Optical detection of strain and doping inhomogenieties in single layer MoS2

TL;DR

This study uses spatially resolved Raman and Photoluminescence imaging to map and quantify strain and doping inhomogeneities in single-layer MoS2, revealing nanoscale structural and electronic variations relevant for device performance.

Contribution

It introduces a method to decouple and quantify strain and doping effects in single-layer MoS2 using spectral correlations, enhancing understanding of substrate-induced inhomogeneities.

Findings

Correlations between Raman bands A1' and E' enable strain and doping separation.

Linewidth of A-exciton peak correlates with strain at sub-laser spot scales.

Optical analysis reveals nanoscale structural and electronic inhomogeneities.

Abstract

Van der Waals single-layer materials are characterized by an inherent extremely low bending rigidity and therefore are prone to nanoscale structural modifications due to substrate interactions. Such interactions can induce excess charge concentration, conformational ripples and residual mechanical strain. In this work, we employed spatially resolved Raman and Photoluminescence images to investigate strain and doping inhomogeneities in a single layer exfoliated Molybdenum disulphide crystal. We have found that correlations between the spectral parameters of the most prominent Raman bands A1' and E' enable us to decouple and quantify strain and charge doping effects. In comparison with AFM topography, we show that the spatial distribution of the linewidth of the A-exciton peak is strain sensitive and can capture features smaller than the laser spot size. The presented optical analysis may have implications in the development of high-quality devices based on two-dimensional materials since structural and electronic modifications affect considerably their carrier mobility and conductivity.