Effect of plasma modification of single wall carbon nanotubes on ethanol vapor sensing

The oxygen and fluorine modified single wall carbon nanotubes (SWCNTs) were manufactured by microwave plasma enhanced chemical vapor deposition (MPECVD), and were developed as novel gas sensor materials. The sensor characteristic has shown a p-type response with resistance enhancement upon exposure to 100 ppm ethanol at room temperature. Oxygen plasma modification can increase the sensor response from 1.13 to 1.74 on process duration of 30 s due to the apparent elimination of amorphous carbon, as demonstrated by FESEM and Raman results. However, oxygen plasma modification has no effective assistance in decreasing the response and recovery time. By applying fluorine plasma modification, the sensor response only increases from 1.13 to 1.51 on process duration of 60 s, but the response and recovery time can decrease apparently from 178 to 54 s and 364 to 97 s due to the existence of numerous fluorine-included functional groups, as demonstrated by XPS and AES results. Therefore, the plasma modified SWCNT can elevate the sensitivity and reactivity for room temperature ethanol sensing.