C-Axis Current -Voltage Characteristics of Mesa Structures on Bi₂Sr₂CaCu₂O_8+δ Single Crystals Fabricated by a Simple Technique Without Photolithography

A simple technique is reported for fabricating the mesa structure on Bi₂Sr₂CaCu₂O_8+δ single crystal. In the patterning process, metal masks are used instead of photolithography and argon ion milling is applied to form the small mesa on the Bi₂Sr₂CaCu₂O_8+δ crystal surface. Real four-probe transport measurements are made on the mesa structure and typical c-axis current-voltage (I - V) characteristics of the intrinsic Josephson effect have been observed. The superconducting gap parameter can be extracted from the multi-branch structure in the I - V characteristics. Additionally, from the strong hysteresis in the I - V characteristics, the capacitance C_J of the unit intrinsic Josephson junction has been estimated to be 2.3pF, which is in good agreement with that evaluated from the geometric parameters of the unit junction between the two copper oxide layers.