Si基Bi3.25La0.75Ti3O12铁电薄膜的制备与特性研究

采用Sol-Gel工艺低温制备了Si基Bi3.25La0.75Ti3O12铁电薄膜.研究了退火温度对薄膜微观结构、介电特性与铁电性能的影响.500℃退火处理的Bi3.25La0.75Ti3O12薄膜未能充分晶化,晶粒细小且有非晶团聚,介电与铁电性能均较差.高于550℃退火处理的Bi3.25La0.75Ti3O12薄膜表面平整无裂纹,晶粒均匀,无焦碌石相或其他杂相,薄膜为多晶生长,具有较好的介电与铁电性能,4V电压下的漏电流密度低于2×10-8A/cm2.随退火温度升高,晶化程度的提升和晶粒尺寸的增大使薄膜的剩余极化增大而矫顽电场降低.600℃退火处理的Bi3.25La0.75Ti3O12薄膜显示了优于Bi4Ti3O12薄膜的铁电性能,其剩余极化Pr和矫顽电场Ec分别达到17.5μC/cm2和102kV/cm.     

(111)取向(Pb,La)TiO3铁电薄膜中90°纳米带状畴与热释电性能的研究

采用射频磁控溅射技术在Pt/Ti/SiO₂/Si(100)衬底上生长了掺镧钛酸铅(PLT)铁电薄膜.用X射线衍射技术(XRD)研究了PLT薄膜结晶性能，结果表明PLT薄膜为 (111)择优取向钙钛矿相织构.使用原子力显微镜(AFM)和压电响应力显微镜(PFM) 分别观察了PLT薄膜的表面形貌和对应区域的电畴结构.PFM观察显示PLT薄膜中存在90°纳米带状畴，电畴的极化为首尾相接的低能量的排列方式，带状畴的宽度为20—60nm.研究了PLT10铁电薄膜的制备条件与性能之间的关系.发现在优化条件下制备的PLT10铁电薄膜的介电常数ε_r为365、介电损耗tgδ为0.02，热释电系数γ为2.18×10^-8C·(cm²·K)^-1，可以满足制备非制冷红外探测器的需要. 关键词： PLT薄膜 电畴 PFM 极化     

Sol-gel法制备Bi0.85Nd0.15FeO3多铁性薄膜

利用sol-gel法在Pt/Ti/SiO₂/Si衬底上制备出Bi_0.85Nd_0.15FeO₃薄膜.研究退火温度对其晶相形成的影响,发现在450 ℃退火时,Bi_0.85Nd_0.15FeO₃晶相开始形成,但是结晶较差,而且存在杂相;在500—600 ℃退火可以获得单相Bi_0.85Nd_0.15FeO₃薄膜,退火温度升高有利于其结晶.对600 ℃退火的Bi_0.85Nd_0.15FeO₃薄膜的介电、铁电和电磁性能进行了测试.在测试频率为1 MHz时,其介电常数和介电损耗分别为145,0.032;饱和磁化强度大约为44.8 emu/cm³;剩余极化值(2P_r)大约是16.6 μC/cm². 关键词： sol-gel法 0.85Nd_0.15FeO₃薄膜')" href="#">Bi_0.85Nd_0.15FeO₃薄膜 铁电性能 铁磁性能     

SrBi2Ta2O9铁电薄膜微结构及其抗疲劳等铁电特性的研究

在低温Pt/Ti/SiO₂/Si衬底上用脉冲准分子激光沉积技术结合氧气氛下700℃退火获得高质量的SBT薄膜，其择优取向为（008）和（115）．薄膜厚度约为200nm．铁电性能测试显示较饱和的、方形的电滞回线，其剩余极化和矫顽电场分别为10μC/cm²和57kV/cm，在10¹⁰次开关极化后没有显示任何疲劳，在5V直流电压下的漏电流密度约为4×10^-8A/cm²，直流击穿电场约为250kV/cm 关键词：     

