Aluminum-Induced Surface-Enhanced Raman Scattering in Ti-Al-Ti Sandwich Multilayer Thin Films

A series of Ti-Al-Ti sandwich thin films with different Al layer thicknesses was prepared via magnetron sputtering. The Al layer facilitated Ti-Al metal coupling within the films, which significantly strengthened the localized surface plasmon resonance (LSPR) and obtained more “hot-spots”, ultimately leading to a remarkable enhancement of the localized electric field. The LSPR effectively promoted charge transfer between probe molecules and the Ti-Al-Ti sandwich thin film. Raman scattering intensity was jointly governed by chemical and electromagnetic enhancement mechanisms. When used as a surface-enhanced Raman scattering (SERS) substrate for methylene blue (MB) detection, the sandwich-structured films achieved a Raman enhancement factor of 3.27 × 106, approximately twice that of single-layer silver thin films. The substrate exhibited a low MB detection limit for MB of 10−8 M and excellent stability. Additionally, the relative standard deviation of main characteristic peak intensities across different positions is consistently below 6%, indicating superior uniformity and reproducibility. Experimental results are in good agreement with FDTD simulation outcomes.