Substrate dependent thermal conductivity in Td-WTe2 using micro-Raman spectroscopy

Tungsten ditelluride (WTe2) is a member of the transition metal telluride (TMT) family, which is emerging as a promising material for electronic applications. The study of thermal characteristics of WTe2 is important to understand heat dissipation in electronic devices. As heat dissipation and thermal transport are dependent on the choice of substrates, it is imperative to understand the effect of different substrates on the thermal conductivity of WTe2. Moreover, the comprehension of out-of-plane thermal conductivity is important when dealing with heat management of multiple layers of 2D materials and their heterostructures. In this work, we report the thermal conductivity of few-layer thick exfoliated Td phase WTe2 flakes over four different substrates, namely bare Si, 90 nm SiO2, 290 nm SiO2, and poly(methyl methacrylate) (PMMA). Micro-Raman spectroscopy has been employed to estimate the out-of-plane thermal conductivity by considering two characteristics out of plane Raman modes A(1)(5) and A(1)(2), as they are more sensitive to temperature variation compared with other modes. Out of the four substrates, WTe2 shows the lowest conductivity over PMMA and highest over 290 nm SiO2/Si for similar thicknesses, which arises due to the low thermal conductivity and molar mass of PMMA with respect to the molar mass of WTe2 giving rise to the lowest thermal conductivity. Our results also show that the thermal conductivity of WTe2 increases with the decrease in thickness. The authors hope that these findings shall provide a compound perspective on the thermal behavior of WTe2 with respect to different substrates.