First principles study of the interface between silicone and undoped/doped BaTiO₃

We investigate the local electronic structure and the surface adhesion strength of a silicone-BaTiO₃ (001) interface through first principles density functional theory (DFT) computations. A polydimethyl siloxane (PDMS) chain was used as a representative siloxane, and the adsorption of PDMS on both undoped as well as n-type (La at Ba site) and p-type (Mn at Ti site) doped BaTiO₃ (001) surfaces are considered. Our interface is modeled in a two dimensional periodical slab model framework and both the possible BaTiO₃ (001) surface terminations (i.e., the BaO- and TiO₂-terminations) are explicitly taken into account. Our calculations indicate that while both n-type and p-type dopants are expected to improve adhesion of silicone chains at the BaTiO₃ surfaces, the n-type doping is expected to result in an interface with a clean band gap and superior effective dielectric properties. p-type doping could lead to a metallic behavior in the near-interface regions through introduction of mostly unoccupied mid-gap states. Finally, the silicone bonding induced electronic perturbation on both the doped (001) facets of BaTiO₃ is analyzed using charge density redistribution analysis.