Improvement of tin oxide single crystal on an m -plane sapphire substrate by mist chemical vapor deposition

Abstract We successfully improved quality of tin oxide (SnO 2 ) films formed on m -plane sapphire substrates by mist chemical vapor deposition. The crystal quality was characterized mainly by the FWHM of the X-ray diffraction ω -rocking curve. We found that the use of tin acetate [Sn(CH 3 COO) 4 ] solution led to the formation of high-quality SnO 2 film, where FWHM was as narrow as 0.1°. Using tin chloride (SnCl 4 ) solution, electrical and optical properties can be improved because crystal grain size was large. Therefore, on the SnO 2 layer formed with the Sn(CH 3 COO) 4 solution, the second SnO 2 layer was overgrown with the SnCl 4 solution to form a double-layer structure, where FWHM was also 0.1° and carbon impurity was lower than that of the first SnO 2 layer. Furthermore, in case of the second SnO 2 layer, we found that a growth temperature window providing the narrow FWHM of 0.1° was very wide (500 °C–800 °C).