Fabrication of high-performance RT-NH3 gas sensor based on Cu and La co-doped ZnO films through a facile drop-casting method

Abstract

In this work, undoped ZnO, 2 % Cu-doped ZnO, 2 % La-doped ZnO and 2 % (Cu:La) co-doped ZnO thin films are deposited on glass substrates using the facile drop-casting method, and their physical characteristics were investigated for the gas sensing application. The X-ray diffraction (XRD) patterns confirmed the hexagonal wurtzite structure and increase in crystallinity for the doped samples. Field Emission Scanning Electron Microscopy (FESEM) images revealed a significant change in morphology from the granular particles to densely packed nanoplates-like morphology for (Cu:La) co-doped ZnO. The doped samples exhibited a red shift in absorption edge and shrinkage of the optical bandgap. Multiple emission peaks in photoluminescence (PL) spectra indicated the presence of defect level in the material. It was discovered that Cu-doped and La-doped ZnO thin films had a considerable NH3 sensing response at ambient temperature. The gas response was remarkably enhanced to 341 % for (Cu:La) co-doped ZnO film and a quicker response/recovery time of 80/10 s for 250 ppm NH3. The (Cu:La) co-doped ZnO can serve as a feasible alternative for pure ZnO gas sensors.