Annealing of Glass-Deposited Silver Island Films Lead to Creation of Regular Sers-Active Surfaces. Comparative Scanning Tunnel Microscopy and Sers Study

Abstract

Preparation of well-defined, stable SERS substrates with a uniform roughness on the scale of 3 to 100 nm has proven to be a critical step in the effect applications. Au, Ag and Cu colloids, electrodes and microelectrodes, island films, nuclear pores, and self-assembled metal colloid monolayers (1,2), all of them provide millionfold enhancements in Raman scattering. Theory predicts that the local electromagnetic field is enhanced as a result of propagation of surface plasmon resonances in the metal at appropriate excitation wavelengths. The relationship between scattering intensity and the distance of the adsorbate from the surface, as well as the overall enhancement, is governed by the particle shape and radius of curvature. Hence, an increase in SERS sensitivity can be attained by preparing substrates with optimal surface morphology.