Date of Award

7-1-2015

Degree Type

Thesis

University or Center

Clark Atlanta University(CAU)

Degree Name

M.S.

Department

Physics

First Advisor

Xiao-Qian Wang, Ph.D

Abstract

We have studied the electronic characteristics of covalently functionalized graphene by nitrophenol groups using first-principles density-functional theory calculations. The nitrophenyl functionalization leads to a band gap opening in graphene and transition from a semi-metallic to semiconducting state. The induced gap is shown to be attributed to the modification of the π-conjugation that depends on the configuration for a pair of monovalent adsorption. A detailed analysis reveals that this intriguing magnetism modulation by strain stems from the redistribution of spin-polarized electrons induced by local lattice distortions. A detailed analysis suggests a sensitive and effective way to tailor properties of graphene for future applications in nanoscale devices.

The quest for low-dimensional boron structures has been motivated by the potential applications of light-weight materials. Recently, a semi-metallic two-dimensional boron allotrope was predicted via ab initio evolutionary structure search, which is markedly lower in energy than the planar structures composed of triangular motifs and hexagonal holes. The emergence of a Dirac cone in the band structure demonstrates an intriguing perspective for quasiplanar counterpart of graphene. We studied the corresponding single walled boron nanotubes derived from the quasiplanar boron structure. In particular, our results are identified to have a Dirac cone, as well. The buckling and coupling between the two sublattices not only enhance the stability, but also are key factors to the emergence of the Dirac cone.

Signature Location_Supplemental file.pdf (45 kB)
Notice to Users, Transmittal and Statement of Understanding

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