Raman G‐Mode Splitting Detection in Multiparametric Raman Analysis of Femtosecond Laser Micro‐Processed Graphene.

ABSTRACT Raman spectroscopy is a fundamental technique to characterize graphene‐related materials, especially when they undergo functionalization or soft modification, for example, by pulsed laser irradiation. The band parameters of the graphene Raman G peak are notably sensitive to structural modification in the lattice such as defects, doping, and the application of mechanical strain. Under certain conditions of such modifications, the internal structure of the G‐band may be affected as this mode is comprised of a double degenerate phonon mode at the center of the graphene Brillouin zone, and the degeneracy may be broken. In this work, we perform in situ time evolution Raman studies and Raman mappings of the micro‐processing of fixed spots in graphene by femtosecond laser irradiation with a fixed laser power relative to the ablation threshold. We find that the graphene G mode is split into two distinguishable peaks and find differences between a one G‐peak analysis and a two‐peak one. We further prove the splitting of the G mode here is an effect of fs‐laser irradiation likely due to a combination of lattice doping and straining.