Improved SERS activity of TiN microstructures by surface modification with Au

Abstract

Over the years, numerous outstanding research groups around the world have been working tirelessly on metallic SERS substrates. Although these efforts have led to the development of various sensors and pushed the field forward, today this line of research seems saturated and exhausted. In this work, we address this issue by exploring an emerging topic in recent literature: the fabrication of high-performance TiN SERS-active structures. TiN thin film was sputtered onto pyramidal Si microstructures. Spectroscopic ellipsometry measurements confirmed the plasmonic properties of the TiN material above its plasma wavelength of 515 nm. The Si-TiN surface was subsequently modified with an Au layer, which was then transformed into Au nanoparticles (Au NPs) during the Rapid Thermal Annealing process. The Si-TiN-AuNPs samples exhibited the highest extinction intensity, as well as the best SERS signal intensity for the model Raman reporter molecule. Further analysis of the SERS data showed that the presence of the Au thin film only moderately increased SERS activity, while Au NPs enhanced the SERS signal by one order of magnitude. Final Si-TiN-AuNPs platforms were successfully employed for the detection of vitamin B12, demonstrating a low limit of detection (8.57•10–8 M) along with excellent point-to-point repeatability. Graphical abstract