Development of room temperature sensor based on high quality rhombohedral Al2O3:Cr2O3 (1:1) thin film with bone like morphological feature for ultrasensitive detection of NH3 gas

This paper describes the successful preparation of high quality (104) oriented Al 2 O 3 :Cr 2 O 3 (1:1) thin film with rhombohedral phase and bone like surface morphology by RF magnetron sputtering technique. Compositional purity and its corresponding chemical states of the elements (Al 3+ and Cr 3+ ) present in the deposited films were ascertained by EDX and XPS analyses, respectively. In particular, the film deposited with 300 W RF power not only possess unique morphology (bone like morphology), but also exhibits superior gas sensing performance towards NH 3 at room temperature due to its very high surface-to-volume ratio, which provide a more reaction site for NH 3 gas molecules. Due to this unique morphological feature, the 1000 °C annealed Al 2 O 3 :Cr 2 O 3 (1:1) film exhibited the good selectivity, long-term stability, high sensitivity (sensitivity = 4.14), excellent sensor response (SR = 99.7% for 100 ppm) for diverse range of ammonia concentrations and the film has an ability to respond even at very low concentration (1 ppm level) at room temperature. The probable gas sensing mechanism was also discussed.