On the deactivation of the dopant and electronic structure in reactively sputtered transparent Al-doped ZnO thin films

Abstract report on a possible origin of electrical heterogeneities in 4 at% Al doped ZnO (AZO) reactively sputtered films. It is found through Zn L 3 and Al K edge X-ray absorption near edge structure (XANES) that a fraction of the Al dopant is deactivated by its positioning in octahedral conformation with oxygen. This fraction as well as the conductivity, optical bandgap and c-axis parameter of ZnO wurtzite are all found to depend on the sample position during deposition. The present results suggest the formation of a metastable Al 2 O 3 (ZnO) m homologous phase that degrades the electrical conductivity. Transparent conducting oxides (TCOs) characterized by both high transparency in the visible range and high electrical conductivity are key materials for devices such