Effect of pH on the morphological evolution of NiO thin film synthesized on ZnO nanorod arrays by electrodeposition and post-annealing

•NiO/ZnO heterostructures were fabricated by using electrodeposition and post-annealing.•The effects of pH on the morphological evolution of NiO thin film synthesized on the ZnO nanorod arrays were investigated.•Formation of NiO nano-bridges depends strongly on the value of pH.

The effects of pH on the morphological evolution of NiO thin film synthesized on the ZnO nanorod arrays by electrodeposition and post-annealing were investigated. With increase in pH in the bath solution, the morphology of the NiO was evolved from a flaky nanostructure type to a thin film nano-bridge type and the thickness of NiO thin film bridges decreased. The transmission electron microscopy investigations revealed that the thin film bridges was composed of several stacked NiO layers, whose thickness was about 5∼10 nm.