Effect of the substrate temperature on the electrical and structural properties of spray-deposited SnO2:F thin films

SnO2:F thin films were prepared by the spray pyrolysis (SP) technique at substrate temperature in the range 360-480 degrees C. The effect of varying the substrate temperature on the electrical and structural properties of the films was investigated by studying the I-V characteristics, the X-ray diffraction patterns (XRD), and the scanning electron microscope images (SEM). The I-V characteristics of the films were improved by increasing the substrate temperature, i.e. the resistivity of the films had decreased from 98 to 0.22 Omega cm. The X-ray diffraction patterns taken at 400 and 480 degrees C showed that the films are polycrystalline and two directions of crystal growth appeared in the difractogram of the film deposited at the lower substrate temperature, which correspond to the reflections from the (110) and (200) planes. With the increase in the substrate temperature a new direction of crystal growth appeared, which corresponds to the reflection from the (101) plane. Also the (110) and (200) lines were slightly grown at the higher substrate temperature, which means the crystal growth was enhanced and the grain size had increased. The SEM images confirmed these results and showed larger grains and more crystallization for the higher substrate temperature too. (C) 2009 Elsevier Ltd. All rights reserved.