| Bismuth layered structure ferroelectrics (BLSFs) thin films have been widely investigated recently. Among them, Bi3.15Nd0.85Ti3O12 (BNT),as a typical kind of layer-structured ferroelectrics, has attracted much attention due to its potential applications in nonvolatile ferroelectric random access memory (NvFRAM) devices.In this thesis, we fabricated BNT thin films by chemical solution deposition method on both Pt(111)/Ti/SiO2/Si(001) and TiO2(101)/ Pt(111)/Ti/SiO2/Si(001) substrates. The effects of the precursor solution concentration, annealing conditions and the propertiy of substrates on the morphology and orientation of grains in those films were addressed, based on the classical nucleation theory. And using Landau-Ginzburg thermadynamics theory, the hysteresis loops of first-order ferroelectric superlattices are simulated, by taking into acount the graded polarization and the surface effect. Moreover, the effects of the antiferroelectric coupling on the size effect of the system were investegated. The main results are as follows:The grain morphology of BNT thin films is mainly determined by the characteristics of the nucleation event; when crystallization occurs at a low temperature, thus the barrier heights for both the interface nucleation and the bulk nucleation can be surmounted, and the film displays microstructure with fine grains. In the opposite case, lower energy interface nucleation events dominate the thin film microstructure and the film is mainly columnar in nature.The grain orientation of BNT thin films are decided by both the nucleation and the grain growth. On the one hand, the c-axis-oriented-grain nucleation is favored due to its lower surface energy and the better mismatch with Pt. But the grains are randomly orientated when the nucleation is occurred in the bulk of films. On the other hand, the a-axis-oriented grains are favored owing to their fasted grain growth speed along the film normal. Anyway, a competition exists between the nucleation and grain growth in determining the film orientation. But for films grown on the seeding layer of TiO2, the low degree of c-aixs-orientation is obtained because the a-axis-oriented grains are favored in both the nucleation and the growth. While, a high degree of (117)-orientation is still obtained even when annealed under 700℃using the rapidly thermal annealing. This results from the fact that the TiO2 seeding layer helps the occurance of bulk nucleation, which favors the randomly oriented grains. Until the annealing with high temperature of 750℃and rapidly thermal annealing is adopted, BNT thin films with a high degree of a-axis-orientation can be obtained.The ferroelectric properties of BNT thin films, especially their ramnent polarization, has close relation with their orientation, i.e., the higher degree of a-axis-orientation, the stronger the remnant polarization. But at the same time, the property is also affected by the grain size, because it is more difficult to reorientate the polarization in the smaller grains by the applied electric field, and so the coercive field increases. For first-order ferroelectric superlattices, their loop patterns vary between typically antiferroelectric and typically ferroelectric depending on the thickness ratio, coupling constant, thickness and extrapolation length. The antiferroelectric coupling has a great effect on the phase transition of a bilayer. It is shown that the size-driven phase transition can't be observed in a ferroelectric bilayer in the case of strong antiferroelectric coupling.The innovations of the thesis are as follows:1. Study systematically the effects of fabrication conditions on the morphology of grains in BNT thin films;2. Study systematically the effects of fabrication conditions on the orientation of grains in BNT thin films and address the mechanism ;3. Put forward the opitimized fabrication conditions to get BNT thin films with excellent properties;4. Simulate the hysetesis loops of first-order ferroelectric bilayers or superlattices and their size effect, by taking into account the surface effect and polarization variation in component films.
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