溶胶-凝胶法制备MgO/(Ba0.8Sr0.2)TiO3多层薄膜及其介电和漏电特性研究

采用改进的溶胶-凝胶方法在LaNiO3/Si(100)衬底上制备了MgO/(Ba0.8Sr0.2)TiO3多层薄膜.实验结果表明,MgO层的引入改变了(Ba0.8Sr0.2)TiO3的介电特性和漏电流行为,使薄膜的漏电流降低了3个数量级,但介电常数也有相应降低.漏电流的显著降低是由MgO子层的高阻特性以及微量Mg向(Ba0.8Sr0.2)TiO3晶格中扩散造成的.     

掺杂BaTiO3/SrTiO3多层膜与太赫兹波相互作用

掺杂半导体中的载流子吸收在THz波段非常明显,其相互作用研究是研制THz通信中的关键器件之一的基础。采用氟化氪（KrF）脉冲准分子激光烧蚀沉积（PLD）技术,制备了Ni掺杂BaTiO3/SrTiO3多层膜。基于辐射频率为3.09 THz、脉冲功率为10 mW量级的THz 量子级联激光器(QCL)光源研究了太赫兹波在Ni掺杂BaTiO3/SrTiO3多层膜中的传输,发现损耗主要是Ni颗粒的非共振吸收导致。     

溶胶-凝胶法制备(Ba0.7Sr0.3)TiO3/LaNiO3异质薄膜及其结构和介电性质研究

采用改进的溶胶-凝胶方法在单晶Si(100)衬底上制备了介电性能优异的(Ba0.7Sr0.3)TiO3/LaNiO3 异质薄膜.实验发现,在750 ℃下、O2气氛中晶化的LaNiO3薄膜的电阻率最小.C-V与I-V特性测量表明(Ba0.7Sr0.3)TiO3薄膜具有优异的介电性能,在频率为50 kHz、零偏压下的相对介电常数εr>300,偏压为6 V时漏电流密度JL<1.2×10-6 A/cm2.     

溶胶-凝胶法制备的高压电常数（Bi0.5Na0.5）1－xBaxTiO3系无铅压电陶瓷

测量了使用溶胶-凝胶工艺制备的(Bi0.5Na0.5)1-xBaxTiO3(x=0.00，0.04，0.06，0.08,0.12)系陶瓷的介电、压电、铁电和热释电性能.由于使用了溶胶-凝胶工艺制备的粉料，因此所有样品的压电性能都得到了较大提高.其中(Bi0.5Na0.5)0.94Ba0.06TiO.3系陶瓷具有该系列最大的压电常数，d33=173×10-12C/N，与传统工艺相比，d33提高了近40%.同时，在一定范围内，随Ba含量的增加，材料的剩余极化Pr和矫顽场Ec逐渐减小，退极化温度逐渐降低.对于(Bi0.5Na0.5)0.94Ba0.06TiO.3系陶瓷，剩余极化和矫顽场分别为25μC/cm2和28kV/cm，退极化温度约为80℃. 关键词： 溶胶-凝胶 压电常数 剩余极化 矫顽场     

电子型高温超导体/铁电体/巨磁阻材料异质结的生长及其电输运性质的研究

本文中采用脉冲激光沉积的方法原位制备了结构完整的La1.89Ce0.11CuO4(LCCO)/Ba0.7Sr0.3TiO3(BST)/La0.67Sr0.33MnO3(LSMO)三层膜,并在此基础上制得了类似P-I-N型的全钙钛矿结构材料异质结.在不同的温度区间对其电输运性质进行了测量.测量结果表明随着充当绝缘层的Ba0.7Sr0.3TiO3的厚度的变化,异质结的电输运机制也在变化.当其厚度到达25纳米时,整个结在低温区呈现良好的整流特性.     

