First-Principles Study of the Surface of Wurtzite ZnO and ZnS - Implications for Nanostructure Formation

The microscopic properties of several ZnO and ZnS surfaces of low Miller index are investigated through first-principles calculation of the surface energy, crystal structure and electronic structure. Generally, the non-polar surfaces such as (10 (1) over bar0) and (11 (2) over bar0) are found to be more stable than the polar (0001)-Zn surface. The (11 (2) over bar0) surface is found to be the most stable for both ZnO and ZnS semiconductors and the (10 (1) over bar0) surface is found to have a slightly larger surface energy. These are consistent with the abundant observations of ZnO nanostructures having (11 (2) over bar0) and (10 (1) over bar0) surfaces. The near-surface structures and electronic structures are discussed.