Coupling and decoupling of bilayer graphene monitored by electron energy loss spectroscopy

TL;DR

This study uses spatially resolved EELS to investigate how interlayer coupling in bilayer graphene varies with twist angle and intercalation, revealing how decoupling affects electronic and optical properties.

Contribution

It demonstrates the use of EELS to monitor twist-angle-dependent hybridization and shows that metal chloride intercalation decouples bilayer graphene, eliminating specific electronic features.

Findings

Twist angle influences energy band hybridization and optical absorption peaks.

Intercalation with metal chloride decouples bilayer graphene and removes the vHS peak.

EELS effectively monitors interlayer coupling and decoupling in bilayer graphene.

Abstract

We studied the interlayer coupling and decoupling of bilayer graphene (BLG) by using spatially resolved electron energy loss spectroscopy (EELS) with a monochromated electron source. We correlated the twist-angle-dependent energy band hybridization with Moire superlattices and the corresponding optical absorption peaks. The optical absorption peak originates from the excitonic transition between the hybridized van Hove singularities (vHSs), which shifts systematically with the twist angle. We then proved that the BLG decouples when a monolayer of metal chloride is intercalated in its van der Waals (vdW) gap, and results in the elimination of the vHS peak.