Metallic conduction at organic charge-transfer interfaces

TL;DR

This paper demonstrates that highly conducting, metallic interfaces can be created between organic molecular crystals through charge transfer, revealing a new class of electronic systems with potential applications in organic electronics.

Contribution

It introduces a novel method to achieve metallic conduction at organic interfaces via charge transfer, expanding the scope of interface engineering in organic materials.

Findings

Conductivity ranges from 1 to 30 kOhm per square.

Some interfaces exhibit metallic temperature dependence.

Charge transfer occurs on a molecular scale at the interface.

Abstract

The electronic properties of interfaces between two different solids can differ strikingly from those of the constituent materials. For instance, metallic conductivity, and even superconductivity, have been recently discovered at interfaces formed by insulating transition metal oxides. Here we investigate interfaces between crystals of conjugated organic molecules, which are large gap undoped semiconductors, i.e. essentially insulators. We find that highly conducting interfaces can be realized with resistivity ranging from 1 to 30 kOhm square, and that, for the best samples, the temperature dependence of the conductivity is metallic. The observed electrical conduction originates from a large transfer of charge between the two crystals that takes place at the interface, on a molecular scale. As the interface assembly process is simple and can be applied to crystals of virtually any conjugated molecule, the conducting interfaces described here represent the first examples of a new class of electronic systems.