Raman Spectroscopy of Lithographically Defined Graphene Nanoribbons ‐ Influence of Size and Defects

Abstract

AbstractGraphene nanostructures are an important building block to make use of the properties of graphene for applications in integrated devices. It is important to study edge roughness and defects in such nanostructures for further device improvement as they become important when downscaling structures. Recent Raman studies focused mainly on the D mode to characterize the defects in graphene and graphene nanoribbons (GNR) whereas not much attention has been paid to the D′ mode that is smaller in Raman intensity. In this work we show by comparison with AFM measurements of the GNR width that both defect‐induced Raman modes have different scattering length scales. Furthermore the size and quality of lithographically defined GNRs can be estimated by a close analysis of the defect‐induced Raman modes and the width of the well‐studied 2D mode of graphene. The findings are explained by the different vibration pattern for both Raman modes and the differences in the matrix elements determining the Raman intensity, i.e. the electron‐phonon coupling and the phonon density of states.