[labnetwork] Johnson Matthey H2 Purifier

[Collins, Deon]

If this was improperly shut down(not allowed to cool off and turned off) the palladium plates can crack and cause gasses to leak through the material.

Deon D. Collins

FACILITY MANAGER
Holonyak Lab
University of Illinois at Urbana-Champaign
208 N Wright St Rm. 248 | 2250
Urbana, IL 61801
217-300-7531 | deonc69 at illinois.edu<mailto:deonc69 at illinois.edu>


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From: labnetwork <labnetwork-bounces at mtl.mit.edu> On Behalf Of Rachel Schoeppner
Sent: Wednesday, October 20, 2021 10:51 AM
To: labnetwork at mtl.mit.edu
Cc: Lillian Hughes <lbhughes at ucsb.edu>
Subject: [labnetwork] Johnson Matthey H2 Purifier

Good Morning,


We have a Johnson Matthey HP-25 hydrogen purifier that we suspect is not functioning properly. In its idle state it is kept under low UHP N2 flow, and we think that some of this is getting through the purifier into the lines of our CVD. At the start of deposition when we start H2 flow and ignite the initial plasma we see an unexpected peak in nitrogen (verified both in the emission spectrum of the plasma as well as nitrogen that is incorporated in the epitaxial film as measured with SIMS). When we flow the hydrogen gas through the growth chamber for ~20 min before deposition, no nitrogen peak is observed, suggesting that it is coming in as an initial “plug” through the purifier at the very beginning that can be flushed through. There is also a low amount of background nitrogen throughout the deposition (this could be an impurity in the methane, but I am not sure how likely that is).

We have leak checked the line running from the purifier to the CVD chamber and cannot detect any leaks that might be causing the initial nitrogen spike.

We are wondering if anyone has experience with these purifiers or ideas on how to diagnose their proper functionality. If it is letting unwanted species through, then what would be our options for fixing or replacing it?


Thank you!


Rachel

—

Rachel Schoeppner, Ph.D

Nanostructure Cleanroom Facility Manager
California NanoSystems Institute (CNSI)
University of California, Santa Barbara
rlschoeppner at ucsb.edu<mailto:rlschoeppner at ucsb.edu>
rachel at cnsi.ucsb.edu<mailto:rachel at cnsi.ucsb.edu>
(805)893-2296










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