Analytical Field Ion Microscopy

Project Description

The predecessor of Atom probe tomography (APT), called the field ion microscopy (FIM) is known for its high spatial resolution, but at the expense of the chemical identity. To achieve improved spatial accuracy, data mining routines are developed here. Applying these routines, data extracted from a sequence of FIM images of W. The imaging distortions are analysed by comparing with atomistic and FIM image simulations, showing that the imaged atomic displacements are a consequence of the electrostatic field redistributions. To tackle the FIM's inability to discern between atoms of different chemical species, the development of a chemically-sensitive anlytical FIM (aFIM) was developed. This technique is used to show the segregation of Re to a dislocation in a creep deformed Ni alloy.

Related Publications

• "Three-Dimensional Atomically Resolved Analytical Imaging with a Field Ion Microscope" - Microscopy and Microanalysis July. 2021. View Publication
  The research showcases a hybrid experimental method combining atom probe tomography (APT) and field ion microscopy (FIM) to achieve atomic resolution with elemental discrimination, a feat neither technique can fully accomplish on its own. By utilizing two atom probe instruments—one with a straight flight path and another with a reflectron lens—for time-of-flight mass spectrometry alongside FIM, the study establishes protocols to distinguish field-evaporated signals from a large field-ionized background. This approach, termed analytical field ion microscopy (aFIM), addresses the challenges of accurately detecting and identifying individual ions, offering a unique solution for linking nanoscale chemical variations to physical properties.
• "Revealing atomic-scale vacancy-solute interaction in nickel" - Scripta Materialia May. 2021. View Publication
  The study focuses on the impact of crystalline imperfections on the physical and mechanical properties of materials, highlighting the challenge of imaging individual vacancies and their atomic surroundings. Using a creep-deformed binary Ni-2 at.% Ta alloy, the research employs atom probe tomography and field ion microscopy, enhanced by density-functional theory and time-of-flight mass spectrometry, to reveal a random Ta distribution and its positive correlation with vacancies. This supports the previously predicted positive solute-vacancy interactions through atomistic simulations.
• "Imaging individual solute atoms at crystalline imperfections in metals" - New Journal of Physics Nov. 2019. View Publication
  The study introduces an advanced method for chemistry-sensitive field-ion microscopy (FIM) by integrating it with time-of-flight mass-spectrometry (tof-ms) and data mining, termed analytical-FIM (A-FIM). This approach enables elemental identification and correlates it to FIM images, offering true atomic resolution and the ability to directly image individual atoms and crystalline defects that significantly influence material properties. A-FIM's capabilities are demonstrated through the identification of individual rhenium (Re) atoms within crystalline defects in Ni–Re alloys, aiding in understanding how Re enhances the durability of Ni-based superalloys at high temperatures.
• "Impact of local electrostatic field rearrangement on field ionization" - Journal of Physics D. Feb. 2018. View Publication
  Field ion microscopy (FIM) achieves true atomic resolution imaging by utilizing the high charge density on surfaces to ionize gas atoms, a process enhanced by field evaporation. This study introduces a novel image processing algorithm that tracks individual atoms on the surface, allowing for quantitative analysis of atomic position shifts. Through a combination of experimental work and molecular dynamics simulations, it was confirmed that these shifts are tied to electrostatic field rearrangements affecting the ionization zone of imaging gas. The findings underscore significant implications for the advancement of 3D FIM data reconstruction, particularly for the precise quantification of lattice strains and the characterization of crystalline defects at the atomic level.