Molecular beam epitaxial growth of Eu-doped CaF2 and BaF2 on Si

The growth of Eu-doped CaF2 and BaF2 thin films on Si(100), (110), and (111) substrates has been realized by molecular beam epitaxy using elemental Eu evaporation. Very bright blue emissions from Eu-doped CaF2 and yellow emissions from Eu-doped BaF2 were obtained in the wavelength range of 400–850 nm at 10 K. Depending on the Si substrate orientation, the zero-phonon line of Eu2+ in the CaF2 thin films was shifted by different amounts relative to that of bulk CaF2 due to residual strain in these epilayers.