Sensitivity enhancement of hydrogen-gas sensor by sub-nm Au on Pd surface of a wireless quartz resonator

Hydrogen (H2) is an important source of next-generation energy production. The various H2 sensors developed to date cannot easily detect very low concentrations of H2 (<10 ppm) at room temperature within 100 s. In this study, we develop H2 sensors by depositing a 200-nm thick palladium (Pd) film on AT-cut quartz resonators and adding a sub-nm gold (Au) layer on the Pd surface. Moderate Au deposition on the Pd surface improves the sensitivity of the sensor by decreasing the activation energy of atomic-hydrogen migration from the surface to the subsurface. The optimal Au thickness that minimizes the activation energy is 0.5 nm. Finally, we show that the approximate detection limit at room temperature is 5 ppm.