Atom Probe Tomography (APT) allows three-dimensional imaging of a tip-shaped specimen, on which it can determine the chemical composition on the atomic scale. Typical APT specimens are sharp needles with apex diameters of about 100 nm or less. To this tip a high voltage is applied so that the surface atoms experience a field that is almost high enough to evaporate them from the surface. An additionally applied high-frequency voltage or laser pulse leads to evaporation of single ions, which are then detected on a 2D detector. This time-resolved and position-sensitive detector analyses the type of the evaporated ions by time-of-flight mass spectroscopy. To avoid lateral movement of tip atoms, the tip has to be cooled down to cryogenic temperatures. Combining the detector information, the specimen can be reconstructed three-dimensionally with almost atomic resolution. Fields of applications include e.g. metals and semiconductors.
Equipment
Local Electrode Atom Probe (LEAP 4000X HR)
- UV-laser or voltage pulsing
- Reflectron for enhanced mass resolution
Laser Assisted Wide Angle Tomographic Atom Probe (LAWATAP)
- Three different laser wavelengths or voltage pulsing
- Field ion microscopy with He or Ne available
Limitations/constraints
- Sample require a SEM compatible sample size for FIB preparation or electropolishing
- Organic materials are challenging and can only be accepted in special cases
- The sample will be prepared as a sharp needle with a diameter of 20 nm to 300 nm
Projects
At KNMFi, a wide variety of research topics is covered. These include alloy design, high temperature composites, intermetallic phases, additive manufacturing, ceramics, high temperature oxidation and corrosion, strengthening mechanisms, high entropy alloys, precipitation processes, phase transformations, hydrogen storage, thin film systems, battery materials, measurement of proteins, superconductors and others. However, KNMFi directs its focus on high temperature materials, including their corrosion resistance.
Collaboration
In the frame of a cooperation it is possible to request instrument time from the Karlsruhe Nano Micro Facility (KNMFi) beantragt werden.