Improvement of multilayer analyses with a three‐dimensional atom probe

Abstract

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.

Nanoscale Cu/Ta multilayer deposition by co-sputtering on a rotating substrate. Empirical model and experiment

“…This leads to artifacts in the reconstruction, i.e. to erroneous layer thickness, asymmetry of the composition profiles and artificial intermixing due to trajectory overlap [29,30]. Repeating the experiments in cross-section geometry [31,32] might resolve some of these problems, though it is known that this geometry decreases lateral spatial resolution and thus would blur the interface relevant information.…”

Interface sharpening in miscible Ni/Cu multilayers studied by atom probe tomography

“…The remaining difference is within the tolerance limit of measurement. This suggests that the asymmetry in the asprepared state is not a result of a local magnification effect, 18 but reflects the real state of the specimen; most likely a result Ni and Cu atoms are represented by blue (darker) and yellow (brighter) pixels, respectively. The scale bar on the left is 10 nm long.…”

On the influence of the stacking sequence in the nucleation of Cu3Si: Experiment and the testing of nucleation models

“…Cu 3 Si was always formed at the top interface while the bottom interface was characterized by a much thinner silicide layer, if it was present at all. In view of the presence of a defined stoichiometric phase and the correlation to the heat treatment, method-derived artifacts can be completely ruled out in explaining the observed asymmetry between the interfaces [21].…”

“…APT is known for interface-related artifacts (e.g. [21]); however, these are usually also registered as large variations of the atomic density near the interface. We did not observe such an effect (see Fig.…”