Mn高掺杂浓度对ZnO禁带宽度和吸收光谱影响的第一性原理研究

采用密度泛函理论框架下的第一性原理平面波超软赝势方法, 建立了未掺杂与不同浓度的Mn原子取代Zn原子的三种Zn_1-xMn_xO超胞模型, 分别对模型进行了几何结构优化、态密度分布、能带分布和吸收光谱的计算. 结果表明: 电子非自旋极化处理的条件下, Mn掺杂浓度越小, ZnO形成能越小, 掺杂越容易, 晶体结构越稳定; Mn的掺入使得ZnO体系的杂质能带和导带发生简并化, 并且导带底和价带底同时向低能方向移动, 掺杂后的导带比价带下降得少导致禁带宽度变宽, ZnO吸收光谱明显出现蓝移现象, 计算结果和实验结果相一致. 同时, 电子自旋极化处理的条件下, 体系有磁性, 吸收光谱发生红移现象. 计算结果与相关实验结果相符合.

First-principles study on the effect of high Mn doped on the band gap and absorption spectrum of ZnO

According to the density functional theory, using first-principles plane-wave ultrasoft pseudopotential method, we set three different concentration Mn doped ZnO models, and perform the geomertry optimizations for the three modes. The total density of states, the band structures and the optical absorption are also calculated. The results show that in the case of non-spin state, the smaller the doping concentration of Mn is, the smaller the formation energy of ZnO is and the easier the Mn doping is, thus the stabler the crystal struetuer is; the Mn doping leads to the degenerations of the impurity energy band and the conduction band, and also to the optical absorption blue-shift. These calculation results accord with the experimental results. Moreover, the magnetism exists in the system under the situation of spin polarization, the absorption spectrum has a red-shift, which is consistent with the experimental result.