A Reproducible Approach of Preparing High-Quality Overdoped Bi_2Sr_2CaCu_2O_8+\delta Single Crystals by Oxygen Annealing and Quenching Method

We report a reproducible approach in preparing high-quality overdoped Bi_2Sr_2CaCu_2O_8+\delta (Bi2212) single crystals by annealing Bi2212 crystals in high oxygen pressure followed by a fast quenching. In this way, high-quality overdoped and heavily overdoped Bi2212 single crystals are obtained by controlling the annealing oxygen pressure. We find that, beyond a limit of oxygen pressure that can achieve most heavily overdoped Bi2212 with a T_\rm c\sim63 K, the annealed Bi2212 begins to decompose. This accounts for the existence of the hole-doping limit and thus the T_\rm c limit in the heavily overdoped region of Bi2212 by the oxygen annealing process. These results provide a reliable way in preparing high-quality overdoped and heavily overdoped Bi2212 crystals that are important for studies of the physical properties, electronic structure and superconductivity mechanism of the cuprate superconductors.