Scanning probe Raman spectroscopy with single molecule sensitivity

By: C. C. Neacsu, J. Dreyer, N. Behr, and M. B. Raschke

Physical Review B 73, 193403 (2006)

Single-molecule vibrational Raman spectroscopy of malachite green adsorbed on planar metal surfaces is achieved by means of optical local-field enhancement provided by a scanning nanoscopic metallic tip. The single-molecule signature is evident from spectral diffusion and a discretization of Raman peak intensities. The optical tip-sample coupling gives rise to a localization of the response down to a sub-10 nm length scale and a Raman enhancement up to ∼5 × 109. This combines vibrational spectroscopy with high resolution scanningprobe microscopy for ultrasensitive in situ analysis of individual molecules.