| Summary: | 碩士 === 國立臺灣大學 === 工程科學及海洋工程學研究所 === 99 === The main purpose of this thesis is to investigate the electronic properties of 1D graphene nanoribbons and carbon nanotubes without applied fields. At first, the concept of grapheme is introduced, and then two different structures(graphene nanoribbons and carbon nanotubes) is cut in the ideal sheet along the highly symmetric directions to obtain zigzag and armchair edge. Some physical properties of energy dispersion relations can be discussed by tight-binding approximation. The numerical analysis shows that the electronic properties of graphene nanoribbons are dominated by the edge structures and ribbon widths. Even though all of the zigzag nanoribbons are metallic, armchair nanoribbons are metallic only for N=3m+2 (where m is a positive integer), and which generates band gaps in the other case. The band gaps decrease as the widths of the armchair graphene nanoribbons increase. Furthermore, for carbon nanotubes, the electronic properties are determined by their geometry. The metallic or semiconducting characters of SWCNT are decided by changing the diameter and chirality. In semiconducting carbon nanotubes, the band gaps of the tubes are inversely proportional to the diameter. Therefore, the band gaps can be adjusted easily.
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