Interfacial Hopping Integral as a Predictive Descriptor for Electron Transport: Saturated Alkane Junctions

Area of Science:

• Surface Science and Nanotechnology
• Molecular Electronics
• Quantum Transport

Background:

• Electron transport across interfaces is crucial for many physical phenomena.
• Orbital overlap is a known factor influencing electron transport, but its experimental measurement is challenging.
• Understanding single-molecule conductance requires precise quantification of interfacial electronic coupling.

Purpose of the Study:

• To experimentally establish and validate the interfacial hopping integral (t_eld-mol) as a predictive descriptor for single-molecule conductance.
• To correlate molecular conductance with quantifiable parameters like molecular tilt (tilt_mol) in functionalized alkane junctions.
• To develop a theoretical model that explains and generalizes conductance variations in diverse molecular junctions.

Main Methods:

• Utilized scanning tunneling microscopy and molecular-junction mapping techniques.
• Correlated single-molecule conductance measurements with molecular tilt (tilt_mol) for π- and σ-type headgroups.
• Employed a tight-binding model with Newns-Anderson-Grimley theory to analyze electron transport across metal-molecule interfaces.

Main Results:

• Successfully extracted the interfacial hopping integral (t_eld-mol), quantifying orbital overlap between contacting atoms.
• Generated conductance heatmaps using a theoretical model that qualitatively match experimental observations.
• Rationalized existing literature findings on alkanedithiol conductance, linking them to molecular tilt and interfacial hopping integral variations.

Conclusions:

• The interfacial hopping integral (t_eld-mol) serves as a robust, experimentally validated descriptor for single-molecule conductance.
• Molecular tilt (tilt_mol) significantly influences conductance by modulating the interfacial hopping integral.
• The developed theoretical framework provides a generalized approach to understanding electron transport in various molecular junctions.