EFFECT OF ROUGHNESS ON SURFACE-PLASMON SCATTERING IN GOLD-FILMS

Attenuated total reflection and rear-side light emission were measured on 50 nm thick gold films evaporated on glass substrates previously c oated with LiF layers of 0-500 nm thickness. The complex dielectric co nstant of metal films was determined as a function of the fluoride thi ckness. Roughness parameters (sigma, delta) were calculated from the a ngular distribution of the emission intensity and also from atomic for ce microscope images. Roughness amplitudes (delta) were found to be pr oportional to the fluoride thickness up to 350 nm, but over this value began to decrease. Both the average grain diameter and the correlatio n length (sigma) increased with the layer thickness in the whole obser ved range, indicating the flattening out of LiF at large thicknesses. Dielectric functions and surface plasmon wave-vectors of gold layers c hange drastically under the influence of increasing roughness amplitud es, which effect cannot be quantitatively described by the unmodified Fresnel equations.