Preparation And Study On Optical-electrical Properties Of Silver Thin Film

When the resonance frequency of conduction electrons and incident light are matched,localized surface plasmon resonance（LSPR）induced by collective electron charge oscillations in metallic nanoparticles（NPs）shows its strong confinement and enhancement of near-field amplitude.LSPR has many applications,such as surface enhanced Raman scattering（SERS）,photothermal therapy,nonlinear optics and other fields.The efficiency of these applications largely depends on the LSPR wavelength which is not only determined by the size,shape and the surrounding medium of metallic NPs but also by the metal materials.With the development of nanomaterials,various fields are effectively related with nanostructures,so the detection and analysis of photoelectric properties for nanomaterials is important.Silver（Ag）,a noble metal,achieves the continuous tunability of resonant absorption from visible to near-infrared.Ag NPs with the ideal shape or environmental medium will get a suitable LSPR wavelength.In recent years,the development of laser technology enables laser irradiation to control the morphology of Ag-based films.The relationship between laser irradiation and thermal annealing and the influence of different dielectric layer on the resonant absorption of Ag-based films also need more in-depth researches.In this paper,nano-ellipsoidal Ag NPs were prepared by laser irradiation to control the resonant absorption.Then different dielectric layers were deposited on silver-based thin films with different morphology.The influence of environmental media on LSPR was also investigated.Finally,the difference between annealing process and laser irradiation was observed.The results are as follows:（1）Laser irradiation with various laser power induced increased size and spacing of Ag NPs,the red shift of LSPR wavelength and the decrased intensity of SERS.（2）ITO/Ag and TiO₂/Ag bilayers with different dielectric layers thickness both showed red shift of LSPR wavelength.ITO had a wider range of shift wavelength,but TiO₂ had a higher absorption and SERS intensities in as-irradiated Ag-based thin films.（3）With the thickness increasing,increased Ag NPs size induced by thermal annealing process showed a red shift of LSPR wavelength and the different SERS.