Gas sensing using single wall carbon nanotubes ordered with dielectrophoresis

We demonstrate efficient NH3 detection in single wall carbon nanotubes (SWCNT) ordered by mean of dielectrophoretical process. The employed approach was to disperse the nanotubes, treated following a specific protocol, in CHCl3 and to distribute the suspension between the tracks of multifinger Au electrodes (40 μm spacing) on SiO2/Si substrates. The control of arrangement and alignment of the SWCNT bundles was achieved by applying an alternate voltage (frequency 1 MHz, 10 Vpp) during the solvent evaporation. The sensitivity for NH3 detection resulted to be strongly enhanced by the degree of SWCNT alignment between the electrodes. The sensitivity resulted enhanced also by increasing up to 80 °C the temperature of the devices. We investigated also the effect induced on the NH3 absorption/desorption processes by a gate voltage applied to the Si substrate beneath the interdigitated electrodes on the NH3. The results indicate that the sensitivity of the SWCNT-based sensor can be increased applying a negative gate voltage.