PMN-PT Thin Films Research Articles

Sm and Mn doped enhancing the electrical properties of .68PMN–.32PT relaxor ferroelectric thin films

Abstract(1−x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMN–PT) has attracted attention due to its excellent electrical properties as a typical relaxor ferroelectric material. High‐quality Mn–Sm co‐doped 0.68PMN–0.32PT thin films were synthesized on the Pt/Ti/SiO2/Si substrates by sol–gel based on spin coating method. The results show that 1 mol% Mn–2 mol% Sm co‐doped PMN–PT thin films have high dielectric constant (εr ∼ 1895) and relatively low dielectric loss (tanδ ∼ .039) at 1 kHz. They also show superior ferroelectric polarization (Pmax ∼ 53.71 μC/cm2, Pr ∼ 30.85 μC/cm2) and high dielectric breakdown strength (∼1656.6 kV/cm), which are primarily due to the low leakage current density (∼10−7 A/cm2). This work suggests a practical approach to enhance the dielectricity, piezoelectricity, and ferroelectricity of PMN–PT thin films.

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.

Non-stoichiometry and its implications for the properties of PMN–PT thin films

0.67[Pb(Mg1/3Nb2/3)O3]–0.33[PbTiO3] (PMN–33PT) epitaxial thin films were prepared by pulsed-laser deposition (PLD) using ceramic targets, enriched with PbO (and MgO).

Misfit-Strain Phase Diagram, Electromechanical and Electrocaloric Responses in Epitaxial PIN-PMN-PT Thin Films.

xPb(In1/2Nb1/2)O3-(1-x-y)Pb(Mg1/3Nb2/3)O3-yPbTiO3 (PIN-PMN-PT) bulks possess excellent electromechanical coupling and dielectric properties, but the corresponding epitaxial PIN-PMN-PT thin films have not yet been explored. This paper adopts a nonlinear thermodynamics analysis to investigate the influences of misfit strains on the phase structures, electromechanical properties, and electrocaloric responses in epitaxial PIN-PMN-PT thin films. The misfit strain-temperature phase diagram was constructed. The results reveal that the PIN-PMN-PT thin films may exist in tetragonal c-, orthorhombic aa-, monoclinic M-, and paraelectric PE phases. It is also found that the c-M and aa-PE phase boundaries exhibit a superior dielectric constant ε11 which reached 1.979 × 106 with um = -0.494%, as well as the c-M phase boundary showing a large piezoelectric response d15 which reached 1.64 × 105 pm/V. In comparison, the c-PE and M-aa phase boundaries exhibit a superior dielectric constant ε33 over 1 × 105 around um = 0.316% and the piezoelectric response d33 reached 7235 pm/V. The large electrocaloric responses appear near the paraelectric- ferroelectric phase boundary. These insights offer a guidance for experiments in epitaxial PIN-PMN-PT thin films.

Polarization in pseudocubic epitaxial relaxed PMN-PT thin films

Understanding the relationship between structural characteristics and functional properties of complex relaxor ferroelectric thin films is of high interest for designing materials with high performances. In this work, the structure of epitaxial relaxed pulsed-laser-deposited Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT; x = 25, 33, and 40) thin films on LaNiO3/SrTiO3 substrates is analyzed using a variety of diffraction and spectroscopic techniques. While based on the data obtained from high-resolution x-ray diffraction and scanning transmission electron microscopy analysis, the average structure of the PMN-xPT films is metrically cubic, micro-Raman polarimetry measurements indicate the tetragonal-like ferroelectric phase with marked preference for the polarization perpendicular to the film for all three compositions. The results of the Raman scattering analysis are supported by electromechanical properties of the samples, which clearly show that the films have a locally non-centrosymmetric structure. Furthermore, only a gradual enhancement of the electrical properties from PMN-25PT to PMN-40PT is observed, which is attributed to small tetragonal distortions that are highly similar for all three compositions.

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.

