Прегледај по Аутор "Mirjanić, D. Lj."

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    Absorption Features of Symmetric Molecular Nanofilms
    (American Scientific Publishers, 2013) Šetrajčić, J. P.; Markoski, B.; Rodić, D.; Pelemiš, S. S.; Vučenović, S. M.; Škipina, B.; Mirjanić, D. Lj.
    Electronic components are used today in extreme physical conditions and in that sense, ultrathin dielectric crystalline films could be used as surface layers for electronic component protection. Calculating dynamical permittivity by the single-pole Green’s functions it was shown that the threshold of light absorption can be moved along frequencies, changing the film thickness and the intensity of boundary perturbations. We study the basic micro and macroscopic physical characteristics of symmetric ultrathin molecular crystalline films and one can see that essential optical properties of these systems arise with perturbation conditions, which appear at their surface layers. Depending on the values of the parameters of surface interactions, certain energy levels can lie outside the energy band of the ideal crystal, so there appear the surface localized states of excitons. Characteristic resonant peaks appear in the dependence of dielectric permittivity and absorption index (extinction coefficient) of ultrathin film on frequency of external electro-magnetic field.
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    Selective IR absorption in molecular nanofilms
    (Elsevier, 2011) Škipina, B.; Mirjanić, D. Lj.; Vučenović, S. M.; Šetrajčić, J. P.; Šetrajčić, I. J.; Šetrajčić-Tomić, A. J.; Pelemiš, S. S.; Markoski, B.
    We have formulated a microscopic theory of optical properties of ultrathin molecular films (nanofilms), i.e. quasi 2D systems parallel to XY planes bounded by two surfaces. Exposure of nanofilms to the external electromagnetic fields has result in creation of excitons – but different than bulk ones. Harmonic exciton states were calculated using the method of two-time, retarded, temperature dependent Green’s functions. It has been shown that two types of optical excitations can occur: bulk and surface exciton states. Exciton energy dispersion law shows discrete behavior with non-zero values. Analysis of the dielectric properties of these crystalline systems for low exciton concentration shows that the permittivity strongly depends on boundary parameters and the thickness of the film. In addition, permittivity shows very narrow and discrete dependence of external electromagnetic field frequency, which is a consequence of both resonance and quantum size effects. Influences of boundary conditions on optical characteristics (through analyses of dynamical absorption coefficient) of these nanostructures were specially and in details explored.