Transport critical current density in epitaxial Bi2Sr2CaCu2O8+x films: Effects of the substrate twinning

Epitaxial Bi2Sr2CaCu2O8+x films have been grown by the liquid phase technique on twinned LaGaO3 and untwinned SrTiO3 substrates. Crystallographic properties and transition temperatures are comparable, but the transport critical current density Jc depends dramatically on the substrate. Films grown on SrTiO3 have Jc comparable with single crystals, while films grown on LaGaO3 have Jc values extrapolated at 4.2 K in the 104-105 A cm-2 range. This effect is demonstrated to be a consequence of the presence of twinning domains in the substrate.