Electronic and plasmonic phenomena at graphene grain boundaries

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Graphene's unique electronic and mechanical properties make it vital for optoelectronics and plasmonics.
• Chemical vapour deposition (CVD) is a key technique for producing graphene for technological applications.
• Characterizing grain boundaries in CVD-graphene is crucial but challenging.

Purpose of the Study:

• To develop and apply an infrared nano-imaging technique for visualizing and investigating grain boundaries in CVD-graphene.
• To probe the electronic properties of individual grain boundaries and their impact on graphene's performance.

Main Methods:

• Utilizing surface plasmon interference generated by reflections and scattering at graphene grain boundaries.
• Employing infrared nano-imaging to record and analyze plasmon interference patterns.
• Mapping large-area CVD graphene films and analyzing individual grain boundaries.

Main Results:

• Successfully visualized and mapped grain boundaries in large-area CVD graphene films.
• Demonstrated that grain boundaries act as electronic barriers, impeding electrical transport and plasmon propagation.
• Quantified the effective width of these barriers (approximately 10-20 nm), relating it to electronic screening and the Fermi wavelength.

Conclusions:

• Identified a microscopic mechanism explaining the reduced electron mobility in CVD-graphene.
• Showcased the potential of using these electronic barriers for tunable plasmon reflectors and phase retarders in graphene plasmonic circuits.