29 February 2012 Spectroscopic determination of the flatband potential and carrier density of ZnO nanowire array with/without hydrogen plasma treatment
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Proceedings Volume 8263, Oxide-based Materials and Devices III; 82631A (2012) https://doi.org/10.1117/12.907500
Event: SPIE OPTO, 2012, San Francisco, California, United States
Abstract
A dense array of vertical ZnO nanowires on a-plane sapphire substrate was synthesized by a simple chemical vapor deposition method. The electrolyte-based Schottky contact of the ZnO nanowires was investigated by electrochemical impedance spectroscopy. An n-type semiconductor behavior and a flat-band potential of about 0 V (0.05 V) versus Ag/AgCl electrode were obtained for the synthesized ZnO nanowires. The ~ 0 V flat-band potential is suggested to be a balanced result of (1) the Femi-level difference induced by the Schottky contact at the ZnO/electrolyte interface and (2) the oxygen vacancy induced surface adsorption effect at the ZnO nanowire surface. Hydrogen plasma treatment was carried out to passivate the oxygen vacancies in the ZnO nanowires. An obvious shift of the flat-band potential to about - 0.6 V was obtained for the same ZnO nanowire array sample after the hydrogen plasma treatment. The negative flatband potential, indicating an electron depletion region at the surface of ZnO nanowires, is observed owing to the Fermilevel difference between the n-type ZnO nanowires and the electrolyte, without a strong influence of the oxygen vacancy-related surface adsorption effect. Moreover, the carrier density in the ZnO nanowires was increased by almost four orders of magnitude after the hydrogen plasma treatment. The increase in carrier density confirms existing reports of hydrogen atoms occupying interstitial sites in the ZnO nanowires in addition to the oxygen vacancies after the hydrogen plasma treatment.
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Miao Zhong, Alexandra Apostoluk, Etsuo Maeda, Georges Bremond, Jean-Jacques Delaunay, "Spectroscopic determination of the flatband potential and carrier density of ZnO nanowire array with/without hydrogen plasma treatment", Proc. SPIE 8263, Oxide-based Materials and Devices III, 82631A (29 February 2012); doi: 10.1117/12.907500; https://doi.org/10.1117/12.907500
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