Gas Detection Mechanism of Single Walled Carbon Nanotube Networks

Paola Barbara, Georgetown University, DMR 1008242

Carbon nanotube (CNT) gas sensors are highly sensitive, low power nanoscale sensors. It is still under debate whether the main sensing mechanism is due to physical adsorption of gas molecules onto the nanotube surface or changes in the Schottky barrier at the interfaces between the nanotube and the metal contacts.

We tested the response of CNT networks to NO2 with the samples fully exposed to the gas (Fig. A) and after covering the contacts with a passivating polymer layer (Fig. B). The conductance of the uncovered device tracks quite well the change in

NO2 concentration, whereas the response is slower when the contacts are covered.

Contrary to single-nanotube gas sensors, where the response is mainly due to the contacts [1], the response for CNT networks is due to both gas adsorption on the network and changes at the contacts.

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[1] J. Zhang et al. , Appl. Phys. Lett. 88, 123112 (2006).

Fedorov’s samples fabricated at GU

Gas Detection Mechanism of Single walled Carbon Nanotube Networks

Paola Barbara, Georgetown University, DMR 1008242

Visit to Kurchatov Institute, Moscow, Russia: P. Barbara and grad. student, A. Boyd, visited the Russian lab in Aug. 2011 for planning the work and testing Boyd’s first samples.

Visit to Georgetown University (GU), Washington, USA: Our Russian collaborator, G. Fedorov, visited GU in Dec. 2011 to fabricate samples with electrodes made of different metals and study how they affect sensing properties. Analysis of these results is ongoing.

GU undergraduate student: B. Rost, worked with A. Boyd to learn fabrication techniques for nanotube devices under the GU sponsored GUROP program.

Purchase of new equipment: A custom designed Kelvin Probe system is being built for this project.

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A. Boyd in Moscow

Boyd’s samples tested in Russian lab

Cr/Au