O3 Ferroelectric Thin Films Research Articles

Study of ferroelectric/dielectric multilayers for tunable stub resonator applications at microwaves

Tunable coplanar waveguide stub resonators deposited on various ferroelectric/dielectric heterostructures are studied in the 10-GHz band. A frequency tunability of up to ~45% is achieved under a moderate biasing field (Ebias<100kV/cm) when the resonator is printed on KTa0.5Nb0.5O3 (KTN) ferroelectric thin film alone: this comes from the large permittivity agility of the KTN material (εr(KTN) varies from ~700 to ~200). Nevertheless this also leads to significant insertion loss due to the dielectric loss of the ferroelectric material itself (tanδr(KTN)≈0.15–0.30 at 10GHz). In this paper, an original route has been considered to reduce the device loss while keeping up a high frequency tunability. It consists in associating the KTN film with a dielectric film to elaborate ferroelectric/dielectric multilayers. The Bi1.5Zn0.9Nb1.5O7−δ (BZN) oxide material is selected here for two main reasons, namely its low dielectric loss (tanδr(BZN)≈0.005–0.0075) and its moderate relative permittivity (εr(BZN)≈95–125) at 12.5GHz. The relevance of this approach is studied numerically and experimentally. We compare numerically two different heterostructures for which the ferroelectric film is grown on the dielectric film (KTN/BZN), or vice versa (BZN/KTN). A stub resonator printed on the most relevant heterostructure has been fabricated, and experimental data are discussed and compared to the numerical results.

Effects of Bi doping on dielectric and ferroelectric properties of PLBZT ferroelectric thin films synthesized by sol–gel processing

[Pb 0·95(La1 − y Bi y ) 0·05][Zr0·53Ti0·47]O3 (PLBZT) ferroelectric thin films have been synthesized on indium tin oxide (ITO)-coated glass by sol–gel processing. PLBZT thin films were annealed at a relatively low temperature of 550 °C in oxygen ambient. Effects of Bi doping on structure, dielectric and ferroelectric properties of PLBZT were investigated. Bi doping is useful in crystallization of PLBZT films and promoting grain growth. When the Bi-doping content \({\mathit{y}}\) is not more than 0·4, an obvious improvement in dielectric properties and leakage current of PLBZT was confirmed. However, when the Bi-doping content is more than 0·6, the pyrochlore phase appears and the remnant polarization P r of PLBZT thin films is smaller than that of \(\left({Pb}_{{1-x}} {\bf La}_{x}\right)\!\!\left({Zr}_{{1-y}} {Ti}_{y}\right){O}_{3}\) (PLZT) thin films without Bi doping. PLBZT thin films with excessive Bi-doping content are easier to fatigue than PLZT thin films.

Effects of Annealing Temperature on Structure and Properties of PLBZT Ferroelectric Thin Films Synthesized by Sol-Gel Processing

[Pb0.95(La0.6Bi0.4)0.05][Zr0.53Ti0.47]O3 (PLBZT) ferroelectric thin films have been synthesized on ITO-coated glass by sol-gel processing. Effects of annealing temperature on structure and properties of PLBZT have been investigated. With the increase of annealing temperature from 500°C to 550°C, the remanent polarization Pr increase slightly to the maximum value of 25.4μC/cm2 due to the improvement in crystallization of PLBZT films. However, when the annealing temperature is more than 550°C, the pyrochlore phase appear and degrade the Pr of PLBZT thin films. The lowest leakage current density of 1.8×10-9 A/cm2 can be observed in PLBZT thin films when the annealing temperature is 550°C.

Influence of pyrolysis temperature on ferroelectric properties of La and Mn co-doped BiFeO3 thin films

Bi0.9La0.1Fe0.95Mn0.05O3 (BLFMO) ferroelectric thin films were fabricated on Pt/Ti/SiO2/Si/substrates by the sol-gel process at different pyrolysis temperatures. The mass loss of BLFMO powder was investigated by thermo gravimetry analyser (TGA), and the polycrystalline structure and smooth surface of BLFMO thin films were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. The remnant polarization (Pr) of the BLFMO films pyrolyzed at 420°C is 21.2 μC/cm2 at the coercive field (Ec) of 99 kV/cm and the leakage current density is 7.1×10−3 A/cm2, which indicates that the BLFMO thin films display relatively good ferroelectric property at this temperature.

