[labnetwork] Outgassing and evaporation of Barium source in MBE

[Hathaway, Malcolm R]

Hi Saba,

I checked with my MBE guy, and he offered the following:

"I've used barium quite a bit. I definitely recommend purchasing dendritic barium sealed in a glass ampoule instead of packed with oil and then minimize exposure to oxygen and water. We would try to load it right before pumping down. Some suppliers can even load the Ba into a customer supplied crucible for you under argon. I've seen some reports of pre-melting the Ba source in a crucible under inert atmosphere to provide a uniform surface but that takes a bit more effort."

I'll forward you his e-ddress in a PM.


Mac
Harvard CNS
________________________________
From: labnetwork-bounces at mtl.mit.edu <labnetwork-bounces at mtl.mit.edu> on behalf of Saba Sadeghi <saba.sadeghi at uwaterloo.ca>
Sent: Thursday, November 21, 2019 12:45 PM
To: labnetwork at mtl.mit.edu <labnetwork at mtl.mit.edu>
Subject: [labnetwork] Outgassing and evaporation of Barium source in MBE


Hello everyone,


I was wondering if anyone has worked with evaporation of Barium using effusion cell in a MBE chamber and I was hoping to get some insight from this experienced community.


I have issues with outgassing of the Ba source; since it is very reactive with air outgassing to get rid of H2 and H2O would take time. I tried to limit the time that the Ba source was exposed to air after cleaning with hexane (it's shipped in mineral oil), but for me it's taking more than two weeks now to reach pressure of below 1.00 E-7 mbar while keeping the source temperature at 400 oC. The base pressure of the chamber is 2 E-10mbar. I was wondering if anyone has experienced this problem and what's the best way to degas Ba before evaporation?


Thanks in advance,

Saba


--

Saba Sadeghi, PhD

Quantum Devices Fabrication Scientist

Institute for Quantum Computing, University of Waterloo

Phone: 519-888-4567 ext. 31111

Email: saba.sadeghi at uwaterloo.ca


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