Temperature-Dependent Raman Spectroscopy of Graphitic Nanomaterials

摘要

The sp~2 carbonaceous molecules possess a single atomic type per unit cell, which makes these materials very good candidates for quantum mechanical studies associated with their vibrational and electronic energy levels. Significant findings, such as the Kohn anomaly, electron-phonon interactions, and other exciton-related effects, associated with these molecules can be transported to other 2-D materials. Information derived from the distinctive Raman bands from a single layer of carbon atoms also aids in gaining insight into new physics from such materials and other graphitic nanomaterials. The present paper focuses on our investigations of the G, D, and G' bands of graphene and graphite, and the specific information provided by each. The G-band peak located at ～1586 cm~(-1), shared by all sp~2 carbons, has been used by us extensively in the estimation of thermal conductivity and thermal expansion characteristics linked to single-walled carbon nanotubes. In addition, we have investigated functionalized graphene nanoplatelets. For all three materials (graphene, graphite, and functionalized graphene nanoplatelets), we made use of the relationship discovered by Tuinstra and Koenig based on the relative intensities of the D and G Raman bands. In addition to the analysis based on Raman spectroscopy of the nanomaterial samples, SEM visualization/dimensional analysis was also performed on the graphene nanoplatelet samples. The bulk macroscopic 3-D character of graphite was clearly apparent, in contrast to the 2-D nature of graphene. However, the graphene nanoplatelets exhibited both 2-D and 3-D characteristics, without one dimension dominating the other.