Modeling the electrostatic potential spatial profile of molecular junctions: The influence of defects and weak links

The spatial profile of the electrostatic potential across a molecular junction is one of the single most influential factors in determining the form of intensity-voltage characteristics. We have modeled the influence of bridge electronic defects (site substitutions) and weak links (local weak bonds) on the potential profile. The potential is determined self-consistently by solving Poisson and Schrödinger equations simultaneously. We have considered the simplest model of a one-dimensional molecular wire. This system already exhibits some of the most relevant features observed in I-V curves of real chemically modified junctions, where strong asymmetries and rectification effects have been reported.