Palladium nanogap-based H₂ sensors on a patterned elastomeric substrate using nanoimprint lithography

Here we report a new nanogap formation manner at edges of a palladium (Pd) thin film on highly patterned arrays of an elastomeric PDMS substrate fabricated nanoimprint lithography (NIL) by absorption/desorption cycles of H₂ for use in the detection of hydrogen (H₂) gas. A 10-nm-thick Pd layer was deposited on the patterned PDMS substrate using an ultra-high vacuum DC magnetron sputtering system. The Pd nanogaps (∼100 nm (W)) formed on the edges of the grating structure by expansion and contraction of the film through a few cycles of H₂ absorption and desorption. Such nanogaps are crucial to the performance of the sensors. The H₂ sensors were found to exhibit a fast response time (∼1 s), low detection limit (0.1%), wide linear range (0.1-2%), and an ON-OFF switching operation in air. These properties are attributed to the synergistic combination of nanogap break junction control in Pd and the patterned elastomeric substrate.