Yazar "Almotiri, R. A." seçeneğine göre listele

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    Ag/n–Si/p–MgSe/(Ag, C, Au, Pt) devices designed as current rectifiers, photodetectors and as ac signal filters suitable for VLC, IR Q3 and 6G technologies
    (IOP Publishing, 2022) Almotiri, R. A.; Qasrawi, Atef Fayez; Algarni, Sabah E.
    Herein the fabrication and practical applications of p-MgSe thin films as active p-layer of electronic devices are reported. MgSe films are prepared by a vacuum evaporation technique onto n-Si substrates under a vacuum pressure of 10–5 mbar. The films are morphologically, structurally, electrically and opto-electronically investigated. Having identified the work function of p-MgSe as 6.74 eV, the role of Ag, C, Au and Pt metal contacts on the performance of the n-Si/ p-MgSe (SM) diodes are studied. It is observed that high rectification ratios of?104 and 102 are achieved at an applied voltage of 3.0 V for the Ag/SM/C and Ag/SM/Ag diode structures, respectively. In addition, a current responsivity to visible and infrared light of?0.70 A W?1 is observed for the Ag/SM/Ag channels. The noise equivalent ratios, the external quantum efficiency and the detectivity of the Ag/ SM/Ag diodes suit requirements of visible light and infrared communication detectors. Moreover, studies of the capacitance-voltage characteristics showed capacitor characteristics. The depleting of the Ag/SM/Ag capacitors is possible up to 50 MHz. Furthermore, analyzing the capacitance, resistance and cutoff frequency spectra have shown that the Ag/SM/Ag device channels can perform as negative resistance sources with cutoff frequency values that suits 6G technology requirements.
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    Enhanced properties of indium thin films by stacking with platinum nanosheets designed for advanced terahertz/ gigahertz applications
    (Optical and Quantum Electronics, 2023) Almotiri, R. A.; Qasrawi, Atef Fayez
    Herein stacked layers of metallic indium (150 nm) and platinum (50–250 nm) thin films are fabricated as a terahertz/gigahertz filters. Indium thin films are produced by the thermal evaporation technique under a vacuum pressure of 10? 5 mbar and coated with Pt nanosheets using the ionic coating technique. It is observed that Pt nanosheets increased the light transmittance and reflectance in In/Pt films. In/Pt stacked layers displayed lower; dielectric constant, optical conductivity and terahertz cutoff frequency values as compared indium thin slabs. In/Pt stacked layers is found appropriate as tunable terahertz filters. In addition, the Drude-Lorentz analyses on these optical layers have shown that In/Pt stacks exhibit plasmon frequency values (8.7–17.3 GHz) that make them suitable for 5G/6G technology as band filters. The optical conductivity parameters including the drift mobility, free electron density and scattering time at femtosecond level are also determined. As a confirming technique an ac signals propagating with driving frequency in the range of 0.01–0.50 GHz is imposed between the terminals of In/Pt stacked layers. It is shown that the microwave cutoff frequency is widely tunable achieving values of 40 GHz at driving frequency of 0.50 GHz. The features of the In/Pt stacked layers are promising as they show properties of tunable terahertz/gigahertz filters.
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    Enhancement of the electrical properties of Au/MgSe/Au microwave resonators via pulsed laser welding of MgSe and Au nanosheets
    (Springer, 2023) Almotiri, R. A.; Qasrawi, Atef Fayez; Agha, B. S.
    Herein, stacked nanosheets of Au (50 nm) and MgSe (100 nm) are fabricated by the thermal evaporation technique and welded by pulsed lasers of wavelengths of 1064 nm within few seconds. Au/MgSe (AMA) and welded Au/MgSe (PLW) interfaces are coated with another Au point contact and employed as microwave resonators. It is observed that both AMA and PLW devices are of amorphous structure. The laser welding technique resulted in formation clusters composed of very dense grains of Mg1.37AuSe1.18 and other clusters composed of Mg1.16Se. In addition, the impedance spectroscopy measurements on these nano-thick devices have shown their novel ability to perform as negative capacitance sources and as band-stop filters. The pulsed laser welding of these microwave resonators increased their ac conductivities by increasing the hopping sites in the devices. The density of localized states near the Fermi level is increased by ~ 21% and the scattering time constant between hopping sites is shortened via laser welding. As microwave resonators, the pulsed laser welding process shifted the notch frequency from 1.0 to 2.16 GHz, improved the negativity of the capacitance, increased the return loss values and lowered the voltage standing wave ratios to 1.0. The features of the AMA microwave resonators before and after the pulsed laser welding nominate them for use as band-stop filters and as negative capacitance sources.
