Microstructural characteristics of tin oxide-based thin films on (0001) Al₂O₃ substrates: Effects of substrate temperature and RF power during co-sputtering

While tin oxides such as SnO and SnO₂ are widely used in various applications, surprisingly, only a limited number of reports have been presented on the microstructural characteristics of tin oxide thin films grown under various growth conditions. In this paper, the effects of the substrate temperature and content of foreign Zn ion on the microstructural characteristics of tin oxide thin films grown by radio-frequency magnetron sputtering were investigated. The increase in substrate temperature induced change in the stoichiometry of the thin films from SnO_1+x to SnO_2x. Additionally, the phase contrast in the transmission electron microscopy image revealed that SnO_1+x and SnO_2x phases were alternating in thin films and the width of each phase became narrower at high substrate temperature. The ternary zinc tin oxide thin films were deposited using the co-sputtering method. As the ZnO target power increased, the crystallinity of the thin films became poly-crystalline, and then showed improved crystallinity again with two types of phases.