Polarization inscription in ferroelectric (111) PZT and (100) SBT films

Ferroelectric thin films form an equilibrium domain structure compatible with their respective crystallographic symmetry. In tetragonal (111) PZT, 90° domains prevail; in (pseudo-tetragonal) (100) SBT both 90° and 180° domains are present. The size of 90° domains has been measured for e.g., PZT as slabs of 15 nm width. Domain size is a result of stress minimization in the film during the paraelectric (PE) → ferroelectric (FE) transition. A precise and regular domain pattern for (111) PZT and (100) SBT films has been investigated in detail by TMSFM. Single domains can be addressed mechanically with the tip of an AFM. Such single domain switching corresponds to a data storage density of 200 Gbit/inch². Applications of ferroelectric and high- paraelectric materials for e.g., non-volatile data storage replacing DRAM devices or as sensors in infrared cameras are increasingly becoming popular.     

Visualization of Ferroelectric Domains in Thin Films of Molecular Materials Using Confocal Micro-Raman Spectroscopy

Ferroelectrics are an important class of functional materials. Among all their unique properties, the study of their ferroelectric domains and domain walls is of great interest due to their importance in ferroelectric applications. There are many methods to characterize ferroelectric domains, namely, scanning probe microscopy, optical microscopy, electron microscopy, etc. Currently, newly emerged molecular ferroelectrics are attracting much attention from chemists, physicists and researchers in material sciences due to their structural flexibility, light mass, simple fabrication, etc. However, for the characterization of molecular ferroelectric domains, most conventional methods require either a complicated preparation process or direct contact between physical probes and material surfaces, limiting the development of molecular ferroelectric materials. In this report, we have demonstrated that confocal micro-Raman spectroscopy, as a nondestructive and noncontact in-situ method, is very suitable for studying the ferroelectric polarization and structures of domains in molecular ferroelectrics. Taking recently reported molecular ferroelectric trimethylchloromethyl ammonium trichlorocadmium(II) (TMCM-CdCl₃) as an example, the non-180° domains have been characterized and visualized at different temperatures. Such a simple and extendable method requires minimum sample preparation, which would further benefit the research of molecular ferroelectric domain engineering and promote the miniaturization and integration of molecular ferroelectric films.     

Absorption-Reflection Infrared Spectroscopy Studies of Sol-Gel Prepared Ferroelectric Pb(Zr,Ti)O3 Thin Films on Pt Electrodes

Although the sol-gel method is ideally suited for the preparation of ferroelectric PZT thin films, poor reproducibility and the need to lower crystallization temperatures remain an issue. To address these problems, we have studied the mechanism of thin film formation using absorption-reflection infrared spectroscopy for a novel and less harmful precursor solution system based on butoxyethanol. By recording in situ infrared spectra we were able to monitor hydrolysis, condensation, decomposition and crystallization phenomena versus temperature. We speculate that the lower reactivity of butoxyethanol is responsible for the higher quality of Ti rich PZT based ferroelectric capacitors prepared by a butoxyethanol precursor solution compared with the more widely used methoxyethanol one. Finally, we observed that film's decomposition kinetics is faster as compared to bulk samples and depends on film thickness and electrode layer.     

Dielectric and Pyroelectric Properties of Compositionally Graded Pb(Zr1-xTix)O3 Thin Films Prepared by Sol-gel Process

"Compositionally graded ferroelectric lead zirconate titanate Pb(Zr1-xTix)O3 (PZT) thin films were grown on Pt/Ti/SiO2/Si substrates by using a sol-gel process. The final structure consists of six layers, up-graded graded films starting from PbZrO3 on the Pt electrode to the top PZT(50) layer, it consists of no Ti, 10%Ti, 20%Ti, 30%Ti, 40%Ti, and 50%Ti respectively. Whereas films with opposite gradient are called down-graded graded films. Structure and dielectric properties of the graded films was investigated by X-ray diffraction, Auger electron spectroscopy and by impedance analysis. The up-graded and down-graded PZT films annealed at 600 o, exhibited the remanent polarization values of 18.0 and 24.2 1C/cm2, respectively. The typical small signal dielectric constants and loss tanffi at a frequency of 100 Hz were 523 and 0.018, 544, and 0.020, respectively, for up-graded and down-graded PZT thin films. The temperature dependence of pyroelectric coeoients of the graded PZT films was measured by a dynamic technique. From 20 o to 82 o, the pyroelectric coeoients of the up-graded and down-graded PZT films up to 374 and 407 1C/m2K, respectively."     

