Laser ablation sample preparation for atom probe tomography and transmission electron microscopy

Abstract

Laser ablation is capable of removing large volumes of material with micron scale precision at very high speeds. This makes it an ideal tool for the initial stage of preparation of samples for atom probe and electron microscopy studies. However, the thermal nature of the laser ablation process is such that thermal and mechanical damage is induced in the samples in the form of zones of recrystallisation and stress induced deformation. For the analysis of nanometer-sized samples, such as those required for atom probe tomography and transmission electron microscopy, it is necessary to ensure that any damage induced during sample preparation will not introduce artefacts and that specimens are representative of the microstructure of the bulk sample. Here we have undertaken an analysis of the damage caused during sample preparation through a study of pure aluminium and phosphorous doped silicon wafers. Our findings indicate that recrystallisation and stress induced misorientations occur in pure aluminium at the micron scale, however, no detectable damage is observed in the silicon sample.

Keywords: Atom probe tomography; Damage characterisation; Laser ablation; Pure aluminium; Silicon wafers; Transmission electron microscopy.