富Pb的PZT铁电薄膜电性能异常

采用金属有机物热分解法制备了不同Ｐｂ过量的锆钛酸铅（ＰＺＴ）铁电薄膜。观测到Ｐｂ过量ＰＺＴ薄膜电滞回线束腰与Ｃ－Ｖ曲线四峰的异常现象,其异常程度随时间回剧。这是薄膜样品有界晶和界面上的ＰｂＯ２相所诱导的陷阱电荷对电畴产生钉扎的结果。陷阱电荷对电畴的钉轧程度与陷阱电荷的密度以及陷阱电荷与电畴的作用状况有关,通过改变晶界处的陷阱电荷的密度与分布可改变薄膜电性能的异常程度。     

不同极化态下有机铁电膜微观振动特性的AFM研究

借助原子力显微镜优异的空间分辨能力和锁相放大技术,实验研究了有机铁电薄膜在不同极化状态下的微观振动特性.负极化态时,薄膜表面振动与驱动电压呈线性且同相;而正极化态时,表面振动与驱动电压依然呈线性,但两者间存在180°相差.实验中清楚地观测到局域振动畴、非振动畴以及振动振幅相对较小的振动畴三者间的共存.本工作探讨了非活性铁电畴存在的可能性,并认为是陷阱电荷的箝制作用限制了铁电畴的活性.     

铅过量PLZT铁电薄膜的制备及其电学性质研究

采用Sol-Gel法,在Pt/TiO2／Si基片上制备了具有不同铅过量（0－20mol%)的PLZT铁电薄膜。分析了薄膜的晶相结构,研究了铅过量对PLZT铁电薄膜的介电性能和铁电性能的影响。结果表明,各薄膜均具有钙钛矿型结构,且各薄膜均呈（110）择优取向。PLZT铁电薄膜的介电性能和铁电性能随铅过量的变化而改变。铅过量为10mol%的薄膜具有最佳的介电性能和铁电性能。     

铅过量PLZT铁电薄膜的制备及其电学性质研究

采用Sol Gel法 ,在Pt TiO2 Si基片上制备了具有不同铅过量 (0— 2 0mol% )的PLZT铁电薄膜。分析了薄膜的晶相结构 ,研究了铅过量对PLZT铁电薄膜的介电性能和铁电性能的影响。结果表明 ,各薄膜均具有钙钛矿型结构 ,且各薄膜均呈 (110 )择优取向。PLZT铁电薄膜的介电性能和铁电性能随铅过量的变化而改变。铅过量为 10mol%的薄膜具有最佳的的介电性能和铁电性能。     

Pb^2＋与Al^3＋掺杂对SiO2薄膜电荷贮存性能的影响

较高的表面能是ＳｉＯ２薄膜产生亲水性并导致体内贮存电荷失稳的重要原因。极性Ｐｂ６２＋离子的掺入有效地降低了ＳｉＯ２薄膜的表面能，使表面趋于中性，增强了疏水性。此外，Ｐｂ＾２＋，Ａｌ＾３＋离子作为填隙式离子和替位式离的掺入较好地改善了ＳｉＯ２薄膜的网络结构并使其致密化，使样品在保持原有良好的负电荷存储性能基础上，又对称增增加了优良的正电荷贮存能力。     

多离子束反应共溅射技术制备（Pb,La）TiO3铁电薄膜及薄膜物化性能表征

研制了多离子束反应溅射技术并运用该技术在多种衬底上制备晶态（Ｐｂ，Ｌａ）ＴｉＯ３铁电薄膜。运用多种分析技术对铁电薄膜的物化性能进行了表征。发现在铁电薄膜的近表面有富铅层。测试了铁电薄膜的电滞回线、矫顽场、折射率、吸收系数等电学和光学参数。利用该技术可在较低衬底温度下在位制备组分可调、附着力强的外延或高度择优取向的铁电薄膜。     

铁电材料的极化疲劳:基本机理和最新进展

简要回顾了铁电材料中极化疲劳现象的基本机理和最新进展.详细地介绍了作者和其合作者最近创立的LPD-SICI模型(LPD-SICI是指极化翻转引起的电荷注入导致的局域相分离).LPD-SICI模型认为导致铁电材料中极化疲劳的主要原因是:在极化翻转早期形成的针状畴顶端的非屏蔽束缚电荷在电极-薄膜界面处会导致强烈的电荷注入(主要是电子),引起局域的焦耳热,最后在畴成核位置引发局域相分离.通过回顾过去几年在铁电材料电学极化疲劳方面实验研究的最新进展,得出LPD-SICI模型与过去三年中文献上发表的大多数实验观测相一致,并可以解释这些现象的起因.因此,极化翻转导致的局域相分离可能是各种类型铁电材料极化疲劳的共同起因.     

