Polymorphic States in the Electron-Beam Exposure-Induced CaSi2 Film Growth at the CaF2 Epitaxy on Si

The results of the study of the crystal structure of CaSi2 films and their polymorphic transformations, depending on production conditions involving radiation-stimulated CaSi2 formation during heat treatment of a CaF2 layer, are presented in this contribution. CaSi2 films with space group $$R\bar {3}m$$ were obtained by exposing the CaF2 layer to an electron beam, both directly during the epitaxial growth of CaF2 and after the formation of CaF2 films of various thicknesses. In both cases, at the initial stage of epitaxial growth with thin CaF2 films (10 nm), the resulting CaSi2 film is characterized by space group $$R\bar {3}m$$ with a three-layer translational period of silicon substructures in the unit cell (tr3). As the CaF2 film thickness increases, the CaSi2 film formed via the radiation-stimulated process is characterized by space group $$R\bar {3}m$$ with a six-layer translational period of silicon substructures in the unit cell (tr6). Analysis of the results obtained in this work, together with literature data, leads to the conclusion that the incorporation of F into the silicide lattice stabilizes the formation of CaSi2 films with space group $$R\bar {3}m$$ corresponding to a specific polytype.