Origin and control of annealing-induced domain-wall features

Determine the origin of the thin, sharp walls or domain-wall features that appear in Ta(C,N) film surfaces after high-temperature face-to-face annealing, and establish processing conditions that control these features.

Background

Atomic-force microscopy revealed thin, sharp walls of material as bright white streaks in the 1 μm² surface scans of the annealed Ta(C,N) films. These features appeared across the investigated annealing conditions, whereas other growth and annealing conditions did not produce them.

The authors identify the origin of the features as unresolved and suggest that they may be related to strain and relaxation during extreme-temperature annealing. Understanding and controlling them is relevant because surface morphology, including step-and-terrace structure, affects the suitability of Ta(C,N) virtual substrates for AlGaN heteroepitaxy.

References

The origin of these features is unknown but likely related to strain and relaxation in the extreme temperature annealing process. We note that other growth and annealing conditions do not contain these domain walls, and further work is ongoing to understand and control these features.

— Face-to-face anneal temperature controls lattice parameter in Ta(C,N) virtual substrates for AlGaN power electronics  (2609.24893 - Zahn et al., 21 Sep 2026) in Section 3.2, Surface Morphology