Relevance of Shockley states on the electrical and thermoelectric response of gold-based single-molecule junctions

TL;DR

This study uses ab initio simulations to demonstrate that Shockley surface states on gold (111) surfaces are crucial for accurately predicting the electrical and thermoelectric properties of gold-based single-molecule junctions, and that these states can be tuned to modify responses.

Contribution

The paper reveals the importance of Shockley surface states in gold (111) for molecular junctions and shows how their energy can be controlled to tune electrical and thermoelectric responses.

Findings

Gold (111) surface states significantly influence junction properties.

Including 5d orbitals is essential to observe surface states in simulations.

Controlled shifting of surface state energy tunes junction responses.

Abstract

Noble metals break preferably exposing (111)-oriented surfaces, that host Shockley type surface states (SSs). Nevertheless, the relevance of SSs on the electrical properties of gold-based molecular junctions has not been explored in detail yet. Here, we present ab initio simulations that show how the gold (111) SS, that lies approximately 0.5 eV below the Fermi energy, is key to determining correctly the electrical and thermoelectric response of the above junctions. We show how the ability to shift in a controlled way the energy position of gold SS enables us to tune the electrical and thermoelectric response of gold molecular junctions. We also show that gold's SS appears in our simulations only if the 5d orbitals are included explicitly in the valence shell. To illustrate this behaviour, we discuss in detail Benzenediamine (BDA) and Benzenedicarbonitrile (BDCN) gold (111) junctions.