Metallic film-coated porous silicon (PSi) has been reported as a lucrative surface-enhanced\nRaman scattering (SERS) substrate. The solution-based fabrication process is facile and easy; however,\nit requires additional reducing agent and extra chemical treatment, as well as hinders the suitability\nas a reproducible SERS substrate due to irregular hot spot generation via irregular deposition of\nmetallic nanocrystallites. To address this issue, we report a unique one-step electronic beam (e-beam)\nphysical vapor deposition (PVD) method to fabricate a consistent layer of gold (Au) nanofilm on PSi.\nMoreover, to achieve the best output as a SERS substrate, PSi prepared by electrochemical etching\nwas used as template to generate an Au layer of irregular surface, offering the surface roughness\nfeature of the PSiâ??Au thin film. Furthermore, to investigate the etching role and Au film thickness,\nAu-nanocrystallites of varying thickness (5, 7, and 10 nm) showing discrete surface morphology\nwere characterized and evaluated for SERS effect using Rhodamine 6G (R6G). The SERS signal of\nR6G adsorbed on PSiâ??Au thin film showed a marked enhancement, around three-fold enhancement\nfactor (EF), than the Siâ??Au thin film. The optimal SERS output was obtained for PSiâ??Au substrate of\n7 nm Au film thickness. This study thus indicates that the SERS enhancement relies on the Au film\nthickness and the roughness feature of the PSiâ??Au substrate.
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