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Observation and Analysis of Blinking Surface-enhanced Raman Scattering
Published on: January 11, 2018
Light depolarization induced by metallic tips in apertureless near-field optical microscopy and tip-enhanced
P G Gucciardi1, M Lopes, R Déturche
1CNR-Istituto per i Processi Chimico-Fisici, sezione Messina, Salita Sperone, Contrada Papardo, I-98158 Faro Superiore, Messina, Italy.
Nanotechnology
|July 7, 2011
Summary
Light scattering from sharp tips in near-field microscopy causes depolarization. This effect, measured experimentally and confirmed theoretically, enables the observation of forbidden Raman modes in silicon crystals using tip-enhanced Raman spectroscopy (TERS).
Area of Science:
- Optics and Photonics
- Materials Science
- Spectroscopy
Background:
- Apertureless near-field optical microscopy relies on sharp tips for high-resolution imaging.
- Understanding light-tip interactions, including polarization effects, is crucial for advanced microscopy techniques.
- Depolarization of scattered light by microscopy tips can influence experimental outcomes.
Purpose of the Study:
- To investigate the depolarization effects of light scattered by sharp tips used in apertureless near-field optical microscopy.
- To quantify depolarization factors for dielectric and metal-coated tips.
- To explore the impact of depolarization on tip-enhanced Raman spectroscopy (TERS) experiments.
Main Methods:
- Experimental measurement of depolarization factors for various tip types (dielectric and metal-coated).
- Finite element method (FEM) calculations to model near-field depolarization.
- Application of polarized tip-enhanced Raman spectroscopy (TERS) to silicon crystals.
Main Results:
- Depolarization factors ranging from 5% to 30% were measured, dependent on incident polarization and tip geometry.
- Theoretical calculations using FEM showed a near-field depolarization factor close to 10%.
- Observed the emergence of forbidden Raman modes in silicon crystals due to depolarization in TERS experiments.
Conclusions:
- Depolarization is a significant effect in light scattering from microscopy tips.
- Experimental and theoretical results for depolarization factors are in good agreement.
- Depolarization in TERS enables the detection of previously unobserved Raman scattering phenomena in materials like silicon.
