Supporting information for manuscript “Influence of ZnO nanowire array morphology on field emission characteristics” by S, Garry et al. Sample preparation

ZnO buffer layer Silicon substrates with (100) orientation were coated with a ZnO buffer layer in order to initiate ZnO nanowire growth and to ensure c-axis alignment. No attempt was made to remove the substrate native oxide layer in any case. Firstly a ZnO seed layer is deposited by drop coating a 5 mM solution of zinc acetate in absolute ethanol [1]. 3.5 μl of this solution is applied per cm of substrate area. After 20 seconds the substrate is rinsed with absolute ethanol and dried with a nitrogen stream. This process is repeated 5 times, after which the substrate is annealed at 350°C for 30 minutes to produce a thin ZnO seed layer. This layer is then used to initiate CBD growth of a thicker ZnO layer. The seed layers are submerged in a 25 mM zinc acetate solution in DI-H2O at 60 70°C for 3 hours. In order to reduce incorporation of precipitates onto the substrates after 90 minutes, they are removed from the solution and rinsed with DI-H2O and then submerged in a fresh zinc acetate solution for a further 90 minutes. After deposition the substrates are cleaned by sonication in fresh DI-H2O and dried with a nitrogen stream [2].