外延BiFeO3薄膜的TEM显微结构表征

外延BiFeO3薄膜中丰富的结构与特殊的性能一直是近年来研究的热点.显微结构的研究不仅可以帮助人们进一步认识BiFeO3的结构信息,还可以帮助人们深入了解BiFeO3结构与性能间的关系,开拓新的应用领域.本文利用球差校正高分辨透射电子显微镜对外延在LaAlO3过渡层/Si基底上的BiFeO3薄膜进行研究.通过原子尺度的定量分析,在应力状态复杂区域观察到类菱方相、应力释放后恢复的菱方相以及拉应力状态下c/a值小于1的类菱方相,并在该区域观察到109°铁电畴,且畴间存在4.4°的畸变夹角.还观察到比较大的c/a比.     

肿瘤热疗用Fe3O4磁性纳米粒的制备及表征

用化学共沉淀法制备用于肿瘤磁流体热疗的Fe3O4磁性纳米粒子并对其进行表征。运用透射电子显微镜、X射线衍射分析、扫描电子显微镜、能谱分析及图像分析等技术进行特性研究;在高频交变磁场下观察Fe3O4纳米磁流体的体外升温情况。制备的Fe3O4磁性纳米粒子属尖晶石型铁氧体、圆形,粒径20nm左右。其不同浓度的磁流体在高频交变磁场下可升温至37℃～56℃。     

LaTiO3外延薄膜的显微结构与电学性能研究

本文利用脉冲激光沉积技术在LaAlO₃(100)和SrTiO₃(100)衬底上生长了LaTiO₃薄膜,利用高分辨X射线衍射和透射电子显微术对薄膜的显微结构进行了系统表征,利用霍尔效应测量系统对薄膜的电学性能进行了研究。XRD结果表明在两种衬底上生长的LaTiO₃薄膜均为单晶薄膜,SrTiO₃衬底上的薄膜具有更高的结晶度。透射电镜显微结构表征的结果显示,LaTiO₃薄膜在两种衬底上均实现了外延生长,SrTiO₃衬底上的薄膜具有更少的晶格缺陷,薄膜与衬底之间的界面也更平直和明锐。薄膜I-V曲线测量的结果表明SrTiO₃衬底上的LaTiO₃薄膜具有更低的电阻率。两种薄膜显微结构和电学性能的优劣主要源自于薄膜与衬底之间的晶格失配大小,更小的界面失配有利于高质量薄膜的外延生长。     

薄膜的截面TEM样品制备

薄膜材料的厚度仅为微米量级或者更薄，对其微结构的研究十分困难，许多表征方法难以采用。透射电子显微分析（TEM）是薄膜材料微结构研究最重要的手段之一。尽管采用TEM平面样品研究薄膜的微结构在样品制备方面相对容易，但由于薄膜依附于基材生长，且通常具有择优取向和柱状晶生长等微结构特征，因而采用截面样品从薄膜生长的横断面进行观察和研究，可以得到更多的材料微结构信息。但是薄膜的TEM截面样品制备过程较为繁杂，难以掌握。已有的文献主要介绍了Si基片上生长薄膜的TEM截面样品制备方法，对金属基片薄膜截面样品的制备方法介绍不多。     

核-壳结构Fe3O4@C磁性纳米颗粒的制备及其结构表征

本文利用水热法制备了直径100 nm的核-壳结构Fe3O4@C磁性纳米颗粒.利用TEM(透射电子显微镜)、XRD(X射线衍射仪)技术对其形貌、成份及微观结构进行了分析,利用VSM(振动样品磁强计)对样品的宏观磁性进行了表征.研究结果表明,所制备的Fe3O4@C磁性纳米颗粒呈现核-壳结构,壳碳层的厚度约为15 nm,分散性良好且尺寸均匀,样品的饱和磁化强度为28 emu/g.Fe3O4@C磁性纳米颗粒在生物技术和医学领域具有广泛应用前景.     

三氧化二铁外延薄膜的制备及贯穿位错表征

氧化物薄膜中贯穿位错的类型和密度对其物理与化学性质具有重要影响。本文利用脉冲激光沉积技术在Al₂O₃(0001)和SrTiO₃(111)衬底上分别生长了α-Fe₂O₃外延薄膜，并利用X射线衍射、原子力显微镜和透射电子显微术对不同温度下生长的薄膜其相结构、结晶度、表面形态和位错类型等进行了系统的表征。结果表明：生长温度对Al₂O₃衬底上薄膜的质量影响很小，而对SrTiO₃衬底上薄膜的质量影响显著，Al₂O₃衬底上薄膜的结晶度和表面平整度普遍优于SrTiO₃衬底上的薄膜；Al₂O₃衬底上薄膜中的贯穿位错为■刃型不全位错，而SrTiO₃衬底上薄膜中的贯穿位错不仅包含■刃型不全位错，还有■混合型全位错。     

一种制备纳米Fe3O4的新方法及其磁性能研究

在正丙醇–水体系中,以NaOH为沉淀剂,用共沉淀法制备了纳米Fe3O4粒子,并用TEM和XRD对其进行了表征。考察了制备过程中工艺参数对Fe3O4颗粒大小的影响,并对影响机理进行了探讨。结果表明:纳米Fe3O4的平均粒径约为15nm;其饱和磁化强度可达73.34Am2/kg,比用水热法(42Am2/kg)和共沉淀法(60Am2/kg)制备的Fe3O4纳米粒子的要高。     

