EVALUATION OF ARACHIDIC ACID LANGMUIR-BLODGETT ULTRATHIN FILMS ON SILVER THIN-FILMS FROM SCATTERED-LIGHT USING SURFACE-PLASMON POLARITON EXCITED AT THE INTERFACES

Attenuated total reflection (ATR) properties and scattered light prope rties were measured for Ag thin films and arachidic acid (C20) Langmui r-Blodgett (LB) ultrathin films on the Ag thin films to obtain the inf ormation about their complex dielectric constants and surface roughnes s utilizing an excited surface plasmon polariton. The complex dielectr ic constants for the Ag thin films and the C20 LB films were obtained by fitting the calculated ATR curves to the experimental ones. The sur face roughnesses of these films were estimated by the angular distribu tion of the scattered light assuming the Gaussian function as an autoc orrelation function and a linear superposition of roughness spectra. T he angular spectra strongly depended on the roughness parameters: the transverse correlation length sigma and the surface corrugation depth delta. The experimental angular distributions were explained by some p airs of sigma and delta. It was suggested that the surface roughness o f the C20 LB films changed with the number of monolayers since the ang ular spectra varied with the number of the C20 LB monolayers on the Ag films. It is thought that the measurement of the scattered light is u seful to evaluate surface roughnesses of LB ultrathin films.