GRAPHOEPITAXY OF CEO2 ON MGO AND ITS APPLICATION TO THE FABRICATION OF 45-DEGREES GRAIN-BOUNDARY JOSEPHSON-JUNCTIONS OF YBA2CU3O7-X

We communicate a detailed study of the epitaxial growth of CeO2 on MgO . The key feature of the growth is the dependence of the in-plane orie ntation of the CeO2 epitaxial layer on the MgO surface morphology. Ato mic force microscopic (AFM) measurements, x-ray analyses, as well as h igh-resolution transmission electron microscopy (HRTEM) investigations reveal that on rough substrates a cube-on-cube growth of CeO2 on MgO occurs while on smooth substrates the CeO2 unit cell is rotated around the surface normal by 45 degrees with respect to the MgO unit cell wh en the deposition rate is low (similar to 0.3 Angstrom/s) during the f irst stages of growth. This growth mechanism can be used for a defined fabrication of 45 degrees grain boundaries in the CeO2 layer by contr olling the surface roughness of the MgO substrate. This report demonst rates that these 45 degrees grain boundaries may be used to fabricate YBa2Cu3O7-x Josephson junctions. (C) 1995 American Institute of Physic s.