Materials analysis with a position‐sensitive atom probe

Abstract

SUMMARY A position‐sensitive detector has been combined with time‐of‐flight mass spectrometry in the atom probe field‐ion microscope to yield a system in which both chemical identity and spatial information are obtained for individual ions field‐evaporated from the specimen surface. This allows the variations in composition originally present in the sample to be reconstructed in 3‐D with sub‐nanometre resolution. The prototype position‐sensitive atom probe is being used to study phase chemistry in a number of metallurgical alloys, including accurate composition determination of 1–2 nm Cu‐rich precipitates formed in Fe–1.3% Cu–1.4%Ni aged to peak hardness. Other applications of the position‐sensitive atom probe (POSAP) include the analysis of surface layers on superconductors and atom probe studies of semiconductor multiple quantum wells. These initial applications of the instrument are reported, and the limitations and intended improvements to the instrument are discussed.

Fine scale investigation of some phenomena in metallic alloys by field ion microscopy and atom probe microanalysis

“…FIM images of this steel aged at 400°C for a long time exhibit a duplex contrast which can be attributed to a fine-scale fully interconnected a/a' isotropic sponge-like microstructure [20]. Theses features have already been observed in Fe-Cr, Fe-Cr-Co, Fe-Cr-Ni systems [21,22] and related steels [22,24].…”

“…The unlimited mass range of the TOF spectrometer as well as the possibility to detect light elements (B, Li...) give to this technique the possibility to investigate a large variety of materials. Moreover, the emergence of new generations of three dimensional atom-probes [24,31] with which the specimen can be chemically and analytically reconstructed on a nearly atomic scale, will open new fields for these techniques in material science.…”

Dynamical Ising Model Simulations of Nucleation and Growth in Copper-Cobalt Alloys

“…With APFIM microanalysis, composition-depth profiles can be obtained with 1-2nm lateral resolution, and a depth resolution of a single atomic layer. In a more recent variant of the technique, the position-sensitive atom probe (PoSAP) [5], this microanalysis capability is extended to a full three-dimensional reconstruction of the distribution of atoms originally present in a volume approximately 20nm x 20nm x 20nm in the solid, with sub-nanometre spatial resolution. It is now possible to make direct comparisons between the results of simulations and the atomic-scale chemical measurements.…”

Microanalysis near particles and voids at grain boundaries

“…Atom probe microanalysis is another technique which can yield valuable elemental information at the atomic level (Cerezo et al, 1989). Samples are formed into a sharp tip which is imaged in a field ion microscope.…”