Abstract Submitted to the    CCTN09 Symposium:

Defective carbon nanotubes: magnetism, spin transport and gas sensing applications

Zeila Zanolli, Jean-Christophe Charlier

Catholic University of Louvain

zeila.zanolli@uclouvain.be

XIV. Transport in Nanotubes

Carbon nanotubes (CNTs) are renowed in the scientific community for being both a playground for studying fundamental physical properties and for applications in, to mention a few, electronic, spintronic and gas sensing technologies. However, despite the progresses in growth techniques, CNTs always exhibit structural defects [1] and their electronic and transport properties will be affected accordingly [2]. In addition, the presence of defects in carbon-based nanostructures has been seen as source of magnetism [3]. Hence, mastering the physics underlying defected CNTs is crucial not only to model realistic systems but also to design new devices.

The spin-polarized electron transport properties of carbon nanotubes with vacancies are investigated using first principles and non-equilibrium Green’s function techniques [4]. Carbon atoms with unsaturated bonds are found to behave as quasi-localized magnetic impurities, coupled by long range interactions. The magnetism of carbon nanotubes with reconstructed mono- and tri-vacancies results in spin dependent contuctances and, hence, can be exploited in spintronic devices such as nano-spin valves.

Clarified the properties of CNTs with vacancies, the sensing ability of defected CNTs towards several molecules (NO₂, NH₃, CO, CO₂, H₂O) has also been investigated ab initio. Since the adsorption/desorption of molecules induces modulations on the electrical conductivity of the tube, quantum conductances of the CNT-based sensors are predicted, finding that defective nanotubes are sensitive to NO₂, NH₃, CO, and H₂O while molecular selectivity is provided by the nature of the charge transfer.

This work is supported by the project “Nano2Hybrids” (EC-STREP-033311).

[1] A. Hashimoto et al., Nature 430, 870 (2004); Y. Fan et al., Nat. Mater. 4, 906 (2005); K. Suenaga et al., Nature Nanotech. 2, 358 (2007).
[2] C. Gomez-Navarro et al., Nature Mater. 4, 534 (2005).
[3] P. Esquinazi et al., Phys. Rev. Lett. 91, 227201 (2003); S. Talapatra et al., Phys. Rev. Lett. 95, 097201 (2005); Y. Shibayama et al., Phys. Rev. Lett. 84, 1744 (2000).
[4] Z. Zanolli and J.-C. Charlier, in preparation (2009).
[5] Z. Zanolli and J.-C. Charlier, submitted (2009).

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