Nanogap-based electrical hydrogen sensors fabricated from Pd-PMMA hybrid thin films

Hybrid thin films, in which a Pd thin film was sandwiched between thin poly(methyl methacrylate) PMMA layers, were prepared on a flexible substrate using a combination of sputtering and spin coating. In real-time electrical response tests to H2, Pd-PMMA hybrid nanogap sensors operated in an on–off manner for both air and N2 carriers. Due to the selective penetration of H2 and the density reduction of the cracks that formed in the trilayer of the hybrid thin films, the detection limit of the hybrid nanogap sensors (6000 ppm H2 in air and 600 ppm H2 in N2) was drastically reduced compared to that of Pd nanogap sensors without PMMA layers. Hybrid thin films have great promise in realizing sensors that can be used in air without additional filter system.