The surfaces of sputtered Cu3Ba2YO7 films on (001) SrTiO3 substrates were structurally and morphologically characterized by using atomic force microscopy and transmission electron microscopy. The former technique revealed 3 types of outgrowth with various shapes and heights between 2 and 200nm. Type-I had a cubic habit, type-II had a tabular habit, and type-III was an agglomerate with no particular shape. Some of the type-III outgrowths were located at the center of growth spirals, where a screw dislocation intersected the film surface. This suggested that, in Cu3Ba2YO7 films, these defects promoted the occurrence of each other. The surface outgrowths were identified by using high-resolution electron microscopy and electron diffraction. It was concluded that type-I was Y2O3, type-II was Y2O3 plus CuYO2, and type-III was Cu3Ba2YO7 plus CuO plus Y2O3. In contrast to type-I and type-II outgrowths, which were both epitaxially related to the surrounding Cu3Ba2YO7, the large type-III agglomerates consisted of epitaxial and non-epitaxial grains. Because it was found that the outgrowing non-epitaxial phases emanated from screw dislocations and from a,b-axis domain boundaries, it was suggested that both internal stresses and high interfacial energies promoted such outgrowths.

A.Catana, J.G.Bednorz, C.Gerber, J.Mannhart, D.G.Schlom: Applied Physics Letters, 1993, 63[4], 553-5