a1 FOM-Institute for Atomic and Molecular Physics, Kruislaan 407, 1098 SJ Amsterdam, The Netherlands
a2 Dep. de Física, ITN, Estrada National 10, P-2685 Sacavém, Portugal
a3 Centro de Física Nuclear da Universidade de Lisboa, Av. Prof. Gama Pinto, 2, 1699, Lisboa Codex, Portugal
Single-crystal sapphire (α–Al2O3) was implanted at room temperature with 200 keV erbium ions to a fluence of 8 × 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 Al2O3 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.
(Received January 05 1996)
(Accepted November 02 1996)