Design of a Wide Angle Laser Assited Tomographic Atom Probe

A wide angle tomographic atom probe has been designed in which the field evaporation of atoms is assisted by subpicosecond laser pulses. It has been shown that the field evaporation is due to the generation of a THz pulse due to the rectification of the optical field at the specimen surface. The very short duration of the pulsed field (a few hundred fs) offers several advantages as compared to conventional pulsing method. First, it makes possible to bring intense electric field at the surface of resistive specimens opening the field of application of the atom probe tomography to new materials such as oxydes or semiconductors. Second, a high mass resolution can be achieved in a straight type configuration allowing to fully open the field of view in order to collect the whole amount of data available from field emitter specimens. Third, because the pulse duration is below the phonon vibration time, no cycling stress in applied on the specimen during the analysis. As a result, very fragile materials can be investigated by APT. In addition, this makes possible to investigate materials at very low temperature making the spatial resolution better. In this contribution, the design of the LaWaTAP will be presented and the performance of the instrument discussed through some applications to metals, oxydes and semiconductors