LaNiO3衬底上Pb(ZrxTi1－x)O3铁电薄膜及梯度薄膜的制备和研究

报道了在镍酸镧 (LaNiO₃, 简称LNO)衬底上锆钛酸铅 [Pb(Zr_xTi_1－x)O₃, 简称PZT]铁电薄膜及其成分梯度薄膜的结构、介电性能、铁电性能以及热释电性能. 首先通过金属有机化合物热分解(MOD)法在Si(100)基片上制备出LaNiO₃, 薄膜, 再通过溶胶-凝胶(sol-gel)法, 在LNO/Si(100)衬底上制备出Pb(Zr_0.80Ti_0.20)O₃, [PZT(80/20)]和Pb(Zr_0.20Ti_0.80)O₃, [PZT(20/80)]铁电薄膜及其成分梯度薄膜. 经俄歇微探针能谱仪(AES)对制备的梯度薄膜进行了成分深度分析, 结果证实成分梯度的存在. 经XRD分析表明, 制备的梯度薄膜为四方结构和三方结构的复合结构, 但其晶面存在一定的结构畸变. 经介电频谱测试表明, 梯度薄膜的介电常数比每个单元的介电常数要大, 但介电损耗相近. 在10 kHz下, 梯度薄膜的介电常数和介电损耗分别为317和0.057. 经电滞回线的测试表明, 梯度薄膜的剩余极化强度比每个单元都大, 而矫顽场却明显较小. 梯度薄膜的剩余极化强度和矫顽场分别为29.96 μC•cm^-2 和54.12 kV•cm^－1. 经热释电性能测试表明, 室温下梯度薄膜的热释电系数为5.54×10-8 C•cm^－2•K^－1, 高于每个单元的热释电系数.     

Ageing and fatigue of lead titanate and lead zirconate titanate thin ferroelectric films

The phenomena of ageing and fatigue have been experimentally investigated in lead titanate and lead zirconate titanate thin ferroelectric films for samples on different substrates and with different materials of the measuring electrodes. A certain broadening of the dielectric permittivity peak is observed for the films on the silicon substrate after a year keeping without external actions. The lead titanate films on corundum substrates did not demonstrate visible changes in structural and dielectric parameters in the course of this time. In the course of repeated cycling the reduction of switching polarization in the lead titanate and lead zirconate titanate films on silicon substrates takes place at considerably greater number of cycles as compared to the same films on corundum substrates under the identical conditions. The above changes of dielectric and switching characteristics can be relevant to the changes in the domain structure of the materials under investigation in the process of their ageing and repeated switching. The reason for the acceleration of the ageing processes in the films on corundum substrates could be either an increase in the absolute magnitude of the switching field or an increase of the internal bias field, that facilitate the migration of oxygen vacancies in the films with the perovskite structure to the electrode–ferroelectric surface with the consequent fixation of domain walls.     

