Electronic structure, screening, and charging effects at a metal/organic tunneling junction: A first-principles study

By ab initio simulation in the density-functional-local-density approximation, we study the structural and electronic properties of a monolayer of Pd-porphyrin and perylene on a Au(lll) slab, and we investigate the response of this interface to an external electrostatic field. Our computation closely mimics the metal/organic junction investigated experimentally by Fischer et al. [Europhys. Lett. 28, 129 (1994)] that has been shown to display rectifying behavior and charging effects associated with molecular conduction via single-electron tunneling. The ab initio model allows us to determine the conditions for molecular tunneling and to investigate their dependence on structural and chemical parameters. Moreover, it provides a direct view of screening at the molecular level.