CMOS-compatible plasmonic hydrogen sensors with a detection limit of 40 ppm

Sensing of leakage at an early stage is crucial for the safe utilization of hydrogen. Optical hydrogen sensors eliminate the potential hazard of ignition caused by electrical sparks but achieve a detection limit far higher than their electrical counterparts so far. To essentially improve the performance of optical hydrogen sensors in terms of detection limit, we demonstrate in this work a plasmonic hydrogen sensor based on aluminum-palladium (Al-Pd) hybrid nanorods. Arranged into high-density regular arrays, the hybrid nanorods are capable of sensing hydrogen at a concentration down to 40 ppm, i.e., one thousandth of the lower flammability limit of hydrogen in air. Different sensing behaviors are found for two sensor configurations, where Pd-Al nanorods provide larger spectral shift and Al-Pd ones exhibit shorter response time. In addition, the plasmonic hydrogen sensors here utilize exclusively CMOS-compatible materials, holding the potential for real-world, large-scale applications.