Metal coverage dependence of local optical properties of semicontinuous metallic films

Abstract

Semicontinuous silver films on insulator substrates, which exhibit unique electrical and optical properties, were studied experimentally and theoretically. The percolation threshold of the films, which were synthesized by laser ablation, was determined from a combination of studies of the surface morphology by electron microscopy and the dc electrical resistance as a function of metal concentration. Local optical properties measured by near-field optical microscopy were compared with theoretical results obtained using the Block elimination method, with good agreement. Local field distributions were found to depend on the metal concentration and wavelength of illumination. The degree of localization was found to increase at metal concentrations above and below the percolation threshold.