Kinetic control of nanocrack formation in a palladium thin film on an elastomeric substrate for hydrogen gas sensing in air

We report the effects of various tensile velocities on the nanocrack formation in a Pd thin film on an elastomeric polydimethylsiloxane substrate and its H₂ sensing properties. A tunable nanocrack along the x and y axes was created by mechanical stretching/compression cycles with varying tensile velocities. From the microstructural analyses, we found that the tensile velocity has a significant effect on the crack density but little effect on the average crack width. The Pd nanogap sensor prepared under a high tensile velocity showed a high performance with a low detection limit of 500 ppm of H₂ in air. Our results indicate that the higher crack density with the narrow nanocrack width (55-100 nm) propagated over the entire film provides the enhanced H₂ sensing properties in air.