Spectro-ellipsometry on cadmium stearate Langmuir-Blodgett films

We have studied cadmium stearate Langmuir-Blodgett (LB) films by spectroscopic ellipsometry (SE) and we have compared the results with those obtained by using X-ray refectivity and atomic force microscopy. The measurements on cadmium stearate LB films deposited on silicon wafers capped by a native oxide layer provide sound results for films formed by 1-25 molecular layers. The experimental data are well fitted by a Cauchy-type model over the whole examined wavelength range (245-725 nm). The model, which takes into account the anisotropy of the film, uses the film thickness of several mono- and multilayers films, together with the in-plane and the out-of-plane components of the refraction index as free parameters. The obtained mean thickness of the monolayer (ML), 2.50 +/- 0.02 nm, very well agrees with X-rays reflectivity measurements and with literature data. (C) 2002 Elsevier Science B.V. All rights reserved.