多场耦合下铁电薄膜非线性行为的畴变模型

铁电薄膜在外加力场,电场和温度场的作用下表现出明显的非线性,为了更好的描述这种现象,本文提出了一个热-电-力耦合场铁电薄膜下的畴变模型。该模型基于细观力学模型,认为电畴自由能的改变提供电畴翻转的动力,且180°电畴翻转由两步90°翻转构成。在本构关系中加入了铁电薄膜制备过程中产生的残余应变项,以区别于块体铁电材料,通过该模型计算出了铁电薄膜在不同外场下的响应,结果与实验和其他模型的结果较为符合。     

OTFTs结构与器件性能

在重掺杂的Si衬底上分别制备了底电极（Bottom—contact organic thin—film transistors，BCOTFYs）和顶电极（Top—contact organic thin—film transistors，TC—OTFYs）有机薄膜场效应晶体管，探讨了源、漏电极位置对器件性能的影响。结果表明，顶电极可以形成良好的欧姆接触，其器件的迁移率和开关电流比均高出BC—OTFYs器件三个数量级。研究了栅绝缘层的薄膜厚度对器件的电性能的影响。结果表明，在相同电压下，薄的绝缘层增大了沟道区域的电场，可积累更多的电荷，以填充更多的陷阱，使器件的场效应迁移率和工作电流得到了明显的提高。     

铁电薄膜纳米尺度畴分布及其生长机制

用溶胶-凝胶的方法制得(111)取向的PZT铁电薄膜,并喷涂于Pt(111)/Ti/SiO2/Si衬底上.用扫描力显微镜(SFM)的压电响应模式纳米级分辨率地观察到了几乎等间距或中间间距大于两侧的条状畴结构.这主要与晶粒和衬底间的应力应变有关.从这畴结构我们提出铁电畴形核和生长速率模型.其基本过程如下(1)由于薄膜和底电极间周期性的结构和成分起伏,致使畴结构在此相连处形核.(2)铁电畴横向生长至相临畴相遇,纵向生长至薄膜上表面.(3)在随后的过程中,由于单个畴间的能量差异致使横向生长再次启动.这些过程是连续的,难以正确的区分.     

溶胶—凝胶方法制备铁电薄膜及其力学性质的研究

本文介绍用溶胶-凝胶方法制备钛酸铅镧(PLT)铁电膜,采用划痕法测定PLT膜在Si基片上的附着力,并通过x射线衍射(XRD)测定在各种工艺条件下PLT薄膜的晶格畸变,并计算内应力。实验表明溶胶-凝胶方法的工艺因素对薄膜的力学性质有很大影响。通过控制溶液浓度,热处理温度及薄膜的厚度可得到附着力强,内应力小,品格畸变小的优质膜。     

Effects of excess Pb on structural and electrical properties of Pb(Zr0.48Ti0.52)O3 thin films using MOD process

Pb(Zr_0.48Ti_0.52)O₃ thin films at 20% excess Pb were synthesized on Pt/Ti/SiO₂/Si(100) substrates at different annealing temperatures by a metal-organic decomposition process. The microstructure of the PZT films was investigated by x-ray diffraction and atomic force microscopy. The composition of the films was characterized by Rutherford Backscattering Spectroscopy (RBS). These results showed that The PZT films have perovskite phase coexisted with PbO₂ phase. The PbO₂ phase mainly was formed by excess Pb which congregate at boundaries of crystalline grains during the annealing process and may be absorbed part of oxygen ion at normal sites, thus leading to an increase of oxygen vacancies in the PZT film. PbO₂ phase and oxygen vacancies act as pinning centres, which has an effect on the ferroelectric domain switching. This eventually resulted in an increase of fatigue rate in PZT films.     

Temperature and Current Dependent Matching Fields in?Superconducting NbN Film

Patterned superconducting thin films having a periodic array of submicrometric pinning centers have been of great interest due to their excellence for the studies of the vortex pinning mechanisms in the type-II superconductors. Square hole array has been fabricated over a micro-bridge 60 mm??60 mm of NbN thin film by electron beam lithography. Previous works have been carried out in Nb, Pb and Al thin films where the vortex pinning effect is assumed to be small. In this work, we study the matching pinning effect by the artificial hole array in superconducting NbN thin films. We observed the interplay between the vortex quantization and the artificial hole array. Magneto-resistance minima at integer matching fields up to five times of H ₁ (the first matching field corresponding to one vortex inside each hole) and fractional matching fields at 1/2H ₁, 3/2H ₁ and 5/2H ₁ have been observed.     

Preparation and characterization of chemically derived (Pb,La)TiO (3) thin films

Ferroelectric lead lanthanum titanate (PLT) thin films with composition varying from pure PbTiO(3) to PLT 25/100 (0 to 25 mol.% La) were prepared by spin-casting 0.25M solutions containing metallo-organic precursors of Pb, La, and Ti. The dielectric and ferroelectric properties of the thin (410-nm) films were characterized. The dielectric constants of the films varied from ~80 to ~690 for La contents varying from 0 to 25 mol%, respectively. Dissipation factors varied from ~0.03 to ~0.09 over the same compositional range. The temperature dependence of the dielectric properties was also studied to determine the effects of La content on the Curie point (T(c)). As expected, T(c ) was found to decrease with increasing La concentration. Coercive field and remanent polarization also decreased with increased La concentration.     