Si基Bi3.25La0.75Ti3O12铁电薄膜的制备与特性研究

采用Sol-Gel工艺低温制备了Si基Bi_3.25La_0.75Ti₃O₁₂铁电薄膜.研究了退火温度对薄膜微观结构、介电特性与铁电性能的影响.500℃退火处理的Bi_3.25La_0.75Ti₃O₁₂薄膜未能充分晶化，晶粒细小且有非晶团聚，介电与铁电性能均较差.高于550℃退火处理的Bi_3.25La_{0.75 关键词： 铁电薄膜 3.25}La_0.75Ti₃O₁₂')" href="#">Bi_3.25La_0.75Ti₃O₁₂ Sol-Gel工艺     

PT/PZT/PT铁电薄膜的铁电畴和畴壁

用sol-gel法制备出了具有良好铁电性、纯钙钛矿结构的PbTiO₃/Pb(Zr_0.3Ti_0.7)O₃/PbTiO₃(PT/PZT/PT)新型夹心结构铁电薄膜.用扫描力显微镜(SFM)的压电响应模式获得了薄膜铁电畴的垂直于膜平面方向(OPP)、膜平面内(IPP)及OPP的相位和幅度图像，结合理论分析指出薄膜的电畴主要由c畴和偏离垂直于膜平面方向上的c畴构成，薄膜取向的复杂性导致了复杂的畴结构.对于［111］取向的薄膜，当偏离垂直于膜平面方向上的c畴在垂直膜平面方向和面内方向都相反时构成180°的畴壁，在垂直膜平面方向上相同、面内方向相反或由垂直膜平面方向上相反、面内方向相同时构成90°畴壁. 关键词： 铁电薄膜 PT/PZT/PT 电畴和畴壁 扫描力显微镜(SFM)     

外加电场对铁电薄膜相变的影响

采用热力学非线性理论,研究了外加电场对立方基底Pb(Zr_0.3Ti_0.7)O₃(PZT)铁电薄膜相变的影响.通过数值计算,得到了"失配应变-外加电场"相图,及外加电场与极化强度的关系.当外加电场达到186 kV/cm时,能使生长在SrTiO₃ 基底上PZT铁电薄膜从单斜r相转变为c相.在实验上,采用扫描探针显微镜通过对PZT薄膜施加不同的极化电场来研究了它的电畴翻转.从得到的压电响应相图可以看出,绝大多数的电畴是清晰可 关键词： 铁电薄膜 相变 扫描探针显微镜 失配应变     

含铜铁电电容器SrRuO3/Pb(Zr0.4Ti0.6)O3/SrRuO3/Ni-Al/Cu/Ni-Al/SiO2/Si异质结的研究

应用磁控溅射法以Ni-Al同时作为Cu与SiO₂/Si,Cu与SRO薄膜之间的阻挡层材料,将Cu与SiO₂/Si衬底和氧化物薄膜电极隔离,避免它们在高温氧气氛中发生化学反应和互扩散,实现了Cu薄膜与氧化物铁电电容器的集成.采用X射线衍射仪(XRD)和原子力显微镜(AFM)研究了不同温度下快速退火的SrRuO₃(SRO)/Ni-Al/Cu/Ni-Al/SiO₂/Si含Cu异质结的微结构和表面形貌,结果发现SRO/Ni-Al/Cu/Ni-Al/SiO₂/Si含Cu多层异质结薄膜在高达750 ℃仍然具有较强的Cu衍射峰和比较平整的表面,显示出了很好的高温热稳定性.研究了"室温长高温退"和"低温长高温退"两种工艺手段,发现在制备含Cu多层氧化物薄膜异质结时,低温长高温后退火的方式要优于常规的室温长高温后退火方式,通过低温长高温退工艺可以缓解应力、削弱界面粗化和避免高温生长对阻挡层和Cu薄膜结构的破坏.最后结合sol-gel法将Pb(Zr_0.4Ti_0.6)O₃(PZT)生长在该含Cu异质结上,制备得SRO/PZT/SRO/Ni-Al/Cu/Ni-Al/SiO₂/Si含Cu铁电电容器,研究了电容器的薄膜结构、铁电性能和漏电特性等,发现制备的含Cu铁电电容器具有很好的铁电性能,如电滞回线趋势饱和,剩余极化强度高达~42 μC/cm²,矫顽电压为~1.0 V,介电常数~1600,漏电流~1.83×10^-4 A/cm²,以及良好的抗疲劳特性和保持特性等,表明导电性优良的Cu薄膜可以应用于高密度高性能铁电电容器.对其漏电机理研究表明,SRO/PZT/SRO含Cu铁电电容器满足空间电荷限制传导机理. 关键词： Cu PZT 铁电电容器 Ni-Al     

