Preparation and properties of humidity sensor based on K-doped ZnO nanostructure

K x Zn 1−x O (X = 0%, 3%, 5%, 10%) nanowires have been synthesized through hydrothermal method and characterized by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. Dielectrophoresis nano-manipulation technique was employed to arrange the materials on pre-designed Ti/Au electrodes to fabricate the humidity sensors, and the humidity sensing properties of sensors were investigated. The experimental results show that K-doped ZnO humidity sensors exhibit more excellent humidity sensing than the undoped ZnO humidity sensor. Especially, 5% K-doped ZnO humidity sensor show the highest sensitivity, the response time reduced from 32 to 12 s, and have lower hysteresis and better reproducibility. The improvement of humidity sensing performance is explained by the increase of oxygen vacancy defects due to the K doping process. In addition, the sensing mechanism was analyzed by complex impedance spectroscopy and multilayer adsorption theory. These results demonstrate the potential application of K-doped ZnO nanowires for fabricating high performance humidity sensors.