Ethanol and Hydrogen Gas-Sensing Properties of CuO–CuFe2O4 Nanostructured Thin Films

Nanocrystalline CuO-CuFe₂O₄ composite thin films were developed from CuFeO₂ ceramic target using a radio-frequency sputtering method followed by a thermal oxidation process. This fabrication process helps to develop porous sensing layers which are highly desirable for solid-state resistive gas sensors. Their sensing properties toward ethanol and hydrogen gas in dry air were examined at the operating temperatures ranging from 250 °C to 500 °C. The electrical transients during adsorption and desorption of the test gases were fitted with the Langmuir single site gas adsorption model. A composite thin film with a total thickness of 25 nm showed highest response (79%) toward hydrogen (500 ppm) at the operating temperature of 400 °C. The shortest response time (τ_res) was found to be ~60 and ~90 s for hydrogen and ethanol, respectively. The dependence of the response of the sensor on gas concentration (10-500 ppm) was also studied.