Contact Transparency of Nanotube-Molecule-Nanotube Junctions

The transparency of contacts between conjugated molecules and metallic single-walled carbon nanotubes is investigated using a single-particle Green's function method which combines a Landauer approach with \textit{ab initio }density functional theory. We find that the overall conjugation required for good contact transparency is broken by connecting through a six-member ring on the tube. Full conjugation achieved by an all-carbon contact through a five-member ring leads to near perfect contact transparency for different conjugated molecular bridges. [Phys. Rev. Lett. \textbf{99, }146802 (2007)]