Abstract
Reconstructions in atom probe tomography (APT) are plagued by image distortions arising from changes in the specimen geometry throughout the experiment. The simplistic and inaccurate geometrical assumptions that underpin the conventional reconstruction approach account for much of this distortion. Here we extend our previous work of modelling APT experiments using level set methods to three dimensions (3D). This model is used to generate and subsequently reconstruct synthetic APT datasets from electron tomography (ET) of an multiphase specimen. Finally, we apply our model to the reconstruction of an experimental field-effect transistor (finFET) dataset. This model-driven reconstruction successfully reduces density distortions compared to conventional methods. By combining prior knowledge about the specimen geometry from sources such as ET, such an approach promises new distortion correcting APT reconstruction applicable to complex specimen geometries.
Highlights
Atom probe tomography (APT) is a three-dimensional (3D) mass spectrometry technique for materials characterisation in which surface atoms on a needle shaped specimen are ionised under a pulsed surface electric field via the physical process of field evaporation, and are accelerated towards a two-dimensional (2D) position-sensitive detector
In this study we presented a full 3D continuum model for specimen field evaporation in atom probe tomography (APT)
By tracking the specimen surface using a level set method, our model can capture a wide range of APT phenomena including crystallographic faceting and evaporation of voids
Summary
Atom probe tomography (APT) is a three-dimensional (3D) mass spectrometry technique for materials characterisation in which surface atoms on a needle shaped specimen are ionised under a pulsed surface electric field via the physical process of field evaporation, and are accelerated towards a two-dimensional (2D) position-sensitive detector. Current reconstruction algorithms assume ion trajectories obey a mathematical point-projection law from a specimen apex that remains hemispherical throughout the field evaporation process [1,2,3]. This assumption is often highly unphysical and a dominant source of error. Our previous work [15,16,17] has demonstrated that level set methods could provide the speed and generality required, but have so far fallen short of fully simulating electrostatics in 3D Another promising reconstruction approach aims to build up the specimen surface from the detected ions in reverse order [18, 19]. This study extends our 2D model [17] to full 3D and aims to show how this new model can be used to perform rapid modelling of realistic specimen geometries to improve understanding of phenomena in APT experiments, and to directly drive the APT reconstruction procedure
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