Imaging atomic motion of light elements in 2D materials with 30 kV electron microscopy

Area of Science:

• Materials Science
• Condensed Matter Physics
• Electron Microscopy

Background:

• Scanning transmission electron microscopy (STEM) is crucial for atomic-scale characterization of 2D materials.
• Electron beam radiation damage remains a significant challenge, particularly for light elements and dynamic processes.
• Observing light elements alongside heavy elements in 2D materials under electron irradiation is difficult.

Purpose of the Study:

• To investigate electron radiation damage in 2D tungsten disulfide (WS2) at 30 kV STEM.
• To demonstrate the capability of integrated differential phase contrast STEM (iDPC-STEM) for real-time imaging of beam-induced defect dynamics.
• To reveal the motion of light elements, such as sulfur, near defects and edges in WS2.

Main Methods:

• Utilized low-voltage (30 kV) scanning transmission electron microscopy (STEM).
• Employed integrated differential phase contrast STEM (iDPC-STEM) for atomic electrostatic potential imaging.
• Captured real-time dynamics of beam-induced defects and atom movement.

Main Results:

• 2D WS2 exhibits electron radiation damage during 30 kV STEM imaging.
• iDPC-STEM successfully captured real-time dynamics of beam-induced defects.
• Single sulfur atom motion near defects and edges in WS2 was observed, which is invisible with conventional annular dark-field STEM at the same dose.
• iDPC-STEM offers significant speed and data processing advantages over camera-based STEM techniques.

Conclusions:

• Low-voltage STEM imaging induces radiation damage in 2D WS2.
• iDPC-STEM is a powerful technique for damage-free, real-time atomic-scale imaging of dynamic processes in 2D materials.
• iDPC-STEM enables the visualization of light elements and their dynamics, overcoming limitations of conventional STEM methods.