Control of thermoelectric properties in MoSe₂ thin films by using He⁺ irradiation

Defect engineering have been widely used via chemical doping and ion irradiation techniques for modifying electrical and thermal properties. For increasing figure of merit, ZT=α²σT/κ in thermoelectric materials, tuning of electrical and thermal characteristics plays an important role, where α is the Seebeck coefficient, σ is the electrical conductivity, and κ is the thermal conductivity. Here, we present our experimental control of both electrical conductivity and Seebeck coefficient of MoSe₂ thin films by irradiating high-energy He⁺ ion beams. From different doses, we observed enhancement of electrical conductivity despite small decrease of Seebeck coefficient, which results in improvement of thermoelectric performance, i.e. power factor (α²σ), for temperature range of 300K – 420K. To understand the irradiation-induced defects, we discuss complementary experimental analysis, such as X-ray diffraction, transmission electron microscopy and Raman spectroscopy.