CaF2, SrF2, BaF2, and mixed (Ca,Sr)F 2 films have been grown epitaxially on Si (111) substrates by vacuum evaporation. The epitaxial relation between these fluoride films and the substrates has been investigated by ion channeling analysis. Both the CaF 2 and SrF2 films prefer to have orientations rotated 180°about the normal to the substrate surface. In contrast, the vast majority of (Ca,Sr)F2 films have orientations identical to those of the substrate, and the BaF2 film is composed of a mixture of the two. Analysis was also made on a Si/CaF2/Si(111) double heterostructure, which showed that the top Si film is again rotated 180°about the normal to the underlying CaF2 surface.
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