Yazar "Qasrawi, Atef Fayez" seçeneğine göre listele
Listeleniyor 1 - 20 / 79
Sayfa Başına Sonuç
Sıralama seçenekleri
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 Amorphous WO3 thin films designed as gigahertz/terahertz dielectric lenses(Springer Link, 2022) Qasrawi, Atef Fayez; Abu Alrub, Shatha N.; Daragme, Rana B.Herein, tungsten oxide thin films comprising excess oxygen are treated as optical resonator suitable for gigahertz/terahertz applications. WO3 thin films which are prepared by the thermal evaporation technique under a vacuum pressure of 10? 5 mbar are structurally, compositionally and optically evaluated. The amorphous WO3 films which showed high transparency permit electronic transitions within an indirect allowed energy band gap of 3.05 eV. The band gap comprised energy band tails of width of 190 meV. Four dominant dielectric resonators centered in the infrared (IR), visible (VIS) and ultraviolet (UV) ranges of light are detected. Analysis of the optical conductivity in accordance with the Drude-Lorentz approaches have shown that the drift mobility of free holes in this amorphous layer can be as large as 5.61 cm2/Vs an as low as 1.59 cm2/Vs when exposed to IR and UV light signals, respectively. In addition, the gigahertz/terahertz cutoff frequency (fco) spectra demonstrated fco values in the gigahertz frequency domain when exposed to IR light. Excitations with light signals in the VIS and UV spectral ranges allow fco values that extends from 0.7 to 40.0 THz. The wide range of tunability of the WO3 dielectric resonators nominates them as dielectric lenses suitable for optical communications.Öğe Au nanosheets-assisted structural phase transitions, in situ monitoring of the enhanced crystallinity, and their effect on the optical and dielectric properties of CuSe/Au/CuSe thin films(Wiley, 2022) Qasrawi, Atef Fayez; Baniowdah, Tahani S.; Samen, Lara O. AbuHerein, stacked layers of copper selenide thin films comprising Au nanosheets in its structure are fabricated and characterized. The CuSe/Au/CuSe (CAC) thin films are prepared by the thermal evaporation technique under a vacuum pressure of 10?5 mbar. It is shown that Au nanosheets improve the stoichiometric growth of the CuSe thin films and induce the structural phase transitions from cubic to hexagonal. In addition, the in situ monitoring of the structural modifications in the CAC in the temperature range of 293–473 K proves the permanent enhanced crystallinity of the films. Optically, while the Au nanosheets increase the light absorbability and redshifts the energy band gap of CuSe, the in situ heating blueshifts the energy band gap. Moreover, insertion of Au nanosheets between layers of CuSe and heating them at 473 K significantly increase the dielectric constant and the optical conductivity by more than five times. Moreover, the drift mobility of charged carriers, the scattering time at femtosecond level, and the plasmon frequency are remarkably enhanced. Values of plasmon frequency exceed 6.0 GHz nominating the CAC films as signal receivers suitable for 5G technology.Öğe Au/CdBr2/SiO2/Au Straddling-Type heterojunctions designed as microwave multiband pass filters, negative capacitance transistors and current rectifiers(Wiley, 2021) Qasrawi, Atef Fayez; Hamarsheh, Areen A.Herein, nanosheets of SiO2 of thicknesses of 25-100 nm are employed to enhance the performance of Au/CdBr2 Schottky barriers. The Au/CdBr2/SiO2/Au straddling type heterojunction devices is prepared by the thermal evaporation technique. It is observed that SiO2 layers enhances the crystallinity of CdBr2 through increasing the crystallite sizes and decreasing the defect density, stacking faults and microstrain by 50%, 56%, 32% and 34%, respectively. A work function of 6.38 eV is determined from the temperature dependent electrical resistivity measurements of p?type CdBr2. In addition, it was observed that, when coated with 50 nm thick SiO2, the Au/CdBr2/SiO2/Au straddling type transistors can reveal high current rectification ratios of 6.9× 102 at low biasing voltages in the range of 0.06-0.30 V. The alternating current signals analysis in the microwave range of spectra indicated that the current conduction mechanism is dominated by the correlated barrier hopping and quantum mechanical tunneling. It was observed that the Au/CdBr2/SiO2/Au devices exhibit negative effect accompanied with resonance-antiresonance in the capacitance spectra. Moreover, the microwave cutoff frequency which reaches ~165.1 GHz and the magnitude of reflection coefficient spectra has shown that the device under study can perform as multiband pass/stop filters suitable for wire/wireless communication applications including 3G/4G technologies.