Determination of the elastic moduli of CVD graphene by probing graphene/polymer Bragg stacks

TL;DR

This study measures the elastic moduli of CVD graphene with wrinkles using Brillouin Light Spectroscopy, revealing that wrinkles reduce the Young's modulus by about 30% compared to flat exfoliated graphene.

Contribution

It introduces a novel method to determine the elastic properties of wrinkled CVD graphene within polymer stacks, highlighting the impact of wrinkles on mechanical strength.

Findings

Young's modulus of CVD graphene is approximately 680 GPa.

Wrinkles in CVD graphene decrease its Young's modulus by about 30%.

The method can be extended to study other 2D materials with surface features.

Abstract

Graphene has been widely used in the form of micro-flakes to fabricate composite materials with enhanced mechanical properties. Due to the small size of the inclusions and their random orientation within the matrix, the superior mechanical properties of graphene cannot be fully exploited. Recently, attempts have been made to fabricate nanolaminate composites by interleaving large sheets of chemical vapor deposition (CVD) monolayer graphene between thin layers of polymer matrices. However, CVD graphene is inevitably accompanied by wrinkles that are formed in the synthesis process, and it remains unknown how the wrinkles affect the mechanical properties of graphene. Here, we employ Brillouin Light Spectroscopy (BLS) to study the elastic moduli of CVD graphene by probing graphene/poly(methylmethacrylate) hybrid Bragg stacks at zero strain. We find the Young's and shear moduli of the CVD graphene, which has wrinkles in the form of sharp elevations of height of about 6 nm and a FWHM of ca. 30 nm, to be 680 and 290 GPa, respectively, with the former being about 30% lower than that of exfoliated, flat graphene. This work sheds light on the elastic properties of CVD graphene and provides a method that can be extended to studying the wrinkle-induced softening effect in other two-dimensional materials.