Development of highly sensitive Al, Ga, and In-doped ZnO films by the drop casting method for NH3 gas sensing

Abstract

This article proposes 2 wt% of aluminum, indium, and gallium-doped ZnO thin film samples for ammonia gas sensors. Using a wet chemical approach, samples of ZnO and aluminum, indium, and gallium-doped ZnO were produced and coated as thin films using the drop cast method. XRD was used to determine the structural characteristics, revealing the polycrystalline composition of the samples. FESEM was used to undertake morphological analyses, which showed that the samples are inhomogeneous and non-uniform. FTIR analysis verifies the functional groups of the ZnO samples. The optical analysis confirmed the variation in the band gap of the ZnO sample by Al, Ga, and In doping. A Keithley source meter was used to test the prepared samples for ammonia gas detection. At ambient temperature, the constructed In-doped ZnO had a high sensitivity of 384% with a short rise time of 51 s, and a fall time of 19 s at 250 ppm of target gas ammonia (NH₃) concentration. Similarly, the In-doped ZnO sample demonstrated good linearity, selectivity, and repeatability, which offers an efficient gas sensor.