Solid-phase epitaxial crystallization of complex oxides in nanoscale complex geometries*

Lateral crystallization of the model perovskite oxide SrTiO₃ from an amorphous precursor can be seeded by selected areas of the surface of a patterned SrTiO₃ (001) single-crystal substrate. The crystallized SrTiO₃ exhibits a rotating lattice microstructure in which the crystallographic orientation evolves continuously as a function of the lateral crystallization distance. Complementary synchrotron x-ray nanobeam diffraction imaging and high-resolution TEM studies measured the rotation rate resulting from crystallization at 550 °C was 50° per μm of lateral crystallization. Key features, including the rotation rate and the direction of the rotation, were reproduced in each of the many lithographically patterned seeds. The results of structural characterization studies are consistent with a model in which the rotation results from a high concentration of dislocations, on the order of 1 per 10 nm of crystallization distance, with a non-random population of Burgers vectors. The nucleation of dislocations with the preferred Burgers vector occurs due to stress near the amorphous-crystalline interface arising from the large volume difference (16%) between amorphous and crystalline SrTiO₃. The development of the rotating lattice microstructure has the potential to enable the creation of complex oxides in stress and orientation configurations not available through other epitaxial growth methods.