SWIFT HEAVY-IONS IN INSULATING AND CONDUCTING OXIDES - TRACKS AND PHYSICAL-PROPERTIES

Damage induced in several oxide materials by swift heavy ions is presented. The discussion is based on results obtained on the following materials [Y3Fe5O12, AFe12O19 (A = Ba, Sr), BFe2O4 (B = Ni, Mg, Zn), ZrSi2O4, SiO2 quartz, Al2O3, high T(c) superconductors (YBa2Cu3O7-delta and Bi2Sr2CaCu2O8)] which have been irradiated by ions with atomic number ranging between 6 (C-12) and 92 (U-238) and energies between 0.05 GeV and 6 GeV. The damage cross section A has been deduced using several physical characterisations like Mossbauer spectrometry, saturation magnetisation measurements, channeling Rutherford backscattering, infrared absorption and electrical resistance measurements. Depending on the material and on the value of the electronic stopping power (dE/dx) the damage cross section varies between 10(-17) and 10(-12) CM2. Using medium and high resolution transmission electron microscopy and chemical etching of the latent track, an electronic stopping power evolution of the damage morphology has been observed leading to the definition of an effective radius R(e) of the latent track which can be linked to the damage (amorphous) cross section A by the relation R(e) = square-root A /pi. Moreover there is a direct correlation between these values and the damage morphology: for R(e) > 3 nm the latent tracks are long and cylindrical, conversely for R(e) < 3 nm the damage is inhomogeneous along the latent track. The effect of the irradiation temperature, of the crystallographic orientation, of the initial electrical resistivity and of the oxygen stoichiometry will be presented. In opposition to what has been usually believed it will be shown that alumina (Al2O3) is indeed sensitive to the electronic stopping power. Moreover the velocity of the incident ion has a direct influence on the damage production: the lower the velocity, the higher the damage.