有限长碳纳米管的边缘效应
Edge effects in finite elongated carbon nanotubes
摘要：
研究了有限尺寸效应对长锯齿形和扶手椅形碳纳米管电子结构的重要性。我们分析了封端的（6，6），（8，0）和（9，0）单壁碳纳米管的电子结构作为其长度的函数，最多60 nm，使用分而治之的密度泛函理论的方法。对于所研究的金属纳米管，在40 nm的长度处恢复了无限碳纳米管的态密度中出现的大部分物理特征。所研究的（8，0）半导体纳米管在能隙内表现出明显的边缘效应，该边缘效应与纳米管的长度成反比。结果，能隙从针对周期系统计算的~1 eV的值减小到针对加帽的62 nm长CNT计算的~ 0.25eV的值。这些边缘效应预期仅在管长度超过6微米时变得可忽略不计。我们的研究结果表明，仔细剪裁的性质的系统和它的盖帽单位时，应适用于设计新的纳米电子器件的基础上碳纳米管。这些结论预计将适用于其他一维系统，如石墨烯纳米带，导电聚合物和DNA分子。
英文摘要：
The importance of finite-size effects for the electronic structure of long zigzag and armchair carbon nanotubes is studied. We analyze the electronic structure of capped (6,6), (8,0), and (9,0) single walled carbon nanotubes as a function of their length up to 60 nm, using a divide and conquer density functional theory approach. For the metallic nanotubes studied, most of the physical features appearing in the density of states of an infinite carbon nanotube are recovered at a length of 40 nm. The (8,0) semi-conducting nanotube studied exhibits pronounced edge effects within the energy gap that scale as the inverse of the length of the nanotube. As a result, the energy gap reduces from the value of ~1 eV calculated for the periodic system to a value of ~0.25 eV calculated for a capped 62 nm long CNT. These edge effects are expected to become negligible only at tube lengths exceeding 6 micrometers. Our results indicate that careful tailoring of the nature of the system and its capping units should be applied when designing new nanoelectronic devices based on carbon nanotubes. These conclusions are expected to hold for other one-dimensional systems such as graphene nanoribbons, conducting polymers, and DNA molecules.
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