BaPbO3 Research Articles

Influence of tensile stress on the phase formation and electronicproperties of Pb(Zr,Ti)O3 film at morphotropic phase boundary

Pb(Zr0.52,Ti0.48)Nb0.04O3 (Nb-doped PZT, PZTN) films are deposited on Pt/TiOx/SiO2/Si substrates with BaPbO3(BPO) buffer layers by RF-magnetron sputtering method. The magnitudes of tensile stress in PZTN films can be changed by adjusting the thickness of BPO layer. For PZTN films with 68 nm and 135 nm-BPOs, the tensile stresses measured by 2θ-sin2ψ method are 0.786 and 0.92 GPa respectively. Enhanced ferroelectric is observed in PZTN film with raised tensile stress. The remanent polarization and the coercive field for PZTN films with tensile stresses of 0.786 GPa and 0.92 GPa are 41.2μC/cm2(70.7 kV/cm) and 44.1μC/cm2(58.1 kV/cm) respectively. The leakage current decreases from 6.57×10-7A/cm-2 to 5.54×10-8A/cm-2 while tensile stress of PZTN film is raised from 0.786 to 0.92GPa. Fine XRD scan is performed with grazing incidence geometry to investigate the phase composition of PZTN films. Rietveld analysis shows that an increased tensile stress in PZTN film can promote the amount of monoclinic phase,which may be the reason for the ferroelectric property improvement.

Stress analysis and ferroelectric properties of Pb(Zr0.52Ti0.48)0.96Nb0.04O3 thin film grown on different thickness of BaPbO3 electrodes

Pb ( Zr 0.52 Ti 0.48 ) 0.96 Nb 0.04 O 3 (PZTN) thin films were deposited on BaPbO3 (BPO) electrodes by rf-magnetron sputtering. 34, 68, 135, and 270 nm thick BPOs were adopted in this study. The preferred orientation changes from slightly (100)/(001) to slightly (101)/(110) as the BPO thickness increased. The mean grain sizes obtained by Williamson–Hall plots are 81 nm, 120 nm, 146 nm, and 90 nm, respectively. The same tendency was observed by atomic force microscopy method. In residual stress analysis, tensile stress was observed in every film. The stress magnitude is the maximum in the film with 135 nm thick BPO. Through a simple calculation, we suggest that the tensile stress in our films mainly originates from the phase transformation stresses. We also note that the ferroelectric and dielectrics properties are improved with the raise of tensile stresses. A possible reason is that the tensile stress benefits the tetragonal–monoclinic phase transition in the PZTN films with composition near morphotropic phase boundary. The other possible reason is that the raise of the tensile stress is consistent with the increasing of grain size, which decreases the grain boundary density and facilitate domain mobility.

Preparation and Characterization of BPO Film as Electrode for Using of FeRAM

Conductive perovskite BaPbO3 (BPO) films as a potential electrode material of PZT capacitors used in ferroelectric random access memory are prepared by rf magnetron sputtering. An x-ray diffractometer and standard four probe method are employed to investigate the dependence of growth conditions on crystal structure and conductivity of BPO films. It is found that BPO films with perovskite phase can be obtained at substrate temperatures above 425° C, and the sample with the lowest resistivity is obtained at 450° C under pure argon atmosphere. Using this BPO film as electrode, ferroelectric properties of BPO/PZT/BPO and Pt/PZT/BPO sandwiched structures are evaluated. Their remanent polarization and coercive field are 36.6μC/cm2 (81.3kV/cm) and 36.9μC/cm2 (89.1 kV/cm), respectively. The coercive field of the former structure is lower than that of the latter, but remanent polarizations are almost the same. In addition, the results imply that BPO electrode is helpful to improve the fatigue resistance of PZT. The reasons are discussed.

Studies on forming gas annealing treated BiFeO3 thin films and capacitors

The structure and electric properties of BiFeO3(BFO)∕BaPbO3(BPO) and Pt/BFO/BPO capacitors with forming gas annealing (FGA) treatment were investigated. X-ray diffraction patterns indicated that the annealing did not affect the structure and phase of BFO films. A degraded electric property was obtained in FGA-treated Pt/BFO/BPO films. It can be attributed to the formation of reduction and incomplete reduction of Bi+3 of BFO. Retention and fatigue properties were obtained in FGA-treated BPO/BFO/BPO capacitors. The normalized Pr loss was 22.8% after applying a voltage above 2Vc (coercive voltage) with 1011cycles. The retention behavior within 30000s is governed by the logarithmic time dependence.

Thickness-dependent retention behaviors and ferroelectric properties of BiFeO3 thin films on BaPbO3 electrodes

Bi Fe O 3 (BFO) thin films produced with varied film thicknesses ranging from 100to230nm were fabricated on BaPbO3(BPO)∕Pt∕Ti∕SiOx∕Si substrates by rf-magnetron sputtering. Saturated polarization–electrical field hysteresis loops, polarization response by pulse measurement, and retention properties were obtained for BFO films with various thicknesses on BPO. The retention behaviors of BFO demonstrate logarithmic time dependence and stretched exponential law. When the thicknesses of BFO films increase, the contribution of logarithmic time dependence to retention, the stretched exponential law becomes dominant. BFO films with thinner thickness exhibit better retention properties but possess smaller remnant polarization.

