Co-Evaporated CuO-Doped In 2 O 3 1D-Nanostructure for Reversible CH 4 Detection at Low Temperatures: Structural Phase Change and Properties.

In order to improve the sensitivity and to reduce the working temperature of the CH ₄ gas sensor, a novel 1D nanostructure of CuO-doped In ₂ O ₃ was synthesized by the co-evaporation of Cu and In granules. The samples were prepared with changing the weight ratio between Cu and In. Morphology, structure, and gas sensing properties of the prepared films were characterized. The planned operating temperatures for the fabricated sensors are 50-200 °C, where the ability to detect CH ₄ at low temperatures is rarely reported. For low Cu content, the fabricated sensors based on CuO-doped In ₂ O ₃ showed very good sensing performance at low operating temperatures. The detection of CH ₄ at these low temperatures exhibits the potential of the present sensors compared to the reported in the literature. The fabricated sensors showed also good reversibility toward the CH ₄ gas. However, the sensor fabricated of CuO-mixed In ₂ O ₃ with a ratio of 1:1 did not show any response toward CH ₄ . In other words, the mixed-phase of p- and n-type of CuO and In ₂ O ₃ materials with a ratio of 1:1 is not recommended for fabricating sensors for reducing gas, such as CH ₄ . The gas sensing mechanism was described in terms of the incorporation of Cu in the In ₂ O ₃ matrix and the formation of CuO and In ₂ O ₃ phases.