Structure and electrical properties of PZT/LNO/PT multilayer films on stainless steel substrates

PbZr0.53Ti0.47O3 (PZT) ferroelectric thin films were deposited on LaNiO3 (LNO) by sol-gel method. The PbTiO3 (PT) seed layer was deposited between the LNO buffer layer and stainless steel (SS) substrate, which effectively decreased the annealing temperature of LNO layer from 750 °C to 650 °C. X-ray diffraction (XRD) reveals that LNO layers with PT layer crystallize into a perovskite phase on annealing at 650 °C for 10 min. PZT deposited on LNO buffer layer with PT seed layer exhibits good ferroelectric property.

The threshold electric field of 180° domain switching in the misfit strain-external electric field phase diagram

The single domain treatment on the selected single grain was performed by the negative DC bias in order to obtain the single-domain state, and the opposite color contrasts within the selected grain in piezoelectric phase images of Pb(Zr0.52Ti0.48)O3 ferroelectric thin film were observed by piezoelectric force microscopy. Based on nonlinear thermodynamic theory, the a1c– and r– phases with the negative P3 component are introduced to describe the electric-generated domain switching, and the external misfit strain-electric field phase diagram and the electric field-polarization components curve are simulated at the simplification of uniform stress/electric distribution for the single-domain state of a single grain. In phase diagram, the electric field at the misfit strain –0.002 evaluated by x ray diffraction is 139 kV/cm for the phase transition from a1c– phase to c+ phase, and it is corresponding to the threshold electric field for 180° domain switching observed by the piezoelectric phase images.

&lt;i&gt;In Situ&lt;/i&gt; X-Ray Reflectivity Study of Imprint in Ferroelectric Thin Films

The structural origin of imprint in Pb(Zr,Ti)O3 (PZT) ferroelectric thin films derived by chemical solution deposition with Pt top and bottom electrodes was studied by in-situ high-resolution X-ray specular reflectivity of synchrotron radiation. Global structural parameters of density, thickness, and surface or interface roughness of each component layer in the thin film sample were obtained. No generation of interfacial layers with a different electron density from PZT and no interface roughening were observed at the interfaces of PZT and Pt during imprint. Thus, the results suggest that the imprint effect is more likely a bulk or electronic defects-related phenomenon.

Ferroelectric Polarization Effect on Al-Nb Codoped Pb(Zr0.52Ti0.48)O3/Pr0.7Ca0.3MnO3 Heterostructure Resistive Memory

This work presents the investigation of resistive switching memory in a perovskite heterostructure composed of an active Al-Nb codoped Pb(Zr0.52Ti0.48)O3 ferroelectric thin film and a semiconducting Pr0.7Ca0.3MnO3 manganite-based oxide film, both sandwiched between Pt electrodes in a parallel capacitor-like structure. Bipolar resistive switching nature was confirmed from the measured characteristics of the DC I-V hysteresis loop and resistance switching in the pulse mode. The active ferroelectric layer has been demonstrated to play a crucial role in controlling the switching memory performance (resistance state stability and high switching endurance). Ferroelectric polarization and corresponding piezoelectric effect-induced lattice strains are found to be responsible for the resistive switching characteristics in this ferroelectric/manganite heterojunction. V C 2011 The Electrochemical Society. [DOI: 10.1149/1.3556977] All rights reserved.