Effect of conductive BaPbO3 electrode on the structural and dielectric properties of (Pb,Ba)ZrO3 films

Highly (1 1 1)-oriented (Pb,Ba)ZrO3 (PBZ) thin films were deposited on BaPbO3(BPO) electrode at different deposition temperatures and different thicknesses. As the deposition temperature increased, the dielectric constant and tunability increased from 150 and 4% to 500 and 56%, respectively. A current transient peak observed prior to dielectric degradation can be related to oxygen vacancy migration (redistribution) with space-charge-limited current transient or modulation of the electric conductivity. We infer that an interfacial layer lying between the PBZ and BPO effectively increases the oxygen vacancy (density ∼1020 cm−3) mobility by Pb4+ diffusing into the PBZ films.

Highly (110)- and (111)-oriented BiFeO3 films on BaPbO3 electrode with Ru or Pt∕Ru barrier layers

Highly (110)- and (111)-oriented BiFeO3 (BFO) films were fabricated with BaPbO3 (BPO)∕Ru and BPO∕Pt∕Ru as electrode/barrier on Si substrates by rf-magnetron sputtering. The BPO∕Ru and BPO∕Pt∕Ru stacks both induce oriented BFO films and act as diffusion barriers. The (110)- and (111)-oriented BFO films possess excellent ferroelectric properties with only minor leakage. The values of remnant polarization are almost the same, about 42μC∕cm2, for (110)- and (111)-oriented BFO films. However, polarization measured under varying pulse widths demonstrates that the switching polarization in (111)-oriented BFO films is higher than in (110)-oriented films. Additionally, (111)-oriented BFO films exhibit better retention properties than (110)-oriented films.

Characterization of highly (110)- and (111)-oriented Pb(Zr,Ti)O3 films on BaPbO3 electrode using Ru conducting barrier

Highly non-(001)-oriented Pb(Zr,Ti)O3 (PZT) films have been fabricated by rf-magnetron sputtering. The preferential (110)-oriented BaPbO3 (BPO) deposited on Ru buffer layer induces the growth of (110)-oriented PZT film. With the aid of self-organized growth of PZT, the orientation of the film deposited on random-oriented BPO∕Pt(111)∕Ru(002) is (111)-preferred. The insertion of Pt layer between BPO and Ru changes the orientation of PZT from (110) to (111) and prevents the oxygen diffusion. These non-(001)-oriented PZT films possess more superior ferroelectric, fatigue, and retention properties than those of (001)-oriented PZT films.

Enhanced Dielectric Properties of [Pb(Mg1/3Nb2/3)O3]0.9–PbTiO3]0.1 Thin Films Grown on BaPbO3 Perovskite Electrode

Polycrystalline and epitaxial [Pb(Mg1/3Nb2/3)O3]0.9–[PbTiO3]0.1 (PMN–PT) thin films were prepared by pulsed laser deposition on BaPbO3 (BPO) and La0.7Sr0.3MnO3 (LSMO) oxide electrodes. In comparison, the epitaxial films show higher dielectric constant and the polycrystalline films exhibit lower dielectric loss and smaller leakage current. It is also found that the use of lead based BPO electrodes helps to raise the dielectric constant of the PMN–PT layer by 30%, and to reduce the dielectric leakage by as much as three orders of magnitude. Our results have clearly demonstrated the superiority of using lead based electrodes for growing lead based dielectrics.

Sol-Gel Derived Pb(Zr0.53Ti0.47)O3 Thin Films on BaPbO3 Electrode

PbZr0.53Ti0.47 (PZT)/BaPbO3(BPO) heterostructure was fabricated by combining the sol-gel and RF-magnetron sputtering techniques. The BPO bottom electrode can effectively prevent the formation of the rosette structure of PZT and reduce the crystallization temperature to 550°C which is 100°C lower than that needed in PZT/Pt film. The BPO bottom electrode not only improves the fatigue property but also reduces the leakage current density. Thus, the BPO electrode can be a good candidate for use in PZT ferroelectric capacitor.

