Published online by Cambridge University Press: 25 February 2011
When preparing single-crystal films of CaF2 on (111) oriented silicon by molecular beam epitaxy (MBE), we found that these dielectric films grew into either A or B type depending on the substrate temperature during growth. A-type films follow the same orientation as that of the substrate silicon, while B-type films rotate 180° about the surface normal with respect to the substrates.
X-ray diffraction (XRD) confirms the single crystallinity and identifies the epitaxial relationships between the film and the substrate. Epitaxial CaF2 films were obtained at growth temperatures ranging from 200°C to 800°C. Employing the asymmetric x-ray diffraction of atomic planes inclined to the sample surface, we found that A-type CaF2 grows at lower substrate temperatures, while B-type films dominate at higher temperatures.