Miniaturized gas-sensing devices that use single-walled carbon nanotubes as active material have been fabricated using two\r\ndifferent electrode materials, namely, Au/Cr and NbN. The resistive sensors have been assembled aligning by dielectrophoresis the\r\nnanotube bundles between 40 Ã?µm spaced Au/Cr or NbN multifinger electrodes. The sensing devices have been tested for detection\r\nof the H2S gas, in the concentration range 10ââ?¬â??100 ppm, using N2 as carrier gas. No resistance changes were detected using sensor\r\nfabricated with NbN electrodes, whereas the response of the sensor fabricated with Au/Cr electrodes was characterized by an\r\nincrease of the resistance upon gas exposure. The main performances of this sensor are a detection limit for H2S of 10 ppm and a\r\nrecovery time of few minutes. The present study suggests that the mechanism involved in H2S gas detection is not a direct charge\r\ntransfer between molecules and nanotubes. The hypothesis is that detection occurs through passivation of the Au surfaces by H2S\r\nmolecules and modification of the contact resistance at the Au/nanotube interface.
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