Fig. 1
The graphene plasmon device for gas identification. a Experimental scheme of our device. A metal chamber with a piezometer was used for precise control of gas parameters. Plasmons in a graphene ribbon array were excited using an incident infrared beam and tuned in situ by electrostatic doping through a gate voltage (Vg). The plasmon resonances were coupled with molecular excitations, thus probing the rotational–vibrational spectral fingerprints of gas molecules. b Raman spectrum of the graphene nanoribbons (GNRs) compared with one of an unpatterned graphene sheet. c Plasmonic field confinement of a typical GNR with ribbon width of 70 nm. d Experimental (black curve) and simulated (red curve) extinction spectra of GNRs for SO2 gas identification. The molecular responses on the plasmonic peaks are marked with solid green areas. The vertical gray lines indicate the rotational-vibrational modes (P, R) of SO2. The schematic of the vibrational mode is indicated with arrows in the central inset. The graphene ribbon width is 100 nm with a filling factor of 80%, ΔVCNP of 30 V, and SO2 of 4000 ppm at 1 atm. The simulation adopts an effective ribbon width of 70 nm and Fermi energy of 0.3 eV to best fit the experimental spectra. Upper inset: oscillator strength vs concentration for the P and R modes of SO2. The differences between experimental and simulated spectra may originate in a narrower ribbon width and lower EF of the fabricated nanoribbons
