Hard X-ray photoelectron spectroscopy of transparent conductive heavily doped ZnO thin films

Abstract

Transparent conductive Al-doped ZnO thin films have been investigated by hard X-ray photoelectron spectroscopy using a laboratory-based XPS system equipped with a Cr Kα X-ray source. The dependences of the carrier concentration were studied. The core and valence band spectra showed tail-like satellite structures at high binding energy side strongly depends on the carrier concentration. The in-gap states near the Fermi level showed a broad feature extended below the conduction band minimum estimated by the photoluminescence.