title: Observation of defect state in highly ordered titanium dioxide nanotube arrays.
abstract: For the first time, a conductive-substrate induced electro-deposition approach is employed to achieve highly ordered TiO2 nanotube arrays based on an anodic aluminum oxide template. Different from other methods, the morphology and parameters of arrays can be adjusted easily through changing the exposure area of a conductive layer. All these arrays are used as matrixes to explore the defect state emission by photoluminescence (PL) spectra. Interestingly, we find that the emission from blue edge to red edge (∼450 nm-600 nm) are apparently quenched in the ordered nanotube arrays, especially when compared to the PL spectra of nanowire arrays, single nanotube and nanoparticles. This distinct result originates from passivation of oxygen vacancies residing along the tube walls when the tubes are interconnected, which is further evidenced by the observation of PL spectra with crystalline phase and sintering. The passivation of defects suggests valuable charge transport perpendicular to the long axis of the tubes in the ordered arrays. This point is particularly significant to the design of highly efficient devices and the applications in various energy-related fields.
authors: School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, People's Republic of China.
authors: Hongchao
authors: H
authors: Zhang
authors: Min
authors: M
authors: Zhou
authors: Qun
authors: Q
authors: Fu
authors: Bo
authors: B
authors: Lei
authors: Wei
authors: W
authors: Lin
authors: Heshuai
authors: H
authors: Guo
authors: Minghong
authors: M
authors: Wu
authors: Yong
authors: Y
authors: Lei