Performance of alkali metal (Li/Na): ZnO thin films for NO2 gas sensing

Abstract

Metal Oxide Semiconducting (MOS) gas sensors based on ZnO are extensively explored due to their exceptional physicochemical properties. Here, prepared films were characterized through XRD, FESEM, and Hall measurements to verify the physical as well as electrical properties. NO2 gas sensing performance of undoped and alkali-metal (Li/Na):ZnO films are evaluated. The operating temperature, sensitivity, and response/recovery time of prepared sensors towards nitrogen dioxide(NO2) were conducted. Through a comparative analysis of NO2 gas sensing activity of pure and 1 wt% of alkali metal (Li/Na) doped ZnO thin films. Lithium-doped ZnO sensors were found to exhibit higher sensitivity and rapid response/recovery time. Fabricated sensors detected NO2 test gas at 15 ppm, which is lower than the exposure limit (20 ppm). The gas sensing mechanism involving adsorption/desorption of the species on the surface of the sensor is also proposed.