[labnetwork] Chamber pressure during reactive e-beam evaporation

[Noah Clay]

Hi Aamer,

In MBE systems, thermal gas crackers are often used for low flux oxygen incorporation or other gases surface cleaning.  Operating pressures are low and dissociation efficiency drops rather quickly with gas flow.  Veeco, Scienta Omicron, Mantis and others have these as stock items.  Helpful Google search term: "oxygen gas cracker mbe”.

Best,
Noah Clay

Noah Clay
School of Engineering & Applied Science
University of Pennsylvania
Philadelphia, PA

> On Feb 7, 2019, at 9:57 PM, Mark Weiler <mweiler at andrew.cmu.edu> wrote:
> 
> Hi Aamar,
> 
> You could also try making a small 1/16” or 1/8” SS tube feed-through that allows a length of tube to enter the chamber and then bent into a position terminating nearby the substrate(s), thus permitting the small amount of O2 you already/currently use to be discharged directly at the substrate.  Inexpensive and worth a shot...
> 
> You would secure the swage fitting on the ATM side only after the correct length of tube within the chamber is determined.  If you do not have a small swage feedthrough, you could use a 1/4” feed-through (or 6mm) and then downsize with an adapter to 1/8 (3mm) nearby the substrate and have a small section of tube affixed there.
> 
> Best regards,
> 
> Mark
> 
> 
> 
> Mark Weiler
> Equipment & Facilities Manager
> Claire and John Bertucci Nanotechnology Laboratory
> Electrical and Computer Engineering | Carnegie Mellon University
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> 
> On Feb 7, 2019, at 22:25, Dr. Aamer Mahmood <amahmood at hbku.edu.qa <mailto:amahmood at hbku.edu.qa>> wrote:
> 
>> Hello all,
>> We have been doing reactive oxide depositions with e-beam evaporation of metals and a few sccm oxygen flowing through our system. We do not have a variable position gate valve and can only control the oxygen MFC settings. The corresponding chamber pressure has been less than 2e-4 Torr. 
>> I have recently received a request to deposit reactive metal oxide films at higher oxygen flow rates that'll correspond to higher chamber pressure during deposition.
>> I am hesitant to increase the deposition chamber pressure due to the increased flow rate because the manufacturer mentioned the aforementioned chamber pressure as an acceptable upper limit for the e-gun. 
>> I'd appreciate any insights/experiences on this matter particularly 1) how does increased oxygen pressure in the chamber affect the system hardware, 2) any safety concerns etc.
>> Thanks in advance.
>> 
>> -Aamer Mahmood
>> Qatar Environment and Energy Research Institute
>> Doha, Qatar
>> 
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