APT (Atom Probe Tomography) is a destructive 3D characterization technique that provides atom-by-atom chemical analysis — field-evaporating individual atoms from a needle-shaped specimen and detecting their mass-to-charge ratio to reconstruct atomic-scale 3D composition maps.

How Does APT Work?

• Specimen: FIB-prepared needle with tip radius < 100 nm.
• Field Evaporation: High voltage (+ laser pulse) evaporates surface atoms one by one.
• Time-of-Flight: Mass-to-charge ratio identifies the chemical species.
• Position-Sensitive Detector: Hit position + evaporation sequence reconstructs 3D positions.

Why It Matters

• Atomic Resolution: The only technique that provides both 3D position and chemical identity of individual atoms.
• Dopant Distribution: Maps individual dopant atoms in a semiconductor volume — statistical fluctuation analysis.
• Interface Analysis: Characterizes abrupt interfaces, grain boundary segregation, and clustering at the atomic scale.

APT is the atom census — counting, identifying, and locating every single atom in a nanoscale semiconductor volume.