Dynamic humidity response of surface acoustic wave sensors based on zinc oxide nanoparticles sensitive film

摘要

ZnO nanoparticles/quartz surface acoustic wave (SAW) humidity sensors were fabricated, and their sensing performance was investigated. The pristine ZnO deposited on ST-cut quartz substrates by radio frequency magnetron sputtering is nanoparticles with grain sizes of 20-50 nm. The comparative analysis for humidity sensing applications of SAW-Love devices based on ZnO sensitive layers with different deposition pressures (0.25 Pa, 0.5 Pa, 1.0 Pa) was conducted, and their properties such as sensor sensitivity, response and recovery were studied. The sensors exhibit a good sensitivity in relative humidity (RH) from～1% RH to 95% RH. Rayleigh mode and Sezawa mode frequency responses of the sensors increase with increasing humidity. The Sezawa mode shows 2-3 times higher humidity sensitivity than its Rayleigh mode counterpart for different RH. Rayleigh and Sezawa mode of 0.5 Pa ZnO nanoparticles-based SAW-Love sensor obtains a higher average sensitivity of 237.4 Hz/% RH and 388.1 Hz/% RH, respectively. Furthermore, the measured response frequencies values decrease rapidly and returned to near the initial state after moisture off. This comparative study demonstrates that the SAW-Love based on Sezawa mode has a great potential for applications in chemo-sensors.