Ms. Iryna Yurgelevych Profile

Iryna Yurgelevych

at Taras Shevchenko National University of Kyiv

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Publications (4)

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Proceedings Article | 6 February 2020 Paper

Influence of elastically-stressed state on polarization and electronic characteristics of amorphous ribbons

Leonid Poperenko, Olga Lopatynska, Iryna Yurgelevych

Proceedings Volume 11369, 1136907 (2020) https://doi.org/10.1117/12.2553469

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Influence of elastically-stressed state on polarization and electronic parameters of Fe- and Ni- based amorphous ribbons were studied by spectroellipsometric method within the infrared hv = 0.2 – 0.6 eV. The ellipsometric parameters Δ and Ψ were measured at for azimuthal directions in own plane of the samples. It was found that dependence of dielectric function is Drude-like one within the infrared for Ni₇₈Si₈B₁₄ ribbon. The parameters of the electronic subsystem, namely plasma frequency ωp and frequency of relaxation γ of the ribbons were found as depending on the azimuthal angle using the functions F₁ – F₃ based on the Drude relationship. These functions are linear dependences on the square of the frequency ω of the incident light or the light wavelength λ. It was found that plasma and relaxation frequencies decrease at two successive azimuthal rotations of the ribbon in its own plane. Consequently, the number of electrons becomes smaller, but the mobility of charge carriers increases. Such difference in the parameters behavior of the electronic subsystem indicates an induced anisotropy of the Ni₇₈Si₈B₁₄ ribbon due to stress in its surface layer. The obtained difference in the behavior of the dependences of the real part of dielectric function ε₁(Е) for both sides of the Fe₇₇Ni₁Si₉B₁₃ ribbon is explained by the specific features of the dynamic characteristics of the conduction electrons with Fermi energy.

Proceedings Article | 24 October 2012 Paper

Photoluminescence and absorption properties of the surface functional layer of CdTe crystals

Dmytro Gnatyuk, Leonid Poperenko, Iryna Yurgelevych, Oleksandr Dacenko, Toru Aoki, Manato Kimura

Proceedings Volume 8507, 85071U (2012) https://doi.org/10.1117/12.940764

KEYWORDS: Crystals, Surface finishing, Luminescence, Laser crystals, Absorption, Wet etching, Laser irradiation, Tellurium, Etching, Laser energy

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Photoluminescence and optical properties of the surface functional layer of detector-grade Cl-compensated semiconductor CdTe(111) single crystals modified by chemical etching and nanosecond laser processing have been studied. A bromine-methanol solution was used for polishing etching and nanosecond pulses of the second harmonic of YAG:Nd laser was applied as a radiation source. The photoluminescence spectra were excited at 80 K by an argon-ion laser with wavelength of 488 nm. The intrinsic emission band at 1.56 eV and broad defect band peaked at 1.45 eV were observed in the spectra before and after chemical and laser processing of CdTe crystals. The emission between 1.4-1.5 eV was associated with carrier recombination at defects in the surface region, so called the band of surface states. The optical parameters were determined using an ellipsometer with laser wavelength of 632.8 nm. Refraction n and absorption k indices were calculated within model of a homogeneous absorbing surface layer upon an absorbing substrate. An increase in n and k was observed at laser irradiation with energy density near or higher than the CdTe melting threshold that was attributed to an increase in volume fraction of Te in the surface region of the crystal. A decrease in the emission intensity at 1.45 eV was evidence of a reduction of the surface impurity contribution to the spectrum as a result of chemical etching. A rise of this band after irradiation was due of formation of point defects and dislocations in a surface layer of the crystal.

Proceedings Article | 10 October 2012 Paper

Peculiarities of optical response of silver-based metal-dielectric thin films

Mykola Biednov, Leonid Poperenko, Irina Yurgelevych

Proceedings Volume 8465, 84651D (2012) https://doi.org/10.1117/12.950718

KEYWORDS: Silver, Dielectrics, Particles, Nanoparticles, Absorption, Plasmons, Metals, Refraction, Optical properties, Composites

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Optical properties and effective dielectric function of nanostructured materials consisting of silver nanoparticles embed in dielectric matrix were studied. Experimental part was performed by means of angular and spectroscopic ellipsometry. Measured angular dependences reveal, that optical conductivity changes from metallic to dielectric with decrease of silver volume fraction. Complex effective dielectric function of the samples was measured within 295-825 nm wavelength range. Dispersion of optical constants of the samples with high silver volume fractions f<0.53 appears to be qualitatively similar to bulk silver. With decrease of Ag concentration influence of plasmon resonance on optical properties of the samples is observed. Measured spectral dependences reveal redshift and significant broadening of plasmon resonance peak of sample with f=0.28 in comparison to those with f=0.06-0.15 which can be explained within framework of surface plasmon resonance theory. Calculations show, that experimental data can’t be described using standard Maxwell-Garnett and Bruggeman effective-medium theories. Effective dielectric function of such composite films can be tuned by varying silver concentration, size and shape of the metal particles. We show that measured values of complex index of refraction for samples with f=0.08-0.2 can guarantee a strong light absorption for 400 nm film thickness according to Fresnel equations and demonstrate, that a considerable fraction of light can be trapped in the film due to total internal reflection of the light, scattered by noble metal nanoparticles.

Proceedings Article | 28 September 2011 Paper

Characterization of the surfaces of CdTe(111) single crystals after laser processing

Dmytro Gnatyuk, Leonid Poperenko, Iryna Yurgelevych, Toru Aoki

Proceedings Volume 8142, 81421N (2011) https://doi.org/10.1117/12.898417

KEYWORDS: Crystals, Laser crystals, Surface finishing, Wet etching, Laser irradiation, Laser processing, Refractive index, Atomic force microscopy, Laser energy, Etching

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Optical properties and morphology of the opposite polar faces of CdTe(111) single crystals subjected to irradiation with nanosecond pulses of the second harmonic of a YAG:Nd laser in a wide range of energy densities have been studied by multiple-angle-of-incidence single-wavelength ellipsometry and atomic force microscopy. The ellipsometric data have been interpreted by the semi-infinite medium model and it is assumed that there are no films on the crystal surface. Also the one-layer model is applied and the crystal relief is considered as a top layer. The refraction n and absorption k indexes of the surface layer are calculated using the fundamental ellipsometric equation and method of thickness curves. Laser irradiation results in an increase in the refractive index of the CdTe surface layer due to laser-induced transformation of the surface structure and it is associated with enriching of the CdTe surface with tellurium. The surface morphology of the crystals is modified at higher laser pulse energy densities because of the beginning of melting of prominent irregularities and thin surface layer. The effects of irradiation with nanosecond laser pulses on the polar surfaces of CdTe(111) crystals are analyzed.

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