Partnership in optical coatings venture?

[MechEng3]

I have found this little gem. I would like to find out if there would be enough interest in forming a GB or partnership in this unit. It could very well be a huge headache and/or a mixed blessing for the oportunity at this type of equipment. Comments? Suggestions? Pipe dreams of home-brew coatings?


http://cgi.ebay.com/Denton-Desk-II-M...item2a02cfef75

[mixedgas]

Thats a metalizer for scanning electron microscopes, not for dielectrics. It puts down 100 nm of silver, carbon, or palladium. We can build you something for 1/2 the price. The fact that it does not get to 10e-6 torr is the giveaway.

Steve

[MechEng3]

OK my bad..........just always looking when I have time to do some crazy searching.

[mophead]

It would be *really* really cool to be able to do custom coatings on a hobbiest level.

Imagine the possibilities.

Knowing nothing about UHV, what all would it take - bare minimum?

[DMills]

Chamber, Clean UHV pump stack (backing, Turbo, Ion would probably be favourite, maybe sorbitron, maybe trade the turbo for a diffstack plus LN2 trap, but those have a few subtle points), lots of dicking around with a helium leak detector or helium plus an RGA to find and seal all the leaks, Then you use thermal or ion assisted deposition with an interferometric measurement of the film thickness....

It could be done with ameteur kit, but is at least as chalenging as say making your own laser tubes.

Regards, Dan.

[mixedgas]

For simple quarterwave stacks he can get by with a turbo and a rougher and a quartz crystal thickness monitor. Or run a referenced beam through a window and watch the peaks on a chart recorder.

I've worked on a ebeam coater, the only magic is sheer amount of Ln2 we used, about 4-6 gallons a run for the cryopump.

Steve

[mixedgas]

[QUOTE=mixedgas;125758]For simple quarterwave stacks he can get by with a turbo and a rougher and a quartz crystal thickness monitor. Or run a referenced beam through a window and watch the peaks on a chart recorder.

I've worked on a ebeam coater, the only magic is sheer amount of Ln2 we used, about 4-6 gallons a run for the cryopump.

With care the helium leak detector becomes optional. A co worker broke the 3000$ glass bell jar, so we turned the matching oring vacuum flanges on a big lathe and tig welded them to a 14" piece of steel pipe, then set a piece of jig plate on top of the chamber for a lid. The ebeam transformer was about 2 kv at 5 amps, but it had a thermal evop option too. I have a box of the evap cathodes, and a full evap module is only about 70$ each.

With the kind of big lathes mecheng has access to, making the chamber is not difficult.

Steve

[shrad]

that's an interesting thread

at laserfreak we had a discussion about simple evaporation coating using a tungsten filament under light vacuum, and it turned to be a lot more difficult than what we thought

I can imagine the evaporation technique at the amateur scale, but how about the sputtering? Is it like what we see in electronic tubes, these metal coated zones, where it behaves like an electron gun evaporating the target and deposing particles on the surface behind?

What would be achievable with, for example, a fridge compressor as the main pump and perhaps anoter one in serie? I can imagine the vacuum needed for at least a faint electron beam wouldalready be huge... (forgive the fridge compressor pump, I know it's real crap, but I have one in my garage)

[mliptack]

From my understanding a fridge compressor can actually pull a pretty good vacuum... granted age and a few other factors come into play, but they can compete with A/C vacuum pumps from what I have read.

[DMills]

Apart from the obvious issues of oil backstreaming (which could be handled with a trap) the major issue with a fridge compressor as a roughing pump will be the small size of the suction line.

As pressure drops gas flow changes from a bulk effect to one where we are talking about molecules just happening to drift into the pump, and small pipes really hurt the flow rates once you reach this region.
This is why pumps for high vac usage (Turbos, diff stacks and the like) all have LARGE suction ports (Turbos with suction ports almost a foot across are not that uncommon, and 6 inches is very common).

A good single stage pump (refrig or a fridge compressor) might get you down to 1mmHg (1 Torr), but you really want to go at least 10^3 times lower then that for this sort of thing, hence the turbo or diffstack.

A few things:
1) With a fast enough pump, the chamber becomes rather less critical.
2) Watch out for X Rays! If you are dicking around with E beam or Ion beams then there can be a real hazzard and it is the soft ones that are dangerous.
3) Ebeams and glass belljars... Just dont! You will end up with a stray beam on the glass = very localised heating = bang!
The "Bell Jar" website has good amateur vac stuff.
4) water vapour is the demon of UHV work (Together with fingerprints, which can outgas for weeks), having a large cold (LN2, or similar) surface somewhere directly in the chamber (where stray beams cannot get to it and protected from radiative heating) will make you much happier.

Regards, Dan.