Emerging applications of nano-Raman

Commercial Raman confocal microscopy can acquire images with a resolution down to 200 nm. Much effort has recently been devoted to improve upon this resolution and obtain chemical characterization of ultimately a single organic molecule. As an effort in this direction, we have developed an experimental configuration by combining the analytical power of Raman spectroscopy with the nanometer resolution of atomic force microscopy (AFM). Here, an AFM silicon nitride probe, coated with a 40 nm silver layer, was used to significantly enhance the Raman signal by laser excitation of surface plasmons in the tip coating. Experimental results indicate a local surface enhanced Raman scattering (SERS) increase of 10 ⁵. Lateral scanning of the sample and collecting the SERS signal allows for a 2D image of the chemical identity of the probed sample simultaneous with its topography as measured by the AFM. Also, the ratio of Stokes to anti-Stokes can be used to obtain an instantaneous and absolute map of the local temperature across the sample.