PMN Thin Films Research Articles

Low temperature processing of alkoxide-derived PMN thin films

A well-crystallized Pb(Mg1/3Nb2/3)O3 (PMN) thin film on a Si wafer was prepared using low-temperature processing with a LaNiO3 (LNO) seeding layer. The PMN thin film was crystallized at 550 °C on a LNO/Si stacking structure. Additionally, we attempted to apply the compressive residual stress to PMN layers for a Curie temperature shift. Results show that the ferroelectric property remained at room temperature. The remanent polarization increased concomitantly with increasing annealing temperature.

液相法によるPb(Mg1/3Nb2/3)O3薄膜の低温合成

液相法によるPb(Mg1/3Nb2/3)O3薄膜の低温合成

Investigation of Pb–Mg–Nb–O pyrochlore thin films for tunable material

PMN thin films have been investigated as a feasible material for tunable microwave applications. PMN thin films were deposited by RF magnetron sputtering from Pb 6MgNb 6O 22 ceramic target on platinized Si substrates. The crystallinity, thickness, surface morphology, dielectric property, and voltage tunable properties of thin films were investigated by means of X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), and an impedance analyzer. The influences of sputtering substrate temperature and post-annealing on the tunable dielectric properties of thin films were investigated. Increasing the sputtering substrate temperature and annealing temperature can significantly increase tunability; however, these relations had the limitation that overly annealing temperature degraded the tunability of the thin film. A tunability of 38% at 1100 kV/cm of dc bias field under 1 MHz was achieved for a sample sputtered at 550 °C and annealed at 700 °C.

EFFECTS OF DEPOSITION PARAMETERS AND FILM THICKNESS ON THE PHASES AND ELECTRICAL PROPERTIES OF Pb(Mg1/3Nb2/3)O3 THIN FILMS MADE BY MOCVD USING ULTRASONIC NEBULIZATION

ABSTRACT PMN thin films were deposited by MOCVD using ultrasonic nebulization and the effects of deposition parameters and film thickness on the phases and electrical properties of the PMN films were investigated. The low deposition temperature and RTA treatment were favorable to deposit the PMN films with a low content of pyrochlore phase. Excess Mg enhanced the formation of perovskite phase of PMN films also. As the film thickness was increased, the portion of pyrochlore phase in PMN films was decreased. The dielectric constant of PMN films increased with the film thickness and showed the value of 25–230.

Broad-band dielectric response of PbMg 1/3Nb 2/3O 3 relaxor ferroelectrics: Single crystals, ceramics and thin films

Data of the extensive study of dielectric response of relaxor PbMg 1/3Nb 2/3O 3 (PMN) single crystals, ceramics (standard and textured) and thin films (thickness 500 nm, sapphire substrate) in the broad frequency range (3 × 10 −3 to 10 14 Hz) were combined, summarized and analyzed. Influence of the mesoscopic structure, possible strain and defects in ceramics and thin film on both relaxational and phonon dynamics is discussed. The phonon response of PMN single crystal and thin film appears to be very similar, including the soft mode behaviour. Similar to PMN crystals, the dielectric response of PMN ceramics and films is mainly determined by relaxational dynamics of polar nanoclusters. Flipping and breathing of the clusters are assumed to be the dominant mechanisms, which can be resolved in the frequency spectra of the complex permittivity. The mesoscopic structure and defects in the ceramics do not result in any significant contribution to additional mechanisms, but influence the dynamics of nanoclusters and lead to pinning of the flipping contribution. In thin films the dielectric response due to cluster dynamics is much more reduced.

Antiphase-type planar defects in Pb(Mg1/3Nb2/3−δ)O3/SrTiO3 thin films

We fabricated epitaxial Pb(Mg1/3Nb2/3−δ)O3 (PMN) relaxor ferroelectric thin films using radio-frequency magnetron sputtering. The structure of the PMN(001) thin films evolves from tetragonal to pseudocubic as the strain is relieved with increasing the film thickness. In films of intermediate thickness, antiphase type planar defects across which atoms are displaced by 1/2[±1 ±1 0] are identified by synchrotron x-ray scattering. The planar defects appear during the course of the strain relaxation.

