Thermal conductivity of MoS2 polycrystalline nanosheets

TL;DR

This paper introduces a residue-free transfer method for MoS2 nanosheets, enabling high-quality free-standing structures, and reports a significant reduction in their in-plane thermal conductivity measured via Raman thermometry.

Contribution

The paper presents a novel, cleaner transfer technique for MoS2 nanosheets and provides the first thermal conductivity measurements of free-standing, polycrystalline MoS2 structures.

Findings

Thermal conductivity reduced to 0.5 W/mK in MoS2 nanosheets

New transfer method yields fewer defects and cracks

Finite element simulations explain thermal behavior

Abstract

We report a technique for transferring large areas of the CVD-grown, few-layer MoS2 from the original substrate to another arbitrary substrate and onto holey substrates, in order to obtain free-standing structures. The method consists of a polymer- and residue-free, surface-tension-assisted wet transfer, in which we take advantage of the hydrophobic properties of the MoS2. The methods yields better quality transferred layers, with fewer cracks and defects, and less contamination than the widely used PMMA-mediated transfer and allows fabrication of few-layer, fee-standing structures with diameters up to 100 micro-m. We report thermal conductivity measurements by means of contactless Raman thermometry on the so-fabricated samples. The measurements revealed a strong reduction in the in-plane thermal conductivity down to 0.5 W/mK. The results are explained using finite elements method simulations for a polycrystalline film.