Field evaporation simulation for high precision atom probe tomography. Effect of field evaporation and surface diffusion of iron and copper on field evaporation

Atom probe tomography (APT) is a very powerful tool being able to investigate atomic positions and chemical compositions of materials with sub nanometer resolution. In APT, atoms are field-evaporated by applying a high electric field to a needle-like specimen. At the precipitates and interfaces, due to the difference in the electric field evaporation of the elements, the local magnification effect causes artifacts. Surface diffusion and reconstruction of atoms during field evaporation also causes artifacts. The difference of the electric field evaporation by the elements can be obtained by first-principles calculation. We performed first-principles calculation of surface diffusion and electric field evaporation where electric field is applied on Fe or Cu adsorbed on BCC Fe(001) and Cu adsorbed on BCC Cu(001). The field evaporation of Fe obtained by the calculation was in good agreement with the experimental value. The surface migration calculations of Fe and Cu on Fe (001) were performed. As the electric field increased, the activation energy of diffusion decreased and the activation energy of the electric field of 28 V/nm is about 40% of that of 0 V/nm. (author)