Sol–gel derived TiO2:ZrO2 multilayer thin films for humidity sensing application

In the present work, we describe humidity sensing properties of nano-structured multilayered TiO2:ZrO2 ceramic thin films prepared by sol–gel processing. An enhancement in the sensitivity is observed for both TiO2/ZrO2 (TZ) and ZrO2/TiO2 (ZT) thin film samples that are annealed at 400 °C, due to simultaneous crystallization of ZrO2 and TiO2. The multilayered ZrO2:TiO2 thin film shows less drift and low hysteresis compared to pure TiO2. The experimental data are fitted to an equivalent circuit containing a resistance and a non-Debye capacitance in parallel. Typical response and recovery time of the sensor are 56 and 124 s, respectively. We demonstrate the possibility of a practical device without heating the humidity sensitive element for regeneration.