Highly effective room-temperature ethanol gas-sensing performance of lanthanum-doped zinc oxide thin films

This paper reports the room-temperature ethanol gas-sensing performance of lanthanum (La)-doped zinc oxide (ZnO) nanostructured thin films and the La dopant concentration effects on this performance. ZnO nanoparticles, both undoped and La-doped, were produced through the sol–gel process, with La concentrations set at 0, 1, 2, 3, and 5 mol%. The production of thin films was carried out by the dip-coating technique on soda-lime glasses. X-ray diffraction patterns confirmed that the structure of the prepared films was hexagonal wurtzite and the predominant orientation was (002). The film surfaces, consisting of nanosized grains and pores exhibiting an evenly distributed and homogeneous morphology, were observed by scanning electron microscopy. Energy-dispersive X-ray analyses revealed the zinc, lanthanum, and oxygen contents of the produced films and their stoichiometric ratios. The room-temperature ethanol-sensing performances of the fabricated sensors were determined by measuring the electrical resistance changes at various ethanol concentrations (10, 25, 50, and 100 ppm). La doping significantly improved the ethanol-sensing performance of ZnO. 1 mol% La-doped ZnO exhibited the most effective room-temperature ethanol gas-sensing performance, and therefore, 1 mol% La was identified as the optimal doping concentration. Its sensing response was measured to be 117.1, with a response/recovery time of 24 s/28.6 s. This study revealed that La-doped ZnO nanostructured thin films are a remarkable material for improving highly effective ethanol gas sensors operating at room temperature.