4 results
Search Results
Now showing 1 - 4 of 4
Article Citation - WoS: 1Citation - Scopus: 1Pseudodielectric Dispersion in As2se3< Thin Films(Wiley-v C H verlag Gmbh, 2020) Kayed, Tarek S.; Kayed, Tarek Said; Qasrawi, Atef F.; Qasrawı, Atef Fayez Hasan; Kayed, Tarek Said; Qasrawı, Atef Fayez Hasan; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics EngineeringHerein, X-ray diffraction, energy dispersive X-ray spectroscopy, and spectral ellipsometry techniques are used to investigate the structural, pseudo-optical, and pseudodielectric properties of arsenic selenide thin films. The stoichiometric films which are prepared by the thermal evaporation technique are found to prefer the amorphous nature of growth. While the pseudoabsorption coefficient spectra display strong absorption bands at 1.84, 1.81, 1.41, and 1.13 eV, the preferred pseudo-optical transitions happen within a direct forbidden energy bandgap of 1.80 eV. In addition, the real part of the pseudodielectric spectra displays three strong resonance peaks at critical energy values of 2.33, 1.90, and 1.29 eV. Modeling of the imaginary part of the pseudodielectric constant spectra in accordance with the Drude-Lorentz approach results in the existence of six linear oscillators. The response of arsenic selenide to elliptically polarized light signals shows that the films exhibit drift mobility, free electron concentration, and plasmon frequency values in the ranges of 0.21-43.96 cm(2) V(-1)s(-1), 1.90-58.0 x 10(19) cm(-3), and 5.8-32.0 GHz, respectively. The optical conductivity parameters for As2Se3 film nominate it as a promising candidate for the fabrication of tunneling diodes suitable for microwaves filtering up to 32.0 GHz and as thin-film transistors.Article Citation - WoS: 9Citation - Scopus: 8Exploring the Optical Dynamics in the Ito/As2< Interfaces(Springer, 2019) Al Garni, S. E.; Qasrawi, A. F.In this work, the effects of indium tin oxide (ITO) substrates on the structural, compositional, optical dielectric and optical conduction properties of arsenic selenide thin films are investigated. The As2Se3 films which are prepared by the thermal deposition technique under vacuum pressure of 10(-5) mbar exhibit an induced crystallization process, improved stoichiometry, increased optical transmittance in the visible range of light and increased dielectric response in the infrared range of light upon replacement of glass substrates by ITO. The ITO/As2Se3 interfaces exhibit conduction and valence band offset values of 0.46 eV and 0.91 eV, respectively. The experimental optical conductivity spectra are theoretically reproduced with the help of the Drude-Lorentz approach for optical conduction. In accordance with this approach, owing to the improved crystallinity of the arsenic selenide, the deposition of As2Se3 onto ITO substrates increases the drift mobility value from similar to 17.6 cm(2)/Vs to 34.6 cm(2)/Vs. It also reduces the density of free carriers by one order of magnitude. The ITO/As2Se3/C heterojunction devices which are tested as band filters which may operate in the frequency domain of 0.01-3.0 GHz revealed low pass filter characteristics below 0.35 GHz and band pass filter characteristics in the remaining spectral range.Article Citation - WoS: 3Citation - Scopus: 3Characterization of As2se3< Heterojunction Designed for Multifunctional Operations(Iop Publishing Ltd, 2021) Qasrawi, A. F.; Kayed, T. S.In this article, As2Se3/MoO3 heterojunction devices are structurally, compositionally, optically and electrically characterized. The heterojunction devices which are prepared by the thermal evaporation technique under vacuum pressure of 10(-5) mbar are observed to exhibit amorphous nature of growth. The optical spectrophotometry measurements and analyses on the heterojunction devices revealed a conduction and valence band offsets of values of 2.64 and 4.08 eV, respectively. In addition, the dielectric dispersion and the optical conductivity parametric analyses have shown that the heterojunction could exhibit large drift mobility value up to 73.7 cm(2) V-1 s(-1). From electrical point of view, while the capacitance- voltage curves reveal characteristics of MOSFET devices, the current--voltage curves display tunneling diode characteristics. The features of the As2Se3/MoO3 devices including the band offsets, drift mobility, plasmon frequency, microwave band filtering and MOSFET characteristics make them attractive for use as thin films transistors suitable electrical and optical applications.Article Citation - WoS: 6Citation - Scopus: 5Characterization of Au/As2< Multifunctional Tunneling Devices(Wiley-v C H verlag Gmbh, 2020) Qasrawi, Atef FayezHerein, the physical design and characterization of the Au/As2Se3 Schottky barrier that is prepared under a vacuum pressure of 10(-5) mbar are reported. The Schottky diodes are characterized by means of X-ray diffraction, energy-dispersive X-ray spectroscopy, current-voltage characteristics, and conductivity, capacitance, and impedance spectroscopy. It is observed that the Schottky barriers exhibit a biasing-dependent large rectification ratio with current conduction mechanisms dominated by the electric field-assisted quantum mechanical tunneling through a barrier height of 0.29 eV and depletion width of 13.3 nm. While the spectral analysis of the alternating current (AC) conductivity reveals mixed conduction with the contribution of both of the tunneling and correlated barriers hopping mechanisms, the capacitance spectra display resonance-antiresonance phenomena at 0.201 GHz. A wide range (0.21-1.80 GHz) of negative capacitance (NC) effects is observed in devices. In addition, the impedance spectroscopy analyses show that the Au/As2Se3 devices exhibit band-stop features with a notch frequency of 1.14 GHz and return loss value of 16 dB. The NC effect, resonance-antiresonance, filtering features, as well as the high rectification ratio at a relatively low biasing voltage (approximate to 0.30 V) nominate the Au/As2Se3 devices for applications which require noise reduction, parasitic effect cancellations, and microwave filtering.
