Contribution of lanthanum doping to the fast humidity sensing capability of zinc oxide nanostructured thin films

This paper reports a comprehensive investigation of the humidity sensing capabilities of undoped and lanthanum (La) doped zinc oxide (ZnO) nanostructured thin films. Undoped and 1–4 mol% La doped ZnO nanoparticles were synthesized via the sol–gel method. The spin coating technique was applied for the production of nanostructured thin films. The surfaces of the films containing capillary nanopores and nanoparticles that facilitate humidity sensing, and their hexagonal wurtzite structure were revealed by scanning electron microscopy and X-ray diffraction findings. The zinc, oxygen and lanthanum components of the produced nanostructures were confirmed by energy dispersive X-ray spectra. The 3 mol% La doped ZnO sensor exhibited noticeable humidity sensitivity and sensing performance, evidenced by 244.76 times humidity sensitivity and fast response/recovery times of 1.0 s/5.5 s. This research not only reveals the capabilities of La doped ZnO nanostructures in humidity sensing, but also establishes a pivotal concentration benchmark for optimal sensor efficiency, making a significant contribution to sensor technology.