Formation, structure, and optical properties of single-phase CaSi and CaSi2 films on Si substrates

Abstract

In this paper, we report on optimizing the conditions for subsequently growing single-phase films of calcium monosilicide (CaSi) and calcium disilicide (CaSi2) on single-crystal silicon by reactive deposition epitaxy (RDE) and molecular beam epitaxy (MBE). The temperature range for the growth of CaSi films (400–500 °C) was determined, as well as the temperature range (600–680°C) for the growth of CaSi2 films on silicon with three orientations: (111), (100) and (110). The minimum temperatures for the epitaxial growth of CaSi films by the RDE method and CaSi2 films by the MBE method were determined, amounting to, respectively, T = 475 °C and T = 640 °C. An increase in the ratio of Ca to Si deposition rates to 26 made it possible to grow a large-block CaSi2 epitaxial film with the hR6 structure by the MBE method at T = 680 °C. Raman spectra and reflection spectra from single-phase epitaxial CaSi and CaSi2 films on silicon were recorded and identified for the first time. The correspondence between the experimental reflection spectra and the theoretically calculated reflection spectra in terms of amplitude and peak positions at photon energies of 0.1–6.5 eV has been established. Single-phase CaSi and CaSi2 films retain transparency in the photon energy range 0.4–1.2 eV.