Modification of ZnO surfaces with oxygen vacancies: density functional study

Abstract

ZnO is a complex material, whose properties are very sensitive to preparation conditions due to the presence of various intrinsic defects. Using the modified density functional calculations, we study the relative stability of the nonpolar (1010 and 1120) and the polar (zinc-terminated (0001)-Zn and oxygen-terminated (0001)-O) ZnO surfaces, as well as the influence of oxygen vacancies on their stability and electronic structure. In our study we consider models of surfaces with different positions and concentrations of oxygen vacancies. Particular attention is given to the charge state of the oxygen vacancies and charges of the individual atoms. We find that the 1010 surface is the most stable, while the polar (0001)-Zn surface is the least stable. Our calculations indicate that the configuration with oxygen vacancies at the top of the surface is the most favorable for all studied surfaces. The obtained results for the structural relaxations and energetics are compared with previous theoretical and experimental data.