Surface-Enhanced Infrared Absorption: Pushing the Frontier for On-Chip Gas Sensing

Surface-enhanced infrared absorption (SEIRA) is capable of identifying molecular fingerprints by resonant detection of infrared vibrational modes through the coupling with plasmonic modes of metallic nanostructures. However, SEIRA for on-chip gas sensing is still not very successful due to the intrinsically weak light-matter interaction between photons and gas molecules and the technical challenges in accumulating sufficient gas species in the vicinity of the spatially localized enhanced electric field, namely, the "hot-spots", generated through plasmonics. In this paper, we present a suspended silicon nitride (Si3N4) nanomembrane device by integrating plasmonic nanopatch gold antennas with metal organic framework (MOF), which can largely adsorb carbon dioxide (CO2) through its nanoporous structure. Unlike conventional SEIRA sensing relying on highly localized hot-spots of plasmonic nanoantennas or nanoparticles, the device reported in this paper engineered the coupled surface plasmon polaritons in the metal Si3N4 and metal MOF interfaces to achieve strong optical field enhancement across the entire MOF film. We successfully demonstrated on-chip gas sensing of CO, with more than 1800X enhancement factors by combining the concentration effect from the 2.7 pm MOF thin film and the optical field enhancement of the plasmonic nanopatch antennas.