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Multiple-angle ellipsometry of uniaxial ultrathin films is discussed analytically and by computer analysis. The various relations between angle of incidence, layer thickness, and refractive indices are presented. It is shown that multiple-angle ellipsometry conveys sets of experimental data well suited for computer analysis with high redundancy by exposing systematic experimental errors. The ellipsometric data allow no unique characterization of ultrathin, uniaxial, nonabsorbing films and it is demonstrated that the derived layer thickness depends strongly on assumptions of the layer anisotropy. For typical experimental results the allowed range of combinations of the refractive index values as a function of an assumed layer thickness is presented. Calculations show that certain combinations of refractive indices will result in an ellipsometric angle &A = 0 for all angles of incidence. Some of these combinations are physically realistic and might in fact be experimentally accessible. The potential of ellipsometric experiments to characterize ultrathin films is demonstrated by combining the method with data known from X-ray diffraction. Thus we have determined the refractive indices for a behenic acid monolayer in the S and CS phase, respectively, to nxS = 1.47, n2S = 1.54 and nxCS = 1.48, nPCS = 1.56. These values are deduced from the measured ellipsometric angles, a Lorentz-Lorenz approximation for the refractive indices, and structural data known from X-ray measurements.

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h) No difference, however, is found if the spacer-free lipid 1 is used for these experiments. This lipid does not show any specific interaction with streptavidiu under the given conditions. Its surface-pressurearea diagrams with free and titrated streptavidin are identical. This indicates that the binding of biotin to the protein does not change its unspecific adsorption characteristics. 464.[21] P. Meller, Rev. Sci. Znstrum. 59 (1988) 2225.[22] M.

The rich phase behaviour of monolayers of behenic acid (=docosanoic acid) has been analyzed by null ellipsometry in isothermic and isobaric measurements. By using structural data known from x‐ray measurements the anisotropy and refractive indices in the vicinity of the S‐CS phase transition have been calculated with a minimum of model assumptions. The calculated values are: nsx=1.47. ncsx=1.48. nsz=1.54. ncsz=1.55. and anisotropy γ=nx/nz ≈︁0.95. It is also shown that ellipsometry is a very sensitive and convenient method of detecting phase transitions. Its value for quantifying the roughness of the monolayer in the close vicinity of phase transitions due to thickness and density fluctuations is shown by the measurement of the parabolic intensity variations of the ellipsometric angle δΔ. The intensity minimum at the phase transition is much wider than in the adjacent homogeneous phases.