Superconducting HgBa2CaCu2Oy thin films growth on NdGaO3, SrTiO3, LaAlO3 and Y-ZrO2 substrates

Superconducting HgBa2CaCu2Oy (Hg-1212) films have been fabricated on (110) NdGaO3, (100) SrTiO3, (100) LaAlO3 and (100) Y-ZrO2 substrates by a two-step process. Good reproducible superconducting properties, zero resistance temperatures (T-c) > 115 K and critical current density (J(c)) > 4000 MA/m(2) at 77 K in zero field, are obtained. X-ray diffraction patterns indicate that the films have an epitaxial structure with the c-axis perpendicular to the surface. Scanning electron microscopy measurements show a layered growth structure with square and octagonal grains on the Hg-1212 film surfaces. (110) NdGaO3 is demonstrated to be a good substrate for growing the Hg-cuprate thin films. A lower superconducting transition temperature is observed in films deposited on Y-ZrO2 substrates, which can be attributed to variations of the microstructure in the films. (C) 1999 Elsevier Science B.V. All rights reserved.