Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+/spl delta// 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 Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+/spl delta// intrinsic Josephson junction. In this paper, we report a simple technique for fabricating the Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+/spl delta// 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 Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+/spl delta// crystal surface. Real four-probe transport measurements are made on the Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+/spl delta// 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 strung hysteresis in the I-V characteristics, the capacitance C/sub J/ 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 lagers.