Influence of ZnO seed crystals and annealing on the optical quality of low-temperature grown ZnO nanorods

Abstract

The influence of ZnO seed crystals and postgrowth annealing on low-temperature aqueous chemically grown ZnO nanorods is analyzed. At the seed crystal/nanorod interface a high density of structural defects leads to emission at 3.332 eV, attributed to excitons bound to structural defects. This peak is absent for seed crystals, very pronounced for rods of shorter lengths grown on seed crystals, and reduced for longer nanorods. After annealing in oxygen and nitrogen atmosphere, the near-band-edge excitonic transitions sharpen and deep-level emission is strongly reduced. Time-resolved photoluminescence measurements show a striking similarity between donor-bound excitons and excitons bound to structural defects.