Correlative transmission electron microscopy and atom probe tomography on field evaporation mechanism of a bulk LaAlO3 oxide

Abstract

Laser-assisted atom probe tomography (APT) has commonly been performed to determine the composition of non-conductive oxide materials at the atomic scale. However, its field evaporation mechanism is still insufficiently understood due to the complexity of laser-matter interaction on the surface of oxide tips. To understand the physical mechanism underlying laser-assisted field evaporation in a bulk oxide LaAlO3 (LAO), we conducted an interrupted experiment that combines transmission electron microscopy with APT. This correlated technique visualized the shape evolution of LAO tips during laser-assisted APT. We demonstrated that the evaporation field strength of the tips depends on the APT experimental parameters including applied laser energy and base temperature. An increase in the laser energy led to a reduction in the field evaporation strength of the tips and the formation of apex asymmetries on the tips, thereby considerably influencing the mass resolution of the technique. Moreover, an increase in the base temperature caused a slight decrease in the evaporation strength but did not significantly affect the mass-resolving ability of APT. The results discussed in this work suggest that it is the employed laser energy that primarily affects APT's resolving capability and the field evaporation strength of oxide materials. Our interrupted technique provides fundamental insight into the field evaporation sequences of LAO oxide tips under laser illumination, which can be feasibly applied to the study of various metallic and oxide materials.