Programme

P.14 -- Poster, NCTP-43

Date: Tuesday, 31 July 2018

Time: 08:30 - 10:00

Band engineering of Bi2Te3 under geometry optimization and strains

Tran Van Quang*(1), Nguyễn Bích Ngọc(2)

(1) Department of Physics, University of Transport and Communications, Hanoi, Vietnam (2) Graduate University of Science and Technology, Vietnam Academy of Science and Technology

Bi2Te3 is a well-known state-of-the-art thermoelectric (TE) material operating at around room temperature. Effort to investigate new effects to improve its TE performance is of great interest. In this report, we employ first-principles density-functional-theory calculation to examine the band structure of Bi2Te3. Spin-orbital coupling also has to be take into account for the precise description. We found that the geometry optimization and atomic relaxation play an important role to determine the band structure, especially the band structure around Fermi energy. Moreover, the valence band edges significantly changes due to the effect of volume relaxation. The band topology is gradually distorted sensitively due to strain. Degenerate valleys at the band edges manifest a possible enhancement of the power factor by band engineering. This is also responsible for the change of TE transport coefficients due to pressure which is observed recently. We also show the calculation of the transport coefficients, i.e. the Seebeck coefficient, the electrical conductivity, and the power factor using the solution of semi-classical Boltzmann’s equation in a constant relaxation-time approximation.

Presenter: Tran Van Quang