Surface plasmon resonance of sputtered Ag films: substrate and mass thickness dependence

The influence of substrate on the tunability of the localized surface plasmon resonance wavelength, lambda(SPR), of silver island films was investigated by magnetron sputtering the films on various substrates. It reveals that increasing refractive index of the substrate, n(sub), not only leads to redshift, but also an extension of the tunable range in lambda(SPR). Such effects can be greatly enhanced by increasing the mass thickness of the metallic islands. The resonance wavelength of an island film can be readily adjusted from the visible to the near infrared region of the electromagnetic spectrum. The sensitivity factor, Delta lambda(SPR)/Delta epsilon mu(av), where epsilon(av) is the interisland dielectric constant, was found to increase approximately linearly with the silver mass thickness up to 4 nm, from 60 nm to about 160 nm per dielectric constant unit.