Epitaxial growth of self-arranged periodic ZnO nanostructures on sapphire substrates grown by MOCVD

This article reports an investigation on the growth behaviour of ZnO epitaxial nanostructures and thin films grown by metalorganic chemical vapour deposition (MOCVD). Self-arranged periodic ZnO nanostructures consisting of a large number of ZnO nano-columns can be directly grown on bare sapphire surface without any lithography or other pre-patterning processes. The spacing of periodic nanostructures was ∼117 nm. The measurements of XRD 2θ/ω and φ scans indicated that epitaxial and non-epitaxial ZnO grains coexisted on the same substrate. According to cross-sectional transmission electron microscopy observation, these periodic ZnO nanostructures were epitaxially grown on sapphire substrates and separated by non-epitaxial ZnO grains. However, the in-plane periodic arrangement of ZnO nanostructures disappeared while increasing the growth temperature. Initial sapphire surface structure and CVD growth kinetics closely relate to the growth of self-arranged periodic ZnO nanostructures.