Point-by-point compositional analysis for atom probe tomography

This new alternate approach to data processing for analyses that traditionally employed grid-based counting methods is necessary because it removes a user-imposed coordinate system that not only limits an analysis but also may introduce errors. We have modified the widely used “binomial” analysis for APT data by replacing grid-based counting with coordinate-independent nearest neighbour identification, improving the measurements and the statistics obtained, allowing quantitative analysis of smaller datasets, and datasets from non-dilute solid solutions. It also allows better visualisation of compositional fluctuations in the data. Our modifications include:.
• using spherical k-atom blocks identified by each detected atom's first k nearest neighbours.
• 3D data visualisation of block composition and nearest neighbour anisotropy.
• using z-statistics to directly compare experimental and expected composition curves.Similar modifications may be made to other grid-based counting analyses (contingency table, Langer-Bar-on-Miller, sinusoidal model) and could be instrumental in developing novel data visualisation options.

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