p-n Junction at the Interface between Metallic Systems

Density functional theory is used to evaluate the electronic properties in a composite metallic material consisting of two subsystems made of interacting metallic thin films separated by a subnanometer gap. One of the subsystems, M/Pt-M/Pt, has a monolayer of metal M over a core of Pt atoms, and the other is Pt-Pt, where the interacting surfaces are made of pure Pt. At equilibrium, this composite material exhibits a potential barrier at the interface, resembling a semiconductor p-n junction. In the gap region of M/Pt-M/Pt, the amount of electrons correlates with the surface layer degree of polarization, which depends on electronegativity and number of unpaired electrons in the external shells. The electron density in the gap, the system work function, and the built-in potential at the interface of the composite system calculated for various metal skins correlate with the degree of reduction of the Pt atoms located at the junction area.