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It's the same story everywhere. Our latest theory was the carbon was being absorbed from the junk molecules in the vacuum during the elevated temperatures of deposition (and then it nucleates into particles during cooling). If it was diffusing in from the
carbon/fabmate crucible we think we'd see erosion of the crucible walls over time (which we did not notice). The latest approach to minimizing carbon contamination was to pump down to the low 10-7 torr before depositing rather than starting your deposition
in the high 10-7's (this sort of reinforces the above advice on keeping the chamber clean). And keep other contaminants off your Au during handling (no finger prints, rinse with alcohol, etc.).</div>
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The cleaner thermal evaporations makes sense from my perspective. When I've done thermal evaporation, we loaded fresh gold every time (we did not reuse the source material), so the gold did not experience a pervious evaporation cycle where it would absorb junk
from the vacuum.</div>
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I do like the idea of gettering with Tantalum. Will have to look into that.</div>
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My two cents. Hope you find a solution that works for you.</div>
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-Cliff</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> labnetwork <labnetwork-bounces@mtl.mit.edu> on behalf of Demis D. John <demis@ucsb.edu><br>
<b>Sent:</b> Saturday, February 1, 2025 7:43 AM<br>
<b>To:</b> Czwakiel, James <czwakj@rpi.edu><br>
<b>Cc:</b> Fab Network <labnetwork@mtl.mit.edu><br>
<b>Subject:</b> Re: [labnetwork] [EXTERNAL] Gold e-beam deposition - carbon contamination</font>
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<div dir="auto">Adding a tantalum pellet to the Au source will getter the carbon and reduce spitting. </div>
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<div dir="auto">I can’t quite find the original paper, but here are some web pages that reference it:</div>
<div dir="auto">1)</div>
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<div><a href="https://compoundsemiconductor.net/article/116629/Tackling_the_foot#:~:text=concern.-,The%20combination%20of%20the%20crucible%20liner%20and%20tantalum%20%E2%80%98getters%E2%80%99%20looks%20like%20a%20win%2Dwin:%20the%20deposition%20rate%20increases%20while%20reducing%20gold%20spitting.,-But">https://compoundsemiconductor.net/article/116629/Tackling_the_foot#:~:text=concern.-,The%20combination%20of%20the%20crucible%20liner%20and%20tantalum%20%E2%80%98getters%E2%80%99%20looks%20like%20a%20win%2Dwin:%20the%20deposition%20rate%20increases%20while%20reducing%20gold%20spitting.,-But</a></div>
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<div dir="auto">2)</div>
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<div><a href="https://www.memsnet.org/memstalk/16896/#:~:text=look%20for%20a%20paperwritten%20in%20the%201970s%20that%20suggests%20adding%20a%20small%20piece%20of%20tantalum%20to%20yourgold.%20%20The%20Ta%20will%20not%20melt%20but%20it%20will%20control%20the%20spitting.">https://www.memsnet.org/memstalk/16896/#:~:text=look%20for%20a%20paperwritten%20in%20the%201970s%20that%20suggests%20adding%20a%20small%20piece%20of%20tantalum%20to%20yourgold.%20%20The%20Ta%20will%20not%20melt%20but%20it%20will%20control%20the%20spitting.</a></div>
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I don’t have measurements of carbon contamination with this - although we do this in our e-beam evaporators. </div>
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<div dir="ltr"><font face="georgia, serif" size="4" style="font-family:georgia,serif; color:rgb(0,0,0)">-- Demis
</font><font face="georgia, serif" size="1" style="font-family:georgia,serif; color:rgb(0,0,0)">(<a href="https://wiki.nanotech.ucsb.edu/wiki/Demis_D._John" target="_blank" style="font-family:georgia,serif">contact info</a>)</font>
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<div dir="ltr" class="x_gmail_attr">On Sat, Feb 1, 2025 at 05:17 Czwakiel, James <<a href="mailto:czwakj@rpi.edu">czwakj@rpi.edu</a>> wrote:<br>
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<div dir="ltr">Youry</div>
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<div dir="ltr">Once contamination is detected…. Clean clean clean</div>
<div dir="ltr">All metal covers removed and blasted and ultra sonically cleaned </div>
<div dir="ltr">Plus …. Make sure crucibles are not touched even with gloved hands….. always use tweezers</div>
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<span style="font-family:Aptos,sans-serif">James Czwakiel</span></p>
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<div id="x_m_7999255587210345344divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt; font-family:Calibri,sans-serif; color:rgb(0,0,0)"><b style="font-family:Calibri,sans-serif">From:</b> labnetwork <<a href="mailto:labnetwork-bounces@mtl.mit.edu" target="_blank" style="font-family:Calibri,sans-serif">labnetwork-bounces@mtl.mit.edu</a>>
on behalf of Youry Borisenkov <<a href="mailto:yb2471@columbia.edu" target="_blank" style="font-family:Calibri,sans-serif">yb2471@columbia.edu</a>><br>
<b style="font-family:Calibri,sans-serif">Sent:</b> Friday, January 31, 2025 11:59:09 AM<br>
<b style="font-family:Calibri,sans-serif">To:</b> Fab Network <<a href="mailto:labnetwork@mtl.mit.edu" target="_blank" style="font-family:Calibri,sans-serif">labnetwork@mtl.mit.edu</a>><br>
<b style="font-family:Calibri,sans-serif">Subject:</b> [EXTERNAL][labnetwork] Gold e-beam deposition - carbon contamination</font>
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<div>Hi All and happy Friday,</div>
<div>I know it is a topic that has been discussed multiple times, however, I'm still lacking a solution that works and will appreciate you sharing your experience.</div>
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<div>Currently we are using a Fabmate crucible, and getting some carbon contamination . </div>
<div>For clean Gold layers we use thermal evaporation. The films are good but it requires a lot of gold.</div>
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<div>So far we tried using a Molybdenum crucible with and without a spacer. The issue with this approach was that eventually after some time, we get carbon contamination back. I believe it's present in the chamber and eventually a critical mass is built on
top of the gold in the crucible, coming from the chamber.</div>
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<div>Were anyone successful in overcoming carbon contamination in their e-beam deposition overtime? </div>
<div>What are the procedures you are following? Maybe cleaning more frequently?</div>
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<span>-- </span><br>
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<div style="color:rgb(136,136,136)">Thank you,</div>
<div style="color:rgb(136,136,136)">Youry Borisenkov</div>
<div style="color:rgb(136,136,136)"><a href="https://cni.columbia.edu/columbia-university-clean-room" target="_blank">CNI</a></div>
<div style="color:rgb(136,136,136)">Columbia University</div>
<div style="color:rgb(136,136,136)">CEPSR 1017, New York, NY, 10027, United States.</div>
<div style="color:rgb(136,136,136)"><a href="https://sustainable.columbia.edu/crown-commuter" target="_blank" style="color:rgb(17,85,204)"><img width="96" height="40" src="https://sustainable.columbia.edu/sites/default/files/content/crown%20commuter%20badge_0.png"></a></div>
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