Evidence of Kohn anomalies In quasi-freestanding graphene on Pt(111)

摘要

High-resolution electron energy loss spectroscopy has been used to probe phonon dispersion in quasi-freestanding graphene epitaxially grown on Pt(111). We report direct evidence of the existence of Kohn anomalies in the Γ-E_(2g) and K-A_2 optical phonon modes. These findings contrast with previous results on graphene/Ni(111), for which no Kohn anomalies were detected. Thus, such dissimilarity arises from the different interactions existing between graphene/Pt(111) (quasi-freestanding graphene) and graphene/Ni(111) (strongly interacting with the substrate). Hence, the phonon spectrum can be used to finely study the graphene-substrate coupling.