As promised yesterday, another photo of an argon-plasma. You can see the new electrode above, with different-sized holes in it. Each hole is a hollow cathode, and lights up under the right conditions, producing a much denser plasma than a flat electrode would. I also wanted to show you what happens if I increase neutral pressure and power, but then my flowmeter died - no more argon until I change it.
Dear Boris,
ReplyDeleteI am a graduate student who is interested in using hollow cathode construction for CVD process. I would appreciate if you could let me know how you designed one.
Hi som, basically all you need to do is have a hole that is larger than twice the sheath-width of your plasma. You have quite a bit of leeway, but plasma chemistry and electrode material will influence that. Lieberman (Principles of Plasma Discharges) has a short chapter on DC hollow cathodes. If you are interested in RF hollow cathodes I would suggest this paper by L.Bárdoš https://doi.org/10.1016/S0257-8972(96)03056-3
ReplyDeleteIf you have easy access to your reactor, just stick some plates with different sized holes in and play with pressure and RF power. Best of luck!
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