Construction of Hybrid SERS Chip Composed of Microstructured Si Metasurface and MoSxOy for Sensitive Molecule Detection

Abstract

Surface-enhanced Raman spectroscopy (SERS) is a powerful fingerprint spectroscopic technique capable of detecting trace molecules, which finds extensive application potential in diverse fields. The SERS substrates with excellent Raman signal enhancement, scalability in large-scale fabrication, and long-term stability is of significant scientific interest and practical value. Herein, we report a hybrid SERS substrate, namely tip-Si@MoSxOy, which integrates a periodic tip-patterned Si metasurface with MoSxOy semiconductor nanostructures, to develop novel noble-metal-free SERS substrate with sensitive molecule detection performance. The engineered periodic Si metasurface enables broadband matrix resonance by coupling with incident light, significanlty amplifying the localized near-field intensity at the inter-element nanogap regions. Theoretical calculations show that the maximum E-field enhancement can be up to 511 times. Meanwhile, the MoSxOy semiconductor leads to modification of the the polarization of probe molecules due to the charge-transfer interactions enabling chemical mechanism SERS effect. These combined effects make the detection of rhodamine 6G (R6G) at concentrations as low as 10-9 M and enhancement factor as high as 107. Moreover, the hybrid substrate exhibits superior antioxidation properties, eliminating the requirement of inert storage environments necessary for traditional noble-metal-based SERS substrates. Also, the MoSxOy semiconductor nanosructures are covalently bonded to the metasurface, ensuring structural stability without the need for post-transfer processes. Therefore, our work provides a novel approach to develop hybrid substrates with improved SERS performance, which is readily achievable and is expected to attract more research enthusiasm in the future.