铁电薄膜光伏效应研究进展

铁电材料由于具有反常的光伏效应(光生电场高达103~105 V/cm),理论上存在较高的光电转换效率,在太阳能光伏领域具有潜在的应用前景而备受关注。然而,由于铁电材料带隙通常较大、导电性差等因素导致其光生电流较低、光电转换效率还有待进一步提高。弄清铁电光伏效应是增强其转换效率的重要前提。但关于铁电材料光伏效应的起源目前还没有定论,其机制也一直存在争议。基于以上考虑,本文综述了铁电薄膜光伏效应的研究进展,详细阐述了影响光伏效应的各种因素及铁电薄膜光伏效应的机制,并提出了亟待解决的问题。     

铁电薄膜光生伏特效应的研究与应用进展

铁电薄膜材料不仅具备优良的铁电、介电性能,还具有反常光生伏特效应。尽管铁电薄膜理论上有较高的光电转换效率,但目前的效率仍然较低,还不宜用作太阳能转换器。综述了国内外锆酸盐系、铋系以及双钙钛矿等铁电薄膜光生伏效应的最新研究进展,并对其在光学检测设备、铁电光伏器件以及电铸无阻开关方面的最新应用进展进行了归纳总结。铁电薄膜光伏效应的产生机理、影响因素以及应用开拓等方面将是未来研究的重点。     

铁电薄膜的微图形化研究

铁电薄膜在微电子和光电子技术中有着重要的或潜在的应用,可以制作随机存取存储器,热释电阵列探测器,铁民微电子机械系统等,在这些器件的制作过程中,铁电薄膜的微图形化是非常重要的一环,本文简要介绍了几种重要的铁电薄膜微图形化方法及有关研究结果,并比较了这些方法的优缺点。     

铁电陶瓷的技术进展及其应用

铁电陶瓷经过多年研究与开发,已成为引人注目的新型材料。以前主要用于军事和航天行业,随着生产技术的不断进步与成熟,生产成本不断降低,具有特殊性能的铁电陶瓷应用领域不断扩大,现已复盖电子、通信、化工、冶金、医学、计算机和汽车行业,产品包括高介电常数电容器、压电声纳和超声波转换器、广播通信用滤波器、热电转换安全监视装置、医学诊断转换器、立体声高频扬声器、气体点火器、正温度系数（ＰＴＣ）传感器和开关,超声马达、光电光阀、薄膜电容器、铁电薄膜存储器、位移传动器等。 铁电陶瓷产品的开发越来越受到国内外技术界…     

铁电薄膜材料的性能,应用和发展前景

本文阐述了铁电薄膜的铁电、压电、热释电三个重要性质，和它们在微电子学和光电子学的应用，并展望了铁电薄膜未来发展前景。     

铁电薄膜的材料系统与功能性质

集成铁电体把铁电材料与集成半导体技术联合起来,以发展出一批新的电子器件.铁电薄膜在其中发挥着非挥发性记忆、热释电、压电、光折变、抗辐射、声学的和/或介电的功能性质.在不同的器件应用中,铁电薄膜的材料体系是不相同的.在非挥发性存贮器(NVRAM)中,PZT薄膜面临着SrBi2Ta2O9(SBT)系列铁电体的强力挑战;Ba1-xSrxTiO3(BST)则可能出现在下一代高密度动态随机存贮器(DRAM)中.金属氧化物电极和/或过渡层可以克服Pt电极面临的一些问题,并有助于铁电薄膜的外延生长.     

铁电薄膜的制备工艺及发展趋势

随着陶瓷材料新技术生产发展的需求,多功能的铁电薄膜材料日益引起科研人员的广泛关注,并成为近年来研究的热点。论述了铁电薄膜的发展过程、种类、性能以及应用,着重介绍了铁电薄膜的制备方法,并指出了铁电薄膜的发展趋势。     

铁电薄膜材料的研究进展

近年来，随着铁电薄膜制备技术的发展，其应用领域不断扩大。综述了近年铁电薄膜材料研究进展情况，并指出存在的问题及其发展方向。     

铁电陶瓷薄膜的制备与结构表征

本文综述了近年来铁电陶瓷薄膜的化学制备方法,及薄膜材料在结构表征方面的最新研究进展。     

溶胶-凝胶法制备铁电薄膜材料研究进展

铁电薄膜是一类重要的功能材料,是近年来高新技术研究的前沿和热点之一.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(包括水溶液法和醇盐法)、工艺过程(包括前驱体溶液的配制、溶胶的制备、涂覆、凝胶的干燥、热处理)、特点和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,薄膜的质量急待提高,以适应器件的要求.     