Ba0.95Eu0.05TiO3陶瓷的变温拉曼研究

采用高温固相反应方法制备了高质量的Ba0.95Eu0.05TiO3多晶陶瓷, X-射线衍射谱(XRD)表明所制备的材料为单相, SEM的图象显示材料致密。用波长为514.5 nm激光光源激发, 在温度83 K-553 K区间内对Ba0.95Eu0.05TiO3陶瓷进行了系统的拉曼实验研究, 实验证明散射强度是温度的函数, 在相变点附近散射强度发生突变, 同时Eu3+对Ba2+的替代导致了BaTiO3相变温度向低温方向位移。我们并对其物理机理进行了探讨。     

Tb1-xDyxFe2-y-Fe掺杂BaTiO3多层膜中的磁电耦合

用溶胶-凝胶法制备了Fe掺杂BaTiO3粉体,在1350℃下烧结成圆片状多晶样品,并与Tb1-xDyxFe2-y胶合成磁电(ME)双层膜或三层膜.实验分析表明Fe:BaTiO3依然是四方相钙钛矿结构,但是居里温度及相变潜热均略低于纯净BaTiO3.研究了Tb1-xDyxFe2-y-Fe∶BaTiO3双层膜和Tb1-xDyxFe2-y-Fe∶BaTiO3-Tb1-xDyxFe2-y三层膜的ME效应.在2.8×104 A/m的磁场下,两者的横向ME电压系数均达其峰值,分别为6.225和26.25 mV·(A·m-1)-1·cm-1.并且,用掺杂BaTiO3制备的双层膜和三层膜的横向ME电压系数均为相同条件下用纯净BaTiO3制备的双层膜和三层膜的横向ME电压系数的1.5倍.另外由于不含铅,锆等有害物质,符合环保要求,因此采用掺杂BaTiO3制备的磁电效应器件具有深入研究和应用价值.     

单相Bi0.9Ba0.1Fe0.85Mn0.15O3陶瓷中的多铁性

溶胶-凝胶法制备了Bi_0.9Ba_0.1Fe_0.85Mn_0.15O₃陶瓷样品,XRD分析显示其为单相菱方钙钛矿结构,明显的磁滞回线和电滞回线说明其在室温具有弱铁磁性和铁电性,介电常数随外磁场的变化显示双掺样品具有更大的磁容效应. 关键词： 溶胶-凝胶法 多铁材料 磁容效应     

高氧压下氧化物薄膜同质和异质外延的RHEED实时监测

我们自行研制了具有三级差分气路可以在高气压下工作的RHEED系统(High-pressure RHEED),并利用本系统实时监测了(001)SrTiO3基片上SrTiO3:Nb、Ba0.5Sr0.5TiO3、YBa2Cu3O7单层薄膜,及Ba0.5Sr0.5TiO3/SrTiO3:Nb双层膜的生长过程.研究结果表明当镀膜室氧压高达21Pa时该系统仍然可以正常工作,并且能够获取较清晰的衍射图样.通过分析衍射图样我们发现,所有这些薄膜都是外延生长且晶体质量良好,但薄膜生长模式及表面平整度受沉积条件影响较大.在真空下薄膜基本上以层状模式生长,具备纳米级光滑的表面,且其表面平整度并不因膜厚的改变而变化;而在10Pa量级氧压下薄膜更倾向于以岛状模式生长,膜表面平整度较差,并且随膜厚的增加粗糙度上升.此外对多层薄膜而言,底层薄膜的表面和结构直接影响到顶层薄膜的质量和品质.     

溶胶-凝胶法制备(Ba0.7Sr0.3)TiO3/LaNiO3异质薄膜及其结构和介电性质研究

采用改进的溶胶-凝胶方法在单晶Si(100)衬底上制备了介电性能优异的(Ba_0.7Sr_0.3)TiO₃/LaNiO₃异质薄膜.实验发现，在750 ℃下 、O₂气氛中晶化的LaNiO₃薄膜的电阻率最小.C-V与I-V特性测量表明(Ba_0.7Sr_0.3)TiO₃薄膜具有优异的介电性能，在频率为50kHz、零偏压下的相对介电常数ε_r>300，偏压为6V时漏电流密度J_L<1.2×10^-6A/cm². 关键词： xSr_1-x)TiO_３铁电薄膜')" href="#">(Ba_xSr_1-x)TiO_３铁电薄膜 ３底电极')" href="#">LaNiO３底电极 溶胶-凝胶法     

