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    Electro-optical dynamics in SnO2 designed as negative resistance sources and gigahertz/terahertz band filters
    (Springer, 2024) Kmail, Bayan H.; Qasrawi, Atef Fayez
    Amorphous thin films of SnO2, prepared by a vacuum evaporation technique under a pressure of 10(- 5) mbar, are employed as electro-optical filters suitable for microwave, infrared, and visible light communication technologies. The filters perform as optical layers, exhibiting optical transitions within an energy band gap of 3.62 eV, with the band gap containing energy band tails of widths of 0.63 eV. In addition, dielectric dispersion analyses on the optical filters show their ideality for high k-gate dielectric applications. Wide tunability in the dielectric response is observed in these films. Moreover, analyses of the optical conductivity and terahertz cutoff frequency spectra have shown that SnO2 films exhibit resonance of optical signals suitable for infrared and visible light communication technology as well. When excited with infrared light of energy of 1.38 eV, the drift mobility and free hole concentration in these films reach 11.72 cm(2)/Vs and 2 x 10(17) cm(- 3), respectively. Furthermore, the device exhibits a negative resistance effect in the microwave range of 0.1-1.80 GHz, and terahertz cutoff frequency values in the range of 10 GHz - 48 THz. The features of the SnO2 electro-optical band filter make them attractive for communication technology extending from 5G/6G to IR and reaching visible light communications.
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    Nb2O5/SnO2 heterojunctions designed as optical absorbers and microwave band filters
    (Wiley, 2024) Qasrawi, Atef Fayez; Kmail, Bayan H.
    Herein, a 200 nm thick films of p-SnO2 are deposited onto p-Nb2O5 thin substrates (100 nm) to construct an isotype p-Nb2O5/p-SnO2 (NSO) heterojunction devices. The device is constructed using a thermal coating method in a vacuum media of low pressure reaching 10(-5) mbar. NSO heterojunctions represent two amorphous/amorphous-stacked layers that exhibit enhanced light absorption exceeding 170% and 120% in the visible and infrared regions of light spectrum, respectively. In addition, the interface under study displays band conduction offset of 0.60-0.90 eV and valence bad offset of 0.53-0.83 eV, respectively. The NSO device, which is treated as a planner microwaves resonators by contacting it with two Ohmic Pt electrodes, shows AC electrical conduction by the correlated barrier hopping within correlated barriers of average heights of 0.127 eV. Electrical conduction is actualized within scattering time constant of 0.27 ns. NSO microwaves resonators display gigahertz cutoff frequency spectra that suit 6G technology applications. The cutoff limit can be engineered in the range of 1.0-12.0 GHz by altering the driving frequency value. The features of the NSO heterojunctions nominate them for use in optoelectronic, which require high light absorption. The heterojunction devices are also promising for potential use in microwave technology a 6G bands filters.