Structure control in atomic scale of relaxors with morphotropic phase boundary composition

(1) Pb(Sc1/2Nb1/2)O3/PbTiO3超晶格薄膜及其介电性能的合成采用脉冲激光沉积（PLD）技术在SrTiO_3（001）衬底上合成了高取向Pb(Sc_<1/2>Nb_<1/2>)O_3 （PSN）和PbTiO_3 （PT）超晶格薄膜。SrRuO_3沉积在衬底上作为电介质测量的底电极层。用x射线衍射（XRD）方法对薄膜的取向和结构进行了表征。用XRD观察了超晶格的清晰反射，并根据超晶格的XRD谱线计算了超晶格的周期、相关长度和嵌合度。在102 ~ 105 Hz的频率范围内，室温下介电常数实部约为350。(2)在过渡金属氧化物薄膜中观察到电场诱导的电阻开关我们发现，在各种过渡金属氧化物薄膜中，电场诱导的极性非挥发性电阻开关几乎以相同的方式发生。这一结果表明，与人们普遍认为的相反，钙钛矿锰矿并不是这种现象的特殊化合物。这也表明电阻开关不是由每个样品的详细电子结构决定的，而是由更一般的来源决定的，例如晶体缺陷。

(1)Syntheses of super lattice thin films of Pb(Sc1/2Nb1/2)O3/PbTiO3 and dielectric propertiesHighly oriented Pb(Sc_<1/2>Nb_<1/2>)O_3 (PSN) and PbTiO_3 (PT) super-lattice thin films are synthesized on single-stepped SrTiO_3 (001) substrates by pulsed laser deposition (PLD) technique. SrRuO_3 is deposited on the substrate as a bottom electrode layer for dielectric measurements. The orientation and structure of the films are checked by X-ray diffraction (XRD) method. Clear super-lattice reflections are observed by XRD and the period of super-lattice, the correlation length and the mosaicity are calculated from XRD profiles of the super-lattice. Real part of the dielectric constant is about 350 at room temperature in the frequency range of 102〜105 Hz.(2)Electric-field-induced resistance switching observed in transition-metal-oxide thin filmsWe show that polarity-dependent, nonvolatile resistance switching by electric field occurs in the thin film of various transition-metal oxides in almost the same manner. This result indicates that contrary to the general acceptance, perovskite manganite is by no means a special compound for this phenomenon. It is also suggested that the resistance switching is not dominated by a detailed electronic structure of each sample, but dominated by a more general origin, e.g., crystalline defect.