Preparation, Characterisation and Dielectric Properties of YBa₂Cu₃O_7-δ/ Insulator-Heterostructures

YBa2Cu3O7-delta/insulator/Au-heterostructure on SrTiO3 or LaAlO3 substrates were prepared to study the properties of the materials SrTiO3, BaTiO3 and CeO2. X-ray diffraction measurements in Bragg-Brentano geometry show c-axis-oriented growth for the superconductor and the insulators SrTiO3 and CeO2. Typical values for the rocking curve width of the different insulating films are between 0.4 degrees and 0.8 degrees. The highest breakdown fields are measured for the insulator SrTiO3 with +37.5 kV/mm and -8.8 kV/mm. The permittivity for CeO2 is independent of applied field and only weakly temperature dependent. This is in contrast to the perovskite type insulators, where the permittivity depends on temperature and field. The measured real- and imaginary- parts of the dielectric constant differ as a function of frequency (20 Hz - 1 MHz) from the bulk-materials for all three insulators. This behaviour can be explained with a resistance in series and a conductance parallel to the capacitance.