Defect-induced plasmon resonance of SERS-active MoO2-x/Mo composite films by pulsed laser irradiation

A series of defective MoO2-x/Mo films were prepared by laser modification. Oxygen vacancy defects were introduced to improve the charge transfer efficiency between the probe molecules and the substrate. The formation of nanoparticles on the surface of the laser-treated samples promoted the localized surface plasmon resonance properties, which ultimately induced the enhancement of the local electric field on the sample surface. The dual mechanisms of chemical and electromagnetic enhancement together determine the Raman scattering signal intensity. The as-treated MoO2-x/Mo thin films show good uniformity and reproducibility in surface-enhanced Raman spectroscopy measurements, with detection limits and enhancement factors of 10−9 mol/L and 2.68 × 105 for the dye methylene blue, respectively.The results of the finite-difference-time-domain simulations are in good agreement with the experimental results.