BTO/STO氧化物超晶格生长模拟及电学性能研究

【作者】 姚海军；

【导师】 罗佳慧；

【作者基本信息】 电子科技大学 ， 材料学， 2004， 硕士

【摘要】 本论文概述了超晶格广阔的应用前景,并阐述了BaTiO3/SrTiO3超晶格材料的特点与其研究的重要性。在试验过程中,使用激光分子束外延技术制备了不同结构的BaTiO3/SrTiO3超晶格薄膜,并对其结构和性能进行了研究。为了研究氧化物薄膜的生长过程,采用Monte Carlo方法对氧化物薄膜的生长过程进行了模拟。参考已有的生长模型,结合晶体理论和试验结果,建立了研究薄膜生长过程的模型,用Monte Carlo方法对薄膜的生长进行了模拟,结果表明在较低的沉积速率下,可以得到表面比较光滑的薄膜,并且在较低的沉积速率下,基片表面的缺陷对薄膜的生长影响不大。为了对BaTiO3/SrTiO3超晶格薄膜的结构进行表征,使用了反射式高能电子衍射仪RHEED、X射线衍射(XRD)、原子力显微镜(AFM)、X射线光电子能谱(XPS)等分析技术对薄膜的结构和成分进行了测试。其中RHEED振荡曲线表明薄膜为良好的二维层状生长,并且通过RHEED振荡曲线可以精确的得到薄膜的层数。从不同基片温度的超晶格薄膜的AFM分析表明,在基片温度为380℃到470℃的温度范围内,薄膜具有原子级光滑表面。对BaTiO3/SrTiO3超晶格薄膜样品的内部成分进行分析,发现在BaTiO3层与SrTiO3层之间,Ba粒子和Sr粒子有一定的互扩散,并且降低基片温度可以减小粒子间的互扩散。使用真空蒸发技术,在BaTiO3/SrTiO3超晶格薄膜上蒸镀金电极,并用导电胶引出引线来测量薄膜的电学性能。在薄膜的制备工艺过程中,氧气压对薄膜的电学性能有较大的影响,过高或过低的氧气压都会影响薄膜的电学性能。调制周期小的超晶格薄膜具有较大的介电常数,并且具有高的居里温度,因而可以通过调节薄膜的调制周期得到耐高温的、高介电常数的薄膜材料。更多还原

【Abstract】 In this paper, we discussed the widely applied foreground of superlattices and expatiated the characteristic of BaTiO3/SrTiO3 superlattice with important research value. The superlattice were got by the method of Laser Molecular Beam Epitaxy(L-MBE) and characteristic of structure and capability were studied in details. We also used Monte Carlo method to simulate the process in order to study the growth process of oxide thin films.The model of the early stage of thin film growth had been instituted based on the experiment results and the growth process of thin films had been simulated using Monte Carlo method by using the theory of crystal growth. The results indicated that the thin films deposited at low growth speed were relatively smoother than those deposited at high growth speed. When the growth speed was lower, the disfigurement on the substrate had little influence to thin films.We used reflection high–energy electron diffraction (RHEED), X-ray Diffraction(XRD), Atomic Force Microscopy(AFM),X-ray photoelectron spectroscopy (XPS) etc to study the micro-structure and composition of thin films. The plots of RHEED showed that the thin films were atomically smooth and in-plane-oriented and we could acquire the numbers of lays in the thin films; when the temperature of substrate was at the range of 380℃ to 470℃,the thin films had atomically smooth. Through the composition analysis of thin films, we found that there were inter diffusion between BaTiO3 layer and SrTiO3 layer, and we could reduce diffusion when the temperature of the substrate was reduced.Using the vacuum evaporation technology, we vaporized the gold on films as electrode to measure the capability of dielectrics. The results made it clear that the pressure of oxygen were very important to the film’s capability of dielectrics even that we could not obtain good capability of electrics if the pressure of oxygen was litter lower or litter higher. The dielectric constant and Curie temperature of BaTiO3/SrTiO3 superlattic increased with decreasing the stacking periodicity. By modulating the stacking periodicity, the high temperature enduranced and high <WP=6>dielectrics of thin films were obtained successfully.更多还原