嵌埋Ni颗粒的BaTiO_3/SrTiO_3薄膜的相变特性

采用高温X射线原位衍射和变温介电谱对SrTiO3基底上外延生长的BaTiO3(嵌埋Ni颗粒)薄膜进行了相变特性分析。从X射线衍射和介电谱的分析结果得出,BaTiO3的相变温度点转变为弥散的温度区间。在这个弥散的相变温度区间内,由于基底和薄膜之间的失配,以及嵌埋Ni颗粒的应力作用,薄膜的介电响应弥散剧烈,并偏离德拜弛豫。分析Cole-Cole图获知,BaTiO3薄膜在四方相转变为立方相的相变过程中同时存在几种极化机制,在高温状态下介电损耗随温度增大而增大。降温过程中,薄膜没有立即恢复四方相,可能是基底和Ni颗粒的共同作用影响了相变弛豫。     

淀积气压对脉冲激光淀积La掺杂钛酸铅薄膜介电性能的影响

利用脉冲激光淀积法在Pt/Ti/SiO2/Si衬底上制备了28mol%La掺杂钛酸铅薄膜.采用不同的淀积氧气压，并分析了其对薄膜微观结构和介电性能的影响.结果表明，在2Pa左右的气压下淀积的薄膜具有好的结晶度和介电系数.在频率为10kHz时28mol%La掺杂钛酸铅薄膜的介电系数达852，并且保持了较低的损耗.同时制备了其他La掺杂浓度的PbTiO3薄膜，发现它们也有类似的特点.对此作了定性解释. 关键词： 脉冲激光淀积 PLT薄膜 气压 介电增强     

Electric-field-induced soft-mode hardening in SrTiO3 films

We have studied electric-field-induced Raman scattering in SrTiO3 thin films using an indium-tin-oxide/SrTiO3/SrRuO3 structure grown by pulsed laser deposition. The soft mode polarized along the field becomes Raman active. Experimental data for electric-field-induced hardening of the soft modes and the tuning of the static dielectric constant are in agreement described by the Lyddane-Sachs-Teller formalism. The markedly different behavior of the soft modes in thin films from that in the bulk is explained by the existence of local polar regions.     

Electrical characteristics of BaTiO3/ Bi0.5K0.5TiO3 multilayered thin films synthesized via metalloorganic decomposition

Multilayered BaTiO₃(BTO)/Bi_0.5K_0.5TiO₃ (BKT) thin films have been fabricated on Pt/Ti/SiO₂/Si substrates using a metalloorganic decomposition process. XRD investigation of the resultant BTO/BKT multilayered thin films shows that they retain a perovskite-related structure type. They also exhibit a well-defined, polarization–electric field hysteresis loop with a measured remnant polarization (2P_r) of 5 µC/cm² at an applied electric field of 250 kV/cm. The measured dielectric constant and dielectric loss at 10 kHz is 470 and 0.07 respectively. These multilayer BTO/BKT films maintain an excellent fatigue-free character even after 10⁹ switching cycles. The mechanism associated with the enhancement of the electrical properties of the synthesized BTO/BKT films is also discussed.     

The influence of Co doping on the dielectric, ferroelectric and ferromagnetic properties of Ba0.70Sr0.30TiO3 thin films

Ba_0.70Sr_0.30TiO₃ (BST) thin films doped by Co (BSTC) are fabricated by sol-gel method on a Pt/Ti/SiO₂/Si substrate. A strong correlation is observed among the microstructure, dielectric, ferroelectric, ferromagnetic properties and Co concentration. The dielectric constant of BST thin films can be tailored from 343 to 119 by manipulating the Co concentration. The dielectric loss of BSTC thin films are still kept below 0.020 and the tunability is above 30% at a dc-applied electric field of 500 kV/cm. With increasing Co doping up to 10 mol%, the coexistence of ferromagnetism and ferroelectrics is found. Suitable dielectric constant, low-dielectric loss, and high tunability of this kind of thin films can be useful for potential tunable applications.     

异质界面对Ca(Mg1/3Nb2/3)O3/CaTiO3叠层薄膜结构和介电性能的影响

采用异质叠层方式制备出一定厚度的Ca(Mg_1/3Nb_2/3)O₃/CaTiO₃(CMN/CT)叠层薄膜,研究了异质界面对薄膜结构、微观形貌及介电性能的影响及其规律.根据实验测试结果,提出CMN/CT叠层薄膜的模拟等效电路,建立介电常数和介电损耗的理论计算公式.结果表明:CMN/CT异质叠层薄膜具有完全正交钙钛矿结构,结构致密,厚度均匀,薄膜中存在独立的CMN和CT相.异质界面处存在过渡层,随着薄膜中异质界面个数增加,介电常数增大,介电损耗减小.减小界面过渡层的厚度,有利于提高CMN/CT叠层薄膜的介电性能.     

