Surface-enhanced and tip-enhanced Raman scattering.

	In this lecture we will introduce the basic notion of the surface plasmon excitation in metals, and show how it can lead to a strong electromagnetic (EM) field at the surface of nan-structured metal structures. This strong field can in turn be used to enhance the Raman scattering from molecules. This is surface-enhanced Raman scattering (SERS). But in addition to the EM mechanism molecules at metal surfaces may enhance their Raman spectra by a chemical mechanism involving charge transfer, which we will also discuss. Finally, tip-enhanced Raman scattering will be introduced. This is a variant of SERS in which a sharp tip is scanned over a surface to generate a near-field image based on detection of Raman photons.