GaN atomic electric fields from a segmented STEM detector: Experiment and simulation.

Area of Science:

• Materials Science
• Solid-State Physics
• Electron Microscopy

Background:

• Accurate characterization of atomic-scale electric fields is crucial for understanding material properties.
• Traditional methods can be limited by radiation damage or slow acquisition speeds.

Purpose of the Study:

• To measure atomic electric fields in a thin Gallium Nitride (GaN) sample using a novel 4D-STEM approach.
• To compare the performance of a segmented STEM detector with a pixelated detector and simulations.

Main Methods:

• Utilized the center-of-mass approach in 4D-scanning transmission electron microscopy (4D-STEM).
• Employed a 12-segmented STEM detector on a Spectra 300 microscope for high-speed, low-dose data acquisition.
• Compared experimental results with detailed simulations and measurements from a pixelated 4D-STEM detector.

Main Results:

• Successfully measured atomic electric fields, charge density, and potential in the GaN sample.
• The segmented detector demonstrated high recording speed, enabling measurements at reduced radiation doses.
• Identified measurement uncertainty stemming from the limited number of segments analyzed in this study.

Conclusions:

• The segmented STEM detector is a promising tool for rapid, low-dose atomic electric field mapping.
• Further analysis with more segments could improve the accuracy of the measurements.
• This method provides valuable insights into the electronic structure of materials like GaN.