PMN-PT Films Research Articles

Enhancement of electrical properties in Eu-doped PMN-PT thin films prepared by sol-gel method

Europium-modified Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 (xEu-PMNT) (x = 1 %, 2 %, 3 %, 4 %) thin films have been deposited on Pt/Ti/SiO2/Si substrates via sol-gel process. The purpose of this present work was to investigate Eu doping-dependent crystal orientation, microstructure, and piezoelectric behaviors of the Eu-PMNT films. X-ray diffraction (XRD) analysis shows that PMNT films exhibit (100) preferred orientation when Eu content less than 3 %, and the film doped with 4 % show (110) polycrystalline orientation accompanied by pyrochlore phase. Increasing grain size and dense microstructure are detected by Scanning electron microscope (SEM) characterization as increasing Eu concentration to 2 %. For the film with 2 % Eu-doped, superior dielectricity (εr = 1204.5, tanδ = 0.055) measured at 1 kHz and ferroelectricity (2Pr = 21.6 μC/cm2, 2Ec = 73 kV/cm) are achieved. Moreover, an enhanced piezoelectric constant (e31) of 8.2 C/m2 is obtained in the PMN-PT film doped with 2 % Eu.

Effect of a niobium-doped PZT interfacial layer thickness on the properties of epitaxial PMN-PT thin films

We are reporting on high quality epitaxial thin films of [Pb(Mg1/3Nb2/3)O3]0.67-(PbTiO3)0.33 [PMN-PT (67/33)]. These films were deposited on (001) oriented, vicinal SrTiO3 single crystal substrates, using 1 mol. % niobium-doped Pb(Zr0.52,Ti0.48)O3 (Nb-PZT) as an interfacial layer. The functional properties of the epitaxial PMN-PT (67/33) thin films were investigated as a function of the layer thickness of the Nb-PZT layer. The deposited hetero-structures are perovskite phase pure and fully (001)-oriented. The variation in Nb-PZT interfacial layer thickness results in an increasing trend change of the in-plane lattice parameter of that layer, which in turn causes a decrease in the c/a ratio of the PMN-PT film on top. The most noticeable effect related to this is a decrease in built-in-bias (imprint) voltage. Thus, the built-in bias can be tuned by changing the interfacial layer thickness. The ferroelectric capacitor properties are found to be most stable for the thinnest interfacial layers under a high number (108) of switching cycles.

Design and implementation of sequential excitation module for high fidelity piezoresponse force microscopy

The acquisition of accurate information through a contact resonance mode is critical for mapping weak electromechanical effect reliably by using piezoresponse force microscopy (PFM). However, it is very challenging to track resonance frequency shifting when the contact stiffness from the sample varies significantly. In this work, we have developed a sequential excitation (SE) module to enable high fidelity PFM. A customized discrete frequency sweep signal from an arbitrary waveform generator is used for drive excitation so that resonance frequency tracking is no longer necessary. Furthermore, the AC component of the piezoresponse is sampled by using an oscilloscope instead of using lock-in amplifiers. To accommodate high volume of data acquisition, a fast analysis method is also developed to fit the transfer function of the cantilever efficiently on the fly during scanning. Hardware implementation and data processing are described in detail. The capability of our SE module has been demonstrated on an ordinary PMN-PT film via first and second harmonic PFM, as well as a suspended freestanding MoS2 membrane that is very challenging to probe due to its substantial variation in contact stiffness.

Flexible all-inorganic Sm-doped PMN-PT film with ultrahigh piezoelectric coefficient for mechanical energy harvesting, motion sensing, and human-machine interaction

In the era of artificial intelligence and the internet of things, the emergence of flexible MICAtronics, heterostructures made by van der Waals epitaxy on layered mica, has attracted great research interest due to applications in the fields of flexible ferroelectric memory, dielectric capacitors, and others, but less effort has been dedicated to the realization of flexible piezoelectric inorganic films for energy harvesters and sensors. In this work, an all-inorganic transparent Sm-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 (Sm:PMN-PT) film has been successfully grown on Mica substrate via a simple one-step sol-gel process. The flexible film shows an ultrahigh piezoelectric coefficient d33 of 380 pm V−1 owing to the enhanced local structural heterogeneity and the weak substrate clamping effect. Simultaneously, superior flexibility is realized without sacrificing its electrical performance, as reflected by withstanding a small radius of curvature of 2 mm and even 103 mechanical bending cycles. Utilizing this Sm:PMN-PT film, the fabricated device exhibits an excellent energy harvesting performance with output voltage of 6 V, current density of 150 μA cm−2, andultrahigh force sensitivity of 5.86 V N−1. Besides, it also possesses a certain temperature resistance and favorable hydrophobicity. In practical applications, it can not only be employed to monitor body motions, including finger pressing, hand tapping, foot stepping, finger/wrist bending, and hand grasping, but also serves as a tactile sensor to record the touch of a finger to unlock a smartphone. This work demonstrates that the flexible PMN-PT based film on Mica substrate has full application potential in mechanical energy harvesting, motion sensing, and human-machine interaction.

