ZnO 极性表面及其N原子吸附机理的第一性原理研究

基于密度泛函理论的第一性原理赝势法计算了ZnO极性表面的几何结构和电子结构特性,对比分析了ZnO(0001)和ZnO(0001)表面结构弛豫、能带结构、电子态密度及N吸附ZnO极性表面的形成能情况.计算结果表明: 相对于ZnO(0001)表面,ZnO(0001)表面受结构弛豫影响更加明显,而ZnO(0001)表面完整性更好.相对于体相ZnO结构,ZnO(0001)表面的能带带隙变窄,同时价带顶附近能级非局域性增强使晶体表面的导电性能变得更好;而ZnO(0001)表面的能带带隙变宽,由于O^{-关键词： 密度泛函理论 第一性原理 ZnO极性表面 N吸附}

First-principles calculations of ZnO polar surfaces and N adsorption mechanism

Structural and electronic properties of clean polar ZnO surfaces are studied by using the first-principles ultra-soft pseudo-potential approach to the plane wave, based on the density functional theory. Furthermore, the relaxations, bandstructures, and densities of states for ZnO(0001) and ZnO(000 1 ) surfaces and the N adsorption for ZnO(0001) surface are studied. The calculation results reveal that the relaxation of ZnO(000 1 ) surface is stronger than that of ZnO(0001) surface, so ZnO(0001) surface has a better integrity. Compared with the ZnO bulk, the ZnO(0001) surface has a narrow bandgap, and big conductivity due to the delocalizing characters. However, the bandgap of the ZnO(000 1 ) surface widens, the empty energy levels appear near the top of bandgap due to the existence of O ^{-2p states, and the body electrons transite easily to the surface, under the thermal excitation, and resulting in negative charges.We find that the face-centered site is the stablest adsorption position of ZnO (0001) surface, and the formation energy is lowest in the first layer when N atoms are embeded in the ZnO (0001) surface. Therefore, N atoms easily accumulate on the surface layer rather than occupy the positions in the body.}