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Your PBN Crucible's Surface Roughness
Your PBN Crucible's Surface Roughness
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Guest
Guest
Sep 24, 2026
11:46 PM
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Something that changed how I specify PBN crucibles: inner surface roughness directly correlates with epitaxial defect density.
Patent data from MBE crucible development tells the story:
Mirror-polished inner surfaces (Ra ? 0.1 µm): 10 defects/cm²
Rougher surfaces: 35 defects/cm²
The mechanism is simple. Molten source material adheres to pits and irregularities. Those droplets spit or shed particulates that end up in your film.
Here's the part most people miss: the graphite mandrel's surface roughness determines the PBN's growth-plane roughness. You can't polish your way out of a bad mandrel. If you specify Ra ? 2 µm on the mandrel, you get a dramatically smoother crucible. After deposition, an 800°C air bake removes carbon residue, and optional mirror-polishing pushes performance further.
If you're buying PBN, ask your supplier about mandrel finish. It matters more than most spec sheets admit.
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Anonymous
Guest
Sep 25, 2026
2:37 AM
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Jason Mills
Guest
Sep 25, 2026
10:21 PM
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Surface roughness is one of those details that quietly determines how well a PBN crucible performs, so this is a genuinely useful topic to dig into. Even small variations in finish can affect thermal contact, contamination risk, and how cleanly materials release during high-temperature processes. It is a good reminder that performance in demanding applications often comes down to precision at the microscopic level, and PBN ceramics are trusted precisely because they deliver that kind of consistency and purity. Thanks for covering this.
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