Method and apparatus for atomic probe tomography

A method of performing atomic probe tomography using an apparatus, wherein the apparatus comprises:

• a vacuum chamber;
• a sample holder for holding a sample inside the vacuum chamber, the sample having a free-standing tip;
• a 2-dimensional APT detector for detecting atoms evaporated from the tip;
• a voltage source for applying a voltage difference between the sample and the APT detector;
• a beam nozzle for delivering a coherent photon beam into the vacuum chamber, the beam being directed at the tip and having a beam energy in the soft X-ray energy range;
• a 2-dimensional photon detector positioned to detect photons, wherein the beam nozzle is configured to permit or enable the scanning by the soft X-ray beam of the tip;
• and
• a data processing tool configured to derive a 2-dimensional or a 3-dimensional image of the tip area, and wherein the method comprises:
• mounting the sample in the sample holder in the vacuum chamber;
• under vacuum, evaporating atoms from the tip and projecting the atoms on the APT detector under the influence of the voltage difference applied between the sample and the APT detector;
• reconstructing the material of the tip on the basis of the detected atoms;
• and
• further comprising the following, executed repeatedly during the above evaporation and reconstruction:
• scanning a number of adjacent and overlapping areas of the tip with the coherent photon beam;
• detecting with the photon detector, interference patterns generated by the detected photons from the soft X-ray beam which have interacted with the tip, originating from the adjacent areas;
• and
• determining the image of the tip area by applying a ptychography or ankylography algorithm to the interference patterns.