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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, 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 and applications of ITO/SeO2 interfaces(Springer Link, 2022) Alfhaid, Latifah Hamad Khalid; Qasrawi, A. F.Herein, indium tin oxide (ITO) thin film substrates are employed to fabricate ITO/SeO2 multifunctional interfaces. The effects of ITO substrates on the physical properties of SeO2 thin films are explored by the structural, morphological, optical and electrical characterization techniques. Amorphous SeO2 thin films are prepared by the thermal evaporation technique under a vacuum, pressure of 10– 5 mbar, that exhibit induced crystallization process when it is coated onto ITO substrates. ITO substrates additionally forced evolution of SeO2 nanotubes of diameters of 10–20 nm. Optically, coating SeO2 onto ITO substrates enhance the light absorbability in the visible and infrared ranges of light, blue shifted the energy band gap of SeO2 and forced dielectric resonance at 3.42 eV and 2.27 eV. Electrically, the ITO/SeO2/Ag devices display negative conductance and negative capacitance effects in the frequency domains of 0.01–0.35 GHz and 0.01–1.80 GHz, respectively. These features are beneficial for signal amplification and noise reduction in electronic circuits. In addition, the impedance spectroscopy analyses shows that the ITO/SeO2/Ag devices operate at high impedance mode in the microwave frequency domain. It also shows band stop filter characteristics that are well performing in the gigahertz frequency domain. The features of the band stop filter nominate the ITO/SeO2/Ag devices for use in 5G technologies.Öğe Effects of Pb nanosheets substrates on the optical and electrical properties CrSe thin films(Physica Scripta, 2023) Aljaloud, Amjad Salamah M.; Qasrawi, Atef Fayez; Alfhaid, Latifah Hamad KhalidHerein the effects of lead nanosheets substrates on the optical and electrical properties of chromium selenide thin films were studied. Chromium selenide thin films were grown by vacuum thermal evaporation technique onto glass and 100 nmthick lead nanosheets substrates. The effects of Pb nanosheets on the structural, morphological, compositional, optical and electrical properties was explored. While films grown onto glass substrates showed compositional stoichiometry forming CrSe2 phase those coated onto Pb substrates preferred the growth CrSe phase. Both films were of amorphous structure and exhibited direct and indirect allowed optical transitions. Pb nanosheets enhanced the optical absorption of chromium selenide in the visible and ultraviolet ranges of light. Formation of films onto Pb nanosheets resulted in band gaps and band tails narrowing and decreased the room temperature electrical conductivity (s) as well. Deep analyses of the s - T variations in the range of 25–340 Kshowed that the electronic transport is dominated by the thermal excitation and variable range hopping of charge carriers. It was observed that Pb nanosheets increased the average hopping energy and hopping range, decreased the density of localized states near the Fermi level and increased the degree of state disorder. The features of glass/CrSe2 and Pb/CrSe films are promising for using then in optoelectronic technologyÖğe Growth and characterization of chromium selenide thin films for optoelectronic applications(Optical and Quantum Electronics, 2023) Aljaloud, Amjad Salamah M.; Qasrawi, Atef Fayez; Alfhaid, Latifah Hamad KhalidHerein amorphous and stoichiometric CrSe2 thin films are obtained by the thermal deposition (TD) technique under a vacuum pressure of 10?5 mbar. The films are structurally, morphologically, optically and dielectrically characterized. It is observed that CrSe2 thin films grown by TD technique exhibit optical excitations within direct and indirect allowed energy band gaps of 2.60 eV and 3.19 eV, respectively. The amorphous CrSe2 thin films contained a wide range of exponential band distribution presented by Urbach energy width of 2.24 eV. In addition in contrast to the chemical bath deposition technique which produced Cr7Se8 films of low dielectric constant ( ), the TD technique revealed high dielectric constant values up to 11.9 for CrSe2 films. Moreover, the Drude-Lorentz modeling of the imaginary part of the dielectric constant spectra revealed drift mobility values in the range of 0.70–6.45 cm2/Vs. The plasmon frequency varied in the range of 5.42–8.33 GHz. Furthermore, analysis of the terahertz cutoff frequency ( ) spectra have shown that CrSe2 thin films exhibit values in the range of 3.30–40.0 THz. The features of CrSe2 thin films deposited by the thermal evaporation technique are promising semiconductor layers suitable for 6G and terahertz technology applications.