Öğe Au/CrSe stacked layers designed as optical absorbers, tunneling barriers and negative capacitance sources(Elsevier, 2023) Alfhaid, Latifah Hamad Khalid; Qasrawi, Atef FayezHerein thin films of CrSe (500 nm) are deposited onto glass and semitransparent gold nanosheets (100 nm) under a vacuum pressure of 10?5 mbar. Au nanosheets substrates induced the formation of CrSe instead of CrSe2 which grows onto glass substrates. The Au/CrSe stacked layers exhibited enhanced light absorption reaching 25% in the ultraviolet, visible and infrared ranges of light. In addition Au nanosheets successfully redshifted the direct allowed transitions energy band gap from 2.60 eV to 2.40 eV. On the other hand electrical investigations have shown that CrSe2 thin films exhibit a work function of 5.064 eV. The Au/CrSe interfaces displayed tunneling type Schottky barriers of height of 0.56 eV and barrier width of 8 nm. When an ac signal was imposed between the terminals of the Au/CrSe Schottky barriers a negative capacitance (NC) effects was observed in the spectral range of 0.02–1.80 GHz. The NC reached value of ? 100 pF at 0.32 GHz. Fitting of the ac conductivity assuming tunneling type of transport indicated a high degree of localization near the Fermi level reaching a density of cm?3 eV?1. The enhanced light absorption and moderate value of work function in addition to the tunneling type of Schottky formation performing as NC source make the Au/CrSe interfaces promising for use in the design of electro-optic system.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 Band offsets, dielectric dispersion, optical conduction and impedance spectroscopy analyses of WO3/ Ga2S3 heterojunctions(Springer, 2022) Qasrawi, Atef Fayez; Abu Alrub, Shatha N.Stacked layers of amorphous WO3 and Ga2S3 are fabricated by the thermal evaporation technique under a vacuum pressure of 10– 5 mbar. The structural, compositional, optical, dielectric and electrical properties of the WO3/ Ga2S3 (WG) heterojunctions are investigated. It is observed that the WG heterojunctions exhibit well-aligned conduction bands. The valance band offsets are 0.58 eV. In addition, as a dielectric resonator, WG interfaces displayed single infrared oscillator, double ultraviolet (UV) oscillators and triple visible light oscillators. The optical conductivity modeling by the Drude–Lorentz approach has shown that for these oscillators the drift mobility of charge carriers is 7.52, 9.40 and 18.80 cm2/ Vs, respectively. The optical conductivity in the ultraviolet range is very high nominating the WG interfaces for UV sensing. On the other hand, the impedance spectroscopy analysis for the Yb/WG/C interfaces revealed the wide tunability of the devices when employed as capacitors and as bandpass filters. The WG interfaces can perform as radiowave/microwave band filters. The microwaveÖğe Band offsets, electron affinities and optical dynamics at the CdBr2/SiO2 interfaces(Elsevier, 2021) Qasrawi, Atef Fayez; Hamarsheh, Areen A.Indexed keywords Funding details Abstract Herein, the structural, optical, dielectric and optical conductivity parameters of the CdBr2/SiO2 interfaces are reported. Thin films of CdBr2 are coated with 50 nm thick SiO2 under a vacuum pressure of 10?5 mbar. The structural morphological and optical investigations have shown that CdBr2 exhibit hexagonal structure of lattice parameters of a=b=7.20Å and =13.86 Å, energy band gap of 3.32 eV and Urbach energy of 0.84 eV. The interfacing of CdBr2 films with SiO2, shortened the lattice parameters, blue-shifted the energy band gap and decreased the Urbach energy value. The electron affinity of CdBr2 which is determined here is found to be 3.27 eV. The CdBr2/SiO2 interfaces displayed a conduction and a valence band offsets of 2.37 eV and 3.21 eV, respectively. In addition, the dielectric dispersion and optical conduction analyses using the Drude-Lorentz approach have shown that the drift mobility and plasmon frequency (Wpi) of the free charge carriers at the CdBr2/SiO2 interfaces varies in the range of 28.59–22.87 cm2/Vs and 0.41–6.47 GHz, respectively. The effectiveness of the plasmon frequency to limit signal propagation in the heterojunction devices is confirmed by the impedance spectroscopy technique which showed radiowave (RF) band filter characteristics at the targeted Wpi. The energy band offsets, the optical conductivity parameters and the RF filtering properties nominates the CdBr2/SiO2 heterojunctions for use in thin film transistor technology.Öğe 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.