Hi,
This is an imteresting group. I have been involved in thin films for
about 20 years.
We have 3 E-beam systems, utilizing cryo-pumps for deep vaccum. Other
equipment includes spectrometers, photometers, and
spectralradiometers. We use crystal monitoring for thickness
monitoring. We are now placing and optical monitoring system for
improved accuracy. The E-beam power supplies are 2 10KV an 1 14KV
system. We feed these power supplies with 3 phase 220V at 100Amp. Two
of them are air-cooled. The 14KV system is water cooled.
I usually design and make interference filters. This weekend, I
coated 12 mirrors from 6" to 10" in size and about 50 diagonals.
I found an interesting combo of layers that I really like. It starts
with about 20nm of Chromium, followed by 130nm of Aluminum and
finished with 4 layers of Tantalum Pentoxide(Ta2O50) and SiO2 for
enhancement and protection. I get about 94% reflectivity with this
combo. I find that very few people use Ta2O5.
I found that the thin Chromium layer all, but eliminates pinholing.
The Ta2O5 is an extremely adherent material and combines very well
with SiO2. I have silver mirrors that I coated the same way. I have
one mirror in my MN56 that is over 3 years old and is still like
brand new. The reflectivity of that mirror is about 97%.
Al M