Low-voltage magnetoelectric coupling in membrane heterostructures.

Strain-mediated magnetoelectric (ME) coupling in ferroelectric (FE)/ferromagnetic (FM) heterostructures offers a unique opportunity for both fundamental scientific research and low-power multifunctional devices. Relaxor-FEs, such as (1 − x)Pb(Mg1/3Nb2/3)O3-(x)PbTiO3 (PMN-xPT), are ideal FE layer candidates because of their giant piezoelectricity. However, thin films of PMN-PT suffer from substrate clamping, which substantially reduces piezoelectric in-plane strains. Here, we demonstrate low-voltage ME coupling in an all-thin-film heterostructure that uses the anisotropic strains induced by the (011) orientation of PMN-PT. We completely remove PMN-PT films from their substrate and couple with FM Ni overlayers to create membrane PMN-PT/Ni heterostructures showing 90° Ni magnetization rotation with 3 V PMN-PT bias, much less than the bulk PMN-PT ~100-V requirement. Scanning transmission electron microscopy and phase-field simulations clarify the membrane response. These results provide a crucial step toward understanding the microstructural behavior of PMN-PT thin films for use in piezo-driven ME heterostructures.

Effect of a thin (doped) PZT interfacial layer on the properties of epitaxial PMN-PT films

Pure perovskite phase, (001)-oriented, epitaxial thin films of (Pb(Mg1/3Nb2/3)O3)0.67-(PbTiO3)0.33 (PMN-PT) were fabricated on single crystal, (001)-oriented SrTiO3 substrates using a hard (Fe-doped) and soft doped (Nb-doped) PZT(52/48) interfacial layer. The effect of different interface layers on the structural and ferroelectric properties of the PMN-PT films was investigated in detail. A significant self-bias voltage in the PMN-PT films can be introduced by using an appropriate interfacial layer. There are significant differences in polarization for different types of doped and undoped interface layers and a doubling of the relative dielectric constant was observed for the Nb-doped interfacial layer. Device properties remain stable up to at least 108 cycles.

Strong modulation of magnetism in multiferroic CoFe2O4/0.7 Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 oxide composite films

Multiferroic magnetoelectric composite films have been becoming the research focus as the candidates for sensors, memories, spintronics and microwave devices. Compared to ferroelectric single crystal consisting of the heterostructure, the functional composite film realizes the magnetism control under only a few volts which brings the advantage of safety and low energy consumption in the memory devices. Here, the CoFe2O4/0.7PbMg1/3Nb2/3O3-0.3PbTiO3 oxide composite thin films were deposited on SrRuO3-buffered SrTiO3 substrate by pulsed laser deposition method. The structural, ferroelectric, magnetic and magnetoelectric properties have been studied respectively. The polarization reversibility of ferroelectric domain was investigated in the PMN-PT films by piezoresponse force microscopy. The coercive field of the CoFe2O4 film ranges from 900 Oe to 975 Oe under the applied direct current voltage. By performing the alternative current voltage modulated magneto-optical Kerr effect test, the dominating coupling mechanism in the composite films influenced by the CoFe2O4 film thickness was discussed. Our study indicates the potential application of electric field assisted magnetic data storage device.

Realization of 1 μm thick, crack-free and smooth PMN-PT film in the MPB through PLD: A comprehensive study

This paper presents a comprehensive study on the various hurdles and solutions in the realization of phase pure, pinhole-free and crack-free, 0.65PMN-0.35PT/LSCO/Pt/TiO2/SiO2/Si heterostructures using pulsed laser deposition. A few major inquiries were i) effect of excess PbO in the target, ii) modulation of deposition and annealing temperatures for the growth of LSCO buffer layer, iii) thickness of the buffer layer iv) effect of the flow of oxygen in the chamber during and after deposition and v) the annealing conditions; on the phase formation, morphology and leakage response demonstrated by the films. Ferroelectric response parameters viz. Psat = 47.7 μC/cm2, Pr = 20.03 μC/cm2, EC = 62.03 kV/cm and absolute area = 21460 units attest the quality of the grown film.

