Reflections on the Spatial Performance of Atom Probe Tomography in the Analysis of Atomic Neighborhoods

Abstract

Atom probe tomography (APT) is often introduced as providing “atomic-scale” mapping of the composition of materials and as such is often exploited to analyze atomic neighborhoods within a material. Yet quantifying the actual spatial performance of the technique in a general case remains challenging, as it depends on the material system being investigated as well as on the specimen's geometry. Here, by using comparisons with field-ion microscopy experiments, field-ion imaging and field evaporation simulations, we provide the basis for a critical reflection on the spatial performance of APT in the analysis of pure metals, low alloyed systems and concentrated solid solutions (i.e., akin to high-entropy alloys). The spatial resolution imposes strong limitations on the possible interpretation of measured atomic neighborhoods, and directional neighborhood analyses restricted to the depth are expected to be more robust. We hope this work gets the community to reflect on its practices, in the same way, it got us to reflect on our work.

Controlled Doping of Electrocatalysts through Engineering Impurities

“…A slice through the APT point cloud, Figure 1d, shows that B (in blue) is located inside Pd-B 40 , not segregated to its surface, and the 1D composition profile, Figure 1e, confirms the ingress of over 2 at% B within the Pd nanocatalyst. A nearest-neighbor analysis indicates no B clustering tendency within the resolution limits of APT, [29,30] Incorporating chemical potentials Δμ B into the modeling (cf. Figure 1a) allows us to determine which adsorption sites are thermodynamically accessible.…”

3D Nanoscale Mapping of Short‐Range Order in GeSn Alloys

“…A very recent paper concludes that the neighborhood analysis in the vertical ( Z ) direction is more robust in APT, and the mean offset d z is within a single atomic layer. [ 43 ] Interestingly, in diamond cubic Ge and GeSn(001) epitaxial films, true KNN and true (K−1)NN are indeed in different atomic layers in the Z direction for K = 2, 3, 4, which enables clear distinctions statistically. We note that the quality of APT data could impact this assumption.…”

Correlating atom probe tomography with x-ray and electron spectroscopies to understand microstructure–activity relationships in electrocatalysts

“…This is where the inherent strength of APT can be best used. In APT, the spatial resolution or size of the smaller resolvable microstructural feature of interest depends on its composition, 53,54 and it can be assumed to be below 1 nm in all three dimensions 55 but is typically an order of magnitude better in depth, 53,56 as summarized in Figure 2a. Now, let us consider common microstructural features, for instance, stacking faults, dislocations, grain boundaries, and secondary phases, along with their respective dimensions, as shown in Figure 2b.…”