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 H-2 for use in the detection of hydrogen (H-2) 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 (similar to 100nm (W)) formed on the edges of the grating structure by expansion and contraction of the film through a few cycles of H-2 absorption and desorption. Such nanogaps are crucial to the performance of the sensors. The H-2 sensors were found to exhibit a fast response time (similar to 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. (C) 2015 Elsevier B.V. All rights reserved.