Sensitivity simulation of surface acoustic wave ultraviolet detector by multi-physics method

Surface acoustic wave (SAW) ultraviolet (UV) detector uses a thin Zinc Oxide (ZnO) nanowire sensing layer to detect the UV light. Since the sensing layer is a photo-conducting film, the sharp change of conductivity of it under UV light illumination becomes the most important factor affecting the propagation velocity of SAW due to the electric-acoustic interaction. The dependence of the SAW propagation velocity on the photo-conductivity of the sensing layer is simulated by multi-physics method and the results are presented and discussed. It is found that the propagation velocity of SAW decreases with increasing the conductivity of the thin ZnO nanowire sensing layer and vice versa. Thus, the sensitivity of the SAW UV detector, which is defined as the decrease of the central frequency under UV light illumination, is investigated using the suggested simulation model. It is found that the UV sensitivity is proportional to the designed frequency of S AW device as well as the thickness of sensing layer to some degree. However, an abnormal phenomenon that there is an UV sensitivity peak on the sensitivity-thickness curve with much larger range of sensing layer thickness will occur according to the simulation results. These simulation results can help optimizing and designing the SAW UV detector.