Damage recovery and optical activity in europium implanted wide gap oxides

Abstract

In this study we compare and discuss the defects and optical behaviour of sapphire and magnesium oxide single crystals implanted at room temperature with different fluences (1 × 1015-1 × 1016 cm -2) of europium ions. Rutherford backscattering channelling shows that for fluences above 5 × 1015 cm-2 the surface disorder level in the Al-sublattice reaches the random level. Implantation damage recovers fast for annealing in oxidizing atmosphere but even for the highest fluence we recover almost completely all the damage after annealing at 1300 °C, independently of the annealing environment (reducing or oxidizing). Annealing above 1000 °C promotes the formation of Eu2O 3 in the samples with higher concentration of Eu. The optical activation of the rare earth ions at room temperature was observed after annealing at 800 °C by photoluminescence and ionoluminescence. In Al 2O3 lattice the highest intensity line of the Eu 3+ ions corresponds to the forced electric dipole 5D 0 → 7F2 transition that occurs ∼616 nm. For the MgO samples the Eu3+ optical activation was also achieved after implantation with different fluences. Here, the lanthanide recombination is dominated by the magnetic dipole 5D0 → 7F1 transition near by 590 nm commonly observed for samples were Eu3+ is placed in a high symmetry local site. The results clearly demonstrate the possibility to get Eu incorporated in optical active regular lattice sites in wide gap oxides