Atom Probe Tomography (APT)

Atom Probe Tomography (APT) is an advanced technique used to obtain 3D atomic-scale compositional information in solids, ranging from metals to semiconductors or insulators. The APT instrument “peels” off individual atoms from a needle-shaped specimen with the help of an electric field or a laser pulse. These atoms are then detected and identified by their time of flight, allowing a detailed 3D reconstruction of the material at the atomic level.

In Atom Probe Tomography, the process begins by sharpening the specimen into a needle shape, typically to a tip diameter of about 100 nm, using a Focused Ion Beam-Scanning Electron Microscope (FIB-SEM) for precise preparation. Next, a high electric field or a laser pulse is applied to the tip, causing individual atoms to evaporate one by one from the apex of the tip. As each atom evaporates, it is directed toward a detector where its arrival time is recorded, allowing the identification of the atom type based on its mass-to-charge ratio. By repeating this process for millions of atoms, APT creates a detailed 3D atomic map of the sample, revealing its compositional and structural characteristics at nearly atomic resolution.

Using a Vacuum Cryo Transfer Module (VCTM) to transfer a sample between an Atom Probe Tomography system and a Focused Ion Beam-Scanning Electron Microscope (FIB-SEM) offers significant advantages, especially when working with sensitive or reactive samples. When the VCTM is employed, it enables the sample to be transferred in a vacuum and at cryogenic temperatures, which helps prevent contamination, oxidation, or structural changes that could occur at room temperature or in ambient conditions.