Influence of UO₂ crystal orientation on laser ablation performance

Area of Science:

• Materials Science
• Analytical Chemistry
• Geochemistry

Background:

• Crystallographic orientation affects surface analysis techniques like SIMS and FIB.
• Laser ablation (LA) is a key sampling method for ICP-MS.
• Understanding LA challenges with crystalline materials is crucial for accurate analysis.

Purpose of the Study:

• To investigate the challenges of laser ablation (LA) for inductively coupled plasma-mass spectrometry (ICP-MS) concerning crystallographic orientation.
• To study laser-matter interaction with uranium dioxide (UO2) single crystals of varying orientations.
• To determine the impact of laser fluence and cumulative effects on ablation characteristics.

Main Methods:

• Production and characterization of UO2 single crystals with different orientations and polycrystalline UO2.
• Utilized a nanosecond (ns) laser ablation system with controlled single-shot fluence and continuous firing.
• Analyzed crater depth, surface roughness (confocal laser scanning profilometry), and ejected particle morphology (SEM).

Main Results:

• Laser ablation rates were highly reproducible and independent of UO2 crystal orientation.
• Ablation rate and crater depth decreased exponentially with increasing single-shot fluence.
• Surface roughness increased with cumulative fluence; crater bottom morphology was limited by molten UO2 re-solidification.

Conclusions:

• Laser ablation sampling for ICP-MS is robust regarding crystallographic orientation for UO2.
• Depth resolution in LA-ICP-MS is primarily limited by the re-solidification of molten material, creating a convex meniscus.
• SEM analysis revealed distinct ejected particle types, offering insights into laser-UO2 interactions.