Mn-N共掺杂TiO_2电子结构和光学性质的第一性原理计算

First-principles calculation on the electronic structure and photoelectric properties of Mn-N co-doped TiO_2

本文采用第一性原理研究了Mn、N掺杂TiO_2和Mn-N共掺杂TiO_2的能带结构、态密度和Mn-N共掺TiO_2对体系介电函数与吸收谱的影响.研究结果表明,Mn掺杂TiO_2的能带结构的禁带内出现的杂质能级是由Mn的3d轨道贡献;N掺杂TiO_2在费米能级处的杂质能级则由O 2p,Ti 3d和N 2p轨道杂化形成;Mn-N共掺的TiO_2能带在费米能级处的杂质能级则由O 2p,Ti和Mn的3d以及N 2p轨道杂化形成;对于介电函数,在低能区间(<2.5 e V),理想TiO_2无介电峰,Mn-N共掺体系则出现了两个介电峰,原因在于Mn 3d态和N 2p态使介电峰值向低能区移动;同时,与理想TiO_2的吸收谱相比,最大的变化是在可见光区出现了一个吸收峰,且在可见光区的响应的范围变宽.

The first -principles methods are used to study the band structures and the densities of states of the Mn doped TiO2 and N doped TiO2 and Mn - N co - doped TiO2. In addition, the dielectric functions and absorp- tion spectra of the Mn - N co - doped TiO2were also studied. It is shown that the impurity levels in forbidden en- ergy of Mn doped TiO2 were contributed by the Mn 3d; at the fermi level, the impurity level of N doped TiO2 is composed of O 2p, Ti 3d and N 2p orbital hybrid ; the impurity levels of the Mn - N co - doped TiO2 were con- tributed by the O 2p, Ti 3d, Mn 3d and N 2p at the fermi level. For the dielectric function, the pure TiO2 with- out the dielectric peak and the Mn -N co -doped TiO2 system have two dielectric peaks in the low energy range （ 〈2.5 eV）, it is reason that the dielectric peaks shifts to lower energy region by Mn 3d and N 2p states. At the same time, the Mn - N co - doped TiO2 system have an absorption peaks in the visible region compared with the pure TiO2, and the response turn width in the range of visible light.