STM and LEED studies of CaF2 submonolayer coverage on Si(001)

► Initial stage of CaF2 growth on Si(001) at 750°C are in situ studied by LEED and STM. ► Unusual asymmetrical splitting of the fractional reflections is ascribed to the antiphase relations at the surface. ► A statistical model is built to describe the partially ordered array of 3× cells in good agreement with the observed diffraction patterns. ► Similarities between CaF2 / Si(001) and metallic Ca / Si(001) interfaces are discussed.