DETERMINING THE RELATIVE PERMITTIVITY AND THICKNESS OF A LOSSLESS DIELECTRIC OVERLAYER ON A METAL-FILM USING OPTICALLY-EXCITED SURFACE-PLASMON POLARITONS

Numerical simulations based on the exact Fresnel equations are used to show that it is possible to determine uniquely the relative permittiv ity and thickness of a thin lossless dielectric film adsorbed on a gol d or silver layer. The calculations, which include the effects of up t o 1% random noise on the experimental data, show clearly that there is no degeneracy in the solutions of the Fresnel equations even for film s as thin as 2 nm. It is shown that gold is preferable to silver as a substrate when the overlayer properties need to be determined accurate ly. It is further shown that, if the overlayer is bounded by water rat her than air,then the experimental constraints would preclude the use of silver as a substrate but measurements would still be possible with gold.