Introducing oxygen vacancies into WO 3 thin film for improving hydrogen sensing performance of Pd/WO 3-x /AAO sensors

Introducing oxygen vacancy into semiconducting metal oxides (SMOs) is a strategic approach to promote their gas sensing performances. In this paper, the WO 3-x thin films were meticulously deposited onto an anodic aluminum oxide (AAO) substrate, and the oxygen vacancies concentrations of WO 3-x thin films were changed by adjusting the ratio of flux of Ar to O 2 in magnetron sputtering process. Sequentially, a layer of palladium (Pd) was deposited on the WO 3-x /AAO films, creating a nano-mesh structured hydrogen sensor with Pd as the catalytic element. The resulted amorphous WO 3-x samples with varying concentration of oxygen vacancies were thoroughly analyzed using XPS and ESR, which confirmed that the oxygen vacancies concentration escalated with an increase in the ratio of flux of Ar to O 2. The hydrogen sensitivity of prepared Pd/WO 3-x /AAO sensors were examined. Our findings revealed an enhancement in hydrogen sensitivity for the sensors with an optimal concentration of oxygen vacancies. However, an excess of these vacancies was found to deteriorate their hydrogen sensing performance. Notably, the optimized Pd/WO 3-x /AAO sensor exhibited a marked response even at a hydrogen concentration as low as 100 ppb, demonstrating its high sensitivity and selectivity towards hydrogen detection.