Role of Nd/Ba substitution on the growth mode and on the structural properties of Nd-rich Re-1(NdxBa2-x)Cu3O7-delta (Re = Nd, Y) thin films

Thin films of the superconducting Nd1+xBa2-xCu3O7-delta (NBCO) and Y-1(NdxBa2-x)Cu3O7-delta (YNBCO) compounds have been deposited by dc magnetron sputtering and diode high pressure oxygen sputtering, Different techniques. including scanning tunneling microscopy, atomic force microscopy, X-ray diffraction and transmission electron microscopy (TEM) have been used to study the film microstructures and the surface morphology. It is shown that the Nd/Ba exchange promotes a 2D heteroepitaxial growth in the case of the NBCO films deposited on (1 0 0) SrTiO3 substrates, with a suppression of the characteristic 3D spirals structures. On the contrary in YNBCO the Nd/Ba exchange does not provide a driving force for the suppression of screw-dislocations. since spirals or towers originated by screw and half loop dislocations are observed on the surface. TEM reveals that anti-phase boundaries are eliminated during the growth of NBCO films thanks to the Nd/Ba exchange while this mechanism is not operating in the case of YNBCO films. (C) 2002 Elsevier Science B.V. All rights reserved.