SPUTTERED GOLD-FILMS FOR SURFACE-ENHANCED RAMAN-SCATTERING

Sputtered gold films in a pure form or as nanocomposites in silica or silicon nitride were screened for surface-enhanced Raman scattering (S ERS) activity using Rhodamine 6G as a probe. The films were prepared b y sputtering pure gold or solidified Au-Si alloys in plasmas generated in a de glow discharge apparatus. The plasmas were produced with argo n, nitrogen, or argon-oxygen as the sputtering gas to directly deposit gold films or in the latter case a Sold oxide intermediate. The alloy s produce nanocomposite films in a silicon nitride or silica matrix de pending on the plasma gas. SERS activity was detected in some of the f ilms thus leading to a search for the critical parameters that control led this phenomenon. The films were characterized by profilometry, x-r ay diffraction, and atomic force microscopy. SERS activity was found t o be correlated to crystallite size in the 10-25 nm range and to rough ness larger than 15 nm, and it was independent of film thickness. Sput tered gold films, particularly those containing the gold as a nanocomp osite in silica are attractive media for SERS because of excellent adh erence, ruggedness, and simplicity in preparation. (C) 1997 American V acuum Society.