Pt- and Ag-Decorated Carbon Nanotube Network Layers for Enhanced NH3 Gas Sensitivity at Room Temperature

Multi-walled carbon nanotubes (CNTs) were directly grown on alumina substrates patterned with Pt interdigitated electrodes by chemical vapor deposition method to fabricate gas sensor. Pt and Ag thin layers with nominal thicknesses of 2 and 4 nm were coated on the CNT layer by evaporation method to modify the CNT properties. The gas sensing results showed that the CNT/Pt- and CNT/Ag-based sensors exhibited enhanced sensitivity to NH3 gas at room temperature. The responses of the CNT/Pt (3.0%) and CNT/Ag (6.9%) sensors with a 4 nm thick metallic layer to 70 ppm NH3 were higher than that of pristine CNT sensor (1.5%).