Single-crystal sapphire (α- Al2O3) was implanted at room temperature with 200 keV erbium ions to a fluence of 8 X 1013 cm-2. Ion channeling using 1.6 MeV He+ shows that the crystal suffers little damage for this low dose implant. Angular scans through axial and planar directions in the crystal indicate that 70% of the Er atoms reside on displaced octahedral sites in the α- Al2O3 lattice. As pure l2O3 has a high density of free octahedral sites, this explains why high concentrations of Er can be dissolved in this material. Smaller fractions of Er are found on tetrahedral (20%) and random (10%) sites. The samples exhibit strongly peaked photoluminescence spectra around 1.5 µm, due to intra-4f transitions in Er3+, indicating the existence of well defined sites for the luminescing Er3+ ions. It is concluded that the octahedral site is the dominating optically active site in the lattice.

J. Mater. Res.
Photonic Materials

van den Hoven, G.N, Polman, A, Alves, E, da Silva, M.F, Melo, A.A, & Soares, J.C. (1997). Lattice site and photoluminescence of erbium implanted in a - Al2O3. J. Mater. Res., 12, 1401–1404.