First-principles study of the structural, electronic, and optical properties of the clean and O-deficient ZnAl2O4(110) surfaces

Abstract

In this work, the stability, structural, electronic, and optical properties of the ZnAl2O4(110) surface have been investigated by using the first-principles method based on the density functional theory. The obtained results show that the AlO2-terminated surface is more stable than the ZnAlO2-terminated surface under O-rich and Al-poor conditions, while the ZnAlO2 surface termination is the most stable under O-poor and Al-rich conditions. The results of structural relaxation show that, for both surface terminations, the most noticeable change in the interlayer distances occurs in the four outermost layers only. In addition, our results also show that the electronic structure and properties of these two surfaces are very different. The work function of the ZnAlO2-terminated surface was found to be 2 times smaller than that of the AlO2 surface. Moreover, the effect of oxygen vacancies on the properties of the ZnAl2O4(110) polar surfaces was investigated in details. We find that the formation energy of VO in the case of the AlO2-terminated surface is lower than that of the ZnAlO2-terminated surface. Our results show that the formation of oxygen vacancies affects greatly the electronic and optical properties of the ZnAl2O4(110) surface. We found also that, at high temperatures, the O-deficient AlO2-terminated surface is more stable than the clean surface.