过渡金属与碳共掺ZnO磁光学性质的第一性原理研究

Interesting Magnetic and Optical Properties of ZnO Co-doped with Transition Metal and Carbon

采用密度泛函理论第一性原理超软赝势的方法，计算了过渡金属与C共掺杂ZnO的磁学和光学性质．计算结果表明，共掺杂均导致费米能级发生移动，掺杂体系共价性强弱发生变化，且共掺杂更有利于高居里温度铁磁性半导体的实现；为了进一步分析掺杂体系的磁学性质，研究了其铁磁态与反铁磁态的能量差、空间电荷和自旋密度分布．各种类型掺杂体系在高能区的光学性质与纯净ZnO几乎一致，而在低能区却存在较大差异，结合电子结构定性解释了光学性质的变化．

Magnetic and optical properties of ZnO co-doped with transition metal and carbon have been investigated using density functional theory based on first-principles ultrasoft pseudopoten- tial method. Upon co-doping with transition metal （TM） and carbon, the calculated results show a shift in the Fermi level and a remarkable change in the covalency of ZnO. Such cases energetically favor ferromagnetic semiconductor with high Curie temperature due to p-d exchange interaction between TM ions and holes induced by C doping. The total en- ergy difference between the ferromagnetic and the antiferromagnetic configurations, spatial charge and spin density, which determine the magnetic ordering, were calculated in co-doped systems for further analysis of magnetic properties. It was also discovered that optical prop- erties in the higher energy region remain relatively unchanged while those at the low energy region are changed after the co-doping. These changes of optical properties are qualitatively explained based on the calculated electronic structure. The validity of our calculation in comparison with other theoretical predictions will further motivate the experimental inves- tigation of （TM, C） co-doped ZnO diluted magnetic semiconductors.