The physical properties of a carbon nanotube is sensitive to its atomic structure. A novel example is that depending on the diameter and the helicity of it, a carbon nanotube can behave either like a metal or like a semiconductor. For example, using the chiral indices [u,v], when u-v is divisible by integer 3, it is metallic, otherwise it is semiconducting.
We have developed a systematic approach to decipher the chiral indices (from which the diameter and helicity of a carbon nanotube are also defined) using nanobeam electron diffraction. The method has been applied to measure the chiral indices unambiguously of both the single-walled and multiwalled carbon nanotubes.
L.-C.
Qin, T. Ichihashi and S. Iijima: On the measurement of helicity of carbon
nanotubes, Ultramicroscopy 67,
181 (1997).
L.-C.
Qin, S. Iijima, H. Kitaura, Y. Maniwa, S. Suzuki and Y. Achiba: Helicity and
packing of single-walled carbon nanotubes studied by electron
nanodiffraction, Chemical Physics
Letters 268, 101 (1997).
L.-C.
Qin: Measuring the true helicity of carbon nanotubes, Chemical
Physics Letters 297, 23
(1998).
L.-C.
Qin: Helical diffraction from tubular structures, Materials
Characterization 44, 407
(2000). (PDF)
L.-C.
Qin: Determining the Helicity of Carbon Nanotubes by Electron Diffraction;
in Progress in Transmission Electron Microscopy 2, Applications in
Materials Science, Springer Series in Surface Sciences Vol. 39,
Eds. X.F. Zhang and Z. Zhang, (Springer-Verlag / TUP, 2001).
Z. Liu and L.-C. Qin: A practical approach to determine the handedness of chiral carbon nanotubes by electron diffraction. Chemical Physics Letters 405, 265 (2005).
Z. Liu and L.-C. Qin: A direct method to determine the chiral indices of carbon nanotubes. Chemical Physics Letters 408, 75 (2005).
Z. Liu, Q. Zhang, and L.-C. Qin: Determination and mapping of diameter and helicity for single-walled carbon nanotubes. Physical Review B 71, 245413 (2005).
Z. Liu, Q. Zhang, and L.-C. Qin: Accurate determination of atomic structure of multiwalled carbon nanotubes by nanobeam electron diffraction. Applied Physics Letters 86, 191903 (2005).