Highly sensitive thin film NH3 gas sensor operating at room temperature based on SnO2/MWCNTs composite

Abstract

Abstract A SnO 2 /MWCNTs composite-based NH 3 sensor working at room temperature was fabricated by thin film microelectronic technique. The gas-sensitive composite thin film was prepared by using both commercially available multi-walled carbon nanotubes (MWCNTs) and nanosized SnO 2 dispersion. Microstructure and surface morphology of the composite were investigated and they revealed that the MWCNTs were still present and well embedded by SnO 2 particles in the composite powder as well as in the composite thin film at calcination temperatures up to 550 °C. The effect of the preparation process of the sensitive composite thin film on gas-sensing properties was examined, and the preparation process parameters such as MWCNTs content, MWCNTs diameter, calcination temperature, and film thickness were optimized. At room temperature, the optimal composite sensor exhibited much higher response and faster response-recovery (less than 5 min) to NH 3 gas of concentrations ranging from 60 to 800 ppm, in comparison with the carbon nanotubes-based NH 3 sensor. Based on the experimental observations, a model of potential barrier to electronic conduction at the grain boundary for the CNTs/SnO 2 composite sensors was also discussed.