Epitaxial Relations in Fluoride Films Grown on GaAs{lll} and Ge(lll) Substrates

Abstract

ABSTRACTEpitaxial relations in Cax Sr1−xF2(0⫶×⫶l) and BaF2 films grown on GaAs(111), (111) and Ge(111) 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. That is, the fluoride films on GaAs prefered 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° about the surface normal 〈111〉 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.