Optical and structural properties of MeV erbium implanted LiNbO3

LiNbO₃ single crystals have been implanted with 2.0 or 3.5 MeV Er ions with fluences between 2.0 X 10¹⁴ and 7.5 X 10¹⁵ cm^-2 and annealed at temperatures between 500 and 1060 ³C in a wet oxygen atmosphere. Photoluminescence spectroscopy, Rutherford backscattering spectroscopy, and secondary-ion-mass spectrometry have been used to study the influence of the annealing treatment on the optical activity of the Er ions, the crystal structure of the implanted LiNbO₃ layer, and the depth distribution of the Er ions, respectively. The as-implanted, amorphized LiNbO₃ already emits the characteristic photoluminescence (PL) of Er³⁺ around 1.53 µm. Annealing for 1 min at 500 °C causes recrystallization of the amorphized layer by columnar solid-phase epitaxial regrowth from the substrate. The PL intensity increases by more than one order of magnitude on annealing at 500°C and the PL lifetime rises from 1.65 to 2.85 ms. In contrast, much longer annealing times and a much higher temperature are necessary to remove the columns and restore the perfect lattice but do not further improve the optical properties. Up to an Er concentration of 0.12 at. % no concentration quenching effects are noticed. MeV implantation-doped samples show the same optical spectra as those doped during growth from the melt.