Effect of doping level on the photoconduction and chemiresistive ethanol gas sensing of lanthanum-doped CuO films

Undoped and lanthanum (La)-doped copper oxide (CuO) thin films were prepared by the nebulizer spray pyrolysis technique. The X-ray diffraction analysis revealed that the effective doping of lanthanum does not alter the monoclinic crystalline structure of copper oxide thin films. Raman spectra confirmed the crystalline quality of undoped and La-incorporated CuO films. From, scanning electron micrograph images, the La-doped CuO films exhibit spherical particles. Energy dispersive X-ray analysis confirmed the existence of copper, lanthanum and oxygen elements. The doping of La-substituted CuO films showed a minimum bandgap when compared to undoped CuO film. The oxidation states of Cu 2p, La 3d and O 1s elements were observed. The electrical resistivity of the films was considerably decreased due to the doping of La ions in CuO matrix. The photoluminescence spectra show that the doping of La ions increases the defect states and shows increased intensity. The time resolved photoluminescence analysis revealed that an extended carrier lifetime was observed for the La-doped films. The La-doped CuO sensors achieved a superior gas sensing performance at room temperature and exhibited quick response and recovery times, suggesting that the sensor has the potential for the detection of harmful volatile gases in real-world applications. The photoconductive investigation revealed that the La-doped CuO films exhibited higher charge-transporting properties and increased light-harvesting ability. This study sheds light on designing gas sensors working under ambient conditions and photosensors for optoelectronic devices.