V高掺杂ZnO最小光学带隙和吸收光谱的第一性原理研究

对于V高掺杂ZnO,当摩尔分数为0.0417—0.0625时,随着掺杂量的增加,吸收光谱出现蓝移减弱和蓝移增强两种不同实验结果均有文献报道.采用密度泛函理论的第一性原理平面波超软赝势方法,构建未掺杂ZnO单胞模型、V高掺杂Zn1-xVxO(x=0.0417,0.0625)两种超胞模型,采用GGA+U方法计算掺杂前后体系的形成能、态密度、分波态密度、磁性和吸收光谱.结果表明,当V的掺杂量(原子含量)为2.083%—3.125%时,随着V掺杂量增加,掺杂体系磁矩增大,磁性增强,并且掺杂体系体积增加,总能量下降,形成能减小,掺杂体系更稳定,同时,掺杂ZnO体系的最小光学带隙增宽,吸收带边向低能级方向移动.上述计算结果与实验结果一致.

First principles study of the effect of high V doping on the optical band gap and absorption spectrum of ZnO

Nowadays, the studies on optical band gap and absorption spectrum of V doped ZnO have presented two distinctly different experimental results, that is, the blue shift increases and decreases when the mole fraction of impurity increases in a range from 0.0417 to 0.0625. To solve this contradiction, according to the first-principles plane-wave ultrasoft pseudopotential of the density functional theory, we set up models for a pure ZnO cell and two supercells of Zn_1-xV_xO (x=0.0417, 0.0625) to calculate the total density of state, partial density of state, magnetism and absorption spectrum through using the method of GGA+U. The calculation results indicate that with the doping amount increasing from 2.083 at% to 3.125 at%, the magnetic moment of doping system increases and magnetism augments, too. Moreover, the volume of doping system increases, the total energy decreases and the formation energy becomes lower, thereby making the system more stable. Meanwhile, its optical band gap becomes wider, and the absorption spectrum shifts toward low energy. The calculation results are consistent with the experimental data.
Keywords： V heavy doping ZnO optical band gap absorption spectrum first-principles