| Perovskite-type ferroelectric thin films have received great attention as one kind of functional materials over the years. Because of the ferroelectric, dielectric, pyroelectric and nonlinear optical properties, perovskite-tpye ferroelectric thin films show good application prospect in microelectronics, optoelectronics and some other fields. Among the ferroelectric thin films, Bismuth-based films have been widely studied and considered as promising materials to take the place of lead-based ones for the purpose of environmental friendly. Currently, the research of Bismuth-based films is mainly on oxides with a Bi layered structure, which show a significant anisotropy and limit their range of application to some extent. Therefore, it is of great significance to study the perovskite-type Bi-based oxides.In this dissertation, two Bi-based perovskite-type films have been used to do some researches. One is Nao.5Bio.5Ti03(NBT) thin film, and the other one is BiAlO3(BAO) thin film. First, the low-temperature dielectric properties of NBT thin film with heat treatment in N2atmosphere has been investigated, then the growth processes of BAO thin film have been discussed to provide some experimental supports for the further study. The detailed research work and experimental results are shown below:(1) NBT thin films have been prepared on LaNiO3-coated substrate by sol-gel method and the effect of heat treatment on the structure and morphology has been investigated. The NBT films annealed at700℃show the best crystalline quality and film quality. Parts of them are treated in N2atmosphere at450℃for2h, donating as NBT-N2. Compared with the NBT film, NBT-N2film exhibits a different dielectric response, which indicating a Debye-like relaxation.(2) In order to study the different phenomenon in the dielectric response of the NBT-N2thin film, the temperature dependence of dielectric characteristic has been measured in the temperature range from100to400K. The relaxation observed in this temperature range demonstrates that there are two thermally activated processes in NBT-N2film. Analysis on the complex permittivity in Cole-Cole plots indicates that the dielectric response follows the modified Debye model.(3) The first attempt of preparing BAO thin films has been made by using chemical solution deposition (CSD). The influence of annealing temperature on structures of BAO films has been studied. The results show that the BiA103phase is observed in the films annealed below500℃. With the annealing temperature increased, BiA103decomposes to form the BiaAl4O9phase along with the Bi24Al2O39and Bi2O3, and the film quality becomes worse. In order to improve the crystalline quality, the effect of post-annealing on structures of films has been analyzed. But the results display that post-annealing neither improves the film crystalline quality nor inhibits the impurity phase.(4) The first attempt of preparing Bi-Al-O thin films has been made by using atomic layer deposition (ALD). The influence of post-annealing on structures of Bi-Al-O films has been investigated. It is found that different substrates show different effects of induction on film growth and BiA103phase is only observed below500℃. Study on the film section morphology indicates that the thickness of Bi-Al-O ternary oxide films is less than the calculation one from ALD growth per cycle of binary oxide films, which may be associated with the different growth mechanism. |
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