Building Large-Domain Twisted Bilayer Graphene with van Hove Singularity

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Twisted bilayer graphene (tBLG) exhibits unique phenomena due to van Hove Singularities (VHS).
• Scalable, angle-controlled production of high-quality tBLG remains a significant challenge.
• Interfacial contamination hinders the desired electronic properties in tBLG.

Purpose of the Study:

• To develop a facile and scalable method for preparing high-quality tBLG with controlled twist angles.
• To investigate the electronic structure and optical properties of the synthesized tBLG.
• To fabricate high-performance photodetectors utilizing the unique properties of tBLG.

Main Methods:

• Layer-by-layer transfer of graphene monolayers without polymer contamination.
• Angle-resolved photoemission spectroscopy (ARPES) with submicrometer spatial resolution.
• Fabrication of photodetectors from the synthesized tBLG.

Main Results:

• Achieved large domain sizes (>100 μm) tBLG with controlled twist angles.
• Confirmed the formation of minigaps and VHSs in the electronic structure via micro-ARPES.
• Observed a ~20-fold enhancement in Raman G-band intensity, indicating high quality.
• Demonstrated photodetectors with up to ~6 times enhanced photocurrent generation.

Conclusions:

• The developed clean transfer method enables scalable production of high-quality, angle-controlled tBLG.
• The resulting tBLG exhibits strong light-matter interactions due to VHS.
• This tBLG is suitable for fabricating high-performance optoelectronic devices like photodetectors.