Improvement of the ferroelectric properties of ABO3 (A=Pb, Ca, Ba; B=Ti, Zr) films (original) (raw)
Related papers
Applied Physics Letters, 2000
We report structural, dielectric, and ferroelectric properties of compositionally graded (Pb,La)TiO3 thin films on LaNiO3/SiO2/Si substrates, where all the films were prepared by the sol-gel technique. The crystalline orientation and surface morphology of the graded films were closely related to the deposition sequence of film layer. Upgraded film exhibited (100) preferentially oriented growth, whereas downgraded film showed a randomly oriented growth, where the films with La content increasing or decreasing gradually along film thickness from the substrate to the top surface are called “upgraded” or “downgraded” films, respectively. The dielectric constants, for upgraded and downgraded films annealed at 650 °C for 60 min, were found to be 659 and 641, respectively. The thin films had large polarization offsets in hysteresis loops when driven by an alternating electric field. The magnitude of the offsets displayed a power law dependence on the electric field, and the direction of th...
Crystal Growth & Design
Functional oxide thin films integrated into CMOS technology often exhibit degraded properties with respect to bulk materials because of complex interfacial phenomena. In this contribution, we demonstrate that a sol-gel LaNiO3 (LNO) interlayer deposited onto the surface of a Pt/TiO2/SiO2/Si substrate prior to growth of sol-gel BiScO3-PbTiO3 (BSPT) films acts: i) to seed nucleation of perovskite structured; ii) to template growth to give controlled orientation and enhanced crystallinity and iii) as a sink for oxygen vacancies (VO). The LNO interlayer therefore not only improves the ferroelectric, piezoelectric and dielectric properties but also reduces leakage current and prevents degradation of the remanent polarization during fatigue tests. We propose that the use of a LNO interfacial layer may offer a generic solution to interfacial degradation in functional oxide films.
1998
Thin ®lms of polycrystalline, tetragonal BaTiO 3 on oxidized Ti metal substrates were synthesized at 240 C under hydrothermal conditions. Microstructure and electrical properties of the ®lms generated over a four week period of synthesis formed the focus of this study. The ®lms displayed a smooth and shiny surface with a relatively dense structure and no observable cracks. Film thickness reached 0.5 mm after two weeks of synthesis and thereafter remained constant. Diameters of the grains on the ®lm surface were in the range of 1 $ 2 mm. It is proposed that initial formation of the BaTiO 3 ®lm occurs by reaction of Ba 2 with solubilized titanium oxide on the Ti metal surface followed at later stages by an in-situ growth via reaction of TiO x with Ba 2 diffusing through the BaTiO 3 ®lm. X-ray diffraction and Raman spectroscopy indicated that the BaTiO 3 ®lms are tetragonal, and the ®lms exhibited typical ferroelectric hysteresis loops at room temperature. However, no evidence of the dielectric anomaly (Curie transition) between 30 and 200 C was observed. Dielectric constant of the ®lms at 1 kHz at room temperature was between 400±500. Both dielectric constant and tand exhibited low dispersion as a function of frequency at temperatures below 150 C, and the dispersion increased with temperature.
Applied Physics Letters, 2000
Ti-modified 0.72BiFeO 3 -0.28PbTiO 3 thin films were prepared on Pt/Ti/SiO 2 /Si substrates by pulsed laser deposition under different oxygen pressures from 2 Pa to 15 Pa. The microstructures and electrical properties were investigated. Tetragonal (001) preferential orientation was observed in all films under different oxygen atmosphere pressures. The electrical properties of the thin films have been investigated for various deposition conditions. The dielectric constant and double remanent polarization were found to be 550 and 80 µC/cm 2 , respectively, for the thin film deposited at an oxygen atmosphere of 10 Pa and a substrate temperature of 680 • C.
Dielectric properties of ferroelectric (Ba0.6Sr0.4)TiO3 thick films prepared by tape-casting
Journal of Electroceramics, 2006
Thick BST films have been fabricated by a tape casting and firing method. Dielectric constants of BST films are changed from 5700 to 7000 at 1 MHz after focused beam annealing. Furthermore, surface morphologies and depth profile of chemistry have been altered after annealing. Especially, Sr atoms diffuse out to the surface, while Ba atoms diffuse into the center. The possibility of the surface alteration of the thick films have been clearly demonstrated in this study, which may applied for the integration of ferroelectrics and other dielectrics and/or conductors for low cost microwave tunable devices.
