Comparative study of ultraviolet detectors based on ZnO nanostructures grown on different substrates

Pd/ZnO/Pd metal-semiconductor-metal photodetectors have been successfully fabricated using a variety of high-quality ZnO nanostructures. The nanostructures used included well-aligned nanorods, tetrapod-like nanorods, and hair-like nanowires and were synthesized on Si (100), porous silicon (PS/Si), and quartz substrates, respectively, using a catalyst-free vapor solid mechanism for comparison. The morphological, structural, and optical properties of these nanostructures were investigated. Upon illumination with ultraviolet light (365 nm), the responsivity values of the fabricated photodetectors on PS/Si, Si, and quartz substrates were 0.22, 0.073, and 0.053 A/W, which correspond to quantum efficiencies of 85%, 28%, and 20%, respectively, at an applied bias of 5 V. The present study demonstrated that ZnO nanowires/PS exhibited a relatively fast photoresponse, with a rise time of 0.089 s and fall time of 0.085 s. The ZnO nanorods/Si and ZnO nanotetrapods/quartz exhibited a slow response, with rise times of 0.128 and 0.194 s and fall times of 0.362 and 0.4 s, respectively. The study suggests that the response time of the ZnO nanostructures to ultraviolet exposure is dependent on the type of substrate used. Results show that these nanostructures are suitable for sensing applications. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4757619]