Spectroscopic ellipsometry on a novel cyanine dyes in Langmuir-Blodgett multilayers

We have investigated on cyanine dye (HQ) in Langmuir-Blodgett (LB) films by spectroscopic ellipsometer (SE) and compared the results with that obtained by using small angle X-ray diffraction (SAXD). It is found from the isotherms that there is a critical point on Langmuir films near the area 0.8 nm2/molecule for HQ LB films with and without Cd2+ ions, respectively and suggested that the facts should result from the phase transition due to the change of molecular tilt angle on surface of sub-phase. The refractive indexes as a function of the wavelength λ are reported by the SE method using the three layers-model (air-LB film-silicon wafer) and Cauchy dispersion equation, for the first time presented in literature. The thickness of a single deposited layer is 2.45 nm on average. The thickness of per monolayer is agreement with those obtained by SAXD measurements.