Preparation of Silver Island Films with Tunable Surface Plasmon Resonance

Silver (Ag) island films have been prepared by pulsed laser ablation in vacuum using a XeCl excimer laser. The effects of the number of ablation pulses, the temperature and time of post-annealing on morphology and surface plasmons properties of the prepared Ag island films were investigated by extinction spectra and scanning electron microscopy. It is found that the films deposited with the ablation pulses of 60 or less are isolated Ag nanoparticles and the mean size of the nanoparticles increases monotonically with increasing the number of ablation pulses. Further increase of the number of ablation pulses up to 240, quasi-percolated Ag films are obtained, and for 600 pulses or more, continuous films will be formed. Extinction spectra results show that localized surface plasmons (LSPs) are supported by the Ag island films, while propagating surface plasmons are supported by the continuous Ag films. The LSPs of Ag island films consist of in-plane and out-of-plane modes. By changing the ablation pulse numbers and annealing conditions, the longitudinal and transverse dimensions of Ag islands could be adjusted, and then the peak positions and peak widths of in-plane and out-of-plane LSPs resonance modes could be effectively controlled.