INVESTIGATION OF THE ELECTONIC STATES OF SINGE-WAL CARBON NANOTUBES PROBED BY RESONANCE RAMAN SCATTERING

我们有一个测量的光学吸收光谱和共振拉曼光谱，用于不同的单壁碳纳米管（SWNTs）和不同的直径分布的laser-furnace和碳弧方法使用NiCo， Ni， RhPd， RhPt， NiY catalysts。我们将“splay method”制作SWNT thin film and measured the optical absorption。We found three absorption bands from near infrared to visible which are reflecting π -> π D1* y D1 transitions between spike-like density of states originating from the one-dimensional van Hove singularities。吸收结构的变化随着SWNT的直径而改变。它发现了第一个和第二个吸收峰值与半导体的光学过渡和第三个金属SWNTs的正确反应。拉曼光谱在金属SWNTs吸收带的激光激发中显示出一种粉线形状，它是金属材料的特征。Thus， we named the third absorption\as "metallic window".Most of synthesis methods provide "bundles" of SWNTs。因此，这对调查捆绑的影响非常重要。这是预料到的，如果分子被隔离在孤立的SWNTs中，掺杂的溴分子可以被清除，而SWNTs内部的分子则不能被清除。使用这种剂量-剂量技术，我们已经测量了拉曼散射的孤立SWNTs。我们发现孤立的金属SWNTs不再显示风扇线的形状。This indicates clearly that the Fano interference is intrinsic to the metallic SWNT "bundles"。更进一步，我们发现了一个非常纯净的SWNTs示例展示了一个非常庞大的捆绑结构。我们已经测量了纯净样本的共振拉曼散射，并发现了放射性呼吸模式显示了大幅度的移位，而这是由SWNTs之间关于Van der Waals相互作用的理论计算预测的。

We have measured optical absorption spectra and resonance Raman spectra for various kinds of single-wall carbon nanotubes (SWNTs) with different diameter distributions fabricated by the laser-furnace and carbon arc methods using NiCo, Ni, RhPd, RhPt, NiY catalysts. We developed a "splay method" to make SWNT thin film and measured the optical absorption. We found three absorption bands from near infrared to visible which are reflecting π -> πィイD1*ィエD1 transitions between spike-like density of states originating from the one-dimensional van Hove singularities. The absorption structures changes with changing the diameter of the SWNT. It was found that the first and the second absorption peaks correspond to the optical transitions of semiconductors and the third one the metallic SWNTs. Raman spectrum taken with the laser excitation at the absorption band of metallic SWNTs shows a Fano line shape which is characteristics of metallic materials. Thus, we named the third absorption band as "metallic window".Most of synthesis methods provide "bundles" of SWNTs. Thus, it is very important to investigate the effect of the bundle. It is expected that the doped bromine molecules can be removed by the evacuation if the molecules located around isolated SWNTs while the molecules inside SWNTs bundles cannot be removed. Using this doping-dedoping technique, we have measured resonance Raman scattering of isolated SWNTs. We found that the isolated metallic SWNTs do not show Fano line shape anymore. This indicates clearly that the Fano interference is intrinsic to the metallic SWNT "bundles". Further, we found that highly purified SWNTs samples show very thick bundle structures. We have measured the resonance Raman scattering of the purified samples and found that the radial breathing modes show large up-shifts which is predicted by theoretical calculation about Van der Waals interactions between SWNTs.