Tip-enhanced Raman imaging and nanospectroscopy: Sensitivity, symmetry, and selection rules

By: C. C. Neacsu, S. Berweger, and M. B. Raschke

Nanobiotechnology 3, 172 (2007)

The fundamental mechanisms of tipenhanced Raman spectroscopy (TERS) have been investigated, including the role of the plasmonic excitation of the metallic tips, the nature of the optical tip–sample coupling, and the resulting local-field enhancement and confinement responsible for ultrahigh resolution imaging down to just several nanometers. Criteria for the distinction of near-field signature from far-field imaging artifacts are addressed. TERS results of molecules are presented. With enhancement factors as high as 109 , single-molecule spectroscopy is demonstrated. Spatially resolved vibrational mapping of crystalline nanostructures and determination of crystallographic orientation and domains is discussed making use of the symmetry properties of the tip scattering response and the intrinsic Raman selection rules.