Effects of the buffer layer on piezoelectric and ferroelectric properties of PMN-PT film-on-Ni foil composites

With the ever increasing requirements for the structural health monitoring systems, the deposition of the piezoelectric films on the metallic or structural materials has turned out to be an important issue. Pb(Mg, Nb)O3-PbTiO3 films with different buffer layers, i.e., in situ NiO, pre-fabricated NiO and LaNiO3, were successfully deposited on the Ni foil via the chemical solution deposition. The crystal structures and electric performances showed evident dependence on the buffer layer. Pre-deposited NiO and LaNiO3 efficiently prevented the diffusion and complex reactions occurring at the interface, offered abundant nucleation sites, and thus helped the formation of pure high-qualified perovskite PMN-PT films at higher annealing temperatures.

Effects of annealing process and the additive on the electrical properties of chemical solution deposition derived 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 thin films

0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 (PMN–PT) thin films were deposited on (111)Pt/Ti/SiO2/Si substrates via the chemical solution deposition. Both of the annealing process and additive methanamide play an obvious part in the structure and electrical properties of PMN–PT films. The optimized high-qualitied PMN–PT thin film in present work is fabricated with the methanamide in the precursor and annealed at 650 °C for 20 min. The film exhibits pure perovskite phase and superior ferroelectricity. The saturation polarization Ps and remanent polarization Pr are 52.1 µC/cm2 and 18.7 µC/cm2 at 500 kV/cm with 1000 Hz. It also shows low leakage current density of approximately 1.0 × 10− 8 A/cm2 at 200 kV/cm.

Epitaxial growth of perovskite (111) 0.65PMN-0.35PT films directly on wurtzite GaN (0002) surface

PMN-PT films were deposited on GaN/sapphire substrates via pulsed laser deposition without any intermediate buffer layers, and epitaxial perovskite (111) 0.65PMN-0.35PT films on wurtzite GaN(0002) surfaces were obtained by adjusting the experimental parameters including substrates temperature and O $$_2$$ pressure. The microstructures and electrical properties of PMN-PT/GaN heterostructure were characterized by reflection high-energy electron diffraction, X-ray diffraction, atom force microscope, transmission electron microscope and polarization–electric field (P–E) measurements. The as-grown PMN-PT films exhibit highly (111) oriented perovskite crystal structure. The in-plane orientation relationship of PMN-PT film with respect to GaN is (111) $$\times$$ [11-2] PMN-PT//(0002) $$\times$$ [11-20] GaN. A domain matching epitaxy model is proposed to account for the epitaxial growth mechanism of PMN-PT on GaN. The P–E curves show typical ferroelectric characteristics, while the remnant polarization and coercive field are about 18.1 $$\upmu$$ C/cm $$^2$$ and 75 kV/cm, respectively. This work provides a good start point for the further development of advanced electronic devices based on the integration of ferroelectric PMN-PT with wide-gap GaN semiconductor.

Thickness‐dependent domain wall reorientation in 70/30 lead magnesium niobate‐ lead titanate thin films

AbstractContinued reduction in length scales associated with many ferroelectric film‐based technologies is contingent on retaining the functional properties as the film thickness is reduced. Epitaxial and polycrystalline lead magnesium niobate‐lead titanate (70PMN‐30PT) thin films were studied over the thickness range of 100‐350 nm for the relative contributions to property thickness dependence from interfacial and grain‐boundary low permittivity layers. Epitaxial PMN‐PT films were grown on SrRuO3/(001)SrTiO3, while polycrystalline films with {001}‐Lotgering factors >0.96 were grown on Pt/TiO2/SiO2/Si substrates via chemical solution deposition. Both film types exhibited similar relative permittivities of ~300 at high fields at all measured thicknesses with highly crystalline electrode/dielectric interfaces. These results, with the DC‐biased and temperature‐dependent dielectric characterization, suggest irreversible domain wall mobility is the major contributor to the overall dielectric response and its thickness dependence. In epitaxial films, the irreversible Rayleigh coefficients reduced 85% upon decreasing thickness from 350 to 100 nm. The temperature at which a peak in the relative permittivity is observed was the only measured small signal quantity which was more thickness‐dependent in polycrystalline than epitaxial films. This is attributed to the relaxor nature present in the films, potentially stabilized by defect concentrations, and/or chemical inhomogeneity. Finally, the effective interfacial layers are found to contribute to the measured thickness dependence in the longitudinal piezoelectric coefficient.

