Growth of ZnO submicron single-crystalline platelets, wires, and rods by ultrasonic spray pyrolysis

Submicron single crystals of ZnO were grown by spray pyrolysis: the mist of an aqueous solution was generated by ultrasonic agitation and then pyrolyzed on a heated glass substrate. Hexagonal platelets of ZnO 10-90nm thick were obtained when ammonium acetate was incorporated into the precursor solution of zinc acetate. Single-crystalline wires and rods, which were 50-150 and 300-4000nm thick respectively, were obtained when indium nitrate was co-incorporated into the solution as a metal catalyst. The crystallographic direction of wires and rods was parallel to one of the [0001], [10 (1) over bar0], or [11 (2) over bar] axis of wurtzite. As substrate temperature increased, the aspect ratio of the crystal thus tended to decrease. Structural and compositional analyses of these crystals were performed by scanning electron microscopy, scanning ion microscopy, transmission electron microscopy and electron diffraction, X-ray diffraction, X-ray photoelectron spectrocopy, and energy dispersive X-ray spectroscopy.