Near-Field Nano-Raman Microscopy

The future of Raman microspectroscopy is probably imaging and optical near-field nano-Raman spectroscopy [529], cfr. Chp. 5.5.2. While conventional laser Raman spectroscopy samples 10 g (mm ), /zRS handles 10 g (nm ) and near-field Raman spectroscopy 10 g (nm ). Mobile Raman microscopy (MRM) allows in situ Raman analysis [530]. One can expect further developments in the field of NIR multichannel Raman spectroscopy with the advent of 2D array detectors offering extended response in the NIR. With these 2D sensors it wiU become possible to apply in the NIR region the powerful techniques already developed in the visible, such as confocal line imaging techniques or multisite remote analysis with optical fibres. 

Near-field microscopy is another usefiil application of DUV plasmonics. In this method, scanning probe microscopy was combined with optical microscopy. A nano-sized probe was coated with plasmonic materials to localize the incident light at its apex. The spectroscopic signal was obtained primarily at the probe apex, realizing a nanoscale imaging resolution. Recently, near-field DUV Raman scattering with an aluminum tip has been reported with an enhancement factor of 1,300... 

A nano-light-source generated on the metallic nano-tip induces a variety of optical phenomena in a nano-volume. Hence, nano-analysis, nano-identification and nanoimaging are achieved by combining the near-field technique with many kinds of spectroscopy. The use of a metallic nano-tip applied to nanoscale spectroscopy, for example, Raman spectroscopy [9], two-photon fluorescence spectroscopy [13] and infrared absorption spectroscopy [14], was reported in 1999. We have incorporated Raman spectroscopy with tip-enhanced near-field microscopy for the direct observation of molecules. In this section, we will give a brief introduction to Raman spectroscopy and demonstrate our experimental nano-Raman spectroscopy and imaging results. Furthermore, we will describe the improvement of spatial resolution... 

With regard to the confinement and enhancement ability of a metallic nano-tip, we have proposed near-field Raman microscopy using a metallic nano-tip [9]. The metallic nano-tip is able to enhance not only the illuminating light but also the Raman scattered light [9, 15, 16]. Figure 2.5 illustrates our nano-Raman microscope that mainly comprises an inverted microscope for illumination and collection of Raman... 

Ichimura T, Hayazawa N, Hashimoto M, Inouye Y, Kawata S (2004) Application of tip-enhanced microscopy for nonlinear Raman spectroscopy. Appl Phys Lett 84 1768 Ichimura T, Hayazawa N, Hashimoto M, Inouye Y, Kawata S (2004) Tip-enhanced coherent anti-stokes raman scattering for vibrational nanoimaging. Phys Rev Lett 92 220801 Tanaka S, Maeda Y, Cai L, Tabata H, Kawai T (2001) Application of tip-enhanced microscopy for nonlinear Raman spectroscopy. Jpn J Appl Phys 40 4217 Watanabe H, Ishida Y, Hayazawa N, Inouye Y, Kawata S (2004) Tip-enhanced near-field Raman analysis of tip-pressurized adenine molecule. Phys Rev B 69 155418 Yano T, Verma P, Saito Y, Ichimura T, Kawata S (2009) Pressure-assisted tip-enhanced Raman imaging at a resolution of a few nanometres. Nature Photon 3 473 Yano T, Inouye Y, Kawata S (2006) Nanoscale uniaxial pressure effect of a carbon nanotube bundle on tip-enhanced near-field Raman spectra. Nano Lett 6 1269 Downes A, Salter D, Elfick A (2006) Heating effects in tip-enhanced optical microscopy. Opt Exp 14 5216... 

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