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GaAs thin-film evaporation and crystal growth
Abstracts
of the papers presented
at the Thirteenth
National
differences in adsorption energy. There appear to be some correlations between the mode of film growth, the epitaxy of the cesium on the rhenium, and the adsorption energy. Harold F Webster, General Electric Research and Development Center, Schenectady, NY. GaAs thin-film evaporation and crystal growth A technique is described for providing a uniform flow of particles for flash evaporation with special provision for the elimination of projectiles. A simple means for obtaining substrate temperatures in excess of 6M)“C, and a facile method of minimizing outgassing from connecting wires in vacuum are also presented. Epitaxy of GaAs on GaAs and heteroepitaxy on Ge and sapphire is described. Successful epitaxy, based on x-ray Laue patterns, is found to depend on the substrate dislocation density, with substrates containing 4 x lo5 and 4x 10’ dislocations/cm2 yielding single crystal patterns while substrate dislocation densities of i06/cma resulted in rings indicative of polycrystallinity. X-ray diffraction scans shows the polycrystalline films to be very strongly oriented in the (111) direction. Electron microscopy results show the films to be quite smooth, with etching revealing a high degree of disorder at the edge of the tirns and very little disorder in the centre. The results of Hall measurements are also presented. M C Zyetz and A M Despres, Douglas Aircraft Company, Inc, 3000 Ocean Park Blvd, Santa Monica, California. 90406. Epitaxiai gallium arsenide thin films GaAs thin films have been vacuum evaporated on NaCl and quartz substrates using the three temperature technique. Crystal structure of the films are strongly dependent on substrate temperature during deposition. At substrate temperatures below 5OO”C,films deposited on NaCl are poiycrystalline, although preferentially oriented in the same direction as the substrate. At temperatures above 500°C epitaxial films are obtained on NaCI. Features on the diffraction pattern indicating a superlattice structure are sometimes noted. however, above GaAs films deposited on quartz are polycrystalline; 500°C all the crvstallites are arranged with the (111) crvstal olane parallel to the substrate but randomly oriented‘ about ‘the c-axis. Electrical, optical, and crystallographic properties, and the results of doping experiments are presented. R F Steinberg, The Bendix Corporation, Research Laboratories Division, Southfield, Michigan 48075. Epitaxy of thin films of cobalt and titanium Thin films of cobalt and titanium were prepared by evaporation of the metal in an ultrahigh vacuum onto mica and silver single-crystal films, obtained within the same vacuum. The orientation and structure of the films was studied as a function of substrate temperature and film thickness by means of reflection electron diffraction and transmission electron diffraction and microscopy. It was found that epitaxy of cobalt and titanium deposited onto mica could be obtained only at elevated temperatures, whilst that of cobalt on a silver single-crystal film was achieved already near room temperature. A comparative study of films prepared in a conventional high vacuum was aIs. made. E Grhbaum, G Kremer and R Schwarz, Departamento de Fisica, Universidad de Chile, Casilla 5487, Santiago, Chile. Formation of single crystal oxide films by reactive and direct deposition Results are presented on the preparation of single crystal films of aluminium and tantalum oxides on various substrates by reactive (pure metal source) as well as by direct (oxide source) sputtering and evaporation. rf, dc glow and supported discharge sputtering were utilized. The critical conditions for single crystal growth by reactive techniques are shown to be systematically defined by the interdependent parameters growth rate, substrate temperature, and partial oxygen pressure. Also discussed are the effects of substrate potential during reactive deposition. A model, used successfully to describe the epitaxial growth of germanium is applied to oxide films prepared by direct deposition. The model must be modified to account for the reaction kinetics involved in the formation of films in a reactive atmosphere. E Krikorian, General Dynamics, Pomona Division, PO Box 2507, Pomona, California 91766.
