On the Wavy Behaviour of Grain Growth in Sprayed Thin Films

Tin oxide films were prepared by spray pyrolysis technique with different deposition times (60 - 240 s) while the substrate temperature (773 K), the deposition rate (0.22 ml/s) and the concentration (0.2 M) of tin chloride (hydrous) solution were kept constant. Variation of grain size with film thickness (deposition time) is found useful to model a mechanism for film growth. Depending on the mode of layer growth followed by 3D crystallite growth (Stranski and Krastaniv, SK) as well as on the variation of the standard deviation of pole densities, a proposed model of growth mechanism of thin film was suggested. Consider the fact that "what you see depends on how you look", a wavy nature was suggested for the variation of the mean grain size with the film thickness using XRD analysis and SEM/AFM images. The discrepancy between the present result and others was understood on the basis of either the definition of the grain size measured by the different techniques (XRD or SEM) or the proposed wavy behaviour of the grain growth with the film thickness. Interpretation of the results of the grain size variation that extracted from the combined use of XRD and SEM/AFM can provide useful information about the growth mechanism.