Nanoscale optical imaging of electronic and vibronic states in carbon nanotubes

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Based on their exceptional properties, single-walled carbon nanotubes (SWNTs) will eventually play an important role as nanometer-scale building-blocks for photonics, opto- and nanoelectronics. In a real SWNT however, different types of localized defects alter the desired properties such as the quasi-infinite spatial extent of excitonic band states. Furthermore, defect related trap states are discussed to be responsible for the extremely low photoluminescence quantum yield of SWNTs which is expected to limit their applicability in devices.We propose to study the electronic and vibronic properties of single SWNTs by near-field optical spectroscopy with a spatial resolution of 10 nm. We image the spatial extent of the photoluminescent excitonic states in a given SWNT and investigate the spectroscopic signatures of trap states to identify their physical origin. Our results will be of major significance for the understanding of the role of localized defects in quasi-infinite electronic systems. From this, device concepts that benefit from defects, as in the case of intentionally doped anorganic semiconductor materials, could be developed for SWNTs.