Abstract
The charge carrier transport in carbon nanotubes is highly sensitive to certain molecules attached to their surface. This property has generated interest for their application in sensing gases, chemicals and biomolecules. With over a decade of research, a clearer picture of the interactions between the carbon nanotube and its surroundings has been achieved. In this review, we intend to summarize the current knowledge on this topic, focusing not only on the effect of adsorbates but also the effect of dielectric charge traps on the electrical transport in single-walled carbon nanotube transistors that are to be used in sensing applications. Recently, contact-passivated, open-channel individual single-walled carbon nanotube field-effect transistors have been shown to be operational at room temperature with ultra-low power consumption. Sensor recovery within minutes through UV illumination or self-heating has been shown. Improvements in fabrication processes aimed at reducing the impact of charge traps have reduced the hysteresis, drift and low-frequency noise in carbon nanotube transistors. While open challenges such as large-scale fabrication, selectivity tuning and noise reduction still remain, these results demonstrate considerable progress in transforming the promise of carbon nanotube properties into functional ultra-low power, highly sensitive gas sensors.
Highlights
New materials often generate entirely new possibilities, pushing the limits of the accepted boundaries of material properties within which engineers operate
Collins et al [8] showed that carbon nanotube mats contacted by metal showed oxygen sensitivity, while Kong et al [7] showed the sensitivity of individual carbon nanotube field-effect transistors (CNFETs) to NO2 and NH3, and discussed the possible mechanisms behind the device response
Individual, single-walled CNFETs have long been used as model systems to study interactions between specific analytes and the nanotube, but several advances in fabrication processes as well as understanding of their behavior has enabled the prospect of using individual-tube devices directly in applications
Summary
New materials often generate entirely new possibilities, pushing the limits of the accepted boundaries of material properties within which engineers operate. Carbon nanotube transistors often operate as Schottky-barrier fieldeffect transistors because the back-gated architecture that is typically employed for CNFET gas sensors covers the entire channel and overlaps the source and drain contacts.
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