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A method to calculate the transmission coefficient in multiterminal systems is presented. By adding a complex absorbing potential to the Hamiltonian of the semi-infinite leads, the problem of inverting an infinite dimensional matrix is transformed into a finite dimensional eigenvalue problem. Using this approach transmission coefficients are calculated for all energies at once. The accuracy of the approach is demonstrated with an analytically solvable model system. Numerical examples of a four-terminal graphene cross junction and six-terminal carbon nanotube junction are presented. [ABSTRACT FROM AUTHOR]

The properties of carbon nanotube-graphene junctions are investigated with first-principles electronic structure and electron transport calculations. Contact properties are found to be key factors in determining the performance of nanotube based electronic devices. In a typical single-walled carbon nanotube-metal junction, there is a p-type Schottky barrier of up to ∼0.4 eV which depends on the nanotube diameter. Calculations of the Schottky barrier height in carbon nanotube-graphene contacts indicate that low barriers of 0.09 eV and 0.04 eV are present in nanotube-graphene contacts ((8,0) and (10,0) nanotubes, respectively). Junctions with a finite contact region are investigated with simulations of the current-voltage characteristics. The results suggest the suitability of the junctions for applications and provide insight to explain recent experimental findings. [ABSTRACT FROM AUTHOR]