INFLUENCE OF VAPOR-DEPOSITION PARAMETERS ON SERS ACTIVE AG FILM MORPHOLOGY AND OPTICAL-PROPERTIES

The magnitude of surface enhancement from thin metal films is known to be critically dependent on film morphology. In order to establish the best methodology for generating reproducible vapor-deposited thin metal films, the influence of a wide range of experimental deposition variables on Ag film morphology and optical properties was investigated by use of a combination of optical absorption, atomic force microscopy, and surface-enhanced Raman spectroscopy(SERS). The specific variables examined include quality of glass substrate, glass pretreatment, deposition rate, deposition temperature, deposition geometry, and postdeposition annealing. The type of glass substrate (''white'' glass vs ''float'' glass) was found to be an important factor for producing high-quality Ag films. However, glass pretreatment appeared to be relatively unimportant. Deposition rate and geometry are critical parameters in generating reproducible films. In addition, mild elevation of substrate temperature (Delta 20 degrees C) strongly affects film characteristics. A detailed analysis of SERS reproducibility, based on these variables, is reported.