Effects of different morphologies of ZnO films on hydrogen sensing properties

Abstract

This paper describes the characteristics of chemiresistor hydrogen (H2) sensors with different ZnO film structures in which ZnO dense films, nanoparticles (NPs), and nanorods (NRs) were prepared by RF magnetron sputtering, the sol–gel method, and the hydrothermal method, respectively. These were decorated with a Pt NP catalyst to investigate the performance of devices comprised of these structures. The effects of the ZnO morphology and operating temperature on the gas sensing behavior of the sensor are reported in detail. The various ZnO film morphologies, which contributed significantly to differences between sensors, play a very important role in enhancement of the supported Pt catalyst area and initial oxygen absorption on the ZnO surface. ZnO dense films prepared by sputtering showed the fastest response with a 13.5 % resistance variation at 1,000 ppm H2 because gas adsorption occurred only on the film surface. The sensor with ZnO NRs showed a slower response, but the highest change in resistance of 65.5 % occurred at 1,000 ppm H2 at room temperature. H2 sensing performance of the chemiresistor sensors was improved due to the Pt catalyst, which was more efficient in dissociating H2 gas molecules even at low temperature. The best chemiresistor sensor was fabricated using ZnO NRs and had a response time of approximately 10 s, a 27 s recovery time, and an 81.5 % change in resistance at 200 °C.