Pb(Zr0.3Ti0.7)O3铁电薄膜激光感生电压效应

采用脉冲激光沉积(PLD)技术在LaSrAlTaO₃(LSATO),LaAlO₃(LAO)和SrTiO₃(STO)的单晶倾斜衬底上成功制备了Pb(Zr_0.3Ti_0.7)O₃(PZT)薄膜,在三种倾斜衬底上生长的PZT薄膜中都首次发现了LIV效应.对PZT/LSATO薄膜在a,c轴两种不同取向择优生长下的LIV效应做了研究,发现在薄膜c轴取向择优生长 关键词： 激光感生电压效应 铁电薄膜 薄膜生长取向 原子层热电堆     

PZT铁电薄膜纳米尺度畴结构的扫描力显微术研究

利用扫描力显微术中压电响应模式原位研究了（111）择优取向的PZT60/40铁电薄膜的纳米尺度畴结构及其极化反转行为.铁电畴图像复杂的畴衬度与晶粒中的畴排列和晶粒的取向密切相关.直接观察到极化反转期间所形成的小至30nm宽的台阶结构，该台阶结构揭示了（111）取向的PZT60/40铁电薄膜在极化反转期间其畴成核与生长机理主要表现为铁电畴的纵向生长机理. 关键词： 畴结构 反转机理 PZT薄膜 扫描力显微术     

聚(偏氟乙烯-三氟乙烯)纳米薄膜极化反转与疲劳特性

采用旋涂法制备了厚度为140 nm的聚(偏氟乙烯-三氟乙烯)[P(VDF-TrFE)]纳米薄膜, 研究了不同退火温度以及环境相对湿度对薄膜的极化反转和疲劳性能的影响. 运用X射线衍射仪、扫描电子显微镜和傅里叶变换红外光谱仪等测试技术对薄膜的微结构进行了表征. 实验结果表明, 通过不同温度的退火处理, P(VDF-TrFE)铁电薄膜的结晶度随着退火温度的升高而不断提高, 并且一定的温度范围内的退火处理可以提高薄膜的极化性能; 此外, P(VDF-TrFE) 铁电薄膜性能还表现出一定的环境湿度的敏感特性, 这与薄膜的物理性能和结构特点密切相关; P(VDF-TrFE)铁电薄膜在不同的环境湿度条件下 表现出较好的电学特性, 其漏电流均保持在10 ^-7A/cm² 的较低水平. 本工作揭示了再退火过程对薄膜的极化反转速度和疲劳恢复特性的影响, 并结合薄膜二次疲劳结果, 探讨了薄膜可逆的内部疲劳恢复特性机理.     

Nanoscale imaging of ferroelectric domain and resistance switching in hybrid improper ferroelectric Ca3Ti2O7 thin films

Hybrid improper ferroelectrics have their electric polarization generated by two or more combined non-ferroelectric structural distortions such as the rotation and tilting of Ti-O octahedral in Ca₃Ti₂O₇ (CTO) family. In this work, we prepared different thickness CTO thin films on Pt substrates by pulsed laser deposition, and investigated their ferroelectric polarization reversal and the current transport properties by using the piezoresponse force microscopy and conducting atomic force microscopy, respectively. It is found that the CTO films exhibit clear ferroelectric domain switching and ferroelectric resistance switching behaviors, and the maximum resistive ratios of CTO film reaches ∼1750. These results demonstrate that hybrid improper ferroelectrics CTO films are promising materials for being employed in non-volatile memory and logic devices.     

