Electronic properties of carbon nanotubes by transmission electron energy-loss spectroscopy
Electronic properties of carbon nanotubes by transmission electron energy-loss spectroscopy
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DOI：
10.1103/physrevb.64.195404
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发表时间：
2001-10
影响因子：
3.7
通讯作者：
B. Reed;M. Sarikaya
中科院分区：
文献类型：
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作者：
B. Reed;M. Sarikaya
我们介绍了在扫描透射电子显微镜下对孤立的单壁碳纳米管及其束进行的电子能量损失光谱测量。在一系列的冲击参数范围内，从样品的中心到材料外的几纳米处，可以获得光谱。曲线拟合技术显示在\ensuremath{\sim} 2 \char 2130 {}eV范围内有5个峰。这些包括表面和体等离子体激元以及直接\ensuremath{\pi}到${\ensuremath{\pi}}^{*}$的带间跃迁。在整个数据集中跟踪这些峰的能量、高度和宽度，以确定它们与束直径和冲击参数的依赖关系。将外激表面模峰的高度与随冲击参数呈指数变化和随束直径呈幂律变化的模型进行了比较。幂律指数从\ensuremath{\pi}到${\ensuremath{\pi}}^{*}$模式的\ensuremath{\sim} 0.4到$\ensuremath{\pi}+\ensuremath{\sigma}$体等离子体激元的\ensuremath{\sim} 1.3不等，表面等离子体激元接近1。峰高数据表明对其中一束的密度不均匀性敏感，并且可能对单管和小束之间的手性矢量的随机变化敏感。这些模式在峰值能量和宽度数据中得到进一步阐明。
We present electron energy-loss spectroscopy measurements on isolated single-walled carbon nanotubes and their bundles performed in a scanning transmission-electron microscope. Spectra are obtained over a range of impact parameters, from the centers of the samples to several nanometers outside the material. Curve-fitting techniques reveal five peaks in the range \ensuremath{\sim}2\char21{}30 eV. These include surface and bulk plasmons and direct \ensuremath{\pi} to ${\ensuremath{\pi}}^{*}$ interband transitions. The energies, heights, and widths of these peaks are tracked throughout the data sets in order to determine their dependence on bundle diameter and impact parameter. The heights of the externally excited surface mode peaks are compared to a model that varies exponentially with impact parameter and by a power law with bundle diameter. The power-law exponent varies from \ensuremath{\sim}0.4 for the \ensuremath{\pi} to ${\ensuremath{\pi}}^{*}$ mode to \ensuremath{\sim}1.3 for the $\ensuremath{\pi}+\ensuremath{\sigma}$ bulk plasmon, with the surface plasmons close to 1. The peak height data suggest a sensitivity to density inhomogeneities in one of the bundles and possibly to random variations in the chiral vectors among the single tubes and small bundles. These patterns are further elucidated in the peak energy and width data.