Ferroelectric-Ferromagnetic Heterostructures based on Sodium Substituted Lanthanum Manganite Thin films deposited on PMN-PT substrate by Pulsed Laser Deposition

Phase pure targets of sodium substituted lanthanum manganites (LNMO) were prepared by citrate gel method and characterized. These targets were laser ablated by pulsed laser deposition technique and were deposited simultaneously on silicon and relaxor ferroelectric PMN-PT substrates with a view to fabricating ferroelectric-ferromagnetic 2D heterostructures. Magnetization measurements reveal a higher magnetization for films of 100 nm thickness than the 300 nm thick films. The PMN-PT substrate influences the magnetic properties of sodium substituted lanthanum manganite thin films. The strain effects are higher for 100 nm thin films. The saturated polarization-electric field (P-E) loop measurements carried out on films demonstrated that, there is a considerable change in hysteresis parameters (coercivity and remanent polarization) upon thin film deposition. PMN-PT LNMO thin films can be viewed as a heterostructure where ferromagnetism and ferroelectricity co-exist and has potential applications in magnetoelectrics.

Enhanced dielectric, ferroelectric, and optical properties in rare earth elements doped PMN-PT thin films

Rare earth (RE = La3+, Sm3+, Pr3+) ion doped Pb(Mg1/3Nb2/3)O3-PbTiO3 (RE-PMN-PT) ferroelectric thin films with compositions near the morphotropic phase boundary were grown on the Pt/TiO2/SiO2/Si(100) substrate using sol-gel/spin coating method. The phase structure, electrical properties, and photoluminescence performance of thin films were investigated systematically. The highly (100)-preferred orientation was obtained in pure perovskite Sm-PMN-0.30PT thin films with an average grain size of 131 nm. After 2.5% Sm3+ doping, the PMN-0.30PT thin films exhibited a triple enhancement of dielectric permittivity with a maximum value of 3500 at 1 kHz, a low dielectric loss of 1.3%, and high remanent polarization of 17.5 μC/cm2 at room temperature. In visible light and near-infrared band, the transmittance rate increased with PT content and showed the highest value of 85% in 2.5%Sm-PMN-0.31PT. In addition, the films presented strong red-orange emission at 599 nm, which was sensitively in temperature range of 248–273 K corresponding to the rhombohedral to monoclinic phase transition temperature.

Micro-machining of PMN-PT Crystals with Ultrashort Laser Pulses

Lead–magnesium niobate lead titanate (PMN-PT) has been proven as an excellent material for sensing and actuating applications. The fabrication of advanced ultra-small PMN-PT-based devices relies on the availability of sophisticated procedures for the micro-machining of PMN-PT thin films or bulk substrates. Approaches reported up to date include chemical etching, excimer laser ablation, and ion milling. To ensure an excellent device performance, a key mandatory feature for a micro-machining process is to preserve as far as possible the crystalline quality of the substrates; in other words, the fabrication method must induce a low density of cracks and other kind of defects. In this work, we demonstrate a relatively fast procedure for the fabrication of high-quality PMN-PT micro-machined actuators employing green femtosecond laser pulses. The fabricated devices feature the absence of extended cracks and well-defined edges with relatively low roughness, which is advantageous for the further integration of nanomaterials onto the piezoelectric actuators.

Synthesis, Giant Dielectric, and Pyroelectric Response of [001]-Oriented Pr3+ Doped Pb(Mg1/3Nb2/3)O₃-PbTiO₃ Ferroelectric Nano-Films Grown on Si Substrates.

The [001]-oriented Pr3+ doped Pb(Mg1/3Nb2/3)O3-0.30PbTiO3 (Pr-PMN-PT) thin films with a composition near the morphotropic phase boundary (MPB) were synthesized by a sol–gel method. The crystal structure was characterized using X-ray diffraction. It was found that a single perovskite phase was achieved in Pr-PMN-PT thin films annealed at 650 °C for 3 min. The dielectric constant (εr) value was 2400 in 2.5% Pr-PMN-PT thin films at room temperature, 110% higher than that of pure PMN-PT samples. Through 2.5% Pr3+ doping, remanent polarization (Pr) and coercive field (Ec) values increased from 11.5 μC/cm2 and 35 kV/cm to 17.3 μC/cm2 and 63.5 kV/cm, respectively, in PMN-PT thin films. The leakage current densities of pure and 2.5% Pr-PMN-PT thin films were on the order of 1.24 × 10−4 A/cm2 and 5.8 × 10−5 A/cm2, respectively, at 100 kV/cm. A high pyroelectric coefficient (py) with a value of 167 μC/m2K was obtained in 2.5% Pr-PMN-PT thin films on Si substrate, which makes this material suitable for application in infrared detectors.

