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Nonlinear Optical Spectroscopy of Isolated Single-Walled Carbon Nanotubes.

机译：隔离的单壁碳纳米管的非线性光谱。

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摘要

Single-walled and multi-walled carbon nanotubes (SWNTs) and (MWNTs) are low dimensional conductors with unique electronic and electro optic properties. To probe these properties, we investigate the third-order, coherent anti-Stokes (CAS) response of individual SWNTs using a dual color, four-wave-mixing technique. Despite being nanoscale objects much smaller than the wavelength of light, the CAS response allows single SWNTs to be optically imaged with good spatial resolution using picosecond infrared laser excitation pulses and a diffraction limited, confocal microscopy technique. The absence of a pronounced Raman signature shows that the CAS response is dominated by electronic rather than vibrational dynamics. The dependence of the CAS signal on fundamental morphological properties of nanotubes is investigated and characterized. The nonlinear signal is found to depend strongly on nanotube diameter and polarization angle while the dependence on length and individual nanotube chirality is much less clear. The CAS signal is also strongly dependent on metallicity, allowing for straightforward optical discrimination between metallic and semiconducting SWNTs. However, variability of undetermined origin still exists in the CAS signal intensity from a given nanotube type. This variability may depend on electrical contact resistances, charge carrier densities, and local physiochemical effects. Furthermore, identification of the third-order CAS response in SWNTs requires proper accounting for other nonlinear luminescence mechanisms. The SWNT and MWNT optical response is found to contain contributions from competing multiphoton processes, including third-order vibrational and electronic mechanisms as well as second-order fluorescence. The relative intensity of these nonlinear processes is investigated and compared.
机译：单壁和多壁碳纳米管（SWNT）和（MWNT）是具有独特的电子和光电特性的低维导体。为了探究这些特性，我们使用双色四波混频技术研究了单个SWNT的三阶相干抗斯托克斯（CAS）响应。尽管是比光波长小得多的纳米级物体，CAS响应仍允许使用皮秒红外激光激发脉冲和衍射受限的共聚焦显微镜技术以良好的空间分辨率对单个SWNT进行光学成像。没有明显的拉曼信号表明，CAS反应主要由电子动力学而非振动动力学决定。研究并表征了CAS信号对纳米管基本形态特性的依赖性。发现非线性信号在很大程度上取决于纳米管的直径和极化角，而对长度和各个纳米管手性的依赖性则不太清楚。 CAS信号还强烈依赖于金属性，从而可以在金属和半导体SWNT之间进行直接的光学区分。但是，来自给定纳米管类型的CAS信号强度仍然存在不确定的起源变异。这种变化可能取决于电接触电阻，电荷载流子密度和局部物理化学效应。此外，鉴定SWNT中的三阶CAS响应需要适当考虑其他非线性发光机制。发现SWNT和MWNT的光学响应包含竞争的多光子过程的贡献，包括三阶振动和电子机制以及二阶荧光。研究并比较了这些非线性过程的相对强度。

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  • 作者

    Sheps, Tatyana.;

  • 作者单位

    University of California, Irvine.;

  • 授予单位 University of California, Irvine.;
  • 学科 Nanoscience.;Physics Electricity and Magnetism.
  • 学位 M.S.
  • 年度 2011
  • 页码 49 p.
  • 总页数 49
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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