The Effect of La-Doped Bi4Ti3O12 Buffer Layer on Crystallinity and Ferroelectric Properties of PbZr0.58Ti0.42O3/Bi3.25La0.75Ti3O12 Multilayered Thin Films

PbZr0.58Ti0.42O3 (PZT) ferroelectric thin films with Bi3.25La0.75Ti3O12 (BLT) buffer layer of various thickness were fabricated on Pt/TiO2/SiO2/p-Si(100) substrates by rf-magnetron sputtering method. The pure PZT film showed (111) preferential orientation in the XRD patterns, and the PZT/BLT films showed (110) preferential orientation with increasing thickness of the BLT layer. There were no obvious diffraction peaks for the BLT buffer layer, for its thin thickness in PZT/BLT multilayered films. There were the maximum number of largest-size grains in PZT/BLT(30 nm) film among all the samples from the surface images of FESEM. The growth direction and grain size had significant effects on ferroelectric properties of the multilayered films. The fatigue characteristics suggested that 30-nm-thick BLT was just an effective buffer layer enough to alleviate the accumulation of oxygen vacancies near the PZT/BLT interface. The comparison of these results suggests that the buffer layer with an appropriate thickness can improve the ferroelectric properties of multilayered films greatly.

Characterization of Textured PZT Thin Films Prepared by Sol-gel Method onto Stainless Steel Substrates

ABSTRACTPbZr0.53Ti0.47O3 (PZT) ferroelectric thin films were deposited on LaNiO3 (LNO) buffered stainless steel (SS) substrates by sol-gel method. The effect of LNO buffer layer on the orientation and electric properties of PZT thin films for different thicknesses were studied. X-ray diffraction (XRD) results indicated that PZT thin films on SS substrates exhibit the (100) preferred orientation with the LNO buffer layers. Scanning electron microscope (SEM) images show that PZT thin films were well crystallized with grain size of about 100 nm. PZT thin films deposited on SS maintain the excellent ferroelectric properties with remnant polarization of about 20 μC/cm2.

Lateral piezoelectric response across ferroelectric domain walls in thin films

In purely c-axis oriented PbZr0.2Ti0.8O3 ferroelectric thin films, a lateral piezoresponse force microscopy signal is observed at the position of 180° domain walls, where the out-of-plane oriented polarization is reversed. Using electric force microscopy measurements we exclude electrostatic effects as the origin of this signal. Moreover, our mechanical simulations of the tip/cantilever system show that the small tilt of the surface at the domain wall below the tip does not satisfactorily explain the observed signal either. We thus attribute this lateral piezoresponse at domain walls to their sideways motion (shear) under the applied electric field. From simple elastic considerations and the conservation of volume of the unit cell, we would expect a similar lateral signal more generally in other ferroelectric materials, and for all types of domain walls in which the out-of-plane component of the polarization is reversed through the domain wall. We show that in BiFeO3 thin films, with 180°, 109°, and 71° domain walls, this is indeed the case.

Interface depolarization field as common denominator of fatigue and size effect in Pb(Zr0.54Ti0.46)O3 ferroelectric thin film capacitors

Dielectric, hysteresis and fatigue measurements are performed on Pb(Zr0.54Ti0.46)O3 (PZT) thin film capacitors with different thicknesses and different electrode configurations, using platinum and LaNiO3 conducting oxide. The data are compared with those collected in a previous work devoted to study of size effect by R. Bouregba et al., [J. Appl. Phys. 106, 044101 (2009)]. Deterioration of the ferroelectric properties, consecutive to fatigue cycling and thickness downscaling, presents very similar characteristics and allows drawing up a direct correlation between the two phenomena. Namely, interface depolarization field (Edep) resulting from interface chemistry is found to be the common denominator, fatigue phenomena is manifestation of strengthen of Edep in the course of time. Change in dielectric permittivity, in remnant and coercive values as well as in the shape of hysteresis loops are mediated by competition between degradation of dielectric properties of the interfaces and possible accumulation of interface space charge. It is proposed that presence in the band gap of trap energy levels with large time constant due to defects in small nonferroelectric regions at the electrode—PZT film interfaces ultimately governs the aging process. Size effect and aging process may be seen as two facets of the same underlying mechanism, the only difference lies in the observation time of the phenomena.

