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Öğe 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.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 Enhanced performance of Pb/FeSe2 interfaces designed for electrical applications(Springer, 2024) Alharbi, Seham R.; Qasrawi, Atef Fayez; Algarni, Sabah E.In this work, iron selenide layers are deposited onto glass and lead substrates to perform as terahertz filters. The layers are deposited by the thermal evaporation technique under a vacuum pressure of 10–5 mbar. Glass/FeSe2 (GFS) and Pb/FeSe2 (PFS) films are structurally, morphologically and electrically characterized. The atomic composition of the GFS films contained excess selenium that reacted with Pb forming a PbSe layer. This layer induced the crystallinity of iron selenide. The preferred crystal structure of FeSe2 was cubic with cell parameters of a = b = c = 3.04 Å and space group Pm3m . Lead substrates increased the room temperature electrical conductivity of GFS films from of 1.52 ×10?5(?cm)?1 to 6.88 ×10?2(?cm)?1 . Analyses of the electrical conduction mechanism in the temperature range of 25–330 K have shown that coating the films onto Pb substrates shifted the accepter level from 182 to 58 meV, decreased the degree of structural disor-der, shorten the average hopping range from 59 to 19 Å and increased the density of localized states near Fermi level by two orders of magnitude. The conductivity of PFS films exhibited degenerate semiconductor characteristics in the temperature range of 120–28 K. This feature is followed by an evidence of exhibiting superconductivity at critical temperatures lower than 24 K. On the other hand the impedance spectroscopy measurements in the driving signal frequency domain of 0.01–1.0 GHz have shown that Pb/FeSe2/Ag interfaces can perform as band filters showing microwave cutoff frequency values reach-ing 100 GHz at driving signal frequency of 1.0 GHz. These band filters are ideal for 6G technology nominating PFS films for high frequency applications.Öğe Growth and characterization of (glass, Ag)/SeO2 thin films(Elsevier, 2022) Alharbi, Seham R.; Qasrawi, Atef Fayez; Algarni, Sabah E.Herein, thin films of SeO2 coated onto glass and Ag thin film substrates are studied and characterized. The films which are prepared by a vacuum evaporation technique, displayed Ag-metal induced crystallization process. The grown films are composed of tetragonal structure of SeO2 as major phase and orthorhombic as minor phase. The optical studies showed that the films exhibit an energy band gap of 3.69 eV. In addition, the analyses of the dielectric dispersion spectra indicated the nonlinear character of dielectric response. The SeO2 films response to oscillatory electromagnetic field is accompanied with drift mobility values in the range of 5.02–12.06 cm2/Vs. Moreover, polycrystalline SeO2 films coated onto Ag substrates are found appropriate for use as negative capacitance (NC) sources in the frequency domain of 0.41–1.80 GHz. Accompany with the NC effect, negative conductance (NG) effect was observed near 0.410 GHz and near 1.53 GHz.Öğe Growth and characterization of PbSe microcrystals via the pulsed laser welding technique(SPRINGER HEIDELBERG, 2022) Alkhamisi, Manal M.; Khanfar, Hazem K.; Algarni, Sabah E.; Qasrawi, Atef FayezHerein lead selenide crystals are fabricated by the pulsed laser welding (PLW) technique within 2 min. The effect of the pulse width on the crystallinity, surface morphology, structural parameters, compositional stoichiometry, electric resistivity and dielectric constant is considered. It is observed that the PLW technique allowed the growth of the crystals in a short period of time. The grown PbSe crystals are mostly cubic containing tetragonal SeO2 as a minor phase. Selenium oxide presented due to the surface oxidation of PbSe after exposing the crystals to air. Remarkable decreases in the electrical resistivity and increase in the dielectric constant by more than two orders of magnitude are achieved as the pulse width increases from 10 to 50 ms. It is observed that the optimum pulse width revealing the highest dielectric constant value is 30 ms. For these samples, a negative capacitance effect is observed for ac signals of frequencies larger than 700 MHz. In addition, analyzing the microwave cut-off frequency spectra for an imposed signal of low amplitude displayed cut-off frequency values larger than 100 GHz at the point where negative capacitance dominates and ac conductance shows a maxima. The features of the PbSe crystals which are prepared in 2 min nominate them for use as negative capacitance sources and band filters suitable for 6G technologies.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 High-performance n – Si/p – SeO2 /p – SiO2 heterojunction photodetectors for potential application in visible light communication technology(Springer, 2023) Alharbi, Seham R. N.; Qasrawi, Atef Fayez; Algarni, Sabah E.Photodetectors suitable for visible light communication (VLC) technology were fabricated and characterized in this study. The photodetectors were designed using two p-type stacked layers of SeO2 and SiO2, which were coated onto n? type Si thin wafers. These stacked layers were deposited in a vacuum medium under a pressure of 10–5 mbar using the thermal evaporation technique. p-SiO2 thin layer enriched the hole concentration of p-SeO2 layer forming p+n type heterojunction and prevented SeO2 from environmental contaminations. The microstructure, surface morphology, and photoelectrical properties of the n-Si/p-SeO2/p-SiO2 (SSS) detectors were explored. It was observed that the SSS detectors exhibited biasing and light power dependent asymmetry. The asymmetry varied in the range of 77–178 as the light power increased from zero to 77 mW. In addition, the SSS photodetectors demonstrated a current responsivity, external quantum efficiency, and specific detectivity reaching values of 123 mA/W, 15.6%, and 1.3?