Layer number and stacking order-dependent thermal transport in molybdenum disulfide with sulfur vacancies

Abstract

Recent theoretical works on two-dimensional molybdenum disulfide, MoS$_2$, with sulfur vacancies predict that the suppression of thermal transport in MoS$_2$ by point defects is more prominent in monolayers and becomes negligible as layer number increases. Here, we investigate experimentally the thermal transport properties of two-dimensional molybdenum disulfide crystals with inherent sulfur vacancies. We study the first-order temperature coefficients of interlayer and intralayer Raman modes of MoS$_2$ crystals with different layer numbers and stacking orders. The in-plane thermal conductivity ($\kappa$) and total interface conductance per unit area ($ g $) across the 2D material-substrate interface of mono-, bi- and tri-layer MoS$_2$ samples are measured using the micro-Raman thermometry. Our results clearly demonstrate that the thermal conductivity is significantly suppressed by sulfur vacancies in monolayer MoS$_2$. However, this reduction in $\kappa$ becomes less evident as the layer number increases, confirming the theoretical predictions. No significant variation is observed in the $\kappa$ and $ g $ values of 2H and 3R stacked bilayer MoS$_2$ samples.