Microstructure and Gas Sensing Property of Porous SnO_2 Sputtered Films

摘要

It is often said that the sensitivity of a gas sensor made of an oxide semiconductor film is enhanced by making the film porous. However, the porosity of sensor films has not been sufficiently examined. In this study, SnO_2 films were deposited using DC magnetron sputtering under various substrate temperatures and discharge gas pressures. In addition to the structural analysis by means of X-ray diffraction and scanning electron microscopy, the density and the BET surface area were measured to clarify the film porosity. The sensitivity to H_2 gas of undoped andPd-doped SnO_2 films upon exposure to 1000 ppm H_2 was measured at 300 ℃. SnO_2 films generally showed a columnar structure. The film deposited at a low temperature and a high pressure showed a low density and a large effective surface area. The H_2 sensitivity increased as the density decreased, that is, as the effective surface area increased.