Thermal Dynamics of Graphene Edges Investigated by Polarized Raman Spectroscopy

TL;DR

This study uses polarized Raman spectroscopy to analyze how graphene edges change structurally under thermal annealing, revealing edge instability and potential for property tuning.

Contribution

It provides new insights into the thermal stability and structural evolution of graphene edges, especially the transformation of zigzag to armchair segments during annealing.

Findings

Graphene edges are unstable at temperatures as low as 200°C.

Zigzag edges rearrange into armchair segments upon annealing.

Armchair edges remain stable even at 500°C.

Abstract

In this report, we present Raman spectroscopy investigation of the thermal stability and dynamics of graphene edges. It was found that graphene edges (both armchair and zigzag) are not stable and undergo modifications even at temperature as low as 200{\deg}C. Based on polarized Raman results, we provide possible structural models on how graphene edges change during annealing. The zigzag edges rearrange and form armchair segments that are \pm30{\deg} relative to the edge direction, while armchair edges are dominated by armchair segments even at annealing temperature as high as 500{\deg}C. The modifications of edge structures by thermal annealing (zigzag segments rearrange in form of armchair segments) provide a flexible way to control the electronic properties of graphene and graphene nanostructures.