Voltage Dependence of Molecule–Electrode Coupling in Biased Molecular Junctions

Journal Article · Wed Sep 20 00:00:00 EDT 2017 · Journal of Physical Chemistry. C

DOI:https://doi.org/10.1021/acs.jpcc.7b05567· OSTI ID:1480505

Liu, Zhen-Fei  ^[1]; Neaton, Jeffrey B. ^[2]

---

1. Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States; Department of Physics, University of California, Berkeley, California 94720, United States
2. Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States; Department of Physics, University of California, Berkeley, California 94720, United States; Kavli Energy Nanosciences Institute at Berkeley, Berkeley, California 94720, United States

Biased interfaces between individual molecules and metallic electrodes are central in many nanoscale devices. A key quantity that governs the nature of the metal–molecule interface is the degree of hybridization between frontier orbitals of the molecule and electrode continuum states. This hybridization leads to the broadening of molecular resonances, a measure of the electronic coupling to the surface. In this work, we present detailed ab initio calculations of the evolution of this electronic coupling for selected frontier orbitals with bias voltage in molecular junctions, nanoscale devices where metal–molecule interface effects are dominant. We focus on symmetric and asymmetric junctions based on an experimentally well-studied system, Au–bipyridine–Au, as examples of our method. The nature of the bias-dependent coupling that emerges from our ab initio calculations provides new physical insight into experimentally achievable systems and is a marked quantitative improvement over simple Lorentzian models often used in interpreting device measurements. Beyond molecular junctions, our approach can be straightforwardly generalized to other molecule–metal interfaces.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 1480505
• Journal Information: Journal of Physical Chemistry. C, Vol. 121, Issue 39; ISSN 1932-7447
• Country of Publication: United States
• Language: English