Synthesis of ZnO nanostructures by spontaneous oxidation of Zn films on p-type silicon substrates

•Different ZnO nanostructures have been achieved by oxidation of Zn films.•Morphologies of ZnO nanostructures could be controlled by gold positions.•The growth mechanism for the formation of ZnO nanostructures has been proposed.•The ZnO/p-Si heterojunction relevant to the photodetectors devices.

ZnO nanostructures have been synthesized on p-type silicon substrates using a two-step, spontaneous oxidation of Zn films method at room temperature. The samples both with and without a thin layer of gold in different positions have been spontaneously oxidized in a humid atmosphere for seven days to form nanosheets and ball-cactus like nanostructures. Diverse morphologies of hierarchical ZnO nanostructures have been obtained by annealing the samples at 700 °C in a nitrogen atmosphere for 1 h. A growth mechanism has been proposed for the formation of different ZnO nanostructures. It was found that the band-gap emission can be greatly improved and that the defect emission is suppressed to a noise level when a thin layer of Au was deposited between the Zn and the Si substrate. Moreover, our results show that the ZnO/p-Si heterojunction exhibits good performance for visible spectrum detection.