Hydrogen detection using SiC/Pd metasurfaces

Although Mid-infrared (mid-IR) sensing is powerful for detecting chemical species as it directly probes molecular vibrations, conventional sensors suffer from weak light–matter interaction and limited sensitivity for low-density gases such as Hydrogen. Phonon polariton, light–matter quasiparticles formed by infrared photons coupling with lattice vibrations in polar materials, overcomes this challenge and offers highly confined light-matter interaction and strong field confinement with low optical losses. Here, we develop a generation sensor based on Silicon Carbide (SiC) metasurfaces with an ultrathin palladium (Pd) layer to achieve high sensitivity Hydrogen gas detection in the mid-IR region at room temperature and pressure. When Hydrogen interacts with Pd, phonon polariton resonances shift due to palladium hydride formation and small changes in dielectric and narrow band, highly sensitive responses are observed across Hydrogen concentration from 0.1% to 4%. We demonstrate that even unpatterned SiC/Pd substrates enable the observation of the Pd phase transition into palladium hydride (PdHx) in the mid-IR region. Furthermore, we use Mie theory to model the electromagnetic response and absorption cross-section of the core-shell nanostructure to compare their coupling with the Pd layer and their efficiency. This reversible, self-calibrated gas sensor, driven by phonon polariton, can provide a highly selective and sensitive detection mechanism with minimal environmental impact.