公度双壁碳纳米管层间耦合对其场发射特性影响的研究

采用紧束缚能带理论，利用所提出的考虑卷曲效应的紧束缚能量哈密顿量，建立了公度双壁碳纳米管(DWNT)的能带结构模型；基于碳纳米管(CNT)发射电流与其能带结构的相关性，定量分析了公度DWNT的层间耦合作用对其场发射电流的影响.结果表明：在层间耦合作用下，DWNT的带结构中部分简并能级发生劈裂，同时使禁带宽度发生改变.前一个因素增加了电子发射的通道，后一个因素改变价带中参与发射的电子数量，导致在一定外电场下，DWNT与其外层的SWNT相比，场发射电流有一定程度的增加，且半导体性管发射电流增幅比金属性管大，在 关键词： 公度双壁碳纳米管 能带结构 层间耦合作用 卷曲效应

The effect of interwall coupling interaction on the field emission characteristics of commensurate double-walled carbon nanotubes

The band structure model of commensurate double-walled carbon nanotube (DWNT) was built by using tight-binding Hamiltonian with curvature effect included. The field emission characteristics of commensurate DWNT were quantitatively investigated basing on its dependence on the band structure. The results indicate that interwall coupling interaction (ICI) can form additional electronic energy level in the band structure of DWNT so as to increase the emitting channel of electrons;and at the same time, it can also increase the energy gap of the metallic DWNT and decrease that of the semiconducting DWNT, which will result in a change in the number of electrons emitted from the valence band. At a given applied electric field, the emission current of DWNT has an obvious increase, compared with that of DWNT when ICI is turn off, and the current increment of semiconducting DWNT is larger than that of the metallic one. At an applied electric field of 5V/μm, the field emission currents of commensurate DWNTs (6,6)&(12,12), (10,0)&(20,0) and (8,2)&(16,4) have an increase of about 3%,10% and 4%, respectively, compared with those when ICI is turn off. The results reveal that ICI contributes to the transport and electron emission of DWNT, which is helpful for understanding the field emission mechanism of DWNT ,and hence that of MWNT.