Observation of strain-free rolled-up CVD graphene single layers: towards unstrained heterostructures

TL;DR

This study demonstrates the creation of strain-free, homogeneously curved CVD graphene layers with well-defined curvature, enabling insights into their elastic properties and the effects of bending on electronic characteristics.

Contribution

It introduces a method to produce and analyze strain-free curved graphene structures with controlled curvature, advancing understanding of their elastic constants and electronic behavior.

Findings

Graphene can be homogeneously curved with radii of 600-1200 nm.

Elastic constants of graphene are consistent with literature values.

Curvature alone does not significantly alter graphene's Raman signature.

Abstract

Single layer graphene foils produced by Chemical Vapor Deposition (CVD) are rolled with self-positioned layers of InGaAs/Cr forming compact multi-turn tubular structures that consist on successive graphene/metal/semiconductor heterojunctions on a radial superlattice. Using elasticity theory and Raman spectroscopy we show that it is possible to produce homogeneously curved graphene with curvature radius on the 600nm-1200nm range. Additionally, the study of tubular structures also allows the extraction of values for the elastic constants of graphene that are in excellent agreement with elastic constants found in the literature. However, our process has the advantage of leading to a well-defined and nonlocal curvature. Since our curvature radius lie in a range between the large radius studied using mechanical bending and the reduced radius induced by Atomic Force Microscopy experiments we can figure out whether bending effects can be a majoritary driving force for modifications in graphene electronic status. From the results described in this work one can assume that curvature effects solely do not modify the Raman signature of graphene and that strain phenomena observed previously can be ascribed to stretching due to the formation of local atomic bonds. This implies that the interactions of graphene with additional materials on heterostructures must be investigated in detail prior to the development of applications and devices.