6:00 PM - 6:15 PM
[19p-S622-16] Metal Grains of Plasmonic Nanoprobe in Tip-Enhanced Raman Microscopy
Keywords:Tip-enhancement,Metallic probe,grain structure
Tip-enhanced Raman spectroscopy (TERS) is recently becoming indispensable as a nano-imaging technique for analyzing advanced nano-devices and nano-materials because it allows strong enhancement of weak Raman signals from the nanometric volume of a sample [S. Kawata, et al. Nat. Photon. 3, 388 (2009).]. However, consistent enhancement in TERS is still an issue, and scientists have been struggling to fabricate good tips for a reliable, strong and reproducible enhancement. The design of the metallic nanotip, which acts as an optical antenna for enhancing Raman scattering, is one of the most important parameter to control the enhancement. Many scientists have realized this fact and have discussed about the need for investigating suitable tip structures for improved control on the enhancement in TERS, but unfortunately no one has yet reported a systematic study on this very important aspect of TERS.
Here, we present a study on the metal grains attached to the tip surface for producing higher and much consistent enhancement in TERS and discuss why tips with granular surface are much better than tips with smooth surfaces [A. Taguchi, et al., Nanoscale 7, 17424 (2015).]. Our study shows that the plasmonic enhancement strongly depends on the number of grains and on their separations. We found through simulations that multiple grains arranged closely but discretely on a dielectric probe act as an efficient plasmonic antenna and that enhancement in TERS attains a maximum value for an optimized number of grains. The number of grains and the nano-gap between them are crucial to achieve a stronger, tunable and reproducible enhancement. This promising result, which we also demonstrate and prove by experiments, will bring TERS to a new level where it can be utilized in experiments with more confidence for a stronger reproducible enhancement even for those nano-sized samples that have extremely weak Raman scattering.
Here, we present a study on the metal grains attached to the tip surface for producing higher and much consistent enhancement in TERS and discuss why tips with granular surface are much better than tips with smooth surfaces [A. Taguchi, et al., Nanoscale 7, 17424 (2015).]. Our study shows that the plasmonic enhancement strongly depends on the number of grains and on their separations. We found through simulations that multiple grains arranged closely but discretely on a dielectric probe act as an efficient plasmonic antenna and that enhancement in TERS attains a maximum value for an optimized number of grains. The number of grains and the nano-gap between them are crucial to achieve a stronger, tunable and reproducible enhancement. This promising result, which we also demonstrate and prove by experiments, will bring TERS to a new level where it can be utilized in experiments with more confidence for a stronger reproducible enhancement even for those nano-sized samples that have extremely weak Raman scattering.