Zinc oxide Nanowires (ZnO NWs) are a very promising oxide semiconductor nanostructure because of their good optical, electrical, and piezoelectric characteristics with possible use for field-emission displays, solar cells, laser¹and electroluminescent devices.

The synthesis of ZnO NWs is possible by electrodeposition from aqueous solution, a simple and cheap method working at low temperature. Its principle is based on an increase of the interfacial pH by electrochemical formation of OH^- from the reduction of dissolved oxygen. This leads to the precipitation of the zinc oxide at the electrode following the reactions^2,3:

½ O₂ + 2e^-+ H₂O →2OH^-

Zn²⁺+ 2OH^- → ZnO + H₂O

ZnO NWs are formed in presence of low concentration of zinc². Many papers are now published on the cathodic deposition of ZnO NWs by this method, but mechanistic aspects have not been explored in detail.

The aim of this study was to understand the mechanism of electrodeposition of ZnO NWs. The influence of different parameters such as pH, bath composition, time of deposition and potential of deposition on the growth was investigated by means of in situ techniques : chronoamperometry, pH-metry and Electrochemical impedance spectroscopy (EIS). The morphology and structure of the ZnO NWs were studied by field emission scanning electron microscope (FE-SEM). The optical properties of ZnO NWs were also studied by means of specular transmission and photoluminescence measurements. From the results we derive a general analysis of electrochemical reactions taking place during the formation with respect to the pH of the solution as a key parameter. We will show that ZnO NWs formation and properties correspond to very specific solution chemistry and substrate effect criteria.

References

1. T. Pauporté, D. Lincot, B. Viana and F. Pellé, Appl. Phys. Lett, 89, 233112 (2006)
2. S. Peulon, D. Lincot, Adv. Mater, 8, 166 (1996)
3. S. Peulon, D. Lincot, J. Electrochem.Soc, 145, 864 ( 1998)

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