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Wyświetlanie 1-3 z 3
Tytuł:
Raman Scattering from ZnSe Nanolayers
Autorzy:
Nesheva, D.
Šćepanović, M.
Aškrabić, S.
Levi, Z.
Bineva, I.
Popović, Z.
Powiązania:
https://bibliotekanauki.pl/articles/1807824.pdf
Data publikacji:
2009-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.15.Ef
81.05.Dz
78.30.-j
68.55.-a
Opis:
A series of ZnSe single layers having thickness between 30 nm and 1 μm was deposited on c-Si and glass substrates at room substrate temperature. Thermal evaporation of ZnSe powder in high vacuum has been applied. Moreover, $SiO_x$/ZnSe periodic multilayers prepared by the same deposition technique and having ZnSe layer thickness of 2 and 4 nm have been studied. Raman spectra were measured at 295 K, using the 442 nm line of a He-Cd laser as well as different lines of the $Ar^+$ or $Ar^+//Kr^+$ lasers. The observed Raman features have been related to multiple optical phonon (1LO to 4LO) light scattering and connected with the existence of randomly oriented crystalline ZnSe grains in both ZnSe single layers and ZnSe layers of the multilayers. Relatively large line width ( ≈ 15 $cm^{-1}$) of the 1LO band has been observed and related to lattice distortion in the crystalline grains and existence of amorphous phase in the layers thinner than 100 nm. The Raman spectra measured on both ZnSe single layers and $SiO_x$/ZnSe multilayers using the 488 nm line with a gradually increased laser beam power indicate an increased crystallinity at high irradiation levels.
Źródło:
Acta Physica Polonica A; 2009, 116, 1; 75-77
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Characterization of La-Doped $TiO_2$ Nanopowders by Raman Spectroscopy
Autorzy:
Šćepanović, M.
Aškrabić, S.
Berec, V.
Golubović, A.
Dohčević-Mitrović, Z.
Kremenović, A.
Popović, Z.
Powiązania:
https://bibliotekanauki.pl/articles/1808047.pdf
Data publikacji:
2009-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.20.Fw
81.07.Wx
78.30.-j
07.05.Tp
Opis:
Titanium dioxide $(TiO_2)$ nanopowders doped with 0.65, 1, 2, 3 and 4 wt.% of lanthanum ions $(La^{3+})$ were synthesized by sol-gel technology. Dependence of structural and morphological characteristics of nanopowders on $La^{3+}$ content and synthesis conditions 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 certain amount of highly disordered brookite phase in nanopowders. Dependence of the intensity ratio of the Raman modes which originate from anatase and brookite on doping conditions is specially analyzed. In order to estimate the variation of nanocrystallite size with dopant content, shift and asymmetrical broadening of the most intensive $E_g$ Raman mode of anatase are analyzed by phonon confinement model. The obtained results are compared with the results of X-ray diffraction spectroscopy. Special attention is dedicated to the changes in the Raman spectra of pure and La-doped $TiO_2$ nanopowders observed after high temperature treatment.
Źródło:
Acta Physica Polonica A; 2009, 115, 4; 771-774
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 1-3 z 3

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