第一性原理计算Ti掺杂CrSi_2的光电特性

First principle calculation ofoptical-electrical characteristics of Ti-doped CrSi_2

采用第一性原理方法对Ti掺杂CrSi2的几何结构、电子结构、复介电函数、吸收系数、反射谱、折射率和光电导率进行了计算,对Ti置换Cr原子后的光电特性变化进行了分析.结果表明:Ti置换Cr原子后,晶格常数a,b和c均增大,体积变大;Ti的掺入引入了新的杂质能级,导致费米能级插入价带中,Cr11TiSi24变为p型半导体,带隙宽度由未掺杂时的0.38eV变为0.082eV,价带顶和导带底的态密度主要由Cr-d和Ti-d层电子贡献;与未掺杂CrSi2相比,Cr11TiSi24的介电峰发生了红移,仅在1.33eV处有一个峰,而原位于4.53eV处的峰消失;吸收系数,反射率和光电导率明显降低.

A detailed theoretical study on geometric structure, electronic structure, complex dielectric function of Ti-doped CrSi2 was performed based on the first -principles method. The results show that after doping Ti, the lattice constants a, b, c and volume are all increased. New impurity energy levels are induced in the forbidden band, and the Fermi energy moved into valence band. Cr11 TiSi24 is a p-type semiconductor and the band gap decreased from 0.38 eV to 0. 082 eV. Density of states of the valence band top and conduction band bottom are mainly composed of Cr-d and Ti-d. Compared with pure CrSi2, the dielectric peak of Cr11 TiSi24makes red shift and only a peak appears at 1.33 eV, while the peak at 4. 53 eV is disappeared. Absorption, reflectivity and conductivity of Cr11TiSi24 are obviously decreased.