Effects of oxygen partial pressure on the ferroelectric properties of pulsed laser deposited Ba0.8Sr0.2TiO3 thin films

The Ba_0.8Sr_0.2TiO₃ thin films were grown on the Pt–Si substrate at 700 °C by using a pulsed laser deposition technique at different oxygen partial pressure (PO₂) in the range of 1–20 Pa and their properties were investigated. It is observed that the PO₂ during the deposition plays an important role on the tetragonal distortion ratio, surface morphology, dielectric permittivity, ferroelectric polarization, switching response, and leakage currents of the films. With an increase in PO₂, the in-plane strain for the BST films changes from tensile to compressive. The films grown at 7.5 Pa show the optimum dielectric and ferroelectric properties and also exhibit the good polarization stability. It is assumed that a reasonable compressive strain, increasing the ionic displacement, and thus promotes the in-plane polarization in the field direction, could improve the dielectric permittivity. The butterfly features of the capacitance–voltage (C–V) characteristics and the bell shape curve in polarization current were attributed to the domain reversal process. The effect of pulse amplitude on the polarization reversal behavior of the BST films grown at PO₂ of 7.5 Pa was studied. The peak value of the polarization current shows exponential dependence on the electric field.     

Ferroelectric and dielectric properties of SrBi<Subscript>4</Subscript>Ti<Subscript>4</Subscript>O<Subscript>15</Subscript> thin films grown on Bi<Subscript>4</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript> film layer

Ferroelectric and dielectric properties of bilayered ferroelectric thin films, SrBi₄Ti₄O₁₅ grown on Bi₄Ti₃O₁₂, were investigated. The thin films were annealed at 700°C under oxygen atmosphere. The bilayered thin films were prepared on a Pt(111)/Ti/SiO₂/Si substrate by a chemical solution deposition method. The dielectric constant and dielectric loss of the bilayered thin films were 645 and 0.09, respectively, at 100 kHz. The value of remnant polarization (2P _r) measured from the ferroelectric thin film capacitors was 60.5 μC/cm² at electric field of 200 kV/cm. The remnant polarization was reduced by 22% of the initial value after 10¹⁰ switching cycles. The results showed that the ferroelectric and dielectric properties of the SrBi₄Ti₄O₁₅ on Bi₄Ti₃O₁₂ ferroelectric thin films were better than those of the SrBi₄Ti₄O₁₅ grown on a Pt-coated Si substrate suggesting that the improved properties may be due to the different nucleation and growth kinetics of SrBi₄Ti₄O₁₅ on the c-axis-oriented Bi₄Ti₃O₁₂ layer or on the Pt-coated Si substrate.     

Low-voltage pulse exciting electron emission from ferroelectric copolymer film cathode: Role of film thickness and emission stability

Ferroelectric copolymer thin films P(VDF-TrFE) are used as a ferroelectric cathode for investigation of their electron emission properties. This ferroelectric copolymer films with different thicknesses are deposited by spin-coating method, and then the annealing process is carried out to improve the crystallinities of as-deposited copolymer films. The measurement results of ferroelectric electron emission showed that the copolymer P(VDF-TrFE) films had a desired ferroelectric electron emission ability excited at low-voltage pulse, and its peak emission current can reach to be ∼1.3 μA when the pulse voltage is 280 V. In addition, the effect of film thickness on electron emission property and emission stability of copolymer thin film P(VDF-TrFE) are discussed.     

铁电双层膜的反转动力学行为

基于Landau-Khalatnikov运动方程,本文研究了含有表面过渡层和铁电界面耦合的反转动力学行为(包括平均极化、反转时间、反转电流和矫顽场).研究结果表明:在铁电双层膜系统中存在一个竞争的机理,即表面过渡层与界面耦合的竞争作用.我们发现在双层膜反转过程中出现了反常行为,这些反常行为归因于表面过渡层与界面耦合之间的竞争.表面过渡层与界面耦合的共同行为对铁电双层膜的动力学特性起到了决定性的作用.     

烘烤温度对溶胶-凝胶法制备镧掺杂钛酸铋薄膜结构与铁电性质的影响

采用溶胶-凝胶法，在保持薄膜结晶温度和有机物分解温度相同情况下，发现烘烤温度（即溶剂的挥发温度）对镧掺杂钛酸铋薄膜的晶体结构、表面形貌和铁电性质均产生重要影响.在较低烘烤温度下得到的薄膜（117）择优取向明显.但随着烘烤温度增加，薄膜的（117）择优取向逐渐减弱.薄膜的表面晶粒形貌则从棒状逐渐转变为盘状.还测量了薄膜的铁电性质，发现在250℃烘烤温度下得到的薄膜具有最大的剩余极化强度，2Pr为28.4μC/cm2.对实验现象进行了定性解释. 关键词： 溶胶-凝胶法 烘烤温度 铁电薄膜