Theoretical calculation of electron transport properties of the Au-Si60-Au molecular junctions

Abstract

The ground structure of Si60 clusters, which was obtained by optimization when using the density functional theory method, is a fullerene structure with C1 point group, a diameter 1.131 nm, the average bond length 0.239 nm, and the difference between the energies of the lowest unoccupied molecular orbital and the highest occupied molecular orbital is 0.72 eV. A Si60 cluster with optimized structure is sandwiched between two semi-infinite Au(100)-44 electrodes, and the Au-Si60-Au molecular junctions is constructed, whose electron transport properties is investigated with a combination of density functional theory and non-equilibrium Green's function method. When the distance between the two electrodes is 1.74 nm, the equilibrium conductance of the junctions is 1.93 G0 (G0=2e2/h). In the range of voltage from -2.02.0 V, we have calculated the current and conductance under different voltages, and find that the Ⅰ-Ⅴ curve of the junctions show linear characteristics. We also analyze the properties of transport from transmission and frontier molecular orbitals, and discuss the relationship of transfer charge with conductance.