Electrodeposition and impedance spectroscopy characterization of ZnO nanowire arrays

An overview of the electrodeposition of ZnO nanowire arrays from the reduction of dissolved molecular oxygen in zinc chloride solutions was reported. In spite of the internal structure of ZnO which favors the anistopic growth along the [0001] direction, the change in the local composition of the electrolyte around the nanowire during the electrodeposition was proposed as a major parameter to affect the nanowire growth mechanism. The influence of the ratio between the O-2 reduction rate and the diffusion of Zn2+ to the cathode was emphasized. Due to the particular morphology of the nanowire arrays, no lateral growth was observed when the reduction of O-2 was relatively fast, while the corresponding deposition efficiency was very low. The decrease of the O-2 reduction rate resulted in an enhancement of the deposition efficiency. The highest efficiencies (40-55%) were attained by using not only in an enhancement of the longitudinal growth, but also in a considerable lateral growth. The influence of the electrodeposition conditions on the donar density of ZnO nanowires was investigated by using electrochemical impedance spectroscopy. Donar densities from 5 x 10(9) cm(-3) to 3 x 10(20) cm(-3) were obtained for as deposited samples. They decreased to values in the range of 10(17)-10(18) cm(-3) after annealing in air (1 hour at 450 degrees C). (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim