溶胶-凝胶法制备铁电薄膜的研究进展

溶胶-凝胶法是制备铁电薄膜的一种重要方法.综述了溶胶-凝胶法制备铁电薄膜的原理、工艺过程、特点,以及采用此方法制备出的某些材料的铁电性能.最后指出,溶胶-凝胶法制备铁电薄膜工艺仍需优化和改进,薄膜的质量亟待提高,以适应器件的要求.     

压电传感器材料的铁电特性研究

本文采用溶胶-凝胶工艺制备了不同Mn离子掺杂浓度的PZT薄膜.研究了不同掺杂浓度对压电传感器薄膜铁电特性的影响.试验结果表明当Mn离子含量较少时,Mn在PZT中主要表现施主掺杂特性,薄膜铁电性能提高;而当浓度增大时,薄膜性能降低.     

集成铁电器件中的关键工艺研究

对集成铁电器件中的关键工艺进行了研究,采用改进的溶胶-凝胶(Sol-Gel)法制备了高品质、(110)择优取向的锆钛酸铅(PZT)铁电薄膜,成功的利用离子束刻蚀(IBE)、反应离子刻蚀(RIE)和湿法腐蚀方法对PZT薄膜进行了刻蚀加工,采用正胶剥离和干法刻蚀工艺实现了金属铂(Pt)电极图形,为集成铁电器件的实现提供了良好的工艺基础.     

O.9Pb(Mg1/3Nb2/3)O3-O.1PbTiO3功能铁电薄膜的制备及其电性能研究

利用溶胶凝胶(sol-gel)技术制备Pb(Mg1/3Nb2/3)O3-PbTiO3(PMNT)铁电薄膜,研究了不同的溶剂对溶胶的配制和溶胶稳定性的影响,得到了可以长期稳定放置的溶胶;采用热重分析和差热分析的方法研究了凝胶的热解过程,确定了420℃为溶胶的热解温度,750℃为合理的结晶温度;以Pt/Ti/Si(100)为衬底,成功地制备了0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3铁电薄膜.通过X射线衍射分析了热处理温度对薄膜相的影响.通过高倍显微镜研究了薄膜的表面形态,通过ZT-Ⅱ型铁电参数测试仪对PMNT薄膜进行了铁电性能测试.测试结果表明,制备的PMNT铁电薄膜为具有完全钙钛矿相的弛豫性PMNT铁电薄膜,薄膜无裂纹,致密性好,其剩余极化和矫顽场分别可达到2.5μC/cm2和45kV/cm.     

退火制度对PZT铁电薄膜性能的影响

铁电薄膜的性质对于硅基MEMS器件有重要的影响,鉴于此本文尝试通过改善退火工艺以提高PZT薄膜的铁电和压电性质.采用溶胶凝胶法,在Si/SiO2/Ti/Pt衬底上制备了PZT铁电薄膜.实验中,采用一次退火工艺和每层退火工艺制备了两种PZT薄膜,采用XRD对薄膜的晶体结构进行分析,通过C-V和I-V特性的研究发现,每层退火工艺有助于提高PZT薄膜的C-V性质,并降低漏导电流.     

溶胶—凝胶法在塑料光学元件上的应用

溶胶—凝胶法是制备薄膜的一种独特的方法。它特别适宜于塑料光学元件。给出了制备的方法以及工艺要点。     

溶液法高质量外延薄膜助力新型复杂氧化物研究

目前普遍用于外延薄膜生长的物理气相沉积技术在复杂氧化物外延薄膜制备工艺,存在工艺探索周期长、生长窗口窄、参数稳定性低等困难。为此,中国科学院深圳先进技术研究院李江宇教授课题组,发展了适用于(1-x)BiTi(1-y)/2 FeyMg(1-y)/2 O3-(x)CaTiO3(BTFM-CTO)体系室温多铁固溶体的溶液法大面积外延薄膜制备工艺。该工作充分体现了溶胶凝胶法简单快速、成本低廉、成分调控均匀灵活等特点,在复杂氧化物外延薄膜研究及应用方面展现出巨大的潜力和优势,并易于与工业生产相结合,助力提升新型复杂氧化物材料器件化的发展速度。     

基于石英基底的PZT薄膜制备研究

研究了在石英基底上制备PZT薄膜,通过在石英基底上制备氮化硅沉积层来改善PZT薄膜质量。运用PECVD技术在石英基底上制备氮化硅沉积层,使用溶胶-凝胶法在沉积层上制备锆钛酸铅(PZT)薄膜,并对PZT薄膜的性能进行了表征。氮化硅沉积层的厚度选为500 nm,PZT薄膜的制备厚度选为1μm,对PZT薄膜的晶向、漏电流、介电性能和铁电性能进行了表征,结果表明在拥有氮化硅沉积层的石英基底上能够制备出性能优良的PZT薄膜。     

基于激光多普勒技术的PZT薄膜压电性能测试研究

应用基于激光多普勒技术的微小形变分析方法,并引入数字锁相技术,成功实现了PZT(Pb(Zr,Ti)O₃)铁电薄膜的压电性能测试。对商用压电陶瓷在小信号激励下的压电性能测试表明,数字锁相技术的引入能有效抑制系统噪声,并提高激光多普勒系统的位移检测分辨率,使其达到皮米量级。此外,研究了用溶胶-凝胶技术和溶胶-电雾化技术制备得到的PZT薄膜的电压-位移曲线和压电位移"蝴蝶线",实验结果表明:在5 V直流偏置下测得两种方法制备得到的PZT薄膜的d₃₃压电系数分别为218.7 pC/N和215.8 pC/N,相应的标准偏差分别为12.7和28.6。     

溶胶-凝胶法制备WO3气致变色薄膜

以钨粉和双氧水为主要材料,采用溶胶-凝胶法制备了WO3气致变色薄膜,研究了WO3薄膜的结构和气致变色性能,结果表明用此种方法制备的WO3薄膜具有良好的气致变色特性.     

Dynamics of space and polarization charges of ferroelectric thin films measured by atomic force microscopy

Retention behavior and local hysteresis characteristics in Pb(Zr(0.52)Ti(0.48))O(3) (PZT) thin films on Pt electrodes have been investigated by electrostatic force microscopy (EFM). A sol-gel method is used to synthesize PZT thin films and drying conditions are carefully explored over a wide range of temperature. Decay and retention mechanisms of single-poled and reverse-poled regions of the ferroelectric thin films are explained by space charge redistribution. Trapping behavior of space charges is dependent on the nature of interface between ferroelectric thin films and bottom electrodes. Local measurement of polarization-electric field curves by EFM shows inhomogeneous space charge entrapment.     

Characterization of self-assembling isolated ferroelectric domains by scanning force microscopy

Lead zirconate titanate (PZT) thin films were prepared by a sol–gel process on platinized Si substrate. Their microstructure and surface morphology were characterized by XRD and Scanninn Force Microscopy. Phase transformation of the prepared PZT films from pyrochlore to ferroelectric was observed by XRD and PFM (piezoresponse force microscopy), respectively. Self-assembling nano-structured ferroelectric phases are fabricated by solution deposition technique followed by the controlling kinetics of the transformation. Complex structures of ferroelectric domains in the isolated ferroelectric phases were found in the furnace annealed PZT films in the temperature range of 400–500°C. Single ferroelectric domain structure in the isolated ferroelectric phases could be found in thinner PZT films and used to study the size effect of laterally confined ferroelectric domains.     

An automated setup for studying thin ferroelectric films by the thermal-noise method

Determination of the initial permittivity (the permittivity in a weak electric field—a field that is much lower than the coercive field) of thin ferroelectric films is the most important problem in studying such objects. For this purpose, the thermal-noise method is a convenient tool. In this case, in contrast to the bridge method, a measuring voltage that can create a significant field in a sample is not applied to it, but a thermalnoise voltage that depends on the film capacitance is measured across a load resistor, which is connected in parallel to the specimen. Below, an automated setup using the LabVIEW package is described. The technique was first applied to studying thin films. A significant difference between the results of measuring the permittivity of thin films by the bridge and thermal-noise methods has been revealed.     

