Discrepancy between ambient annealing and H+ implantation in optical absorption of ZnO

The discrepancy between sub-bandgap absorption in ZnO induced by thermal annealing and H+ implantation is investigated in this study for the first time. Results indicate that nonreductive annealing-induced optical absorption is independent of annealing ambient, and can be assigned to V-o, whereas the absorption centers caused by H+ implantation and H-2 annealing are primarily associated with V-o and ionized Zn-i. (C) 2016 Elsevier B.V. All rights reserved.