In、Sc掺杂对SrTiO3电子结构和光学性质的影响

采用基于密度泛函理论的第一性原理平面波超软赝势计算方法, 研究了In、Sc p型掺杂对SrTiO3母体化合物稳定性、电子结构和光学性质的影响. 计算结果表明:掺杂后, SrIn0.125Ti0.875O3和SrSc0.125Ti0.875O3的稳定性降低, 体系显示p型简并半导体特征, 掺杂仅引起杂质原子近邻区域的几何结构发生变化. 同时, SrIn0.125Ti0.875O3和SrSc0.125Ti0.875O3体系的光学带隙分别展宽0.35、0.30 eV, 光学吸收边发生蓝移, 在1.25-2.00 eV的能量区间出现新的吸收峰, 该吸收峰与体系Drude型自由载流子的激发相关. 此外, SrIn0.125Ti0.875O3和SrSc0.125Ti0.875O3体系的可见光透过率有了明显的提高, 在350-625 nm波长范围透过率高于85%. 掺杂原子在费米能级处低的电子态密度限制了跃迁概率和光吸收. 大的禁带宽度、小的跃迁概率和弱的光吸收是SrIn0.125Ti0.875O3和SrSc0.125Ti0.875O3体系具有较高光学透明度的原因.

Effect of In and Sc Doping on the Electronic Structure and Optical Properties of SrTiO3

The effect of In and Sc p-type doping on the structural stability, electronic structure, and optical properties of SrTiO3 was investigated by first-principles calculations of plane wave ultra-soft pseudo-potential based on density functional theory (DFT). The calculated results revealed that the structural stability of SrTiO3 was weakened after In and Sc doping and that the partial substitution of In for Ti (or Sc for Ti) merely resulted in local structural changes around the dopant sites. The doped SrIn0.125Ti0.875O3 and SrSc0.125Ti0.875O3 systems are p-type degenerate semiconductors. The optical bandgap was broadened by about 0.35 eV for SrIn0.125Ti0.875O3 and 0.30 eV for SrSc0.125Ti0.875O3. In addition, a noticeable blue-shift of the absorption spectral edge was observed in the two p-type doping systems and a new absorption appeared at around 1.25 to 2.00 eV because of the Drude-type behavior of the free-carrier excitation. The optical transmittance of SrIn0.125Ti0.875O3 and SrSc0.125Ti0.875O3 improved significantly after doping and the transmittances were higher than 85% from 350 to 625 nm. The wide bandgap, small transition probability, and weak absorption because of the low partial density of states of impurities in the Fermi level result in SrIn0.125Ti0.875O3 and SrSc0.125Ti0.875O3 being optically transparent.