Mohamed Fathy Hasaneen

Fe[ ]Co _x O nanoparticles ([ ]−0.20 at.%) were synthesized via a hydrothermal method to systematically investigate the effect of cobalt incorporation on their structural, optical, surface, and magnetic properties. X-ray diffraction confirmed the formation of phase-pure rhombohedral Fe ₂ O ₃ with no detectable secondary cobalt phases, while progressive peak shifts indicated successful substitution of Co ions into the iron oxide lattice. Cobalt doping led to a controlled increase in crystallite size accompanied by reduced lattice strain and dislocation density, reflecting improved structural ordering. FTIR spectra revealed modifications in metal oxygen bonding consistent with dopant-induced lattice distortion. Morphological analysis showed aggregated near-spherical nanoparticles, with enhanced grain growth at higher cobalt concentrations. Nitrogen adsorption–desorption measurements demonstrated mesoporous characteristics, with a maximum BET surface area of 39.54[ ]m ² [ ]g[ ] at ([ ]). X-ray photoelectron spectroscopy identified mixed Fe[ ]/Fe[ ] and Co[ ]/Co[ ] oxidation states, indicating strong Fe–O–Co interactions and increased surface defect density. Optical studies revealed a systematic blue shift of the absorption edge and a widening of the optical bandgap from 2.57[ ]eV to 3.23[ ]eV with increasing cobalt content. Magnetic measurements showed enhanced saturation magnetization and coercivity, reaching 9.1[ ]emu[ ]g[ ] and 275[ ]Oe at ([ ]), followed by a decline at higher doping levels due to defect-mediated spin canting. These results demonstrate that controlled cobalt doping enables effective tuning of Fe ₂ O ₃ nanoparticle properties, highlighting their potential for applications in spintronics, magnetic sensing, and photocatalysis.

This study investigates Metal–Organic Vapor Phase Epitaxy (MOVPE)-grown AlGaN/GaN and AlN/GaN heterostructures using high-temperature thermal annealing and Secondary Ion Mass Spectrometry (SIMS). By fitting experimental diffusion coefficients (DAl) to the Arrhenius equation, two crucial kinetic parameters were found: the activation energy (E_a) and the pre-factor (D₀). In the AlGaN/GaN structure, the dominating out-diffusion of Al has a large D₀ = 4.03 × 10⁻⁵ cm² s⁻¹ and a low activation energy in the range of [2.1–2.4 eV]. A substitutional diffusion mechanism in the crystal lattice mediated by defects is closely linked to the low E_a. Significantly higher activation energies (E_a) of 3.66 and 4.59 eV, respectively, control both in- and out-diffusion processes in the AlN/GaN structure. The better intrinsic thermal stability of the pure AlN layer, whose stability is attained by a strong energy barrier, is confirmed by the increase of more than 1.2 eV in E_a.

A GaN layer with a thickness of 2 µm was grown on a sapphire substrate using atmospheric pressure metal–organic chemical vapor deposition (AP-MOCVD). Subsequently, the layer was annealed under a nitrogen atmosphere at temperatures ranging from 1000 °C to 1120 °C. High-resolution X-ray diffraction (HRXRD) analysis reveals the impact of thermal annealing on the mosaic structure of the GaN, specifically the tilt and twist variations in four planes: (00.2), (10.3), (10.2), and (10.1). Interestingly, the observed trends suggest a differential effect of annealing on screw and edge dislocation densities. The annealing process reduces the edge and screw dislocation density. Lower values (D_screw = 1.2 × 10⁸ cm⁻²; D_edge = 1.6 × 10⁹ cm⁻²) were obtained for the sample annealed at 1050 °C. Notably, both tilt and twist angles exhibited a minimum at 1050 °C (tilt = 252 arcsecs, and twist = 558 arcsecs), indicating improved crystal quality at this specific temperature. Photoluminescence (PL) spectroscopy further complemented the structural analysis. The intensity and broadening of the yellow band (YL) in the PL spectra progressively increased with the increasing annealing temperature, suggesting the presence of additional defect states. The near band edge PL emission (3.35 and 3.41 eV) variation upon thermal annealing was correlated with the mosaic structure evolution.

In this work, the free-catalyst chemical vapor deposition technique is used for synthesizing Sn_xZn_1-xO, x = 0.00, 0.02, 0.04, 0.06, and 0.08 nanostructures. X-ray diffraction analysis demonstrates that all of the samples have crystallized into a pure hexagonal-wurtzite structure without any impurities or secondary phases. The effect of adding Sn on the structural parameters, including crystallite size, bond length, lattice strain, unit cell, volume, and dislocation density of ZnO, is studied. Electron microscopy investigation proves that increasing the Sn concentration is associated with a transformation in the morphology from needles- to flakes-like shape. A blue shift in the optical energy gap is observed when Sn⁴⁺ cations are incorporated into the ZnO network structure, according to the UV-visible spectra in coincidence with the Burstein–Moss model. The electrical conductivity measurements reveal typical semiconductor features of the synthesized nanostructures where the thermally activated electrical conduction mechanism dominates. The photocatalytic mechanism is defined, and the rate constants and photodegradation efficiency are calculated. It is found that the photocatalytic properties are improved at an optimum doping ratio rather than rising linearly with the doping level. The Sn_0.04Zn_0.96O compound demonstrates the best photocatalytic capacity when exposed to UV light and attains the maximum degradation efficacy of 63.8% after irradiation for 180 min (photodegradation rate constant of 5.2 × 10⁻³).