The Fabrication Of La Doped Bi₄Ti₃O₁₂ Thin Films And Multilayer Thin Films By Sol-gel Process And Their Ferroelectric Properties

(Bi4-xLax)Ti3O12 (BLT) film has been investigated extensively for the application in the ferroelectric random access memories (FRAMs). But the development of the FRAMs is limited for its lower capacity than the dynamic random access memories (DRAMs). The key to improve the capacity of FRAMs is to improve the remnant polarization of the thin films. Therefore, the research for the thin films with high remnant polarization is an important work.In this paper, we found the crystal structures, surface morphology and ferroelectrics properties of BLT thin films were greatly affected by the baking temperatures during sol-gel processing. At lower baking temperature, the (117)-orientation in the BLT thin film was preferred. However, with the increasing of the baking temperature, the (117) diffraction peak became weaker. In addition, the surface morphology of the films changed from rodlike to platelike. The ferroelectrics properties were measured and it was found that the BLT thin film has the largest remnant polarization (2Pr) 28.4C/cm2 at a baking temperature of 250.The enhancement of remnant polarization was also observed in artificially multilayered (Bi3.25La0.75)Ti3O12(BLT)/Bi4Ti3O12(BT) films The multilayer was prepared on platinum coated silicon substrate by chemical solution deposition. The multilayered film with a stacking periodicity of 60 nm BLT/30nm BT shows a remnant polarization (2Pr) of 61C/cm2, which is much higher than those of the single-phase films. In addition, the multilayered films show a fatigue-free character.