Tilting of the top layer of graphoepitaxial metal-oxide multilayer thin film heterostructures

The mechanisms of tilt formation in the metal oxide multilayer heterostructures with graphoepitaxial (3DGE) growth mode were studied in the YBa₂Cu₃O_x–CeO₂–Y:ZrO₂–BaZrO₃ system fabricated by pulsed laser deposition on tilted-axes NdGaO₃ substrates. Every layer growing in the 3DGE mode demonstrates tilt of the small-index crystallographic plane set by surface features of the underlying layer, no matter the structure or mechanism of tilt formation in it. Introduction of a non-graphoepitaxial interface into the multilayer results in a corresponding change of tilt of the top layer. The reasons for such a change of the growth mode can be different: breach of graphoepitaxy at high tilt angles, seeding of grains of small size, or chemical interaction between neighboring layers. The epitaxial relations in the multilayer with unexpected tilt angles may be reconstructed taking into account changes of the growth step height and formation of interfaces with non-3DGE epitaxial relations. The presented results are important for analysis of the epitaxial heterostructures where 3DGE growth mode is possible, especially when trenches and slopes are patterned in some layers during fabrication of electronic devices.