Bandgap modulation of carbon nanotubes by encapsulated metallofullerenes


Motivated by the technical and economic difficulties in further miniaturizing silicon-based transistors with the present fabrication technologies, there is a strong effort to develop alternative electronic devices, based, for example, on single molecules1,2. Recently, carbon nanotubes have been successfully used for nanometre-sized devices such as diodes3,4, transistors5,6, and random access memory cells7. Such nanotube devices are usually very long compared to silicon-based transistors. Here we report a method for dividing a semiconductor nanotube into multiple quantum dots with lengths of about 10 nm by inserting Gd@C82 endohedral fullerenes. The spatial modulation of the nanotube electronic bandgap is observed with a low-temperature scanning tunnelling microscope. We find that a bandgap of 0.5 eV is narrowed down to 0.1 eV at sites where endohedral metallofullerenes are inserted. This change in bandgap can be explained by local elastic strain and charge transfer at metallofullerene sites. This technique for fabricating an array of quantum dots could be used for nano-electronics8 and nano-optoelectronics9.

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Figure 1: Effect of inserted Gd metallofullerenes (GdMFs) on the topography and band structure of a single-walled nanotube (SWNT).
Figure 2: Bandgap modulation of a GdMF-SWNT by encapsulated GdMFs.
Figure 3: Energy-resolved dI/dV images of a GdMF-SWNT.


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We thank J.-Y. Park for his LTSTM design, Y. J. Song and H. S. Suh for experimental assistance, and J. J. Yu and S. W. Hwang for discussions. This work was supported by the Korean Ministry of Science and Technology through Creative Research Initiatives Program and the Future Program on New Carbon Nano-Materials by the Japan Society for the Promotion of Science.

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Correspondence to Young Kuk.

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Lee, J., Kim, H., Kahng, S. et al. Bandgap modulation of carbon nanotubes by encapsulated metallofullerenes. Nature 415, 1005–1008 (2002).

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