Direct Quantifying Charge Transfer by 4D-STEM: A Study on Perfect and Defective Hexagonal Boron Nitride

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Four-dimensional scanning transmission electron microscopy (4D-STEM) enables simultaneous structural and electronic property determination.
• Accurate atomic-scale quantification in 4D-STEM is often limited by probe effects.
• Hexagonal boron nitride (h-BN) is a key material for electronic applications.

Purpose of the Study:

• To comprehensively analyze electric fields and charge densities in pristine and defective h-BN flakes using 4D-STEM.
• To investigate the impact of probe effects on quantitative charge measurements.
• To establish the capabilities of 4D-STEM for detecting charge transfer phenomena.

Main Methods:

• Combining experimental 4D-STEM with first-principle simulations.
• Analyzing charge densities and electric fields in h-BN flakes.
• Evaluating probe propagation and size-related effects on data acquisition.

Main Results:

• Precise charge quantification at individual atomic sites is hindered by probe effects.
• 4D-STEM directly measures charge transfer at the monolayer edge of h-BN.
• Sensitivity down to a few tenths of an electron and angstrom-scale resolution were achieved.

Conclusions:

• 4D-STEM is a powerful tool for studying electronic properties of 2D materials.
• The study highlights limitations and capabilities of 4D-STEM for charge analysis.
• This work provides insights into charge transfer mechanisms in h-BN.