제 목 : Nanoimaging through tip-enhanced Raman spectroscopy

강 사 : Prof. Prabhat Verma (Osaka University, Japan)

시 간 : 2019년 3월 15일 금요일 오후 3시 30분

장 소 : 제1신공학관 301동 101호

Abstract:

Nature has many interesting things to offer - one of them is the fact that visible light (from near-UV to near-IR) contains an energy that is comparable to the electronic or vibrational energies of most of the naturally existing materials that we interact with in our day-to-day lives. Visible light can therefore interact directly with the electronic or vibronic system of a sample, and can extract rich information related to the intrinsic properties of the sample. This is probably one of the most important reasons why optical techniques, such as Raman spectroscopy, have always been convenient tools for analyzing and imaging various materials. However, Raman microscopy in its conventional form is not suitable for analyzing and imaging nanomaterials due to two major reasons. First, the poor spatial resolution restricted by the diffraction limits of the probing light makes it impossible to analyze materials smaller than about half of the wavelength, which is about 200~400 nm for visible light. And second, due to the extremely small volume of nanomaterials, Raman scattering intensity is extremely weak for such samples. However, when conventional Raman microscopy is combined with plasmonics and the near-field techniques, it achieves new and exciting features as it goes beyond the conventional limits of optical microscopy, in terms of both the spatial resolution and scattering intensity. This can be done by utilizing the technique of tip-enhanced Raman spectroscopy (TERS), which is based on plasmonic enhancement and confinement of light field near the apex of a sharp metallic nanotip for characterizing and imaging samples at nanoscale. This plasmonics-based technique allows us to have a spatial resolution below 10 nm in optical nanoimaging.

Here, with the help of several example of TERS measurements, we will show how such a high spatial resolution in TERS is obtained and how it can be useful in various applications. We will also discuss some new approaches in TERS, which strengthen this technique further.

Biography:

Prabhat Verma is a Professor at the Department of Applied Physics of Osaka University in Japan, where he leads a research team on Nanospectroscopy. He is also the Chair of the JSPS Core-to-Core Program at Osaka University and a Director of the Photonics Division of the Japan Society of Applied Physics. He received his Master from IIT Kanpur and Doctorate from IIT Delhi in India, after which he went for his post-doctoral research in Germany and in Japan. Prof. Verma is one of the leaders in the field of tip-enhanced Raman spectroscopy (TERS). He has co-authored more than 130 peer-reviewed papers in high ranked journals, has written several book chapters, review articles and has delivered more than 60 Plenary and Invited talks in various international conferences. He is actively involved with international societies, and has organized more than 25 international conferences so far.