溶胶凝胶法制备PbTiO3薄膜的研究

利用ＩＲ、ＤＴＡ、ＴＧ、ＸＲＤ及Ｒａｍａｎ光谱等测试手段,研究了乙酰丙酮改性的Ｐｂ－Ｔｉ系统的溶胶凝胶过程。结果表明通过乙酰丙酮的改性可以得到稳定的溶胶前驱体,由此溶胶制备的薄膜在６００℃即形成完全晶化的钛酸铅薄膜。     

Texture Development, Microstructure Evolution, and Crystallization of Chemically Derived PZT Thin Films

Two solution-based methods, metallo-organic decomposition and sol—gel processes, were used to study the effects of precursor solution type on the microstructure evolution and texture development of oriented PZT films. Microstructure development and perovskite content are strongly dependent on the heating rate. Fast heating rate forms a dense fine-grained microstructure with (111) orientation. Intermediate-temperature pyrolysis followed by a fast heating rate forms clustered or island structures of submicrometer grains with (100) orientation. Intermediate-temperature pyrolysis followed by a very slow heating rate forms larger spherical rosettes with random orientations. Pt_5–7Pb is a (111) textured transient intermetallic phase that nucleates PZT(111) texture. PbO is a (001) textured layer compound that nucleates PZT(100) texture. The texture selection of PZT films is independent of precursor systems but sensitive to the film thickness especially when sol—gel precursors and oxidizing atmosphere are used. Correlation and comparison of oriented sol—gel and MOD PZT films with electrical properties are also made.     

Crystallization Behavior of Sol–Gel-Derived Strontium Barium Niobate Thin Films

The crystallization of sol–gel-derived strontium barium niobate (SBN) thin films on various substrates is enhanced by a two-step heating process. Also, SBN films with c -axis preferred orientation are obtained on MgO (100) substrates. The crystallized phase and the degree of orientation are dependent on crystallization temperature and film composition. The crystallization temperature required to form a single tetragonal tungsten bronze (TTB) SBN phase increases with an increase of Sr content due to the distorted SBN structure. However, in the case of the film on MgO substrate, the oriented crystallization which forms the single tetragonal phase occurs at a lower crystallization temperature than those of polycrystalline films because of lattice matching between the film and the substrate. Its optical and ferroelectric properties were also investigated. They vary depending on film composition, due to the effect of the distorted SBN structure.     

Role of Alumina Buffer Layer on the Dielectric and Piezoelectric Properties of PZT System Thick Films

Piezoelectric properties of screen‐printed thick films, 0.01Pb(Mg_1/2W_1/2)O₃–0.41Pb(Ni_1/3Nb_2/3)O₃–0.35PbTiO₃–0.23PbZrO₃ + 0.1 wt% Y₂O₃ + 1.5 wt% ZnO (PMW–PNN–PT–PZ+YZ) on alumina (Al₂O₃) buffer layers deposited on Si substrates, were studied. To improve piezoelectric properties of and integrate the PMW–PNN–PT–PZ+YZ thick films, the Al₂O₃ buffer layers on silicon (Si) substrates were used. The Al₂O₃ buffer layer on the Si substrate suppressed the pyrochlore phases of the piezoelectric thick films and prevented interdiffusion of Si and Pb. The PMW–PNN–PT–PZ+YZ thick films with 900 nm thick Al₂O₃ buffer layer showed piezoelectric properties such as P_r = 32 μC/cm², E_c = 25 kV/cm, and d₃₃ = 32 pC/N. These significant piezoelectric properties of our screen‐printed PMW–PNN–PT–PZ+YZ thick films by the Al₂O₃ buffer layers can be applied to functional thick film in many micro‐electromechanical system (MEMS) applications such as micro actuators and sensors.     

射频磁控溅射制备PZT铁电薄膜的工艺研究

在SiO2/Si基片上采用直流对靶溅射技术制备出Pt/Ti底电极;应用射频磁控溅射方法,利用快速热处理(RTA)工艺,制备出了具有良好铁电性能的Pb(Zr0.52Ti0.48)O3铁电薄膜.将样品进行10min快速热退火处理,退火温度700℃.测试分析表明:薄膜厚度比较均匀、表面基本平整、没有裂纹和孔洞、致密性好、薄膜样品的矫顽场强(Ec)为28.6kV/cm,剩余极化强度(Pr)为18.7μC/cm2,自发极化强度(Ps)为37.5μC/cm2,是制备铁电薄膜存储器的优选材料.     

