Near-field scanning optical microscopy incorporating Raman scattering for vibrational mode contrast

Near-field scanning optical microscopy offers the ability to combine a broa d range of spectral contrast features with spatial resolution that is an or der of magnitude better than that set by the diffraction limit of the probe light. For many chemical problems, it would be advantageous to use vibrati onal spectroscopy as the optical contrast mechanism. This realization of op tical contrast would enable nanometer scale identification of changes in ch emical composition as a function of position and/or time. A leading candida te for this chemical imaging approach is Raman scattering. Ln this paper a comparison of transmitted and reflected signals will be made as a function of probe-to-sample separation, thus discriminating between bulk and near-fi eld contributions of the detected signal. Also, the decay of the Raman inte nsity as a function of probe-to-sample separation will be used to show the sensitivity to local field effects. (C) 1999 Elsevier Science B.V. All righ ts reserved.