Graphenes flakes under controlled biaxial deformation

TL;DR

This study develops an experimental setup to apply controlled biaxial strain to graphene, using Raman spectroscopy and simulations to analyze phonon shifts and stress uptake, advancing understanding of 2D material mechanics.

Contribution

It introduces a novel device for applying controlled biaxial strain to graphene and combines experimental and simulation methods to analyze phonon behavior under strain.

Findings

Raman G and 2D peaks shift with strain in the range of 62.3 to 148.2 cm^-1/%

Gruneisen parameters for G and 2D peaks are between 1.97 and 2.86

Experimental results agree well with molecular dynamics simulations

Abstract

Thin membranes, such as monolayer graphene of monoatomic thickness, are bound to exhibit lateral buckling under uniaxial tensile loading that impairs its mechanical behaviour. In this work, we have developed an experimental device to subject 2D materials to controlled equibiaxial strain on supported beams that can be flexed up or down to subject the material to either compression or tension, respectively. Using strain gauges in tandem with Raman spectroscopy measurements, we monitor the G and 2D phonon properties of graphene under biaxial strain and thus extract important information about the uptake of stress under these conditions. The experimental shift over strain for the G and 2D Raman peaks were found to be in the range of 62.3 \pm 5 cm^-1/%, and 148.2 \pm 6 cm^-1/%, respectively, for monolayer but also bilayer graphenes. The corresponding Gruneisen parameters for the G and 2D peaks were found to be between 1.97 \pm 0.15 and 2.86 \pm 0.12, respectively. These values agree reasonable well with those obtained from small-strain bubble-type experiments. The results presented are also backed up by classical and ab initio molecular dynamics simulations and excellent agreement of \Gamma-E2g shifts with strains and the Gruneisen parameter was observed.