I'm trying to inject nitrogen into some of the PVD materials I'm growing, and ammonia added during deposition may be able to accomplish this
Dear Sir,
we have worked with ammonia in a 3 step CVD process to growth epitaxial monolayer of hexagonal boron nitride (i.e., "boronitrene" or "white graphene").
Maybe this publications helps:
F. Mueller et al., PHYSICAL REVIEW B 82, 075405 (2010)
Sincerely, FM
Thank you Frank, I'm trying to locate the publication now. I am concerned that caustic chemicals in an ebeam will eat the o-rings and/or cause other problems, whereas a CVD system is designed to handle reactions and so it's less of a concern with the equipment. I would like to know if someone else has done it so that I have some measure of assurance that it is safe for people and equipment.
Dear Michael,
I don´t know the setup, but if only the o-rings are the problem, ask your workshop
to make rings from stainless steel (or other metals) of nearly the same geometry.
For sealing, just use some thin wires from indium or gold on the end faces.
Or in general, think of replacing your viton sealed Klein fanges by conflat
flanges sealed with copper rings.
Regards, FM
Is the system generally designed to run with a background pressure? I'd not be worried with the chamber. Ammonia is volatile, so it can be pumped out; the ammonia pressure in your chamber is very, very low; it is reasonably inert in gaseous form. Water is more reactive and more problematic!
Edit: Just make sure that your pump exhaust goes outside. Ammonia is toxic, do you have a setup that is safe with toxic gasses?
Hi Dieter,
It's a cryopump, so does not exhaust until regenerated, which is once per year. There was mention of the ammonia attacking the seals. We operate at 5x10^-7 Torr, so very little background pressure.
What is the material of the seals? Metal seals and polymer seals should both not be a problem at low ammonia pressure. It may just diffuse through polymer seals. Dry gaseous ammonia is not chemically aggressive. It only becomes an issue in terms of corrosion together with liquid water. You are not going to run it at atmospheric pressure, right?
Is it an MBE machine and you want to use a gas jet? Or is it an ordinary evaporator and you want to put the chamber to a certain pressure?
If you use cryopumps I guess that your setup is not designed to run with a significant gas filling in the chamber, or is it? What NH3 pressure do you want to get? Was the 5x10^7 torr the intended ammonia pressure?
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