Hydrophobic mediated growth of galvanic-nanobuds from germanium nanowires for a highly tunable SERS substrate

Abstract

Potential applications of SERS substrates lie in their ability to be of large area and reproducible with a high shelf life. Sensitivity, however, is a consequence of tunability of the substrate for the specific laser in use. These criteria are addressed using the reported SERS substrate with a galvanic-nanobud architecture through germanium nanowires. Dense germanium nanowires have been fabricated using a plasma enhanced chemical vapour deposition technique. Silver nanostructures were grown on the nanowires by hydrophobic interactions between the nanowire substrate and AgNO₃ solution. A measurement method has been proposed to obtain the temporal information on nanobud formation, thereby optimizing the surface enhanced Raman scattered signal from such substrates in real-time for any wavelength. This eliminates the usage of computationally expensive numerical tools or additional characterization techniques to locate plasmon resonances of the substrates. The proposed optimization technique was further verified by cathodoluminescence measurements. Cathodoluminescence hotspot maps revealed the nature of the hotspots of the substrates optimized for 514 nm and 785 nm. Enhanced sensitivity and tunability of the substrates in the red spectral region present their plausible future application in biological domains.