Abstract
We report on a method for the fabrication of a single titania nanowire (NW) connected with metal electrodes and its application to ultraviolet (UV) light detection. The detection mechanism is due to the desorption of oxygen molecules on the NW surface and the resultant decreasing of the Schottky barrier height at the NW/metal interface under UV illumination. Consequently, the current passing through the NW increases and can be utilized for detection. A titanium NW with a width of around 100 nm, thickness of 50 nm and length of 10 m was first fabricated by atomic force microscopy nanomachining and lift-off, and contact electrodes were created by conventional photolithography. The NW was then oxidized by two methods: one was ambient heating and the other atomic force microscopy nano-oxidation. Then a titania NW UV photodetector was obtained. The fabricated photodetectors were characterized by using light sources of white light and UV (254 and 365 nm at 3.3 mW cm-2) lamps. The results show that the devices do not respond to visible light and have good wavelength selectivity. The best sensitivity is around 12100% upon 254 nm light illumination. The present work has successfully accomplished the fabrication of single titania NW UV photodetectors by a top-down approach instead of the commonly used bottom-up approaches, which have the main disadvantage of controlling the positions of the NWs. The present approach can be potentially applied to the construction of other oxide NW sensing devices.