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

Abstract
YBa₂Cu₃O_7-δ/insulator/Au-heterostructures 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° and 0.8°. 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.