Improved semiconducting CuO/CuFe2O4 nanostructured thin films for CO2 gas sensing

• Thin films were deposited by sputtering from a CuFeO2 target.
• Self-organized p-CuO/n-CuFe2O4 bilayer could be obtained by a two steps process.
• This nanostructured bilayer was sensitive to 5000 ppm CO2.
• Measurement temperature, thickness and microstructure of the film were optimized.
• A response between 45% and 50% could be obtained with Ag as additive.

Promising results on the behavior of CuO/CuFe2O4 sputtered thin films as a sensing material under carbon dioxide atmospheres are presented in this article. More specifically, we report the effects of preparation parameters and microstructure of the sensing layer on the response to CO2. FEG-SEM images and XPS measurements revealed the two-stacked layers rearrangement of samples after air annealing as a key parameter in gas sensing test. The influence of the sensing layer thickness and the influence of Ag as an additive in the film on the response are also reported. The best response was obtained at the optimal operating temperature of 250 °C with a thin film deposited under low argon pressure and low target-to-substrate distance, reaching 40% towards 5000 ppm of CO2.