Formation of high T_c, superconducting films by laser induced fragments

Formation of YBaCu oxide films by pulsed-laser sputtering of superconducting Y₁Ba₂Cu₃O_y pellets at 1.064 μm was performed. At laser energy densities from 0.6 to 0.8 J/cm², the films formed on (100) MgO substrate showed superconductivity (T_c = 81 K, T₀ = 79 K) and highly preferred orientation of the c-axis after post-annealing. The regrowth of amorphized highly implanted layers of the superconducting films has also been investigated. For the amorphous layer produced with implantation of 120 keV O⁺ to a dose of 1 × 10¹⁶/cm², both the superconductivity and preferred orientation of the c-axis were recovered by furnace annealing in flowing O₂ gas at 900 and 940 ° C for 1 h. For annealing at 800 and 850 ° C, on the other hand, the amorphous layer is recrystallized and the layer has a normal metallic conductance but no preferential growth. Results suggest that solid phase epitaxial regrowth of O⁺ ion-implanted amorphous layer occurs only at temperatures higher than a critical temperature between 850 and 900° C.