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Bi2Sr2CaCu2O8+δ (Bi-2212) stacks of intrinsic Josephson junctions were fabricated by an acid-treatment process from inside a single crystal. The surrounding acid-treated product is a transparent material, BiOCl. During the process, an optical adhesive (NOA-61) was used to fix a piece of the crystal on a glass substrate and to coat the surface of the sample. The current-voltage characteristics of the stacks at T = 77 K exhibited large hystereses and multiple branches with voltage spacings of approximately 2-3 mV. Under an external microwave field in the frequency range of 2-18 GHz, clear Shapiro steps were observed at voltages with multiples of (h/2e)frf. In addition, the thermal cycling properties of the critical current (Ic) were investigated. No apparent degradation of the Ic was observed during repeated thermal cycling between 300 and 77 K.
Date of Publication: June 2011