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Carbon Nanotube Transistors as Gas Sensors: Response Differentiation Using Polymer Gate Dielectrics

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journal contribution
posted on 21.11.2019, 13:36 by François Lapointe, Jianfu Ding, Jacques Lefebvre
The high sensitivity of carbon nanotube devices as gas sensors is generally attributed to the large surface area of the material, whereas selectivity is often imparted by the “lock-and-key” mechanism. In contrast with this picture, where little function is conferred to the underlying substrate, we demonstrate that bottom gate carbon nanotube network field-effect transistors (CNN-FETs) fabricated on a variety of polymer dielectrics, but with the same pristine carbon nanotubes, show differentiated responses to analytes. Interaction with the environment thus occurs not only directly with carbon nanotubes but is often mediated by the substrate. In a broad survey of polymers, we identify several materials suitable as the gate dielectric of printed devices and that yield a vanishing gate hysteresis in ambient air. The other two classes of polymers that induce a lagging or advancing hysteresis in CNN-FETs are found desirable for gas sensing applications. Moreover, we have tested CNN-FETs with different polymer gate dielectrics against a series of analytes ranging from common alcohols to organic solvents and amines, among others. A rich set of distinct and complementary analyte signatures could be observed, identifying the polymer gate dielectric as a differentiator for chemical discrimination in a future printed cross-reactive sensor array, that is, an electronic nose.