INTEREST in nano-materials has been growing rapidly for the past several years. Carbon nanotubes (CNTs) are especially promising as new materials for a variety of potential applications. Existing electrical sensor materials include semi conducting metal oxides, silicon devices, and carbon black-polymer composites. Semi conducting metal oxides have been widely used for NO and NH detection. These sensors operate at high temperatures (200 C to 600 C) to achie
ve enhanced chemical reactivity between molecules and the sensor materials for substantial sensitivity. Conducting polymers and organic phthalocyanine semiconductors have also been investigated for NO sensing. The former exhibits limited sensitivity, whereas the latter tends to have very high resistivity (sample resistance of -Ohms). Recently, CNT-based gas sensors have received considerable attraction because of their outstanding properties, such as faster response, higher sensitivity, lower operating temperature, and a wide variety of gases that may be detected compared with the other types of gas sensor. Up-to-date reported studies on possible applications of carbon nanotubes as gas sensors have been focused either on isolated single wall carbon nanotubes (SWCNTs) or on SWCNT mats. Theoretical studies have predicted significant changes in the electronic properties of carbon nanotubes because of gas adsorption. These results lead to the application of carbon nanotubes as gas sensors to detect sub-ppm concentrations of oxidizing gases like NO , and CO. However, it takes a long time for the CNT-based gas sensors fabricated to recover owing to the small diffusion barriers of gases on CNT surfaces. This letter reports on the fabrication of the sensor composed of a heater, a diaphragm, a contact electrode, and a directly grown MWCNT-sensing film on a thermally insulated dielectric diaphragm to improve recovery characteristics. Following a description of the integrated structure and the MWCNT deposition process, the characteristics of the sensor when exposed to NO are presented.
ve enhanced chemical reactivity between molecules and the sensor materials for substantial sensitivity. Conducting polymers and organic phthalocyanine semiconductors have also been investigated for NO sensing. The former exhibits limited sensitivity, whereas the latter tends to have very high resistivity (sample resistance of -Ohms). Recently, CNT-based gas sensors have received considerable attraction because of their outstanding properties, such as faster response, higher sensitivity, lower operating temperature, and a wide variety of gases that may be detected compared with the other types of gas sensor. Up-to-date reported studies on possible applications of carbon nanotubes as gas sensors have been focused either on isolated single wall carbon nanotubes (SWCNTs) or on SWCNT mats. Theoretical studies have predicted significant changes in the electronic properties of carbon nanotubes because of gas adsorption. These results lead to the application of carbon nanotubes as gas sensors to detect sub-ppm concentrations of oxidizing gases like NO , and CO. However, it takes a long time for the CNT-based gas sensors fabricated to recover owing to the small diffusion barriers of gases on CNT surfaces. This letter reports on the fabrication of the sensor composed of a heater, a diaphragm, a contact electrode, and a directly grown MWCNT-sensing film on a thermally insulated dielectric diaphragm to improve recovery characteristics. Following a description of the integrated structure and the MWCNT deposition process, the characteristics of the sensor when exposed to NO are presented.
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