Oxygen Vacancies Enhance SERS Performance of Tungsten-Doped Vanadium Dioxide Nanoparticles

Abstract

Surface-enhanced Raman spectroscopy (SERS) is a powerful spectroscopic identification technique for analyzing chemical and biological analytes. Semiconductors are important materials that can expand the scope of SERS applications. However, the low SERS enhancements limit the application of semiconductor substrates. In this work, a new defect engineering approach is used, i.e., combining two types of defects, to enhance SERS performance by preparing of oxygen-vacancy-tunable W-doped VO₂ substrate. In this design, two types of defects effect in synergy to improve the SERS performance of rhodamine 6G (R6G). The oxygen vacancy concentration in W-doped VO₂ is adjusted through thermal annealing. This substrate achieves a detection limit of 1 × 10⁻⁷ m for R6G and an enhancement factor (EF) of 1.39 × 10⁶, comparable to noble metals. XPS and DFT analysis reveal that SERS enhancement can be attributed to the high density of electronic states associated with W-doping and oxygen vacancies. Additionally, W-doping increases the free electron concentration in the oxygen-deficient W-VO₂, which enhances the charge transfer (CT) between the substrate and R6G, leading to significant amplification of Raman signal. This work provides a defect-engineering approach based on the synergistic effect of oxygen vacancies and tungsten doping for enhancing the SERS performance of metal oxide semiconductor-based substrates.