A, the heating power being about 200 W. A M Ivlev, USSR Patent, No 355,689, appld 26 Jan 1970, publd 3 Nov 1972. 31 930. Cathode. (USSR) A “quasi-cold” cathode with a high secondary electron emission coefficient and a fairly high thermionic emission, capable of working at 7O&looo”C in uhf instruments, is described. The cathode is made of a platinum alloy containing 0.5-3 wt ‘A magnesium. For a cathode containing l-1.5’% Mg the maximum secondary emission coefficient is 2.6 and the work function 3.6 eV. The work function remains stable for 1000 h at 1200 K. The secondary emission coefficient remains stable for the same time under bombardment with 469