表面效应对Li掺杂的ZnO薄膜材料p型电导的影响

The surface effect on the p-type conductivity of Li-doped ZnO film

利用第一性原理的方法研究了在ZnO非极性表面和极性表面的不同原子层中,分别用Li原子去替位Zn原予(记为Li_(zn))后的相对稳定性和热离化能.计算结果表明Li_(zn)处于ZnO表面区域时的稳定性优于在ZnO体中时的稳定性,并且Li_(zn)在表面区域的热离化能要比它在体结构中的热离化能大很多,于是,ZnO表面效应的存在会使Li掺杂的ZnO薄膜材料的p型导电能力大幅度降低.这个结果对低维ZnO体系p型掺杂有着重要的指导意义.我们进一步发现,在不同的ZnO表面区域里Li_(zn)的热离化能会表现出很大的差异是源于不同的表面具有不同的静电势分布.

＋By using the first-principles method,we study the relative stabilities and the thermal ionization energies of the doped Li（LiZn） in the different atomic layers for both the non-polar and polar surfaces.Our calculations indicate that the LiZn in the surface region is more stable than in the ZnO bulk,and the thermal ionization energy of the LiZn in the surface region is considerably bigger than in the ZnO bulk.So,the surface of ZnO film degrades the p-type conductivity of the Li-doped film significantly,which is important for the p-type doping in the low-dimensional ZnO system.Furthermore,we find that the observed difference in thermal ionization energy of LiZn between a surface and bulk actually stems from the different distributions of the electrostatic potentials between a surface and bulk.