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    Formation and characterization of MgSe alloys by pulsed laser welding technique
    (Wiley, 2023) Almotiri, R. A.; Qasrawi, Atef Fayez
    Herein, MgSe alloys with different compositions are fabricated using laser welding techniques within a couple of minutes in an argon atmosphere. The optimum laser welding parameters, which reveal the correct compositional ratios, are determined by varying arc voltage, pulse width, welding frequency, and laser beam diameter. The structure of the MgSe alloy is monoclinic. Additionally, scanning electron microscopy studies have shown that MgSe alloys are least porous and have a layered structure. The electrical resistance of the welded alloys depends on the Mg content in the samples. Measurements from impedance spectroscopy have shown that the alloys can function as band filters, displaying cutoff frequency values of ?16 GHz for AC signals propagating at a driving frequency of 1.0 GHz with an amplitude of 0.10 V. The properties of the MgSe alloys make them attractive for use in 5G/6G technology applications as band filters.
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    Growth and characterization of vacuum evaporated MgSe thin films
    (Springer, 2023) Almotiri, R. A.; Qasrawi, Atef Fayez; Al Garni, Sabah E.
    Herein, thin flms of magnesium selenide are thermally grown in a vacuum deposition (VD) system onto glass substrates under a vacuum pressure of 10–5 mbar. The flms are structurally, morphologically, compositionally, and optically characterized. It is observed that MgSe thin flms coated by the VD technique are composed of polycrystalline MgSe1.07 (a=5.149 ?, space group Fm3m) and MgSe1.96 (a=6.514 ?, space group P3?a) cubic phases. The flms displayed an average roughness value of 13 nm. They also exhibited a direct energy band gap of 2.54 eV and an indirect band gap of 3.34 eV. In addition, detailed studies of the dielectric properties, optical conductivity, and terahertz cutof frequency spectra showed the ability of MgSe thin flms to perform as a dielectric material. High dielectric constant values are reached in the near-infrared range of light. As optical conductors, the flms displayed one IR, two visible, and two ultraviolet light oscillators showing a maximum plasmon frequency of 8.19 GHz in the UV range. The drift mobility of these oscillators varied in the range of 4.57–9.67 cm2 / Vs. Moreover, the terahertz cutof frequency for these oscillators varied in the range of 11–175 THz proofng the suitability of MgSe flms for terahertz technology issues.
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    ITO/MgSe interfaces designed as gigahertz/terahertz filters
    (IOP Science, 2023) Almotiri, R. A.; Qasrawi, A. F.
    Herein a new class of MgSe gigahertz/terahertz band filters operatives in the frequency domain of 1.0 GHz-1.86 THz is fabricated and experimentally tested. MgSe band filters are coated onto glass and indium tin oxide (ITO) substrates by the thermal evaporation technique under a vacuum pressure of 10-5 mbar. Thin films of MgSe are structurally, morphologically, compositionally, optically and electrically characterized. It is observed that ITO substrates induce the growth of monophasic of MgSe, enhances the crystallinity of the films and blueshifts the energy band gaps of MgSe. Practical applications were verified by impedance spectroscopy technique through imposing an ac signal of driving frequency in the domain of 10.0 MHz-1.8 GHz between the terminals of ITO/MgSe/Au (IMA) devices. It is observed that the IMA devices exhibit negative capacitance effect. Analysis of the cutoff frequency spectra has shown that IMA devices can reveal wide range of tunability in the gigahertz frequency domain. In addition, the cutoff frequency spectra show values reaching ~1.86 THz for signals of driving frequencies of ~1.0 GHz. Evaluation of the magnitude of the reflection coefficient spectra and return loss spectra for these devices show that the IMA devices can perform as bandstop filters with return loss values exceeding 20 dB at 1.0 GHz. The features of the ITO/MgSe/Au devices are appropriate for the 5G/6G technology needs indicating that the device can be employed in communication technology and other gigahertz/terahertz applications.
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    Optoelectronic performance of n?Si/p?MgSe heterojunctions as a visible light communication component
    (Elsevier B.V., 2022) Almotiri, R. A.; Qasrawi, Atef Fayez
    Herein magnesium selenide thin films coated onto glass and Si substrates are studied and characterized. The films, prepared by the thermal vacuum evaporation technique under a vacuum pressure of 10?5 mbar, are structurally, morphologically, compositionally, optically, and electrically investigated. While films grown onto glass substrates showed the existence of cubic phases of MgSe and MgSe2, films coated onto Si substrates contained SiSe2. Replacement of glass substrates by Si highly improved the crystallinity of the films. In addition, the optical analyses on the films grown onto Si substrates indicated the formation of Si/MgSe heterojunctions with valence and conduction band offsets of 0.95?eV and 0.40?eV, respectively. MgSe films are coated onto Si substrates and contacted with Ag contacts performed as photosensors suitable for vehicle visible light communications. The asymmetry (rectification ratios), the current responsivity, the noise equivalent power factor, and the detectivity of the devices reached 517, 0.73?A/W, 5.93W/Hz1/2 and 5.8 Jones, respectively, at 4.3?V.