Tip-enhanced Raman scattering unraveling molecular interactions in individual carbon nanotube systems

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Devices on the nanometer scale drive intensive research today and will gain even more influence in the future for both the field of nanoelectronics and the field of biochemistry and medicine. Tip-enhanced Raman scattering (TERS) is an ideal method to understand the functionality of such devices in depth, since it combines microscopic with spectroscopic information at nanometer scale spatial resolution. This project is going to unfold the full potential of TERS to characterize and study the structure of nanoscale devices. The model systems most suitable for this investigation are functionalized carbon nanotubes (CNTs). On the one hand, they show a high potential for applications as nanosensors or single molecule detectors. On the other hand, Raman spectroscopy on CNTs is well understood, and TERS on CNTs has been demonstrated. However, knowledge about interactions between CNTs and other molecules grafted to them is still limited. We will study such interactions in particular with magnetic molecules, correlating high-resolution transmission electron microscopy with Raman spectroscopy and TERS on the same CNT and using the full spectral information. Energy filtered electron energy loss spectroscopy provides element selectivity and will be used to determine the spatial resolution as well as the chemical selectivity of TERS. The resonance effect in Raman spectroscopy gives insight into the electronic states of the material. Thus, studying the influence of the resonance effect on the TERS spectra of functionalized CNTs will lead to an understanding of the influence of the functionalization on the electronic properties of the CNT, e.g., by doping or creation of defects. The final goal of the project is then to combine the results to select those sites on functionalized CNTs with the most promising and the most interesting properties for transport devices.