UV detection properties of hybrid ZnO tetrapod 3-D networks

Abstract

Hybridization of micro- and nanostructures of semiconducting oxides is known to be an efficient way to greatly improve their sensing properties and photocatalytic activity. In this work, zinc oxide (ZnO) tetrapod (T) three-dimensional (3-D) highly porous networks were hybridized with MexOy and ZnxMe1-xOy compounds (Me = Sn, Fe, Bi, Cu or Al), and their ultraviolet (UV) sensing properties were investigated. Additionally, individual Al-doped ZnO-T (ZnO-T:Al) with different diameters were integrated into devices using a FIB/SEM system to study the influence of diameter on the UV sensing properties. ZnO-T−CuO hybrid networks demonstrated the highest increase in UV response (with about 2.5 times) and decrease in response and recovery time (τr1 = τr2 ≈ 0.03 s and τd1 = τd2 ≈ 0.045 s) compared to pristine ZnO-T networks before hybridization, which is quite promising for applications in fast optical communication. The ZnO-T−Zn2SnO4 hybrid networks showed only a slight increase in UV response while other types of hybrid networks showed a considerable decrease in UV response, especially in the case of ZnO-T−Bi2O3 hybrid networks, which could be attributed to the fast recombination of photoexcited electrons and holes in Bi2O3 under the UV light illumination. The results demonstrate that hybridization with p-type materials is more efficient due to higher photogenerated charge separation properties. In the case of individual structures the device based on a microwire with lower diameter showed higher stability and good repeatability with a relatively high UV response of about 5.5. The excellent UV sensing properties combined with ultra-low power consumption make such devices very attractive for real applications like portable UV dosimeters. This work demonstrated the high efficiency of ZnO-T hybridization with p-type metal oxides for improvement of UV sensing properties.