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Letter 42037
Why Gold coating over Titanium Nitride
turns reddish when touched?
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We use a PVD (UBM) Machine (with Polycold) to coat Gold over
Titanium Nitride. Invariably, we find the color of Gold Coating
change to a Reddish Tinge when touched with bare fingers. When wiped
with a good cloth, this reddish tinge disappears.
We also find this to happen on the Titanium Nitride Coating, although
the TiN coating is visibly very good at a rich greenish yellow color
when taken fresh. The color of TiN turns reddish brown in the areas
touched.
Can some one help us to identify the actual cause of this?
Sreenivass NV
Premier Systems - Hosur, Tamil Nadu, INDIA
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How thick are the films? We tried using TiN for a quartz crystal
sensor coating at ~0.15 um but the surface roughness was ~0.1 um!
Unless the gold is thick compared to that roughness it will not
"smooth" over the spikes of the TiN surface.
Jeffrey C. Andle
- Westbrook, ME
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I forgot to actually get to the point... The finger oil is
absorbed in the rough surface and is optically on the order of the
wavelength. The coloration we observed varied depending on roughness
and what liquid...
Jeffrey C. Andle
- Westbrook, ME
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