Texture control of fluorine-doped tin oxide thin film

Abstract

The texture control of transparent oxide thin film, the crystalline orientation, is very important, because it is related to the electrical resistivity and the optical transparency. It is known that the crystal orientation could be controlled by varying precursor source, gas flow rate, and deposition temperature. We deposited fluorine-doped tin oxide (FTO) thin film on aluminoborosilicate glass by spraying water-based solution and ethyl alcohol-added solution. We showed in this research that (200) and (301) preferential orientation of FTO thin film can be controlled by the addition of ethyl alcohol to FTO coating solution. (200) oriented FTO thin film deposited from ethyl alcohol-added solution comprises of pyramidal crystallites with {111} polar faces, which contain {101} contact twin planes. {101} contact twin planes forms salient reentrant angle which provides nucleating sites and makes crystallites grow abnormally. (301) orientation is thought through Periodic Bond Chains of tin hydroxide which forms prismatic long crystallites. Prismatic crystallites are comprised of {110} crystal faces which contain {101} repeated contact twin. It is very helpful to control (200) or (301) oriented crystal formation in transparent conducting oxide film, because the texture affects the electrical and optical properties of transparent conducting oxide film. We suggest that ethyl alcohol addition plays a role to form crystallites with {111} polar faces corresponding to (200) preferential orientation. The crystal morphologies are changed by doping elements, precursor sources, deposition conditions like flow rate and temperatures, and solvents.