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Wyświetlanie 1-3 z 3
Tytuł:
Optical Properties of $As_{36}Te_{42}Ge_{10}Si_{12}$ Thin Films
Autorzy:
Hegab, N.
El-Mallah, H.
Powiązania:
https://bibliotekanauki.pl/articles/1535744.pdf
Data publikacji:
2010-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.20.-e
78.20.Ci
78.66.-w
78.68.+m
Opis:
Thermally evaporated $As_{36}Te_{42}Ge_{10}Si_{12}$ amorphous chalcogenide films were prepared in a vacuum of $10^{-5}$ Torr on to glass substrates hold at about 300 K during the deposition process. Measurements of the optical properties have been made. The optical transmittance and reflectance spectra of films in the thickness range 155-395 nm were measured in the wavelength λ range 500-2500 nm. The refractive index n, the extinction coefficient k and the absorption coefficient α were calculated for the studied films. It is found that both n and k are independent on the film thickness. The refractive index n has anomalous behavior for the wavelength λ range 500-1500 nm, while it has normal dispersion for the wavelength greater than 1500 nm. The optical energy gap was estimated from absorption coefficient. The allowed optical transitions were found to be nondirect transitions with optical gap of 1.08 eV for the sample under test. The effect of annealing on the obtained optical parameters was also investigated.
Źródło:
Acta Physica Polonica A; 2010, 118, 4; 637-642
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
AC Conductivity and Dielectric Properties οf Amorphous $Te_{42}As_{36}Ge_{10}Si_{12}$ Glass
Autorzy:
Hegab, N.
El-Mallah, H.
Powiązania:
https://bibliotekanauki.pl/articles/1585075.pdf
Data publikacji:
2009-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.80.Ng
77.22.-d
Opis:
$Te_{42}As_{36}Ge_{10}Si_{12}$ chalcogenide composition was prepared by conventional melt-quenching. The ac conductivity and the dielectric properties were carried out in the frequency range 0.5×$10^{3}$-4×$10^{6}$ Hz and temperature range 300-423 K. The analysis of the experimental results of the frequency dependence of ac conductivity $σ_{ac}(ω)$ indicates that $σ_{ac}(ω)$ is proportional to $ω^{s}$ where s> 1. The temperature dependence of both ac conductivity and the parameter s is reasonably well interpreted by the correlated barrier hopping model. The maximum barrier height $W_{m}$ calculated from ac conductivity and the density of localized states were determined. Values of dielectric constant $ε_{1}$ and dielectric loss $ε_{2}$ were found to decrease with frequency and increase with temperature. The analysis of dielectric loss leads to determine the barrier height $W_{m}$ and agrees with that proposed by the theory of hopping of charge carriers over potential barrier between charged defect states as suggested by Elliott in case of chalcogenide glasses.
Źródło:
Acta Physica Polonica A; 2009, 116, 6; 1048-1052
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ac Conductivity and Dielectric Properties of Amorphous $Ge_{15}Se_{60}X_{25}$ ( X = As or Sn) Films
Autorzy:
Hegab, N.
Afifi, M.
Atyia, H.
Ismael, M.
Powiązania:
https://bibliotekanauki.pl/articles/1505386.pdf
Data publikacji:
2011-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.80.Ng
77.22.-d
Opis:
The ac conductivity and dielectric properties of $Ge_{15}Se_{60} X_{25}$ (X = As or Sn) thin films are reported in this paper. The thin films were deposited by thermal evaporation at $10^{-5}$ Torr pressure. The films were well characterized by X-ray diffraction, differential thermal analysis and energy dispersive X-ray spectroscopy. The ac conductivity was measured over temperature range 303-413 K and frequency range $10^2-10^5$ Hz. The frequency dependence of the ac conductivity was found to be linear with slope which lies very close to unity and is independent of temperature. This behavior can be explained in terms of the correlated barrier hopping between centers forming intimate valence alternation pairs. Values of the dielectric constant $ε_1$ were found to decrease with frequency and increase with temperature. The maximum barrier height $W_{m}$ for each sample, which was calculated from the dielectric measurements according to the Guinitin equation, agrees with the theory of hopping of charge carriers over potential barrier as suggested by Elliott in case of chalcogenide glasses. The density of localized state near the Fermi level was estimated for the studied films.
Źródło:
Acta Physica Polonica A; 2011, 119, 3; 416-423
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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