Microscopic study of electrical transport through individual molecules with metallic contacts: I. "Band" lineup, voltage drop and high-field transport

TL;DR

This paper investigates the microscopic mechanisms of electrical transport in single-molecule devices with metallic contacts, focusing on band alignment, voltage distribution, and high-field effects using first-principles calculations.

Contribution

It introduces a first-principles self-consistent Green's function approach to analyze charge and potential responses in molecular heterostructures under electrical bias.

Findings

Charge and potential response of atomic groups analyzed

Band lineup and voltage drop characterized

High-field transport behavior studied

Abstract

We present the first in a series of microscopic studies of electrical transport through individual molecules with metallic contacts. We view the molecules as ``heterostructures'' composed of chemically well-defined atomic groups, and analyze the device characteristics in terms of the charge and potential response of these atomic-groups to the perturbation induced by the metal-molecule coupling and the applied electrical field, which are modeled using a first-principles based self-consistent matrix Green's function (SCMGF) method. As the first example, we examine the devices formed by attaching two benzene-based molecular radicals--phenyl dithiol (PDT) and biphenyl dithiol (BPD)--symmetrically onto two semi-infinite gold electrodes through the end sulfur atoms.