Investigation of substrate-dependent characteristics of SnO2 thin films with Hall effect, X-ray diffraction, X-ray photoelectron spectroscopy and atomic force microscopy measurements

SnO2 thin films of 100 nm in thickness were prepared on glass and alumina substrates with targets-facing type sputtering apparatus to investigate the substrate-dependent characteristics of the films. The sensitivity of the films is measured in flammable gas atmosphere (hydrogen, butane and methane, 5000 ppm), and it revealed that the SnO2 films on alumina substrates showed better sensitivity for all introduced gases than the films on glass substrates. Hall effect, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) measurements were performed to clarify the difference of the sensitivity, and it is concluded as follows: 1) The variation of carrier concentration of the films on alumina substrates is larger than those on glass substrates when they are exposed to flammable eases. 2) The structure of the films on alumina substrates is similar to that of SnO2 powder. 3) The film on an alumina substrate contains more oxygen impurities than that on a glass substrate, which can be considered to cause the large variation of carrier concentration. 4) Surface area of the films on alumina substrates is wider than that of the films on glass substrates.