The Influence of Annealing Treatment on Physics and Electrical Characteristics of Ba(Zr&lt;sub&gt;0.1&lt;/sub&gt;Ti&lt;sub&gt;0.9&lt;/sub&gt;)O&lt;sub&gt;3&lt;/sub&gt; Ferroelectric Films on ITO/Glass Substrate

Perovskite Ba(Zr0.1Ti0.9)O3 (BZ1T9) ferroelectric thin films well deposited on ITO/glass substrates for applications in system-on-panel (SOP) devices are produced and investigated. The sputtering parameters of as-deposited BZ1T9 thin films were rf power of 160 W, chamber pressure of 10 mTorr, substrate temperature of 550oC, and an oxygen concentration of 40%. From the SEM cross- sectional observation, the deposition rate were about 2.5 nm/min. Additionally, the maximum dielectric constant and leakage current density of annealed BZT films under the rapid temperature annealing would be increased, as the temperature increased to 6500C. Further, the maximum remnant polarization and coercive field of BZT films were found and calculated from the p-E curves.

Focus on innovation in ceramics research in East Asia

Ceramics, as broadly defined, include all materials other than organic substances and metals, either crystalline or amorphous. They have been used by humans since early history and have contributed considerably to improving the quality of our life. In most cases, however, high-temperature treatment is necessary to prepare ceramics. This burdens the environment and there is therefore a great need for new ceramics processing methods. Recent technologically advanced ceramics are often composed of nanocrystallites, which have great potential for innovation in terms of exploring practical applications of nanomaterials and, consequently, reducing the environmental load. The ceramics industry had long flourished in Asia, particularly in East Asia, and even today, this region is leading the development of related materials. In line with these traditions, Japanese and Korean ceramics societies have been co-sponsoring seminars on ceramics since the 1980s. Having become more international in scope and context, a series of these seminars is now known as the International Japan–Korea Seminar on Ceramics. This focus issue contains eight key articles presented at the 26th International Japan–Korea Seminar on Ceramics held on 24–26 November 2009 at the Tsukuba International Congress Center. In particular, Fabbri et al review electrode materials for protonic solid-oxide fuel cells, and Kamiya et al outline the present situation and future prospects for transparent transistors, particularly those based on amorphous In-Ga-Zn-O films. Eitel et al discuss the progress in engineering high-strain lead-free piezoelectric ceramics. Kim and Kumar review a simple processing method for producing porous ceramics using polysiloxane precursors, Kamiya and Iijima focus on surface modification and characterization of nanomaterials, and Wan et al briefly review the strategy of reducing lattice thermal conductivity of thermoelectric materials and propose new materials for thermoelectric devices. Aubert et al introduce a novel technique of synthesizing composite nanomaterials and Cross and coworkers characterize Pb(Zr,Ti)O3 (PZT) ferroelectric thin films co-doped with Bi and Fe to enhance PZT capacitor ferroelectric properties. These articles are closely related to the global environmental load and energy issues that require solutions in modern ceramics technology. We hope that this focus issue will help advance not only ceramics-related but also other fields of materials science.

Laser-induced voltage effect in Pb(Zr0.3Ti0.7)O3 ferroelectric thin film

Pb(Zr0.3Ti0.7)O3(PZT)thin films have been grown by pulsed laser deposition (PLD) on LaSrAlTaO3 (LSATO),LaAlO3(LAO) and SrTiO3(STO) single crystal vicinal cut substrates. Laser-induced voltage(LIV) effect was also found in PZT thin films grown on the three vicinal cut substrates for the first time. LIV signals increased with the single-pulse laser energy following the linear relation in case of c-axis orientation of thin film; but this linear relation was not followed obviously in case of a-axis orientation of thin film. This result shows that the LIV effect in PZT thin film is the atomic layer thermopile effect, in the which anisotropy of Seebeck coefficient plays an important role. Through realizing impedance-matching of thin films and transmission line, LITV signal response time has been optimized, the time of rising edge dropped from 60 ns to 26 ns, the full width at half maximum dropped from 260 ns to 38 ns.

