Single crystal growth of Bi2212 with different Bi/Sr ratio for terahertz waves emitters

The Bi-based copper oxide high-temperature superconductor Bi₂Sr₂CaCu₂O_8+δ (Bi2212) has a nonstoichiometry composition expressed as Bi_2+xSr_2-xCaCu₂O_8+δ. We consider that the disorder of the insulating layer due to this nonstoichiometric composition (Bi/Sr) affects the CuO₂ layer and consequently changes in the superconducting transition temperature and the in-plane residual resistance. The intrinsic Josephson junctions (IJJs) constructed in Bi2212 have been thought to be affected by a crystallographic disorder. For the application of Bi2212 single crystals to terahertz wave emitters (Bi2212-THz emitters) based on IJJs, we evaluated the disorder mainly from the viewpoint of crystal structure. Specifically, we prepared single crystals of Bi2212 with different Bi/Sr ratio and subsequently the oxygen was controlled by post annealing. And the physical properties of the crystals have been examined by using X-ray techniques. We also study the device characteristics of Bi2212-THz emitters made by different ratio of (Bi/Sr) and the obtained results are compared at this moment. We will discuss these characteristics in details in the meeting.