Tuning of Thermoelectric Properties of MoSe2 Thin Films Under Helium Ion Irradiation

Abstract

Transition metal dichalcogenides have attracted renewed interest for use as thermoelectric materials owing to their tunable bandgap, moderate Seebeck coefcient, and low thermal conductivity. However, their thermoelectric parameters such as Seebeck coefcient, electrical conductivity, and thermal conductivity are interdependent, which is a drawback. Therefore, it is necessary to fnd a way to adjust one of these parameters without afecting the other parameters. In this study, we investigated the efect of helium ion irradiation on MoSe2 thin flms with the objective of controlling the Seebeck coefcient and electrical conductivity. At the optimal irradiation dose of 1015 cm−2, we observed multiple enhancements of the power factor resulting from an increase in the electrical conductivity, with slight suppression of the Seebeck coefcient. Raman spectroscopy, X-ray difraction, and transmission electron microscopy analyses revealed that irradiation-induced selenium vacancies played an important role in changing the thermoelectric properties of MoSe2 thin flms. These results suggest that helium ion irradiation is a promising method to signifcantly improve the thermoelectric properties of two-dimensional transition metal dichalcogenides.