退火温度对Bi_4Ti_3O_(12)_Bi_3TiNbO_9复合薄膜铁电性能的影响

研究了退火工艺对溶胶-凝胶法Bi4Ti3O12_Bi3TiNbO9复合薄膜铁电性能的影响。结果表明,采用溶胶-凝胶工艺制备Bi4Ti3O12_Bi3TiNbO9复合薄膜,可将薄膜的剩余极化值Pr提高到19.8μC/cm2(而Bi4Ti3O12薄膜的Pr只有15μC/cm2);薄膜在650℃退火可获得最佳的铁电性能。     

Bi4Ti3O12铁电薄膜的制备及研究进展

铁电薄膜具有良好的铁电、介电性能,在非挥发存储器件方面有很好的应用前景.本文介绍了钛酸铋(Bi4Ti3O12)铁电薄膜的研究现状,对目前Bi4Ti3O12铁电薄膜最常用的几种主要制备方法及其掺杂改性进行了评述,指出了Bi4Ti3O12铁电薄膜研究中亟待解决的几个问题.     

铋层状结构陶瓷Bi_2SrNdNb_2FeO_(12)铁电性能及磁性能研究

用固相烧结法制备了三层铋层状结构陶瓷Bi2SrNdNb2FeO12,对其介电性能及磁性能进行了研究.介电性能研究发现,试样漏导较大,损耗值随温度上升而急剧增加.室温时试样表现出电滞回线特性,但是由于试样漏导较大,高的极化电压加不上去.磁性能测量结果表明,所用试样表现为反铁磁性.试验合成了兼具铁电性能和反铁磁性能的铁电磁体Bi2SrNdNb2FeO12.     

铁电薄膜铁电性能的测量

本文介绍了铁电薄膜材料铁电性能的测量原理和方法.分析了以传统测量电路Sawyer-Tower电路为基础的电滞回线测量方法和基于虚地模式的电滞回线测量方法,并提出了一种基于计算机的铁电性能综合测试仪的实现方案,对其中的主要部分微电流放大器的设计作了介绍.该测试仪不仅能画出铁电薄膜的电滞回线,还可以得到铁电薄膜材料的饱和极化Ps、剩余极化Pr、矫顽场Ec、漏电流Ik等参数,以及对铁电薄膜材料的铁电疲劳性能、铁电保持性能的测试.     

退火温度对LiMn2O4薄膜性能的影响

以壳聚糖、聚乙烯吡咯烷酮(PVP)、醋酸锂和醋酸锰等为原料,采用溶胶凝胶-旋转涂布法在不锈钢基底上制备了LiMn2O4薄膜。通过X射线衍射光谱法(XRD)和扫描电子显微镜法(SEM)研究了退火温度对LiMn2O4薄膜的结构和形貌的影响,并研究了其电化学性能。结果表明:退火温度对薄膜的结构、形貌及电化学性能影响显著。在500～750℃下退火所制得的薄膜表面都呈现褶皱状的微观形貌,650℃以下退火的薄膜样品表面均匀致密,无裂痕。薄膜颗粒粒径随着温度的升高显著增大,结晶化程度也随之提高。650℃退火的薄膜样品为纯相尖晶石结构的LiMn2O4,并且具有最好的电化学性能,在50mA/cm2的电流下,初始比容量为35.9mAh/cm2·mm,经20次循环后比容量为33.8mAh/cm2·mm,容量保持了93.6%,表现出良好的循环性能。     

重掺杂Bi:YIG溅射薄膜的磁和磁光性能

用磁控溅射 快速退火晶化处理在YAG、Al2O3基片上制备了重掺杂Bi:YIG磁光薄膜,利用X射线衍射(XRD)、原子力显微镜(AFM)、磁光克尔仪/光学分度计、振动样品磁强计(VSM)分别研究了薄膜的微结构、磁光性能和磁性能.薄膜的饱和磁化强度为135～139 kA/m,不同基片上制备的薄膜的矫顽力不同,薄膜的法拉第角在450～610nm的光波段范围内约为3～5°/μm;当退火温度在600℃时,在两种基片上制备的薄膜透射率谱非常相似,当退火温度为800℃时,在Al2O3基片上的薄膜透射率谱将出现一个台阶.     

