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.