椭偏法测量拓扑绝缘体的复折射率

Measuring the complex refractive index of topological insulators based on spectroscopic ellipsometry

采用椭偏法测量了拓扑绝缘体Bi 2Te 3单晶的复折射率.运用经典的德鲁德和托克-洛伦兹模型分别对拓扑绝缘体的表面态和体态进行拟合,获得了其折射率和消光系数,并且分析了色散曲线的变化规律.实验结果表明:Bi 2Te 3拓扑绝缘体的体态具有类半导体特性(含带隙),折射率在近红外波段可达7以上;表面态具有类金属特性,厚度约为2.52 nm.

The spectroscopic ellipsometer was used to measure the complex refractive index of topological insulators(e.g.Bi 2Te 3 single crystal).The surface and bulk states of Bi 2Te 3 were fitted with the Drude and the Tauc-Lorentz models.The refractive indices and extinction coefficients of surface and bulk states of Bi 2Te 3 topological insulator were achieved.The properties of the dispersion curves for surface and bulk were analyzed.The results demonstrated that the bulk state possessed semiconductor-like properties with a band gap,whose refractive index could exceed 7 at near-infrared wavelengths.The surface state presented metal-like properties with a thickness of 2.52 nm.