Revealing the 3-dimensional shape of atom probe tips by atomic force microscopy

Area of Science:

• Materials Science
• Nanotechnology
• Surface Science

Background:

• Atom probe tomography (APT) is a powerful technique for nanoscale material analysis.
• Accurate reconstruction of APT data relies heavily on precise knowledge of the specimen tip's geometry.
• Existing methods lack the capability to quantitatively determine the 3D shape of atom probe tips.

Purpose of the Study:

• To introduce and validate a novel method using atomic force microscopy (AFM) for quantitative 3D characterization of atom probe tips.
• To investigate the impact of tip shape deviations on APT data accuracy and artifact formation.
• To provide a tool for understanding physical mechanisms in laser-assisted APT.

Main Methods:

• Utilizing atomic force microscopy (AFM) to quantitatively measure the 3D shape of atom probe tips.
• Developing a technique to overcome the challenge of aligning two extremely sharp tips for measurement.
• Analyzing apex and shank regions of multiple atom probe tips.

Main Results:

• Successfully measured the 3D tip shape of three different atom probe tips using AFM.
• Identified significant deviations from hemispherical shapes in two tips, attributed to laser absorption or material heterogeneity.
• Demonstrated the capability of AFM to resolve tip geometry down to the atomic level.

Conclusions:

• AFM provides a novel and effective approach for quantitative 3D assessment of atom probe tip shapes.
• Understanding non-hemispherical tip shapes is critical for improving APT reconstruction algorithms and reducing artifacts.
• This method opens new avenues for studying tip evolution and physical processes in APT.