Field evaporation behavior in [0 0 1] FePt thin films

Though the atom probe has provided unprecedented atomic identification and spatial imaging capability, the basic reconstruction assumption of a smooth hemispherical tip shape creates significant challenges in yielding high fidelity chemical information for atomic species with extreme differences in fields required for field evaporation. In the present study, the evaporation behavior and accompanying artifacts are examined for the super-cell lattice structure of L10 FePt, where alternating Fe and Pt planes exist in the [0 0 1] orientation. Elemental Fe and Pt have significant differences in field strengths providing a candidate system to quantify these issues. Though alloys can result in changes in the elemental field strength, the intrinsic nature of elemental planes in [0 0 1] L10 provides a system to determine to what extent basic assumptions of elemental field strengths can break down in understanding reconstruction artifacts in this intermetallic alloy. The reconstruction of field evaporation experiments has shown depletion of Fe at the (0 0 2) pole and zone axes. Compositional profiles revealed an increase in Fe and atom count moving outward from the pole. The depletion at the low indexed pole and zone axes was determined to be the result of local magnification and electrostatic effects. The experimental results are compared to an electrostatic simulation model.

Research highlights
► Field evaporation behavior of the ordered L10 FePt was investigated using APT.
► It was found that close to the (0 0 2) pole the number density of Fe ions detected was significantly lowered because of ion trajectory aberration effects.
► Simulations incorporating a face center cubic structure have qualitatively reproduced the experimental findings without the inclusion of a binding term or thermal effects.
► Both experimental and simulation results have shown that the difference in evaporation field between the two components of the alloy contributed to the trajectory aberrations near the (0 0 2) pole and zone axes.