Single Cooper-pair tunneling junctions using high-T/sub c/ superconducting materials

We introduce the single electron (Cooper-pair) tunneling junctions using c-axis Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+d/ (Bi-2212) superconducting single crystal whiskers. Focused-ion-beam (FIB) etching patterned the Bi-2212 whiskers. The fabricated small stacked junctions have in-plane area S smaller than <1 /spl mu/m/sup 2/. The junctions showed current-voltage (I-V) characteristics with the periodic structure of current peaks. The stacking layered structure of Bi-2212 works as a multi-junction array which decreases the effective capacitance, C/sub /spl Sigma//=C/sub 0//N, where C/sub 0/ is the capacitance of the junction and N is the layer number of elementary junctions. The period of current peaks of I-V curves corresponds to the charging energy of the single Cooper pair, 2Ec (=e/sup 2//C/sub /spl Sigma//).