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Accueil > Séminaires > Archive des séminaires d’Utinam > Archive des séminaires de physique (jusqu’en 2011) > 2007

Electric Field Induced Changes in Carbon Nanotubes

par Edith Burgey -

Zhao Wang

doctorant à l’Institut UTINAM équipe DSC

Jeudi 15 novembre 2007

Résumé : Carbon Nanotubes (CNTs) can be used as key elements in nanoelectromechanical systems (NEMS) such as nanorelays, nanoswitches, nanotweezers and feedback device which are designed for memory, sensing or actuation uses. Their electric field induced deformation is a key character for these promising applications, as well as for their fabrication, separation and electromanipulation.

We have computed the deformations of semiconducting and metallic CNTs induced by uniform electrostatic fields, by minimizing total potential energy calculated using a monopole-dipole-interaction model combined with an empirical many-body potential (AIREBO). The effects of field strength, field direction tube geometries and defects on the electrostatic deformation are investigated for both single- and double-walled CNTs. For metallic CNTs, they are much easier to be deflected than semiconducting ones. The deflection is not changed by reversing the field direction. The curve of alignment ratio versus field strength is found to change with field directions. The deflection is found to decrease with the increase of the tube radius ; conversely, it increases when the tube is longer. The multi-walled metallic CNTs are found to be much harder to be bent in electric fields than SWCNTs. Furthermore, we find that the electrostrictive deformation of SWCNTs is proportional to the square of field strength.

Currently, we are investigating the distribution of the charge and the induced dipole in CNTs submitted to electrostatic fields. The results of our calculation show that the charge density at the edge of the open-ended tube is higher than that of the closed tube with net charges. The same effects can be found for the distribution of induced dipoles.

These studies could apply to recently designed devices based on cantilevered carbon nanotubes. Moreover, we wish that they could help to design some new nanoelectromechanical devices.