Flash electropolishing for TEM: Reducing FIB-induced defects in tungsten with protocols for new materials

Area of Science:

• Materials Science
• Microscopy
• Nuclear Engineering

Background:

• Focused ion beam (FIB) milling is standard for transmission electron microscopy (TEM) specimen preparation.
• FIB-induced damage, especially 'black spot' defects in tungsten, hinders accurate microstructural characterization, particularly in radiation effects studies.
• These defects can be mistaken for fine irradiation-induced loops.

Purpose of the Study:

• To evaluate flash electropolishing as a post-FIB treatment for minimizing preparation artifacts in tungsten TEM specimens.
• To systematically assess key processing parameters for flash electropolishing.
• To establish criteria for reliable microstructural analysis of FIB-prepared tungsten.

Main Methods:

• Systematic evaluation of flash electropolishing on non-, ion-, and neutron-irradiated tungsten materials.
• Comparison with conventional FIB and plasma-FIB preparation methods (Ga, Ar, Xe ion cleaning).
• Analysis of processing parameters: lamella thickness, voltage, duration, electrolyte chemistry, cathode geometry.

Main Results:

• Flash electropolishing effectively removes FIB-damaged layers and 'black spot' defects.
• Reliable observation of irradiation-induced dislocation structures is enabled.
• Clear criteria for implementing flash electropolishing were established.

Conclusions:

• Flash electropolishing is a viable, artefact-controlled method for TEM specimen preparation of tungsten alloys.
• The developed protocol enhances the accuracy of radiation-damage characterization.
• The methodology is adaptable for other material systems.