×?1010 Jones, respectively. These values are considered adequate for VLC technology. Practical tests have shown that the device can transmit wireless square-wave pulses with frequencies up to approximately 10–100 kHz. The growth and decay response times were found to be 1.15 ms and 0.89 ms, respectively. The features of the SSS detectors make them suitable for use as light-controlled current rectifiers and VLC detectors.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 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.Öğe Pb/FeSe interfaces designed for optical communication technology(Wiley, 2023) Alharbi, Seham R.; Qasrawi, Atef Fayez; Algarni, Sabah E.Herein, thin films of FeSe are coated onto glass and semitransparent Pb substrate of thicknesses of 200 nm. The produced glass/FeSe (GFS) and Pb/FeSe (PFS) are structurally, compositionally, and optically characterized. It is observed that Pb substrates induced the crystallinity of cubic FeSe and cubic PbSe. On average, 21% of the phases in FeSe films are identified as PbSe. Due to the strong orbital overlapping between Pb and FeSe, Pb substrate increases the light absorption, the dielectric constant, the optical conductivity, and the terahertz cutoff frequency by ?150 %, 180 %, 263 %, and 101 %, respectively. In addition the direct and indirect energy bandgaps shrink from 2.49 and 2.80 to 2.41 and 2.50 eV, respectively. Moreover, treating GFS and PFS as terahertz optical resonators have shown that Pb substrates enhanced the drift mobility and increased the plasmon frequency making it adequate for 6G technology applications. An important feature of the PFS optical resonator is the stability of the terahertz cutoff frequency at 16 THz in the visible range of light. This feature together with the enhanced optical absorption in the visible light region makes the PFS films attractive for visible light communication technology.Öğe Pt/PbSe optoelectronic receivers designed for 6G and terahertz communication technologies(SPRINGER, 2023) Alkhamisi, M.M; Qasrawi, Atef Fayez; Khanfar, Hazem K.; Algarni, Sabah E.Herein PbSe thin films are coated onto glass and semitransparent platinum substrates. The films which are treated as optoelectronic signal receivers are deposited by the thermal evaporation technique under a vacuum pressure of 10?5 mbar. The structural investigations have shown that (glass, Pt)/PbSe films are of polycrystalline nature. Optically, Pt substrates increased the transparency and reflectivity of PbSe films. The energy band gap of PbSe is also increased by 0.12 eV when films are coated onto Pt substrates. In addition the dielectric constant also increased as a result of strong interaction between Pt plasmonic particles and lead selenide. On the other hand, fitting of the imaginary part of the dielectric constant using Drude–Lorentz model has shown that coating of PbSe onto semitransparent Pt substrates increased the drift mobility of lead selenide by four times. Pt substrates resulted in a decrease in the density of free charge carriers and increases the scattering time constant at femtosecond levels. (Glass, Pt)/PbSe optoelectronic receivers displayed plasmon frequencies up to?~?13 GHz and showed terahertz cutoff frequency of?~?1.0 THz. In addition, allowing the propagation of an ac signal of low amplitude in the Pt/PbSe/Pt receivers has shown that the devices exhibit wide range of resistance tunability. The microwave cutoff frequency also reached 14 GHz. Both of the optical and electrical measurements proved the suitability of the Pt/PbSe devices for 6G and terahertz communication technologies.Öğe Selenium oxide based laser sensors designed for optoelectronic applications(Springer, 2023) Alharbi, Seham R. N.; Qasrawi, Atef Fayez; Algarni, Sabah E.In this study, stacked layers of p? SeO2 and p? SiO2 were formed onto n? type silicon wafers to act as laser photosensors. The p? type stacked layers were fabricated using the thermal evaporation technique under a vacuum pressure of 10–5 mbar. Ag and Au thin films were used as Schottky contacts for p? SiO2 and n? Si, respectively. The energy band diagram of the device showed the presence of large conduction and valence band offsets that were sufficient for electron–hole separation. Practical tests using current–voltage characteristics indicated that in the dark, current transport was mostly dominated by diffusion and Richardson Schottky types of current conduction. These transport mechanisms led to a biasing-dependent rectification ratio, which increased by more than 149 times, 24 times, and ~?4 times under laser lights of wavelengths of 632 nm, 850 nm, and 1550 nm, respectively. The photosensors achieved high current responsivity (R˜ ) and external quantum efficiency (EQE %) reaching 0.54 A/W and 27.5%, respectively, under 632 nm-laser illuminations. The photosensors also showed acceptable values of R˜ and EQE % when irradiated with laser lights of wavelengths of 850 nm and 1550 nm. The proposed devices exhibited features such as a rectification ratio up to 104 and specific detectivity of ~?1010 Jones under laser light, making them suitable for wireless communication technology.
