Atef Fayez Qasrawi

Amorphous Ge thin films coated with rare-earth yttrium (Y) and ytterbium (Yb) nanosheets were investigated as multifunctional materials for electronic and microwave applications. Electrical characterization of as-grown Ge and coated Ge (Y, Yb) structures over 30–300 K and 0.01–6.0 GHz showed that Y and Yb coatings enhanced the low-temperature electrical conductivity by factors of 23.7 and 11.3, respectively. Charge transport was governed by thermally activated conduction and variable range hopping above about 120 K, while tunneling dominated in the 20–120 K range, indicating that rare-earth coating strongly modifies carrier localization and interfacial electronic states in Ge. In the 0.001–1.8 GHz range, Ge/Y and Ge/Yb also exhibited negative conductance and negative capacitance, supporting their potential for signal processing and sensing technologies. In parallel, sub-6 GHz two-port microwave measurements showed that the Y-coated sample exhibited the broadest common matched frequency range of 2.01–3.90 GHz and a balanced two-port response near 2.40 GHz. For Ge/Y, the minimum reflection coefficients were S₁₁ = −37.84 dB at 2.61 GHz and S₂₂ = −38.06 dB at 2.34 GHz, while S₂₁ and S₁₂ reached −24.12 dB and −23.96 dB, respectively, at 0.21 GHz. These results establish rare-earth coating as an effective approach for tuning the electrical and microwave network response of amorphous Ge thin-film structures and motivate their further investigation for sub-6 GHz microwave and wireless-device applications.

This study presents pulsed laser irradiation (PLI)-induced crystallization of amorphous Cu ₂ O/WO ₃ (CW) heterostructures and evaluates their structural, optical, and electromagnetic behavior for sub-terahertz and sub-6 GHz applications. By varying the PLI fluence from 1.27 to 81.48 kJ cm ⁻² , crystallization occurred within one second, forming tetragonal phases at low and hexagonal phases at high fluence. Higher fluence increased grain size, porosity, and generated two distinct optical band gaps. Impedance spectroscopy studies in the range of 10 MHz–1.8 GHz revealed cutoff frequencies exceeding 347 GHz, confirming their potential for high-frequency waveguiding which was also confirmed by computer simulations using telegrapher’s equations and network equations. Planar PLI processed samples was implemented as compact rectangular monopole antenna networks and experimentally characterized over 0.01–6.0 GHz. The antennas exhibit multiband and wideband impedance matching, with low fluence resulting in a 3.18 GHz bandwidth (2.52–5.70 GHz) and high fluence showing a narrower 1.80 GHz bandwidth (3.12–4.92 GHz). Distinct resonance behaviors were observed, including deep minima below −20 dB, indicating efficient radiation and good impedance matching. The results demonstrate the suitability of these antennas for sub-6 GHz wireless systems, including 5 G 6 G ⁻¹ applications.

Herein, robust crystallization of thermally evaporated CuO on Si is achieved through the application of Mo‐nanosheets, with a 20‐nm coating being sufficient to induce monoclinic CuO formation and further increases in Mo thickness producing no measurable change in structural order. Mo‐induced tuning of band bending and depletion width in SCM‐xx devices is demonstrated at 1 MHz. The capacitance‐voltage and Mott–Schottky analyses reveal a non‐monotonic capacitance response with strong suppression in SCM‐20. In addition, the current‐voltage characteristics show increasing voltage‐dependent asymmetry with Mo nanosheet thickness. Moreover, an engineered capacitively loaded circular microcavity antenna (CL‐CMA) based on a vertically integrated Ag/Si/CuO/Mo/Ag heterostructure exhibits excellent resonance at 2.6, 3.07, and 3.20 GHz as a result of the Mo coating on CuO, with return loss exceeding 40 dB at 3.20 GHz and a bandwidth of 2.25 GHz, values that are promising for high‐frequency applications. Furthermore, full‐wave electromagnetic simulations examining how Mo thickness influences the RF behavior of Si/CuO structures contacted by Ag electrodes, reveal that a 20‐nm Mo layer provides the most efficient impedance matching and deepest S ₁₁ minimum. The radiation patterns remain largely unchanged across samples. Overall, the features of the devices are promising for advanced electronic applications.

Herein, CuO waveguides are deposited on glass substrates and then overlaid with ultrathin Mo nanosheets (50–300 nm thick) to modify their electro‐optical and microwave properties. Although the Mo thickness does not modify the microstructure, it systematically increases the surface roughness, optical absorption, band tail states, and optical bandgap. The addition of Mo facilitates the controlled modification of dielectric screening, optical losses, and carrier transport mechanisms for both visible and near‐infrared wavelengths. Moreover, the drastic increment in the cutoff frequency to 25 THz at 406 nm (laser lines) underlies the enhanced high‐speed optoelectronics provided by the Mo‐modified waveguides. When incorporated into a periodic CuO waveguide device with platinum (Pt) top electrodes, the ultrathin Mo coatings further modify the microwave properties. Specifically, the 100 nm Mo‐coated waveguide shows a strong reflection minimum at −32 dB and an effective working band of 2.40 at 3–5 GHz. Simultaneously, the complementary S ₂₁ transmission characteristics show smooth and broad incrementing transmission efficiencies for increased Mo thickness, thereby confirming the controlled coupling efficacy of the CuO/Mo/Pt waveguides. The Mo‐modified copper oxide waveguides demonstrated here underlie their suitability as tunable platforms for the development of various optoelectronics and terahertz applications.