Thickness Effect on (La _0.26 Bi _0.74 ) ₂ Ti ₄ O ₁₁ Thin-Film Composition and Electrical Properties

Abstract

Highly oriented (00l) (La0.26Bi0.74)2Ti4O11 thin films are deposited on (100) SrTiO3 substrates using the pulsed laser deposition technique. The grains form a texture of bar-like arrays along SrTiO3 ⟨110⟩ directions for the film thickness above 350 nm, in contrast to spherical grains for the reduced film thickness below 220 nm. X-ray diffraction patterns show that the highly ordered bar-like grains are the ensemble of two lattice-matched monoclinic (La,Bi)4Ti3O12 and TiO2 components above a critical film thickness. Otherwise, the phase decomposes into the random mixture of Bi2Ti2O7 and Bi4Ti3O4 spherical grains in thinner films. The critical thickness can increase up to 440 nm as the films are deposited on LaNiO3-buffered SrTiO3 substrates. The electrical measurements show the dielectric enhancement of the multi-components, and comprehensive charge injection into interfacial traps between (La,Bi)4Ti3O12 and TiO2 components occurs under the application of a threshold voltage for the realization of high-charge storage.