SPECIFIC APPROACH OF GENERALIZED ELLIPSOMETRY FOR THE DETERMINATION OF WEAK INPLANE ANISOTROPY - APPLICATION TO LANGMUIR-BLODGETT ULTRATHINFILMS

We report on a procedure of generalized ellipsometry for the determina tion of the optical constants of stratified samples that present a wea k in-plane anisotropy. We first derive the analytical expressions of t he Jones reflection matrix and of the detected intensity for a rotatin g-polarizer ellipsometer configuration. These expressions show that th e in-plane birefringence and the orientation of the principal axes of the dielectric tensor can be obtained from a measurement of the normal ized off-diagonal terms of the reflection matrix as a function of the sample azimuth, followed by a Fourier analysis and a wavelength-by-wav elength inversion of these experimental data. We apply this method to the optical characterization of Langmuir-Blodgett molecular films depo sited on silicon substrates. The obtained results show that even for t ransparent and ultrathin films it is possible to accurately determine very weak in-plane birefringence and axis orientations. (C) 1998 Optic al Society of America.