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

In the present work we report on the initial stage of CaF2 growth on Si(001) at 750 °C. Samples with submonolayer coverage are grown and in situ studied by low energy electron diffraction and scanning tunneling microscopy. The unusual diffraction patterns with asymmetrically split fractional reflections and streaks are ascribed to the antiphase relations at the surface characteristic for the studied CaF2 coverage. A statistical model built to describe the partially ordered array of 3× cells shows good agreement with the observed diffraction patterns. Similarities between CaF2/Si(001) and metallic Ca/Si(001) interfaces are discussed.