I'm working with a ZnSe window and, during my process, I observed a white coat on the window's surface. It's uniform with some clear spots that look like a drop.
It could have been methanol or IPA, lens wipes, UV light, heat (200 °C), or contamination from NOA or epoxy.
What do you think could have caused the white coat? How can I remove it without damaging the crystal?
Thank you
edit: I found that "Zinc Selenide oxidizes significantly at 300°C", it could be that
Only generic cleaning guidelines are given, since the kind of ('white') contamination/corrosion is not identified ― as it would be preferably. Note, however, that ZnSe is generally attacked by acids, even at room temperature.
You may first try cleaning by gently swabbing the contaminated surface with a polishing microfiber cloth impregnated with some ZnSe-compatible cleaning solvent; such as acetone, isopropanol, hexane, diethyl ether, or chloroform. If that fails, you may still try cleaning by warm water and soap. If you think that etch-polishing is required; you may still consider alkalinized potassium ferricyanide aq. sol.: K3Fe(CN)6 (≤ 30 g) + KOH (0.57 g) + H2O (100 cm3); 1―2 min at room temperature.
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