Advanced hydrogen sensitive material WO3 and its optical sensing properties

The correlation between reflected light intensity and hydrogen concentration is the basis of the end-face type hydrogen sensor with WO3 coating. However, the changes of optical properties of WO3 under different hydrogen concentrations have not been fully investigated, and its hydrogen sensitivity mechanism is still unclear, which restricts the improvement and optimization of hydrogen sensing performance. Therefore, the relationship between hydrogen concentration and Refractive Index (RI) of WO3 is established in this paper to explore the hydrogen sensitive mechanism. The experimental results show that the RI of WO3 changes when hydrogen is introduced, and the RI varies under different hydrogen concentration. Since there is a certain mathematical relationship between the RI value and the reflectivity of the films, the RI changes measured by ellipsometer is further verified by the intensity-tracing experiments results. Hence, we can clarify that the hydrogen sensitivity mechanism of WO3 is related to its RI changes under different hydrogen concentration, which will provide a basis for the further research and applications.