Large ferroelectric polarization of chemical solution processed BiFeO3–PbTiO3 thin films (original) (raw)
Related papers
2010
Thin films of (1-x)BiFeO3-xPbTiO3 (BF-xPT) with x ~ 0.60 were fabricated on Pt/Si substrates by chemical solution deposition of precursor BF and PT layers alternately in three different multilayer configurations. These multilayer deposited precursor films upon annealing at 700{\deg}C in nitrogen show pure perovskite phase formation. In contrast to the equilibrium tetragonal structure for the overall molar composition of BF:PT::40:60, we find monoclinic structured BF-xPT phase of MA type. Piezo-force microscopy confirmed ferroelectric switching in the films and revealed different normal and lateral domain distributions in the samples. Room temperature electrical measurements show good quality ferroelectric hysteresis loops with remanent polarization, Pr, of up to 18 {\mu}C/cm2 and leakage currents as low as 10-7 A/cm2.
Journal of Applied Physics, 2009
Thin films of (1-x)BiFeO 3 -xPbTiO 3 (BF-xPT) with x ≈ 0.60 were fabricated on Pt/Si substrates 11 by chemical solution deposition of precursor BF and PT layers alternately in three different 12 multilayer configurations. These multilayer deposited precursor films upon annealing at 700°C in 13 nitrogen show pure perovskite phase formation. In contrast to the equilibrium tetragonal structure 14 for the overall molar composition of BF:PT::40:60, we find monoclinic structured BF-xPT phase 15 of M A type. Piezo-force microscopy confirmed ferroelectric switching in the films and revealed 16 different normal and lateral domain distributions in the samples. Room temperature electrical 17 measurements show good quality ferroelectric hysteresis loops with remanent polarization, P r , of 18 up to 18 µC/cm 2 and leakage currents as low as 10 -7 A/cm 2 .
Applied Physics A, 2011
We report an unusual behavior observed in (BiFeO 3 ) 1 − x -(PbTiO 3 ) x (BF-xPT) thin films prepared using a multilayer chemical solution deposition method. Films of different compositions were grown by depositing several bilayers of BF and PT precursors of varying BF and PT layer thicknesses followed by heat treatment in air. X-ray diffraction showed that samples of all compositions show mixing of two compounds resulting in a single-phase mixture, also confirmed by transmission electron microscopy. In contrast to bulk compositions, samples show a monoclinic (M A -type) structure suggesting disappearance of the morphotropic phase boundary (MPB) at x = 0.30 as observed in the bulk. This is accompanied by the lack of any enhancement of the remanent polarization at the MPB, as shown by the ferroelectric measurements. Magnetic measurements showed an increase in the magnetization of the samples with increasing BF content. Significant magnetization in the samples indicates melting of spin spirals in the BF-xPT films, arising from a random distribution of iron atoms. Absence of Fe 2+ ions was corroborated by X-ray photoelectron spectroscopy measurements. The results illustrate that thin film processing methodology significantly changes the structural evolution, in contrast to predictions from the equilibrium phase diagram, besides modifying the functional characteristics of the BP-xPT system dramatically.
Journal of Applied Physics, 2007
BiFeO 3 (BFO) thin films were fabricated on Pt(111)∕Ti∕SiO2∕Si substrates by using a polymeric precursor solution under appropriate crystallization conditions. The capacitance dependence on voltage is strongly nonlinear, confirming the ferroelectric properties of the films resulting from the domain switching. The leakage current density increases with annealing temperature. The polarization electric field curves could be obtained in BFO films annealed at 500 °C, free of secondary phases. X-ray photoelectron spectroscopy spectra of films annealed at 500 °C indicated that the oxidation state of Fe was purely 3+, demonstrating that our films possess stable chemical configurations.
Chemical Substitution‐Induced Ferroelectric Polarization Rotation in BiFeO3
Advanced Materials, 2011
The direction of the ferroelectric polarization vector is a key factor infl uencing the properties of ferroelectric/piezoelectric [ 1 ] and multiferroic [ 2 ] materials. For instance, ferroelectric materials at morphotropic phase boundaries (MPB), where multiple structural phases with ferroelectric polarizations pointing in different crystallographic directions coexist, often display large piezoelectric coeffi cients. [ 3-5 ] It is the ferroelectric distortions, which accompany the polarization rotation that leads to enhancements in the piezoelectric coeffi cient. In multiferroic BiFeO 3 (BFO), it has been shown [ 2 ] that the coupled antiferromagnetic order can be altered by switching the ferroelectric polarization vector. In fact, the ability of a material to display polarization rotation is recognized as an important precursor to occurrence of an MPB. [ 5 , 6 ] Chemical substitution into perovskite BiFeO 3 , which displays room-temperature multiferroic properties, [ 2 , 7 ] has been a subject of much interest since the substitution results in improved ferroelectric properties and enhancement in piezoelectric and dielectric properties. [ 8-10 ] One important consequence of substitution is that a symmetry-lowering structural phase transition from the rhombohedral phase for pure BFO to another structure takes place, displaying the characteristics of an MPB with enhanced dielectric and piezoelectric properties, as observed in Pb-based ferroelectrics. [ 3 , 4 ] Recently, we demonstrated [ 11 ] that substitution of rare earth elements (RE = Sm, Gd, and Dy) into the A-sites of BFO thin fi lms results in a ferroelectric rhombohedral to paraelectric orthorhombic structural transition, exhibiting a double hysteresis behavior in the polarization-electric fi eld (PE) hysteresis loop, and that the occurrence of this transition can be universally described by the averaged A-site cation radius regardless of the substituted rare-earth element. The piezoelectric coeffi cient d 33 and dielectric constant ε 33 are enhanced at the boundary, and the maximum d 33 reaches 110 pm V − 1 , [ 8 ] which is comparable to the value for epitaxial Pb(Zr 0.48 Ti 0.52)O 3 thin fi lms at the MPB. [ 12 ] Based on the results of fi rst-principles calculations, it was proposed [ 11 ] that an electric fi eld-induced structural transformation from the nonpolar orthorhombic to the polar rhombohedral phase is the origin for the double hysteresis behavior and the concomitant enhanced properties at the boundary.
