不同浓度Nb掺杂ZnO第一性原理研究

First-Principles Study on Nb Doped ZnO with Different Concentration

本文采用基于密度泛函理论的第一性原理计算了不同浓度Nb掺杂ZnO的能带结构及性能,并对本征ZnO、Al掺杂ZnO(AZO)和Nb掺杂ZnO(NZO)的模拟结果进行对比分析。结果表明:(1)NZO和AZO的带隙值均低于本征ZnO的带隙值,掺杂浓度(原子数分数)同为6.25%的NZO的带隙值低于AZO的带隙值。随着Nb掺杂浓度增高,NZO的导带底明显降低,态密度峰值降低,且Nb-4d态电子占据了费米能级的主要量子态。(2)随着掺杂浓度的增加,NZO和AZO吸收峰和介电函数峰均降低,且向低能区移动,其中,NZO吸收峰向低能区移动更明显,且介电函数虚部分别在0.42 eV和34.29 eV出现新的峰,主要是价带中Nb-4d和Nb-5p电子能级跃迁所致。掺杂浓度同为6.25%的NZO的静介电常数大于AZO的静介电常数,表明NZO极化能力更强,NZO可以更有效改善ZnO的光电性能。随着Nb掺杂浓度增加,NZO的吸收系数和介电函数虚部强度增加且向高能区移动。NZO的模拟结果为高价态元素Nb掺杂ZnO的实验研究工作及实际应用提供了理论参考。

In this paper,the energy band structure and properties of Nb doped ZnO with different concentration were calculated based on the first-principle of density functional theory,and the simulation results of intrinsic ZnO,Al doped ZnO(AZO)and Nb doped ZnO(NZO)were compared and analyzed.The results show that:(1)the band gap values of NZO and AZO are lower than that of intrinsic ZnO,and the band gap values of NZO with the same concentration of 6.25%are lower than that of AZO.With the increase of Nb doping concentration,the conduction band bottom and the peak density of states of NZO decrease obviously,and Nb-4d electrons occupy the main quantum states of Fermi level.(2)With the increase of doping concentration,the absorption peaks and dielectric function peaks of NZO and AZO decrease,and move to the low energy region.Among them,the absorption peaks of NZO move more obviously to the low energy region,and the imaginary part of dielectric function has new peaks at 0.42 eV and 34.29 eV respectively,which is mainly due to the transition of Nb-4d and Nb-5p electronic energy levels in the valence band.The static dielectric constant of NZO with the same concentration of 6.25%is greater than that of AZO,which indicates that NZO has stronger polarization ability,and NZO can improve the photoelectric properties of ZnO more effectively.With the increase of Nb doping concentration,the absorption coefficient and the imaginary part strength of dielectric function of NZO increase and move to the high energy region.The theoretical simulation results of NZO provide a theoretical reference for the experimental research and practical application of high valence element Nb doped ZnO.