SrTiO3金属-绝缘体-半导体结构的介电与界面特性

采用金属有机分解法在p型Si衬底上制备了SrTiO3（STO）薄膜.研究了STO薄膜金属 绝缘体 半导体(MIS)结构的介电和界面特性.结果表明，STO薄膜显示出优异的介电性能，在10kHz处的介电常数约为105，损耗低于001，这来源于多晶结构和良好的结晶性；MIS结构中的固定电荷密度Nf和界面态密度Dit分别约为15×1012cm-2和(14—35)×1012cm-2eV-1，这主要与Si/STO界面处形成的低介电常数界面层有关. 关键词： SrTiO3薄膜 MIS结构 介电性能 Si/STO界面     

Room-temperature pulsed laser deposition and dielectric properties of amorphous Bi3.95Er0.05Ti3O12 thin films on conductive substrates

Bi_3.95Er_0.05Ti₃O₁₂ (BErT) thin films were prepared on Pt/Ti/SiO₂/Si and indium-tin-oxide (ITO)-coated glass substrates at room temperature by pulsed laser deposition. These thin films were amorphous with uniform thickness. Excellent dielectric characteristics have been confirmed. The amorphous BErT thin films deposited on the Pt/Ti/SiO₂/Si and ITO-coated glass substrates exhibited almost the same dielectric constant of 52 with a low dielectric loss of less than 0.02 at 1 kHz. Meanwhile, the dielectric properties of the thin films had an excellent bias voltage stability and thermal stability. The amorphous BErT thin films might have potential applications in microelectronic and optoelectronic devices.     

Synthesis and characteristics of KTa0.5Nb0.5O3 thin films

KTa_0.5Nb_0.5O₃ thin films were synthesized via a metal-organic solution. Characteristics were measured, such as X-ray diffraction pattern, surface morphology and roughness, and electric properties. The synthesized films have a (100) preferential growth orientation on Si (100) substrate. The homogeneous microstructure and smooth surface benefit to the good electric properties of the thin films. The current density-voltage characteristic shows an unexpected feature of the transition from linear to nonlinear, which can be explained by the space-charge-limited mode. Dielectric constant and loss of the thin films decrease with the increase of frequency. The decrease of dielectric loss is related to the decrease of net polarization in material. The decrease of dielectric constant can be explained by Debye formula. The phase transition temperature T _c is about 102 °C for KTa_0.5Nb_0.5O₃ materials.     

The effects of substrate temperatures on the electrical properties of CaZrO3 thin films prepared by RF magnetron sputtering

The radio frequency magnetron sputtering technology (RFMS) was employed to deposit perovskite structure orthogonal phase CaZrO₃ thin films on Pt/Ti/SiO₂/Si substrates. The effects of substrate temperatures on structure and electrical properties of these films were investigated in detail. The CaZrO₃ thin films were systematically characterized by means of X-ray diffraction (XRD), Scanning electron microscope (SEM), Multi-frequency LCR meter (HP4294A) and Radiant Precision Workstation to study the phase structure, cross-section morphology, dielectric and ferroelectric properties at different substrate temperatures. The result indicates that these films can withstand 80 V DC Bias voltage and have excellent stability of frequency, voltage and temperature. The CaZrO₃ thin film prepared at 550 °C turned out to be mainly orthorhombic CaZrO₃ phase with high permittivity, low dielectric loss, extremely low leakage current (at 1 MHz, the dielectric constant is 39.42, the dielectric loss is 0.00455, the quality factor is 220 and the leakage current density is 9.11 × 10⁻⁷A/cm² at 80 V applied voltage.). This work demonstrates that higher substrate temperature can boost the formation of orthorhombic CaZrO₃ phase and the CaZrO₃ thin film prepared by RF magnetron sputtering is a very promising paraelectric material in the application of thin film capacitor.