Fabrication of vertically aligned ferromagnetic ZnO nanopillar arrays on sapphire substrates by polymer-assisted deposition

Vertically aligned ferromagnetic ZnO nanopillar arrays have been fabricated on single-crystal sapphire substrates through polymer-assisted deposition. X-ray diffraction and transmission electron microscopy analysis show that the arrays are ZnO hexagonal crystal structure along the c-axial direction. The existence of room temperature ferromagnetism of the arrays was confirmed by the superconducting quantum interference device measurements. The enhancement of ferromagnetism in ZnO nanopillar arrays is found to be correlated with the increase in Zn1− vacancies and the decrease in oxygen interstitials, which was shown by photoluminescence measurements of the samples. Our results provide a viable way to fabricate ferromagnetic vertical arrays of ZnO nanopillars.