Sol–gel preparation of TiO2 and MgF2 multilayers
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TiO2 and MgF2 thin films were prepared by sol–gel processing. Their microstructure was investigated by scanning electron microscopy, X-ray diffraction and ellipsometric porosimetry as a function of the number of coating-firing cycles with different single layer thicknesses. TiO2/MgF2 multilayers were processed in different stacking sequences; the nucleation of the subsequent material was correlated to the underlying crystal structure and the respective film morphology. It was found that dense crystalline MgF2 films on glass can be manufactured by homoepitaxial growth of multiple thin layers. On an underlying TiO2 layer the effect of densification and crystallization is increased. In the reverse film order no such effect could be observed.
KeywordsThin films MgF2 TiO2 Multilayer Optical films
The authors thank Christina Claes and Manfred Römer for performing the SEM measurements and some coating experiments. The supply of MgF2 coating solutions by Professor E. Kemnitz, Humboldt University, Berlin is gratefully acknowledged.
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