Journal of Crystal Growth, 2005
The (1 0 0) oriented LaNiO 3 (LNO) films with different thickness were prepared on SiO 2 /Si substrate by a modified metallorganic decomposition process. PbZr 0.53 Ti 0.47 O 3 (PZT) films ($1 mm) subsequently deposited on LNO by modified sol-gel process. The X-ray diffraction measurements show PZT films exhibit a single perovskite phase with (1 0 0) preferred orientation. a 1 0 0 494% can be obtained for PZT deposited on LNO bottom electrode with thickness greater than 60 nm. SEM measurements show the PZT films have a columnar structure. The LNO thickness effect on P r , E c , and dielectric constant were investigated and showed that the thickness of the LNO bottom electrode caused drastic changes in P r , dielectric constant and dielectric loss. Sub-switching fields dependence of permittivity were investigated for PZT films and showed that both reverible and irreversible component of the permittivity increase with the thickness of LNO electrode. r
Applied Surface Science, 2013
Ferroelectric lead-free (Na 0.5 Bi 0.5) 1−x Ba x TiO 3 thin films obtained by pulsed laser deposition have been structurally and electrically investigated for compositions, x = 0 and x = 0.06, in and out of the morphotropic phase boundary (MPB). Sodium bismuth titanate Na 0.5 Bi 0.5 TiO 3 (NBT), pure or in solid solution with other materials (like BaTiO 3), is considered to be the best candidate material for lead-free ferroelectric and piezoelectric applications such as actuators and nonvolatile memory devices. Bulk solid solutions with BaTiO 3 (BT), (1−x)NBT-xBT (NBT-x%BT) have been investigated widely, also due to a morphotropic phase boundary (MPB) with enhanced dielectric and ferroelectric properties between a rhombohedral and a tetragonal ferroelectric phase, at x = 0.06. Nonetheless, to transpose bulk properties to NBT-BT thin films is a major achievement. XRD technique has been used for structural characterizations of NBT-BT films. Dielectric spectroscopy measurements were performed at room temperature in the frequency range 100 Hz-1 MHz. The best films show pure perovskite phase and good crystalline structure, as a function of specific deposition conditions. Unusual characteristics, especially dielectric constant values higher than those for bulk, have been found for films with specific crystallographic orientations.
Journal of materials …, 2000
Barium titanate (BaTiO 3 ) and other perovskite-type materials are being extensively studied for their potential commercial applications in dynamic random access memories (DRAMs), capacitors and nonvolatile memories due to their desirable dielectric properties . Many methods, such as rf-sputtering , laser-ablation , MOCVD (metalorganic chemical vapor deposition) , and sol-gel techniques, have been used to grow thin films; however, most of these methods are expensive and require complex equipment. The polymeric precursor method is a chemical technique that offers several advantages, i.e., its low cost, good compositional homogeneity, high purity, relatively low processing temperatures and the ability to coat large substrate areas. In this technique, the desired metal cations are chelated in a solution using a hydroxycarboxylic acid as the chelating agent. The solution is mixed with a polyhydroxyalcohol and heated to promote esterifying reactions in the solution, while the metals remain homogeneously distributed in the polymeric network.
Journal of Physics D-applied Physics, 2000
Thin films of ferroelectric PbTiO3 (PT) and Pb(Zr0.5 Ti0.5 )O3 (PZT) as well as antiferroelectric PbZrO3 (PZ) have been prepared on LaNiO3 /SiO2 /Si substrates by nebulized spray pyrolysis (NSP) of metal-organic precursors. The metallic LaNiO3 (LNO) electrode layer was also deposited by NSP. The ferroelectric films obtained show satisfactory morphology and desirable dielectric properties. Typical values of the coercive field, remnant polarization and dielectric constant (300 K) for the PT/LNO/SiO2 /Si film are 170 kV cm-1 , 22 µC cm-2 and 210, respectively, with the corresponding values for the PZT/LNO/SiO2 /Si film being 120 kV cm-1 , 13 µC cm-2 and 540, respectively. The PZ/LNO/SiO2 /Si film shows typical antiferroelectric characteristics including the electric-field induced reversible antiferroelectric - ferroelectric transition. The various films deposited on LNO/SiO2 /Si by NSP are comparable in all respects to those prepared on Pt/Ti/SiO2 /Si by the same technique.