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Wyszukujesz frazę "Šćepanović, M." wg kryterium: Autor


Wyświetlanie 1-5 z 5
Tytuł:
Use of Phonon Confinement Model in Simulation οf Raman Spectra of Nanostructured Materials
Autorzy:
Grujić-Brojčin, M.
Šćepanović, M.
Dohcević-Mitrović, Z.
Popović, Z.
Powiązania:
https://bibliotekanauki.pl/articles/1807810.pdf
Data publikacji:
2009-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.07.Wx
78.30.-j
63.22.-m
07.05.Tp
Opis:
The simulation of the Raman spectra of nanostructured materials, where the effects of frequency shift and asymmetric broadening of the Raman modes play an important role, can be very useful in systematic characterization of these materials. Use of phonon confinement model for calculating Raman spectra of different nanomaterials is considered both from the viewpoint of different confinement function and the confinement strength, as well as the dimensionality of the confinement model. The phonon dispersion relations and the choice of their approximation are also studied. The influence of particle size distribution on the shape of the calculated spectra is discussed and contributions of Gaussian and asymmetric Gaussian distribution are compared. The effects of average and inhomogeneous strain on the behavior of simulated Raman spectra are also discussed. The results of the phonon confinement model are compared to the experimental spectra of $CeO_2$ and anatase $TiO_2$ nanopowders.
Źródło:
Acta Physica Polonica A; 2009, 116, 1; 51-54
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optical Characterization of Laser-Synthesized Anatase $TiO_{2}$ Nanopowders by Spectroscopic Ellipsometry and Photoluminescence Measurements
Autorzy:
Šćepanović, M.
Grujić-Brojčin, M.
Mirić, M.
Dohčević-Mitrović, Z.
Popović, Z.
Powiązania:
https://bibliotekanauki.pl/articles/1795613.pdf
Data publikacji:
2009-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.07.Wx
78.67.Bf
73.22.-f
07.60.Fs
78.55.-m
Opis:
Nanosized titania $(TiO_{2})$ is synthesized by laser-induced pyrolysis using $TiCl_{4}$ as a liquid precursor. X-ray diffraction and Raman scattering confirmed anatase structure of $TiO_{2}$ nanocrystals. The dielectric function ε(ω) of $TiO_{2}$ nanopowders has been determined by spectroscopic ellipsometry in the energy range from 1.5 to 6 eV at room temperature. The features observed in ε(ω) have been fitted to analytical line shapes by using the second derivatives of experimental spectra. The energies corresponding to different interband electronic transitions have been determined. Photoluminescence measurements have been carried out in vacuum for T = 20 K and T = 300 K. Under laser irradiation with sub-band gap photon energy, anatase nanocrystals have displayed strong visible photoluminescence emission. In this broad photoluminescence band different variations of line shape and position with excitation energy and temperature are observed for nanopowders with different crystallite size, pointing out to the various electronic transitions mediated by defect levels within the band gap.
Źródło:
Acta Physica Polonica A; 2009, 116, 4; 603-606
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Characterization of ZnSe Nanolayers by Spectroscopic Ellipsometry
Autorzy:
Šćepanović, M.
Grujić-Brojčin, M.
Nesheva, D.
Levi, Z.
Bineva, I.
Popović, Z.
