Phonon and Thermal Properties of Thin Films Made from WS₂ Mono- and Few-Layer Flakes

Abstract

We first report the temperature phonon properties of a large-area thin film (lateral size: ∼mm, thickness ∼50 nm) made from WS2 mono and few layers deposited on the SiO2/Si substrate. We show that temperature phonon properties probed by Raman spectroscopy significantly differ for bulk and thin-film systems in a temperature range of 90–450 K; however, both exhibit strong temperature-dependent phonon energy nonlinear behavior. Employing the optothermal Raman method, we also estimate thin-film thermal conductivity (κ = 4.3 W/(m K)) and thermal interface conductance (g = 5.5 MW/(m2 K)) at room temperature. We find that the thermal properties of thin films (κ and g) are 1 order of magnitude lower than that for bulk or monolayer WS2, which is caused by a reduction in flake size and an increase in boundary scattering. This finding is important for heat management in future applications of thin films made from two-dimensional (2D) nanoflakes.