Yazar "AlGarni, Sabah E." seçeneğine göre listele

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    Band offsets, optical conduction, photoelectric and dielectric dispersion in InSe/Sb2 Te3 heterojunctions
    (SciELO, 2021) Alfhaid, Latifah Hamad Khalid; Qasrawi, Atef Fayez; AlGarni, Sabah E.
    InSe based heterojunction devices gain importance in optoelectronic applications in NIR range as multipurpose sensors. For this reason, InSe/Sb2 Te3 heterojunctions are constructed as NIR sensors by the thermal evaporation technique. The structural, optical, dielectric and photoelectric properties of InSe/Sb2 Te3 heterojunctions are explored by X-ray diffraction and ultraviolet-visible light spectrophotometry techniques. The structural analyses revealed the preferred growth of polycrystalline hexagonal Sb2 Te3 onto amorphous InSe as a major phase. Optically, the coating of Sb2 Te3 onto InSe enhanced the light absorbability of InSe by more than 18 times, redshifts the energy band gap, increased the dielectric constant by ~5 times and increased the optical conductivity by 35 times in the NIR range of light. A conduction and valance band offsets of 0.40 and 0.68 eV are determined for the InSe/Sb2 Te3 heterojunction devices. In addition, the Drude-Lorentz fittings of the optical conductivity indicated a remarkable increase in the plasmon frequency values upon depositing of Sb2 Te3 onto InSe. The illumination intensity and time dependent photocurrent measurements resulted in an enhancement in the photocurrent values by one order of magnitude. The response time of the devices is sufficiently short to nominate the InSe/Sb2 Te3 heterojunction devices as fast responding NIR sensors suitable for optoelectronic applications.
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    Design and characterization of ZnSe/GeO2 heterojunctions as bandstop filters and negative capacitance devices
    (Wiley-VCH Verlag, 2021) AlGarni, Sabah E.; Qasrawi, Atef Fayez; Khusayfan, Najla M.
    Herein, polycrystalline films of ZnSe which are coated onto Au substrates and recoated with amorphous layers of GeO2 are used as active material to perform as bandstop filters. The stacked layers of Au/ZnSe/GeO2 are coated under pressure of 10?5 mbar. The device is characterized by X-ray diffraction, X-ray photoelectron, X-ray fluorescence, and impedance spectroscopy techniques. It is observed that when the device is contacted with carbon point contacts, it exhibits resonance–antiresonance phenomena near 1.0 GHz. The Au/ZnSe/GeO2/C devices display negative capacitance effect in the frequency domain of 0.96–1.80 GHz. Analyses of the conductivity and capacitance spectra in the frequency domain of 0.01–1.80 GHz reveal the domination of conduction by quantum mechanical tunneling below 0.58 GHz and by the correlated barriers hopping above 0.58 GHz. In addition, characterizations of the impedance, reflection coefficient, return loss ((Formula presented.)) and voltage standing wave ratios ((Formula presented.)) spectra of the device indicated ideal bandstop filter features. The notch frequency of the filter is 1.56 GHz. At this critical frequency, the Au/ZnSe/GeO2/C devices display ideal characteristics presented by VSWR of 1.0, (Formula presented.) value of 28.9 dB. These features make the Au/ZnSe/GeO2/C heterojunction devices promising for use in telecommunication technology.
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    Effects of Ag2O nanosheets on the structural, optical, and dielectric properties of GeO2 stacked layers
    (Wiley-VCH Verlag, 2021) Alharbi, S. R.; Qasrawi, Atef Fayez; AlGarni, Sabah E.
    Herein, the effects of insertion of Ag2O nanosheets of thicknesses 25–75 nm between stacked layers of GeO2 on the structural, morphological, and optical properties of germanium dioxide are explored. While the stacking of GeO2/Ag2O/GeO2 layers does not alter the amorphous nature of the structure, significant effects on the transmittance, reflectance, absorption coefficient, Urbach's tails, and dielectric constant are observed. Silver oxide nanosheets successfully enhance the light absorbability of germanium dioxide in the visible and the infrared (IR) range of light. The light absorbability is increased by more than 12 times after the insertion of 75 nm-thick Ag2O nanosheets. In addition, a widening in Urbach's tails and narrowing in the indirect bandgap of GeO2 are detected as a result of increasing Ag2O layer thickness. The dielectric constant and optical conductivity are also increased by ?59.6% and 191.4% in the IR range of light. The enhancement in the optical properties of GeO2 that results from the insertion of Ag2O nanosheets makes germanium dioxide more appropriate for optoelectronic applications.
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    Effects of polycrystalline GeO2 substrates on the structural, optical and electrical properties of ZnSe thin films
    (IOPScience, 2021) AlGarni, Sabah E.; Qasrawi, Atef Fayez; Khusayfan, Najla M.
    Herein, the effects of polycrystalline germanium dioxide substrates on the structural, morphological, optical and electrical properties of zinc selenide thin films are reported. Thin films of ZnSe coated onto GeO2 are prepared by the thermal evaporation technique under vacuum pressure of 10–5 mbar. Compared to films grown onto glass substrates, ZnSe films deposited onto GeO2 exhibited narrower band gap and improved light absorbability. When ZnSe films are recoated onto gold substrates, the insertion of GeO2 layers between Au and ZnSe shifted the resonance peaks of the capacitance spectra from 527 to 711 MHz and formed new peak at 1000 MHz making the Au/ZnSe interfaces more appropriate for use as microwave cavities and as negative capacitance sources. Analysis of the conductivity spectra in the frequency domain of 10–1800 MHz revealed the domination of quantum mechanical tunneling and correlated barriers hoping of charge carriers in the samples. The fitting of the conductivity spectra assuming combined current conduction by these two mechanisms has shown that GeO2 layers increased the density of state near the Fermi level and shortened the scattering time of charge carriers. The designed Au/GeO2/ZnSe/C devices are also found to be suitable as band pass/ stop filters. The notch frequency of these filters is shifted from 1420 MHz to 1050 MHz as a result of GeO2 participation in the structure of the Au/ZnSe devices.
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    Yb/inse/sb2te3 /au broken gap heterojunction devices designed as current rectifiers, tunable mos capacitors and gigahertz microwave cavities
    (S.C. Virtual Company of Phisics S.R.L, 2021) Alfhaid, Latifah Hamad Khalid; Qasrawi, Atef Fayez; AlGarni, Sabah E.
    Herein, we report the design and experimental characterization of a broken gap heterojunction devices fabricated by vacuum evaporation of Yb/InSe/Sb2Te3/Au stacked layers. The structural characterizations of the stacked layers revealed an amorphous/polycrystalline heterojunction type. The measurements of capacitance-voltage characteristics in the frequency domain of 1.0-9.0 MHz displayed tunable metal-oxide-semiconductor (MOS) characteristics. The frequency dependent built-in voltage, depletion width, and free carrier density is also investigated. In addition, the analyses of current-voltage characteristics have shown that the device displays highly stable current rectification ratios of ~103 above 0.20 V. Moreover, the ac signal analyses in the frequency domain of 10-1800 MHz have shown the possible tunability of the conductance and capacitance over a wide range of frequency. Furthermore, the microwave cutoff frequency spectra indicated increasing cutoff frequency limits with increasing incident signal frequency. The microwave cutoff frequency reached 7.1 GHz for a propagating signal of frequency of 1800 MHz.