Thermal Spike and Displacement Damage Effects in BiSrCaCuO Thin Films by Ar Ion Beams

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Abstract
Superconducting BiSrCaCuO thin films containing both low-T c, 80 K phase and high-T c, 108 K phase material were irradiated with 100 keV Ar ions up to 4×1017 ions/cm2 at 10 K and 300 K. In-situ resistivity measurements revealed that in the early stage of Ar ion irradiation at 10 K the superconducting state of the films was maintained, but was destroyed after prolonged irradiation to a dose of 1×1015 ions/cm2. The normal-state resistivity of the high-T c phase increased with ion dose at a smaller rate than that of the low-T c phase. A thermal spike model was suggested in which the constituent atoms are thermally activated to rearrange themselves and form high-T c phase embryos under the irradiated conditions. The growth of the high-T c embryos occurred efficiently by subsequent annealing at 700∼730°C, improving the high-T c phase ratio markedly.