7 September 1999 Structural and mechanical properties of evaporated pure and mixed MgF2-BaF2 thin films
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To grow dense and hard MgF2 films substrate temperatures of about 300 degrees C are required, which unfortunately leads to high tensile film stress and the ability of crack formation. Lowering tensile stress in MgF2 films can be achieved by admixture a second fluoride material of higher cation radius than Mg2+. While former investigation were performed with non-heated films the purpose of the present work was to verify the behavior of mixed films when deposited at elevated substrate temperatures. One of the promising add material is BaF2 which enables evaporation of appropriate pre-mixed materials from a single source. The BaF2 content in the mixed films was varied from 3 to 55 mol percent in the MgF2 host. Optical, mechanical, and structural properties of samples deposited at different substrate temperatures have been studied by spectral photometry, IR spectroscopy, ex situ measurement of mechanical stress, x-ray diffraction, and -reflectometry, RBS, as well as investigation of surface morphology.
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Roland Thielsch, Roland Thielsch, Matthieu Pommies, Matthieu Pommies, Joerg Heber, Joerg Heber, Norbert Kaiser, Norbert Kaiser, Jens Ullmann, Jens Ullmann, "Structural and mechanical properties of evaporated pure and mixed MgF2-BaF2 thin films", Proc. SPIE 3738, Advances in Optical Interference Coatings, (7 September 1999); doi: 10.1117/12.360125; https://doi.org/10.1117/12.360125

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