Effect of Rapid Thermal Annealing on Material, Electrical, and Sensing Characteristics of Ag-Doped CaTiO3-CuO Thin Film Carbon-Dioxide Gas Sensors

The effect of rapid thermal annealing (RTA) on CO 2 sensing characteristics of RF-sputtered and Ag-doped CaTiO 3 -CuO thin films has been studied in this work. The surface morphology, grain size, surface chemical states, I-V characteristics, and sensing ability of the films, have been evaluated for postdeposition RTA at different temperatures (400 °C-600 °C) and time (0-60 s). As the annealing temperature was raised, crystallinity improved and the grain size increased. Indeed, XRD revealed that RTA resulted in strong crystallographic orientation in the films. XPS analysis revealed no changes in the oxidation states and chemical composition of the material. I-V measurements show that the resistance of the film decreases as RTA temperature increases. On the other hand, the sensing characteristics reveal an optimum grain size for the best sensitivity. The films annealed at 500 °C for 60 s, leading to a grain size of about 10 nm, display the highest sensor response of 54%, when exposed to 1000 ppm of CO 2 .