Structural characterization of SnO2 gas sensing films deposited by spray pyrolysis

The results of SnO2 thin film structure characterization using X-ray diffraction, scanning electron microscopy, and Auger electron spectroscopy are presented in this report. We discuss the influence of film deposition conditions and modes of heat treatment in the range of temperatures (400–900°C) on crystallite size and predominant orientation. It was determined that SnO2 films, deposited by spray pyrolysis, are textured polycrystalline films. The crystallite sizes in the films could be controlled over a range from 9 to 25 nm by varying the film thickness, deposition method, and post-deposition annealing temperature. The structure of these SnO2 films was very stable in an oxygen-containing atmosphere. It was found that crystallite orientation, in addition to crystallite size, plays a major role in determining the gas sensitivity of SnO2 films. Crystallites with crystallographic (110) and (200) planes parallel to substrate are predominant in the films. The relative amounts of crystallites with a (110) and (200) orientation depend on film thickness and deposition mode.