Chemical control over the energy-level alignment in a two-terminal junction

Area of Science:

• Molecular electronics
• Chemical physics
• Materials science

Background:

• Molecular transistors use external gating to control energy-level alignment.
• Two-terminal molecular junctions lack gates and face Fermi-level pinning, hindering control.
• Controlling energy-level alignment is crucial for molecular electronic devices.

Purpose of the Study:

• To investigate chemical modifications for controlling energy-level alignment in two-terminal molecular junctions.
• To enhance the tunnelling current in molecular junctions without using external gates.
• To demonstrate an alternative method for regulating electrical properties in molecular electronic systems.

Main Methods:

• Utilized two-terminal molecular tunnelling junctions with self-assembled monolayers.
• Chemically altered the molecular component between its stable radical and non-radical forms.
• Maintained the supramolecular structure of the junction throughout the chemical modification process.

Main Results:

• Achieved a two-orders-of-magnitude enhancement in tunnelling current.
• Demonstrated successful control over energy-level alignment via chemical modification.
• Showcased the ability to tune electrical properties through intrinsic molecular changes.

Conclusions:

• Purely chemical modifications can effectively regulate energy-level alignment in molecular junctions.
• Chemical control of molecular orbitals presents a viable alternative to gating for two-terminal devices.
• This approach offers a promising pathway for developing novel molecular electronic components.