Laser irradiation induced tunable localized surface plasmon resonance of silver thin film

Tunable localized surface plasmon resonance (LSPR) properties of silver thin films were realized by CO2 laser irradiation. The effects of laser irradiation on the structure, morphology and optical property of the samples were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscopy (AFM), UV-VIS-NIR double beam spectrometer and Raman system, respectively. XRD patterns show that laser irradiation has the effects of improving grain growth and orientation of Ag thin films. With laser irradiation power increasing, the topography of as-irradiated silver thin films were observed to develop discontinuous nano-ellipsoid structure with a red-shift of the surface plasmon resonance wavelength in visible region. Both the various ellipsoid sizes and the states of aggregation of as-irradiated silver thin films contributed to increase significantly the sensitivity of surface enhanced Raman scattering (SERS). Additionally, the simulation result of Finite-Difference Time-Domain (FDTD) was proved to be in good agreement with that of the experiment.