| Summary: | 碩士 === 國立成功大學 === 物理學系碩博士班 === 95 === In this thesis, the electronic structures of few-layer graphenes (~1-4 layers) are investigated by the tight-binding model. They are significantly affected by the number of layers, the stacking sequences, and the intensity of stress along armchair and zigzag directions. The effects of interlayer interactions would cause the drastic changes in the energy dispersions, the band widths, and the new band-edge states. The electronic properties could reflect in the density of states (DOS) per unit area. The linear subbands correspond to finite values in DOS. The band-edge states exhibit the peaks of logarithmic divergences or square-root divergences. The deformation effects of graphene lattices under external stress are applied to the elasticity theory. The strain along x-axis is relevant to different values along y-axis and z-axis. Both intralayer and interlayer hopping integrals would be adjusted by the deformed C-C bond lengths, according to the Harrison’s rule.
The linear bands intersection of graphene shifts under deformation, but it still remains zero-gap semiconductors. The deformation influences energy bands and causes the semimetal-semiconductor transition in AB-stacked bilayer graphene. The stacking consequence would be more complicated in tri- and quadri- layers due to the increasing number of layers. In addition, the geometric structures of the tension (compression) along armchair direction are similar to those of the compression(tension) along zigzag direction for few-layer graphenes. The deformation effects would alter intralayer and interlayer hopping integrals between C-C atoms, the large shift of the Fermi momenta, the strong modification of low band structures, and the change of free carrier concentrations. It also leads to the prominent peaks in DOS. The predicted electronic properties could be verified by the scanning tunneling spectroscopy.
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