Thermal Dynamics of Graphene Edges Investigated by Polarized Raman Spectroscopy

In this report we present Raman spectroscopy investigation of the thermal stability and dynamics of graphene edges. It is found that graphene edges (both armchair and zigzag) are not stable and undergo modifications even at temperature as low as 200 degrees C. On the basis of 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 +/- 30 degrees relative to the edge direction, while armchair edges are dominated by armchair segments even at annealing temperature as high as 500 degrees 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.