Studies of Resistive-type Hydrogen-Sensitive Sensors Using Pd-Based Thin Films

Zigzag-shaped Pd-based thin films (pure Pd and Pd-SiO2 mixture with thickness ranged from 10 nm to 100 nm deposited on cover-glass substrates were used to fabricate resistive-type hydrogen sensors. It is found that relative sensitivities are independent of the thin-film thickness and are 10%, 7.4%, 6.1%, and 5% for the pure-Pd sensor in 2%, 1.5%, 1%, and 0.5% H-2/N-2, respectively. However, its response time (t(a)) is substantially influenced by the thin-film thickness for pure-Pd resistive-type sensor. t(a) is measured with a thickness coefficient of 0.14 s/nm in 2% H-2/N-2 while it is 0.5 s/nm in 1% H-2/N-2. Compared to the pure-Pd sensor, the Pd-SiO2 sensor has a shorter response time (20 s to 33 s) and a higher relative sensitivity (8.7% to 6.1%) in 1% H-2/N-2. In 3% H-2/N-2, relative sensitivity is even as high as 15.2% with a response time of 10 s.