Surface-enhanced Raman scattering from molecules in tunnel junctions

Surface-enhanced Raman scattering from molecular monolayers adsorbed at the aluminum oxide-Ag interface of tunnel junctions has been studied as a function of the junction parameters and surface roughness. The surface-plasmon-polariton contribution to surface-enhanced Raman scattering from this system is quantitatively demonstrated in experiments on samples fabricated on holographic diffraction gratings. The existence of a short-range contribution to the surface-enhanced Raman effect is also shown and compared with the predictions of the modulated surface dipole mechanism of Jha, Kirtley, and Tsang.