Mechanical stress in fluoride coatings

Jens Ullmann; Hans-Georg Keck; Roland Thielsch; Hein Uhlig; Norbert Kaiser

doi:10.1117/12.360074

7 September 1999 Mechanical stress in fluoride coatings

Jens Ullmann, Hans-Georg Keck, Roland Thielsch, Hein Uhlig, Norbert Kaiser

Proceedings Volume 3738, Advances in Optical Interference Coatings; (1999) https://doi.org/10.1117/12.360074
Event: Optical Systems Design and Production, 1999, Berlin, Germany

Abstract

The mechanical behavior of fluoride single layers and thick model layer systems were carried out ex-situ after deposition at laboratory conditions. The samples on substrates with different thermal expansion coefficients have been prepared by a low loss evaporation process. Investigation were performed for single layers deposited at different film thickness, substrate temperature and storage time. All investigated fluorides posses tensile stress of various amounts. The thermal stress component seems to be the major contribution to the total stress MgF₂ films of about 100 nm thickness deposited onto silicon substrate. The stress and force per unit width of model multilayer systems formed from different fluorides were examined and correlated to the ability of crack formation on thick rigid fused silica substrates. Optimization of the stress values, the bending force and the crack formation was performed by adjusting the deposition temperature and by introducing a third stress reducing material in the stack. An example of a stress optimized high reflector will be shown.

Citation Download Citation

Jens Ullmann, Hans-Georg Keck, Roland Thielsch, Hein Uhlig, and Norbert Kaiser "Mechanical stress in fluoride coatings", Proc. SPIE 3738, Advances in Optical Interference Coatings, (7 September 1999); https://doi.org/10.1117/12.360074

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