Magnetostatic Coupling in CoFe2O4/Pb(Zr0.53Ti0.47)O3 Magnetoelectric Composite Thin Films of 2-2 Type Structure

CoFe₂O₄/Pb(Zr_0.53Ti_0.47)O₃ (CFO/PZT) magnetoelectric composite thin films of 2-2 type structure had been prepared onto Pt/Ti/SiO₂/Si substrate by a sol-gel process and spin coat-ing technique. The structure of the prepared thin film is substrate/PZT/CFO/PZT/CFO. Two CFO ferromagnetic layers are separated from each other by a thin PZT layer. The upper CFO layer is magnetostatically coupled with the lower CFO layer. Subsequent scan-ning electron microscopy (SEM) investigations show that the prepared thin films exhibit good morphologies and compact structure, and cross-sectional micrographs clearly display a multilayered nanostructure of multilayered thin films. The composite thin films exhibit both good magnetic and ferroelectric properties. The spacing between ferromagnetic layers can be varied by adjusting the thickness of intermediate PZT layer. It is found that the strength of magnetostatic coupling has a great impact on magnetoelectric properties of composite thin films, i.e., the magnetoelectric voltage coefficient of composite thin film tends to increase with the decreasing of pacing between two neighboring CFO ferromagnetic layers as a result of magnetostatic coupling effect.     

PMN-PT thin films grown by sputtering on silicon substrate: influence of the annealing temperature on the physico-chemical and electrical properties of the films

Studies of piezoelectric and electrostrictive properties of (1?x)PMN-xPT thin films were carried out. We have chosen the compositions 90/10 and 70/30, which exhibit, respectively, mostly electrostrictive and piezoelectric behaviour in bulk material. Annealing temperature effects on PMN-PT structural, dielectric, ferroelectric and electromechanical properties have been investigated. We demonstrate that with conventional annealing the pure perovskite phase can be obtained at very low temperature (400°C) without any pyrochlore phase for the two compositions. We show that electromechanical response is a mix between electrostrictive and piezoelectric response for the two compositions. However, as can be easily understood, piezoelectric contribution is larger for 70/30. It is shown that electrical responses of the films obtained at 400°C are largely satisfied for many applications; for higher annealing temperature we observe an enhance of the electrical properties due to an improvement of the material quality in terms of crystalline structure.     

Ferroelectric ceramics by sol–gel methods and applications: a review

New advances in the sol?Cgel processing of ferroelectric ceramic powders and thin films and recently, scientific and technological interests in ferroelectric ceramics have been focused particularly on thin films. This is mainly due to their great potential applications in integrated electronics as passive components and as non-volatile ferroelectric memories, optoelectronic devices, etc. Special attention has been paid to the effects of the microstructure and composition on the piezoelectric properties of ferroelectric ceramic powders and thin films, and various characterization techniques are reported. This paper introduces the basic principles governing ferroelectricity and lists the various materials which exhibit these properties. The processing of ferroelectric ceramics and thin films in general and sol?Cgel processing in particular, with some examples are described. Finally, important applications of ferroelectric films and microstructure examination as well as powerful techniques are briefly discussed.     

Lead Zirconate Titanate Stable Stock Solution: Characterization and Applications

Lead zirconate titanate (PZT) thin films were prepared by the sol-gel process using acetic acid and 1,2-propanediol as solvents. Acetone was used as final solvent and in this way a stable stock sol (for more than 12 months) was obtained. The PZT sols prepared were reproducible and suitable for the preparation of PZT thin films. To study the sol structure evolution gas chromatography mass spectrum (GC-MS) and Fourier-transform-infrared (FT-IR) spectra were recorded and analyzed on each step of the synthesis. The rheological behavior and the stability of the stock sol were checked using a rheometer. It is observed that the addition of acetone leads to a very stable stock sol. The preliminary investigation of the electric properties of the obtained PZT thin films showed that the crystallized films deposited from a fresh prepared sol and a 12 months aged sol exhibit similar ferroelectric properties and comparable to those reported in the literature.     

Micropatterning of the Ferroelectric Phase in a Poly(vinylidene difluoride) Film by Plasmonic Heating with Gold Nanocages

Polymer thin films with patterned ferroelectric domains are attractive for a broad range of applications, including the fabrication of tactile sensors, infrared detectors, and non‐volatile memories. Herein, we report the use of gold nanocages (AuNCs) as plasmonic nanostructures to induce a ferroelectric–paraelectric phase transition in a poly(vinylidene fluoride) (PVDF) thin film by leveraging its photothermal effect. This technique allows us to generate patterned domains of ferroelectric PVDF within just a few seconds. The incorporation of AuNCs significantly enhances the pyroelectric response of the ferroelectric film under near‐infrared irradiation. We also demonstrate the use of such patterned ferroelectric films for near‐infrared sensing/imaging.     

