Optical detection of magnetic resonance and electron paramagnetic resonance study of the oxygen vacancy and lead donors in ZnO

Optical detection of magnetic resonance (ODMR) and electron paramagnetic resonance (EPR) spectra are investigated in ZnO single crystals. The strong negative ODMR line with axial symmetry of the g -tensor around the c axis with g ∥ = 2.0133 ± 0.0001 and g ⊥ = 2.0135 ± 0.0001 is ascribed to Pb 3 + ions. The strongest Pb 3 + ODMR spectrum is observed under excitation with visible light from an Ar + ion laser and below 40 Hz of on/off microwave power modulation. The negative Pb 3 + line, accompanied with effective mass (EM) donors over the spectral range of the photoluminescence (PL), shows spin dependent transfer of electrons from EM donors to Pb 3 + , competing with PL. The intensity of the Pb 3 + EPR line as well as the EPR line of oxygen vacancy ( V O + ) investigated in samples irradiated with 2.5 MeV electrons show a fast increase when the light is switched on and gradual decrease during illumination. The dependence of the growth and decay kinetics of the Pb 3 + and V O + EPR spectra on wavelength of light is analyzed by taking into account the double donor nature of the investigated centers and their energy level positions within the energy gap of ZnO.