Monolithically Integrated Microelectromechanical Systems for On-Chip Strain Engineering of Quantum Dots.

Elastic strain fields based on single crystal piezoelectric elements represent an effective way for engineering the quantum dot (QD) emission with unrivaled precision and technological relevance. However, pioneering researches in this direction were mainly based on bulk piezoelectric substrates, which prevent the development of chip-scale devices. Here, we present a monolithically integrated Microelectromechanical systems (MEMS) device with great potential for on-chip quantum photonic applications. High-quality epitaxial PMN-PT thin films have been grown on SrTiO3 buffered Si and show excellent piezoelectric responses. Dense arrays of MEMS with small footprints are then fabricated based on these films, forming an on-chip strain tuning platform. After transferring the QD-containing nanomembranes onto these MEMS, the nonclassical emissions (e.g., single photons) from single QDs can be engineered by the strain fields. We envision that the strain tunable QD sources on the individually addressable and monolithically integrated MEMS pave the way toward complex quantum photonic applications on chip.

Room-temperature magneto-dielectric response in multiferroic ZnFe2O4/PMN-PT bilayer thin films

The magneto-dielectric response in multiferroic ZnFe2O4/PMN-PT bilayer thin films prepared on a glass substrate using RF magnetron sputtering has been investigated in this work. PMN-PT thin films (i.e. PMN-PT/LCMO/Pt/Ti/glass) deposited on glass were used as a substrate for deposition of ZnFe2O4 thin films. ZnFe2O4 thin films were annealed ex situ at different temperatures. Structural, magnetic, ferroelectric, dielectric and magneto-dielectric studies were carried out on these multiferroic bilayer thin films. Structural studies revealed the presence of each layer in its respective single phase. Magnetic and ferroelectric studies revealed the ferromagnetic and ferroelectric behaviors of these bilayers. To quantify the magnetoelectric coupling, the dielectric constant of the bilayer was measured at room temperature as a function of frequency with and without the applied magnetic field. The magneto-dielectric response MD(%) was calculated by finding the relative change in dielectric constant at 1 kHz as a percentage. The observed MD response was correlated with magnetization of the ferrite layer. An MD response of 2.60% was found for a bilayer film annealed at 350 °C. At this particular annealing temperature, the ZnFe2O4 layer also has the highest saturation magnetization of 1900 G.

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.

Effect of Ti concentration on the growth of chemically-ordered regions of Pb(Mg<sub>1/3</sub>Nb<sub>2/3</sub>)O<sub>3</sub>–PbTiO<sub>3</sub> epitaxial thin films

(1 − x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMN–PT) (x = 0–1) epitaxial thin films with high crystallinity have been prepared by using metallo-organic decomposition (MOD) processes at a temperature half of the crystallization temperature of the corresponding bulk crystals. X-ray diffraction patterns show that Ti-poor and Ti-rich PMN–PT thin films have perovskite-type structure with a single phase of pseudocubic and/or tetragonal phase, respectively. The morphotropic phase boundary (MPB) is located around x = 0.6. Chemically-ordered regions (CORs), where Mg and Nb ions at B-sites show 1:1 ordered structure in the 〈111〉 directions, are clearly detected by using aberration-corrected high angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) images taken along the 〈110〉 directions, while it is difficult to analyze the detailed structure of the CORs by the electron or X-ray diffraction methods owing to the small volume. It showed that the density of COR rapidly decreases with increasing the Ti concentration, keeping the size of each COR, which infers that the COR may vanish at the Ti composition less than MPB. STEM analysis around the film/substrate interface shows the elastic interaction between CORs and local strain fields would be weak.

