Controlled Formation of Isolated Silver Islands for Surface-Enhanced Raman Scattering

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Abstract
Rough silver surfaces enhance the Raman scattering of adsorbed molecules by many orders of magnitude. The size, shape, and surroundings of the metal particles greatly influence the resulting Raman intensities. With the controlled formation of well-separated silver islands, direct investigation of the local origin of the Raman enhancement is greatly facilitated. We summarize the effects of experimental parameters during and after vapor deposition of silver on the resulting surface morphology. With the selection of suitable experimental conditions, particle sizes and shapes, as well as the interparticle distances, can be controlled so that well-separated silver islands are formed that still show high Raman enhancement. The surfaces were characterized morphologically by means of atomic force microscopy (AFM) and scanning electron microscopy (SEM). Optical characterization was carried out by using ultraviolet-visible and Raman spectroscopy.