Thermal Transport by Hot Carrier in Sub-10 nm MoS2 Atomic Layer

Abstract

We report a novel approach for non-contact, simultaneous determination of hot carrier diffusion coefficient (D) and interface thermal resistance (R) of sub-10 nm virgin mechanically exfoliated MoS2 nanosheets on c-Si. The effect of hot carrier diffusion in heat conduction by photon excitation, diffusion, and recombination is identified by varying the heating spot size from 0.294 μm to 1.14 μm (radius) and probing the local temperature rise using Raman spectroscopy. R is determined as 4.46~7.66×10-8 K·m2/W, indicating excellent contact between MoS2 and c-Si. D is determined to be 1.07~1.62 cm2/s, showing little dependence on the thickness. Unlike previous methods of making electrical contacts and applying an electric field for D measurement, our technique has the advantage of being truly non-contact and noninvasive, and is able to characterize the electron diffusion behavior of virgin 2D materials. Also, it points out that hot carrier diffusion needs to be taken into serious consideration in Raman-based thermal properties characterization of 2D materials, especially under very tightly focused laser heating whose spot size is comparable to the hot carrier diffusion length.