Electronic fluctuations in nanotube circuits and their sensitivity to gases and liquids

The temperature-dependent noise of individual, single-walled carbon nanotubes is measured here in a variety of different gases and liquids. The ambient environment is found to have only a weak relationship with device noise, even in cases where adsorption significantly changes the dc resistance. Correspondingly, a 450 K degassing procedure typically reduces the device noise by only 1 order of magnitude. An important exception to this finding is a pronounced, 100-fold increase in noise observed near gas-liquid phase transitions of the ambient. Wide-range temperature scans clearly identify the condensation of N(2), H(2), and CH(4) onto metallic nanotubes, but not the sublimation of CO(2). The observations suggest that nanotube devices can directly transduce ambient density fluctuations, though without an inherent gas specificity. Even so, the method is a particularly sensitive characterization of nanotube chemical interactions, one which is successful even for the extreme case of inert gases adsorbed on metallic nanotubes.