Öğe Characterization of PbWO4 thin films formed by the pulsed laser welding technique(Elsevier, 2023) Alfhai, Latifa Hama Khalid; Qasrawi, Atef Fayez; Khanfar, Hazem K.within couple of seconds in an argon atmosphere. Thin films of Pb (100 nm)/WO3 (500 nm) were deposited by the thermal evaporation technique under a vacuum pressure of 10?5 mbar. The films were then exposed to a pulse laser beam of fixed amplitude and variable pulse width (0.1–10 ms). The produced films were characterized by means of X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and optical spectrophotometry techniques. An almost pure phase (~90%) of tetragonal PbWO4 was achieved after the pulse width exceeds 5.0 ms. PbWO4 thin films produced by the PLW technique exhibited a direct and indirect energy band gaps of 2.27 eV and 3.52 eV, respectively. Energy band tails of widths of 1.35 eV were found dominant in these films. In addition fitting of the dielectric resonance spectra for Pb/WO3 and PbWO4 thin films indicated that the formation of PbWO4 was accompanied with a decrease in the high frequency dielectric constant, a decrease in the free hole concentration and an increase in the electronic friction in the films. The fast method of obtaining PbWO4 thin films and the formation of the direct band gap being 2.27 eV together with the nonlinear dielectric and optical properties make the PbWO4 films obtained by the PLW technique suitable for optoelectronic technologyÖğe Copper doping effects on the optical and dielectric properties of amorphous indium selenide thin films(Springer, 2023) Qasrawi, Atef Fayez; Aboalrub, Fatima M.(a-InSe) thin films were doped with copper using the thermal evaporation technique under a vacuum pressure of 10– 5 mbar. The aim was to investigate the impact of Cu doping on the optical absorption, energy band gap, dielectric dispersion, optical conduction, and terahertz cutoff frequency. Notably, Cu doping levels of 1.41 at.% and 2.97 at.% in a-InSe resulted in a significant enhancement in light absorption by more than three and four times, respectively, without significantly altering the energy band gap. Furthermore, Cu doping led to a remarkable increase in the dielectric constant value and caused a redshift in the position of the dielectric resonance peak. Moreover, a noticeable enhancement in the optical conductivity and terahertz cutoff frequency values was observed in a-InSe films doped with 2.97 at.% of Cu. The Drude-Lorentz fittings of the optical conductivity data demonstrated that the presence of Cu atoms increased the scattering time at the femtosecond level and enhanced the drift mobility from ~ 5.0 cm2/ Vs for undoped films to ~ 113 cm2/ Vs for 2.97 at.% Cu-doped films. Additionally, the range of the terahertz cutoff limit expanded, covering a range of 0.1–16 THz. The study indicate that the features exhibited by Cu-doped InSe hold promise for various optoelectronic applications including terahertz technologyÖğe Design and characterization of (Yb, Al, Cu, Au)/GeO2/C As MOS field effect transistors, negative capacitance effect devices and band pass/reject filters suitable for 4G technologiet(Springer Link, 2022) Qasrawi, Atef Fayez; Daragme, Rana B.Herein, the efect of Yb, Al, Cu and Au metal substrates on the electrical performance of germanium oxide-based devices is reported. Back-to-back Schottky-type metal-insulator-metal (MIM) electronic devices with the structure (Yb, Al, Cu, Au)/ GeO2/C are prepared by vacuum evaporation under a vacuum pressure of 10?5 mbar. Capacitance-voltage characteristic curve analysis on these devices have shown that, while the forward-biased Al/GeO2/C displays NMOS (enhanced N-channel metal oxide semiconductor) characteristics, Cu/GeO2/C and Au/GeO2/C show inverted NMOS and PMOS felds efect transistor (FET) characteristics under forward and reverse biasing conditions, respectively. A large scale (8–737 nm) of depletion width and built-in potentials engineering is possible via metallic substrate selection. In addition, current-voltage characteristic curve analysis have shown that the dominant transport mechanism is by electric feld-assisted tunneling through narrow barriers. The only device that showed current rectifcation was the Yb/GeO2/C device. The absence of the recertifcation property from the (Al, Cu, Au)/GeO2/C devices is assigned to the large surface roughness of the metal substrates. Analysis of the capacitance, conductance, impedance and refection coefcient spectra in the frequency domain of 0.01–1.80 GHz have shown that the proposed device structures can exhibit features of negative capacitance efect devices and tunable microwave/ radio wave cavities. The observed notch frequency values of the (Yb, Al, Cu, Au)/GeO2/C devices make them suitable for use as bandpass/reject flters suitable for 4G technologyÖğe Design and characterization of MoO3/In2Se3 heterojunctions