Growth and Characterization of Trumpet-Shaped ZnO Microtube Arrays on Si Substrates

Aligned trumpet-shaped zinc oxide microtube arrays have been successfully prepared on silicon (100) substrates via the chemical vapour deposition method with a mixture of ZnO and active carbon powders as reactants. The results show that two types of trumpet-shaped ZnO microtubes can be obtained. A plausible growth mechanism based on the studies of scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), and room-temperature photoluminescence spectroscopy is proposed and discussed. The initial metastable zinc-rich ZnOx embryos play a key role in the formation of trumpet-shaped ZnO microtubes. On the different surfaces of metastable zinc-rich ZnOx (x<1), embryos exhibit different stabilities and resistivities to oxidation; these tiny embryos are gradually extended with different growing rates along the directions of its long axis and circular boundary around its oxide shell. Just this special reason creates the formation of trumpet-shaped microtubes and results in the erratic and imperfect hexagonshaped cross section that appears. Moreover, the analytical results also show that the as-synthesized ZnO microtube arrays can exhibit better room-temperature photoluminescence behaviour.