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

Abstract

A SnO2/MWCNTs composite-based NH3 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 SnO2 dispersion. Microstructure and surface morphology of the composite were investigated and they revealed that the MWCNTs were still present and well embedded by SnO2 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 NH3 gas of concentrations ranging from 60 to 800 ppm, in comparison with the carbon nanotubes-based NH3 sensor. Based on the experimental observations, a model of potential barrier to electronic conduction at the grain boundary for the CNTs/SnO2 composite sensors was also discussed. © 2007 Elsevier B.V. All rights reserved.