ROUGH SILVER FILMS STUDIED BY SURFACE-ENHANCED RAMAN-SPECTROSCOPY ANDLOW-TEMPERATURE SCANNING-TUNNELING-MICROSCOPY

The surface topography of Ag films and surface enhanced Raman scatteri ng (SERS) from benzene on Ag films have been simultaneously recorded. The Ag films were formed by vacuum deposition at temperatures ranging from 100 K to 500 K. Analysis of scanning tunnelling microscopy (STM) images shows that films formed below 250 K are fractal structures with Hausdorff-Besicovitch dimension 2.55 < D < 2.72, while for those form ed above 250 K, D approximate to 2. The lower temperature, rough films exhibit strong surface enhanced Raman scattering but the higher tempe rature, smooth films do not. We consider the consequences of fractal c haracter and the possible correlation between this and the SERS activi ty of these films.