Oxygen vacancies in ZnO

TLDR

The electronic properties of ZnO have traditionally been explained by invoking intrinsic defects, particularly oxygen vacancies as the source of unintentional n‑type conductivity. First‑principles calculations reveal that the oxygen vacancy in ZnO is a deep donor with an ε(2+/0) level ~1.0 eV below the conduction band, exhibiting negative‑U behavior due to large lattice relaxations, and the configuration coordinate diagram explains recent ODEPR measurements. Citation: Rev.

Abstract

The electronic properties of ZnO have traditionally been explained by invoking intrinsic defects. In particular, the frequently observed unintentional n-type conductivity has often been attributed to oxygen vacancies. We report first-principles calculations showing that the oxygen vacancy VO is not a shallow donor, but has a deep ε(2+∕0) level at ∼1.0eV below the conduction band. The negative-U behavior that causes the 1+charge state to be unstable is associated with large local lattice relaxations. We present a detailed configuration coordinate diagram, which allows us to provide a detailed interpretation of recently reported ODEPR (optically detected electron paramagnetic resonance) measurements [L. S. Vlasenko and G. D. Watkins, Phys. Rev. B 71, 125210 (2005)].