Semiconducting properties of cup-stacked carbon nanotubes

The current-voltage characteristics of individual cup-stacked carbon nanotubes (CSCNTs) were investigated in situ inside the transmission electron microscope. Different from other quasi-1D carbon structures such as multi-walled carbon nanotubes, carbon nanofibers or graphitic fibers that normally behave as a metallic conductor of electrons, individual CSCNTs were found to exhibit unexpectedly semiconducting behaviors due to the special stacking microstructure of graphene layers. The band gap of the CSCNTs was obtained with the value of about 0.44 eV, in contrast to the zero-gap semiconducting quasi-2D graphene. These findings provide new information about the effect of the stacking graphene layers on their electronic properties, and will widen the usefulness of such stacking structure for the application in nanoelectronics.