TiN Nanorods as Effective Substrate for Surface-Enhanced Raman Scattering

Owing to its well-known chemical stability, thermal stability, and complementary metal-oxide-semiconductor process compatibility, titanium nitride (TiN) has recently been demonstrated as an excellent alternative plasmonic material for noble metals. However, the lack of systematic studies on its electromagnetic enhancement mechanism has placed an obstacle on the realization of localized surface plasmon resonance (LSPR) using this unique TiN substrate for surface-enhanced Raman scattering (SERS) applications. In this study, we prepared TiN nanorods using scalable high-throughput oblique angle deposition technique and optimized its SERS effect by improving the crystallinity via annealing. Remarkably, we directly observed the LSPR of the TiN nanorods by near-field optical image and revealed its corresponding LSPR mode using finite element analysis. The two resonance peaks in both near and far field exhibit a red shift when increasing the length of the TiN nanorods, which can be ascribed to the increase of electron cloud oscillation distance with the same electron mobility. Therefore, our systematical investigations have clarified the critical influences of both the crystallinity and the length on the LSPR of TiN nanorods, thus providing urgently required guidance for TiN SERS substrate design, as well as LSPR device development.