聚苯胺/纳米SnO2复合材料的表征及其氨敏特性

为了提高聚苯胺的灵敏性和稳定性,通过溶胶-凝胶法中的PANI前驱体法、浸渍-提拉法制备了聚苯胺/纳米SnO2复合材料粉末及其薄膜元件,利用FT - IR、XRD、SEM等分析手段对其进行了表征,并研究了SnO2/An摩尔比、氨气浓度对复合材料气敏性的影响,及其薄膜元件的长期稳定性.结果表明:随n( SnO2)/n(An)的增加,PANI衍射峰强度逐渐降低,且复合材料的团聚情况减轻;复合材料对500 ppm(1 ppm=10-6)氨气的灵敏度随n(SnO2)/n(An)的增力加呈现减小-增大-减小的趋势,当n(SnO2)/n(An) =0.8时,灵敏度达到最大,为16.0.不同薄膜元件的灵敏度均随氨气浓度的升高而增大,且对低浓度氨气也具有较好地灵敏性.     

硅基铁电微声学器件中薄膜残余应力的研究

采用基底曲率法测量了硅基铁电微声学器件中各层薄膜的残余应力情况,通过调节热氧化的二氧化硅层的厚度,优化了微声学器件中复合膜的残余应力,得到平整的振膜结构,提高了器件的可靠性和成品率。     

Imaging of ferroelectric thin films by X-ray photoemission electron microscopy (XPEEM)

We performed X-ray photoemission electron microscopy (XPEEM) measurements at the Nanospectroscopy Beamline of the synchrotron light source ELETTRA, Trieste, Italy, to demonstrate the principal possibility of imaging ferroelectric thin films by low-energy photoelectrons. Due to the insulating properties of ferroelectric films, severe surface charging was the major experimental challenge to overcome. This was achieved by grounding an array of gold inter-digital electrodes (with 5 microm blank intervals between them) deposited on top of the films. The images taken with BaTiO(3) films revealed 50-100 nm-sized holes (material discontinuities) on the surface, an observation confirmed by high-resolution scanning electron microscopy (HRSEM). Finer details, e.g. a granular structure, which has been resolved with HRSEM, could not be observed in the XPEEM images. Our measurements indicate that despite some residual charging, a 50 nm lateral resolution can be achieved in XPEEM measurements with ferroelectric films.     

The charge storage characteristics of PZT nanocrystal thin film

Lead zirconate titanate (PZT) films have been extensively investigated for many applications: the nonvolatile memory devices based on their remarkable ferroelectric properties, the microelectromechanical system (MEMS) based on their piezoelectricity as well in sensors as in actuators. In this paper, we inject charges into PZT thin films, and then the charge storage and transportation through PZT thin films were observed by electric force microscopy (EFM). Results were studied and charging mechanisms were proposed.     

Electrostatic force microscopy study on the domain switching properties of the Pb(Zr0.2Ti0.8)O3 thin films with different crystallographic orientations for the probe-based data storage

The domain switching properties of the ferroelectric Pb(Zr(0.2)Ti(0.8))O(3) (PZT) thin films with two types of crystallographic orientations were investigated by electrostatic force microscopy (EFM). The crystallographic orientations of the PZT thin films were random on the (111)Pt/MgO(100) and c-axis preferred on the (100)Pt/MgO(100), respectively. When dc bias was applied to the films for writing in micro-scale area, electrostatic force images showed that the domain switching was hard in the PZT thin films with random orientation, while the pattern could clearly be written in the PZT films with c-axis orientation. The differences in the domain switching properties of each PZT thin film were investigated in the crystallographic orientations point of view, and the domain switching dynamics were also measured by investigating the nano-sized dot switching behavior with respect to the width of the applied voltage pulse.     

Note: Electrical and thermal characterization of a ferroelectric thin film with an electro-thermal nanoprobe

The localized temperature-dependent piezoelectric response of ferroelectric barium strontium titanate (BST) thin films is studied using an electro-thermal (ET) nanoprobe. The ET probe provides independent electrical and thermal excitation to a nanometer-scale volume of the specimen and is capable of detecting the phase transition temperature of the BST thin films. The piezoresponse measured by the ET probe follows the temperature dependence of the piezoelectric constant, whereas with bulk heating the response follows the temperature dependence of the spontaneous polarization. The observed differences stem from the localized inhomogeneous electro-thermal field distribution at the specimen.