Diameter-Controlled Vapor-Solid Epitaxial Growth and Properties of Aligned ZnO Nanowire Arrays

A facile, template-free method was used to grow large areas of well-aligned ZnO nanowire arrays on amorphous SiO2 substrates. The arrays are composed of vertically aligned, single-crystalline, wurtzitic [001] ZnO nanowires whose diameters were easily controlled by growth temperature, adjusted by changing the distance between the substrate and the precursor material in the growth chamber. A vapor-solid epitaxial growth mechanism is proposed by which ZnO nanocrystals, nucleated on a NiO catalytic film, seed the growth of the ZnO nanowires. Photoluminescence spectra indicate broad visible wavelength emission, likely caused by near surface traps, whose intensity relative to band edge ultraviolet emission grows as nanowire radii decrease. UV photoconductivity measured for individual ZnO nanowire devices demonstrates their potential as a UV light nanosensor.