In Operando Angle-Resolved Photoemission Spectroscopy with Nanoscale Spatial Resolution: Spatial Mapping of the...

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Understanding performance limits in 2D material devices requires resolving electronic properties at the mesoscale under operating conditions.
• Twisted bilayer graphene exhibits unique electronic properties influenced by its structure.

Purpose of the Study:

• To map the quasiparticle electronic structure of a twisted bilayer graphene device using nanoARPES.
• To correlate mesoscale structural variations with electronic properties under static and operating conditions.

Main Methods:

• Angle-resolved photoemission spectroscopy with nanoscale spatial resolution (nanoARPES).
• Mapping electronic dispersion and linewidth of Dirac cones across the device.
• Applying current and electrostatic gating to study device operation.

Main Results:

• Identified a range of twist angles (9.8°–12.7°) due to microscopic rotational domains.
• Observed strong electric fields (up to 0.75 V/μm) at domain boundaries under operation.
• Demonstrated nanoARPES's capability to link structure and electronic states.

Conclusions:

• NanoARPES can probe electronic states in 2D materials at the mesoscale under operating conditions.
• Extrinsic factors like structural domains significantly influence device performance.
• This method can differentiate extrinsic influences from intrinsic electronic behavior.