High porosity and oxygen vacancy enriched WO3-x thin films for room temperature hydrogen gas sensors

Abstract

Due to the increase in demand for hydrogen in several fields, sensors that detect the presence of hydrogen gas more precisely even at room temperature (30 °C) are required for its safe use. In this work, we report the hydrogen gas sensing performance of the WO3-x thin film deposited at different oxygen partial pressures (10%, 15%, and 20%) onto SiO2/Si substrate using a radio frequency (RF) magnetron sputtering technique. To study the hydrogen gas sensing performance, Ag/WO3-x/Ag test-device is fabricated by depositing interdigitated Ag electrodes onto the WO3-x gas sensing layer via thermal evaporation. The performance of the obtained sensors is investigated at different hydrogen concentrations (100 ppm–300 ppm) and different operating temperatures (30°C–300 °C). WO3-x thin films deposited at 10% of pO2 show a maximum response of 3.40% for 100 ppm of H2 gas even at room temperature, which is due to the high crystallinity, high porosity, and the presence of more oxygen vacancies. The oxygen vacancies that are created during the reactive magnetron sputtering would enhance the hydrogen adsorption and hence superior hydrogen sensing results achieved. Herein, the response and recovery times are measured in most of the sensing conditions and the sensing mechanism has been discussed.