Self-assembled metal oxide bilayer films with "single-crystalline" overlayer mesopore structure

Self-assembled metal oxide bilayer films having a single-crystalline overlayer mesopore structure is presented. The preparation of metal oxide films with nanometer-scale periodicity and solid-state functionality by sol-gel processing promises the resulting systems for materials science and ease of underlying templating processes. Such films with iso-oriented domains corresponding to a periodically ordered array without grain/domain boundaries could be regarded as mesophase single crystals. The uniaxial orientation of sol-gel-derived films with nanometer-scale periodicity is predominantly caused by the fact that the adhesion of the fragile organic-inorganic nanocomposite to the substrate surface is strong, impeding the nucleation of a biaxially oriented mesostructure as well as grain-boundary motion during film formation. Such bilayer films also offer the opportunity to exploit the combination of different physicochemical properties, and thus to design functional nanodevices.