Electronic Transport in Molecular Junction Based on C₂₀ Cages

Choosing closed-ended armchair (5, 5) single-wall carbon nanotubes (CCNTs) as electrodes, we investigate the electron transport properties across an all-carbon molecular junction consisting of C₂₀ molecules suspended between two semi-infinite carbon nanotubes. It is shown that the conductances are quite sensitive to the number of C₂₀ molecules between electrodes for both configuration CF1 and double-bonded models: the conductances of C₂₀ dimers are markedly smaller than those of monomers. The physics is that incident electrons easily pass the C₂₀ molecules and are predominantly
scattered at the C₂₀--C₂₀ junctions. Moreover, we study the doping effect of such molecular junction by doping nitrogen atoms substitutionally. The bonding property of the molecular junction with configuration CF1 has been analysed by calculating the Mulliken atomic charges. Our results have revealed that the C atoms in N-doped junctions are more ionic than those in pure-carbon ones, leading to the fact that N-doped junctions have relatively large conductance.