Carbon Nanotube-SnO2 Composite Gas Sensor Prepared by Electron beam Evaporation

Carbon nanotube (CNT) is a useful material for gas sensing applications because of its high surface to volume ratio structure. In this work, multi-wall CNTs are incorporated into tin oxide thin film by the means of powder mixing and electron beam evaporation and the enhancement of gas-sensing properties is presented. The CNTs were combined with SnO₂ powder with varying concentration in the range of 0.25-5% by weight and electron beam evaporated onto glass substrates. From AFM and TEM characterization, CNT inclusion in SnO₂ thin film results in the production of circular cone protrusions of CNT clusters or single tube coated with SnO₂ layer. Experimental results indicate that the sensitivity to ethanol of SnO₂ thin film increases by the factors of 3-6. However, if the CNT concentration is too high, the sensitivity is decreased. Moreover, the CNT doped film can operate with good sensitivity and stability at a relatively low temperature of 250-300 degC. The improved gas-sensing properties should be attributed to the increasing of metal oxide surface adsorption area produced by CNT protrusion