title: Real-time observation of interlayer vibrations in bilayer and few-layer graphene.
abstract: We report real-time observation of the interlayer shearing mode, corresponding to the lateral oscillation of graphene planes, for bi- and few-layer graphene. Using a femtosecond pump-probe technique, we have followed coherent oscillations of this vibrational mode directly in the time domain. The shearing-mode frequency, as expected for an interlayer mode, exhibits a strong and systematic dependence on the number of layers, varying from 1.32 THz for the bulk limit to 0.85 THz for bilayer graphene. We explored the role of interactions with the external environment on this vibrational mode by comparing the response observed for graphene layers supported by different substrates and suspended in free space. No significant frequency shifts were observed.
authors.affiliation: Department of Physics, Columbia University , New York, New York 10027, United States.
authors.forename: Davide
authors.initials: D
authors.lastname: Boschetto
authors.forename: Leandro
authors.initials: L
authors.lastname: Malard
authors.forename: Chun Hung
authors.initials: CH
authors.lastname: Lui
authors.forename: Kin Fai
authors.initials: KF
authors.lastname: Mak
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Li
authors.forename: Hugen
authors.initials: H
authors.lastname: Yan
authors.forename: Tony F
authors.initials: TF
authors.lastname: Heinz
mesh_terms: D006108:Graphite / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry*; D010316:Particle Size; D013059:Spectrum Analysis, Raman; D013499:Surface Properties; D014732:Vibration
chemical_list: D006108:Graphite