Optical detection of magnetic resonance (ODMR) and electron paramagnetic resonance spectra were 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 and g┴ =2.0135 was ascribed to Pb3+ ions. The strongest Pb3+ ODMR spectrum was observed under excitation with visible light from an Ar+ ion laser and below 40Hz of on/off microwave power modulation. The negative Pb3+ line, accompanied with effective-mass donors over the spectral range of the photoluminescence , showed spin dependent transfer of electrons from effective-mass donors to Pb3+, competing with photoluminescence. The intensity of the Pb3+ electron paramagnetic resonance line as well as the electron paramagnetic resonance line of O vacancy (VO+) investigated in samples irradiated with 2.5MeV electrons showed a fast increase when the light was switched on and gradual decrease during illumination. The dependence of the growth and decay kinetics of the Pb3+ and VO+ electron paramagnetic resonance spectra on wavelength of light was analyzed by taking into account the double donor nature of the investigated centers and their energy level positions within the energy gap of ZnO.

Optical Detection of Magnetic Resonance and Electron Paramagnetic Resonance Study of the Oxygen Vacancy and Lead Donors in ZnO. Laiho, R., Vlasenko, L.S., Vlasenko, M.P.: Journal of Applied Physics, 2008, 103[12], 123709