Gas sensing with long, diffusively contacted single-walled carbon nanotubes

Abstract

A carbon nanotube thermal-conductivity-based pressure or gas sensor is described, which utilizes5–10 µm long, diffusively contacted single-walled nanotubes (SWNTs). Low temperatureelectrical transport measurements for these tubes were suggestive of a thermallyactivated hopping mechanism for electron localization, where a hopping energy of∼39 meV was computed. A negative differential conductance regime was also detected insuspended tubes, released using critical point drying, at high bias voltages. The pressure orgas sensitivity increased more dramatically as the bias power was increased up to14 µW, which was interpreted in the context of the high optical phonon density in the suspendedSWNTs. Such devices are promising for use as pressure sensors, as well as for the chemicalidentification of species having differing gas thermal conductivities.