Ferroelectricity and Self-Polarization in Ultrathin Relaxor Ferroelectric Films.

We report ferroelectricity and self-polarization in the (001) oriented ultrathin relaxor ferroelectric PMN-PT films grown on Nb-SrTiO3, SrRuO3 and La0.7Sr0.3MnO3, respectively. Resistance-voltage measurements and AC impedance analysis suggest that at high temperatures Schottky depletion width in a 4 nm thick PMN-PT film deposited on Nb-SrTiO3 is smaller than the film thickness. We propose that Schottky interfacial dipoles make the dipoles of the nanometer-sized polar nanoregions (PNRs) in PMN-PT films grown on Nb-SrTiO3 point downward at high temperatures and lead to the self-polarization at room temperature with the assistance of in-plane compressive strain. This work sheds light on the understanding of epitaxial strain effects on relaxor ferroelectric films and self-polarization mechanism.

Epitaxial ferroelectric 0.3Pb(In1/2Nb1/2)O3–0.38Pb(Mg1/3Nb2/3)O3–0.32PbTiO3 thin films grown on (110)-oriented MgO substrates

Ferroelectric 0.3Pb(In1/2Nb1/2)O3–0.38Pb(Mg1/3Nb2/3)O3–0.32PbTiO3 (PIN–PMN–PT) epitaxial thin films with a perovskite phase were grown on (110)-oriented MgO substrates by sputter deposition method. The structure of the PIN–PMN–PT films was found very sensitive to the growth condition. The single perovskite phase obtained under optimized processing condition was substantially relaxed from lattice-mismatch strain down to at least 11nm in thickness due to the formation of an ultrathin interfacial layer of twin domains. Compared to other technically important relaxor ferroelectrics such as PMN–PT, the PIN–PMN–PT thin films have a higher Curie temperature and a large coercive field, which are very promising for piezoelectric applications in micro/nano-electromechanical systems.

Lateral scaling of Pb(Mg1/3Nb2/3)O3-PbTiO3 thin films for piezoelectric logic applications

The dielectric and piezoelectric behavior of 70Pb(Mg1/3Nb2/3)O3-30PbTiO3 (70PMN-30PT) thin films was studied as a function of lateral scaling. Dense PMN-PT films 300–360 nm in thickness were prepared by chemical solution deposition using a 2-methoxyethanol solvent. These phase pure and strongly {001} oriented films exhibited dielectric constants exceeding 1400 and loss tangents of approximately 0.01. The films showed slim hysteresis loops with remanent polarizations of about 8 μC/cm2 and breakdown fields over 1500 kV/cm. Fully clamped films exhibited large signal strains of 1%, with a d33,f coefficient of 90 pm/V. PMN-PT films were patterned down to 200 nm in spatial scale with nearly vertical sidewalls via reactive ion etching. Upon lateral scaling, which produced partially declamped films, there was an increase in both small and large signal dielectric properties, including a doubling of the relative permittivity in structures with width-to-thickness aspect ratios of 0.7. In addition, declamping resulted in a counterclockwise rotation of the hysteresis loops, increasing the remanent polarization to 13.5 μC/cm2. Rayleigh analysis, Preisach modeling, and the relative permittivity as a function of temperature were also measured and further indicated changes in the domain wall mobility and intrinsic response of the laterally scaled PMN-PT.

Development of high performance piezoelectric d33 mode MEMS vibration energy harvester based on PMN-PT single crystal thick film

In this paper, we present the development of the d33 mode piezoelectric MEMS energy harvester, which is made of composite cantilever beams from single crystal PMN-PT thick film, and silicon layer. The PMN-PT piezoelectric thick film is deployed to improve the coupling coefficient and electromechanical coefficient. The d33 mode harvester based on interdigital electrodes contributes to improve its energy conversion efficiency. The hybrid processes composed of wafer bonding and mechanical lapping for thinning is successfully developed to prepare the PMN-PT thick film. The experimental results show that the fabricated prototype excited at 1.5g vibration level can generate a maximum output voltage of 5.36 VP–P and corresponding power of 7.182μW at the resonant frequency of 406.0Hz. The power density is calculated as 17,181.8μWcm−3, which is superior to the devices fabricated by other technologies in the reported literature.

