(Courtesy D. Hornbaker and A. Yazdani)

The illustration depicts the atomic structure of a single-wall carbon nanotube "peapod"
with superimposed electron waves, mapped using a state-of-the-art
low-temperature scanning tunneling microscope at the University of Illinois.

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In a paper appearing today [1 February 2002] in Science, Professor Ali Yazdani and his student, Daniel Hornbaker, report their experiments on nanoscale "peapods"—C₆₀ buckyballs nested inside single-wall carbon nanotubes. Using their high-resolution, low-temperature scanning tunneling microscope (STM), they performed the first electronic measurements of these novel nanomaterials and mapped the motion of electrons inside them. Their measurements show that an ordered array of the encapsulated molecules could be used to tailor electron motion in nanotubes—an important finding for fabricating nanotube-based single-molecule electronic devices.

The peapods, which are produced using molecular self-assembly by University of Pennsylvania materials science professor David Luzzi and his group, show that encapsulated fullerenes modify the electronic properties of the nanotube without affecting its atomic structure. Penn professor of physics Eugene Mele, in collaboration with the Illinois group, created a theoretical model of the experimental findings.

Yazdani and his group also used their home-built STM to manipulate the fullerene molecules inside a carbon nanotube, allowing them to record the electronic properties of sections of nanotubes with and without the encapsulated molecules. By comparing the two experiments' results, they were able to determine that, in contrast to unfilled nanotubes, peapods exhibit additional electronic features that are strongly dependent on their physical location along the tube. Their findings anticipate future design of hybrid nanotube structuress having specific electronic functionalities.

More information about this exciting work is available from Professor Yazdani (Department of Physics and the Frederick Seitz Materials Research Laboratory) or Physics graduate student Daniel Hornbaker.

D. J. Hornbacker, S-J Kagng, S. Misra, B. W. Simth, A. T. Johnson, E. J. Mele, D. E. Luzzi, and A. Yazdani, "Mapping the One-Dimensional Electronic States of Nanotube Peapod Structures," Science 295, 828–831, 2002. (Cover Story)