Structural models of Au (111)-2T-Au (111) molecular junctions with one-dimensional (1D) and three-dimensional (3D) gold lead, respectively. Two repeated units are shown for each device. (a) 1D gold leads are used with large enough vacuum layer in transverse x and y directions. Molecule A is symmetrically bonded to the Au with thiol end groups. Molecule B is thiol-bonded to the right lead while the other end is terminated by a H atom. (b) 3D gold leads sandwich the 2T molecule A. The 3D leads extend periodically in x, y directions with a unit cell Au (3 × 3).
(a) Current–voltage characteristics of systems A and B with 1D gold electrodes. (b) Current–voltage characteristics of system A with 3D gold electrodes (a voltage region from −2.6 V to +2.6 V for a comparison with other studies). (c) and (d) The transmission coefficient T(E) at zero bias and density of states (DOS) of the system A with 1D electrodes. (e) and (f) T(E) at zero bias and DOS of the system A with 3D electrodes. The average Fermi level is set to zero.
MPSH states of molecule system A with 1D electrodes.
(a) I–V curves of 2T, 4T, and 6T molecular devices with the 1D Au electrodes for the system A and (b) I–V curves of 2T, 4T, and 6T for system B. The inset is the rectification ratio R(V) with the applied bias.
(a) The transmission coefficient at zero bias for 2T, 4T, and 6T devices, respectively. The average Fermi level is set to zero. The triangle denotes three molecular orbitals HOMO-1, HOMO, and LUMO toward the high energy region. (b) The transmission coefficient (solid line) of 2T device for several special bias voltages. The region between two dashed lines is the bias window.
The transmission coefficient (left) and the corresponding MPSH states of the molecular orbital HOMO (right) for 6T device at several special bias voltages. The region between two dashed lines is the bias window. The average Fermi level is set to zero. The triangle denotes the molecular projected Hamiltonian energy spectrum of the molecular orbitals HOMO-2, HOMO-1, HOMO, and LUMO toward the high energy direction.
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