Mechanism of Surface Morphology Development of Tin Oxide Transparent Conductive Films

The surface morphology of tin oxide transparent conductive films deposited by chemical vapor deposition was studied. The development of surface crystallites was observed, and the change in the crystalline orientations was evaluated at several stages of film growth. The prismatic and triangular pyramidal-shaped crystallites on the surface were characterized as (200) and (110) oriented, respectively, based on the knowledge of crystal habit appearing on cassiterite mineral crystals and periodic bond chain theory. The prismatic shape consisted of flat {110}, while the triangular pyramidal shape consisted of two {101} and one rough surface, which is brought about by the imperfectness of the kinked {111}. Although these two orientations exist in films from the initial growth stage, switching of the most dominant crystalline orientation from (110) to (200) occurs as the morphology of the film changes from an isolated island to competitive growths.