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Electromigrated ultra-small quantum dots based on carbon nanotube

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Single molecule devices suffer of the difficulty to be able to put a single molecule between two nanometer-spaced electrodes.
Single wall carbone nanotube (SWCNT) are giant molecules which have micrometric dimension in the axial direction and nanometric dimension in the radial one. From this point of view, nanotubes are much more easly manipulables to study transport at nanometric scale.

Images par microscope électronique à balayage d'un nanogap électromigré sur un nanotube de carbone monoparoi

TELEM group is developping a project to realize carbone nanotube based quantum dots by electromigration. This will allow the possibility to investigate transport properties of a small SWCNT section. By evaporating two electrodes on a SWCNT, in fact, we define a tube portion (dot) where electrons are confined, the dot size is simply given by the distance between the electrodes. Electromigration allows to attain electrode distances lower than what is typically attainable by standard electron lithogaphy techniques.
Our device is made by a SWCNT covered by a 100 nm long, 20 nm thick Pd nanowire. Electromigration on such structure is still possible because we measure taht the SWCNT starts shunting the nanowire as the nanogap is formed.
Preliminary results show that this technique results in the formation of quantum dots in a strong coupling regime where Kondo effect plays a fondamental role. New tests where we change the metal nature of the nanowire and the electromigration procedure are in progress.
Besides that, the group is also studing the SWCNT based transistor at room temperature. Such device can overcome the silicon technology by allowing to acces to very short channel transistors.