Controlling the electronic transport through the carbon nanotube junction via the local electronic environment

The electron transport behaviors through a series of molecular junctions, which consist of polyacene molecule bridging armchair CNT(5,5) electrodes, have been investigated using density functional theory combined with the non-equilibrium Green's function approach. The electronic signature is strongly impeded by the edge sites at nonvertical edges of CNT(5,5), such as the SWNT-4CH junction. This is due to the fact that the presence of edge electron injection can significantly hinder mainstream electron transport through destructive quantum interference, thereby reducing the current substantially. In contrast, when the edge sites at interfaces between molecules and electrodes are removed, edge electron injection is blocked, and an observable improvement in junction current is achieved. Substituting carbon atoms at the edge sites with B and N heteroatoms results in a nonlinear behavior for SWNT-4BH and SWNT-4NH with an "inverse Schottky" feature. This confirms that introducing B and N heteroatoms at edge sites can affect part of edge electron injection, reduce destructive quantum interference effects, and enhance junction conductivity. Based on these studies, a series of models were designed to investigate rectification characteristics. The insights gained from this study on interfaces could contribute to a better understanding of all-carbon devices for designing efficient nanoelectronic devices.