Anisotropic In-plane Thermal Conductivity of Freestanding Few-layer ReS2

Rhenium disulfide (ReS2) is a unique TMDC with a strong in-plane anisotropy and weak interlayer coupling. The pronounced anisotropy in the thermal conductivity observed in bulk ReS2 flakes (exceeding 60 nm) makes them valuable for applications that require directional heat management or isolation. Whether this anisotropy is maintained below 10 nm has not yet been studied. Here, we measured the thermal conductivity of freestanding, exfoliated, few-layer ReS2 samples (thickness < 10 nm) on SiO2/Si holey substrates using the optothermal Raman technique. Polarization-dependent Raman measurements revealed variation in thermal conductivity along the high symmetry axes. The total in-plane thermal conductivities show a nonmonotonic trend with ReS2 thickness ranging from 2.5 to 8 nm. The in-plane thermal conductivity of few-layer ReS2 devices, which varies with thickness, holds significant potential for applications in nanoscale thermoelectric devices.