Effect of Buffer Layer on Improvement of SnO2 Thin Film on Sapphire Substrate Formed by Mist Chemical Vapor Deposition

Tin oxide (SnO 2 ) is an n-type wide band-gap semiconductor with excellent properties such as optical, electrical and chemical properties. In this research, SnO 2 thin films were grown on m-plane sapphire substrates by mist chemical vapor deposition. However, it was difficult to deposit high quality SnO 2 films because of the large lattice mismatch and the large difference in the thermal expansion coefficient between the SnO 2 film and the sapphire substrate. To improve the quality of SnO 2 films, we inserted a SnO 2 buffer layer to solve the lattice mismatch problem between the substrate and the film. We found that the surface morphologies of SnO 2 films with the buffer layers were smoother than the films without the buffer layers. Furthermore, the full width at half maximum (FWHM) of an X-ray $\omega$ -rocking curve for the SnO 2 thin film was reduced obviously. Thus, the crystal quality of SnO 2 films was much improved by introducing the buffer layers between the substrate and the thin films.