EUROPIUM DIFFUSION ENHANCEMENT IN LINBO3 IRRADIATED WITH GEV NICKEL IONS - INFLUENCE OF THE DAMAGE MORPHOLOGY

The influence of the damage induced by GeV nickel ion irradiations on europium diffusion in LiNbO3 single crystals was investigated. For thi s purpose, 10.8 MeV/u Ni-58 ion irradiations were performed at room te mperature in LiNbO3 samples at fluences in the range 2.0 x 10(11)-1.2 x 10(12) ions cm(-2). The damage resulting from these irradiations dep ends on both the electronic stopping power (dE/dx)(e) and the velocity of the incident ions. Two kinds of damage morphology have been eviden ced: (i) amorphous continuous tracks for (dE/dx)(e) > 10 keV nm(-1); ( ii) discontinuous tracks or isolated defects for (dE/dx)(e) < 10 keV n m(-1). After irradiation the samples were implanted with 5.0 x 10(16) Eu cm(-2) at 70 keV and then annealed in air in the range 700-1100 deg rees C. Transmission electron microscopy observations exhibit both the continuous tracks and the extended defects induced by the high energy irradiation. Rutherford backscattering spectrometry results show that below or above the threshold of 10 keV nm(-1) the enhancement of euro pium diffusion in LiNbO3 seems to depend, mainly, on the damaged volum e.