Nonfaceted Growth of (111)-Oriented Epitaxial Alkali-Halide Crystals via an Ionic Liquid Flux in a Vacuum

Nonfaceted growth of (111)-oriented epitaxial KBr crystals on sapphire single crystal substrates has been achieved using a novel vacuum deposition method of flux-mediated epitaxy, involving the use of ionic liquids as a flux. It was found that the ionic liquid could act as a flux to promote the growth of KBr at higher growth temperatures and to stabilize its unstable polar (111) face with no faceting of the crystal surface. Even after evaporation of the remaining ionic liquid to remove it from the KBr crystals, the atomically flat (111) surface could be preserved without refaceting.