Fe_3O_4磁性纳米颗粒的制备及性能表征

以Fe_2(SO_4)_3·6H_2O,FeSO_4·4H_2O和NH_3·H_2O为原料,采用化学共沉淀法制备Fe_3O_4磁性纳米颗粒,并通过XRD、FTIR、TEM和VSM手段,研究了反应温度对其结构、形貌和磁性能的影响。结果表明:制备的Fe_3O_4磁性纳米颗粒表面包裹了一层有机物质,呈球形,大小均匀,平均粒径在13nm左右,分散性好,饱和磁化强度Ms最大值可达53.38A·m~2·kg~(–1),且反应温度70℃时其磁性能最佳。     

Preparation and characterization of thin films of MgO,Al2O3 and MgAl2O4 by atomic layer deposition

MgO, Al₂O₃ and MgAl₂O₄ thin films were deposited on silicon substrates at various temperatures by the atomic layer deposition (ALD) method using bis(cyclopentadienyl)magnesium, triethylaluminum, and H₂O and were characterized systematically. High-quality polycrystalline MgO films were deposited for a substrate temperature above 500°C, and amorphous thin films were deposited around 400°C. The deposited Al₂O₃ and MgAl₂O₄ thin films were characterized as amorphous in structure. Applicability of ALD to complex oxides is discussed.     

快速退火对钛酸铋薄膜微结构和铁电性的影响

采用MOCVD与快速退火工艺,制备高度择优取向的Bi4Ti3O12铁电薄膜.运用x射线衍射术分析薄膜材料的结构,x射线显微分析仪测量薄膜材料的组分,并通过电滞回线的测量,研究快速退火对Bi4Ti 3O12薄膜结构和铁电性的影响.     

Fe3O4/P(St-AL)磁性微球的制备和复合微相结构

适当修饰磁性氧化铁粒子,并采用种子聚合法将苯乙烯和丙烯醛等单体的共聚控制在磁性氧化铁粒子表面,制备出内核是Fe3O4外壳为聚苯乙烯的复合微球.这种微球是一种既具有磁响应性,表面又含有反应性基团(醛基)的功能性复合微球.如果在其表面连接酶、抗体、亲和素等生物活性物质,即可制得高效、易分离的生物反应器.本文研究了Fe3O4/P(St-AL)磁性复合微球的制备及微相结构,考察了影响该微球粒径、磁响应性和表面特性的有关因素.     

外延BiFeO_3薄膜的温度特性

基于Landau-Devonshire唯象理论,采用等效衬底晶格常数的方法,并拟合了磁刚度系数的温度函数,对多铁性外延BiFeO3薄膜的铁电性和磁性进行了研究。结果表明,70nm厚薄膜的磁化强度在10～731℃先增加后减小,在371℃时有最大值64569A/m,随膜厚的增加磁化强度的极值减小;自发极化、c轴晶格常数随膜厚的增加而减小,同一厚度薄膜随温度的升高自发极化强度减小;压电常数、相对介电常数随温度升高而增大,随膜厚增加而增加。     

Preparation and gas-sensing properties of α-Fe2O3 thin films

Haematite (α-Fe₂O₃) thin films are prepared by two different chemical vapor deposition (CVD) processes: the atmospheric pressure CVD (APCVD) and the plasma enhanced CVD (PECVD). The films are analyzed by x-ray diffraction and scanning electron microscopy; their gas-sensing properties are also investigated. Experimental results show that APCVD α-Fe₂O₃ films are highly sensitive and selective to smoke while PECVD films are highly sensitive and selective to alcohol. A certain amount of quadrivalent metal in the films has an effect on their sensitivity and selectivity to gases. It is found that the films will “break down” under certain conditions.     

Magnetic flux pinning in epitaxial YBa2Cu3O7−δ thin films

The influence of microstructure on the critical current density of laser ablated YBa₂Cu₃O_7−δ thin films has been examined. Scanning tunneling microscopy was used to examine the morphologies of YBa₂Cu₃O_7−δ films and the morphology data were then correlated with measurements of the critical current density. The films were found to grow by an island nucleation and growth mechanism. The critical current densities of the films are similar to those of films with screw dislocation growth, indicating that screw dislocation growth is not necessary for good pinning. The data suggest that the critical current density in applied magnetic field may be higher in films with higher densities of growth features.     

LixMn2O4 thin films characterization by X-ray,electrical conductivity and XANES

The spinel Li_xMn₂O₄ thin films were prepared by a new sol–gel route. The X-ray diffraction analysis confirmed the crystal structure with formation of high quality spinel at temperature of 800 °C. All the samples shown a Arrhenius type behavior in the electrical conductivity (σ), metal–insulator transition in low temperatures and decrease in the activation energy for high lithium concentration, indicating that the Fermi's level increased. When the pure spinel was formed the σ shown the maximum and the X-ray absorption near edge spectroscopy results shown a jump in the relative intensity of the O K-edge and Mn L_2,3-edges.