Thermally activated electron transport in single redox molecules

Area of Science:

• Molecular electronics
• Surface science
• Electrochemistry

Background:

• Understanding electron transport through single molecules is key to developing molecular electronic devices.
• Perylene tetracarboxylic diimides (PTCDIs) are redox-active molecules with potential applications in molecular electronics.
• The interface between molecules and electrodes significantly influences charge transport properties.

Purpose of the Study:

• To investigate electron transport through single PTCDI molecules covalently linked to gold electrodes.
• To determine the influence of different linker groups on molecular conductance.
• To explore the effects of electrochemical gate voltage and temperature on electron transport.

Main Methods:

• Fabrication of single-molecule junctions using PTCDIs with varying linker groups attached to gold electrodes.
• Electrochemical measurements of current-voltage characteristics as a function of gate voltage.
• Temperature-dependent conductance measurements in different solvent environments.

Main Results:

• Molecular conductance is sensitive to linker groups due to varying electronic coupling with electrodes.
• Current is reversibly controlled over 2-3 orders of magnitude by gate voltage, peaking near the redox potential.
• Electron transport exhibits a thermally activated process, consistent with a two-step sequential electron transfer mechanism.

Conclusions:

• The transport mechanism in these PTCDI molecular junctions is consistent across different linker groups.
• A two-step sequential electron transfer model effectively describes both gate voltage and temperature dependencies.
• This study provides insights into controlling and understanding electron transport at the single-molecule level.