Current rectification in a single molecule diode: the role of electrode coupling

TL;DR

This study demonstrates exceptionally high rectification ratios in single-molecule junctions using a metal-oxide cluster, revealing that asymmetric electrode coupling is key to diode behavior and enabling rational design of molecular diodes.

Contribution

It shows that asymmetric electrode coupling in single-molecule junctions causes high rectification, providing a simple design strategy for molecular diodes.

Findings

Rectification ratios > 100 achieved in single-molecule junctions

Junctions sustain current densities > 10^5 A/cm^2

Rectification due to asymmetric coupling and level structure

Abstract

We demonstrate large rectification ratios (> 100) in single-molecule junctions based on a metal-oxide cluster (polyoxometalate), using a scanning tunneling microscope (STM) both at ambient conditions and at low temperature. These rectification ratios are the largest ever observed in a single-molecule junction, and in addition these junctions sustain current densities larger than 10^5 A/cm^2. By following the variation of the I-V characteristics with tip-molecule separation we demonstrate unambiguously that rectification is due to asymmetric coupling to the electrodes of a molecule with an asymmetric level structure. This mechanism can be implemented in other type of molecular junctions using both organic and inorganic molecules and provides a simple strategy for the rational design of molecular diodes.