Modeling of Cu-linked rectification devices by varying torsion angles

Abstract

Using the nonequilibrium Green's function (NEGF) method in combination with the density functional theory (DFT), we have analyzed the rectifying performance in Cu-linked molecular devices by varying torsion angles (?=0?---90?). The linking effect of Cu atom has been investigated by calculating current-voltage (I-V) characteristics, rectification performance, transmission functions, projected density of states (PDOS), and molecular projected self-consistent Hamiltonian (MPSH). Present calculations revealed that linking of Cu in combination with conjugated dithiocarboxylate (-CS2) and standard thiol linkers significantly affects the metal-molecule coupling asymmetry, and thus the rectifying behavior in molecular devices. Further, the subsequent studies show that the left-right combination of -CS2 linker and Cu atom displays higher rectification ratio at various torsion angles in gold---biphenyl---gold junctions than thiol and Cu linkers. The calculated results are helpful not only in predicting an optimal combination of linking groups for realistic applications but also provide the way for better control of rectification effects in molecular devices.