Sputtered PdO decorated TiO₂ sensing layer for a hydrogen gas sensor

We report a sputtered PdO decorated TiO₂ sensing layer by radiofrequency (RF) sputtering methods and demonstrated gas sensing performance for H₂ gas. We prepared sputtered anatase TiO₂ sensing films with 200 nm thickness and deposited a Pd layer on top of the TiO₂ films with a thickness ranging from 3 nm to 13 nm. Using an in situ TiO₂/Pd multilayer annealing process at 550°C for 1 hour, we observed that Pd turns into PdO by Auger electron spectroscopy (AES) depth profile and confirmed decorated PdO on TiO₂ sensing layer from scanning electron microscope (SEM) and atomic-force microscope (AFM). We also observed a positive sensing signal for 3, 4.5, and 6.5 nm PdO decorated TiO₂ sensor while we observed negative output signal for a 13.5 nm PdO decorated one. Using a microheater platform, we acquired fast response time as 11 sec and sensitivity as 6 μV/ppm for 3 nm PdO under 33 mW power.