Controlling single-molecule junction conductance by molecular interactions.

Y Kitaguchi,S Hatta,H Okuyama,T Frederiksen,M Paulsson,T Aruga,S Habuka,H Ueba

doi:10.1038/srep11796

Abstract

For the rational design of single-molecular electronic devices, it is essential to understand environmental effects on the electronic properties of a working molecule. Here we investigate the impact of molecular interactions on the single-molecule conductance by accurately positioning individual molecules on the electrode. To achieve reproducible and precise conductivity measurements, we utilize relatively weak π-bonding between a phenoxy molecule and a STM-tip to form and cleave one contact to the molecule. The anchoring to the other electrode is kept stable using a chalcogen atom with strong bonding to a Cu(110) substrate. These non-destructive measurements permit us to investigate the variation in single-molecule conductance under different but controlled environmental conditions. Combined with density functional theory calculations, we clarify the role of the electrostatic field in the environmental effect that influences the molecular level alignment.

Highlights

On Cu(110) and found that it is bonded to the surface via an oxygen atom in a nearly flat configuration
The scanning tunnelling microscope (STM) image of a phenoxy molecule on Cu(110) shows a pair formed by a protrusion and a smaller depression (Fig. 1a), reflecting the density of states at the phenyl ring and oxygen atom, respectively
In previous works the molecular conductance was thoroughly investigated by break-junction experiments as a function of the molecular structure[36,37,38] and anchoring groups[39,40,41]

Summary

Introduction

On Cu(110) and found that it is bonded to the surface via an oxygen atom in a nearly flat configuration. When the STM tip is gradually approached to such a flat-lying phenoxy molecule on the surface at one point, the molecule flips up and makes contact to the tip apex while remaining anchored to the Cu surface via the oxygen atom, forming a molecular junction between the two electrodes. Repeated switching of a phenoxy junction is feasible with this setup. This enables us to investigate the molecular conductance with unprecedented precision and to compare the conductance of a junction in different prearranged environments to reveal the impact of surrounding molecules

Methods

Results

Conclusion