Single-crystal ZnO nanowire arrays have emerged as promising building blocks for a new generation of devices in different technological domains such as optoelectronics, solar cells, gas sensing, field emission and piezoelectrics. Among the various deposition techniques, electrochemical deposition appears as a versatile method well suited to synthesize ZnO with a large variety of morphologies as well as epitaxial thin films. It is a low temperature method, well suited for cheap large-scale production. After reviewing the state of the art of the electrodeposition of ZnO, this presentation will focus on the deposition of arrays of ZnO nanowires (NWs). I will show, using more precisely the electroreduction of molecular oxygen method, that vertically aligned ZnO nanowires with tailored dimensions and electrical properties were obtained. The role of the composition and concentration of the electrolyte on the ZnO growth mechanisms will be emphasized. The anions from the zinc precursor and supporting electrolyte were found to play a major role in the synthesis of ZnO, opening new routes to tailor the dimensions of the nanowires. ZnO NWs with a diameter between 25 and 500 nm and a length up to 10 µm were successfully attained, resulting in high aspect ratios up to 50. The electrical properties of the ZnO NW arrays were analysed by electrochemical impedance spectroscopy. A cylindrical model which takes into account the geometry of ZnO NWs was developed, allowing to determine the carrier density of the ZnO NWs. Donor densities between 10¹⁷ and 10²⁰ cm^-3 were obtained as a function of the deposition conditions and thermal treatments. Those results showed that playing the electrolyte composition and concentration allows not only to monitor the dimensions of the ZnO NWs, but also their electrical properties. In conclusion, the application of electrodeposited ZnO NW arrays in nanostructured ETA-solar cells will be discussed.

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