Tip-Enhanced Raman Imaging and Nanospectroscopy: Sensitivity, Symmetry, and Selection Rules

Reviews and Highlights	Quantum Science	Molecular and Soft-matter	Ultrafast Nano-optics and Nanophotonics	Mineralogy and Geochemistry

Catalin C. Neacsu, Samuel Berweger, and Markus B. Raschke
Nanobiotechnology  3, 172 (2007).
DOI PDF

The fundamental mechanisms of tip-enhanced 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.