Growth and study of c-axis-oriented vertically aligned ZnO nanorods on seeded substrate

ZnO nanorods (NRs) are grown by sonicated sol–gel immersion method at a lower temperature, along c-axis, i.e., normal to the glass substrate spin-coated with seed-layer of zinc oxide. Effects of seed-layer-precursor molarity and immersion time on the structural and morphological properties of NRs have been investigated. These two process parameters affect the diameter and length of the ZnO NRs significantly. The NRs are hexagonal in cross section. The polycrystalline seed-layer with nano-sized grains exhibits high transparency and quick photoresponse. The transmittance decreases after the growth of NRs but improves past annealing. The band gap value of bulk ZnO is tuned up to 190 meV by the growth of NRs and their subsequent annealing. These NRs exhibit green emission and persistent photoconductivity (PPC). The annealing of NRs quenches the green emission and reduces the PPC effect partially.