Synthesis of BSCCO Single Crystal Whiskers for Terahertz EM Wave Oscillators

We prepared Bi2Sr2CaCu2O8+delta (BSCCO, Bi2212) and Bi2-xPbxSr2CaCu2Oy (BPSCCO) single crystal whiskers from Bi2+xSr2-xCa2Cu2Te0.5Oy and Bi2-xPbxSr2Ca2Cu2Te0.5Oy 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 Bi2Sr2Ca2Cu3O10+delta (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 degrees 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 similar to 300 mu m in length and similar to 20 mu m 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.