i have problem that the plasma ignite under the bottom electrode of the chamber (where the subtrate lie ) instead of ignite between the two electrodes . during CNTS growth using PECVD (easy tube 2000 device )
what could be the reason of that ? here are the process condition in the picture
If your plasma is in the wrong place, I recommend checking your setup for short circuits or broken contacts before you try another ignition. If one of the electrodes is on the mass or one voltage ends up in the wrong place because the final electrode is no longer in contact with the supply, that could in the best case be harmful for your other equiqment and in the worst case dangerous for people.
The pressure is too high, lower the pressure under 1 Torr (10^-2 to 1 Torr). Choose an RF power of 3 to 5 W/ cm^2 . Then lower the voltage, and verify that the bottom electrode is at the ground potential.
Referring to Valentin: There could be some dirt causing the misplaced plasma either by evaporation or as the starting point of an arc. If so, inspecting, maybe cleaning the surfaces in question should help.
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