Raman spectroscopy of graphene | Posted on:2010-02-27 | Degree:Ph.D | Type:Dissertation | University:Columbia University | Candidate:Yan, Jun | Full Text:PDF | GTID:1441390002473547 | Subject:Physics | Abstract/Summary: | | In this dissertation I present my studies of electron-phonon interactions in graphene using Raman scattering.;Graphene is a single sheet of carbon atoms arranged in a honeycomb lattice. It is a novel electron system in the 2D atomic limit that hosts chiral massless Dirac fermions. The interactions of phonons and excitations from these unique charge carriers attract significant contemporary theoretical and experimental attention. We studied the effect of charge doping on the long wavelength optical phonon (G band) in graphene. We found that both the energy and the life time of the G band are tunable with employment of the electric field effect using a gate electrode.;Bilayer graphene is an equally interesting and unique electron system. Its low energy band structure and electron density of states are significantly different from those of a monolayer. We investigated the electric field effect on bilayer graphene and discovered a resonant electron-phonon interaction induced phonon anomaly. The observation of the phonon anomaly is closely linked to the large electron density of states of bilayer graphene. The size of the phonon anomaly offers a venue for characterization of sample quality.;Bilayer graphene exhibits intriguing inversion symmetry breaking effects. We use polymer electrolyte to gate bilayer graphene and found that the even-parity and odd-parity long-wavelength in-plane optical phonons become entangled. The coupling of the two modes displays dramatic mode splitting and intensity reversal phenomena, offering a direct proof for the loss of inversion symmetry.;We used magneto-phonon resonance (MPR) to study the Landau level structures of Dirac fermions in graphene and Kish graphite. The MPR is a very sensitive probe for the Landau level transitions. We found that the interaction effects depend crucially on the competition between the mode coupling strength and the Landau level width. We discovered that in Kish graphite there exists a narrow Landau level transition of 6.5meV in width at 5T. To the best of our knowledge, this is the sharpest Landau level observed in this magnetic field range for all graphitic materials. | Keywords/Search Tags: | Graphene, Landau level, Electron, Phonon | | Related items |
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