Automated Atom-By-Atom Three-Dimensional (3D) Reconstruction of Field Ion Microscopy Data

Abstract

An automated procedure has been developed for the reconstruction of field ion microscopy (FIM) data that maintains its atomistic nature. FIM characterizes individual atoms on the specimen's surface, evolving subject to field evaporation, in a series of two-dimensional (2D) images. Its unique spatial resolution enables direct imaging of crystal defects as small as single vacancies. To fully exploit FIM's potential, automated analysis tools are required. The reconstruction algorithm developed here relies on minimal assumptions and is sensitive to atomic coordinates of all imaged atoms. It tracks the atoms across a sequence of images, allocating each to its respective crystallographic plane. The result is a highly accurate 3D lattice-resolved reconstruction. The procedure is applied to over 2000 tungsten atoms, including ion-implanted planes. The approach is further adapted to analyze carbides in a steel matrix, demonstrating its applicability to a range of materials. A vast amount of information is collected during the experiment that can underpin advanced analyses such as automated detection of "out of sequence" events, subangstrom surface displacements and defects effects on neighboring atoms. These analyses have the potential to reveal new insights into the field evaporation process and contribute to improving accuracy and scope of 3D FIM and atom probe characterization.

Current Challenges and Opportunities in Microstructure-Related Properties of Advanced High-Strength Steels

“…[375] Additional processing of sequence series of such images allows for a full atomistic reconstruction of the local atomic arrangement. [376,377] 3DFIM has been employed to study e.g., radiation damages, [378] precipitation, [372] crystalline defects dislocation [375] , and solute interactions with defects. [379] Recent developments and application of machine learning to FIM [380] further enhance the data obtained from these techniques.…”

A model to predict image formation in the three-dimensional field ion microscope

“…Successful attempts at reconstructing 3D data volumes from FIM images have already been reported [15,16] and automated procedures were developed for the reconstruction of accurate 3D, latticeresolved atom maps. These procedures consist in the application image processing techniques to detect the positions of hundreds of atoms within each micrograph and to digitally track them across a sequence of FIM images, from the moment when they are first revealed at the surface of the specimen until their field evaporation.…”

Interfaces and defect composition at the near-atomic scale through atom probe tomography investigations

“…Field-ion-based techniques were initially developed for studying surfaces 1,2 : The field ion microscope (FIM) reveals the structure of a material with atomic-scale resolution 3 , at least in some parts of the image, while the implementation of a time-of-flight spectrometer onto a field ion microscope, which is the atom probe, targeted the elemental identification of atoms images at the surface 4 . The level of detail of the intimate structure of crystalline defects, being grain boundaries 5 or dislocations 6 , brought by FIM was astonishing, and the technique is unrivalled when it comes to observing individual vacancies 7,8 . FIM provides three-dimensional information: the two-dimensions are provided by the projected image of the surface formed by the ionisation of the imaging gas atoms, while the third dimension arises from the possibility to sequentially remove atoms from the specimen itself by field evaporation [8][9][10][11][12][13] .…”

“…The level of detail of the intimate structure of crystalline defects, being grain boundaries 5 or dislocations 6 , brought by FIM was astonishing, and the technique is unrivalled when it comes to observing individual vacancies 7,8 . FIM provides three-dimensional information: the two-dimensions are provided by the projected image of the surface formed by the ionisation of the imaging gas atoms, while the third dimension arises from the possibility to sequentially remove atoms from the specimen itself by field evaporation [8][9][10][11][12][13] .…”