Pressure-induced growth evolution of different ZnO nanostructures by a pulsed laser ablation method

ZnO nanostructure growth evolution from well-aligned two-dimensional nanowalls to one-dimensional nanowire arrays and finally to zero-dimensional nanoparticles was successfully demonstrated by a pulsed laser ablation and deposition growth method, where the growth pressure was proved to be the determinant factor for the formation of different ZnO nanostructures. At lower pressure, nanowall grew due to a prefer nucleation at the grain boundary of a ZnO wetting layer via a vapor-solid process. At middle growth pressure, the ZnO nanowire growth can be described with a nanoparticle-assisted pulsed laser deposition process. At higher growth pressure, due to the strong collision between the ablated ZnO clusters and background gas, only nanoparticles were deposited. These ZnO nanostructured arrays had a preferred c-axis growth orientation on c-cut sapphire substrates. The photoluminescence and field emission properties were also studied.