Enhanced Infrared Absorption of Thiourea Adsorbed on a Rough Silver Surface

Thin films of different thicknesses, made by thiourea molecules deposited on a flat silver surface roughened by treatment with chemical etching solutions, have been studied by infrared reflectionabsorption spectroscopy. A significant enhancement (of the order of several hundreds) of the infrared absorption cross-section of the thiourea molecules has been found. In agreement with the surfaceenhanced Raman spectroscopy results for the same films, it has been found that the main enhancement is associated with the first layer of thiourea molecules chemisorbed on the silver surface.