Experimental evidence on low energy electron beam induced point defect activation in GaN grown by metal-organic vapor phase epitaxy (MOVPE) is presented. The GaN samples are irradiated with a 5–20 keV electron beam of a scanning electron microscope and investigated by photoluminescence and positron annihilation spectroscopy measurements. The degradation of the band-to-band luminescence of the irradiated GaN films is associated with the activation of point defects. The activated defects were identified as in-grown Ga-vacancies. We propose that MOVPE-GaN contains a significant concentration of passive VGa-Hn complexes that can be activated by H removal during low energy electron irradiation.

Nanocrystalline samples of ZnO doped with Fe2O3 were synthetized by wet chemical method. The series of ZnO nanosized samples in the wide range of Fe2O3 concentration (from 5 wt.% to 95 wt.%) was prepared by precipitation from nitrate solutions using ammonia. The phase composition of the samples was determined using X-ray diffraction measurements. The phases of hexagonal ZnO, and/or rhombohedric Fe2O3, and/or ZnFe2O4 were identified. The mean crystalline size of nanocrystals, determined with the use of Scherrer's formula, varied from 8 to 52 nm. The preliminary micro-Raman spectroscopy measurements were performed. The observed features are typical of Fe doped ZnO nanoparticles. The magnetic measurements revealed the presence of different types of magnetic behavior. For samples with high Fe2O3 contents (above 70 wt.%) the ferromagnetic ordering was observed at room temperature. For samples with lower Fe 2 O 3 contents we observed the phenomenon of superparamagnetism above the blocking temperature.

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