聚合物在取向聚合物薄膜上的附生结晶研究进展

总结了近年来以取向聚合物为基底的聚合物附生结晶的部分研究成果,重点综述了聚合物附生结晶的机理及晶格匹配、链段规整度、结晶动力学、二次成核等因素对聚合物附生结晶的影响,并对其今后的发展进行了展望。     

Effect of Nb Doping on the Microstructure of Sol—Gel-Derived PZT Thin Films

Aliovalent Nb doping (<10 at.%) of sol—gel-derived lead zirconate titanate (PZT) thin films was investigated with the intention of improving the ferroelectric properties. Nb addition was found to significantly alter the perovskite crystallization by stabilizing the transient pyrochlore phase, resulting in the retention of pyrochlore second phases and an increase in the perovskite lateral grain size and columnarity. The occurrence and composition of Zr-rich (surface) pyrochlore phases were found to depend on Nb concentration, annealing temperature, and Pb content. The observed changes in ferroelectric and dielectric properties as a function of Nb dopant addition were found to be strongly influenced by microstructural effects and the occurrence of pyrochlore, and hence the intrinsic effects of Nb incorporation in the perovskite lattice could not be directly ascertained.     

Microstructure of Solution-Processed Lead Zirconate Titanate (PZT) Thin Films

Lead zirconate titanate (PZT) thin films with a composition near the morphotropic phase boundary (Zr/Ti = 53/47) were fabricated by spin deposition of an alkoxide-derived solution and annealed at 650°C for 30 min. A complex microstructure is observed in which micrometer-scale rosettes of the desired perovskite phase are surrounded by nanocrystalline (10 to 15 nm) grains of pyrochlore structure. Transmission electron microscopy (TEM) demonstrates that the perovskite rosettes—features of approximately circular cross section which grow rapidly within the confined conditions of the thin film—are single crystals despite being highly porous. Pockets of lead-deficient pyrochlore extend throughout the thickness of the film. The only effects of Nb (2%) doping on the microstructure are to increase the fraction of the perovskite phase and the perovskite grain size. Despite the highly irregular shape of the perovskite particles and the presence of some pyrochlore, reasonable ferroelectric properties are measured (spontaneous polarization P _s∼ 0.2 C/m²).     

Microstructural Studies on the Low-Temperature Crystallization Process of Strontium Bismuth Tantalate Thin Films

The preparation of strontium bismuth tantalate (SBT) thin films at low temperatures for electronic applications is at present the subject of intense study. However, the microstructural evolution of these films has not been extensively reported, despite its importance in the determination of the final properties of the film. In this work, we study SBT thin films with various nominal compositions obtained by the crystallization at 650°3C of spin-coated solutions on a silicon-based substrate. Both the formation of the perovskite phase and the evolution of the grains are analyzed, with special attention to the formation of platelet-like grains. A process of coalescence of initially round grains is proposed to explain the grain growth in this system. We also show that the use of a preannealing step inhibits the grain growth and, therefore, should be avoided. The role that the film thickness plays in the development of large grains is discussed.     

Phase and Texture Evolution in Chemically Derived PZT Thin Films on Pt Substrates

The crystallization of lead zirconate titanate (PZT) thin films was evaluated on two different platinum‐coated Si substrates. One substrate consisted of a Pt coating on a Ti adhesion layer, whereas the other consisted of a Pt coating on a TiO₂ adhesion layer. The Pt deposited on TiO₂ exhibited a higher degree of preferred orientation than the Pt deposited on Ti (as measured by the Full Width at Half Maximum of the 111 peak about the sample normal). PZT thin films with a nominal Zr/Ti ratio of 52/48 were deposited on the substrates using the inverted mixing order (IMO) route. Phase and texture evolution of the thin films were monitored during crystallization using in situ X‐ray diffraction at a synchrotron source. The intensity of the Pt₃Pb phase indicated that deposition on a highly oriented Pt/TiO₂ substrate resulted in less diffusion of Pb into the substrate relative to films deposited on Pt/Ti. There was also no evidence of the pyrochlore phase influencing texture evolution. The results suggest that PZT nucleates directly on Pt, which explains the observation of a more highly oriented 111 texture of PZT on the Pt/TiO₂ substrate than on the Pt/Ti substrate.     

