TUNNELING ANOMALIES IN BI2SR2CACU2O8-DELTA BI2SR2YCU2O8-DELTA/BI2SR2CACU2O8-DELTA PLANAR JUNCTIONS/

We have prepared Cu2O8-delta/Bi2Sr2YCu2O8-delta/Bi2Sr2CaCu2O8-delta (2 2 1 2/2 2 Y 2/2 2 1 2) planar heterojunctions (trilayer structures) u sing an in situ d.c.-sputtering process at high oxygen pressures onto (0 0 1) SrTiO3 substrates. Bi2Sr2YCu2O8-delta films (semiconducting-li ke) 10 and 12 nm thick were used as artificial barriers. Composition a nd structure of the barrier and the superconducting electrodes are ent irely compatible which allows epitaxial growth of the entire heterostr ucture. Gap-like structures of about 30 mV have been determined from t unnelling characteristics of the junctions. Linear conductance backgro unds as well as Zero Bias Anomalies (ZBA) are reported and discussed i n detail. (C) 1997 Elsevier Science Ltd.