4 optical filters – INFICON Guardian EIES Controller User Manual
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Guardian Co-Deposition Controller Operating Manual
adjustments to compensate for these differences; however, that does not
adequately compensate for the lower signals inherent in the setup. If you use this
configuration, install the first detector (#1 in this example) on the material with the
lowest deposition rate (lowest signal).
4.4 Optical Filters
A 1 in. (25 mm) round optical filter is mounted in the inlet of each detector. See
and
for installation instructions.
This filter selectively passes a specific wavelength of light that is the characteristic
emission from a specific material. The filter is a critical EIES component. The
characteristics and quality of the filter have a strong influence on the results. Filter
characteristics to consider include:
Transmission: The filter should transmit (pass) as much of the light as possible for
the specified wavelength. A filter is a lens with a special coating that blocks all light
except for a specified wavelength. Unfortunately, that coating also partially blocks
the desired wavelength. The result is a reduced light beam even for the wavelength
of interest.
Bandwidth: A filter passes wavelengths a little above and below the specified
wavelength (the transmission curve is a bell-shape). A 100 nm filter with a
bandwidth of 10 nm passes wavelengths from roughly 95 nm up to about 105 nm.
A very narrow-bandwidth filter is more selective in passing only the wavelength of
interest, but it may also result in lower signal level as well.
Some materials have primary emission wavelengths very close to other materials,
which means the filter and detector cannot distinguish one material from the other.
In these cases, a secondary emission wavelength may produce sufficient signal to
be usable. Contact an
INFICON
Thin Film Technical Support Engineer for
assistance in selecting an appropriate filter line.
lists common materials and their characteristic emission wavelengths.