Sensing properties of resistive-type hydrogen sensors with a Pd–SiO2 thin-film mixture

Zigzag-shaped pure-Pd thin film and Pd–SiO2 thin-film mixture as resistive-type hydrogen sensors were deposited on cover-glass substrates through a multiple-boat thermal evaporator. Temperature dependence of the resistance of the pure-Pd resistive-type sensor showed a relative sensitivity of 3.2% at 80 °C with a temperature coefficient of the resistance (TCR) of 0.058%/°C. Sensing properties of the Pd–SiO2 resistive-type sensor responding to the presence of 1% H2/N2 are much better than those of the pure-Pd one, including a higher relative sensitivity (9%–7.7%), a faster response time (10 s–30 s), and a lower detection concentration limit (50 ppm–100 ppm). A higher dissociation rate and a faster diffusion rate due to porous-like properties and more hydrogen atoms caught due to oxygen associated with the Pd–SiO2 thin-film mixture explain why the Pd–SiO2 resistive-type sensor has a higher relative sensitivity with a shorter response time.