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Gap-Plasmon Tip-Enhanced Raman Scattering of Semiconductor Nanostructures

Subject Area Experimental Condensed Matter Physics
Term from 2019 to 2023
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 410250059
 
Final Report Year 2025

Final Report Abstract

This project aimed at investigating gap-plasmon induced enhancement of Raman scattering by semiconductor nanocrystals in the vicinity of metallic nanostructures with nanometric spatial resolution. We also studied local optical phenomena of low-dimensional materials revealing some novel aspects of these systems. The key concept of this project was to utilize the localized surface plasmon resonance (LSPR) of metal nanostructures to induce resonance phenomena in adjacent low dimensional systems and to study the subsequent effects by tipenhanced Raman scattering (TERS) and surface-enhanced Raman scattering (SERS). Semiconducting nanocrystals or quantum dots (QDs) composed of CdSe and CdS with variable sizes were the main model systems studied in this project. They were deposited by the Langmuir-Blodgett technique onto arrays of gold nanostructures. To understand the plasmonic effects thoroughly, especially the impact of LSPR, we employed numerical simulation tools. This helped us to design our experiments in an efficient manner. With this detailed approach, it was possible to study local phonon properties of semiconducting nanostructures with a spatial resolution as low as approximately 2 nm. We also studied surface-enhanced photoluminescence from such nanostructures, which in comparison to SERS is less efficient due to non-radiative decay channels. Beyond the scope of the original project the (nano-) spectroscopic approach was applied to a range of other semiconductor systems. The results of this project reveal some new aspects of low-dimensional semiconductors, which have a significant impact on both fundamental understanding and towards development of technological applications.

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