Investigation of Growth-Induced Strain in Monolayer MoS2 Grown by Chemical Vapor Deposition

TL;DR

This study investigates how growth-induced strain affects the optical properties of CVD-grown monolayer MoS2 flakes, revealing shape-dependent strain distributions and their impact on photoluminescence and Raman signals.

Contribution

It systematically quantifies strain effects in MoS2 monolayers and links growth conditions to optical property variations, providing new insights into strain management during 2D material synthesis.

Findings

Strain varies with flake shape and location.

Growth-induced strain influences PL and Raman signals.

Strain relaxation occurs after transfer, confirming thermal origin.

Abstract

Two-dimensional materials such as transitional metal dichalcogenides exhibit unique optical and electrical properties. Here we report on the varying optical properties of CVD grown MoS2 monolayer flakes with different shapes. In particular, it is observed that the perimeter and the central region of the flakes have non-uniform photoluminescence (PL) energy and intensity. We quantified these effects systematically and propose that thermally induced strain during growth is the origin. The strain relaxation after transfer of the MoS2 flakes supports this explanation. Detailed investigations of the spatial distribution of the PL energy reveal that depending on the shape of the MoS2 flakes, the width of the strain field is different. Thus, our results help to elucidate the fundamental mechanisms responsible for the differences in PL and Raman signals between the perimeter region and the center region of monolayer MoS2 and suggest that the induced strain plays an important role in the growth of monolayer materials.