Highly sensitive hydrogen sensor with a nano bumpy structured Pd film

In this study, a highly sensitive hydrogen gas sensor of the multi-layer and micro-heater type was designed and fabricated using a microelectromechanical system (MEMS) process. The sensing layer of palladium deposited in the middle of the sensor platform was modified to be a nano-bumpy structure using nanosized polystyrene beads. The root-mean square roughness measured by AFM was 9.07 nm for the nano-bumpy Pd structure whereas that of the simple Pd thin film was 0.98 nm. At hydrogen gas concentration of 2,000 ppm, the sensitivity of the simple Pd thin film and the Pd nano-bumpy film was 0.638 and 1.045, respectively. The sensitivity of the Pd nano-bumpy film was much higher than that of the Pd thin film due to the very high surface-to-volume ratio of the nano-bumpy Pd structure.