A study on the aging of ultra-thin Palladium films on SAW hydrogen gas sensors

Traditionally, low-powered, room temperature sensing of gaseous hydrogen (H2) is difficult. With renewed interest in H2 as a source of energy, there is a need for reliable, energy-efficient sensors. A potential solution can be found in using surface acoustic wave (SAW) devices, which have been implemented as passive, wireless RFID tag-sensors. Thus, in concept, it is advantageous to develop a SAW device with H2 sensing capabilities. Prior experiments have successfully demonstrated a passive SAW-based H2 gas sensor by placing an ultra-thin Palladium (Pd) film (<50Å) in the propagation path [1–3]. These sensors have an instantaneous response and a significant fractional change in SAW propagation loss; however, the lifetime of these sensors are still unknown. Hence, the objective of this study was to examine the influence of aging of ultra-thin Pd films on the usable life of passive SAW H2 gas sensors.