Al-Sn doped ZnO thin film nanosensor for monitoring NO2 concentration

The metal oxide semiconductor gas sensor technology is robust and has quick response times. In this work, aluminium and tin co-doped zinc oxide (ASZO) thin films were synthesized by a sol-gel dip-coating process as sensors for the greenhouse gas nitrogen dioxide (NO2). The prepared ASZO thin films were characterized using such techniques as X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and photoluminescence (PL) emission studies in order to analyze the elemental confirmation, particle size, surface roughness and optical emission properties, respectively. The XRD data reveals the hexagonal structure of ASZO and that the preferential orientation is along 2θ = 36.19°. SEM images of the ASZO thin film exhibit rod-like formations of ASZO on the substrate. The ASZO films show enhanced sensing behaviour, sensing NO2 gas even at 2 ppm at an operating temperature of 170 °C. The response and recovery times were determined to be 30 and 20 s, respectively.