Spray pyrolysis deposition of zinc oxide nanostructured layers

Highly structured ZnO layers comprising well-shaped hexagonal rods were prepared by spray pyrolysis deposition of zinc chloride aqueous solutions in the temperature range of 490-560 degrees C. The layers were characterised by SEM, XRD and SAED. A flat ZnO film evolves into the structured layer consisting of single crystalline hexagonal elongated prisms at growth temperatures close to 500 degrees C and above. The rise of both the growth temperature and solution concentration increases rod dimensions. The deposition of the 0.1 mol/I solution at similar to 500 degrees C results in crystals with a diameter of 200-300 nm and length of 800 nm. However, the rods grown at 560 degrees C indicate a width in the range of 400-600 nm and a length of up to 2500 nm. The deposition of the 0.05 mol/I solution at 560 degrees C results in the rods with a diameter of 100-300 run and a length of 1500 run. The increase of the concentration up to 0.2 mol/I results in branched crystals, mainly tripods with a similar leg size of 600-700 nm in width and 3000 mn in length. According to XRD, the ZnO layers grown from the 0.1 mol/I solution in the temperature range of 450-560 degrees C are caxis-oriented, independent of morphology. The XRD peaks intensities ratio (I-002/I-101) of the samples deposited at 560 degrees C changes from 9 to 1.3 by an increase in the solution concentration from 0.05 to 0.2 mol/I and indicates that c-axis orientation vanishes at higher concentrations. We showed that ZnO nanorods with the length to diameter ratio of 30 can be prepared by spray technique using indium tin oxide-covered glass substrates instead of bare glass. (c) 2006 Elsevier B.V All rights reserved.