as terahertz/gigahertz band filters suitable for visible light communications and 3G/4G technologies(IOP Publishing, 2021) Qasrawi, Atef Fayez; Nancy, M. A. YaseenAbstract Herein, MoO3/In2Se3 (MI) heterojunctions are fabricated by a vacuum deposition technique for use as wideband filters. The MI devices are composed of optical and electrical parts to detect visible light spectra and microwave ac signals (0.01-3.0 GHz). Basic physical characterizations on the MI devices have shown that the devices are amorphous in nature, composed of MoO2.86/In2Se2.76 and exhibit valence and conduction band offsets of 1.62 eV and 3.10 eV, respectively. The optical conductivity analyses have shown that, the mobility and the plasmon frequency of charge carriers in the MI devices can reach 121.70 cm2/Vs and 5.39 GHz, respectively. The terahertz cutoff frequency in these heterojunctions is in the range of 0.54-4.80 THz. On the other hand, application aimed characterizations has shown that the MI heterojunctions exhibit high photosensitivity against daylight light-emitting-diode irradiation. In addition, imposing ac signal of power of -1.0 dBm and measuring the power transmitted within a band width of 5.0 MHz in the frequency domain of 0.01-3.0 GHz indicated that the MI heterojunction devices can behave as multiband bandstop filters with notch frequency value that suits 3G/4G mobile technologies. The features of the currently proposed MI devices nominate them for use as optical receivers suitable for visible light communication technology and as microwave band stop filters. Keywords: MoO3/In2Se3 heterojunction,band offsets, microwave resonators, terahertzÖğe Design and characterization of n -Si/p -CdO broken gap heterojunctions as high frequency PMOSFETs and microwave resonators(Institute of Electrical and Electronics Engineers Inc., 2021) Harbi, Seham R.Al; Qasrawi, Atef FayezHerein, p -type CdO thin films coated onto n -type Si crystals are employed to form metal oxide semiconductor field effect transistors (MOSFET). In the broken gap design, the valence band edge of Si substrates centered at 5.25 eV is aligned at conduction band edges of CdO centered at 5.20 eV. The construction of the energy band diagram indicated that the devices could reveal a deep built in potential of 4.68 eV. The device is fabricated by the thermal evaporation technique under vacuum pressure of 10-5 mbar. CdO thin films grown onto Si thin crystals form a randomly distributed nanorod-like grains of rod length and diameter of ~2.0 ?m and 160 nm, respectively. In addition, n -Si/p -CdO heterojunctions displayed typical diode characteristics with ideality factors of ~1.40 and barrier height of 0.67 eV. As passive mode devices, the C-V curves displayed enhanced PMOS channel with the ability of capacitance depletions in a wide range of frequency (10M-1.0 GHz). The depletion width of the device widens from 7.0 nm to 660 nm in that frequency domain. Moreover, the biased and unbiased impedance spectra analyses in the frequency domain of 1.0M-1.0 GHz, indicated the voltage controllability of the devices when operated as microwave cavities. The magnitude of the reflection coefficient spectra indicated the ability of using the MOSFET devices as high pass filters. The features of the n -Si/p-CdO heterojunctions nominate them for use as microwave band filters, PMOS field effect transistors and as frequency and voltage controlled tunable capacitorsÖğe Design and characterization of Yb/p? SiO2/(Yb, In) thin-film transistors for 5G resonators(Springer Link, 2022) Qasrawi, Atef Fayez; Khanfar, Hazem Khulqi; Alyat, Sara BassamHerein, Yb/ p?SiO2/(Yb, In) multifunctional thin-film transistors (TFTs) are designed and characterized. The TFT devices are fabricated in a vacuum thermal evaporation technique under a vacuum pressure of 10? 5 mbar. The transistors are composed of 100-nm-thick layer of p-SiO2 coated onto ytterbium substrates. While the Yb/SiO2/Yb back-to-back Schottky (BBS) channels display NMOS (metal–oxide–semiconductor) characteristics and behave as current rectifiers with rectification ratios of 3.2 ×102 , the Yb/SiO2/In BBS channels show PMOS characteristics and displayed a non-rectifying properties. Investigations which targeted ac signal analysis on these devices in the frequency domain of 0.01-1.80 GHz have shown that the current conduction are dominated by the correlated barrier hoping and by the quantum mechanical tunneling. The density of localized states near Fermi level and the relaxation times are highly influenced by the orbital overlapping of Yb and In metals with that of SiO2. It was shown that; while Yb/SiO2/Yb channels are suitable for use as microwave band filters, Yb/SiO2/In can perform as radiowave band reject filters. The calculated notch and microwave cutoff frequencies for these filters lay in the range defined for 4G/5G mobile technologies. The Yb/SiO2/Yb filters can pass more than 96% of the propagating signal with high-quality power transmissions.