Effect of excess Pb in PbTiO<Subscript>3</Subscript> precursors on ferroelectric and fatigue property of sol–gel derived PbTiO<Subscript>3</Subscript>/PbZr<Subscript>0.3</Subscript>Ti<Subscript>0.7</Subscript>O<Subscript>3</Subscript>/PbTiO<Subscript>3</Subscript> thin films

A series of Pb_(1+x)TiO₃/PbZr_0.3Ti_0.7O₃/Pb_(1+x)TiO₃ (PTO/PZT/PTO) and PbZr_0.3Ti_0.7O₃ (PZT) thin films were prepared by a sol–gel method. Different excess Pb content (x) (x = 0, 0.05, 0.10, 0.15, 0.20) were added to the PbTiO₃ (PTO) precursors to investigate their effect on ferroelectric and fatigue properties of the PTO/PZT/PTO thin films. X-ray diffraction results show that the crystallization behavior of the PTO/PZT/PTO thin films is greatly affected by the excess Pb content (x) in PTO precursors. Topographic images show that the PTO/PZT/PTO thin films with excess Pb content x = 0.10 appears the densest and the most uniform grain size surface morphology. The ferroelectric and fatigue properties of the films correlate straightforwardly to the crystallization behaviors and excess Pb content (x) in the PTO precursors. The excess Pb content (x) in the PTO layers which acts as a nucleation site or seeding layer for PZT films affects the crystallization of the PTO layer and ultimately affects the perovskite phase formation of the PZT films. With the proper excess Pb content (x = 0.10–0.15) in the PTO precursors, the pure perovskite structure PTO/PZT/PTO thin films, with dense, void-free, and uniform fine grain size are obtained, and a well-saturated hysteresis loop with higher remnant polarization is achieved. Using an appropriate Pb content, the fatigue has been avoided by controlling the inter-diffusion and surface volatilization.     

Enhanced Flux Pinning Properties of BaZrO3-doped YBCO Films Grown by Pulsed Laser Deposition on LaAlO3(100) Substrates Decorated with Y2O3 Nanoislands

In this work, we intend to investigate the interaction between two types of nanoscaled artificial pinning centers and their pinning properties in YBCO thin films grown by pulsed laser deposition technique. The two types of artificial pinning centers were prepared in different processes, (1) Y₂O₃ nanoislands decorated on substrates prior to the deposition of YBCO thin film, and (2) BaZrO₃ nanoparticles self-assembled within YBCO matrix during the deposition of YBCO thin film. We compared the transport characteristics of the YBCO thin films containing these two types of artificial pinning centers with those of pure YBCO thin films grown on decorated substrates and BZO-doped YBCO thin films grown on undecorated substrates. It was found that these two types of artificial pinning centers, which are simultaneously present, acted constructively to enhance the pinning properties of YBCO thin films.     

不同电极形式对掺镧钛酸铅铁电薄膜的介电性能的影响

采用射频磁控溅射技术在Si(100) 基底和Pt/Ti/SiO2/Si(100)基底上生长了掺镧钛酸铅[(Pb0.9,La0.1)TiO3, PLT10]铁电薄膜.用X射线衍射技术(XRD)研究了PLT10薄膜结晶性能.使用光刻工艺在Si(100) 基底的PLT10薄膜上制备了叉指电极,测试了PLT10薄膜的介电性能.在室温下,测试频率为1kHz时,PLT10薄膜的介电常数为386.而采用相同工艺条件制备的具有平行电极结构的PLT10薄膜, 其介电常数为365.但利用叉指电极测试的PLT10薄膜的介电常数和介电损耗随频率的下降比利用平行电极测试的PLT10薄膜的快些.这是因为叉指电极结构引入了更多的界面态影响的缘故.     

The effect of different electrode structures on the dielectric properties of lanthanum-doped lead titanate ferroelectric thin films

Lanthanum-doped lead titanate [(Pb_0.9,La_0.1)TiO₃, PLT10] ferroelectric thin films were grown on Si(100) and Pt/Ti/SiO₂/Si(100) substrates by radio frequency (RF) magnetron sputtering. The crystalline properties of PLT10 films were studied by X-ray diffractometry (XRD). Photolithographic technique was applied to fabricate the interdigital electrodes on PLT10 thin films on Si(100) substrates. The dielectric properties of PLT10 thin films with different electrodes were measured. At room temperature and 1 kHz testing frequency, the dielectric constant of the PLT10 thin film with interdigital electrodes is 386. The dielectric constant of the PLT10 thin film fabricated under the same technological conditions with parallel plate electrodes structure is 365, while the dielectric constant and loss of the PLT10 thin film with interdigital electrodes are decreased faster than those of the film with parallel plate electrodes with increasing frequency. This is because more influences of interface state are introduced due to the interdigital electrode configuration. Translated from Journal of Functional Materials, 2006, 10(37): 1,554–1,556, 1560 (in Chinese)