EPITAXIAL RELATIONS IN FLUORIDE FILMS GROWN ON GaAs left brace 111 right brace AND Ge(111) SUBSTRATES.

Epitaxial relations in Ca//x Sr//1//-//xF//2(0 less than equivalent to x less than equivalent to 1) and BaF//2 films grown on GaAs and Ge substrates were investigated by He ion channeling analysis and transmission electron microscopy. Though the lattice constants of GaAs and Ge are nearly the same, the relations were found to be completely different: the fluoride films on GaAs preferred to have an orientation identical to that of the substrate (type A orientation), whereas the orientation of the films on Ge was mainly rotated by 180 degree about the surface normal LT AN BR 111 RT AN BR axis (type B orientation). A hypothesis is proposed that the epitaxial relations in these systems are affected by the ionicity of the substrate as well as the lattice matching condition.