AVS 45th International Symposium
    Surface Science Division Monday Sessions
       Session SS1+NS-MoA

Paper SS1+NS-MoA7
Characterization of Near-Field Probes for Enhanced Raman Spectroscopy

Monday, November 2, 1998, 4:00 pm, Room 308

Session: Novel Surface Probes
Presenter: C.E. Jordan, National Institute of Standards and Technology
Authors: C.E. Jordan, National Institute of Standards and Technology
L.J. Richter, National Institute of Standards and Technology
R.R. Cavanagh, National Institute of Standards and Technology
S.J. Stranick, National Institute of Standards and Technology
Correspondent: Click to Email
Near-field Raman spectroscopy can potentially obtain chemical specificity with the subwavelength resolution of a near-field scanning optical microscope (NSOM). Signals from a single crystal diamond sample have been evaluated to assess the limits of this technique. Three different types of illumination mode fiber optic probes have been used in the near-field Raman experiments: an uncoated probe; a probe coated with a smooth layer of aluminum which has an aperture that is less than 100 nm in diameter; and a probe coated with a smooth layer of aluminum and then overcoated with a rough layer of silver. In order to discriminate between the enhanced contribution to the Raman signal observed in the near-field of the probe and bulk scattering, the Raman intensity from each type of probe is measured as a function of the probe sample separation. Very little change in the Raman intensity is observed as a function of probe sample separation when an uncoated fiber optic probe is used. For an optical probe coated with a smooth layer of aluminum the Raman intensity is about a factor of seven higher when the sample is in the near-field of the probe compared to the intensity measured when the sample is farther than 100 nm away from the probe. Probes that are coated with a rough silver film show a greater enhancement in the near-field Raman intensity than is observed for probes coated only with aluminum.