Synthesis of BSCCO Single Crystal Whiskers for Terahertz EM Wave Oscillators

We prepared Bi₂Sr₂CaCu₂O_8+δ (BSCCO, Bi2212) and Bi_2-xPb_x Sr₂CaCu₂O_y (BPSCCO) single crystal whiskers from Bi_2+xSr_2-xCa₂Cu₂Te_0.5O_y and Bi_2-xPb_xSr₂ Ca₂Cu₂Te_0.5O_y precursors using a tellurium-doped method, respectively. X-ray diffraction patterns revealed that the resulting whiskers showed a single crystalline Bi2212 phase. Although the temperature dependence of the resistance in the ab-plane showed a superconducting transition at T = 84 K and 107 K, a transition along the c-axis was observed only at T = 84 K. This indicates the intergrowth of the Bi₂Sr₂Ca₂Cu₃O_10+δ (Bi2223) phase. The Pb- and Te-dual doping method suppresses the crystal growth of the BPSCCO whisker, and the superconductivity of the BPSCCO whisker is easily destroyed by annealing at 450°C in air. A mesa-type BSCCO intrinsic Josephson junction (IJJ) oscillator was fabricated with a single crystalline whisker. The current-voltage ( I-V) characteristics of the fabricated oscillator show a multibranch structure. The critical current is 14 mA at 4.2 K for a mesa structure ~ 300 μm in length and ~20 μm in width, which is higher than that previously reported for a whisker-based IJJ structure. Furthermore, a negative differential resistance in the I-V characteristics was observed below 40 K. A BSCCO whisker might be a potential candidate material for constructing an IJJ terahertz electromagnetic wave oscillator.