Powiązania:
https://bibliotekanauki.pl/articles/1795712.pdf
Data publikacji:
2009-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.07.-b
81.15.-z
81.05.Dz
78.30.-j
07.60.Fs
68.55.-a
Opis:
Single layers of ZnSe with thicknesses of 30, 40, 50, 70 and 100 nm are deposited at room substrate temperature by thermal evaporation of ZnSe powder in vacuum. The layers surface morphology has been investigated by atomic force microscopy. Structural characterization by the Raman scattering measurement revealed the existence of randomly oriented crystalline ZnSe particles in all layers, and the presence of amorphous phase in layers thinner than 100 nm. The ellipsometric measurements were performed in the range from 1.5 to 5 eV at room temperature in air. To interpret the experimental results, the Bruggeman effective medium approximation of dielectric function of ZnSe layers has been used, representing the layers as different mixtures of crystalline ZnSe (c-ZnSe), amorphous ZnSe (a-ZnSe), and voids. The assumption of polycrystalline ZnSe layers modeled as mixture of porous c-ZnSe (with volume fraction of voids ≈ 0.17) and a-ZnSe gives the best fit of ellipsometric experimental data. Single layer thicknesses similar to those expected from preparation conditions have been obtained by this fitting procedure. It has been also found that decrease in the layer thickness causes an increase of the volume fraction of a-ZnSe. Thus, c-ZnSe/a-ZnSe ratio, porosity and layer thickness obtained by spectroscopic ellipsometry, provides useful information about crystallinity and micro-/nanostructure of ZnSe nanolayers.
Źródło:
Acta Physica Polonica A; 2009, 116, 4; 708-711
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Effects of Nonstoichiometry on Optical Properties of Oxide Nanopowders
Autorzy:
Šćepanović, M.
Grujić-Brojčin, M.
Dohčević-Mitrović, Z.
Vojisavljević, K.
Srećković, T.
Popović, Z. V.
Powiązania:
https://bibliotekanauki.pl/articles/2047872.pdf
Data publikacji:
2007-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.84.Bw
73.63.Bd
78.67.-n
78.55.-m
78.30.-j
Opis:
In this paper we illustrate the change of optical properties of mechanically activated wurtzite ZnO powder and laser synthesized anatase TiO$\text{}_{2}$ nanopowder due to the nonstoichiometry caused by mechanical activation and/or laser irradiation in vacuum. Both of the investigated materials are widely used in optoelectronics and the examination of their optical properties under different preparation and environmental conditions is of great practical interest.
Źródło:
Acta Physica Polonica A; 2007, 112, 5; 1013-1018
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Low-Frequency Raman Spectroscopy of Pure and La-Doped $TiO_2$ Nanopowders Synthesized by Sol-Gel Method
Autorzy:
Šćepanović, M.
Aškrabić, S.
Grujić-Brojčin, M.
Golubović, A.
Dohčević-Mitrović, Z.
Kremenović, A.
Popović, Z.
Powiązania:
https://bibliotekanauki.pl/articles/1807845.pdf
Data publikacji:
2009-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.20.Fw
81.07.Wx
78.30.-j
63.22.-m
Opis:
Pure and La-doped titania $(TiO_2)$ nanopowders are synthesized by sol-gel technology. The crystallite sizes determined by X-ray diffraction measurements range from 10 to 15 nm. Dependence of structural and morphological characteristics of nanopowders on synthesis conditions and $La^{3+}$ content is investigated by the Raman spectroscopy. Very intensive modes observed in the Raman spectra of all nanopowder samples are assigned to anatase phase of $TiO_2$. Additional Raman modes of extremely low intensity can be related to the presence of a small amount of brookite amorphous phase in nanopowders, which is in accordance with the results of X-ray diffraction analysis. The particle size distribution in TiO_2 nanopowders was estimated from the low frequency Raman spectra, using the fact that the phonon modes in nanosized $TiO_2$ observed in the low frequency region (ω <40 $cm^{-1}$) can be well described by the elastic continuum model, assuming that nanoparticles are of perfect spherical shape and isotropic. The nanosized particle distribution obtained by this method is used for the calculation of the frequency and shape of the most intensive $E_g$ Raman mode in anatase $TiO_2$ by the phonon confinement model. The calculated broadening of this mode, associated with the particle size distribution, coincides well with the characteristics of $E_g$ mode observed in measured Raman spectra of $TiO_2$ nanopowders. This confirms the Raman spectroscopy method as a powerful tool for determination of particle size distribution in nanosized materials.
Źródło:
Acta Physica Polonica A; 2009, 116, 1; 99-102
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-5 z 5

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