Using the Landauer formalism that combines both the non-equilibrium Green's function (NEGF) and first-principles density functional theory (DFT), the electron transport characteristics of one-dimensional molecular switching device based on the capped carbon nanotubes have been investigated. The results show that the transmission can be efficiently tuned within two orders of magnitude just by changing 0.2 nm of the tube-tube separation. Moreover, the electron transport is insensitive to the topology of the facing conformations which can improve the practical stability of the chosen system as a molecular switch.
By applying nonequilibrium Green's function formalism combined with the first-principles density functional theory, we investigate the electronic transport in two molecular junctions constituted by a substituted oligo (phenylene ehtynylene) sand-wiched between two Au electrodes. Our calculations show that the weak molecule-electrode coupling is responsible for the observation of the negative differential resistance (NDR) effect in experiments. When the coupling is weak, the projected density of states (PDOS) of the molecule and the electrodes undergoes a mismatch-match-mismatch procedure, which increases and then decreases the transmission peak intensities, leading to a NDR effect. We also find that the localization/delocalization of the molecular orbitals and the change of charge state of the molecule have no direct relation with the NDR effect, because they change little as the voltage increases.
By applying non-equilibrium Green's function in combination with density functional theory,we investigated the electronic transport properties of capped-carbon-nanotube-based molecular junctions with multiple N and B dopants.The results show that the electronic transport properties are strongly dependent on the numbers and positions of N and B dopants.Best rectifying behavior is observed in the case with one N and one B dopants,and it is deteriorated strongly with the increasing dopants.The rectifying direction is even reversed with the change of doping positions.Moreover,obvious negative differential resistance behavior at very low bias is observed in some doping cases.
Using the Landauer formalism that combines both the non-equilibrium Green’s function and first-principles density functional theory, the electron transport properties of a one-dimensional molecular junction based on capped carbon nanotubes with boron doping at various sites are investigated. The results show that the electron transport properties are strongly dependent on the boron-doping site. Negative differential resistance behavior can be observed when boron-atom dopants are present in the tip region.
We investigate using the Landauer formalism,which combines both the non-equilibrium Green's function and density functional theory,the effects of separation and orientation between two electrodes of boron-doped capped-carbon-nanotube-based molecular junctions on negative differential resistance.The results show that this negative differential resistance behavior is strongly dependent on the separation and orientation between the two electrodes.A gap width of 0.35 nm and maximal symmetry achieves the best negative differential resistance behavior.
