Effects of Oxygen Addition on the Local Structures of Cosputtered Transparent Conducting Oxide Films

The local structures of amorphous transparent conducting oxide films (ZnO, GaO, GaZnO, InZnO, InGaO, and InGaZnO) prepared by rf magnetron sputtering were examined with hard X-ray absorption spectroscopy. The introduction of oxygen gas during sputtering enhanced the crystallinity of Zn-containing cosputtered films (GaZnO, InZnO, and InGaZnO) and degraded the homogeneity of the cosputtered InGaZnO films by segregating ZnO. This suggests that the cosputtering method using oxygen gas is unsuitable for the growth of Zn-containing tertiary or quaternary amorphous oxide films because of the crystallization and phase changes driven by oxygen bombardment effects.