Thermal annealing induced tunable localized surface plasmon resonance of Au/Ag bimetallic thin film

Tunable localized surface plasmon resonance (LSPR) was achieved on thermally annealed thin films composed of Au deposited on Ag. Characterization of the crystallographic structure, morphology, and optical properties of the thin films was done by X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscopy (AFM), UV-VIS-NIR double-beam spectrometer, and Raman system. The XRD results confirmed that thermal annealing improved the grain growth and orientation of Au/Ag bimetallic thin films. AFM and SEM results showed that Au/Ag bimetallic thin films transformed into Au/Ag ellipsoid nanoparticles (NPs) on thermal annealing. The LSPR wavelength of Au/Ag NPs could be tuned between 500 nm and 342 nm. Additionally, the Raman scattering could be adjusted by increasing the thickness of Ag in the Au/Ag bimetallic composite structure.