Sputtering Effect on Amorphous Ga–In–Zn–O Thin-Film Surface: Occurrence of Subgap and Metallic States

Abstract

The chemical states of -ion-sputtered amorphous Ga–In–Zn–O (-GIZO) thin films were investigated by high-resolution X-ray photoelectron spectroscopy. The sputtering reduced the Zn and In contents relative to that of Ga and generated a subgap state above the valence band maximum. Further sputtering resulted in metallic states at the In3d and In4d orbitals and at the Fermi energy edge, more so for the lower Zn- and In-content film. Locally generated metallic In is suggested to contribute to the metallic states.