Direct imaging of graphene edges: atomic structure and electronic scattering

Area of Science:

• Materials Science
• Condensed Matter Physics
• Surface Science

Background:

• Graphene synthesis via chemical vapor deposition (CVD) on copper (Cu) foils is a key method for producing large-area graphene.
• Understanding the atomic structure and electronic properties of graphene grain boundaries is crucial for its electronic applications.
• Edge structure significantly influences graphene's electronic behavior.

Purpose of the Study:

• To investigate the atomic structure of graphene grain edges synthesized on Cu foils using scanning tunneling microscopy (STM).
• To correlate observed edge structures with predicted electronic properties, specifically intervalley backscattering.
• To analyze the electronic behavior near different types of graphene edges.

Main Methods:

• Atomically resolved scanning tunneling microscopy (STM) was employed.
• Graphene grains were synthesized on copper foils via chemical vapor deposition (CVD).
• Microscopic and macroscopic edge orientations were analyzed at the atomic scale.

Main Results:

• Most graphene grain edges were found to be parallel to the zigzag crystallographic direction.
• Microscopic roughness at zigzag edges also followed zigzag directions with characteristic 120° turns.
• A distinct standing wave pattern with a periodicity of approximately 3a/4 was observed near rare armchair-oriented edges.

Conclusions:

• The observed zigzag edge structure is consistent with minimal electronic scattering.
• The standing wave pattern near armchair edges supports theoretical predictions of electronic intervalley backscattering.
• STM provides atomic-level insights into the structure-property relationships of graphene edges, crucial for device performance.