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Local magnification effects related to the presence of a second phase in three-dimensional atom probe have been investigated using a simulation of ion trajectories from the analyzed sample surface. Spherical precipitates containing only B atoms embedded in pure A solid solution were considered. The magnification was found to vary drastically from 0.5 to 2.0 times when the evaporation field of B (EB) was varied from 1.15 EA to 0.85 EA. The trajectories were found to overlap over distances close to 1 nm only when the reduced evaporation field (εB=EB/EA) is outside of a gap ranging from 0.9 to 1.1. Simulations indicate that the “measured” composition in the inner core of precipitates is not biased in this gap. This is also the case for particles which have a diameter larger than a critical value of 2 nm.

A tomographic atom probe (TAP) in which the atoms are field evaporated by means of femtosecond laser pulses has been designed. It is shown that the field evaporation is assisted by the laser field enhanced by the subwavelength dimensions of the specimen without any significant heating of the specimen. In addition, as compared with the conventional TAP, due to the very short duration of laser pulses, no spread in the energy of emitted ions is observed, leading to a very high mass resolution in a straight TAP in a wide angle configuration. At last, laser pulses can be used to bring the intense electric field required for the field evaporation on poor conductive materials such as intrinsic Si at low temperature. In this article, the performance of the laser TAP is described and illustrated through the investigation of metals, oxides, and silicon materials.

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