Studies in semiconducting metal oxides in conjunction with silicon for solid state gas sensors. Progress report for April 1, 1977--March 31, 1978

Abstract

ZnO films have been reproducibly grown using chemical deposition and radio-frequency sputtering techniques. These films are polycrystalline or amorphous, but are stable, uniform and lend themselves to material characterization by Auger and x-ray analysis techniques, and electrical measurements. SnO/sub 2/ films have been reproducibly grown by chemical vapor deposition, vacuum deposition and radio-frequency sputtering techniques. These films are also polycrystalline or amorphous, and lend themselves to material characterization and measurements. By vacuum deposition techniques, Si-SnO/sub 2/ heterojunctions have been grown, which exhibit good rectification properties. An original thermodynamic analysis of the growth of SnO/sub 2/ by a chemical vapor deposition technique based on the reaction between SnCl/sub 4/ and H/sub 2/O has been developed and submitted for publication. Pd-SiO/sub 2/-Si Schottky barrier diodes exhibiting excellent rectification properties have been successfully fabricated. A formalism has been established for the analysis of the behavior of these devices in the presence of H/sub 2/, H/sub 2/S and CO. The ZnO films grown by chemical deposition have proven to be sensitive to CO and CH/sub 4/. Sputtered ZnO films are sensitive to O/sub 2/ and H/sub 2/. SnO/sub 2/ films grown by chemical vapor deposition are not very sensitive to gases. Sputtered films, however,more » are very sensitive to H/sub 2/ and H/sub 2/S. The Pd-SiO/sub 2/-Si diodes are extremely sensitive to H/sub 2/, H/sub 2/S and NH/sub 3/, and, under certain conditions, to CO. A microprocessor data processing system has been developed incorporating gas sensors in the presence of a variety of gases and gas mixtures.« less