Crystallization of Sol–Gel-Derived Barium Strontium Titanate Thin Films

Microstructural development of thin-film barium strontium titanate (Ba _x Sr_{1– x} TiO₃) as a function of strontium concentration and thermal treatment were studied, using transmission electron microscopy (TEM) and X-ray diffractometry (XRD). Thin films, ∼250 nm thick, were spin-coated onto Pt/Ti/SiO₂/Si substrates, using methoxypropoxide alkoxide precursors, and crystallized by heat-treating at 700°C. All films had the cubic perovskite structure, and their lattice parameters varied linearly with strontium content. Films with higher strontium concentrations had a larger average grain size. In situ TEM heating experiments, combined with differential thermal analysis/thermogravimetric analysis results, suggest that the gel films crystallize as an intermediate carbonate phase, Ba _x Sr_{1– x} TiO₂CO₃ (with a solid solution range from x = 1 to x = 0). Before decomposition at 600°C, this carbonate phase inhibits the formation of the desired perovskite phase.     

Mg掺杂对Ba0.5Sr0.5TiO3薄膜介电性能的影响

用醋酸盐和钛酸四丁酯为原料,采用sol-gel工艺在Pt/TiO/SiO/Si基片上制备了含有Mg元素的Sr0.5Ba0.5-xMgxTiO3薄膜,其退火处理温度为750℃.通过X射线衍射和扫描电镜分析技术研究了薄膜的相结构和形貌.采用美国HP Angilent 4294A阻抗分析仪测试了以Pt为底电极、Ag为上电极的MFM电容器的介电性能.实验结果表明:掺镁Sr05Ba05.xMgxTiO3薄膜较未掺杂的Ba05Sr0.5TiO3薄膜相对介电常数高、介电损耗低.介温谱表明在居里温度附近发生了弥散型相变,且居里温度有向低温方向漂移的趋势.     

The Dependence of the Effective Dielectric Constant of PbTiO 3 on the Surface Layer

Complex oxide thin films, such as ferroelectric thin films, are being widely used in various devices. However, the chemical composition and chemical bondings of the surface layer are usually different from those in the "bulk" region of the oxide thin films. The existence of the surface layer will certainly affect the properties, such as dielectric behavior, of the films. Departing from the effective medium theory, the dependence of the effective dielectric behavior of PbTiO 3 thin films on the surface layer has been analyzed by using the model we proposed. The effective dielectric constant of the thin film is proposed as the function of the dielectric constants of the expected compounds and the unexpected compounds in the surface layer, the content of the unexpected compounds compared with the expected compound in the surface layer, and the volume faction of the surface layer in the whole thin films. The surface layer deviating stoichiometry has a pronounced effect on the effective dielectric constant of the thin films.     

Influence of Anvil Properties on RDX Thin Layer Ignition Behavior

We report on a drop‐impact protocol that arrests sample radial flow to isolate how anvil properties influence ignition in a thin layer of RDX powder. To eliminate sliding friction as a probable heating mechanism, flow arrestment was provided by a waxed weighing paper that shielded the RDX layer from direct contact with the impact surfaces. RDX reaction sensitivity under bare and shielded conditions for the standard O1 hardened steel anvil was compared with that for two deformable anvil types: 1018 steel and C110 copper. Profilometer measurements of anvil deformation and paper impressions quantified anvil plastic work and final radial flow displacement. Post‐test particle analyses correlated particle size distribution to ignition results. Experiments indicated that the impact energy absorbed by the anvils was varied and inhibited ignition accordingly. For the standard anvil, ignition was not inhibited under flow arrestment, suggesting that significant radial sliding or flow is not essential for thin layer ignition.     

Annealing Temperature Effect on Bismuth Induced Crystallization of Hydrogenated Amorphous Silicon Thin Films

Silicon - In this work, we emphasis on the Bismuth induced crystallization of hydrogenated amorphous silicon (a-Si) thin films. 50&nbsp;nm of bismuth thin films are deposited by vapor...     

