Owing to their excellent hydrogen surface susceptibility, TiO2 thin films have been proven worthy of sensing hydrogen. However, these sensors work best at temperatures of 150-400 °C, with poor selectivity and a low response at room temperature. In this context, the novelty of this paper includes an investigation of the critical role of electrode fabrication that is found to significantly define the surface as well as the performance of a sensor. Sensors prepared with optimized conditions showed the best sensor response (SR) of ∼1.58 × 107 toward 10 000 ppm H2 with excellent linearity (R-square ∼ 0.98 for 300-10 000 ppm) at room temperature (∼20 °C). In addition, the said sensor showed a response time of ∼125 s with full baseline recovery and a selectivity factors (SF) of ∼1754, 2456, and 4723 to 1000 ppm of interfering reducing gases CH4, CO, and NH3, respectively, at 100 °C. At room temperature, the selectivity factor (for 300 ppm H2) of the sensor is ∼3.41 to 90% RH and ∼37.35 to 250 ppm oxygen, 200 ppm CO, and 1600 ppm CO2. Last but not least, our X-ray diffraction, X-ray photoelectron spectroscopy, and electrical transport characteristics enabled us to explain the high sensing mechanism on the basis of the estimated grain size, the quantitative atomic composition, the barrier at the Pt/TiO2 interface, and the thermal activation energy (also known as the intergranular barrier height) of the thin films.
Keywords: Pt/TiO2 interface; TiO2; hydrogen sensor; sputtering; thin films.