<div><div dir="auto">Hi Rachel,</div><div dir="auto">Palladium cell purifiers work great but are prone to failure due to the brittle nature of the Pd membrane.</div><div dir="auto">If they are not properly purged before the cell cools down, such as in a loss of power, the membrane will crack due to Hydrogen getting trapped inside.</div></div><div><div dir="auto">A quick function test can be done by switching the upstream H2 supply over to full Nitrogen (or other inert gas) while hot. The purified H2 existing in the pressurized line will eventually back-diffuse through the hot cell and get carried away by the purge bleed flow. Eventually, it will pull a vacuum on the H2 downstream line (assuming it is leak right and there are no downstream valves open.</div><div dir="auto">If it doesn’t pull a vacuum, the membrane is dead.</div><div dir="auto">Hope this helps!</div><div dir="auto">Brian</div><div dir="auto"><br></div><div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Oct 20, 2021 at 12:09 PM Rachel Schoeppner <<a href="mailto:rlschoeppner@ucsb.edu" target="_blank">rlschoeppner@ucsb.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;padding-left:1ex;border-left-color:rgb(204,204,204)"><div dir="auto"><div dir="ltr">Good Morning, <div><br></div><div><br></div><div><div>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). </div><div><br></div><div>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.</div><div><br></div><div>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?</div><div><br></div><div><br></div><div>Thank you!</div><div><br></div><div><br></div><div>Rachel</div><div>
<div dir="auto" style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;word-wrap:break-word;line-break:after-white-space;color:rgb(0,0,0)"><div dir="auto" style="letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;word-wrap:break-word;line-break:after-white-space;font-family:Helvetica;color:rgb(0,0,0)"><div dir="auto" style="letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;word-wrap:break-word;line-break:after-white-space;font-family:Helvetica;color:rgb(0,0,0)"><div dir="auto" style="letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;word-wrap:break-word;line-break:after-white-space;font-family:Helvetica;color:rgb(0,0,0)"><div dir="auto" style="letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;word-wrap:break-word;line-break:after-white-space;font-family:Helvetica;color:rgb(0,0,0)"><div dir="auto" style="letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;word-wrap:break-word;line-break:after-white-space;font-family:Helvetica;color:rgb(0,0,0)"><div dir="auto" style="letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none;word-wrap:break-word;line-break:after-white-space;font-family:Helvetica;color:rgb(0,0,0)"><div style="font-family:Helvetica"><br>— </div><div style="font-family:Helvetica"><br></div><div style="font-family:Helvetica"><b style="font-family:Helvetica">Rachel Schoeppner, Ph.D</b></div><div style="font-family:Helvetica"><b style="font-family:Helvetica"><br></b></div><div style="font-family:Helvetica">Nanostructure Cleanroom Facility Manager</div><div style="font-family:Helvetica">California NanoSystems Institute (CNSI)</div><div style="font-family:Helvetica">University of California, Santa Barbara</div><div style="font-family:Helvetica"><div style="font-family:Helvetica"><a href="mailto:rlschoeppner@ucsb.edu" style="font-family:Helvetica" target="_blank">rlschoeppner@ucsb.edu</a></div><div style="font-family:Helvetica"><a href="mailto:rachel@cnsi.ucsb.edu" style="font-family:Helvetica" target="_blank">rachel@cnsi.ucsb.edu</a></div><div style="font-family:Helvetica">(805)893-2296</div><div style="font-family:Helvetica"><br></div></div><div style="font-family:Helvetica"><br></div></div><br></div><br></div><br></div><br></div><br></div><br></div><br style="color:rgb(0,0,0);font-family:Helvetica;font-size:12px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration:none"><br>
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</div>-- <br><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><p class="MsoNormal"><font color="#000000" face="arial, sans-serif">______________<br></font><span style="color:rgb(0,0,0);font-family:arial,sans-serif">Brian Little, Ph.D.<br></span><span style="color:rgb(0,0,0);font-family:arial,sans-serif">Senior Research Scholar<br></span><span style="color:rgb(0,0,0);font-family:arial,sans-serif">Electrical and Computer Engineering Department<br>Campus Box 7911<br></span><span style="color:rgb(0,0,0);font-family:arial,sans-serif">2410 Campus Shore Drive, Room 322F<br></span><span style="color:rgb(0,0,0);font-family:arial,sans-serif">Monteith Engineering Research Center (MRC)<br></span><span style="color:rgb(0,0,0);font-family:arial,sans-serif">Raleigh, NC 27606<br></span><span style="color:rgb(0,0,0);font-family:arial,sans-serif">Email: </span><a href="mailto:bdlittl2@ncsu.edu" style="font-family:arial,sans-serif" target="_blank">bdlittl2@ncsu.edu</a><br><font color="#000000" face="arial, sans-serif">Mobile: 919-272-4984<br></font><img src="https://i.postimg.cc/52QQf0fg/ncsu.jpg" width="200" height="33"></p></div></div></div></div></div></div></div></div></div></div></div></div>