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標題: | 石墨烯與奈米碳管之電子特性 Electronic properties in graphene and carbon nanotubes |
作者: | Tsung-Lin Tsai 蔡宗霖 |
指導教授: | 薛文証(Wen-Jeng Hsueh) |
關鍵字: | 石墨烯,奈米石墨帶,奈米碳管,鋸齒狀,手椅狀,緊束模型近似法,折疊近似法,能帶結構, graphene,graphene nanoribbons,carbon nanotubes,zigzag,armchair,tight-binding approximation,zone-folding approximation,band structure, |
出版年 : | 2011 |
學位: | 碩士 |
摘要: | 本論文主要目的在探討無外加任何場的情況下,一維奈米石墨帶與奈米碳管之電子特性。首先對石墨烯的觀念和理論做基本的介紹,之後針對這兩種不同的結構(奈米石墨帶和奈米碳管),沿著高對稱性切口方向所獲得的鋸齒狀與手椅狀結構中,利用緊束模型近似法來計算色散關係式,接著再從這些色散關係式去探討能帶結構的一些物理特性。透過數值分析結果顯示,對於奈米石墨帶而言,它的電子特性是由邊界結構與寬度所決定。所有的鋸齒狀結構都是金屬特性,而手椅狀結構只有在寬度為 是金屬(其中 是一個正整數),其餘的情況下皆會有能隙產生,且能隙是隨著奈米石墨帶寬度的增加而減小。此外,對於奈米碳管來說,導電特性主要是由本身自己的幾何結構所決定。藉著改變螺旋角及直徑的不同,單壁奈米碳管會呈現出金屬或半導體特性。在半導體性質的奈米碳管中,會發現到直徑與能隙之間的關係是成反比。因此,可以非常容易地調節其能隙大小。 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. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/23629 |
全文授權: | 未授權 |
顯示於系所單位: | 工程科學及海洋工程學系 |
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