Passivation of Metal-Nanotube interfaces using SiO2/Single-Wall Carbon Nanotube Composites for Toxic Gas sensor Applications

Abstract

In nanotube based gas sensors, the gas detection characteristics generally depend upon the contact barrier characteristics, between the metal electrode and the nanotube contact, especially for the single-wall nanotube (SWCNT) thin film gas sensors. Gas molecules absorbed at the metal electrode-SWCNT interface caused sensitivity degradation by forming non-ohmic contacts and erosion of the contact metal surface forms barriers at the interface reducing contact reliability. Here, we present a method of utilizing sol-gel based SiO2-SWCNT mixing solution coated on the metal and the SWCNT thin film contact area for enhancement of mechanical, thermal, chemical and humidity stabilities of the metal-SWCNT interface. We dispersed the specific amount of SWCNT into the SiO2 sol-gel solution using ultrasound agitation. Electrophoresis was used to attract the nanotubes in solution to the metal-SWCNT interface leaving the sol-gel to completely encapsulate the contact area. Then, the sample was annealed at 650℃ for 2 minutes for crystallization. We found the SiO2/SWCNT composite film formed on the metal-SWCNT contact improves the mechanical, thermal, chemical and humidity stabilities of contact interface. Also we found the sensing signal from the metal-SWCNT interface passivated sensor was more stable than that of unpassivated one, when they were exposed to toxic gases. The metal-SWCNT interface characteristics depending on mechanical stress, temperature, humidity and some specific chemicals were extensively investigated.