Hole accumulation effect on Laser-assisted field evaporation of insulators

• Published in: Ultramicroscopy Vol. 196; pp. 121 - 128
• Main Author: Xia, Yu
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-01-2019
• Subjects: Atom probe; Field evaporation; Insulators; Laser–matter interaction; Insulators; Atom probe; Field evaporation; Laser–matter interaction
• ISSN: 0304-3991; 1879-2723
• DOI: 10.1016/j.ultramic.2018.10.004

•Surface hole accumulation under high fields and laser pulse illumination is analyzed.•The evaporation field decreases linearly as the surface hole density increases.•Neutral species is easy to evaporate at high laser intensity in atom probe.
Current issues associated with laser-assisted atom probe tomography of insulators are addressed by investigating laser-induced carrier dynamics and field evaporation kinetics. It is shown that for typical insulators with slow carrier recombination compared to the sub-picosecond laser pulse, hole accumulation at the surface plays a key role. By carrying out density functional theory calculations on a MgO cluster, it is found that the critical evaporation field strength decreases linearly as the surface hole density increases. This phenomenon can be explained by the hole-induced electric field. The evaporation of neutral oxygen is enhanced at low electrostatic field strength and high laser intensity. Theoretical insight is also provided for the non-stoichiometry problem in the mass spectra measured in atom probe tomography of compounds.