From trial and error (not by calculation) I have found that a one-inch long piece of nearly-pure aluminum wire about 3-4 mm in diameter works best for us. (I'll recheck those measurements later) it's about 1/5 to 1/3 cubic cm I think.
We have a single tungsten filament about 60 cm from the mirro suspended overhead in our bell jar.
I figure, using 4*pi*r^2 for the area of a two foot radius sphere that the aluminum is spread over an area of 45,239 sq cm. Sp this roughly 0.3 cc of Al is spread to a thickness of something like 80 nm if I did all the conversions correctly.
As I said, I need to check the weight/mass of the wire that we typically use.?
On Apr 13, 2011, at 9:45 AM, "Aurigema, Andrew N. (KSC-ESC-620)[QinetiQ North America - ESC]"<
andrew.n.aurigema@...> wrote:
?
I have a sideways flow stationary emitter array that seems to yield good results.? I recently added a digital thickness indicator to my rig so now have actual numbers to put to the thickness.? Using a witness plate, I am just barely able to see the noon day sun thru the coating with about 140 nm of aluminum deposited.? This number is from my digital thickness unit that Ken Hunter built so I got a lot of faith in the number.? ?I deposit about 10 nm per second and run the unit for about 15 seconds.? ?I personally like to put on more aluminum ( like 350 nm ) because I don¡¯t overcoat and thin coatings don¡¯t last as long.? The experts say ? wave of red 550 nm light? ( around 140 nm ) is ideal.? ??
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Hope it helps
?
Drew in sunny Florida
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From: VacuumX@... [mailto:VacuumX@...] On Behalf Of Vladimir Chutko
Sent: Wednesday, April 13, 2011 4:05 AM
To: VacuumX@...
Subject: Re: [VacuumX] coating thickness error tolerance
?
?
Hi,
Coating uniformity depends on substrate holder type (single or planetary
rotation), chamber dimensions, evaporator position, coated surface shape
and some other factors. For industrial coating machines with single
rotated substrate holder coating uniformity less than 5% is usually
specified. For machines with substrate holder double planetary rotation
the thickness uniformity about or even less than 1% is available,
sometimes the extra rotating mask is used. However it doesn't mean that
you can obtain so high uniformity for any coating made of any materials.
Uniformity also depends on evaporated material distribution in the
chamber volume which may vary for different materials and during a time
of evaporation. We usually obtain uniformity in mass production of
e-beam evaporated multilayer dielectric coatings (not the thickness but
optical properties, it is close but not the same) less than 2% in the
chamber Dia.72"x72" with double planetary rotating substrate holder and
rotating mask. But not for all coatings, for some of them less than 1%,
for some - about 5%.
Best regards,
Vladimir Chutko
On 4/13/2011 12:06 AM, deepak wrote:
> Hi,
> This is my first post in the group. I want to know the tolerance in thickness variation (in nm) of Aluminium coating, acceptable and expected from professional and amateur coaters.
>
> Mr Jan van Gastel in interferometry group has finished a mirror accurate to<5nm. So I think coating error introduced in 100 nm film thickness would be less than 1 nm. Is such precision achieved routinely by coaters in this group?
> Thanks and with regards,
> Deepak
> Ahmedabad, India
>
>
>
>
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