The spatial resolution of 3D atom probe in the investigation of single-phase materials

The resolution of three-dimensional atom probe (3DAP) is known to be mainly controlled by the aberrations of the ion trajectories near the surface of the specimen. A model has been developed to compute the ion trajectories in 3D near a sharp hemispherical electrode defined at the atomic scale. Simulations were applied on one-phase binary alloys. The influence of the evaporation fields of chemical species is studied. Simulated desorption images are consistent with experiments in both ordered alloys and random solid solution. An extra loss in the lateral resolution is observed in disordered alloys as compared to pure metals. The predicted order of evaporation provided by this model is in excellent agreement with experiments. The stacking sequence of atomic planes reconstructed from simulated data is shown to be disturbed in a similar way as observed in real experiments with 3DAP.