Gas fingerprinting using carbon nanotubes transistor arrays

Abstract

This paper deals with the fabrication of carbon nanotube field effect transistors (CNTFETs) for gas sensing applications. Such devices exploit the extremely sensitive change of the Schottky barrier heights between carbon nanotubes (CNTs) and drain/source metal electrodes: the gas adsorption creates an interfacial dipole that modifies the metal work function and so the band bending and the height of the Schottky barrier at the contacts. Our aim is to achieve the fingerprinting of a specific gas using a CNTFET based sensor array. This fingerprinting concept is based on the fact that the change of the metal electrode work function strictly depends on the metal/gas interaction. Consequently the CNTFET transfer characteristics will change specifically as a function of this interaction. To demonstrate this new concept, we have fabricated arrays of CNTFETs with different metal contacts: Au, Pd, Ti and Pt. Using these transistors, we have shown that a particular gas, in our case DiMethylMethyl-Phosphonate (DMMP, a sarin simulant), interacts specifically with each metal: 1 ppm of DMMP (15 min of exposure) reduces the transistor ON current by about 20% for Pt contacted CNTFETs and by nearly one order of magnitude for Pd contacted CNTFETs. We believe that this new approach can be applied for highly selective sensing of various gases, using ultra-compact, room temperature and very low power devices.

Highly sensitive and selective carbon nanotube-based gas sensor arrays functionalized with different metallic nanoparticles

“…They used Pt, Pd and Au as metal electrodes where each metal creates an analyte-specific pattern and enables discriminative detection. In that context, Bondavali et al [26] discussed the working mechanism of CNT FETs that have different contact metals under the exposure of DiMethyl-Methyl-Phosphonate (DMMP). They attributed the change in the transfer characteristics to the interaction between the gas and the metal.…”

Evaluation of sorted semi-conducting carbon nanotube films for gas sensing applications

“…It was not observed in [10] because the inter-electrode distances used are larger than ours. The resistance measured when the inter-electrode distance is less than 10 μm [6] is mainly attributed to ballistic transport in metallic nanotubes [11].…”

“…This mechanism is consistent with the evolution of the resistivity upon exposure to an electron donor or acceptor gas, respectively NO 2 and NH 3 , and was confirmed by ab-initio calculations. On the other hand, Bondavalli et al interpret the response of CNT-based gas sensors by a different mechanism: a modification of the Schottky contact between the semiconducting nanotubes and the electrical contacts [6]. Using this approach, and varying the electrode metal, the authors reported a matrix of CNT-based gas sensors aiming at the analysis of complex atmospheres by recognition of different gas fingerprints.…”

Carbon nanotubes based transistors composed of single-walled carbon nanotubes mats as gas sensors: A review

“…This concept has been developed by a joint-research team of Thales and École polytechnique in France (Nanocarb Lab.) [20][21][22][23]. More precisely, they exploited the mechanism described by IBM researchers, the modulation of the metal work function operated by gas exposure, to get the fingerprinting of a particular gas using a large network of CNTFETs.…”