Visible photoluminescence in ZnO tetrapod and multipod structures

The properties of ZnO tetrapod and multipod structures were investigated using scanning electron microscopy, x-ray diffraction, photoluminescence (PL), and electron paramagnetic resonance (EPR) spectroscopy. While there is relationship between g=1.96 EPR and green PL in some of the samples, this is not the case for all the samples. Therefore, the commonly assumed transition between a singly charged oxygen vacancy and photoexcited hole [K. Vanheusden, C. H. Seager, W. L. Warren, D. R. Tallant, and J. A. Voigt, Appl. Phys. Lett. 68, 403 (1996)] does not explain the green emission in all ZnO samples. The green emission likely originates from surface defects. (C) 2004 American Institute of Physics.