Al2O3:Cr2O3:CuO (1:1:1) thin film prepared by radio frequency magnetron sputtering technique: a promising material for high sensitive room temperature ammonia sensor

Abstract

In the present work, we report the room temperature gas sensing behavior of Al2O3:Cr2O3:CuO (1:1:1) thin films prepared by radio frequency (RF) magnetron sputtering technique for the first time. X-ray diffraction study confirmed the presence of tetragonal phase Al2O3:Cr2O3:CuO in the deposited film. X-ray photoelectron spectroscopic data confirmed the predominant presence of Al3+, Cr3+ and Cu2+ states in the films. The annealing temperature induced shift in absorption edge may be due to the morphological change and the improvement in crystallinity of the films. The gas sensing study shows the excellent sensitive behavior of the films to NH3 gas at room temperature. Interestingly, the annealed film was very sensitive to NH3 gas even at a very small concentration of 1 ppm, while the as-deposited one was responded at 10 ppm level. The maximum response of 99.17% was observed for 75 ppm of NH3 gas at room temperature. The sensor uphold its initial response without any decrease upon 10 repeated cyclic operation and also retains 94% and 91% of its initial response after 6 months duration for as-deposited and annealed films, respectively, which confirms the high operational stability and repeatability of Al2O3:Cr2O3:CuO (1:1:1) thin film in the detection of ammonia gas.