轻稀土掺杂TiO2(101)面的电子结构和光学性质的理论研究

Theoretical study on electronic structures and optical properties of light rare earth doped TiO2(101) surface

利用基于密度泛函理论的第一性原理方法研究了轻稀土掺杂TiO2(101)面的电子结构和光学性质,并讨论了其内部的微观机制.研究结果表明:稀土掺杂TiO2(101)面时,掺杂原子诱导掺杂体系的价带顶和导带底出现了显著的不对称,掺杂体系形成了兼并型的P型或N型半导体.掺杂体系的价带和导带出现了明显的移动,平均带隙相比未掺杂体系均出现了不同程度的增加,但是在带隙中出现了浅杂质能级.稀土原子替代O原子或以插入原子形成掺杂体系的光吸收强度明显高于稀土原子替代Ti原子形成的掺杂体系.La@O13体系和Ce@O13体系的光吸收能力最强,其可以归因于净磁矩的产生和浅杂质能级的形成,从而致使电子空穴对的产生和分离,进一步提高了掺杂体系在可见光区域的光催化吸收强度.研究结果可为二氧化钛在光电子器件领域的应用开发提供有益的理论依据.

In this paper, the electronic structures and optical properties of light rare earth doped TiO2(101)surface are studied by first-principles method based on density functional theory. Simultaneously, the internal microscopic mechanisms are discussed. The results show that when the rare earth atoms are doped in TiO2(101)surface, the valence band maximum and conduction band minimum of doped systems induced by the doped atoms show a significant asymmetry, and the doped systems form some annexed P-type semiconductor or N-type semiconductor. Compared with the undoped system, the average band gaps of doped systems increase in different degrees, but some shallow impurity levels appeared in the band gap. The light absorption intensities of the doped systems that are formed by substituting rare earth atom for O atom or forming inserted atom are significantly higher than that of the doped systems formed by substituting rare earth atom for Ti atom. Among all the doped systems, the La@O13 system and Ce@O13 system have the strongest light absorption ability, which can be attributed to the generation of net magnetic moment and the formation of shallow impurity energy levels.Therefore, the generation and separation of electron hole pairs further improve the light absorption intensities of the doped systems in the visible region. These outcomes can provide a theoretical basis for the application and development of titanium dioxide in the field of optoelectronic devices.