Formation and characterization of surface metal nanostructures with tunable optical properties

The ability to form surface nanostructures from silver and gold films on various oxides under 400 keV ion irradiation and optical properties of the fabricated particle arrays were studied by means of scanning electron microscopy and UV–visible optical spectroscopy. The resulting structures consist of relatively large surface nanoislands of irregular shape having size in the range 30–100 nm and smaller nanoclusters with diameter less than 10 nm, embedded into oxide matrix. The geometry of the surface structures depends on the ion-beam mixing (IBM) conditions, metal thickness and substrate material. It was found that optical properties of the samples are affected by multipolar surface plasmon resonances (SPR) in nanoislands. The comparison of extinction and absorption spectra has resulted in considerable insight concerning the nature of SPR modes. The resonance wavelength can be adjusted throughout the visible region by substrate material, IBM conditions, ion specie and RIE post treatment.