Bi2Sr2CaCu2O8+δ intrinsic Josephson junctions fabricated by a simple technique without photolithography

Due to the roughness in the surface of the crystal sample, it is hard to use photolithography in the patterning process of the Bi2Sr2CaCu2O8+δ intrinsic Josephson junction. In this paper, we report a simple technique for fabricating the Bi2Sr2CaCu2O8+δ intrinsic Josephson junctions. In the patterning process, metal masks are used instead of photolithography and argon ion milling is applied to form a small mesa on the Bi2Sr2CaCu2O8+δ crystal surface. Real four-probe transport measurements are made on the Bi2Sr2CaCu2O8+δ intrinsic junctions and typical current-voltage characteristics with multi-branch structure have been observed, from which the superconducting gap parameter can be extracted. Additionally, from the strong hysteresis in the I-V characteristics, the capacitance CJ of the unit intrinsic Josephson junction can be estimated, which is in good agreement with that evaluated from the geometric parameters of the unit junction between the two copper oxide layers.