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Contributed Speaker

Assoc. Prof. Duško Čakara

Centre for micro- and nanosciences and technologies, University of Rijeka, Croatia

E-mail

dcakara@uniri.hr

Effective medium theory for optical modeling of chemically and structurally heterogeneous thin films

Duško Čakara ^1,2

¹ Center for micro- and nanosciences and technologies, University of Rijeka, Croatia

² Faculty of biotechnology and drug development, University of Rijeka, Croatia

The macroscopically observable optoelectronic properties of thin film materials may be determined from their dielectric function (DF), accessible through optical modeling of the experimental ellipsometric spectra. Models for the DF of optical materials in the visible and near infrared region reside on their postulated structure. For chemically heterogeneous materials that involve phase(s) mixed at a length scale that starts with the molecule size and goes up to several tens of nanometers, the relationship between the structure and the DF (viz. their optical properties) may present a significant challenge , whereby most of the available modellng approaches follow from the effective medium theory. This involves postulation of the composition and structure of the optical phases, as well as model approximations that are not applicable generally, but need to be validated for each specific system. The paper discusses the DFs based on the Maxwell-Garnett's and Bruggeman's effective medium approximations for modeling the ellipsometrically measured reflection coefficients of several morphologically different composite thin films, formed by the oxidation of metal (Cu, Zn) surfaces in a chloride solution (Fig. 1), in the presence and absence of several organic corrosion inhibitors [1,2], as well as for a polymer brush grafted at the Si/SiO2 surface, in the presence and absence of gold nanoparticles [3].

Keywords: composite, film, ellipsometry, optical, model.

Figure1. The optical model and the effective medium dielectric function for the film formed by the Cu ₂ O/corrosion inhibitor colloidal phases [1].

References

[1] D. Čakara, R. Peter, M. Finšgar , Surf. Interfaces , 2022 , 32, 102108

[2] M. Finšgar, D. Čakara , Appl Surf Sci , 2022 , 606 , 154843

[3] D. Čakara, P. Ritzert, D. Boyaciyan, R. von Klitzing, 45th Jubilee International Convention on Information, Communication and Electronic Technology (MIPRO) , 2022 , 606 , 223–229

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