Low-temperature annealing effect of as-grown Bi-Sr-Ca-Cu-O thin films on superconducting property and the c-axis lattice constant

As-grown crystallized Bi₂Sr₂Ca₁Cu ₂O_x phase films were prepared on MgO(100) substrates by rf magnetron sputtering. The as-grown film showed the T_c onset of 92 K and the T_c end of 82 K. By annealing in the furnace at 480°C after deposition, superconducting property and the c-axis lattice constant varied with atmosphere during annealing. The film after annealing in air at 480°C exhibited the highest superconducting transition with the T _c onset of 93 K and the T_c end of 85 K. The T_c onset increased when the c-axis lattice constant was increased, suggesting that the T_c onset increases with decreasing the oxygen content of the film.