SURFACE-MORPHOLOGY AND GAS-SENSING CHARACTERISTICS OF SNO2-X THIN-FILMS OXIDIZED FROM SN FILMS

Abstract

SnO2-x gas sensors have been fabricated by thermal oxidation of Sn thin films. Sn thin films approximately 15000 Angstrom thick for commercial applications are deposited on a polished alumina substrate by using a high-vacuum resistance-heating evaporator. These films are oxidized at 500 degrees C in various oxygen partial pressures in order to control the x value in SnO2-x. The surface morphology and quantitative compositional analysis of SnO2-x thin films as functions of oxygen partial pressures are systematically investigated by SEM, RES and XPS. Gas sensitivities and response times of Pd-doped SnO2-x thin films to H-2, CO, C3H8 and i-C4H10 gases are measured at 300 degrees C. The relationship between gas sensitivities and the x value in SnO2-x thin films is discussed.