Thermoelectric properties in three-dimensional topological insulator thin films

Abstract

Three-dimensional topological insulators (3D TIs) have the topologically protected conducting surface states. These unusual surface states influence the transport behaviors. We focus on the thermoelectric properties. The 3D TI Bi2Te3, Bi2Se3 and Sb2Te3 are good thermoelectric materials. The relations between TI surface states and thermoelectric properties are central subjects to increase the thermoelectric efficiency. In this thesis, we have studied thermoelectric properties of three-dimensional topological insulator thin films using density-functional theory to investigate the effects of surface states and quantum confinement effects varying the film thickness. First-principles calculations and semi-classical Boltzmann transport method are used to investigate the thermoelectric property of Bi2Te3, Bi2Se3 and Sb2Te3 in a-fewlayer structures. Results of this study have shown that the Seebeck coefficients of n-type and p-type doped films exhibit contrasting behavior upon variation in film thickness and that the thickness dependence of the Seebeck coefficient is associated with the interplay of the quantum confinement effect and the surface states near the Fermi level in 2D structures.