GRAIN-SIZE AND HILLOCK GROWTH OF VACUUM-EVAPORATED SNO2 THIN-FILMS

In this study, tin-oxide (SnO2) thin films were prepared by a two-step process. With a vacuum-evaporation method, pure tin thin films were f irst deposited on Si and glass substrates at substrate temperatures fr om 50 to 300 degrees C. Then the metallic thin films were thermally ox idized with dry oxygen from 300 to 500 degrees C. The surface morpholo gy of the SnO2 thin films was observed by scanning electron microscopy and atomic force microscopy. It was found that metallic hillocks are formed only for SnO2 thin films for which the substrate temperature du ring tin deposition was lower than 150 degrees C. The hillock growth i s associated with stress inhomogeneity during the oxidation process. G rain size of the SnO2 thin films is also found to increase with the fi lm thickness and the oxidation temperature. Kinetics of the grain grow th is discussed in terms of a three-dimensional diffusion limited proc ess. (C) 1996 American Vacuum Society.