Quasiparticle scattering off phase boundaries in epitaxial graphene

Area of Science:

• Condensed Matter Physics
• Materials Science
• Surface Science

Background:

• Single layer graphene (SLG) exhibits unique electronic properties.
• Understanding the local density of states (LDOS) near graphene edges is crucial for electronic applications.
• Graphene grown on silicon carbide (SiC) offers a route to high-quality samples.

Purpose of the Study:

• To investigate the electronic structure of SLG terraces.
• To analyze the perturbations of LDOS near SLG edges.
• To interpret the observed LDOS patterns using classical standing wave models.

Main Methods:

• Scanning tunnelling microscopy (STM) was employed to probe the electronic structure.
• Samples were prepared by thermal decomposition of 6H-SiC(0001) in ultra-high vacuum.
• Fourier transform analysis of LDOS images was used to characterize electronic patterns.

Main Results:

• Armchair edges of SLG promote intervalley quasiparticle scattering, creating a (√3 x √3)R30° LDOS superstructure.
• Intrinsic doping in SLG leads to a complex LDOS pattern at the Fermi energy, combining superstructures and long-range modulations.
• Zig-zag edges and SLG/bilayer graphene junctions do not exhibit intervalley scattering.

Conclusions:

• The electronic properties of SLG edges are strongly dependent on their crystallographic orientation.
• Intrinsic doping significantly influences the electronic landscape of graphene.
• The findings provide insights into the fundamental electronic behavior of graphene nanostructures.