A hydrogen sensor based on orientation aligned TiO_2 thin films with low concentration detecting limit and short response time

摘要

Hydrogen sensors with high sensitivity, rapid response and low cost are urgently demanded in today's industry. In this work, we reported our research on the fabrication process and the relevant sensing mechanisms of a TiO_2 film based hydrogen sensor which showed an excellent performance at room temperature in air. The sensor, prepared by hydrothermal methods with a seed layer being introduced during the growth of the thin films, exhibited the concentration detection limit as low as 1 ppm and the response time as short as 9 s. Structural analysis revealed that the introduction of the seed layer resulted in a significant improvement in the quality of the TiO_2 thin film, which was intimately related to the sensing properties. The dynamical response process was studied and the corresponding sensing mechanisms were analyzed in detail. It was found that, in addition to the generally accepted Schottky barrier mechanism, the adsorption of H_2 molecules at (002) surface of the TiO_2 thin film played a key role in achieving such a low detection limit and a short response time for the sensor.