Evolution of tip shape during field evaporation of complex multilayer structures

Area of Science:

• Materials Science
• Surface Science
• Nanotechnology

Background:

• Atom-probe tomography (APT) is vital for analyzing interfacial properties in complex multilayer structures.
• Field evaporation in APT can introduce significant artefacts into 3D reconstructed data.
• Existing reconstruction algorithms often assume a spherical emitter shape, which may not hold true for multilayered materials.

Purpose of the Study:

• To investigate the origin and impact of artefacts in APT analysis of FeCoB/FeCo/MgO/FeCo/IrMn multilayer structures.
• To understand how the emitter tip shape evolves during the field evaporation of different material layers.
• To identify potential improvements for 3D data reconstruction in APT of multilayered systems.

Main Methods:

• Transmission electron microscopy (TEM) was used to observe emitter tip shapes during APT.
• Finite difference modeling was employed to simulate electric fields and evaporation processes.
• Comparison of experimental TEM observations with simulation results.

Main Results:

• The emitter tip shape in APT is not spherical, particularly for multilayer structures.
• The surface morphology of the emitter evolves dynamically during the successive evaporation of distinct material layers.
• This evolving, non-spherical morphology directly contributes to artefacts in the 3D reconstructed APT data.

Conclusions:

• The assumption of a spherical emitter shape is a primary source of artefacts in APT analysis of multilayered materials.
• Accounting for the evolving, non-spherical emitter morphology is essential for accurate interfacial property determination.
• Proposed improvements to reconstruction algorithms are needed to address these findings.