ELECTRICAL-PROPERTIES AND GAS-SENSING BEHAVIOR OF SNO2 FILMS PREPARED BY CHEMICAL VAPOR-DEPOSITION

Abstract

Tin oxide films were prepared in the temperature range of 300-700-degrees-C by chemical vapor deposition using a chloride source, SnCl4. The films were analyzed using transmission electron microscopy, Auger electron spectroscopy, and Hall measurement. As the deposition temperature increased from 300 to 500-degrees-C, the resistivity of the film decreased gradually down to approximately 3 x 10(-3)-OMEGA-cm at 500-degrees-C. However, a further increase of the deposition temperature up to 700-degrees-C resulted in a rapid increase in film resistivity. The temperature dependence of the film resistivity is likely more affected by carrier concentration rather than by carrier mobility. Thus, it is suggested that donor electrons are produced primarily by chlorine incorporation into the lattice during the deposition process and that the high resistivity of the film deposited at 700-degrees-C is caused by the lower Cl content, which is due to an easy decomposition of the Sn-Cl bond at high temperatures. The sensitivity of SnO2 thin film to reducing gases, such as H-2 and LPG, were also studied with respect to film thickness and film resistivity.