Self-patterned oxide nanostructures grown by post-deposition thermal annealing on stepped surfaces

We report here on the self-patterned growth of nanostructured epitaxial oxide thin films using a bottom-up approach. Different stepped (0001) sapphire surfaces have been used as templates to grow different nanostructured thin films of yttria-stabilized zirconia elaborated by a chemical solution deposition technique, namely sol-gel dip-coating. For such films, a morphological instability occurs during post-deposition thermal annealing that forces the film to split into isolated islands. Taking advantage of this effect, three distinct types of nanostructures have been produced depending on the step morphology of the substrate surface, and depending on the relative magnitude of the mean island diameter (D) and the mean terrace length (L). Flat-top islands, dome-shaped islands, tilted flat-top islands or self-organized arrays of nano-islands can be generated. Atomic force microscopy was used to observe nanostructures and quantitative characterizations of crystallographic and nanostructural aspects were carried out by high-resolution x-ray diffraction reciprocal space mapping.