NH3 sensing properties of ZnO thin films prepared via sol-gel method

An 80 nm-thick ZnO film was prepared via the sol-gel method at 500 °C using zinc acetate, 2-methoxyethanol, and monoethanolamine as precursors. Characterization of the film showed that it was composed of 20-30 nm sintered ZnO nanoparticles with good crystallinity. The NH3 sensing properties of gas-sensing devices with a 5 μm gap that utilized the prepared ZnO film were examined. The highest sensor response (57.5%) was achieved with 600 ppm NH3 in air at 150 °C. The response and recovery times were 160 s and 660 s, respectively. This study also examined the effects of NH3 and oxygen concentration as well as the temperature on the sensor response performance. The findings show that oxygen plays an important role in the conductivity of ZnO thin films, and thus affects the sensor response toward NH3.