Controlling and Observing Sharp-Valleyed Quantum Interference Effect in Single Molecular Junctions.

Area of Science:

• Molecular electronics
• Quantum interference phenomena
• Nanoscale science

Background:

• Quantum interference (QI) is crucial for molecular electronics.
• Controlling QI in single molecular junctions is challenging but desirable.
• Existing methods often involve altering molecular structure or redox states.

Purpose of the Study:

• To investigate the control of QI in meta-benzene based molecules (meta-BT) using electrode potential.
• To demonstrate tunable conductance in single molecular junctions.
• To explore the potential for creating effective molecular switches.

Main Methods:

• Fabrication and characterization of single molecular junctions using meta-BT as the molecule and dihydrobenzo[b]thiophene as the anchoring group.
• Electrochemical gating by manipulating electrode potential in an electrolyte.
• Conductance measurements across a range of electrode potentials.
• Theoretical calculations of transmission functions and work functions.

Main Results:

• Demonstrated control over the QI effect in meta-BT molecular junctions by varying electrode potential.
• Observed a conductance change of over two orders of magnitude (<10^-6.0 to 10^-3.3 G0) without changing the molecule's redox state.
• Achieved conductance values higher than para-BT, attributed to energy level alignment shifts.
• Theoretical calculations showed good agreement with experimental results, confirming destructive QI.

Conclusions:

• Electrode potential can effectively tune the QI effect in molecular junctions.
• This electrochemical gating method provides a pathway for developing molecular switches.
• The findings offer a novel approach for controlling molecular conductance without redox state changes.