Improvement of multilayer analyses with a three-dimensional atom probe

Owing to their giant magnetoresistance properties, multilayer thin-film materials are widely used in information storage technology. However, because this magnetic behaviour is highly sensitive to interface roughness and diffusivity on a subnanometre scale, the structural characterization of these materials with high spatial resolution is of fundamental importance. The three-dimensional atom probe is one of the instruments that theoretically can provide chemical analyses in three dimensions with the highest spatial resolution. However, because three-dimensional reconstructions can be subject to strong artefacts due to trajectory aberrations, it is important to combine experimental analyses with theoretical investigations of the evaporation and reconstruction process in order to obtain the most accurate data on interface structure. In this paper, a simulation model is used in order to compute the ion trajectories close to a field emitter. The model is modified to take into account the unique morphology of the multilayer thin-film structure. This model gives a sound interpretation of the three-dimensional atom probe images of multilayer thin films. The three-dimensional atom probe reconstructions of NiFe/FeCo/Cu multilayer structures are found to be degraded by strong artefacts owing to the difference in evaporation field between the FeCo layer and the Cu layer. By using simulation, these aberration effects are interpreted as errors in the calculation of the z-dimension within three-dimensional images. A correction procedure has been developed to improve the reconstruction of multilayer thin films in the three-dimensional atom probe. Copyright (C) 2004 John Wiley Sons, Ltd.