Germanium Sputtering in the new Reserach Facility

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Dennis P Brown
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Germanium Sputtering in the new Reserach Facility

Post by Dennis P Brown » Wed Oct 14, 2020 2:10 pm

Well I finally am using my new research building for, well, research! How novel. I am trying to make high quality germanium (Ge) films on plastic or glass. I can't get consistent quality films because (I believe) the coating requires slightly better vacuum than my mechanical pump can achieve - about 5 microns. So to explore the parameter space of lower vacuums (0.1 to 5 microns), I will use my turbo and its manual gate valve to adjust the argon pressure in my sputtering system to that range. I am adding a more accurate gauge that can better read in that range (my analog gauge is not accurate below 5 microns.)
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20201014_095848.jpg
Complete system
20201014_095903.jpg
Sputtering Chamber

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Ed Meserve
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Re: Germanium Sputtering in the new Reserach Facility

Post by Ed Meserve » Wed Oct 14, 2020 3:24 pm

That's a handsome setup, Dennis!
Ed Meserve

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Dennis P Brown
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Re: Germanium Sputtering in the new Reserach Facility

Post by Dennis P Brown » Wed Oct 14, 2020 3:32 pm

Thank you! It is a mix of surplus, home made (mostly the metal work) and jury-rigging so I am pleased it all works. I do try to make stuff look semi-proffesional.

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Richard Hull
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Re: Germanium Sputtering in the new Reserach Facility

Post by Richard Hull » Thu Oct 15, 2020 12:00 am

Nice gear in you new building. Sputtering goes much smoother with better coatings at 10e-6 torr.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Dennis P Brown
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Re: Germanium Sputtering in the new Reserach Facility

Post by Dennis P Brown » Thu Oct 15, 2020 11:34 am

For metal vapor deposition 10^-6 torr is essential. Sputtering requires a gas (generally argon) to 'knock' off ions of metal. This creates near zero heating of the substrate and this makes this process so useful. Sputtering is often done in the low torr to high micron range for this reason. Certainly a magnetron can work at the lower pressure range (my unit is a magnetron.)

Still, some metals are tricky to coat (Al is so slow no one would bother) so I am hoping Ge isn't one such. I could use vapor dep but the substrate will be 20 micron plastic and that process would likely melt the plastic. So I'm trying this process. I've done nickel, and Pd and Au very successfully but these coat at higher pressures (30 to 150 microns.)

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Re: Germanium Sputtering in the new Reserach Facility

Post by John Futter » Thu Oct 15, 2020 6:18 pm

Dennis my sputtering system at work uses a 20kV 2mA argon beam to ablate a target held at 45 degrees to the beam this then sprays the ablated onto rotating catchers. Benefit of this system is the ions arrive with 10 -100eV of energy so chemically bond to the receiving surface. Your sputter coater is the sort used to make SEM samples conductive.
I melted my germanium target in our system melted germanium has some very interesting properties on solidification i'll try and find a SEM pic of the volcanic like growths

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Dennis P Brown
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Re: Germanium Sputtering in the new Reserach Facility

Post by Dennis P Brown » Thu Oct 15, 2020 8:02 pm

Those images would be good to see.

These will be used as laser targets ( 2000 J/1 ns pulse @ 238 nm focused to a few tens of microns square.) Used in studies for direct drive fusion related science.

Peter Schmelcher
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Re: Germanium Sputtering in the new Reserach Facility

Post by Peter Schmelcher » Fri Oct 16, 2020 6:34 am

Nice setup.

I attempted gate valve pressure control a few years back and moved on to mass flow controllers.
In hindsight I think it was an area problem in that the gate valve position was almost fully closed for the pressure I wanted. The net result was a big pressure change with a very small mechanical adjustment with my setup.

You might find the attached 2010 paper on sputtering interesting.
Inverted Magnetron Source.pdf
(943.14 KiB) Downloaded 21 times
Cheers
-Peter

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Re: Germanium Sputtering in the new Reserach Facility

Post by ian_krase » Mon Oct 19, 2020 4:32 am

Looks pretty cool. Probably works a lot better than my homemade experimental setup.

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Dennis P Brown
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Re: Germanium Sputtering in the new Reserach Facility

Post by Dennis P Brown » Mon Oct 19, 2020 10:09 am

Peter, you are correct - for the micron pressures I require a manual control using the type of gate valve I have is really poor. Mass flow is superior for any gas input flow control but its vacuum control I need to regulate - I'd empty my small lecture bottle if I simply used gas flow to counter the turbo. I have managed to use a manual 'butter fly' gate valve to control my fusor very well but a 'slide' to close gate valve is certainly not a very good device for this purpose. But I can't easily switch out the two devices so I will attempt to use the one I have installed on the turbo. If it proves too difficult, guess I'll deal with that issue then.

Thanks Ian; it is partly a useless (i.e. not working) old sputtering system I used for a base, glass tube and its vacuum gauge; all else failed (power supply, upper cathode assembly.) So I added what I needed to get it to work.

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