Displacement Damage Effects and Related Phase Changes of Ar-Ion-Irradiated BiSrCaCuO System Superconducting Thin Films

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Abstract
BiSrCaCuO thin films of 0.5 µm thickness containing mainly the high-T c phase were irradiated with 100 keV Ar ions up to 5×1017 ions/cm2 at 10 K or 300 K. The irradiated thin films were considered to consist of a heavily damaged surface layer and an underlying partly displaced crystalline layer. The transition temperature T c of the films decreased initially with increasing Ar ion dose and converged at about 63 K for doses larger than 1×1017 ions/cm2. By a subsequent annealing below 800°C, the T c recovered up to 98 K. The relative X-ray diffraction intensity of the high-T c phase reached a maximum upon annealing at 700∼730°C. During the annealing, the heavily damaged or amorphous surface layer recrystallizes and regrows into better quality high-T c phase particles with concomitant formation of the thermodynamically stable Ca-free phase at this low temperature range.