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Öğe Band offsets, dielectric dispersion and some applications of CdSe/GeO2 heterojunctions(Elsevier GmbH, 2021) Khusayfan, Najla M.; Qasrawi, Atef Fayez; Alharbi, S. R.; Khanfar, Hazem K.; Kayed, T. S.Herein, the formation, structural, morphological, compositional, optical, dielectric, photoelectrical and electrical properties of the CdSe/GeO2 heterojunctions are explored. While the surface displayed formation of deficient GeO, the bulk of the films exhibited correct stoichiometry of GeO2 and CdSe. It is found that stacking of GeO2 onto CdSe enhances the crystallinity of CdSe by reducing the defects concentrations. It blue shifts the energy band gap of CdSe from 1.74 eV to 2.60 eV. The stacked layers of CdSe/GeO2 displayed conduction and valence band offsets of 2.34 eV and 1.23 eV, respectively. In addition, the Drude-Lorentz model analyses have shown that the coating of GeO2 onto CdSe, highly increases the drift mobility of charge carriers and tunes the plasmon frequency making it more appropriate for optoelectronic device applications. When exposed to light irradiation, an illumination intensity dependent photosensitivity is observed. The photoconduction mechanism is governed by the sublinear recombination with exponential trap distribution. Moreover, the capacitance –voltage characteristics of the device revealed metal-oxide-semiconductor field effect transistors (MOSFET) characteristics. The built in potential for this device under reverse biasing conditions reached 4.74 eV.Öğe 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.Öğe 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.Öğe Enhanced Optical and Electrical Interactions at the Pt/MgSe Interfaces Designed for 6G Communication Technology(Wiley, 2022) Algarni, Sabah E.; Qasrawi, Atef Fayez; Khusayfan, Najla M.Magnesium selenide thin films are coated onto glass and semitransparent Ptsubstrates (nanosheets) by the vacuum evaporation technique under avacuum pressure of 10?5mbar. The effect of Pt nanosheets of thicknesses of100 nm on the structural, compositional, optical, and electrical properties ofMgSe is explored. It is found that platinum nanosheets enhance the lightabsorbability in the visible and infrared ranges of light. They slightly redshiftthe energy bandgap and decrease the dielectric constant. The stronginteraction between Pt and MgSe increases the electrical conductivity by fiveorders of magnitude. Pt forms shallow impurity levels in the energy bandgapof MgSe allowing the tunneling process at the Pt/MgSe interfaces. Practically,a Pt/MgSe/Pt tunneling type device is fabricated and tested by the microwaveimpedance spectroscopy technique. It is found that Pt/MgSe/Pt devices canexhibit resonance–antiresonance and negative capacitance effects which areimportant in electronic circuits as parasitic capacitance cancelers, signalamplifiers, and noise reducers. In addition, evaluation of the cutoff frequencyspectra has shown the ability of using the Pt/MgSe/Pt devices as microwaveresonators appropriate for 5G/6G technologies. A cutoff frequency larger than70 GHz can be achieved by imposing ac signal of amplitude of 0.10 V.Öğe Fast crystallization of InSe thin films via pulsed laser welding technique and effect of crystallinity on the optical and dielectric properties(IOP Publishing, 2024) Khusayfan, Najla M.; Qasrawi, Atef Fayez; Khanfar, Hazem K.; Alharbi, Seham R.Physica Scripta Inclusive Publishing Trusted Science, find out more. ACCEPTED MANUSCRIPT Fast crystallization of InSe thin films via pulsed laser welding technique and effect of crystallinity on the optical and dielectric properties Najla M. Khusayfan1, A F Qasrawi2, Hazem Khanfar3 and Seham Alharbi4 Accepted Manuscript online 18 January 2024 • © 2024 IOP Publishing Ltd What is an Accepted Manuscript? DOI 10.1088/1402-4896/ad2040 DownloadAccepted Manuscript PDF Download PDF Article metrics 3 Total downloads Submit Submit to this Journal MathJax Turn on MathJax Permissions Get permission to re-use this article Share this article Share this content via email Share on Facebook (opens new window) Share on Twitter (opens new window) Share on Mendeley (opens new window) Hide article and author information Author e-mails atef.qasrawi@aaup.edu Author affiliations 1 Department of Physics, University of Jeddah, Jeddah, Jeddah, Makkah, 21959 , SAUDI ARABIA 2 Physics Department, Arab American University, Telfit,, Jenin, P298, Palestine, State of 3 Computer system Engineering , Arab American University, Telfit,, Jenin, Jenin, P298, Palestine, State of 4 Physics Department, University of Jeddah, jeddah, Jeddah, Makkah, 21959 , SAUDI ARABIA ORCID iDs A F Qasrawi https://orcid.org/0000-0001-8193-6975 Hazem Khanfar https://orcid.org/0000-0002-3015-4049 Dates Received 5 October 2023 Revised 17 December 2023 Accepted 18 January 2024 Accepted Manuscript online 