Thickness Effect on (La_0.26Bi_0.74)_2Ti_4O_11 Thin-Film Composition and Electrical Properties

Highly oriented (00l) (La_0.26Bi_0.74)_2Ti_4O_11 thin films are deposited on (100) SrTiO_3 substrates using the pulsed laser deposition technique. The grains form a texture of bar-like arrays along SrTiO_3 \langle 110\rangle 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)_4Ti_3O_12 and TiO_2 components above a critical film thickness. Otherwise, the phase decomposes into the random mixture of Bi_2Ti_2O_7 and Bi_4Ti_3O_4 spherical grains in thinner films. The critical thickness can increase up to 440 nm as the films are deposited on LaNiO_3-buffered SrTiO_3 substrates. The electrical measurements show the dielectric enhancement of the multi-components, and comprehensive charge injection into interfacial traps between (La,Bi)_4Ti_3O_12 and TiO_2 components occurs under the application of a threshold voltage for the realization of high-charge storage.