The results of electron paramagnetic resonance (EPR), photo-EPR, and optical detection of EPR (ODEPR) investigation of different point defects in ZnO single crystals, ceramics and powders are reported. The main attention is given to EPR and photo-EPR studies of oxygen vacancy (V-o) being in scope of many experimental and theoretical investigations. Different EPR and ODEPR spectra related to Vo and reported in literature are analyzed and their temperature stability is investigated. The properties of the Pb atoms playing important role in spin dependent recombination process are studied. Specific features of the V-o(+) and Pb3+ EPR spectra, such as (i) reversal and not reversal change of EPR lines intensity under excitation by light with different wavelengths, (ii) fast increase followed by slow decrease of EPR spectra when light is switched on, (iii) correlation between EPR photoexcitation and persistent microwave photoconductivity are discussed. Spectral and time dependences of the Pb3+ EPR spectrum are explained taking into account double donor nature of Pb in ZnO. Experimental results on the photoexcitation and quench of the EPR spectrum in different ZnO samples are reported. (C) 2009 Elsevier B.V. All rights reserved.
