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Nanotube Single-Electron Transistor Works At Room Temperature
A nanoscale transistor that can be switched between "on" and "off" with a single electron and works efficiently at room temperature could become an important component in molecular electronics. Now, researchers in the Netherlands have made such a room-temperature single-electron transistor (SET) within a single carbon nanotube [Science, 293, 76 (2001)].
To make the device, professor Cees Dekker and coworkers in the department of applied physics at Delft University of Technology start with a metallic single-wall carbon nanotube lying across two gold electrodes on an insulating surface (right). Using the tip of an atomic force microscope, they bend the nanotube sharply at two sites along its length. The bending causes the tube to buckle, with the two buckles separated by 20 nm, as shown in the circle at right and in the enlarged image at left. The buckles serve as barriers on either side of a "conducting island" into which electrons can tunnel one at a time when an appropriate voltage is applied to the "gate" underneath the island.
It can take several hours to make just one of these buckled nanotubes, Dekker says. For large-scale applications, SETs will have to be fabricated more efficiently. Dekker and coworkers suggest that it might be possible to induce buckles in many nanotubes at once by using a patterned substrate or by chemically creating defects in the side wall of the nanotube.
While studying how the nanotube SET works, the Delft team uncovered some exotic physics. They found evidence of a type of quantum connection between the electrons: Rather than hopping on and off the island independently, as has been seen previously, the electrons in this new device do their hopping in an intimately coupled way.
|PHOTOS COURTESY OF CEES DEKKER AND HENK POSTMA/DELFT UNIVERSITY OF TECHNOLOGY
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Copyright © 2001 American Chemical Society