【作者】 郭宏礼； 赵瑾；

【Author】 Hongli Guo;Jin Zhao;Department of Physics,University of Science and Technology of China;Department of Physics,University of Science and Technology of China,Hefei National Laboratory for Physical Sciences at Microscale;

【机构】 中国科学技术大学物理系； 中国科学技术大学物理系,合肥微尺度国家实验室；

【摘要】 SrTiO3作为光催化分解水较好的材料已被广泛研究,但其3.2eV的宽带隙很大地限制了可见光的吸收。基于"极化灾难"机制的SrTiO3/LaAlO3(001)(STO/LAO)界面,我们设计一种既包含n型又包含p型界面的"三明治"结构SrTiO3/LaAlO3/SrTiO3(001)异质结。由于LAO(001)内部存在的本征电场随层数而增加,我们可以通过改变LAO的厚度来调节两边STO的能带位置。通过这种方法,体系的带隙有了明显变小,从而大大提高了光吸收效率,通过第一性原理计算的结果看到,当LAO厚度到达一定层数后,光吸收范围可移动至可见光甚至红外光。同时,LAO内部的电场将光激发的电子空穴对分离并向相反方向移动,有效地阻止了电子空穴对的复合,使得两边的STO分别成为电子掺杂和空穴掺杂的表面,在空间上分离了水的氧化还原反应。综上所述,我们从理论上证明了np型SrTiO3/LaAlO3/SrTiO3(001)薄膜成为可见光光催化材料的可能性。更多还原

【Abstract】 SrTiO3 is a well studied photocatalyst which could be used for H2O splitting. However, a band gap as big as 3.2 eV does not have advantage to absorb the visible light. Based on the polar catastrophe in SrTiO3/LaAlO3(STO/LAO) heterojunction, we design a sandwich like nanostructure STO/LAO/STO, which includes a n type and a p type interface(n-p type). Because the sandwiched LAO is polarized and generates a build-in electric field, with different LAO layers, the band alignment of the two different STO surfaces could be tuned. By this way, the band gap of the whole system could be reduced significantly. Our study proves for this n-p type STO/LAO/STO, the absorption of visible-light is improved distinctly. Simultaneously, the build-in electric field in LAO drives the electrons and holes into opposite directions and prevents the recombination, generating an electron doped surface and a hole doped surface, which could be used for redox and oxidation of H2O separately.更多还原