Surface acoustic wave H2 sensor on silicon substrate

A surface acoustic wave (SAW) hydrogen sensor implemented on a silicon substrate is presented. The device is based on the changes produced in the phase velocity of SAWs propagating along a multilayered Pd/ZnO/SiO₂/Si structure by H₂ absorption and desorption in the selectively sorbent Pd film. Several devices have been made and tested. The time response and the sensitivity of the devices on exposure to different concentration of H₂ in N₂ are reported for two different values of the thickness of the Pd film. Measurements have shown a high response of the device on exposure to H ₂ concentrations in N₂ in the range 50-10000 p.p.m. The frequency of operation, the electrical performances of the device, and the fabrication technology involved have been optimized in view of a future integration of the electroacoustic structure and of the electric signal-processing circuitry on the same Si substrate