Dynamic hysteresis scaling of ferroelectricPb0.9Ba0.1(Zr0.52Ti0.48)O3 thin films

We measure systematically the intrinsic scaling behavior of dynamic hysteresis forPb0.9Ba0.1(Zr0.52Ti0.48)O3 (PBZT) ferroelectric thin films with Pt electrodes on Si substrates, utilizing theSawyer–Tower technique. For the as-prepared thin films of similar thickness andmicrostructure, over the low frequency range, the scaling follows the power law under low E0 and the power law under high E0,where ⟨A⟩ is thehysteresis area, and f and E0 are the frequency and amplitude of the external electric field. In the high-f range, the powerlaw for low E0 takes the form of , while that for high E0 takes the form of . It is identified that the dynamic behaviors at low frequency mainly come from theintrinsic domain reversal instead of others like the leakage current, while thedepolarization field may influence the frequency exponents at high frequency. We studythe temperature scaling of the hysteresis, indicating that the scaling under lowE0 is roughlyconsistent with the (Φ2)2 model. Finally, we argue that experimentally obtained power law scaling forPb(Zr0.52Ti0.48)O3 thin films prepared under the given conditions may not be reliable due to the polarizationfatigue effect.

Labile Ferroelastic Nanodomains in Bilayered Ferroelectric Thin Films

Bilayered Pb(Zr(1–x),Tix)O3 ferroelectric thin film heterostructures show complex ferroelastic nanodomain patterns. These ferroelastic nanodomains exist only in the upper layer, and hence are able to move under the application of an external electric field. Quantitative analysis reveals an enhanced piezoelectric coefficient of ≈220 pm V−1, rendering them attractive for a variety of electromechanical devices.

Effect of Oxygen Concentration on Characteristics of Ba(Zr0.1Ti0.9)O3 Thin Films Deposited on Indium Tin Oxide/Glass Substrates

In this study, the perovskite Ba(Zr0.1Ti0.9)O3 (BZ1T9) ferroelectric thin films deposited on indium tin oxide (ITO)/glass substrates for applications in system-on-panel (SOP) devices are produced and investigated. The optimal sputtering conditions of as-deposited BZ1T9 thin films are an rf power of 160 W, a chamber pressure of 10 mTorr, a substrate temperature of 580 °C, and an oxygen concentration of 40%. The effect of oxygen concentration on the physical and electrical characteristics of BZ1T9 thin films is determined. For different oxygen concentrations, the thickness and deposition rate are calculated by scanning electron microscopy (SEM). From polarization versus electrical field curves, the 2Pr value and coercive field of BZ1T9 thin films are determined to be 7 µC/cm2 and 250 kV/cm, respectively. In addition, the maximum dielectric constant, leakage current density, and transmittance within the ultraviolet–visible (UV–vis) spectrum are investigated.

Improvement of electrical property for Pb(Zr0.53Ti0.47)O3 ferroelectric thin film deposited by sol-gel method on SRO electrode

Pb(Zr,Ti)O3 thin films with Zr/Ti ratio of 53:47 were deposited on SRO/YSZ/Si(100) and Pt/Ti/SiO2/Si(100) substrates using the sol-gel method. The thermal process of the PZT thin films included treating two-step pyrolysis, at 300°C for 30 minutes and 400°C for 10 minutes, and annealing crystallization, at 600°C for 10 minutes in air ambient. The remnant polarization and the coercive field of the PZT/SRO/YSZ/Si were 28 μC/cm2 and 65 kV/cm2, and those of the PZT/Pt/Ti/SiO2/Si were 12 μC/cm2 and 79 kV/cm2. This indicates that the use of the metallic SRO-electrodes significantly improves electrical property of PZT piezoelectric thin film as compared with a metal-electrode Pt.

Observation of a fifth-order optical nonlinearity in Bi0.9La0.1Fe0.98Mg0.02O3 ferroelectric thin films

Ferroelectric Bi0.9La0.1Fe0.98Mg0.02O3 thin films with high optical quantity were deposited on quartz substrates by radio frequency magnetron sputtering at 650 °C. The interplay between third- and fifth-order optical nonlinearities is observed by performing Z-scans under femtosecond laser excitation with 1.60 eV photon energy. The measured third-order nonlinearities mainly originate from electronic Kerr effect and two-photon absorption (2PA), while the population redistribution assisted by 2PA leading to an equivalent stepwise χ(3):χ(1) process is the main mechanism of the fifth-order effect.