少层Bi_2Se_3拓扑绝缘体薄膜电子结构和光学性质理论研究  

Theoretical study on electronic structure and optical property of few-layer topological insulator Bi_2Se_3 thin film

作　　者：李中军[1] 王安健 赵伟 王健越 陈实[1] 李国祥[1] 仇怀利[1] LI Zhongjun;WANG Anjian;ZHAO Wei;WANG Jianyue;CHEN Shi;LI Guoxiang;QIU Huaili(School of Electronic Science and Applied Physics,Hefei University of Technology,Hefei 230009,China)

机构地区：[1]合肥工业大学电子科学与应用物理学院,安徽合肥230009

出　　处：《合肥工业大学学报（自然科学版）》2018年第9期1280-1283,共4页Journal of Hefei University of Technology：Natural Science

基　　金：国家自然科学基金资助项目(21503061);中央高校基本科研业务费专项资金资助项目(JZ2015HGXJ0184;JZ2016HGBZ1046);安徽省自然科学基金资助项目(1708085ME122);国家大学生创新实验资助项目(201510359035)

摘　　要：文章采用密度泛函理论方法,研究少层Bi_2Se_3拓扑绝缘体薄膜的电子结构和光学性质随薄膜厚度的变化。能带结构和态密度分析发现,当薄膜厚度从5QL(quintuple layer)逐步变化到1QL时,其费米能级附近的电子态仍然保持线性色散关系;特别是当薄膜厚度减小到2QL和1QL时,由于量子限域效应,体电子态和表面电子态的能隙都明显增大,导致体电子态和表面电子态发生分离,这种分离有利于制备基于1QL和2QL的Bi_2Se_3拓扑绝缘体薄膜的自旋电子器件。光吸收系数的计算发现,厚度为5QL、4QL、3QL的薄膜在红外区有1个吸收主峰,吸收边远超出了红外区;当厚度减小到2QL和1QL时,吸收边发生明显蓝移,红外区的吸收峰蓝移且强度明显减小,这表明3QL以上的Bi_2Se_3拓扑绝缘体薄膜更适合制备红外光探测器件。The variation of the electronic structure and optical property of few-layer topological insulator Bi 2Se 3 thin film with the thickness of thin film is studied by density functional theory method.The analysis of band structures and density of states indicates that when the thickness of thin film gradually decreases from 5QL(quintuple layer)to 1QL,the electronic states near the Fermi level remain linear dependence of energy on momentum.Moreover,as the thickness of thin film decreases to 2QL and 1QL,the energy gaps of both bulk electronic states and topological surface states obviously increase due to quantum confinement effect,resulting in the separation of topological surface states from bulk states.This separation is convenient to produce spintronic device based on Bi 2Se 3 thin film with the thickness of 2QL and 1QL.The calculated absorption coefficients show that when the thickness of thin film is 5QL,4QL or 3QL,there is an absorption peak in infrared range and the absorption edge is beyond infrared range.However,when the thickness of thin film is reduced to 2QL and 1QL,there is an obvious blue-shift for the absorption edge and the absorption peak in infrared range weakens clearly.This suggests that the Bi 2Se 3 thin film with the thickness more than 2QL is fit to fabricate infrared optoelectronic device.

关 键 词：拓扑绝缘体 少层Bi 2Se 3薄膜 拓扑表面态 量子限域效应 光吸收谱 

分 类 号：O484.1[理学—固体物理]