Finite-size effects in armchair (n,n) carbon nanotubes are studied as a function of the tube length by using the generalized tight-binding calculations. End structures of the tubes considered here are caps formed from hemispherical pieces of Ih fullerenes and hydrogen-free open ends. It has been clarified that the dimensionality in electronic structures of the finite-length nanotubes only depends on an aspect ratio of the tube diameter to the length of the cylindrical region. The aspect ratio where the finite-length tubes exhibit one-dimensional properties is found to be about four. The results corroborate that the nanotubes with their length of 10–100 nm experimentally observed could be regarded as one-dimensional electron systems.
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