MgF2 coating

[macona]

Wow, neat site. I was messing around and made a mirror like you described with almost 97% reflection at 1121 and about 1% at 1064. It is a mess though, I would be curious to see what the filter actually looked like if it was made. I had to find another computer with an old enough version of IE for the site to work right.

MgF2 and TiO2 both can be evaporated. You would almost need some sort of automation system to deal with the multiple layers of Ti02. After coating MgF2 you need to add a partial pressure of oxygen because Ti02 decomposes to TiO and Ti which are not transparent without. Then you have to pump out the O2 again to coat MgF2.

[macona]

Got a 2000l/s turbo set and made adapters and got it installed on the system in place of the old diff pump. Now I have a nice, dry system. I also installed a stepper controlled gate valve on it that works with a adaptive pressure control to maintain a set pressure in the chamber for doing higher pressure stuff like sputtering.

It still pumping down, lots of water in the system, down to 5x10^-7 torr right now. Heck, I had to hose out the gate valve housing after scrubbing all the light surface rust that had accumulated in it. Whatever they were pumping caused stainless to rust, weird. No trace of it on the RGA though.

I am also building a new filament controller for doing thermal deposition. I am not happy with the existing transformer setup, it uses the ground as a neutral. I am building a power controller for a 5v, 600A switching power supply, that ought to do the trick.

Turbo pump installed and running by macona, on Flickr

[krazer]

Looking good! Must have taken a while to machine that adapter...

[macona]

Looking good! Must have taken a while to machine that adapter...

It wasnt bad. The ASA to ASA adapter was pushing the limits of my lathe at being 11" in diameter. I ended up having to mill out the perimeter of the adapter because I couldnt get it on the lathe. I think it turned into a 8 hour job.

Untitled by macona, on Flickr

The ASA to ISO250 adapter was pretty simple. A hole in the center of a plate, a circle of through holes, another circle of 3/4" threaded holes, and a groove on the back side. I got to try threadmilling for the 3/4-10 bolts holes in the plate. Worked pretty slick:



6" ASA to ISO250 pump adapter by macona, on Flickr

The pump is mag lev, pretty cool, floats in space so no bearings to wear out.

Untitled by macona, on Flickr

[macona]

And I got another vacuum system. This one came out of SITe, a company that made scientific grade CCDs, they went under about 11 years ago and this was in storage since. It is a smaller system with a 6" diff pump with water cooled baffle and LN2 trap. It is combination of a Veeco 770 and CHA 600 series machine with a 19" bell jar. It is set up for evaporative coating of Al, CU, and Au.

After replacing about 30 broken water fittings I did a copper coat on a microscope slide last night.

Veeco 770 vacuum coater by macona, on Flickr

Veeco 770 vacuum coater by macona, on Flickr

Veeco 770 Cha 600 coater by macona, on Flickr

Thermal Evaporation by macona, on Flickr

Thermal Evaporation by macona, on Flickr

[planters]

Macona,
This is a compelling undertaking. Nice set up and I would put your coater in the entry way to my house. It is an industrial work of art.

The O-ring in your flange looks like buna-N. For very high vacuum, don't these things need to be plastic or metal?

[macona]

Most seals in this setup are nitrile or viton. Rubber seals are good down to the 10^-8 range without much of an issue. More if you have a really fast vacuum pump. You really only need metal seal when you want to get into ultra high vacuum where you really start having to worry about baking parts out to get rid of water molecules. Copper gaskets are the only thing that will take the heat.

The problem with copper gaskets is they are single use and in a bell jar setup that would get expensive in a hurry.

I was very surprised with the new little system. After its initial run down to about 2x10^-7 torr after it had been sitting for several days the pressure was still in the -6 range.

[krazer]

As long as you have good conductance to the diff pump getting down to low e-6 torr is usually pretty quick as long as you do not have too many virtual leaks or fingerprints.

Did you abandon the original chamber? Or make any progress in building an ebeam? Strait gold/aluminum mirrors are better than nothing, but we have all been spoiled by modern protected silver or dialectric mirrors ;-)

[macona]

As long as you have good conductance to the diff pump getting down to low e-6 torr is usually pretty quick as long as you do not have too many virtual leaks or fingerprints.

Did you abandon the original chamber? Or make any progress in building an ebeam? Strait gold/aluminum mirrors are better than nothing, but we have all been spoiled by modern protected silver or dialectric mirrors ;-)

Yeah, it gets down to the -6 within a couple minutes of opening the diff pump main valve. I have not used LN2 with the trap yet, I need to repump my 50L dewar, it is not holding as long as I think it should. I also need to get some more LN2 for the EDX on the SEM, there were about 30 brass fittings cracked or broken on this machine, not sure why. No obvious corrosion but it looks like a lot of the brass became brittle. I am going to section a couple of the fittings and check them out in the SEM.

No, the big chamber is definitely not abandoned. I got a proportional valve controller for the gate valve and need to hook up a barotron to the main chamber so the controller can do it's job and regulate the gate valve so I can do partial pressure stuff for sputtering. I was building a new evaporator controller for that system but that got pushed to the side now that I have this new system. I am going to yank out the home made evaporator setup inside the big one which will free up some feedthroughs for e-beam whenever I get to that.

With the 2000l/s turbo on that system I can be down to mid -5 within about 5 minutes of turning on the system and the turbo not even fully spooled up.

[mixedgas]

When would you be ready to coat four pieces of four sided 9 mm diameter beam combiner Axicons with a AL Enhanced mirror with overcoat?
I've been sitting on these prototypes for years...

Steve