Probing quantum confinement of single-walled carbon nanotubes by resonant soft-x-ray emission spectroscopy

We report the band-structure changes near Fermi level for single-walled carbon nanotubes (SWNTs) with diameters down to 1nm from the study of soft-x-ray absorption and resonant emission spectroscopy. The observed quantum confinement of SWNTs affects both π and σ bands and bandgap through the rehybridization of π and σ orbitals. The significant changes of electronic structure are proved to be a measure for the mean diameter of the macroscopic amounts of SWNTs.