First-Principles Study on Formation and Electron-Transport Properties of Single Oligothiophene Molecular Junctions

In this work, the formation of single oligothiophene molecular junctions was studied using density functional theory. The elastic scattering Green’s function method was applied to investigate the electron-transport properties of the molecular junctions and their conductance switching properties caused by an electrochemical gate. Given four configurations, the optimized structures and breakdown forces of the molecular junctions were obtained. The breakdown of the oligothiophene molecular junctions is likely to occur at the Au–S bond as the electrodes are pulled. The simulated results show that the experimental findings that the four-repeating-unit oligothiophene is more conductive than the three-repeating-unit oligothiophene are due to their different configurations. The oligothiophenes’ electronic structures are sensitive to the gate field, and their conductance switching properties are explained when a gate field is applied.