材料期刊网

当Cr掺杂ZnO 的摩尔数为0．0313~0．0625的范围内，掺杂体系的最小光学带隙宽度和吸收光谱分布随Cr掺杂浓度的变化出现了两类相反的实验结果.为了解决本问题，采用密度泛函理论(DFT)框架下的广义梯度近似(GGA＋U)平面波超软赝势方法，用PBE 泛函的计算方案来描述电子间的交换关联能，对未掺杂 ZnO 和3种不同浓度Cr掺杂ZnO 超胞模型进行了能带结构、态密度、差分电荷密度、布居值以及吸收光谱的计算.结果表明，当Cr掺杂摩尔数为0．0313~0．0625的范围内，随着Cr掺杂量增加，掺杂体系的晶格常数和体积增大，总能量和形成能减小，结构更稳定，掺杂更容易，最小光学带隙宽度增大，吸收光谱显著蓝移.计算结果与实验结果相一致，并合理解释了存在的问题.这对制备Cr掺杂ZnO 中实现短波长光学器件有一定的理论指导作用.

The studies of absorption spectra of Cr-doped ZnO have presented two contradictory experimental re-sults,which are the red shift and blue shift on the optical bandgap and absorption spectra when the mole frac-tion of Cr increases in a range from 0.0313 to 0.0625.To solve this contradiction,based on the first-principles plane-wave pseudopotential of the spin-polarized density functional theory (DFT),we set up four models for Zn1-xCrxO (x=0,0.0313,0.0417,0.0625)to calculate the band structure,density of state,difference charge density,population and absorption spectra using the method of generalized gradient approximation (GGA+U). The calculation results indicate that with the increase of mole fraction of Cr in a range from 0.0313 to 0.0625, the lattice parameters and the volume of doping systems increases,the total energy decreases,the formation en-ergy decreases,thereby the doping becomes easier,and the doping system becomes more stable.Meanwhile, the optical bandgap of the doping system becomes wider,which suggests that absorption spectra of Cr-doped ZnO systems would have a blue shift.The calculation results are consistent with the experimental data.And the contradiction of blue shift and red shift of Cr-doped ZnO systems has been explained reasonably.These results may contribute to improve the design and the preparation of short wavelength optical devices from Cr-doped ZnO.