Crystal Orientation Control of Bismuth Layer-Structured Dielectric Films Using Interface Layers of Perovskite-Type Oxides

Abstract

Thin films of SrBi 4 Ti 4 O 15 , a kind of bismuth layer-structured dielectrics (BLSDs), were prepared on platinized silicon wafers buffered by perovskite-type oxide interface layers, (100)LaNiO 3 /(111)Pt/TiO 2 /(100)Si and (001)Ca 2 Nb 3 O 10 -nanosheets/(111)Pt/TiO 2 /(100)Si, by chemical solution deposition (CSD). The Ca 2 Nb 3 O 10 nanosheets were supported on a (111)Pt/TiO 2 /(100)Si substrate by dip coating using an aqueous dispersion, while (100)LaNiO 3 was prepared by CSD. The (00 l ) planes of BLSD crystal were preferentially oriented on the surface of both substrates, which is caused by suitable lattice matching between the a -( b -)axis of BLSD and perovskite-type oxide layers. The film deposition on (001)Ca 2 Nb 3 O 10 nanosheets yielded (001)-oriented BLSD films with higher crystallinity and smaller fluctuation in the tilting angle of the (001)BLSD plane than those on the (100)LaNiO 3 interface layer. The dielectric constant (ε r ) of (001)-oriented SrBi 4 Ti 4 O 15 film on (001)Ca 2 Nb 3 O 10 -nanosheets/(111)Pt/TiO 2 /(100)Si substrate was approximately 190, which was significantly stable against the change of frequency and bias voltage compared with that of the randomly-oriented SrBi 4 Ti 4 O 15 film.