The influence of dielectric environment on the localized surface plasmon resonance of silver-based composite thin films

Ag-based thin films with different topography were prepared by annealing process and laser irradiation, respectively. The tunability of localized surface plasmon resonance (LSPR) was realized by adjusting the cover layer thickness of ITO or TiO2. The effect of dielectric environment of Ag-based composite thin films on structure, surface morphology and optical property was investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscopy (AFM), UV-VIS-NIR double beam spectrometer and Raman system, respectively. With the thickness of dielectric layer increasing, the topography of as-irradiated Ag-based thin films became smoother while the as-annealed Ag-based thin films had a rougher surface. LSPR absorption of both ITO/Ag and TiO2/Ag bilayers showed red shift with the thickness of dielectric layer increasing. The electromagnetic field coupling between dielectric layers and Ag thin films contributed to increase significantly the sensitivity of surface enhanced Raman scattering (SERS). Additionally, the result of finite-difference time-domain (FDTD) simulation was in good agreement with that of the experiment.