Browsing by Author "Hazem, Rafik"

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    Proton irradiation-induced defect aggregation and metallic nanoparticles in CaF2 single-crystal
    (Elsevier, 2023) Hazem, Rafik; Izerrouken, Mahmoud
    Proton irradiation induced-defects aggregation and metallic nanoparticles in single-crystal CaF2 was investigated by X ray diffraction (XRD), Raman spectroscopy and UV–Vis spectrophotometry. The structural reports reveal the degradation of material crystallinity after irradiation without amorphization, as a result of generated anion point defects (F- and H-center pairs). Particularly, Raman analysis reveals the colloids formation and even the increase of their size with increasing energy. While confirming this result, the optical measurements show an anticorrelation between the concentration of F-centers and Ca colloids with increasing proton fluence. The blue shift of the colloid band, observed at higher energies, indicates that larger colloids are formed at deeper penetration, resulting in the development of a compressive stress in material
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    Radiation damage induced by reactor neutrons in nano-anatase TiO2 thin film
    (Elsevier, 2020) Hazem, Rafik; Izerrouken, Mahmoud
    Reactor neutrons damage induced in nanocrystalline anatase TiO2 thin film, deposited by sol-gel on silicon substrate, was investigated by grazing angle X-ray diffraction (GAXRD), Raman spectroscopy, four-point probe and UV–visible spectrophotometry. After irradiation, the crystallinity of TiO2 films improves and the electrical resistivity increases, due to an annealing effect associated with the reduction in oxygen vacancies in material. The observed change in the response of irradiated material at higher fluence, demonstrated by a slight reduction in the degree of crystallinity and electrical resistivity, testifies to the simultaneous presence of an annealing effect and a damaging effect during neutron irradiation. Moreover, the difference in the response of anatase and rutile phases of TiO2 under neutron irradiation is explained by the difference in their crystalline structures and kinetic properties of defects. The optical band gap remains unchanged after irradiation meaning that no energy level has been produced within the forbidden region
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    The impact of reactor neutrons on 6H-SiC followed by irradiation of 91.3 MeV Xe ions–defects studies using positron annihilation spectroscopy
    (Institute of Physics, 2025) Hazem, Rafik; Izerrouken, Mahmoud; Yener, Murat Yavuz; Tav, Cumali; Yahsi, Ugur
    The positron annihilation spectroscopy (PAS) was used to study the defects in 6H-SiC single crystal generated only by the impact of reactor neutrons and, it followed by the irradiation of a 91.3 MeV Xe ion beam. After neutron irradiation, only silicon vacancy-related defects, as identified by the Doppler broadening, are created. Further positron lifetime-based analysis showed that these defects are mainly (VC-VSi) divacancy, (VC-VSi)3 and (VC-VSi)4 clusters. With the post irradiation of a 91.3 MeV Xe ion beam, the defects generated at high neutrons dose remained almost similar, indicating saturation of positron trapping. The results indicate two competing annihilation processes for silicon monovacancy VSi- pre-saturation, where the VSi is annealed by aggregation to form (VC-VSi)n vacancy clusters, and a saturation, where the VSi is annealed by recombination with interstitials.