Photoelectron diffraction study on the epitaxial growth of SrF2 on Ge(111)-c(2×8)

The initial stages of epitaxy of SrF2 on Ge(111)-c(2×8) have been studied by X-ray photoelectron diffraction (XPED). Forward-scattering peaks along the emitter–scatterer axes have been effectively used to determine the morphology of the overlayer. In addition, multiple-scattering analysis of the two-dimensional XPED patterns for the overlayer emission has provided the information on the average domain size of SrF2 islands. The epitaxy of SrF2 on Ge(111) has been characterized by (1) the 180° azimuthal rotation of the overlayer relative to the substrate, (2) formation of small SrF2 (111) islands of ∼2 TL (triple-layer) in thickness at deposited coverages below 1 TL-equivalent, and (3) aggregation of the islands into relatively large domains with the average height of ∼2 TL unchanged at coverages up to 2 TL-equivalent.