Nb高掺杂量对锐钛矿TiO_2导电和光学性能影响

Effects of Nb doping concentration on TiO_2 electricel conductivity and optical performance

目前,在Nb高掺杂量摩尔数分别为0.050和0.0625的条件下,对掺杂体系锐钛矿Ti O2电阻最低存在相反的两种实验结果都有文献报道.为解决这个矛盾,本文采用基于密度泛函理论的平面波超软赝势方法,计算了纯的单胞和三种不同Nb高掺杂量对锐钛矿Ti1-xNbxO2(x=0.03125,0.050,0.0625)超胞的能带结构分布、态密度分布和光学性质.结果表明,在本文限定掺杂量的条件下,Nb掺杂量越增加,掺杂体系的体积越增加,总能量越升高,稳定性越下降,形成能越升高,掺杂越难,相对自由电子浓度越增加,电子有效质量越增加,电子迁移率越减小,电子电导率越减小,最小光学带隙越变宽,吸收光谱和反射率向低能方向移动越显著,透射率越增加.计算结果与实验结果相吻合.

Nowadays, in the reports of Nb heavy-doped TiO2, when the doping mole of Nb is in the range of 0.050 to 0.0625, there is a current controversy between the two experimental results about the minimum resistance of the doped systems. To solve this contradiction, the models of un-doped and the three different concentrations of Nb doped Til-xNbxO2 （x = 0.03125, 0.050, 0.0625） have been set up based on the first-principles plane wave ultra-soft pseudo potential method Of density functional theory; then the geometry optimization of all models is carried out; and the band structures, the density of states, and optical properties are calculated. Results reveal that under the condition of limited doping amount as in this paper, when the doping moles of Nb is increased, the volume, the total energy, and the formation energy of the doped system are increased; the doped system has a lower stability and is hard to be redoped; the relative electronic concentration, and the electron effective mass are increased; the migration rate is reduced, and the conductivity is thus reduced. The wider the optical band-gap, the more obvious the shift of absorption edge to the short wavelength side, the lower the absorptivity and reflectivity; and the transmittance is increased, these are in agreement with the experimental results.