Deposition and characterization of gold black coatings for thermal infrared detectors
2010
High absorptivity and low thermal mass are two important requirements for coatings applied to thermal infrared
detectors. Gold black coatings are very good candidates to ensure these characteristics in the broadband infrared
spectral range. A specific deposition system was designed and built at INO in order to provide gold-black coatings
for different broadband detection applications including the broadband radiometer (BBR) instrument for the
European Space Agency (ESA) EarthCARE satellite. A parametric study targeting uniform optical absorptance
within the spectral range from 0.2 μm to 50 μm was conducted. Specular reflectance lower than 10% was obtained
for extended wavelength range up to 100 μm. The coating thickness ranges typically between 20 μm and 35 μm,
with uniformity of about ± 3 μm over a sample surface of 10x10 mm 2 . The deposit density was typically ~0.3% of
the bulk density of gold. To singulate the blackened infrared detector pixels, a laser micromachining process was
developed. The setup exhibits a 1μm positioning accuracy and allows for ablation of 3 μm to 12 μm wide channels
through the gold-black thickness, while preserving the pixel and gold-black deposit integrity.
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