Near-Field Raman Spectroscopy with Aperture Tips

Abstract

In this paper, we review nano-Raman techniques based on aperture scanning near-field optical microscopy (SNOM). Fundamentals of SNOM and aperture-tip-based near-field Raman spectroscopy and their applications in key technical issues, including Raman signal intensity and collection time, are introduced. Recent advances in the tip design are discussed, and applications of the aperture-SNOM-based nano-Raman technique are presented. We attempt to identify the most pressing open questions in this field. We believe that, by improving the power transmission efficiency and combining the local field enhancing technique with the tip-enhanced spectroscopy, the performance of aperture-SNOM can be significantly improved. Its nanometer-scale excitation volume and the consequent low background make the aperture-tip technique feasible for many important samples that cannot be measured by other optical nanospectroscopies.

A Review of Three-Dimensional Scanning Near-Field Optical Microscopy (3D-SNOM) and Its Applications in Nanoscale Light Management

“…2017, 7, 973 5 of 25 different spectroscopy techniques to be implemented alongside SNOM systems to allow spectroscopy and imaging at sub-wavelength resolution. Techniques with which aperture-type SNOM has been coupled include Fourier-transform infrared spectroscopy (FTIR) [8], fluorescence [16], and Raman spectroscopy [17,18].…”

“…More recently surface enhanced Raman scattering (SERS) has demonstrated label-free single molecule resolution [18,27]. Coupling Raman spectroscopy with c-SNOM systems overcomes the limitations of the other sensitivity enhancing techniques and can achieve nanoscale-SNOM enhanced Raman spectroscopy [17]. Nano Raman is a c-SNOM technique making use of aperture type tips placed within the near-field of a sample to be imaged.…”

“…Nano Raman is a c-SNOM technique making use of aperture type tips placed within the near-field of a sample to be imaged. This technique has been used to study inorganic crystals, polymer thin films, liquid-liquid interfaces at the nanoscale, as well as mapping of single molecules on surfaces [17] an investigation that is not possible with conventional far-field Raman.…”

Gap plasmon-enhanced photoluminescence of monolayer MoS 2 in hybrid nanostructure

“…[17] To compensate for this, different kinds of approaches to enhancing the emission of monolayer MoS 2 are proposed, including chemical doping, [18] polymeric nano-spacing, [19] defect engineering, [20] and using surface plasmon polaritons (SPPs). [21][22][23] Among these methods, SPPs which have been widely utilized for strong light-matter interaction applications such as photoluminescence enhancement [24][25][26][27][28][29][30][31] and surface enhanced Raman scattering, [32,33] could induce hot electrons and cause the phase transition of MoS 2 , [34][35][36] resulting in the enhanced PL in a metal-MoS 2 coupled system. [37][38][39][40] For example, gap plasmons have been used in different areas, such as enhancing local chemical reactions, [41] dielectric gratings, [42,43] plasmonic nanocavities, [44][45][46] and PL of single layer WSe 2 .…”

A fully automated dual-tip scanning near-field optical microscope for localized optical excitation and detection in the visible and near-infrared

“…Scanning near-field optical microscopy (SNOM) is an invaluable tool to investigate optical phenomena within the near-field region of nano-photonic structures. Since its first realization, 1,2 SNOM has been a measurement tool in various research areas such as plasmonics 3,4 , photonic crystals [5][6][7] , surface-enhanced Raman spectroscopy 8,9 and photovoltaics 10,11 . The tip a) Electronic mail: najmeh.abbasirad@uni-jena.de in a conventional aperture SNOM often serves for either near-field excitation or detection, which can be more localized than allowed by the diffraction limit.…”