Tin dioxide (SnO2) with rutile type structure exhibits unique electronic and optical properties. In applications of this material as gas sensors, a film-type of SnO2 provides high ratio of surface area to volume and lead to high sensitivity and fast responses. It has been found that substrate material, deposition conditions, and annealing procedure may directly control the microstructure of thin films, hence control gas-sensing properties. In this paper, we present transmission electron microscopy (TEM) studies of the microstructure and crystal defects of tin oxide thin films on sapphire substrate with subsequent annealing at high temperatures.

Tin oxide thin films were deposited on the surface of sapphire by e-beam evaporation of high purity SnO2 (99.999%) at 350°C followed by annealing in air at 600°C - 700°C. Microstructures of the films were characterized by X-ray diffraction (XRD) and TEM techniques.