Surface acoustic wave ultraviolet detector based on zinc oxide nanowire sensing layer

The surface acoustic wave (SAW) ultraviolet (UV) detector based on zinc oxide (ZnO) nanowire sensing layer was developed and fabricated in this paper. To improve the SAW device's response characteristics, inter-digital transducers (IDTs) apodized by Morlet wavelet function and multiple couplers (MSC) were applied. ZnO nanowire materials were synthesized by Zinc thermal evaporation method. The ZnO nanowire sensing layer was coated onto the propagating area of the SAW devices, namely the sensing area, by transfer method as well as the multi-crystal ZnO sensing layer was deposited onto another device by magnetron sputtering for comparison. It was found that ZnO nanowire layer itself shows enhanced UV photoelectric response characteristics compared to sputtered ZnO film layer, which is acquired by characterizing their optical and photoelectrical properties. Under illumination of a UV light source, central frequency shifts of the two UV detectors were measured. An average central frequency shift of over 65 kHz of the UV detector based on ZnO nanowire layer was observed under 150 μW/cm2 365 nm illumination for several on–off cycles while the one of the other detector was only about 8 kHz. Moreover, the results indicate that the ZnO nanowire layer based SAW UV detector has good stability and repeatability. This kind of SAW UV detector with high sensitivity presents the potential for practical UV detection applications.