Microwave activated chemical bath deposition (MW-CBD) of zinc oxide: Influence of bath composition and substrate characteristics

ZnO films have been deposited using microwave activated chemical bath deposition (MW-CBD) technique. In this procedure, a substrate is immersed in an aqueous chemical bath containing soluble ZnO precursors and irradiated with microwaves. Deposits produced by this method are crystalline and strongly adhered. The use of water-ethanol 1:1 (v/v) mixtures instead of water as a solvent and the addition of ethylenediaminetetraacetic acid (EDTA), a Zn2+ complexing agent, are factors that have been explored in this work. The influence of the chemical bath composition on the crystal habit of the deposited crystal has been analysed. Scanning electron microscopic characterization suggested that both the shape of the crystals and the texture of the films were highly influenced by the chemical bath composition. The observed morphological changes suggested a shift from kinetic to thermodynamic control in the crystal growth process, as a result of the addition of either ethanol or EDTA to the deposition bath. Moreover, comparison of films grown on bare glass or fluorine-doped tin oxide (SnO2:F) showed that heterogeneous deposition was favoured on conducting substrates due to their localized heating, as a consequence of the interaction of the substrate with the microwave irradiation.