Evidence for Photoconductivity Anisotropy in Aligned TiO2 Nanorod Films

Enhanced photocatalytic properties of oriented films of rutile nanorods have previously been observed when the polarization of UV light is parallel to the rutile c axis. To reach a better understanding of this effect, we report here an investigation, in the dark and under UV-light irradiation, of the electrical resistance of aligned rutile nanorod films. In both cases, the resistance along the nanorod main ([001]) axis is 4 times smaller than that in the perpendicular directions. Moreover, the resistance decreases by an order of magnitude under UV irradiation. Furthermore, experiments were also performed with linearly polarized UV light, and we found that the film resistance is twice smaller when the UV-light polarization is parallel to the nanorods than in the perpendicular direction. These results give information about the mechanisms that control the electrical conductivity of aligned rutile nanorod films.