Laser pulsing of field evaporation in atom probe tomography

The processes by which field evaporation in an atom probe is momentarily stimulated by impingement of a laser beam on a specimen are considered. For metals, the dominant and perhaps only sensible mechanism is energy absorption leading to thermal pulsing, which has been well established. The energy of a laser beam is absorbed in a thin optical skin depth on the surface of the specimen. For materials with a band gap such as semiconductors and dielectrics, it is found that energy absorption in a thin surface layer dominates the process as well and leads to similar thermal pulsing. The relative amount of surface absorption versus volume absorption can strongly influence the heat flow and therefore the mass spectrum of the specimen. Thus it appears for very different reasons that all materials behave similarly in response to laser pulsing in atom probe tomography.