2-Dimentional photoconductive MoS2 nanosheets using in surface acoustic wave resonators for ultraviolet light sensing

2-Dimensional (2D) wide band-gap semiconductor molybdenum disulfide (MoS2) nanosheets as an ultraviolet (UV) photo-conductive material were used in surface acoustic wave (SAW) resonators for UV light sensing. A SAW resonator based on zinc oxide (ZnO) piezoelectric film deposited on glass through radio frequency (RF) magnetron sputtering technique was prepared, in which the sub-microscale gold/chromium (Au/Cr) interdigital transducers (IDTs) and grating reflectors were fabricated onto the ZnO surfaces using the electron beam lithography and lift-off techniques to form the IDTs/ZnO/glass-based SAW resonator with a working frequency at ∼1.02 GHz. The MoS2 nanosheets prepared by electrochemical lithiation process were coated on IDTs region to form a highly sensitive SAW UV sensor, exhibiting an interesting photoresponse behavior to UV radiation. A maximum frequency shift of ∼3.5 MHz was found under 365 nm UV radiation with power intensity of 1.466 mW/cm2, which is attributed to the high resonant frequency (in GHz) and high specific surface area of photo-conductive MoS2 nanosheets. It is suggested that the adsorption and desorption of oxygen on MoS2 nanosheets play the dominant roles in the frequency-upshift due to mass loading effect and acoustoelectric effect, meanwhile, acoustoelectric effect also creates the SAW attenuation.