title: Tip-enhanced Raman spectroscopy and imaging: an apical illumination geometry.
abstract: Results are presented illustrating the use of tip-enhanced Raman spectroscopy (TERS) and imaging in a top-illumination geometry. A radially polarized beam is used to generate an electric field component in the direction of beam propagation, normal to the surface, resulting in a 5x increased enhancement compared to a linearly polarized beam. This multiplicative enhancement facilitates a discrimination of the near-field signal from the far-field Raman background. The top illumination configuration facilitates the application of TERS for investigating molecules on a variety of surfaces, such as Au, glass, and Si. The near-field Raman spectra of Si(100), rhodamine B, brilliant cresyl blue, and single wall carbon nanotubes are presented. Sufficient enhancement is obtained to permit a sub-diffraction-limited resolution Raman imaging of the surface distribution of large bundles of carbon nanotubes of various diameters.
authors.affiliation: Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Zachary D
authors.initials: ZD
authors.lastname: Schultz
authors.forename: Stephan J
authors.initials: SJ
authors.lastname: Stranick
authors.forename: Ira W
authors.initials: IW
authors.lastname: Levin
mesh_terms: D005898:Glass / Q000737:chemistry; D006046:Gold / Q000737:chemistry; D007834:Lasers; D008029:Lighting / Q000379:methods*; D018625:Microscopy, Atomic Force / Q000379:methods; D036103:Nanotechnology / Q000379:methods*; D037742:Nanotubes, Carbon / Q000737:chemistry; D010078:Oxazines / Q000737:chemistry; D010775:Photic Stimulation / Q000379:methods; D012235:Rhodamines / Q000737:chemistry; D012825:Silicon / Q000737:chemistry; D013059:Spectrum Analysis, Raman / Q000295:instrumentation / Q000379:methods*; D013379:Substrate Specificity
chemical_list: D037742:Nanotubes, Carbon; D010078:Oxazines; D012235:Rhodamines; C006797:Brilliant Cresyl Blue; D006046:Gold; C029773:rhodamine B; D012825:Silicon