EPITAXIAL-GROWTH OF SRTIO3 YBA2CU3O7-X HETEROSTRUCTURES BY PLASMA-ENHANCED METALORGANIC CHEMICAL-VAPOR-DEPOSITION/

We report heteroepitaxial growth of SrTiO3 on YBa2Cu3O7-x/LaAlO3 subst rates by plasma-enhanced metalorganic chemical vapor deposition. X-ray diffraction results indicated that SrTiO3 films were epitaxially grow n on a (001) YBa2Cu3O7-x surface with [100] orientation perpendicular to the surface. The film composition, with Sr/Ti molar ratio in the ra nge of 0.9 to 1.1, was determined by Rutherford backscattering spectro metry and energy dispersive spectroscopy. The thickness of the SrTiO3 films is 0.1-0.2 mum. The epitaxial growth was further evidenced by hi gh-resolution transmission electron microscopy and selected area diffr action. Atomically abrupt SrTiO3/YBa2Cu3O7-x interface and epitaxial g rowth with [100]SrTiO3\\[001]YBa2Cu3O7-x were observed in this study. The superconducting transition temperature of the bottom YBa2Cu3O7-x l ayer, as measured by ac susceptometer, did not significantly degrade a fter the growth of overlayer SrTiO3. The capacitance-voltage measureme nts showed that the dielectric constant of the SrTiO3 films was as hig h as 315 at a signal frequency of 100 KHz. The leakage current density through the SrTiO3 films is about 1X10(-6) A/cm2 at 2-V operation. Da ta analysis on the current-voltage characteristic indicated that the c onduction process is related to bulk-limited Poole-Frenkel emission.