Abstract
Metallic film-coated porous silicon (PSi) has been reported as a lucrative surface-enhanced Raman scattering (SERS) substrate. The solution-based fabrication process is facile and easy; however, it requires additional reducing agent and extra chemical treatment, as well as hinders the suitability as a reproducible SERS substrate due to irregular hot spot generation via irregular deposition of metallic nanocrystallites. To address this issue, we report a unique one-step electronic beam (e-beam) physical vapor deposition (PVD) method to fabricate a consistent layer of gold (Au) nanofilm on PSi. Moreover, to achieve the best output as a SERS substrate, PSi prepared by electrochemical etching was used as template to generate an Au layer of irregular surface, offering the surface roughness feature of the PSi–Au thin film. Furthermore, to investigate the etching role and Au film thickness, Au-nanocrystallites of varying thickness (5, 7, and 10 nm) showing discrete surface morphology were characterized and evaluated for SERS effect using Rhodamine 6G (R6G). The SERS signal of R6G adsorbed on PSi–Au thin film showed a marked enhancement, around three-fold enhancement factor (EF), than the Si–Au thin film. The optimal SERS output was obtained for PSi–Au substrate of 7 nm Au film thickness. This study thus indicates that the SERS enhancement relies on the Au film thickness and the roughness feature of the PSi–Au substrate.
Highlights
Surface-enhanced Raman scattering (SERS) is a sophisticated analytical technique to detect minute amounts of target analyte, even down to a single molecule, by providing molecule-specific vibrational spectra
Prepared porous silicon (PSi) is metastable and reactive due to the presence of hydrogen-terminated Si–Hx (x = 1, 2, 3) on the external layer of the PSi, vulnerable to react with the impurities present in the electrolytes used in etching process or from the air of the material storage environment [21]
Large numbers of Au nuclei are generated on the PSi surface, which facilitate the formation of Au nanocrystallites on roughened PSi surface at a higher rate in comparison to the conventional flat Si surface
Summary
Surface-enhanced Raman scattering (SERS) is a sophisticated analytical technique to detect minute amounts of target analyte, even down to a single molecule, by providing molecule-specific vibrational spectra. The SERS phenomenon is attributed to two effects: Electromagnetic and chemical enhancement mechanisms. Electromagnetic enhancement is due to the enhanced electromagnetic fields localized on or in the immediate vicinity of a nanostructured metallic surface generated by the excitation of localized surface plasmons. Chemical enhancement results from the charge transfer between a metal substrate and the adsorbed molecule onto its surface [1,2,3].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
