GW electronic structure calculations of cobalt defects in ZnO

Abstract

Recently the point defect responsible for the emission of cobalt in doped zinc oxide (ZnO) samples has been identified [24]. In this work we extend our investigation to other point defects in Co-doped ZnO. We use density-functional theory and GW calculations to obtain the orbital-resolved band structure of cobalt doped ZnO. We show that mainly O-p and Co-d orbitals take part in the process and confirm that an oxygen interstitial nearby a cobalt atom is a likely defect to occur in ion beam Co-doped ZnO samples. We also rule out that other common point defects in ZnO can be responsible for the observed d-d transition. Finally, we suggest that defect complexes involving oxygen interstitials could be used to promote ferromagnetism in cobalt doped ZnO samples.