表面钝化对ZnO纳米线压电性的影响

本文利用第一性原理方法，研究了四种表面钝化对六角形001]方向ZnO纳米线压电性质的影响. 研究发现，在50%H/50%Cl和50%H/50%F两种钝化中，体积效应和表面效应都起到了增强压电性的作用. 而在100%H和100%Cl的两种钝化中，表面效应被弱极化的表面电荷屏蔽，不能起到增强压电性的作用. 此外，结果还揭示了体积效应和表面效应的竞争使得实验上不能观察到ZnO纳米线压电性的直径依赖现象，并提出了利用表面钝化缩小纳米线轴向晶格常数或增大表面极化来提高压电性的方法.

Effect of Passivation on Piezoelectricity of ZnO Nanowire

Surface passivation is one valuable approach to tune the properties of nanomaterials. The piezoelectric properties of hexagonal 001] ZnO nanowires with four kinds of surface passivations were investigated using the first-principles calculations. It is found that in the 50% H(O) and 50% Cl(Zn), 50% H(O) and 50% F(Zn) passivations, the volume and surface effects both enhance the piezoelectric coefficient. This differs from the unpassivated cases where the surface effect was the sole source of piezoelectric enhancement. In the 100% H, 100% Cl passivations, the piezoelectric enhancement is not possible since the surface effect is screened by surface charge with weak polarization. The study reveals that the competition between the volume effect and surface effect influences the identification of the diameter-dependence phenomenon of piezoelectric coefficients for ZnO nanowires in experiments. Moreover, the results suggest that one effective means of improving piezoelectricity of ZnO nanowires is shrinking axial lattice or increasing surface polarization through passivation.