Strain Modulation of Graphene by Nanoscale Substrate Curvatures: A Molecular View

TL;DR

This study combines experimental Raman analysis and molecular dynamics simulations to understand how nanoscale substrate curvatures induce strain in graphene, revealing size-dependent strain effects crucial for strain engineering.

Contribution

It provides a molecular-level understanding of how substrate curvature influences strain in graphene, aiding precise strain engineering strategies.

Findings

Smaller nanospheres induce larger tensile strain in graphene.

Molecular dynamics simulations confirm size-dependent strain and microscopic interaction mechanisms.

Experimental and theoretical results agree on the strain dependence on nanosphere size.

Abstract

Spatially nonuniform strain is important for engineering the pseudomagnetic field and band structure of graphene. Despite the wide interest in strain engineering, there is still a lack of control on device-compatible strain patterns due to the limited understanding of the structure-strain relationship. Here, we study the effect of substrate corrugation and curvature on the strain profiles of graphene via combined experimental and theoretical studies of a model system: graphene on closely packed SiO2 nanospheres with different diameters (20-200 nm). Experimentally, via quantitative Raman analysis, we observe partial adhesion and wrinkle features and find that smaller nanospheres induce larger tensile strain in graphene, theoretically, molecular dynamics simulations confirm the same microscopic structure and size dependence of strain and reveal that a larger strain is caused by a stronger, inhomogeneous interaction force between smaller nanospheres and graphene. This molecular-level understanding of the strain mechanism is important for strain engineering of graphene and other two-dimensional materials.