UV nanophotodetectors: A case study of individual Au-modified ZnO nanowires

Abstract

In this work, ultraviolet (UV) nanophotodetectors based on individual gold-functionalized ZnO nanowires (Au/ZnO NWs) with different diameters and with different Au content were fabricated using a focused ion beam/scanning electron microscopy (FIB/SEM) system. The influence of the Au content, the diameter of the NWs, the applied bias voltage, the temperature and the relative humidity during operation on the UV sensing properties was investigated in detail. The necessity of a higher Au nanoparticles (NPs) coverage of individual Au/ZnO NWs in order to obtain higher UV response is demonstrated for the first time. A high UV response (IUV/Idark) of 21 for an individual Au/ZnO NW (with ∼ 6.4% Au NPs coverage) was obtained, which is by a factor of 17 higher compared to unmodified ZnO NWs. The investigation regarding the NW diameter confirmed that thinner NWs are more suitable for UV sensing applications due to the greater influence of surface phenomena on electrical properties. Most importantly, the elaborated nanophotodetectors in this work, based on individual Au/ZnO NWs, show an extreme low influence caused by water vapors, i.e. relative humidity on UV response, which is critical for practical applications of high performance UV photodetectors in normal ambient conditions. Our experimental results demonstrate clearly that the n-type Au/ZnO NWs with enhanced optoelectronic properties are highly promising building nano-blocks for near future nano-optoelectronic devices and possible for biosensing applications.