Preparation of Pb(Mg1/3Nb2/3)O3 Thin Films by MOCVD Using Ultrasonic Nebulization

Lead magnesium niobate (PMN) films were fabricated on Si substrates by MOCVD using the ultrasonic nebulization and their characteristics were investigated. PMN thin films deposited at 400°C were annealed in a RTA(Rapid Thermal Annealing) system at 700°C for 30 sec to improve structural and electrical properties. The crystallinity of PMN films strongly depends on the composition ratio of Pb, Mg and Nb component. PbTiO3 seed layer have a good effect on the formation of perovskite PMN films. At −20°C, the PMN films with perovskite phase act as a ferroelectrics, which show a typical butterfly type curve in the Capacitance—Voltage characteristics.

Highly Oriented Growth of a Pb(Mg1/3Nb2/3)O3 Thin Film on a Si(001) Substrate Using a TiN Buffer Layer

A highly (00l) oriented Pb(Mg1/3Nb2/3)O3 (PMN) thin film was successfully grown on a TiN buffered Si(001) substrate. The TiN buffer layer was epitaxially grown with an orientation relationship of [110](001)TiN∥[110](001)Si on Si(001) by pulsed laser deposition. The PMN films were deposited using a radio-frequency magnetron sputtering technique at 500–700°C. The crystallinity, epitaxial nature and microstructures of the fabricated multi-films were investigated using X-ray diffraction and transmission electron microscopy. It was found that a PMN thin film deposited at 650°C shows a dense columnar structure with preferential (001) orientation suggesting the possibility of growing epitaxial PMN thin films on Si substrates using a TiN buffer layer.

New sol-gel route for processing of PMN thin films

Pyrochlore free Pb(Mg1/3Nb2/3)O3 (PMN) thin films were prepared from mixed-metal precursors solutions using the sol-gel process. Lead acetate [Pb(CH3COO)2], magnesium acetate [Mg(CH3COO)2] and niobium ethoxide [Nb(C2H5O)5] were used as starting materials, while 2-isopropoxy-ethanol was chosen as solvent. The reactivity of the precursors was investigated in order to understand and control the process and thus to prevent the contamination of the PMN with the pyrochlore phase. The solution was spin-coated on TiO2/Pt/TiO2/SiO2/Si substrate. The thin films were characterized by SEM and XRD while dielectric measurements were performed on the bulk ceramic.

Ferroelectric Pb(Mg 1/3Nb 2/3)O 3 thin films by PLD at varying oxygen pressures

Oxygen deposition pressure exerts a strong impact on the structure and ferroelectric properties of Pb(Mg 1/3Nb 2/3)O 3 (PMN) thin films derived from pulsed laser ablation (PLD), when perovskite PMN films on (La 1/3Sr 2/3)MnO 3/LaAlO 3 substrates were deposited at 520 °C and oxygen pressure varied from 0.1 to 0.6 mbar. Instead of showing the cubic structure of bulk ceramic PMN, the films exhibit a tetragonal structure, as confirmed by the splitting of (002) diffraction peak into (002) and (200) peaks. The intensity ratio of (002) and (200) increases with decreasing oxygen partial pressure. Both the remnant polarization and dielectric constant of the PMN thin films increase with decreasing deposition oxygen pressure. This is attributed to the enhancement of c-domains, which exhibit a larger polarization than that of a-domains. Typical depressed semicircles were observed in Cole–Cole curves, suggesting the coexistence of polarization relaxation and space charge relaxation in the oxygen deficient PMN films.