嵌入式电容用钛酸钡/聚酰亚胺复合薄膜的制备及性能研究

对钛酸钡(BT)纳米粒子进行了表面改性,采用原位聚合法将钛酸钡与聚酰亚胺复合制备了高介电BT/PI复合薄膜,为了进一步提高介电性能,将第三组分炭黑掺入其中,并对其进行了红外光谱、扫描电镜(SEM)分析和介电性能测试。结果表明:与未改性的复合薄膜相比,改性后纳米粒子在基体中分散更加均匀,复合薄膜的介电性能明显提高,可用于制备嵌入式电容中的电介质材料。     

Li_4Ti_5O_(12)/TiO_2复合薄膜染料敏化太阳电池的性能

以商品化的P25为原料,利用丝网印刷方法制备TiO2多孔膜,经热处理后,在TiO2多孔膜表面涂覆一层Li4Ti5O12薄膜,经干燥后利用扫描电子显微镜法(SEM)、紫外-漫反射光谱等测试技术对复合薄膜的物理性能进行了表征;并通过组装电池测定了复合薄膜的光电性能。结果表明Li4Ti5O12/TiO2复合薄膜表面颗粒分布均匀,团聚较少;同时,开路电压从0.76 V提高到0.90 V时,效率也有所提高。     

ZIF-67/PVDF复合薄膜的制备及介电性能

改善介电电容器性能是满足电路元器件微型化和集成化需求的有效方法之一，如何提高介电复合材料的介电性能引起了研究者们的广泛关注。本文以聚偏氟乙烯（PVDF）为基体，金属有机框架物（MOFs）ZIF-67为填料，通过流延涂膜制备了一系列ZIF-67/PVDF复合薄膜材料，探究MOFs对PVDF基复合材料的微观结构及宏观性能影响。结果表明：ZIF-67可以诱导PVDF生成更多β相，促进基体极化，提高复合材料的力学性能和介电性能。当填料质量分数为5%时，ZIF-67/PVDF复合薄膜40℃下的杨氏模量为1 200 MPa,击穿场强为139.74 kV/mm，两者相较于纯PVDF薄膜均有增长；100 Hz下的介电常数为10.39，比纯PVDF薄膜提高了35.29%，并且能保持较低的介质损耗。     

铁电薄膜钛酸铋掺杂改善铁电性及疲劳特性的研究

分析了对铁电薄膜Bi4Ti3O12进行A位、B位掺杂时,Bi4Ti3O12铁电性及疲劳特性的改善及相应的理论解释,并指出Bi4Ti3O12值得进一步深入研究的领域。     

Ferroelectric nonvolatile logic

Abstract

This paper describes the design of nonvolatile logic elements using ferroelectric materials. Two separate approaches are discussed. The first approach involves shadowing a CMOS latch or flip-flop with a single bit 2T/2C ferroelectric memory. The second approach offers improved density by integrating ferroelectric capacitors within the logic element. Both designs employ non-switching ferroelectric capacitors to establish the optimum bit line load in the absence of sufficient parasitic capacitance. The paper further describes low-voltage and wide-voltage design techniques used to realize 2.7 – 5.5V products on a “5-volt” ferroelectric process. These same techniques allow 1.8V ferroelectric memory products to be designed using the upcoming generation of production ready “3-volt” ferroelectric materials. Layout effects are discussed, as well as bit/cell ratio optimization.     

Ferroelectric Non-Volatile Logic Devices

Ferroelectric non-volatile logic is proposed. It is low power and can be used for dynamic reconfigurable logic technologies by storing logic state or circuit configuration non-volatility. Cost of LSIs can be decreased by switching circuit blocks. The fundamental device of non-volatile latch was developed and characterized. Moreover, advanced functional device that can do operation at a ferroelectric capacitor was also fabricated. The durability and the low power consumption were confirmed.     

Measurements of Ferroelectric MEMS Microphones

ABSTRACT

This paper introduces three measurement methods of ferro-MEMS microphone in the fields of acoustics, piezoelectronics and mechanics respectively. The results of the three measurements are close to each other in some respects, such as frequency response, resonant frequency, quality value and so on. And they together discover the total characteristics of ferro-MEMS microphone which is hard to be obtained in only one measurement. Especially, a typical TO-CAN packaged ferro-MEMS microphone is presented and coupler measurement technology is discussed for acoustics measurement. Resonance measurement and vibration measurement of microphone membrane are taken mainly to confirm the resonant frequency and frequency response of microphone membrane. All measurement results agree well with theoretical estimation. In the case of ferro-MEMS microphone with membrane size of 2.5 mm × 2.5 mm, the resonant frequency of membrane is 13 kHz, quality factor is about 8. And the sensitivity of the microphone is ?36 dB(15 mV/Pa)@1 kHz.     

Ferroelectric memory programs in Canada

Abstract

Thin film PZT ferroelectrics have been fabricated in Canada since 1976 by magnetron sputtering and more recently by acetate-based sol gel processing and are now being considered for implementation into commercial communications systems. Processing based on rapid thermal annealing has shown marked advantages for crystallization into the required perovskite phase. Applications based on the piezoelectric properties of PZT films are shown to have an interesting potential for a range of devices.     

