Controlling self-assembled perovskite-spinel nanostructures

We report a discovery that self-assembled perovskite-spinel nanostructures can be controlled simply by selecting single-crystal substrates with different orientations. In a model BiFeO3-CoFe2O4 system, a ( 001) substrate results in rectangular-shaped CoFe2O4 nanopillars in a BiFeO3 matrix; in contrast, a (111) substrate leads to triangular-shaped BiFeO3 nanopillars in a CoFe2O4 matrix, irrespective of the volume fraction of the two phases. This dramatic reversal is attributed to the surface energy anisotropy as an intrinsic property of a crystal.