Synchrotron X-Ray Scattering Study of the Substrate Effects on Relaxor Pb(Mg1/3Nb2/3-δ)O3/SrTiO3 Thin Films

Perovskite Pb(Mg1/3Nb2/3-δ)O3 (PMN) thin films are grown epitaxially on on-axis SrTiO3 (001) (STO), vicinal SrTiO3 (001), and MgO (001) substrates by radio-frequency magnetron sputtering. The substrate effects on the structure of PMN thin films have been studied using synchrotron X-ray scattering technique. Initially PMN films grow in two-dimensional planar layers on the STO substrates, while they grow in the form of three-dimensional (3D) islands on the MgO substrate. The surface steps on the vicinal STO encourage the 3D island growth as the film thickness increases. We also found an unexpected monoclinic phase in PMN/STO and PMN/vicinal-STO films, which has been reported in bulk Pb(Mg1/3Nb2/3)O3-35%PbTiO3 solid solution. With increasing the film thickness, the unit cell structure of PMN films transforms from tetragonal to other structures as the strain relaxes.

Pulsed laser deposition of PMN thin films

Lead magnesium niobate (Pb(Mg 1/3Nb 2/3)O 3 or PMN) thin films have been deposited on different substrates by pulsed laser deposition. Film composition was studied by secondary ion mass spectroscopy and their crystallinity by X-ray diffraction techniques. Small-signal dielectric constant and loss factor of the films have been measured as a function of temperature and frequency on structures with 3 mm diameter evaporated Au top electrodes, by using an impedance analyser. The obtained PMN films have been found polycrystalline and partially oriented, with a certain amount of secondary pyrochlore phases and interface phases which are detrimental for the overall dielectric constant and modifies the behaviour of the heterostructures. Polarization hysteresis measurements performed at different temperatures below and above the dielectric maximum temperature T m showed the persistence of polarization above T m.

Preparation of heteroepitaxial Pb(Mg 1/3Nb 2/3)O 3 (PMN) thin film by pulsed laser deposition on Si(001) substrate using La 0.5Sr 0.5CoO 3 (LSCO)/CeO 2/YSZ triple buffer

Preparation of heteroepitaxial Pb(Mg 1/3Nb 2/3)O 3 (PMN) thin films by pulsed laser deposition (PLD) was successful on Si(001) substrate using La 0.5Sr 0.5CoO 3 (LSCO)/CeO 2/YSZ triple buffer structure for the first time. Using this triple buffer, the formation of pyrochlore type compounds was completely suppressed. The heteroepitaxial growth of PMN, LSCO, CeO 2 and YSZ on Si(001) substrate was confirmed by both X-ray pole figure measurement and RHEED observation. In this work, the thickness dependency of both crystal structure and electrical properties of PMN thin film was examined as a function of the thickness of PMN between 1.6 and 130 nm. The lattice parameter and FWHM (ω scan) of PMN thin films increased with the decrease of the thickness of PMN. The current density of PMN thin film was low irrespective of the thickness of PMN (9.2×10 −7 and 2.9×10 −6 A/cm 2 for 130- and 6.3-nm-thick, respectively. Dielectric constant of heteroepitaxial PMN thin film was decreased with the thickness, which was attributed to the depletion width.

The effect of target crystallography on the growth of Pb(Mg1/3Nb2/3)O3 thin films using pulsed laser deposition

Pulsed laser deposition has been used to make two sets of lead magnesium niobate thin films grown on single-crystal h100j MgO substrates. One set was fabricated using a perovskite-rich target while the other used a pyrochlore-rich target. It was found that the growth conditions required to produce almost 100% perovskite Pb(Mg1/3Nb2/3)O3 (PMN) films were largely independent of target crystallography. Films were characterized crystallographically using x-ray diffraction and plan view transmission electron microscopy, chemically using energy dispersive x-ray analysis, and electrically by fabricating a planar thin film capacitor structure and monitoring capacitance as a function of temperature. All characterization techniques indicated that perovskite PMN thin films had been successfully fabricated.

Influence of oxygen content on dielectric and electromechanical properties of Pb(Mg1/3Nb2/3)O3 thin films

Pulsed laser deposition was used to grow Pb(Mg1/3Nb2/3)O3 (PMN) thin film planar capacitor structures. X-ray diffraction and plan-view transmission electron microscopy were used to verify PMN crystallography. The dc leakage current and ac capacitance and dielectric loss were measured as a function of temperature and frequency. Finally, crystallographic strain as a function of applied dc field was monitored in situ by x-ray diffraction. The electromechanical strain response was found to depend on the deposition conditions for each capacitor. Tensile strains of ∼0.2% and compressive strains of ∼0.35%, both parallel to the applied field, were measured for capacitors of different oxygen contents and thicknesses. Tensile strains achieved are higher than previously reported for PMN thin films or polycrystalline ceramics. We propose that the compressive strains are not an intrinsic property of the PMN. Instead they are induced by the combined effect of joule heating of the capacitor structure, caused by leakage currents, and thermal expansion mismatch between the substrate and films.