Enhanced photovoltaic properties of PbTiO3-based ferroelectric thin films prepared by a sol-gel process

PbTiO₃ (PTO), Pb(Mn_0.1Ti_0.9)O₃ (PMTO), Pb(Sr_0.1Ti_0.9)O₃ (PSTO), and Pb(Zr_0.1Ti_0.9)O₃ (PZTO) were prepared on an indium tin oxide (ITO)/glass substrate by a sol-gel method. PTO, PMTO, PSTO, and PZTO films exhibited energy band gaps of 3.55 eV, 3.63 eV, 3.59 eV, and 3.66 eV, respectively. All these films generated high photocurrents due to high shift currents, because carrier migration channels were successfully introduced by a lattice mismatch between the films and ITO substrates. The PMTO thin film exhibited the best ferroelectric and photovoltaic properties, with a photovoltage of 0.74 V, a photocurrent density of 70 μA/cm², and a fill factor of 43.34%, which confirms that shift current and ferroelectric polarization are two main factors that affect the ferroelectric photovoltaic properties. The PSTO, PZTO, and PTO thin films displayed space-charge-limited current (SCLC) when the electric field strength was below 10 kV/cm, and these three films broke down when the electric field strength was above 10 kV/cm. Analysis of the shift current mechanism confirmed that the breakdown of the PZTO and PSTO thin films resulted from Pool Frenkel emission current. The PMTO thin film displayed SCLC in the test range, which indicates that doping with Mn could inhibit defect formation in ferroelectric thin films.     

Thermodynamical characteristics of thin ferroelectric films

Thermodynamic characteristics of the KDP type ferroelectrics are analysed in the paper. Dispersion laws of the ferroelectric excitations in the thin ferroelectric films are considered. The ordering parameter was investigated at the low temperatures and at the temperatures near the phase transition temperature. The analysis shows that the spontaneous polarization in the film decreases more slowly with increase of the temperature than in the bulk structure. This conclusion is important for practical application because the thin films keep the ferroelectric properties at significantly higher temperatures than the bulk structures.     

The ferroelectric photovoltaic effect of BiCrO3/BiFeO3 bilayer composite films

This work involves an investigation of the structure, ferroelectricity, optical band-gap, photovoltaic spectral response and J-V performance of BiCrO₃/BiFeO₃ bilayer composite films prepared via the solution-gelation technique. It is shown that the enhanced ferroelectric properties are observed for BiCrO₃/BiFeO₃ bilayer composite films by interaction resulting from the coupling between BiFeO₃ and BiCrO₃ layers. The photovoltaic spectral responses of the normalized current for BiCrO₃/BiFeO₃ bilayer composite films presents a noteworthy red-shift towards visible region compared with the pure BiFeO₃ films and the pure BiCrO₃ films. Thus photovoltaic response is attributed to the narrow band-gap of BiCrO₃/BiFeO₃ bilayer composite films. The short circuit current density and open circuit voltage of the BiCrO₃/BiFeO₃ bilayer composite films under white-light illumination are much higher than the values of BiFeO₃ and BiCrO₃ films. The present work provides an available way of controlling photovoltaic response of ferroelectric films and accelerating its application in light sensors, light drivers and ferroelectric photovoltaic cells.     

Ferroelectric-optical memory on ferroelectric thin films

New type memory on ferroelectric thin films is proposed. Writing of information is performed by localheating of the film by laser beam up to the Curie temperature or above and cooling the film in external electric field. Reading can be made by nondestructive methods including pyroelectricity, piezoelectxicity, birefringence, optical activity and photovoltaic effect.     

