# Variable-angle high-angle annular dark-field imaging: application to three-dimensional dopant atom profiling

## TL;DR

This paper introduces a new imaging technique to accurately determine the 3D positions of dopant atoms in materials.

## Contribution

The study introduces variable-angle HAADF imaging to improve 3D dopant atom profiling accuracy and precision.

## Key findings

- Variable-angle HAADF imaging improves precision and accuracy in 3D dopant atom profiling.
- Combining data from two detectors reduces uncertainty in depth position measurements.
- The method can uniquely identify atomic configurations previously indistinguishable.

## Abstract

Variable-angle high-angle annular dark-field (HAADF) imaging in scanning transmission electron microscopy is developed for precise and accurate determination of three-dimensional (3D) dopant atom configurations. Gd-doped SrTiO3 films containing Sr columns containing zero, one, or two Gd dopant atoms are imaged in HAADF mode using two different collection angles. Variable-angle HAADF significantly increases both the precision and accuracy of 3D dopant profiling. Using image simulations, it is shown that the combined information from the two detectors reduces the uncertainty in the dopant depth position measurement and can uniquely identify certain atomic configurations that are indistinguishable with a single detector setting. Additional advances and applications are discussed.