Preparation and electromechanical properties of Pb(Mg1/3Nb2/3)O3 thin film

Pb(Mg1/3Nb2/3)O3 (PMN) alkoxide precursor solutions were synthesized and used to prepare thin layers on TiO2/Pt/TiO2/SiO2/Si substrates by spin coating. Many parameters like homogeneity of the solution and appropriate processing must be controlled to minimize the pyrochlore formation. Optimization of the processing allowed highly (111)-oriented thin films to be obtained. Dielectric measurements and TEM investigations were performed and showed that PMN thin films exhibit relaxor behavior.

Raman Spectroscopic Determination of Pyrochlore-Type Compound on the Synthesis and Decomposition of Sol-Gel-Derived Pb(Mg1/3Nb2/3)O3(PMN)

Raman spectroscopy was applied to the sol-gel-derived Pb(Mg1/3Nb2/3)O3(PMN) powder and thin film. Pyrochlore-type compound which forms on the synthesis of PMN contains Mg in the formula (Pb1.86Mg0.24Nb1.76O6.5) instead of Pb1.5Nb2O6.5, Pb2Nb2O7, or Pb2.8Nb2O7.8, which have been reported in the literature to form on the synthesis of PMN. It is rather difficult to distinguish these pyrochlore-type compounds by X-ray diffraction since thed-values of these compounds are very close to each other. From the result of Raman spectroscopy, it was also clarified that the pyrochlore-type compound formed by the decomposition of PMN thin film also contains Mg in the formula (Pb1.86Mg0.24Nb1.76O6.5).

Relaxor behavior and electromechanical properties of Pb(Mg1/3Nb2/3)O3 thin films

Pb(Mg 1/3 Nb 2/3 ) O 3 (PMN) alkoxide precursor solutions were synthesized and used to prepare thin films by spin coating on TiO2/Pt/TiO2/SiO2/Si substrates. Many parameters like the use of homogeneous and stable precursor solutions and appropriate processing were used to greatly reduce the presence of the nonferroelectric pyrochlore phase. Transmission electron microscopy investigations, dielectric, electrostrictive, and direct current field induced piezoelectric measurements were carried out and have shown that PMN thin films exhibit a relaxor-like behavior.

Dielectric Properties of Sol-Gel Derived Pb(Mg1/3Nb2/3)O3–PbTiO3 Thin Films

Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN-PT) thin films were fabricated using a sol-gel method. The dielectric constant was found to be strongly dependent on the number of strong Mg–O–Nb bonds in the precursor solution. A large number of strong Mg–O–Nb bonds were formed after a long reflux time. This process resulted in PMN thin films with a large dielectric constants sometimes greater than 3000, with a loss tangent of 0.5%. Relaxor characteristics such as weak temperature dependence and weak dc bias dependence were also observed in the thin films. These results suggest that PMN-PT is an important material for thin film capacitor applications.

Characteristics of Lead Magnesium Niobate Thin Film Prepared by Sol‐Gel Processing Using a Complexing Agent

The effects of a complexing agent on the synthesis of a Pb(Mg1/3Nb2/3)O3 (PMN) solution and the dielectric properties of a PMN thin film were investigated. When triethanolamine (TEA) was used as a complexing agent, a homogeneous and stable precursor solution was synthesized in air and a crack‐free thin film with the nearly pure perov‐skite phase and an average grain size of 0.2–0.4 μm was prepared by heating at 800°C for 5 min. The PMN thin film showed a relative permittivity of 1800 and tan δ of 0.01 at room temperature. The voltage dependence of polarization for the thin film was also presented.