Epitaxial growth and characterization of CaF2 on Si

Abstract

CaF₂ films have been grown epitaxially on (100) and (111) Si substrates by molecular beam epitaxy. These films have been characterized by electron microscopy, reflection high‐energy electron diffraction, Rutherford backscattering ion channeling, and back‐reflection Laue x‐ray diffraction. In addition, chemical etching has been used to reveal dislocations and to delineate cracks. Film cracking appears to be related to crystalline perfection through misfit dislocation mobility. It is possible to grow high quality, (x_min=3.0%) single‐crystal films on (111) Si which are free of cracks and atomically flat. However, the high free energy of the (100) surface in an ionic fluorite crystal prevents the growth of comparable CaF₂ films on the (100) Si surface.