Fabrication of single-walled carbon nanotube-based highly sensitive gas sensors

A highly sensitive single-walled carbon nanotube (SWCNT)-based ammonia (NH3) gas detector is manufactured by orderly assembling SWCNT using the dielectrophoretical (DEP) technology. Atom force microscopy (AFM) and scanning electron microscopy (SEM) images revealed that SWCNTs were assembled between the microelectrodes. SWCNTs were affected by the electrophoretic force which was carried out by the related theoretical analysis in a nonuniform electric field. The SWCNT field effect transistors geometry was obtained. The electrical performance of NH3 gas sensor with the SWCNT field effect transistors geometry was tested before and after the adoption of NH3 at room temperature. Experimental results indicated that the efficient assembly of SWCNT was obtained by the applied alternating current voltage with frequency of 2 MHz and amplitude of 10 V. The SWCNTs-based gas sensor had high sensitivity to NH3, and the electrical conductance of NH3 gas sensor reduced two times after interaction with NH3. The SWCNTs surface gas molecules were removed by means of ultraviolet ray irradiation for 10 min. Hence, the fabricated NH3 gas sensor could be reversible. There is a clear evidence that the adsorption of NH3 on the SWCNT channel is easy to be realized. Our theoretical results are consistent with recent experiments.