Physics-based reconstruction algorithm for 3D atom probe microscopy

• Applicant: Professor Dr. Guido Schmitz
• Subject Area: Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials ; Mechanical Properties of Metallic Materials and their Microstructural Origins
• Term: from 2013 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 232117566

• Final Report Year: 2022

Final Report Abstract

New reconstruction methods were developed for high-resolution analytical microscopy by atom probe tomography, which i) are based on the evaluation of realistically calculated ion trajectories and ii) on a statistical evaluation of the distribution of a large number of events on the detector surface. The corresponding software was programmed and the basic function of the concepts was proven. For this purpose, computer-based model data sets were reconstructed on the one hand, which allow the quality of the reconstruction to be quantified exactly, and on the other hand experimental data sets, which lead to serious artefacts when evaluated with the conventional method. The investigations show that methods that attempt to build up the sample atom by atom in a "bottom-up" process can only be applied meaningfully to very small partial volumes (about 100,000 atoms), even if they rely on an exact calculation of the trajectories. When reconstructing larger volumes, missing atoms in the experimental datasets lead to selfreinforcing roughening in the tip shape, which prevents further meaningful calculation of the trajectories. Through further increases in detector efficiency, these methods could find wider application. The second method evaluates the detection densities of many events on the detector before the actual reconstruction. It leads to a significant improvement in tomographic reconstruction with a reasonable numerical effort, so that the method could establish itself as the standard in atom probe tomography. The density variation on the detector is initially used to develop the specific tip shape using differential geometry methods. Only in a second step, with knowledge of this tip shape, are the individual atoms positioned based on their individual detection data. The success of this method is proven by means of model measurements on multiple layers and the practical applicability is demonstrated.

Publications

• Atom probe reconstruction with a locally varying tip shape, Dissertation, Univ. Stuttgart 2019
  Daniel Beinke
  
• Evolution of γ/γ' phases, their misfit and volume fractions in Al10Co25Cr8Fe15Ni36Ti6 compositionally complex alloy, Materials characterization 154, (2019) 363-376
  A. M. Manzoni, S. Haas, J. M. Yu, H. M. Daoud, U. Glatzel, H. Aboulfadl, F. Mücklich, R. Duran, G. Schmitz, D. M. Többens, S. Matsumura, F. A. Vogel, N. Wanderka
  
• ‘Atom probe reconstruction with a locally varying emitter shape’, J. Microscopy and Microanalysis 25 (2019) 2
  Daniel Beinke, Guido Schmitz
  
• Extracting the shape of nanometric field emitters, Nanoscale 2020, 12: 2820-2832
  Daniel Beinke, Felicitas Bürger, Helena Solodenko, Rachana Acharya, H. Klauk, Guido Schmitz
  
• On the formation of nano-sized precipitates during cooling of NiAl- strengthened ferritic alloys, Materials Characterization 171 (2021) 110722
  R. Lawitzki, D. Beinke, D. Wang, G. Schmitz