Epitaxial growth of Be on α-Al₂O₃

We report the growth of epitaxial single-crystal (0001) hcp-Be on (0001) α-Al₂O₃ substrates using molecular beam epitaxy. Thin films were characterized in situ with reflection high energy electron diffraction, and ex situ with ion beam analysis, electron microscopy, atomic force microscopy, and a variety of x-ray diffraction techniques. The in-plane orientation of films grown at substrate temperatures T in the range 10°C<T<270°C is Be[11̄00] ∥α-Al₂O ₃[12̄10] and Be[12̄10] ∥α-Al₂O ₃[11̄00], while at T=500°C the Be is aligned with the substrate. At T=10°C the films are smooth, but the roughness increases with increasing T. At T=500°C the crystal perfection improves dramatically but the Be forms large islands.