Gas Sensing Properties and Transport Properties of Multi Walled Carbon Nanotubes

OF THESIS GAS SENSING PROPERTIES AND TRANSPORT PROPERTIES OF MULTI WALLED CARBON NANOTUBES Multi walled carbon nanotubes (MWCNT) grown in highly ordered porous alumina templates were incorporated into a resistive gas sensor design and were evaluated for their sensitivities. The material characteristics and electrical properties of the nanotubes were analyzed. A study was undertaken to elucidate the effect of UV light on desorption characteristics and the dependence of sensitivity on (i) thickness of amorphous carbon layers and (ii) flow rates of analyte gases. These sensors were highly responsive to both oxidizing and reducing gases with steady state sensitivities of 5% and 10% for 100ppm of NH3 and NO2 respectively, at room temperature. As part of a comparative study, thick films of MWCNTs grown on Si/SiO2 substrates were integrated into various nano-composite based sensors and were evaluated for their response. Steady state sensitivities as high as 10% and 11% were achieved for 100ppm of NH3 and NO2 respectively, at room temperature. MWCNTs were characterized for their electrical properties by I–V measurements at room temperatures. A typical I-V curve with an ohmic behavior was observed for a device with high work function metals (example: Au, Pt); Schottky behavior was observed for devices with metal contacts having low work functions (example: Al, Cu).