Effects of synthesis conditions on electrical properties of chemical solution deposition-derived Pb(Mg1/3Nb2/3)O3–PbTiO3 thin films

Relaxor ferroelectrics Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) have attracted considerable attention because of their excellent electrical properties, which include high dielectricity and piezoelectricity. Their thin films are promising for use as super capacitors and piezoelectric actuators. However, the reported electrical properties of PMN–PT thin films, such as dielectric and piezoelectric properties, are markedly lower than those of bulk ceramics and single-crystals. This study investigated the effects of synthesis conditions such as annealing temperatures, excess lead amounts, and the molecular design of the precursor solution on the electrical properties of the Chemical Solution Deposition (CSD)-derived PMN–PT thin films to deposit single-phase perovskite PMN–PT thin films with superior electrical properties on a Si substrate at lower temperatures. Results of studies demonstrated effectively that suitable processing is necessary to elicit the enhanced electrical properties of PMN–PT thin films, such as introduction of suitable seeding layers and optimization of synthesis conditions. Results show that CSD-derived polycrystalline 0.65PMN–0.35PT thin films with preferred orientation exhibited a higher dielectric constant over 4000 (1kHz, at room temperature) and higher remanent polarization of Pr=27.7μC/cm2 (1000kV/cm, at room temperature) as well as a higher electrostrictive constant of d33 about 200pm/V. Further investigation and development are expected to improve these electrical properties of the PMN–PT thin films by stress engineering or residual stress.

Effects of Oxide Seeding Layers on Electrical Properties of Chemical Solution Deposition-Derived Pb(Mg1/3Nb2/3)O3–PbTiO3 Relaxor Thin Films

Relaxor ferroelectrics Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) have attracted considerable attention because of their excellent electrical properties, such as high dielectricity and piezoelectricity, for application to super capacitors, piezoelectric actuators, and so on. It is well known that the electrical properties of ferroelectric thin films depend on several parameters, such as crystal orientation, composition, and residual stress. In this study, the effects of the lead titanate and lanthanum nickel oxide seeding layers on the film orientation, electrical properties, and low-temperature crystallization behavior were investigated for Chemical Solution Deposition (CSD)-derived PMN–PT thin films. As a result, PMN–PT thin films with (001)C- and (111)C-preferred orientations were successfully obtained by designing the seeding layers. Both thin films exhibited very good ferroelectricity because of their good crystallinity and preferred orientation.

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.

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.

Low-Temperature Processing of High-Performance 0.74Pb(Mg1/3Nb2/3)O3-0.26PbTiO3 Thin Films on La0.6Sr0.4CoO3-Buffered Si Substrates for Pyroelectric Arrays Applications

To prepare high-performance ferroelectric thin films on Si substrates for pyroelectric arrays applications, 0.74Pb(Mg1/3Nb2/3)O3–0.26PbTiO3 (PMN–PT) thin films, with composition beyond morphotropic phase boundary, were deposited by radio-frequency magnetron sputtering. Conductive perovskite La0.6Sr0.4CoO3 with resistivity of about 20 μΩ cm was used as a buffer layer between PMN–PT and Pt/Ti/SiO2/Si substrates to promote perovskite phase formation for the PMN–PT thin films. The PMN–PT thin films with pure perovskite phase have been obtained at temperatures as low as 500°C, which is compatible with integrated circuits. The ferroelectric, dielectric, and pyroelectric properties of the films were investigated. It is found that the films exhibit a large remnant polarization of 29.2 μC/cm2 and a high pyroelectric coefficient of 9.4 × 10−4 C/m2 K at room temperature. The calculated figures of merit for current responsivity, voltage responsivity, and detectivity are 3.76 × 10−10 m/V, 0.02 m2/C, and 1.29 × 10−5 Pa−1/2, respectively. These features suggest the film a promising material for thermal imaging applications based on silicon technology.