Atom Probe Tomography Reconstruction for Asymmetric Tip Shapes
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Solution Overview
Problem
Existing atom probe tomography methods struggle with inaccurate reconstruction of three-dimensional atomic distributions due to non-symmetric tip shapes, particularly in heterogeneous samples, leading to errors in tip shape estimation and reconstruction.
Innovation Solution
A method for determining three-dimensional atomic distribution by recording hit maps, dividing them into zones, identifying mass-to-charge ratios, deriving flight lengths and launch angles, and matching approximate to actual surface geometries, allowing for precise reconstruction without assuming axial symmetry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If simplifying assumptions (axial symmetry, hemispherical apex) are made for tip shape, then reconstruction complexity is reduced, but reconstruction accuracy deteriorates for heterogeneous samples
Solution Approach 1:
The tip shape is measured beforehand using scanning probe microscopy before the atom probe tomography reconstruction process. This preliminary measurement provides accurate geometric information that is then used to guide the reconstruction algorithm, eliminating the need for simplifying assumptions about tip symmetry and shape during the actual reconstruction process.
Solution Approach 2:
Scanning probe microscopy is introduced as an intermediary measurement technique to obtain accurate tip shape information. This intermediary step provides precise geometric data that bridges the gap between the physical tip shape and the reconstruction algorithm, allowing accurate reconstruction without requiring the algorithm itself to be overly complex.
2Measurement precision
If detailed tip shape measurement is implemented, then reconstruction accuracy is improved, but measurement and processing complexity increases
Solution Approach 1:
The scanning probe microscopy measurement serves multiple functions: it characterizes the tip shape for reconstruction accuracy, provides geometric constraints for the algorithm, and validates the experimental setup. This multi-functional approach justifies the additional measurement complexity by providing comprehensive information from a single measurement process.
Solution Approach 2:
The invention changes the measurement parameters from indirect inferences during reconstruction to direct geometric measurements before reconstruction. By measuring actual tip shape parameters (curvature, symmetry, apex geometry) beforehand, the system transforms the problem from estimating parameters during reconstruction to using measured parameters as known inputs, improving accuracy while managing complexity.
3Shape
If extrapolation of curvature from detected region is performed, then complete tip shape is estimated, but error propagation increases
Solution Approach 1:
The complete tip shape is measured beforehand using scanning probe microscopy, which captures the entire tip geometry including regions outside the detector field of view. This preliminary complete measurement eliminates the need for extrapolation during reconstruction, as the full tip shape information is already available from the prior measurement.
Solution Approach 2:
The actual tip shape is copied from the scanning probe microscopy measurement data and used as the reference geometry for reconstruction. Instead of estimating or extrapolating the tip shape from limited detector data, the system uses a direct copy of the measured tip geometry, ensuring accuracy without error propagation from extrapolation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method provides highly accurate reconstruction of three-dimensional atomic distributions by accurately estimating tip shapes, overcoming the limitations of previous methods that rely on simplifying assumptions.
Implementation Method 1
A high electric field (>10 V/nm) is thereby induced at the apex of the tip such that the atoms at the surface of the apex are ionized
Implementation Method 2
a laser pulse is added to trigger the evaporation process by supplying additional thermal energy such that the atoms at the apex can overcome the energy barrier of evaporation
Implementation Method 3
Evaporated ions are detached from the tip surface and are accelerated towards the detector according to the electric field distribution between the tip and the detector
Implementation Method 4
The TOF is measured as the time difference between the arrival time (on the detector) and the onset of a voltage pulse or laser pulse which triggers the evaporation process. By analyzing the time of flight of the atoms, the mass-to-charge ratio of the species can be determined
Data Source
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AI summary
A method (100) for determining a three-dimensional atomic distribution of a sample (201) having a tip, during an atom probe tomography process. The method accounts for the tip not being axial symmetric and not having a hemispherical shaped apex throughout the evaporation process.