18 January 2024 Journal RSS Sign up for new issue notifications Abstract In the current study the crystalline phase of indium selenide thin films which were grown by the thermal evaporation technique is achieved via pulsed laser welding technique (PLW) in a second. The films crystallinity is achieved under various welding conditions including the pulse width (PW), repetition frequency (f_r ) and pulse diameter (d). The optimum parameters for obtaining well crystalline phase are PW=1.0 ms, f_r=10Hz and d=1.0 mm. PLW induced crystallinity showed preferred structure relating to monoclinic phase of InSe. Compositionally while amorphous films exhibited In2Se3 chemical structure, crystalline ones preferred InSe phase. Associated with this type of crystallinity, direct and indirect energy band gap values of 2.32 eV and 3.12 eV are determined. The crystalline films showed lower dielectric constant value accompanied with higher optical conductivity and higher terahertz cutoff frequency in the infrared range of light. In addition the dielectric dispersion spectra were treated using Drude-Lorentz model to read the optical conductivity parameters for the PLW assisted crystalline InSe terahertz resonators. The treatment showed that the crystallinity of the films resulted in improved free carrier density, longer relaxation times at femtosecond level, larger plasmon frequencies and higher drift mobility values. These features together with the response of terahertz cutoff frequency to IR excitations make crystalline InSe thin films promising for optoelectronic and terahertz technology applications.Öğe Growth of Polycrystalline n? CrSe2 Nanosheets Onto p –Si Substrates and their Applications as Rectifiers and Gigahertz Band Filters(Springer, 2024) Algarni, Sabah E.; Qasrawi, Atef Fayez; Khusayfan, Najla M.a vacuum evaporation technique under a vacuum pressure of 10– 5 mbar. Experimental and theoretical structural investigations have shown the preferred growth of trigonal CrSe2. The unit cell parameters being a = b = 3.520 Å,c = 5.889 Å and P3m1(164) fits well with the standards of trigonal CrSe2 structure. Nanosheets of chromium selenide displayed low defect density of the order of 1010 lines/cm2 along the a? and b axes. Surface morphology studies have shown that CrSe2 nanosheets is composed of spherical grains of average sizes of 200 nm. Optically the interfacing of the n– type CrSe2 nanosheets with p? type Si results in formation of a conduction and valence band offsets of 0.95 eV and 0.47 eV, respectively. These band offsets were found sufficient to allow running the Si/CrSe2 interfaces as pn junction devices. The devices displayed a biasing dependent rectification ratios (asymmetry). The ratios which reached value of 70 can be varied with the applied voltage. Deep analyses of the current transport mechanism of these rectifiers have shown the domination by thermionic and tunneling mechanisms under forward and reverse biasing conditions, respectively. Moreover the pn junction device showed features of band filters with cutoff frequency values suiting gigahertz technology making the device attractive for multifunction operations.Öğe Hydraulic pressure and temperature efects on the structural, morphological and electrical properties of SeO2 powders(Springer Link, 2022) Algarni, Sabah E.; Qasrawi, Atef Fayez; Khusayfan, Najla M.Herein, powders of SeO2 are subjected to hydraulic pressure in the range of 1.0–12 MPa and heating cycles in the range of 290–383 K. The pressure and temperature effects on the crystalline nature, plane orientations, structural parameters, surface morphology, composition, electrical resistivity, capacitance spectra and conductance spectra are explored. It is observed that hydraulic pressure value of 6.0 MPa is a critical value at which the tetragonal SeO2 grains prefer (020) plane orientation over (011) planes. The (020) plane orientations resulted in remarkable changes in the lattice parameters, structural parameters, electrical resistivity, capacitance and conductance spectra. In addition, the heating and cooling cycles of the samples pressed at 10 MPa have shown that the transition of the planes is permanent. The heated and cooled pellets displayed resonance–antiresonance in the capacitance spectra near 0.43 GHz. The resonance–antiresonance phenomena are accompanied with negative conductance effect near 0.43 GHz. The enhancements in the properties of SeO2 powders that are achieved via pressure and temperature effects make them appropriate for electronic circuit technological applications.