Öğe Induced crystallization and enhanced light absorption and optical conduction in WO3 films via pulsed laser welding technique(Springer, 2023) Alfhaid, Latifah Hamad Khalid; Qasrawi, Atef FayezHerein amorphous WO3 thin films prepared by the thermal evaporation technique under a vacuum pressure of 10? 5 mbar are treated via pulsed laser welding technique (PLW) in an argon atmosphere. An induced crystallization process within one second for a spot of diameter of 2 mm is achieved via this technique. The crystalline films exhibited hexagonal structure and showed cuboid grains of dimensions of (length × width) 4.6 × 1.1 (?m)2. In addition, the PLW treated tungsten oxide thin films exhibited enhanced light absorbability reaching 90 times at 3.09 eV. Moreover in addition to the existing indirect energy band gap (3.50 eV) of WO3 films, the PLW treatment resulted in formation of another direct energy band gap of value of 1.92 eV. The pulsed laser welding of the WO3 films increased the optical conductivity of the films by 66 times and shifted the plasmon frequency from 0.19 to 6.99 GHz. The free charge carrier density also increased by two orders of magnitude. On the other hand, the impedance spectroscopy studies have shown domination of negative capacitance effect in samples treated with PLW technique. The conversion of the structure of the films from amorphous to polycrystalline that is associated with enhanced light absorption and improved optical conduction which is achieved within 41 s for a large area of 1.25 cm2 of the films is accounted as a smart new approach for improving the physical properties of thin films.Öğe LaGe2 thin films designed as band filters for 6G communication technology(Springer, 2023) Alfhaid, Latifah Hamad Khalid; Qasrawi, Atef FayezHerein, LaGe2 thin films with thickness of 150 nm are grown on thin layers of indium by the thermal evaporation technique under a vacuum pressure of 10?5 mbar. The films are structurally, morphologically, compositionally and electrically characterized. It is observed that thin films of LaGe2 are polycrystalline in nature, comprising slightly excess germanium in their structure. To establish their applicability in communication technology, two In/LaGe2/Ag and In/LaGe2/C electrical channels are formed. Both of the channels performed as negative resistance and capacitance sources. The channels exhibited microwave cutoff frequency exceeding 200 GHz. The resonance in the In/LaGe2/Ag and In/LaGe2/C channels dominates at driving frequencies of 1.21 GHz and 1.42 GHz, respectively. The measured impedance, magnitude of reflection coefficient (S11 parameter), return loss and voltage standing wave ratio spectra confirmed the suitability of the LaGe2 thin films for wireless 6G communication technology.Öğe Optical properties of chromium-selenide films designed for terahertz applications(Optik, Eylul 2023) Aljaloud, Amjad Salamah M.; Qasrawi, Atef Fayez; Alfhaid, Latifah Hamad KhalidHerein the effects of indium substrates on the properties of chromium selenide thin films are reported. Chromium selenide thin films and indium substrates are prepared by the thermal evaporation technique under a vacuum pressure of 10?5 mbar. It is observed that indium sublayers alters the atomic stoichiometry of chromium selenide. It induces the formation of Cr2Se3 phase instead of CrSe2 phase which grow onto glass substrates. Both of the glass/CrSe2 and In/Cr2Se3 films displayed direct and indirect energy band gaps. The respective gaps are 2.60 eV and 3.19 eV and 2.25 eV and 2.83 eV. The Urbach tails states exhibited a width of 2.24 eV in glass/CrSe2 and showed value of 0.85 eV in In/Cr2Se3. In addition a light absorbability enhancement of more than 45% is reached at the In/Cr2Se3 interfaces in the visible range of light. Moreover, as terahertz resonators, In/Cr2Se3 films showed larger optical conductivity. It also displayed a spectral terahertz cutoff frequency in the range of 3.0–35 THz. Furthermore, when utilized as terahertz resonators, In/Cr2Se3 films demonstrate heightened optical conductivity and a spectral terahertz cutoff frequency ranging from 3.0 to 35 THz. Analyzing these terahertz oscillators using Drude-Lorentz models reveals that the density of free charge carriers increases with higher oscillator energy, while the drift mobility of these carriers within the terahertz resonators varies between 1.10 and 3.09 cm²/Vs. The array of features showcased by In/Cr2Se3 thin films, including their performance as terahertz resonators, positions them as strong contenders for applications in optical and terahertz technologies.