TUNNELING CHARACTERISTICS OF EPITAXIAL YBA2CU3O7-X Y2O3/YBA2CU3O7-X PLANAR TYPE JUNCTIONS/

We deposited YBa2Cu3O7-x/Y2O3/YBa2Cu3O7-x heterostructures by a dc/rf sputtering process at high oxygen pressures on (001) SrTiO3 substrates . The deposition conditions of Y2O3 are completely compatible with tho se of YBa2Cu2O7-x. The crystal structure of Y2O3 provides a close latt ice match with YBa2Cu3O7-x, which results in high quality epitaxial tr ilayers with no foreign phases in the structure. Both bottom and top Y Ba2Cu3O7-x layers are superconducting above 90 K. The thicknesses of t he intermediate artificial Y2O3 layers range from 3 to 5 nm. Tunneling measurements on these planar junctions exhibited an anisotropic gap s tructure without zero bias anomalies. Gap structures at 9.6 K are clea rly seen at about 20 and 5 mV bias voltages. These values are discusse d considering the contributions from both ab-plane and quasiparticle t unneling processes.