Browsing by Author "Wassel, Ahmed R"

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    Elucidation the effectiveness of acridine orange as light-harvesting layer for photosensing applications: Structural, spectroscopic and electrical investigations
    (Elsevier, 2022-11) Salem, Marwa S; Wassel, Ahmed R; Fedawy, M; Shaker, A; Al-Bagawia, Amal H; Alanazi, Adwan; El-Mahalawy, Ahmed M
    In this research, acridine orange, AO, bio-photosensitive thin films are prepared using vacuum thermal evapo- ration technique for optoelectronic applications. First, the crystal structure of the deposited films compared to powder is investigated using the XRD technique. Next, the surface morphology of the deposited AO thin film is characterized using the FESEM technique giving rise to a uniform, homogeneous, and granular polycrystalline film. The amplitude and spatial roughness parameters of the film are estimated. Furthermore, the optical properties of the deposited AO thin film are spectrophotometrically characterized in the range from UV to NIR. The recorded absorbance, transmittance, and reflectance showed high UV and visible absorption characteristics with a direct energy gap of ~2.238 eV. The optical constants, including refractive index and extinction coeffi- cient, are found, and the dispersion behavior is analyzed using the one-oscillator model for estimating the oscillator and dispersion energies. The dielectric function and dielectric relaxation time of AO thin film are interpreted in detail. In addition, an organic/inorganic heterogeneous junction based on Ag/AO/p-Si/Al is fabricated and electrically evaluated using the current-voltage relation. The fabricated heterojunction shows a rectification behavior of ideality factor, barrier height, and rectification ratio ~2.09, 0.707 eV, and 176, respectively. The charges dynamics mechanism in terms of band diagram and the density of interface states profile are analyzed. Eventually, the photoresponse of the engineered heterojunction is evaluated under the illumination of intensities that varies from 20 mW/cm2 to 100 mW/cm2 . The fabricated photosensor showed a high stable performance with responsivity, specific detectivity, linear dynamic range, and ON/OFF ratio of about 68.4 mA/W, 1.11 × 1010 Jones, 69.3 dB, and 108.4, respectively. The photoresponse performance of the present device is considered more efficient and stable than many other organic/inorganic photosensors.
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    Integration of biocompatible Coomassie Brilliant Blue dye on silicon in organic/Inorganic heterojunction for photodetection applications
    (Elsevier Ltd., 2022-07) Salem, Marwa S; Wassel, Ahmed R; Fedawy, M; Shaker, A; Al-Bagawia, Amal H; Aleid, Ghada Mohamed; El-Mahalawy, Ahmed M
    Here, we introduce systematic investigations of structural, morphological, and optical properties of solution- processed coomassie brilliant blue, CBB, thin films for photodetection applications. First, the structural and morphological features of the spin-coated CBB thin films are investigated using XRD and FESEM microscopy and yielded a polycrystalline, nanostructured, and porous CBB film of crystallite size and RMS roughness ~31.95 nm and 10.65 nm, respectively. The UV–Vis–NIR spectrophotometric measurements of transmittance and reflectance elucidated the efficient absorption and light-harvesting of the UV and visible light range with estimated indirect energy gap and Urbach energy ~1.54 eV and 22.3 meV, respectively. Next, the dispersion behavior of the fabricated thin films is analyzed in the light of the single-oscillator model estimating the detail dispersion pa- rameters. Furthermore, the dielectric function, as well as the nonlinear optical parameters, is accurately esti- mated. Subsequently, the microelectronic parameters of the engineered rectifying Ag/CBB/p-Si/Al heterojunction such as ideality factor, barrier height, series, and shunt resistances are estimated at different temperatures. The charges dynamical mechanism and the interface states density profile are analyzed, and the thermionic emission model is confirmed to fit the low bias region with a modified Richardson constant of about 34.8A/cm2 K2 .After that, the photoresponse of the implemented organic/inorganic heterojunction is checked at different illumination intensities and showed a significant stable sensitivity with fast On-Off switching behavior. The fabricated heterojunction achieved good figures of merit such as responsivity, specific detectivity, linear dynamic range, and rise/fall time of about 4.289 mA/W, 2.07 × 109 Jones, 30.36 dB, and 61.6/82.5 ms, respectively. The good and stable responsive performance of the current Ag/CBB/p-Si/Al architecture may make it a potential candidate for photodetection applications