Ultra-strong Adhesion of Graphene Membranes

TL;DR

This paper measures the adhesion energy of graphene sheets to silicon oxide substrates, revealing ultra-strong adhesion due to graphene's extreme flexibility and conformability, which enhances its interaction with substrates.

Contribution

The study provides direct measurements of graphene's adhesion energy, showing it exceeds typical micromechanical values and is comparable to solid/liquid adhesion energies, highlighting the importance of flexibility.

Findings

Adhesion energy for monolayer graphene is 0.45 J/m².

Adhesion energy decreases with more layers, down to 0.31 J/m² for 2-5 layers.

Graphene's flexibility enhances substrate interaction, making it more liquid-like.

Abstract

As mechanical structures enter the nanoscale regime, the influence of van der Waals forces increases. Graphene is attractive for nanomechanical systems because its Young's modulus and strength are both intrinsically high, but the mechanical behavior of graphene is also strongly influenced by the van der Waals force. For example, this force clamps graphene samples to substrates, and also holds together the individual graphene sheets in multilayer samples. Here we use a pressurized blister test to directly measure the adhesion energy of graphene sheets with a silicon oxide substrate. We find an adhesion energy of 0.45 \pm 0.02 J/m2 for monolayer graphene and 0.31 \pm 0.03 J/m2 for samples containing 2-5 graphene sheets. These values are larger than the adhesion energies measured in typical micromechanical structures and are comparable to solid/liquid adhesion energies. We attribute this to the extreme flexibility of graphene, which allows it to conform to the topography of even the smoothest substrates, thus making its interaction with the substrate more liquid-like than solid-like.