Preparation of BaPbO3 Electrode Thin Films by RF Magnetron Sputtering

For electrode materials of Pb(Zr,Ti)O3 (PZT) thin films in ferroelectric random access memory (FeRAM), various materials have been studied. As new electrode material with which the polarization and fatigue properties are improved, we take notice of barium metaplumbate BaPbO3 (BPO). Because the BPO contained lead (Pb) and oxygen is conductor that adopted same perovskite structure as PZT. BPO thin films were prepared by rf magnetron sputtering on various substrates. (SiO2/Si, MgO, Al2O3 and Pt-coated substrates), and influence of growth conditions (sputtering gas, rf power, the substrate-heating temperature and post anneals) on crystallization and conductivity were investigated. In case of post anneal after sputtering at room temperature, perovskite single phase was obtained above 400°C. In case of substrate heating while sputtering, without post anneal, perovskite single phase was obtained at 350–500°C on SiO2/Si substrates (110) preferred orientation BPO films obtained at low temperature, and resistivity of the films decreased at decreasing sputtering temperature. Resistivity of the film at substrate temperature 350°C was 3 × 10−3 Ω cm. In the case of single crystal substrate, the BPO films were epitaxially grown. Orientation of the films was varied with the sputtering condition. The epitaxial PZT thin films were also grown on the BPO, revealing that PZT(111)[011] //BPO(111)[011] //Pt(100)[011] //MgO(100)[011] and PZT(111)[011] //BPO(111)[011] //Pt(111)[011] //Al2O3(001)[100] structures were obtained, and their ferroelectric properties were also evaluated.

RF-Magnetron Sputtered Conductive Perovskite BaPbO3 Films

The crystallinity, chemical bonding, and electrical properties of BaPbO3 (BPO) thin films prepared by rf-magnetron sputtering on SiO2/Si substrates were investigated. The working pressure and the Ar/O2 ratio during sputtering are two of the most important factors that influence the characteristics of the prepared BPO films. Both increasing working pressure and increasing Ar/O2 ratio enhanced the crystallization of the perovskite BPO phase and yielded films with low resistivity. Sputtering in an environment with a working pressure of 80 mTorr and Ar/O2 = 90/10 at 350°C gave deposited BPO films with a low resistivity of 0.9 ×10-3 Ωcm, and a high carrier concentration of 8.3 ×1020 electrons/cm3, which values were almost equal to those of the bulk BaPbO3. X-ray photoelectron spectroscopy (XPS) revealed that Pb4+ ions were formed in the BPO films as the working pressure and the Ar/O2 ratio were increased, enhancing the crystallization of the perovskite BPO phase to yield films of lower resistivity.

BaPbO 3 perovskite electrode for lead zirconate titanate ferroelectric thin films

BaPbO 3 (BPO) films were prepared by rf-magnetron sputtering at temperatures as low as 350 °C. These films possessed low electrical resistivity of 1.4×10−3 Ω cm, which is appropriate for electrodes. The BPO electrode has an advantage over a Pt electrode in that it lowers the crystallization temperature of Pb(Zr0.53Ti0.47)O3 (PZT) films from 600 to 550 °C. The coercive fields of the PZT films deposited on a BPO/Pt electrode are significantly lower than those deposited on the Pt electrode, but the remanent polarization remained essentially unchanged. The BPO electrode also improved the fatigue resistance and decreased the leakage current of the PZT films deposited.

Modeling Phase Stability in a(B1/3B'2/3)O3 Perovskites

AbstractOrder-disorder phenomena on the simple-cubic B-site sublattice in A(B1/3B'2/3)O3 perovskites is examined. A simple cubic groundstate analysis in the cube approximation reveals that this approximation is inadequate for A(B1/3B'2/3)O3 perovskites, because it cannot predict a common experimentally-observed [111] superstructure. A partial vertex enumeration technique is used to demonstrate that a 12 interaction subset of the cube + linear triplet approximation is sufficient. First-principles calculations were performed for Ba(Zn1/3Ta2/3)O3 (BZT) and Pb(Mg1/3Nb2/3)O3 (PMN), two technologically interesting materials, in an effort to construct generalized Ising model Hamiltonians to enable simulations of these materials. Both ionic model (SSCAD) and pseudopotential (PP) calculations were done, enumerating the relative energies of a series of B-site superstructures. Structural hierarchies are reasonble and predict the [111] groundstate for both BZT and PMN, despite the fact that it is not observed in the latter. The pseudopotential results also indicate the possibility of metal-insulator transitions in BZT as a function of B-site configuration.

Interpretation of the electronic structure of Ba(K)Pb(Bi)O3 via the alternating lattice method

An analysis of augmented plane wave results obtained for the cubic perovskite compounds BaBiO3, KBiO3, and BaPbO3 of coherent potential approximation results for the alloys Ba1-xKxBiO3 and BaPb1-yBiyO3 is made by the alternating lattice method. We show that the electronic structure near the Fermi level of the pure compounds and their alloys can be well understood by the alternating nature of the Bi(or Pb)-O sublattices in a tight-binding scheme involving a small set of orbitals.

Electron-phonon interaction in the Ba(K)Pb(Bi)O3 system

We have used the results of band structure calculations to evaluate the electron-phonon coupling and the superconducting transition temperature in the cubic perovskites Ba(K)Pb(Bi)O3.

Piezoelectric Properties of Solid Solution Ceramics - A Note

Piezoelectric coupling coefficient for compositions in the quaternary system (BaPb) (NbZr)O3 using Mason’s technique are reported. It is found that the radial coupling coefficient is maximum for compositions at the morphotrophic boundaries in both tetragonal and orthorhombic phases of the system.