Ultrafast laser-triggered field ion emission from semiconductor tip

International audienceWe study experimentally and theoretically the controlled field evaporation of single atoms from a semiconductor surface by ultrafast laser-assisted atom probe tomography. The conventional physical mechanisms of field evaporation cannot explain the experimental results recently reported for such materials. A new model is presented in which the positive dc field leads to band bending with a high density of laser-generated holes near the surface of the sample. The laser energy absorption by these holes and the subsequent energy transfer to the lattice considerably increase the tip temperature. We show that this heating plays an important role in the field ion emission process. In addition, experiments are carried out for germanium and silicon tips to check the role of the dc field in the absorption processes, as well as the heating of the tip and the following evaporation. Good agreement between the predictions of our model and the experimental data is found

Effects of incidence angles of ions on the mass resolution of an energy compensated 3D atom probe

Abstract We have used a first-order reflectron lens in an optical tomographic atom probe in order to improve the mass resolution. Calculations have been performed to determine the effect of second-order errors in ion energy and incidence angle on the performance of the lens. By applying a correction procedure based on the results of these calculations, we have been able to improve experimental mass resolution by 30%.

A Photonic Atom Probe coupling 3D Atomic Scale Analysis with in situ Photoluminescence Spectroscopy

Laser enhanced field evaporation of surface atoms in Laser-assisted Atom Probe Tomography (La-APT) can simultaneously excite phtotoluminescence in semiconductor or insulating specimens. An atom probe equipped with appropriate focalization and collection optics has been coupled with an in-situ micro-Photoluminescence ({\mu}PL) bench that can be operated during APT analysis. The Photonic Atom Probe instrument we have developped operates at frequencies up to 500 kHz and is controlled by 150 fs laser pulses tunable in energy in a large spectral range (spanning from deep UV to near IR). Micro-PL spectroscopy is performed using a 320 mm focal length spectrometer equipped with a CCD camera for time-integrated and with a streak camera for time-resolved acquisitions. An exemple of application of this instrument on a multi-quantum well oxide heterostructure sample illustrates the potential of this new generation of tomographic atom probe.Comment: 22 pages, 4 figures. The following article has been accepted by the Review of Scientific Instruments. After it is published, it will be found at https://publishing.aip.org/resources/librarians/products/journals

Role of the atom probe in the study of nickel-based superalloys

International audienceNanostructural features of nickel-based superalloys as revealed by Field-Ion Microscopy, Atom Probe (APFIM), and 3D Atom Probe are reviewed. The unique and original information provided by these techniques is discussed on the basis of an extended and almost exhaustive analysis of bibliography over the last 30 years. Atom Probe techniques are shown to be able to measure the composition of tiny γ′ precipitates, a few nanometer in size, to detect ordering or subtle clustering effects within the γ solid solution or γ′ particles. Plane-by-plane analysis of (001) planes of the γ′ phase makes it possible to estimate the degree of order as well as the preferential sites of various addition elements included in superalloys. Due to its ultrahigh depth resolution, the microchemistry of interfaces and grain boundaries can also be characterized on an atomic scale. Most salient results will be reviewed, and the specific role of 3D APFIM will be highlighted with selected examples

Contribution of 3D atom probe to the understanding of plane-by-plane AP analyses data: application to the study of ordering in Cu3Au

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Contribution of 3D atom probe to the understanding of plane-by-plane AP analyses data: application to the study of ordering in Cu3Au

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Antenna effect in laser assisted atom probe tomography: How the field emitter aspect ratio can enhance atomic scale imaging

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Role of the atom probe in the study of nickel-based superalloys

International audienceNanostructural features of nickel-based superalloys as revealed by Field-Ion Microscopy, Atom Probe (APFIM), and 3D Atom Probe are reviewed. The unique and original information provided by these techniques is discussed on the basis of an extended and almost exhaustive analysis of bibliography over the last 30 years. Atom Probe techniques are shown to be able to measure the composition of tiny γ′ precipitates, a few nanometer in size, to detect ordering or subtle clustering effects within the γ solid solution or γ′ particles. Plane-by-plane analysis of (001) planes of the γ′ phase makes it possible to estimate the degree of order as well as the preferential sites of various addition elements included in superalloys. Due to its ultrahigh depth resolution, the microchemistry of interfaces and grain boundaries can also be characterized on an atomic scale. Most salient results will be reviewed, and the specific role of 3D APFIM will be highlighted with selected examples

A general protocol for the reconstruction of 3D atom probe data

International audienceData collected with 3D atom probes have to be carefully analysed in order to give reliable composition data precisely positioned in the probed volume. Indeed, the large analysed surfaces of 3D atom probes require the development of reconstruction methods taking into account the tip geometry. When the analysis does not take place in the close vicinity of the tip axis, the analysis direction is no longer perpendicular to the evaporated surface. The influence of this effect on the local magnification and atom positioning must be taken into account. The proposed procedure will be validated by studying the effects of calculations on a long-range-ordered phase. \textcopyright 1995

Femtosecond field ion emission by surface optical rectification

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