BiFeO3薄膜研究进展

BiFeO3是少数的在室温下同时具有铁磁性和铁电性的铁磁电材料之一,在信息存储、传感器和自旋电子器件等方面都有潜在的应用前景.本文通过对BiFeO3薄膜的结构、磁性起源、制备工艺和应用领域等方面的综述,提出并设计了水热法和仿生法这两种新的制备BiFeO3薄膜的湿化学方法,并展望了BiFeO3薄膜今后的研究和发展趋势.     

Effect of Zn, Sr, and Y Addition on Electrical Properties of PZT Thin Films

We have investigated methods to increase the efficiency of piezoelectric micromachined ultrasonic transducers (pMUTs). pMUTs are driven by a thin piezoelectric layer on a Si membrane. The efficiency of pMUTs can be increased using a film with better ferroelectric properties. We have used Zn, Sr, and Y doping on PZT-based thin films along the morphotropic phase boundary (MPB) composition to increase their piezoelectric properties. The results obtained were then extended to compositions on both sides of the MPB. The sol–gel method was used to prepare precursor solutions, which were then spin coated on a Pt(100)/Ti/SiO₂/Si substrate to prepare the PZT thin films. It was found that Zn and Sr together had the most significant effect on the ferroelectric properties in which a saturation polarization of 108 μC/cm² and remanent polarization of 54 μC/cm² were achieved.     

铁掺杂对TiO_2薄膜结晶和光诱导超亲水性的影响

采用溶胶-凝胶法制备了Fe_2O_3-TiO_2复合薄膜和复合粉末,采用X射线衍射(XRD)、高分辨扫描电镜(SEM)和接触角分析仪考察了Fe的掺杂对TiO_2薄膜的晶型、晶粒粒径及接触角的影响。结果表明,添加少量的Fe_2O_3不仅能有效地抑制TiO_2金红石晶型的产生,而且还能显著地抑制薄膜中TiO_2粒子生长。当Fe_2O_3的物质的量分数达到0.1%时,薄膜中粒子明显变小,且分布也变窄,锐钛矿TiO_2的晶粒粒径降低至未添加Fe_2O_3时的二分之一。随着Fe掺杂量的继续增加。金红石型TiO_2继续减少,但锐钛矿TiO_2的晶粒粒径却有少许增大。薄膜的亲水性与TiO_2粒子的晶粒粒径密切相关。在两种紫外光源照射下,薄膜与水的接触角都随着晶粒粒径的减少而明显变小。     

The Crystallization of Amorphous Aluminum Oxide Thin Films Grown on NiAl(100)

The crystallization of amorphous aluminum oxide thin films formed on NiAl(100) has been investigated using in‐situ low energy electron microscopy, low energy electron diffraction, and scanning tunneling microscopy. It is found that both the annealing temperature and annealing time play crucial roles in the crystallization process. A critical temperature range of 450°C–500°C exists for the crystallization to occur within a reasonably short annealing time. The initially uniform oxide film first becomes roughened, followed by coalescing into amorphous‐like oxide islands; further annealing results in the conversion of the amorphous oxide islands into crystalline oxide stripes. The density of the crystalline oxide stripes increases concomitantly with the decrease in the density of the amorphous oxide islands for annealing at a higher temperature or longer time.     

Two-Layer Crystallization of Amorphous YMnO3 Thin Films on Si (100) Substrates

During a rapid thermal annealing process at 850°C in a N₂ ambient, an as-deposited amorphous YMnO₃ thin film on Si (100) substrates was crystallized with two distinct layers. High-resolution transmission electron microscopy showed a top layer of c -axis-oriented YMnO₃ and a bottom layer of polycrystalline YMnO₃ in the 100-nm-thick YMnO₃ thin film. The abrupt change of the crystalline orientation from the c -axis-preferred orientation to the random orientation is caused primarily by high stress induced by the c -axis-oriented YMnO₃ layer. High-resolution X-ray diffraction showed that the c -axis-oriented YMnO₃/polycrystalline YMnO₃ structure effectively relieved the stress.