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.Öğe Performance of Pt/CRSe schottky diodes designed for 5G/6G technology applications(Virtual Co. Physics SRL, 2024) Alfhaid, Latifah Hamad Khalid; Qasrawi, Atef FayezHerein thin films of CrSe deposited by the thermal evaporation technique onto Pt substrates are designed as Schottky diodes. It is observed that the Pt/CrSe/C (PCC) Schottky diodes are of tunneling type showing barrier height and widths of 0.56 eV and 18 nm, respectively. These diodes displayed biasing dependent nonlinearity and negative slope of differential resistance. The analyses of the cutoff frequency spectra indicated that PCC devices can exhibit high cutoff frequency up to 17 GHz based on the driving signal frequency. The features of the PCC devices make it promising as electronic component suitable for 5G/6G technology applications.Öğe Production of PtInx thin films by the pulsed laser welding technique(Springer, 01.08.2023) Alfhaid, Latifah Hamad Khalid; Qasrawi, Atef FayezHerein, PtInx nanosheets are fabricated by the pulsed laser welding technique (PLW) in an argon atmosphere within seconds from stacked layers of Pt (150 nm) and In (150 nm). Pt/In stacked layers coated by thermal evaporation under a vacuum pressure of 10?5 mbar are exposed to pulsed laser irradiation. During the welding process, the pulse width, repetition frequency and arc voltage of the laser are all varied. It is observed that the formed PtInx alloys are highly sensitive to the laser welding conditions. A new phase of PtInx alloys, referred to as PtIn4, is obtained and shown to favor a monoclinic crystal structure. PtIn4 displayed a high microwave cutoff frequency exceeding 100 GHz and negative capacitance effect. Modeling of the capacitance spectra in accordance with the Drude–Lorentz approach for ac conduction showed that converting stacked layers of Pt/In into thin films of PtIn4 form by PLW improves the electrical conductance and the drift mobility of the films. A 900-fold enhancement in mobility is achieved via the PLW technique. The characteristics of the produced PtIn4 thin films, including the negative capacitance (NC) effects and the cutoff frequency values, make the films attractive candidates for use as the active layer to produce NC thin film transistors and as band filters suitable for 6G technology.Öğe Synthesis of copper nanosheets coatings onto glass and glass/CrSe2 substrates using ion coating technique for terahertz technology(Wiley, 2023) Alfhaid, Latifah Hamad Khalid; Qasrawi, Atef FayezIn this study, copper (Cu) nanosheets are utilized as semitransparent conducting optical windows for the fabrication of terahertz band filters based on chromium selenide (CrSe2). The deposition of CrSe2 thin films onto glass substrates is performed via the thermal evaporation technique followed by the application of Cu nanosheets using the ion coating technique. The interaction between Cu windows and CrSe2 films resulted in a slight widening of the energy bandgap and a remarkable reduction in the Urbach tail states from 2.24 to 1.23 eV. Furthermore, the coating of CrSe2 with Cu optical windows led to a decrease in the dielectric constant values of more than 35% and an increase in the terahertz cutoff frequency by more than 70%. The application of Cu windows increased the cutoff frequency to 23 THz. The correlation between electrical and optical conduction in the terahertz band filters is investigated through the utilization of Drude–Lorentz models, revealing that although Cu windows reduced the free carrier density and conductivity, they enhanced drift mobility, resulting in more efficient terahertz filter properties. The calculated optical constants and optical conductivity parameters provided evidence of the suitability of Cu-coated CrSe2 films for applications in terahertz technology.Öğe 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.
