Sequential electron transport and vibrational excitations in an organic molecule coupled to few-kayer graphene electrodes

TL;DR

This study demonstrates sequential electron transport and vibrational excitations in a molecular device with graphene electrodes, revealing intermediate electron-phonon coupling effects supported by experimental and theoretical analysis.

Contribution

It introduces a new experimental setup with graphene electrodes and provides combined experimental and computational insights into vibrational excitations in molecular electronics.

Findings

Observation of inelastic co-tunneling and single-electron transport coexistence

Identification of vibrational-assisted excitations due to intermediate electron-phonon coupling

Agreement between experimental vibrational modes and density functional theory calculations

Abstract

Graphene electrodes are promising candidates to improve reproducibility and stability in molecular electronics through new electrode-molecule anchoring strategies. Here we report sequential electron transport in few-layer graphene transistors containing individual curcuminoid-based molecules anchored to the electrodes via pi-pi orbital bonding. We show the coexistence of inelastic co-tunneling excitations with single-electron transport physics owing to an intermediate molecule-electrode coupling; we argue that an intermediate electron-phonon coupling is the origin of these vibrational-assisted excitations. These experimental observations are complemented with density functional theory calculations to model electron transport and the interaction between electrons and vibrational modes of the curcuminoid molecule. We find that the calculated vibrational modes of the molecule are in agreement with the experimentally observed excitations.