过渡金属W、Mn、V、Ti掺杂二维材料MoSi_(2)N_(4)的第一性原理计算

First-principles calculation of two-dimensional MoSi_(2) N_(4) doped with transition metals W,Mn,V and Ti

本文基于密度泛函理论(DFT)的第一性原理计算了W、Mn、V、Ti替位掺杂二维MoSi_(2)N_(4)后的几何结构、电子结构以及光学性质的变化.电子结构分析表明W、Mn、W、Ti替位掺杂二维MoSi_(2)N_(4)后的禁带宽度分别为1.806 e V、1.003 e V、1.218 e V和1.373 e V;四种过渡金属掺杂后MoSi_(2)N_(4)的带隙类型没有发生改变,均为间接带隙半导体;W掺杂后的杂质能级靠近价带顶,费米能级靠近价带顶,为p型半导体,杂质能级为受主能级;Mn掺杂后的杂质能级靠近导带底,费米能级靠近导带底,为n型半导体;V和Ti掺杂后杂质能级位于费米能级附近,为复合中心;光学性质分析表明,在2 e V~4 e V的能量区间内,W掺杂结构的吸收波长为336 nm,体系发生红移;Mn、V和Ti替位掺杂后的吸收波长分别为320 nm、358 nm和338 nm,且掺杂体系均发生蓝移.

The changes in the geometric structure, electrical structure, and optical characteristics of the substitution-doped MoSi_(2) N_(4) crystal with W, Mn, V, and Ti were estimated using the fundamental principles of density functional theory (DFT ). According to the electronic structure study, the prohibited band widths for W, Mn, W, and Ti doped two-dimensional MoSi_(2) N_(4) are 1.806 eV, 1.003 eV, 1.218 eV, and 1.373 eV, respectively. Given that the doping structure is a p-type semiconductor and that the impurity energy level is the dominant energy level, the impurity energy level introduced by W doping is close to the top of the valence band. Since the Fermi energy level and the impurity energy level are both near to the conduction band bottom and the doping structure is an n-type semiconductor, the impurity energy level introduced by Mn doping is also known as the sender energy level. The Fermi energy level, which is a part of the recombination center, is close to the impurity energy levels brought about by V and Ti doping. The optical property analysis shows that in the energy interval of 2 eV~4 eV, the absorption wavelength of the W-doped structure is 336 nm and the system is red-shifted;the absorption wavelengths of the Mn-, V- and Ti-dopend systems are 320 nm, 358 nm and 338 nm, respectively, and they are blue-shifted.