Fast response characteristics of hydrogen sensors based on Pd nanoparticle films with controlled coverage

The response time of the quantum conductance-based hydrogen sensor fabricated from films consisting of closely spaced palladium nanoparticles formed with cluster beam deposition was investigated. The dependence of the response time on the coverage-regulated nanoparticle size, as well as the hydrogen pressure, was determined. At low hydrogen pressure, the response time is dominated by the hydriding time of the larger Pd nanoparticles. Fast response as short as 3 s to 1,000 Pa H2 could be realized with the lower coverage nanoparticle film, with a sensitive change of the relative conductance as high as 70 %. At 10 kPa hydrogen pressure, subsecond hydrogen response could be realized. With the increase of the hydrogen pressure, the response time of the devices becomes longer and longer as determined by the hydriding time of the Pd nanoparticles involved in the smaller size population of the size distribution, and approaches the same value for the hydrogen sensors with different nanoparticle coverages. The abnormal increase of the response time accompanied by the formation of the α + β coexistence phase of PdH x was also investigated.