Near-field Raman spectroscopy using a sharp metal tip

Near-field Raman spectroscopy with a spatial resolution of 20 nm is demonstrated by raster scanning a sharp metal tip over the sample surface. The method is used to image vibrational modes of single-walled carbon nanotubes. By combining optical and topographical signals rendered by the single-walled carbon nanotubes, we can separate near-field and far-field contributions and quantify the observed Raman enhancement factors.