This work demonstrates a simple method for fabricating a nano-structured device that performs notable photodetecting capabilities. With a template of anodic aluminum oxide, highly ordered Ni-NiO nano core-shell arrays were fabricated by annealing the electroless-deposited Ni arrays at 300°C for 30 minutes. High-resolution transmission electron microscopy (HRTEM) demonstrated that a NiO layer with a thickness of ∼5 nm was developed on the surface of the Ni arrays. The effects of annealing time and temperature on NiO were probed by HRTEM. Results show that temperature has a greater effect on the development of NiO. The NiNiO interface forms naturally a Schottky nanojunction, which covers most of the array surface when patterned with an indium-tin oxide (ITO) electrode. The ITONi-NiOSi device was found to yield photocurrent when exposed to ultraviolet (UV) light without an external voltage bias. The device takes great advantage of the large junction area and one-dimensional configuration of the core-shell array, displaying rapid photoresponse to UV light and subsequent steady photocurrent. These features make the proposed device a viable alternative to the UV photodetector.