Optimized single-beam modulation argon ion milling for TEM cross-sectional specimens of nanostructured interfaces

High-quality transmission electron microscopy (TEM) specimens are critical for high-resolution imaging and conducting electron energy loss spectroscopy (EELS) analysis. However, fabricating cross-sectional TEM specimens with large, thin, and low-damage regions remains challenging, particularly with conventional mechanical polishing and Ar⁺ ion-beam milling methods. Here, we propose an optimised method based on Ar⁺ ion-beam milling that precisely maintains the consistency of the sample's thickness after mechanical polishing and fine-tunes Ar⁺ ion-beam milling parameters. Appropriately chosen milling parameters through real-time monitoring minimise the damaged layer's thickness, while optimised parameters reduce the redeposition of sputtered material. Applied to interfaces such as those between aligned carbon nanotube arrays (A-CNTs) and gate dielectrics key to next-generation nanoelectronics, we achieved samples with a 30 µm wide thin region, the thinnest area reaching 15 nm, preserving structural integrity and yielding a well-defined CNT-HfO₂ interface. Notably, redeposition was reduced from 44.4% to 6.6%, and single-beam modulation enabled these extensive thin regions, outperforming dual-beam methods.