A SOFTWARE PACKAGE FOR ATOM PROBE USERS

Un programme d'acquisition et de traitement de données pour sonde atomique a été développé. Il permet d'obtenir toutes les informations usuellement disponibles à l'issue de calculs ultérieurs pendant la manipulation. Il permet de montrer les spectres de masse, les différents profils ... Il supporte la multi-détection et autorise la désignation et le tri des objets métallurgiques. L'interface utilisateur est particulièrement convivial.An atom probe software package for on line analysis of atom probe data has been developped. It allows to get during the experiments all informations usually obtained with "off -line" treatments, such as mass spectra, multi-element concentration and composition profiles ... It supports the four sector multi-detection we developped. The designation and sorting of various phases is achieved by means of on line graphic methods. The user interface is very convenient

The tomographic atom probe: A quantitative three-dimensional nanoanalytical instrument on an atomic scale

International audienceThe physical architecture and the performance of a quantitative three-dimensional atom probe recently constructed are described. The development of such an instrument relies on the design of a multi-impact position sensitive detector. The multidetection system that we have developed is based on the use of a 10×10 anode array placed behind a two microchannel plate assembly in a chevron arrangement. The spread of charge between the microchannel plate and the multianode is used to derive the position of ion striking the detector. Spatial coordinates can be calculated for multiple and simultaneous time-of-flight events. The procedure used for the derivation of ion positions from charge measurements is given. Specific experiments were carried out in order to determine the intrinsic spatial resolution of the multidetector. Three-dimensional reconstruction of two-phase materials are provided and illustrate the performance of this new apparatus. The reconstructed images demonstrate that atoms are positioned with a precision of a few tenths of a nanometer. The mass resolution M/ΔM (FWHM) of the apparatus is close to 200

The tomographic atom probe: A quantitative three-dimensional nanoanalytical instrument on an atomic scale

International audienceThe physical architecture and the performance of a quantitative three-dimensional atom probe recently constructed are described. The development of such an instrument relies on the design of a multi-impact position sensitive detector. The multidetection system that we have developed is based on the use of a 10×10 anode array placed behind a two microchannel plate assembly in a chevron arrangement. The spread of charge between the microchannel plate and the multianode is used to derive the position of ion striking the detector. Spatial coordinates can be calculated for multiple and simultaneous time-of-flight events. The procedure used for the derivation of ion positions from charge measurements is given. Specific experiments were carried out in order to determine the intrinsic spatial resolution of the multidetector. Three-dimensional reconstruction of two-phase materials are provided and illustrate the performance of this new apparatus. The reconstructed images demonstrate that atoms are positioned with a precision of a few tenths of a nanometer. The mass resolution M/ΔM (FWHM) of the apparatus is close to 200

The Rouen energy-compensated atom probe

International audienceThe energy-compensated atom probe developed in Rouen is based on the original instrument built in 1978. Since, several improvements were added. Some extensions, among which a Poschenrieder-type energy compensator and a spatial resolution controlling diaphragm, have been adapted to it. The main characteristics of this instrument are presented. \textcopyright 1994

Performance of the multiple events position sensitive detector used in the tomographic atom probe

International audienceThe tomographic atom probe (TAP) is the first 3D atom probe based around the use of a parallel position encoding system. This contribution will be focused on the implementation and the study of the TAP position sensitive detector. In the first part, it will be shown why this detector necessarily has to be sensitive to simultaneous events and the detector principle will be described. Then performance and limitations of the TAP will be discussed and related to the detector performance itself. Critical points such as spatial resolution, mass resolution or detection efficiency will be quantified. \textcopyright 1995

Performance of the multiple events position sensitive detector used in the tomographic atom probe

International audienceThe tomographic atom probe (TAP) is the first 3D atom probe based around the use of a parallel position encoding system. This contribution will be focused on the implementation and the study of the TAP position sensitive detector. In the first part, it will be shown why this detector necessarily has to be sensitive to simultaneous events and the detector principle will be described. Then performance and limitations of the TAP will be discussed and related to the detector performance itself. Critical points such as spatial resolution, mass resolution or detection efficiency will be quantified. \textcopyright 1995

The Rouen energy-compensated atom probe

International audienceThe energy-compensated atom probe developed in Rouen is based on the original instrument built in 1978. Since, several improvements were added. Some extensions, among which a Poschenrieder-type energy compensator and a spatial resolution controlling diaphragm, have been adapted to it. The main characteristics of this instrument are presented. \textcopyright 1994

An atom probe for three-dimensional tomography

International audienceELECTRIC-field-induced evaporation of ions from a needle-like surface, and their subsequent identification by time-of-flight mass spectrometry, forms the basis of the atom-probe technique1. This has proved to be a powerful analytical tool2,3, permitting the quantitative determination of material composition in a small selected region of the surface (depths of 1–5 nm) with single-layer resolution. Positional information for the atoms within each layer is lost, however. In contrast, the field-ion microscope3 provides atomic-resolution images of surfaces, but without information about the nature of the atoms. Several attempts have been made to combine these two techniques by extending the time-of-flight measurement into two dimensions, but they have been limited by their inability to identify all chemical species4 or to combine spatial and temporal information for multiple events5, especially for ions with very similar mass-to-charge ratios6. Here we make use of a recently developed7 multiple-impact detector to construct a position-sensitive atom probe with sufficiently high temporal resolution (of the order of 10 ns) to avoid these earlier problems; thus, reliable composition and position data can be obtained at the same time. We illustrate the performance of this instrument by imaging the three-dimensional distribution of chemical heterogeneities in a nickel-based alloy on a near-atomic scale

In-Situ Survey System of Resistive and Thermoelectric Properties of Either Pure or Mixed Materials in Thin Films Evaporated Under Ultra High Vacuum

The study of thermoelectric and resistive in situ behaviours depending on temperature for thin films of either pure or composite materials obtained under ultra-high vacuum, is very interesting, since they can be used as strain gauges or superficial resistances. However, studies become particularly difficult when the measurements generate very low-level electrical signals. Indeed, these turn out to be hardly detectable because of the perturbations brought by the experimental environment. The apparatus described below allows for the measurement of resistance with a relative uncertainty of $2\times10^{-4}$, resistance variation with an absolute uncertainty of 2 m$\Omega$ and thermoelectric e.m.f. of about 2 $\mu$V. Films studied in the laboratory generally exhibit resistances lower than 100 $\Omega$ and resistance variations due to temperature variations of about a few ohms. So this device has sufficient technical characteristics for our studies. It can be connected to a PC, which allows for easy data collection and treatment.L'étude des comportements résistif et thermoélectrique in situ en fonction de la température de couches minces de matériaux simples ou composites obtenus en milieu raréfié s'avére intéressante en vue d'applications comme jauge de contrainte ou résistance superficielle mais particulièrement délicate lorsque les mesures donnent naissance à des signaux électriques de très faible amplitude. Ces derniers deviennent en effet difficilement décelables en raison des perturbations apportées par l'environnement expérimental. Le système qui est décrit ici permet de mesurer des résistances avec une certitude relative de $2\times10^{-4}$ et d'apprécier des variations de résistance de 2 m$\Omega$ et des f.e.m. thermoélectriques de l'ordre de 2 $\mu$V. Les couches étudiées au laboratoire présentent généralement des résistances inférieures à 100 $\Omega$ et des variations de résistance dues aux variations de température de l'ordre de quelques $\Omega$. Le dispositif de mesure présente donc des caractéristiques techniques suffisantes pour nos études. Connecté à un PC il permet l'acquisition des données et un traitement rapide