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Electron-beam action induced CaSi2 crystal nucleation and growth at the CaF2 epitaxy on Si
* 1, 2 , 3 , 3 , 3, 4 , 1 , 2, 5 , 5
1  Rzhanov Institute of Semiconductor Physics of Russian Academy of Science. Email:
2  2Novosibirsk state university, Russian Federation
3  1Rzhanov Institute of Semiconductor Physics of Russian Academy of Science.
4  2Novosibirsk State Universities, 630090 Novosibirsk, Russia
5  Rzhanov Institute of Semiconductor Physics, Siberian Branch of Russian Academy of Sciences
Academic Editor: José Luis Arias Mediano


The effects of electron-beam irradiation (electron energy 20 keV, current density 50 μA/m2) on CaF2 films epitaxially grown on Si(111) has been studied with reflection high-energy electron diffraction (RHEED) and Raman spectroscopy (RS). It was found that the electron beam action leads to the CaSi2 layer synthesis as during the epitaxial growth of СаF2 films and with irradiation after formation of CaF2 films. The radiation-induced phenomena of CaSi2 crystal growth were investigated, both directly during the epitaxial CaF2 growth on Si (111) and film irradiation with fast electrons on Si(111) after its formation of CaF2 films with keeping the specified film thickness, substrate temperature and radiation dose. Irradiation in the process of the epitaxial CaF2 film growth leads to the formation of CaSi2 nanowhiskers oriented along the direction <110>. The electron irradiation of the formed films, under similar conditions, leads to the homogeneous nucleation of CaSi2 crystals and their proliferation as inclusions in the CaF2 film. It was shown that both approaches lead to the formation of CaSi2 crystals of the 3R polymorph in the irradiated region of a 10 nm thick CaF2 layer. The crystal structures of CaSi2 was found to depend on thickness of deposited СаF2 films: it is trigonal rhombohedral modification tr3 for thin (<20nm) СаF2 films and trigonal rhombohedral modification tr6 for thicker one.

The reported study was funded by RFBR and ROSATOM, project number 20-21-00028

Keywords: crystal structure, nanostructures, electron-beam radiation, molecular-beam epitaxy, calcium compounds, silicon