Vertically aligned ZnO nanotube arrays fabricated on an ITO substrate are found to exhibit strong persistent photoconductivity (PPC) effect and electrically driven conductance switching behavior, though the latter shows a gradual decay from high conductance state to a low conductance state. Unlike the electrical switching, the PPC cannot be reset or reversed by an electrical pulse. Excitation wavelength dependent conductance measurement indicates the presence of the defect localized states (DLS) ~ 240meV above the valence band edge, in support of the hypothesis that the doubly ionization of these DLS are responsible for the PPC effect.
@article{arxiv.0806.2907,
title = {UV-photon and electrically driven resistance switching in ZnO nanotube arrays},
author = {Peng Liu and Guangwei She and Zhaoliang Liao and Yao Wang and Zhenzhong Wang and Wensheng Shi and Xiaohong Zhang and Shuit-Tong Lee and Dongmin Chen},
journal= {arXiv preprint arXiv:0806.2907},
year = {2009}
}