Modification of electronic structure and thermoelectric properties of hole-doped tungsten dichalcogenides

TL;DR

This study investigates how doping and substitution alter the electronic structure and thermoelectric properties of layered WSe_2, revealing changes in band structure, thermal conductivity, and thermoelectric efficiency at high temperatures.

Contribution

It combines theoretical calculations and experimental measurements to show how Te substitution modifies the electronic states and thermoelectric performance of hole-doped WSe_2.

Findings

Te substitution raises bands at the K point in WSe_2

W_1-xTa_xSe_1.6Te_0.4 has lower room-temperature thermal conductivity

Both systems have similar thermoelectric figures of merit at high temperatures

Abstract

We present a study on the modification of the electronic structure and hole-doping effect for the layered dichalcogenide WSe_2 with a multi-valley band structure, where Ta is doped on the W site along with a partial substitution of Te for its lighter counterpart Se. By means of band-structure calculations and specific-heat measurements, the introduction of Te is theoretically and experimentally found to change the electronic states in WSe_2. While in WSe_2 the valence-band maximum is located at the Gamma point, the introduction of Te raises the bands at the K point with respect to the Gamma point. In addition, thermal-transport measurements reveal a smaller thermal conductivity at room temperature of W_1-xTa_xSe_1.6Te_0.4 than reported for W_1-xTa_xSe_2. However, when approaching 900 K, the thermal conductivities of both systems converge while the resistivity in W_1-xTa_xSe_1.6Te_0.4 is larger than in W_1-xTa_xSe_2, leading to comparable but slightly smaller values of the figure of merit in W_1-xTa_xSe_1.6Te_0.4.