Phase formation in pulsed laser-deposited ferroelectric thin films

PZT and modified lead titanate thin films were prepared by pulsed excimer laser irradiation of dense ceramic targets. The amorphous phase of the lead titanate was crystallized to pyrochlore and/or perovskite by post annealing and the ratio, perovskite to pyrochlore, was found to depend on the depositional P₀₂. Formation of two types of pyrochlore was discussed. A PZT film formed from a target having the morphotropic phase boundary composition showed no tetragonal X-ray peak splitting. However, Raman spectroscopy suggested that this film had mixed tetragonal and rhombohedral phases, the same as the target.     

Characterization techniques for thin and thick ferroelectric films

A few measurement techniques are presented for characterization of thin and thick ferroelectric films at microwave frequencies. Broadband reflection type measurements using a probe station are considered for on wafer characterization of thin films. The accuracy of the method is analyzed with respect to measurement residual systematic errors. A test structure is introduced allowing quick and accurate extraction of the film parameters based on the rigorous full-wave model. Two measurement techniques are reported for electrode-less characterization of thick ferroelectric films. The first method (X-band) is based on the reflection type measurement of a resonator established by a layered alumina/ferroelectric sample loaded in a cut-off waveguide. The second method (B-band) utilizes an open resonator (OR) technique. Theoretical and experimental results are presented.     

Structural,ferroelectric, and optical properties of Pr-NBT-xCTO relaxor ferroelectric thin films

Sol-gel method was used to prepare the Pr³⁺ ions-doped (1-x)Na_0.5Bi_0.5TiO₃-xCaTiO₃ (Pr-NBT-xCTO) (x?=?0, 0.04, 0.06, 0.08, 0.1, 0.12, and 0.16) thin films on Pt/Ti/SiO₂/Si and fused silicon substrates. The structure phase of thin films was evolving from rhombohedral (R3c) to orthorhombic (Pnma) with increasing CTO content. Owing to the morphotropic phase boundary (MPB), the improved ferroelectric and dielectric properties were obtained at x?=?0.06–0.1. The MPB was formed from the concomitant phase of rhombohedral (R3c) and orthorhombic (Pnma). The Pr-NBT-0.08CTO thin film showed the best ferroelectric and dielectric properties, as well as strong relaxor behavior (the diffusion factor is γ?=?1.79). In addition, all the films exhibited strong red emission as excited by UV light, and wide optical band-gap (3.44–3.47?eV), which might be influenced by grain size and structural variation. Our results indicate that Pr-NBT-xCTO thin films may have potential applications in ferroelectric-luminescence multifunctional optoelectronic devices.     

Additively patterned ferroelectric thin films with vertical sidewalls

The functional properties of electroceramic thin films can be degraded by subtractive patterning techniques used for microelectromechanical (MEMS) applications. This work explores an alternative deposition technique, where lead zirconate titanate (PZT) liquid precursors are printed onto substrates in a desired geometry from stamp wells (rather than stamp protrusions). Printing from wells significantly increased sidewall angles (from ~1 to >35 degrees) relative to printing solutions from stamp protrusions. Arrays of PZT features were printed, characterized, and compared to continuous PZT thin films of similar thickness. Three‐hundred‐nanometer‐thick printed PZT features exhibit a permittivity of 730 and a loss tangent of 0.022. The features showed remanent polarizations of 26 μC/cm², and coercive fields of 95 kV/cm. The piezoelectric response of the features produced an e_31,f of ?5.2 C/m². This technique was also used to print directly atop prepatterned substrates. Optimization of printing parameters yielded patterned films with 90° sidewalls. Lateral feature sizes ranged from hundreds of micrometers down to one micrometer. In addition, several device designs were prepatterned onto silicon on insulator (SOI) wafers (Si/SiO₂/Si with thicknesses of 0.35/1/500 μm). The top patterned silicon was released from the underlying material, and PZT was directly printed and crystallized on the free‐standing structures.     

苯丙乳液最新研究进展

综述了具有高性价比的苯丙乳液研究现状,具体包括乳化剂体系、引发剂体系、聚合工艺、胶粒设计、新型乳液聚合技术等方面,为制备性能优异、用途广泛的苯丙乳液指明了方向。