Öğe InSe/CrSe interfaces performed as resistive switches and band filters for Gigahertz/Terahertz communication technology applications(Springer, 2024) Algarni, Sabah E.; Qasrawi, Atef Fayez; Khusayfan, Najla M.Herein chromium selenide (n-CrSe) nanosheets are deposited onto amorphous indium selenide (n-InSe) thin films by the thermal evaporation technique under a vacuum pressure of 10?5 mbar. The formed InSe/CrSe heterojunctions are structurally, optically and electrically investigated. InSe/CrSe heterojunctions exhibited a band structure discontinuities at the InSe/CrSe interfaces presented by a conduction and valence band offsets of 0.50 eV and 0.65 eV, respectively. The isotype InSe/CrSe heterojunctions exhibited resistive switching property under a forward and reverse biasing voltages of 1.5 V and 0.3 V, respectively. In addition computer assisted fittings which were carried out on the current–voltage characteristics of the InSe/CrSe devices have shown the existence of large barrier height of 1.75 eV at the InSe/CrSe interfaces. Moreover, low amplitude ac signal analyses have shown that the device under study performed as negative conductance sources with increased negative conductance values with increasing signal frequency. The negative conductance effect resulted from the deficiency of selenium atoms in InSe and CrSe as confirmed by the energy dispersive X-ray spectroscopy. Furthermore combination of the analysis of the picofarad level- capacitance with the conductance allowed determining the cutoff limits of the InSe/CrSe devices when treated as signal filters. The cutoff frequency of the InSe/ CrSe devices varied in the range of 10M-1.1 THz assuring the suitability of the devices for megahertz/gigahertz/terahertz technology applicationsÖğe Lead selenide thin films designed for laser sensing and visible light communications(Springer, 2023) Khusayfan, Najla M.; Qasrawi, Atef Fayez; Khanfar, Hazem K.; Alharbi, Seham R.Herein thin films of PbSe are coated onto amorphous glass, amorphous silicon (a?Si) and crystalline n?type Si (n?Si) wafers by the thermal evaporation technique under a vacuum pressure of 10? 5 mbar. The films are structurally, morphologically, compositionally, optically and electrically characterized. Strong effect of the nature (amorphous or crystalline) and type (Si or glass) of the substrate on the physical properties of lead selenide films is detected. Of these properties the crystallite sizes decreased and the microstrain, the stacking faults and defect density increased and the energy band gap is blue shifted when (a, n)-Si substrates replaces glass. In addition, the use of crystalline n?Si substrates instead of a?Si removed the free carrier absorption from a?Si/ p?PbSe improving the quantum efficiency of the devices. Opto-electronically, n?Si/p?PbSe films showed photosensor characteristics that suit both visible light and infrared technology applications. The photosensors displayed high current responsivity, external quantum efficiency percentages and response times reaching respective values of 1.4 A/W, 172% and 60 ?s. In addition, the n?Si/p?PbSe photosensors which were used as detectors to receive wireless light signals generated from light pulses of 10 kHz frequencies showed smart features nominating them as promising devices for laser sensing and visible light communication technology.Öğe p-Si/n-CrSe2 Heterojunctions Designed as High-Frequency Capacitors and Photosensors(Springer, 2024) Algarni, Sabah E.; Qasrawi, A. F.; Khusayfan, Najla M.; Alharbi, Seham R.; Alfhaid, Latifah Hamad KhalidIn this work, polycrystalline n-CrSe2 nanosheets with thickness of 100 nm are grown on p-type Si wafers by the thermal deposition technique under vacuum pressure of 10(-5) mbar. Structural and optical investigations showed the preferred growth of the trigonal phase of CrSe2 on Si substrates. Direct allowed transitions within an energy band gap of 2.60 eV were found to be dominant in the films. Silver contacts on the layers allowed construction of hybrid optoelectronic device structure formed from Ag/p-Si Schottky arm and p-Si/n-CrSe(2)pn junction. The device runs in such a way that forward biasing of the Schottky arm is accompanied by a reverse biasing of the pn junction. It is observed that the hybrid device structure can perform as a high-frequency capacitor. The capacitance-voltage characteristic curves show that these capacitors can respond to ac signals with frequencies of 100 MHz. They also exhibit bandstop filter characteristics allowing the passing of signals with return loss and voltage standing wave ratios exceeding 10 dB and 1.76, respectively, at 60 MHz. The device under study displayed rectifying and photo-sensing properties with an asymmetry ratio of 60 in the dark and 217 under excitation of visible light. Visible light excitation of these photosensors displayed voltage biasing dependence in their current responsivity, external quantum efficiency and specific detectivity, reaching values of 0.24 A/W, 65.2% and 4.83 x 10(9) Jones, respectively. The features of the hybrid devices which use CrSe2 nanosheets as active media make them good candidates for use in radio wave and visible light communication technologies.