Combinatorial synthesis of thin mixed oxide films and automated study of their piezoelectric properties

The development of an automated production of thin films and the characterization of their piezoelectric properties in high-throughput are described. A library of 50 undoped as well as doped lead zirconate titanate Pb(Zr,Ti)O₃ (PZT) coatings was produced by sol deposition. Afterwards, the piezoelectric properties of the library films were analyzed by automated atomic force microscopy employing the ultrasonic piezo-mode.     

Accelerate ageing of PZT-type ceramics

Accelerate ageing of lead zirconate–titanate ferroceramics (PZT) by fast neutron irradiation is investigated. The ferroelectric behavior of Pb_1−wM_w(Zr,Ti)O₃, where w < 0.5 wt%, M = Li, Nb, Cr, Bi, Mn, Sb, La for Zr/Ti ratio = 51.5/48.5, prepared by solid state reaction, is strongly affected by fast neutron irradiation at Φ_i = (10¹³ ÷ 10¹⁸) n/cm² integrated fluxes. Structural investigations (XRD and SEM) reveal modifications of the microstructure, porosity and elementary cell parameters. High irradiation levels induce tetragonal-cubic at the same time with a ferro–paraelectric transition. The micrographs show the evolution of 90° and 180° walls as well as herringbone structure typical for tetragonal distortions with irradiation level. A relation between macroscopic characteristics (piezoelectric and dielectric) and microscopic properties (crystallographic parameters, porous structure and grain morphology) as function of irradiation doses can be established using a model based on microstructural parameters. These results offer opportunities to understand the fundamentals of radiation effects upon piezoelectric ceramics.     

Effect of post-metallization annealing on the ferroelectric properties of sol-gel derived PZT thin films

A series of monolithic Pt-PZT-Pt capacitors was prepared based on sol-gel derived PZT 53/47 films fired to 700 C. After deposition of top Pt electrodes, the capacitors were subjected to post-metallization annealing (PMA) temperatures of 100 C to 700 C. Dielectric and ferroelectric (FE) characterizations were performed. Increasing the PMA temperature produced lower values of spontaneous and remanent polarizations, dielectric constant and leakage currents. The observations are correlated with a proposed FE capacitor model.     

Microstructure and ferroelectric properties of r.f. magnetron sputtering derived PZT thin films deposited on interlayer (PbO/TiO2)

Lead zirconate titanate (PZT) thin films were deposited on Pt/Ti/SiO₂/Si and interlayer/Pt/Ti/SiO₂/Si substrate by radio frequency (r.f.) magnetron sputtering with a Pb_1.1Zr_0.53Ti_0.47O₃ target. The crystallization of the PZT thin films was formed only by substrate temperature. When interlayer (PbO/TiO₂) was inserted between the PZT thin film and the Pt electrode, the grain growth and processing temperature of the PZT thin films were considerably improved. Compared to PZT/Pt structure, the dielectric constant and polarization properties of the PZT/interlayer/Pt structure were fairly improved. In particular, PZT/interlayer/Pt at the substrate temperature of 400 °C showed prevalent ferroelectric properties (_r=475.97, tanδ=0.0591, P_r=23 μC/cm²). As a result of an X-ray photoelectron spectroscopy (XPS) depth-profile analysis, it was found that PZT/interlayer/Pt deposited only by substrate temperature without the post-annealing process via r.f. magnetron sputtering method remained independent of each other regardless of substrate temperatures.     