Converse magnetoelectric coupling in NiFe/Pb(Mg1/3Nb2/3)O3–PbTiO3 nanocomposite thin films grown on Si substrates

Multiferroic NiFe (∼30 nm)/Pb(Mg1/3Nb2/3)O3–PbTiO3(PMN–PT, ∼220 nm) bilayered thin films were grown on common Pt/Ti/SiO2/Si substrates by a combination of off-axis magnetron sputtering and sol-gel spin-coating technique. By using AC-mode magneto-optical Kerr effect technique, the change in the Kerr signal (magnetization) of the NiFe upon applying a low-frequency AC voltage to the PMN–PT film was in situ acquired at zero magnetic field. The obtained Kerr signal versus voltage loop essentially tracks the electromechanical strain curve of the PMN–PT thin film, clearly demonstrating a strain-mediated converse magnetoelectric coupling, i.e., voltage-modulated magnetization, in the NiFe/PMN–PT nanocomposite thin films.

Low-temperature preparation of self-polarized Pb(Mg1/3Nb2/3)O3–PbTiO3 films on well crystallized LaNiO3 electrodes

0.68Pb(Mg1/3Nb2/3)O-3-0.32PbTiO(3) (PMN-PT) films were deposited on [100]-oriented LaNiO3 (LNO) electrodes with two different crystallinities by a sal-gel method. A phase-pure PMN-PT film can be formed on the well crystallized LNO electrode at 500 degrees C, 100 degrees C lower than the film deposited on the LNO electrode with lower crystallinity. All the phase-pure PMN-PT films are self-polarized. With the increase of the annealing temperature from 500 to 650 degrees C, the mean piezoelectric coefficient (d(33)) of the films deposited on the well crystallized LNO electrodes increases from 11 to 257 pm/V. This phenomenon is assigned to the defect dipoles and residual stress. (C) 2013 Elsevier B.V. All rights reserved.

Effects of high pressure annealing technique on the structure, morphology and electric properties of 0.65PMN-0.35PT thin films

Thin films of 0.65PMN-0.35PT PMN=Pb (Mg1/3Nb2/3)O3 and PT=PbTiO3 with a thickness about 250 nm were prepared on LaNiO3/SiO2/Si substrates by radio frequency magnetron sputtering. The films were annealed using high pressure annealing (HPA) technique in oxygen atmosphere. Effect of HPA on the crystal structure, morphology and electrical properties of the films was studied. XRD patterns of the films indicated that PMN-PT films treated by HPA in oxygen atmosphere (annealing temperature 400℃) showed a pure perovskite phase, with highly (100) preferred orientation. The strong and sharp diffraction peak showed the better crystallization of PMN-PT thin films after HPA. SEM observations showed that a rod or bubble morphology was present on the films surface. Ferroelectric properties tests showed that the PMN-PT film annealed in oxygen atmosphere at a pressure of 4 MPa, and annealing time of 4 h had good ferroelectric properties, in which the remanent polarization (Pr) could reach 10.544 uC/cm2. The shape of electric hysteresis was better, but the leakage current was too large, which may be due to the microstructure of the films. Meanwhile, the dielectric tests indicated that PMN-PT thin films could show very good dielectric properties, and the dielectric constant (r) could reach 913, and dielectric loss (tg) was very small, only 0.065.

J212011 コンビナトリアル成膜法によるPMN-PT薄膜の組成依存性評価([J212-01]マイクロ・ナノ材料創成とそのデバイス応用(1))

In this study, we deposited Pb(Mg_<1/3>Nb_<2/3>)03-PbTi03 (PMN-PT) thin films on PbTiO_3/Pt/Ti/Si substrates by combinatorial sputtering to optimize the composition ratio of PMN-PT thin films. Compositional gradient PMN-PT thin films were deposited by multi target co-sputtering, namely combinatorial sputtering, and pyrocholre-free PMN-PT thin films with rondom orientation were prepared on PbTiO_3/Pt/Ti/Si substrates. PT compositional ratio is ranging from 0.25 to 0.57, which coverd MPB composition of bulk PMN-PT ceramics (PT = 0.33). We confirmed that relative dielectric constants increase with decreasing PT ratio in PMN-PT films. On the other hand, the PMN-PT thin films showed the maximum piezoelectric coefficients|e_<31,f>| = 7〜8 C/m^2 around PMN-0.45PT, which is shifted from MPB composition of PMN-PT bulk ceramics.