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 Design of Au/Cdbr2/Au as negative capacitance devices and as band filters suitable for 4G technologies(SciELO, 2021) Qasrawi, Atef Fayez; Hamarsheh, Areen A.Herein, cadmium bromide thin film devices are designed for possible use in communication technology. The 1.0 thin layer of CdBr2 is sandwiched between two Au (1.0 thick) layers using the thermal evaporation technique under a vacuum pressure of 10-5 mbar. The Au/CdBr2/Au devices are structurally morphologically and electrically characterized. It is observed that the hexagonal cadmium bromide exhibits large lattice mismatches with cubic Au substrates. The randomly distributed nano- rod like grains is accompanied with average surface roughness of ~26 nm. When an ac signal of low amplitude is imposed between the terminals of the Au/CdBr2/Au devices, a negative capacitance effect in the frequency domain of 10-1800 MHz is observed. In addition, analysis of the impedance spectra in the same domain has shown that the device behaves as band pass/stop filters suitable for 4G technology. The microwave based standard analysis of the Au/CdBr2/Au band filters have shown that it displays a notch () frequency of 2.0 GHz. The cutoff frequency at reaches 7.86 GHz. The features of the Au/CdBr2/Au devices nominate it for use as microwave resonators and as negative capacitance devices suitable for; 4G technology, noise reduction and for parasitic capacitance cancellation.Öğe Effect of lanthanum substrates on the structural, optical and electrical properties of copper selenide thin films designed for 5G technologies(Springer Link, 2022) Qasrawi, Atef Fayez; Ghannam , Arwa N. AbuIn this work, copper selenide thin films coated onto glass and transparent lanthanum substrates are studied. The (glass, La)/CuSe thin films which are prepared by the thermal evaporation technique under a vacuum pressure of 10?5 mbar are structurally, morphologically, optically, dielectrically and electrically characterized. Lanthanum substrates improved the crystallinity by increasing the crystallite size and decreasing both of the microstrains and defect density of copper selenide. La substrates redshifts the energy band gap and doubled the dielectric constant values. In addition, employing Drude–Lorentz approaches for optical conduction to fit the dielectric constant provided information about the effects of La substrates on the drift mobility, plasmon frequency, free carrier density and scattering times at femtosecond level. The drift mobility increased and the plasmon frequency range is modified when La substrates are used. Verifying impedance spectroscopy tests in the microwave frequency domain have shown the ability of the La(gate)/CuSe/Ag (source) transistors performing as band pass filters. These filters are suitable for 5G technologies. The microwave cutoff frequency reached ~ 5.0 GHz at a notch frequency of 2.80 GHz of the glass/La/CuSe/Ag highpass filters.Öğe Effect of transparent Pb substrates on the structural, optical, dielectric and electrical properties of copper selenide thin films(Forum of Chalcogeniders, 2022) Qasrawi, Atef Fayez; Abu Ghannam, A. N.Herein, copper selenide thin films are coated onto transparent lead substrates. Pb/CuSe stacked layers is fabricated by the thermal evaporation technique under a vacuum pressure of 10-5 mbar. They are structurally, morphologically, optically and electrically characterized. Lead substrates enhanced the crystallinity of CuSe through increasing the crystallite sizes, reducing the microstrain and lowering defect densities. In addition, a blue shift in the energy band gap associated with remarkable increase in the value of the high frequency dielectric constant resulted from replacement of glass by Pb substrates. Moreover, significant increase in the optical conductivity in the ultraviolet range of light is observed. Fitting the optical conductivity in accordance with Drude- Lorentz models allowed determining the effect of transparent Pb substrates on the plasmon frequency, scattering time at femtosecond level and drift mobility of CuSe. On the other hand, electrical measurements on the Pb/CuSe/C by imposing an ac signal of low amplitude in the frequency domain of 10-1000 MHz, have shown that the Pb/CuSe can perform as negative capacitance source employable for devices scaling and low power applications.Öğe 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.
