Near-field optics and spectroscopy for molecular nano-imaging.

Application of near-field optical microscopy with a sharp metallic probe to Raman spectroscopy brings microanalysis of materials to their nano-identification and imaging. The local plasmon polariton excitation on the probe tip results in the localization and amplification of the optical field at the vicinity of the tip. The tip-enhanced near-field Raman spectroscopy has analyzed DNA base molecules and single-walled carbon nanotubes (SWNTs) with the nanometric spatial resolution and sufficient sensitivity. Combined with tip pressurization and nonlinear effects, the tip-enhanced near-field Raman spectroscopy gives additional spectral information or improves the spatial resolution and sensitivity. This article introduces the recent progresses on the tip-enhanced near-field Raman spectroscopy and imaging.