Vacuum Symposium
Friction
and lubrication
in vacuum
Au apparatus for the measurement of friction and wear as a function of speed and load in ultrahigh vacuum and controlled atmospheres An apparatus is described for measuring friction and wear in ultrahigh vacuum and in controlled atmospheres down to
of the papers presented
at the Thirteenth
National
differences in adsorption energy. There appear to be some correlations between the mode of film growth, the epitaxy of the cesium on the rhenium, and the adsorption energy. Harold F Webster, General Electric Research and Development Center, Schenectady, NY. GaAs thin-film evaporation and crystal growth A technique is described for providing a uniform flow of particles for flash evaporation with special provision for the elimination of projectiles. A simple means for obtaining substrate temperatures in excess of 6M)“C, and a facile method of minimizing outgassing from connecting wires in vacuum are also presented. Epitaxy of GaAs on GaAs and heteroepitaxy on Ge and sapphire is described. Successful epitaxy, based on x-ray Laue patterns, is found to depend on the substrate dislocation density, with substrates containing 4 x lo5 and 4x 10’ dislocations/cm2 yielding single crystal patterns while substrate dislocation densities of i06/cma resulted in rings indicative of polycrystallinity. X-ray diffraction scans shows the polycrystalline films to be very strongly oriented in the (111) direction. Electron microscopy results show the films to be quite smooth, with etching revealing a high degree of disorder at the edge of the tirns and very little disorder in the centre. The results of Hall measurements are also presented. M C Zyetz and A M Despres, Douglas Aircraft Company, Inc, 3000 Ocean Park Blvd, Santa Monica, California. 90406. Epitaxiai gallium arsenide thin films GaAs thin films have been vacuum evaporated on NaCl and quartz substrates using the three temperature technique. Crystal structure of the films are strongly dependent on substrate temperature during deposition. At substrate temperatures below 5OO”C,films deposited on NaCl are poiycrystalline, although preferentially oriented in the same direction as the substrate. At temperatures above 500°C epitaxial films are obtained on NaCI. Features on the diffraction pattern indicating a superlattice structure are sometimes noted. however, above GaAs films deposited on quartz are polycrystalline; 500°C all the crvstallites are arranged with the (111) crvstal olane parallel to the substrate but randomly oriented‘ about ‘the c-axis. Electrical, optical, and crystallographic properties, and the results of doping experiments are presented. R F Steinberg, The Bendix Corporation, Research Laboratories Division, Southfield, Michigan 48075. Epitaxy of thin films of cobalt and titanium Thin films of cobalt and titanium were prepared by evaporation of the metal in an ultrahigh vacuum onto mica and silver single-crystal films, obtained within the same vacuum. The orientation and structure of the films was studied as a function of substrate temperature and film thickness by means of reflection electron diffraction and transmission electron diffraction and microscopy. It was found that epitaxy of cobalt and titanium deposited onto mica could be obtained only at elevated temperatures, whilst that of cobalt on a silver single-crystal film was achieved already near room temperature. A comparative study of films prepared in a conventional high vacuum was aIs. made. E Grhbaum, G Kremer and R Schwarz, Departamento de Fisica, Universidad de Chile, Casilla 5487, Santiago, Chile. Formation of single crystal oxide films by reactive and direct deposition Results are presented on the preparation of single crystal films of aluminium and tantalum oxides on various substrates by reactive (pure metal source) as well as by direct (oxide source) sputtering and evaporation. rf, dc glow and supported discharge sputtering were utilized. The critical conditions for single crystal growth by reactive techniques are shown to be systematically defined by the interdependent parameters growth rate, substrate temperature, and partial oxygen pressure. Also discussed are the effects of substrate potential during reactive deposition. A model, used successfully to describe the epitaxial growth of germanium is applied to oxide films prepared by direct deposition. The model must be modified to account for the reaction kinetics involved in the formation of films in a reactive atmosphere. E Krikorian, General Dynamics, Pomona Division, PO Box 2507, Pomona, California 91766.
Vacuum Symposium
Friction
and lubrication
in vacuum
Au apparatus for the measurement of friction and wear as a function of speed and load in ultrahigh vacuum and controlled atmospheres An apparatus is described for measuring friction and wear in ultrahigh vacuum and in controlled atmospheres down to