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 »

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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Ed Meserve
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Re: Germanium Sputtering in the new Reserach Facility

Post by Ed Meserve »

That's a handsome setup, Dennis!
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Dennis P Brown
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Re: Germanium Sputtering in the new Reserach Facility

Post by Dennis P Brown »

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 »

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

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

Post by Dennis P Brown »

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 »

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 »

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 »

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 320 times
Cheers
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Re: Germanium Sputtering in the new Reserach Facility

Post by ian_krase »

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 »

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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Re: Germanium Sputtering in the new Reserach Facility

Post by John Futter »

as promised a few pics of a Ge target that got a little hot
Ge_Melt1.jpg
Ge_Melt2.jpg
Ge_Melt3.jpg
Ge_Melt6.jpg
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Re: Germanium Sputtering in the new Reserach Facility

Post by ian_krase »

Those spikes remind me of the tungsten field emitters formed for vacuum microelectronics (basically MEMS vacuum tubes)

I use a standard KF40 manual angle valve plus a needle gas inlet valve to adjust pressure. The meaningful adjustment range for the gate valve is all pretty close to closed, but you get a good number of degrees between hermetically closed and substantially open.


What's the anode in this system? Does it have a way of biasing the substrate?
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