The Ferroelectric Slab Waveguide: A Geometry for Microwave Components that Incorporate Ferroelectric Materials

A slab geometry, in which ferroelectric is inserted between two “cladding” layers with a microstrip electrode placed on top, is proposed as a way to integrate the properties of ferroelectric materials into microwave components. This structure distributes the propagating microwave fields between the ferroelectric and the cladding, so that the microwave dielectric constant is a weighted average of the dielectric constants of the two materials. It is shown that this geometry drastically reduces dissipation due to dielectric losses in the ferroelectric. In addition, by applying a dc bias to the microstrip line, the dielectric constant of the ferroelectric layer can be varied and with it the microwave properties of the structure.     

Ferroelectric lead iron-chromium-nickel niobate films

Abstract

The fabrication of ferroelectric films of modified lead iron niobate by a multiple magnetron sputtering technique with a subsequent rapid thermal annealing at 800°C for 5 seconds is reported. Since the magnetic properties of pure iron preclude its use in magnetron sputtering, a non-magnetic stainless steel was used as one of the target materials resulting in a ferroelectric of composition Pb[(Fe_0.7Cr_0.2Ni_0.1)_0.5Nb_0.5]O₃. The reaction sequence involved in the formation of the ferroelectric perovskite phase has been identified. The films exhibit unsaturated ferroelectric hysteresis loops with a remanent polarization of 15 μC/cm² and a coercive field of 100 kV/cm. The room temperature dielectric constant and dielectric loss at 1 kHz were 640 and 0.1, respectively. The dielectric constant showed a dielectric anomaly as a function of temperature in the form of a broad maximum around 90°C confirming the ferro-para electric phase transition. The films were highly insulating with a room temperature conductivity of ≈1 X^?12 Ω^?1 cm^?1, and an activation energy of 0.8 eV.     

Fabrication of Ferroelectric Photonic Crystals

ABSTRACT

Ferroelectric photonic crystals consisted of a PLZT matrix and 800 nm-pitch air-holes with a diameter of 560 nm were successfully fabricated by the electron-beam-induced patterning process. Hexagonal holes inscribed to the circles with a diameter of 400 nm in a precursor matrix changed to circular holes with a diameter of 560 nm after heat-treatment due to shrinkage of the matrix. The optical properties of CSD-derived PLZT films were also evaluated. The PLZT films showed the refractive index of 2.3 and the Kerr constant of 0.4 × 10^{? 16} m²/V². Therefore, it is expected that an applied voltage of 9.7 V to 1 μ m-thick PLZT photonic crystals induces 1%-decrease in refractive index and 40°-swinging of light with a wavelength of 1.55 μ m.     

Competing Instabilities in Ferroelectric Aurivillius Compounds

The stability of SrBi₂Ta₂O₉ has been studied by means of ab-initio calculations. The main instability of the tetragonal configuration concerns a non-polar mode at the Brillouin zone border. It can be related through Brillouin zone folding to the well-known soft rigid-unit mode R₂₅ in perovskites. This implies a complex scenario for the whole Aurivillius family with two competing order parameters, which can result in a sequence of two continuous phase transitions or a single discontinuous one. A third hard-mode is shown to play an essential role in the stabilization of the ferroelectric phase.     

Ferroelectric Space Charge Non-Destructive Read-Out memory

Abstract

The Ferroelectric Space Charge (FESC) Memory is a technique to achieve Non-Destructive Read-Out (NDRO) of a ferroelectric memory that employs standard metal-ferroelectric-metal memory capacitors. The NDRO technique allows the polarization state of the capacitor to be read without altering the polarization. This provides the advantage that the memory capacitor is not subjected to the destructive read/rewrite cycle commonly employed in ferroelectric memories, so the lifetime of the device is limited only by the number of times the memory is written. In addition, the NDRO avoids the period of data volatility in the time interval between the read pulse and the subsequent rewrite of the data. The FESC NDRO approach utilizes changes in the dielectric response of the ferroelectric due to interactions between the internal space charges, the spontaneous polarization, and internal and external electrical potentials. The NDRO is implemented entirely in circuitry and does not require specialized ferroelectric devices. It has been proven in working breadboard circuits and hybrid memory modules. The FESC memory concept is the subject of several patents awarded to Draper Lab.     

Diffuse Dielectric Anomaly in Ferroelectric Materials

It has not been clear whether the diffuse dielectric anomaly by Debye-type dielectric relaxation is extrinsic or intrinsic in origin although it has been frequently found in ferroelectric materials regardless of their structures and ferroelectric properties. We experimentally investigated the extrinsic nature of the diffuse dielectric anomaly in ferroelectric oxides and sulfide such as BaTiO₃, Pb_0.9La_0.1TiO₃, and SnP₂S₆. The advanced fitting method using the modified Debye relaxation equation was introduced in order to explain the temperature dependent behavior of the diffuse dielectric anomaly. It was confirmed that the diffuse dielectric anomaly was a competitive phenomenon between the dielectric relaxation and the electrical conduction of the relaxing species. It was also proved that the activation energy of the dielectric relaxation should be always higher than the conductivity activation energy of the relaxing species in the diffuse dielectric anomaly.