Speaker
Description
We consider the in-plane anisotropy of thick organic layers obtained by Langmuir-Blodgett technique. As the optical axis of theses Y-type structures lays in the incidence plane, the optical properties can be obtained from standard spectroscopic ellipsometry (SE) measurements [1]. Ordinary (no) and extraordinary (ne) complex refraction indexes are characterized for Cd2+-stabilized arachidic acid films whose thickness ranges from two-layers (2L) up to 200-layers (200L). Both no and ne are appropriately modeled by a Cauchy dispersion law. The Cauchy law parameters as well as the layer thickness are described as a function of the number of layers in the structure (Nlayers). In ellipsometry data analysis, multivariate methods have only been used in a very limited number of cases : Brouwer and coworkers linked the thickness of thin layers of colloidal gold nanoparticles to the principal components [2] and Garcia-Caurel performed hierarchical classification of FTIR-SE responses of bacterial films to classify microorganisms[3]. We recently used support vector machines to analyze the silver nanoparticles resonance peak parameters in plasmonic nanocomposites [4]. In this contribution, we use Complex principal Components Analysis (CPCA) of the complex SE data [5] and compare the results with standard PCA techniques applied to real and imaginary parts of the ellipticity ρ.
[1] R. Azzam and N. Bashara, Ellipsometry and polarized lightNorth-Holland personal library (North-Holland Pub. Co., 1977).
[2] E. M. Brouwer, E. S. Kooij, H. Wormeester, M. A. Hempenius, and B. Poelsema, Journal of Physical Chemistry B: Materials, surfaces, interfaces, & biophysical 108, 7748 (2004).
[3] E. Garcia-Caurel, J. Nguyen, L. Schwartz, and B. Drévillon, Thin Solid Films 455-456, 722 (2004).
[4] C. Guyot and M. Voué, Applied Surface Science (2016), arXiv:1506.01581 [cond-mat.mtrl-sci].
[5] J. Horel, J. Climate 23, 1660 (1984).
