Origin of green luminescence of ZnO powders reacted with carbon black

ZnO powders were synthesized by a precipitation method and annealed with carbon black. Electron paramagnetic resonance (EPR) and photoluminescence spectroscopies were conducted to study the characteristics of the ZnO powders. The g factor of the EPR signal shifted to lower value for the samples annealed with carbon black. These signals are assigned to singly ionized oxygen vacancy composed of V-O(center dot) complex and isolated V-O(center dot) defects. The transition from V-O(center dot) complex to isolated V-O(center dot) is proposed to explain the shift of the EPR signals. In conclusion, a transition of an electron from V-O(center dot) to V-O(center dot center dot) at the surface of the ZnO particles is responsible for the green emission peak at 528 nm from current results. (c) 2007 American Institute of Physics.