Quantitative annular dark field electron microscopy using single electron signals.

Area of Science:

• Materials Science
• Physics
• Chemistry

Background:

• Analyzing atomic resolution electron microscope images is often hindered by unknown or imprecisely fitted sample thickness.
• Accurate, parameter-free, column-by-column thickness quantification with single-atom precision is highly desirable for applications like simulation matching.

Purpose of the Study:

• To propose a novel, parameter-free method for quantifying sample thickness in annular dark field scanning transmission electron microscopy (ADF STEM).
• To enable accurate atom counting at the atomic scale by leveraging detector signal levels.

Main Methods:

• Utilized the single electron intensity level of the detector in ADF STEM.
• Employed mean intensity averaged over a primitive cell for atom counting, eliminating the need for fitting parameters.
• Applied the method to quantify Al (or N) atoms in aluminum nitride single crystals.

Main Results:

• Demonstrated a routine quantification method for ADF STEM images across various beam currents and dynamic range conditions.
• Successfully counted the number of Al (or N) atoms per primitive cell in aluminum nitride, ranging from 3 to 99 atoms.
• Showcased the method's utility for analyzing ultra-thin or light-element materials.

Conclusions:

• The proposed method offers a parameter-free, single-atom accurate thickness quantification for ADF STEM.
• This technique facilitates precise atom counting, crucial for advanced materials characterization and simulation validation.
• The method is versatile, applicable to diverse materials and imaging conditions.