Abstract
We present an analysis of deep-UV Raman measurements of graphite, graphene, and carbon nanotubes. For excitation energies above the strong optical absorption peak at the point in the Brillouin zone ( eV), we partially suppress double-resonant scattering processes and observe the two-phonon density of states of carbon nanomaterials. The measured peaks are assigned to contributions from LO, TO, and LA phonon branches, supported by calculations of the phonon dispersion. Moreover, we gain access to the infrared-active mode in graphite. By lowering the excitation energy and thus allowing double-resonant scattering processes, we demonstrate the rise of the mode in graphite with ultrashort phonon wave vectors.
- Received 27 March 2015
- Revised 27 May 2015
DOI:https://doi.org/10.1103/PhysRevB.92.041401
©2015 American Physical Society