# Thermal expansion coefficient of few-layer MoS2 studied by temperature-dependent Raman spectroscopy

## TL;DR

This paper studies how few-layer MoS2 expands with temperature using Raman spectroscopy, revealing unique thermal behavior.

## Contribution

The study reveals negative thermal expansion coefficients in few-layer MoS2 at low temperatures, a novel observation.

## Key findings

- Suspended and supported MoS2 showed different thermal expansion behaviors due to substrate mismatch.
- Negative thermal expansion coefficients were observed below 175 K, attributed to bending vibrations.
- Raman spectroscopy is shown to be a feasible tool for studying thermal properties of few-layer MoS2.

## Abstract

The thermal expansion coefficient is an important thermal parameter that influences the performance of nanodevices based on two-dimensional materials. To obtain the thermal expansion coefficient of few-layer MoS2, suspended MoS2 and supported MoS2 were systematically investigated using Raman spectroscopy in the temperature range from 77 to 557 K. The temperature-dependent evolution of the Raman frequency shift for suspended MoS2 exhibited prominent differences from that for supported MoS2, obviously demonstrating the effect due to the thermal expansion coefficient mismatch between MoS2 and the substrate. The intrinsic thermal expansion coefficients of MoS2 with different numbers of layers were calculated. Interestingly, negative thermal expansion coefficients were obtained below 175 K, which was attributed to the bending vibrations in the MoS2 layer during cooling. Our results demonstrate that Raman spectroscopy is a feasible tool for investigating the thermal properties of few-layer MoS2 and will provide useful information for its further application in photoelectronic devices.