High-fidelity conformation of graphene to SiO2 topographic features

TL;DR

This study demonstrates that graphene closely conforms to the topography of SiO2 substrates with nearly 99% fidelity, providing insights into strain engineering and the morphology of graphene on rough surfaces.

Contribution

The paper provides high-resolution measurements and a quantitative model explaining how graphene's morphology is determined by substrate roughness and adhesion.

Findings

Graphene is slightly smoother than SiO2 substrate.

Graphene conforms to substrate features with nearly 99% fidelity.

High-resolution microscopy reveals substrate roughness at the nanometer scale.

Abstract

Strain engineering of graphene through interaction with a patterned substrate offers the possibility of tailoring its electronic properties, but will require detailed understanding of how graphene's morphology is determined by the underlying substrate. However, previous experimental reports have drawn conflicting conclusions about the structure of graphene on SiO2. Here we show that high-resolution non-contact atomic force microscopy of SiO2 reveals roughness at the few-nm length scale unresolved in previous measurements, and scanning tunneling microscopy of graphene on SiO2 shows it to be slightly smoother than the supporting SiO2 substrate. Quantitative analysis of the competition between bending rigidity of the graphene and adhesion to the substrate explains the observed roughness of monolayer graphene on SiO2 as extrinsic, and provides a natural, intuitive description in terms of highly conformal adhesion. The analysis indicates that graphene adopts the conformation of the underlying substrate down to the smallest features with nearly 99% fidelity.