Large negative differential resistance and rectifying behaviors in isolated thiophene nanowire devices

We design isolated molecular nanowires composed of thiophene oligomers sandwiched between two one-dimensional gold electrodes. Electronic transport through the molecular junctions with two interface geometries is studied by performing the first principles calculations based on density functional theory and nonequilibrium Green's function. The current-voltage (I-V) curves of the molecular wires display an unexpected negative differential resistance and rectifying behaviors along with the oscillation effects, different from other theoretical and experimental studies about the analogous thiophene devices. The significant difference is attributed to the design of the one-dimensional gold electrodes with large enough vacuum layer in transverse direction in order to suppress the interaction between wires. Such transport behaviors indicate that the thiophene molecular device would be an important candidate in future molecular electronics.