Glycol-based sol-gel process for the fabrication of ferroelectric PZT thin films

A new sol-gel system using ethylene glycol was developed for the fabrication of PZT thin films with compositions near the morphotropic phase boundary Pb(Zr_0.52Ti_0.48)O₃. Ethylene glycol was used as both a chelating agent and a solvent to replace the highly toxic methoxyethanol used in previous formulations. Thin films were deposited by spin coating the solutions onto platinized silicon substrates. Films were completely crystallized by about 600°C and contained the ferroelectric perovskite phase. A dielectric constant of about 750–800 at 1 KHz was obtained for thin films of 0.3 µm thickness. The hysteresis measurements revealed a remanent polarization of 15 mC/cm² with a coercive field of 60 kV/cm.     

Polyamide-11/lead zirconate titanates—a novel composite material with high dielectric properties

Polymeric composites gain increasing interest in materials research and practice applications due to combining excellent electric property of piezoelectric ceramic and flexibility of polymer matrix. A novel decoupling capacitor with high dielectric constant has been developed by mixing polyamide-11 (PA11) with ferroelectric ceramic lead zirconate titanates (PZT). The composite demonstrates high dielectric constant, with better frequency stability and low dielectric losses. The dependence of the dielectric constant on frequency and polymer fraction was investigated. The excellent dielectric constant of 100 and the dielectric loss of 0.1 can be obtained at a PA11 volume fraction of 0.4. The enhanced dielectric behavior originates from good connection between ferroelectric ceramic and PA11 Dielectric losses of the PZT/PA11 composites change slightly with the test frequency. Our findings suggest that the created polymeric composites with relatively high dielectric constant represent a novel type of material that is flexible and easy to process. Moreover, is suited to applications in advanced decoupling capacitors and flexible electronics.     

Doped liquid nitrobenzene is ferroelectric

The high resolution hyper-Rayleigh light scattering spectrum for liquid nitrobenzene doped with triflic acid (CF(3)SO(3)H) shows a narrow spike at zero frequency shift which has the polarization signature of a polar longitudinal collective mode. This spectral spike disappears for pure nitrobenzene. The spectral spike is interpreted as due to ferroelectric domains in the liquid. The dopant molecules appear to induce ferroelectric organization of the nitrobenzene molecules which is otherwise absent in the pure liquid. Estimated domain size is 34 nm and relaxation time is 50 ns.     

Control of microstructure and functional properties of PZT thin films via UV assisted pyrolysis

The influence of ultraviolet (UV) light during pyrolysis of sol-gel fabricated Pb(Zr_0.52Ti_0.48)O₃ thin films on (111)Pt/Ti/SiO₂/Si substrates has been investigated. The UV treated films show a homogeneous fine grain structure with (100) preferential orientation, whereas a bimodal grain structure and (111) preferential orientation were found for the untreated film. This is explained in terms of specific template layers formed during pyrolysis. The ferroelectric, dielectric and piezoelectric properties are also reported for both films. It is shown that while the ferroelectric properties are higher for the (111) films, the (100) films show better dielectric and piezoelectric properties with an effective piezoelectric coefficient, d _33eff, of 183 pm/V vs. 101.8 pm/V for the (111) films.     

Improving ferro- and piezo- electric properties of hydrogenized poly(vinylidene fluoride-trifluoroethylene) films by annealing at elevated temperatures

After annealing the solution cast P(VDF-TrFE) films at elevated temperatures, which were synthesized via a full hydrogenation process from P(VDF-CTFE) with a composition of VDF/TrFE = 80/20(mol%), a series of P(VDF-TrFE) films were fabricated in present work. The crystalline and ferroelectric phases of the films were carefully characterized and their dielectric, ferroelectric and piezoelectric properties were systematically investigated. The improved crystalline and ferroelectric phases in the films induced by annealing at elevated temperatures are responsible for the significant improved electric properties of the films. The optimized annealing temperature is found to be 130 °C and the best performance including the highest dielectric constant of 12.5 at 1 kHz, the largest maximum polarization of 11.21 μC/cm~2 and remnant polarization of 7.22 μC/cm~2, the lowest coercive electric field of 56 MV/m, and the highest piezoelectric coefficient of -25 pC/N is observed.