Multi-scale time-resolved electron diffraction: A case study in moiré materials.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Physical Chemistry

Background:

• Ultrafast-optical-pump - structural-probe measurements are crucial for studying non-equilibrium dynamics in matter.
• High-performance detectors are essential for maximizing data quality in scattering experiments.

Purpose of the Study:

• To demonstrate the utility of a hybrid pixel array direct electron detector for ultrafast electron diffraction (UED).
• To resolve weak scattering features and moiré superlattice structures in 2D heterobilayers.
• To achieve continuous time resolution for mapping dynamic processes like thermal transport.

Main Methods:

• Deployment of a hybrid pixel array direct electron detector for UED experiments.
• Utilizing a chopping technique to generate high signal-to-noise diffraction difference images.
• Performing scanning UED to map spatial and temporal thermal transport.

Main Results:

• Successful resolution of weak diffuse scattering and moiré superlattice structure in WSe₂/MoSe₂ 2D heterobilayers without zero-order peak saturation.
• Achieved signal-to-noise ratio at the shot noise limit using the detector's high frame rate and chopping technique.
• Demonstrated continuous time resolution from femtoseconds to seconds, enabling detailed mapping of thermal transport.

Conclusions:

• Hybrid pixel array detectors significantly enhance capabilities for UED experiments on delicate 2D materials.
• The high frame rate and chopping technique enable high-fidelity diffraction measurements.
• UED with fast detectors offers a powerful approach for spatiotemporal characterization of dynamic phenomena like thermal transport.