Sol–gel preparation of TiO2 and MgF2 multilayers

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.