Materials property mapping from atomic scale imaging via machine learning based sub-pixel processing

Direct visualization of the atomic structure in scanning transmission electron microscopy has led to a comprehensive understanding of the structure-property relationship. However, a reliable characterization of the structural transition on a picometric scale is still challenging because of the limited spatial resolution and noise. Here, we demonstrate that the primary segmentation of atomic signals from background, succeeded by a denoising process, enables structural analysis in a sub-pixel accuracy. Poisson noise is eliminated using the block matching and three-dimensional filtering with Anscombe transformation, and remnant noise is removed via morphological filtering, which results in an increase of peak signal-to-noise ratio from 7 to 11 dB. Extracting the centroids of atomic columns segmented via K-means clustering, an unsupervised method for robust thresholding, achieves an average error of less than 0.7 pixel, which corresponds to 4.6 pm. This study will contribute to a profound understanding of the local structural dynamics in crystal structures.

Automated summary

This study demonstrates the possibility of achieving structural analysis with sub-pixel accuracy by segmenting atomic signals from background and applying denoising techniques. The elimination of Poisson noise and residual noise greatly increases the peak signal-to-noise ratio. Extracting centroids of atomic columns using K-means clustering allows for a deeper understanding of the local structural dynamics.