# Evaluating arbitrary strain configurations and doping in graphene with Raman spectroscopy

## TL;DR

This paper presents a Raman spectroscopy method to evaluate unknown strain and doping in graphene by separating hydrostatic and shear strain effects through correlation analysis of Raman peak shifts, applicable to various strain configurations.

## Contribution

The authors introduce a novel Raman spectroscopy approach that independently quantifies hydrostatic strain, shear strain, and doping in graphene without prior assumptions about strain configuration.

## Key findings

- Effective separation of strain and doping effects in Raman spectra.
- Quantitative measurement of hydrostatic and shear strain in graphene.
- Validation on uniaxial stress and nanostructure-induced strain cases.

## Abstract

Raman spectroscopy is a powerful tool for characterizing the local properties of graphene. Here, we introduce a method for evaluating unknown strain configurations and simultaneous doping. It relies on separating the effects of hydrostatic strain (peak shift) and shear strain (peak splitting) on the Raman spectrum of graphene. The peak shifts from hydrostatic strain and doping are separated with a correlation analysis of the 2D and G frequencies. This enables us to obtain the local hydrostatic strain, shear strain and doping without any assumption on the strain configuration prior to the analysis. We demonstrate our approach for two model cases: Graphene under uniaxial stress on a PMMA substrate and graphene suspended on nanostructures that induce an unknown strain configuration. We measured $\omega_\mathrm{2D}/\omega_\mathrm{G} = 2.21 \pm 0.05$ for pure hydrostatic strain. Raman scattering with circular corotating polarization is ideal for analyzing strain and doping, especially for weak strain when the peak splitting by shear strain cannot be resolved.