Anthony C. Sutorik

Assembly of thin Film Dielectrics by Sequential Adsorption Reactions of Unilamellar Inorganic Colloids

Several layered inorganic materials (e.g. KCa 2 Nb 3 O 10 , KTiNbO 5 , and CsPb 2 Nb 3 O 10 ) were prepared and their alkali cations exchanged by in aqueous acid. A fraction of the interlayer protons of HCa 2 Nb 3 O 10 and HTiNbO 5 can be replaced by tetra-n-butylammonium (TBA + ), by reaction with TBA + OH. Intercalation of a sufficient amount of TBA + causes complete exfoliation, and single, nanometer-thick sheets of these materials are thus obtained. By sequential adsorption of these two-dimensional colloidal polyanions and polymeric cations, monolayer sheets of layered perovskites can be stacked on silicon surfaces to give thin films of any desired thickness. The layered materials, the exfoliated colloids, and the thin film multilayers on silicon were studied by X-ray diffraction, transmission electronic microscopy (TEM), ellipsometry, and atomic force microscopy (AFM). The dielectric properties of the related bulk materials were measured, and are also discussed.