First-principles of wurtzite ZnO (0001) and (0001-bar ) surface structures

The surface structures of wurtzite ZnO (0001) and (0001-bar ) surfaces are investigated by using a first-principles calculation of plane wave ultra-soft pseudo-potential technology based on density functional theory (DFT). The calculated results reveal that the surface energy of ZnO-Zn is bigger than that of ZnO-O, and the ZnO-Zn surface is more unstable and active. These two surfaces are apt to relax inward, but the contractions of the ZnO-Zn surface are smaller than the ZnO-O surface. Due to the dispersed Zn4s states and the states of stronger hybridization between the Zn and O atoms, the ZnO-Zn surface shows n-type conduction, while the O2p dangling-bond bands in the upper part of the valence cause the ZnO-O surface to have p-type conduction. The above results are broadly consistent with the experimental results. (semiconductor physics)