Optical characterization of randomly microrough surfaces covered with very thin overlayers using effective medium approximation and Rayleigh-Rice theory

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Authors

OHLÍDAL Ivan VOHÁNKA Jiří ČERMÁK Martin FRANTA Daniel

Year of publication 2017
Type Article in Periodical
Magazine / Source Applied Surface Science
MU Faculty or unit

Faculty of Science

Citation
Web https://www.sciencedirect.com/science/article/pii/S0169433217312473
Doi http://dx.doi.org/10.1016/j.apsusc.2017.04.211
Keywords Ellipsometry;Thin films;Roughness;Effective medium approximation;Rayleigh-Rice theory
Description The modification of the effective medium approximation for randomly microrough surfaces covered by very thin overlayers based on inhomogeneous fictitious layers is formulated. The numerical analysis of this modification is performed using simulated ellipsometric data calculated using the Rayleigh–Rice theory. The system used to perform this numerical analysis consists of a randomly microrough silicon single crystal surface covered with a SiO2 overlayer. A comparison to the effective medium approximation based on homogeneous fictitious layers is carried out within this numerical analysis. For ellipsometry of the system mentioned above the possibilities and limitations of both the effective medium approximation approaches are discussed. The results obtained by means of the numerical analysis are confirmed by the ellipsometric characterization of two randomly microrough silicon single crystal substrates covered with native oxide overlayers. It is shown that the effective medium approximation approaches for this system exhibit strong deficiencies compared to the Rayleigh–Rice theory. The practical consequences implied by these results are presented. The results concerning the random microroughness are verified by means of measurements performed using atomic force microscopy.
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