Negative differential resistance at sequential single-electron tunnelling through atoms and molecules

Area of Science:

• Quantum electronics
• Molecular electronics
• Solid-state physics

Background:

• Single-electron transistors (SETs) are crucial for nanoscale electronics.
• Understanding electron transport through molecular islands is key to advancing SETs.
• Quantized energy spectra in molecular islands influence transport properties.

Purpose of the Study:

• To investigate electron transport in SETs utilizing single atoms or molecules as islands.
• To analyze the impact of electric fields on tunneling barriers in molecular SETs.
• To explore the potential of observed transport phenomena for integrated circuit development.

Main Methods:

• Combined theory of sequential single-electron transport (Averin and Korotkov).
• Ab initio calculations of molecular orbitals and energy spectra using density functional theory (NRLMOL).
• Bardeen's approximation for tunneling rates based on wavefunction overlap.

Main Results:

• Calculations predict extended branches with negative differential resistance in DC I-V curves of molecular SETs.
• This negative differential resistance arises from source-drain electric field enhancement of a tunneling barrier.
• The predicted effect aligns with experimental observations from multiple research groups.

Conclusions:

• The study provides a theoretical framework for understanding electron transport in molecular SETs.
• Negative differential resistance in molecular SETs is a viable phenomenon with experimental validation.
• This effect offers potential for improving density and performance in hybrid semiconductor/nanodevice integrated circuits.