Low-Energy Irradiation Damage in Single-Walled Carbon Nanotubes
Low-Energy Irradiation Damage in Single-Walled Carbon Nanotubes
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DOI：
10.5772/18140
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发表时间：
2007
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影响因子：
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通讯作者：
Satoru Suzuki
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文献类型：
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作者：
Satoru Suzuki
单壁碳纳米管(SWCNTs)具有独特的准一维结构和优异的电、力学性能，是未来纳米电子学最有前途的材料之一。它们还具有非常高的化学稳定性，这是因为它们具有强大的sp2键碳网络(石墨烯)，没有悬挂键。由于结构的健壮性，人们通常认为在真空中进行低能(通常为10 eV-20keV)电子和光子辐照时，当能量小于敲击阈值时，不会对单壁碳纳米管造成损害。事实上，使用低能电子或光子的分析工具，如扫描电子显微镜(SEM)，已经被普遍用于表征单壁碳纳米管，而没有引起严重的关注。然而，在2004年，我们报道了在扫描电子显微镜中的电子照射导致了由热化学气相沉积和激光烧蚀方法产生的单壁碳纳米管的严重损伤(低能量辐射损伤)(Suzuki等人，2004b)。其他使用低能电子和真空紫外(VUV)光或软X射线(特别是高亮度同步辐射光)的技术，如低能电子显微镜(LEEM)和光电子能谱，也不可避免地会损坏单壁碳纳米管。因此，关注单壁碳纳米管的低能辐照损伤具有重要的现实意义。例如，当我们测量相同的单壁碳纳米管的拉曼光谱和光致发光(PL)光谱和电学性质并拍摄扫描电子显微镜图像时，应该最后进行扫描电子显微镜观察。首先进行高分辨率的扫描电子显微镜观察，不可避免地会造成严重的破坏，并极大地影响后续的测量。低能辐照损伤及其缺陷特征也是物理上的有趣之处。在本章中，我们将回顾损伤引起的物理和化学性质的变化，以及与其他类型的损伤显著不同的缺陷性质。我们将研究缺陷诱导的金属-半导体转变的室温电学性质，并讨论其机制。我们还将总结其他类型的损伤，它们经常与低能量辐射损伤混淆，重点讨论它们之间的区别。在继续正文之前，我必须简要解释一下我是如何比较从相同的SWCNT样品中获得的光谱的。在许多对碳纳米管和石墨烯进行物理或化学处理的研究中，光谱通常被归一化到最大峰高。在……里面
Single-wall carbon nanotubes (SWCNTs) are one of the most promising materials for future nano-electronics, because of their unique quasi-one-dimensional structures and excellent electric and mechanical properties. They also have very high chemical stability, owing to their robust sp2-bonding carbon network (graphene) with no dangling bonds. Because of the structural robustness, low-energy (typically 10 eV-20 keV) electron and photon irradiation in a vacuum had been generally assumed not to cause damage to SWCNTs when the energy is smaller than the knock-on threshold. In fact, analytical tools that use low-energy electrons or photons, such as scanning electron microscopy (SEM), had been commonly used for characterization of SWCNTs without serious concerns. In 2004, however, we reported that electron irradiation in a SEM caused severe damage (low-energy irradiation damage) in SWCNTs produced by both thermal chemical vapor deposition and laser ablation methods (Suzuki et al., 2004b). Other techniques using lowenergy electrons and vacuum-ultraviolet (VUV) light or soft x-rays (especially highbrilliance synchrotron radiation light), such as low-energy electron microscopy (LEEM) and photoemission spectroscopy, also inevitably damage SWCNTs. Therefore, paying attention to the low-energy irradiation damage is practically important for those who study SWCNTs. For example, when we measure the Raman and photoluminescence (PL) spectra and electric properties and take SEM images of the same SWCNTs, the SEM observations should be done last. Doing the high-resolution SEM observation first would inevitably cause severe damage and tremendously affects the following measurements. The low-energy irradiation damage and its defect characteristics are also physically interesting. In this chapter, we will review the physical and chemical property changes induced by the damage, and the defect properties, which are significantly different from those of other types of damage. We will examine the defect-induced metal-semiconductor transition of the room-temperature electric properties and discuss its mechanism. We will also summarize other types of damage, which are often confused with the low-energy irradiation damage, focusing on the differences between them. Before continuing to the main text, I must briefly explain how I compare spectra obtained form the same SWCNT sample. In many studies of the physical or chemical treatment of SWCNTs and graphene, spectra are often normalized to the maximum peak height. In