Electronic excitation induced modifications in the ferroelectric polarization of BiFeO3 thin films
We report the effect of electronic excitations induced modifications in the ferroelectric polarization in BiFeO 3 (BFO) multiferroic films grown on 0.2% Nb doped SrTiO 3 (SNTO) substrates by pulsed laser deposition. The BFO/SNTO films were irradiated with 200 MeV Ag +15 ions with ion fluences of 5 × 10 10 to 5 × 10 12 ions/cm 2 and characterized by using X-ray diffraction (XRD), atomic force microscopy (AFM), ferroelectric polarization and near-edge X-ray absorption fine structure (NEXAFS) measurements. The XRD and AFM results show the creation of structural defects and oxygen vacancies by ion irradiation. Such defects induced enhancement in structural strain and reduction in mobility of charge carriers leading to the improvement in ferroelectric behaviour in BFO films. In addition, the local electronic structures investigated using NEXAFS studies reveal the significant change in spectral features suggesting the role of Bi-O and Fe-O hybridizations that modifies the ferroelectric behaviour of BFO films. These results are used to understand the mechanism.
Research Square (Research Square), 2021
0.9Bi 1 − x Nd x FeO 3-0.1PbTiO 3 solid solution where x = 0.05, 0.10, 0.15 and 0.20 were success fully synthesized by the standard solid-state reaction method. The effect of Nd 3+ ion substitution on structural, micro structural, ferroelectric, magnetic, dielectric and magneto-electric properties of 0.9BiFeO 3-0.1PbTiO 3 have been investigated. The XRD analysis for the samples under study revealed distorted rhombohedral structure with R3C space group. 0.9Bi 1 − x Nd x FeO 3-0.1PbTiO 3 where x = 0.05, 0.10, 0.15 and 0.20 i.e. (BNFPT)x compounds crystallised as single-phase materials with the same structure as the parent BiFeO3 compound.. The SEM study revealed the uniform grain scattering for all prepared samples. Raman spectroscopy showed disappearance of some Raman modes indicated a structural phase transition with substitution of Nd dopants at Bi site and also con rmed the distorted rhombohedral perovskite structure of (BNFPT) x compounds with R3c symmetry. Dielectric measurements showed magnetoelectric coupling around Neel temperature in all the samples and also improved dielectric properties with addition of dopants in BiFeO 3 (BFO) compound. All the prepared samples exhibit weak ferro-magnetic character at room temperature. However, the variation in linear behavior and enhancement in magnetization is found at 5 K which shows gradual increase in remnant magnetization from 0.00785 emu/g to 0.37513 emu/g with increase in Nd doping for all (BNFPT) x samples. Nd doping reduces leakage current by three orders of magnitude, from 10 − 4 to 10 − 7. Ferroelectric study revealed the pinning effect in hysteresis loops with low remnant polarization.
Improved ferroelectric behavior in (110) oriented BiFeO[sub 3] thin films
Journal of Applied Physics, 2010
Multiferroic BiFeO 3 thin films were grown on LaNiO 3 -buffered Pt/ TiO 2 / SiO 2 / Si substrates by off-axis radio frequency magnetic sputtering, where ͑110͒ oriented texture was obtained. The LaNiO 3 buffer layer promoted the growth of BiFeO 3 film, resulting in a dense texture and columnar growth of BiFeO 3 thin films. The BiFeO 3 thin film exhibits 2P r ϳ 145.8 C / cm 2 and 2E c ϳ 573.5 kV/ cm, together with a very low dielectric loss ͑0.80% at 10 kHz͒ and an almost fatigue-free behavior at 500 kHz up to 10 10 switching cycles. The 2P r value is comparable to the reported value of the BiFeO 3 deposited on the SrTiO 3 ͑110͒ substrate. While a weak ferromagnetism is demonstrated for the multiferroic thin film at room temperature, the low leakage current and high ͑110͒ orientation contribute toward the improved ferroelectric behavior. The BFO thin film with a giant remanent polarization and a fatigue-free behavior promises a candidate material for high-temperature ferroelectric random access memory.
Journal of Physics D: Applied Physics, 2008
Multiferroic BiFeO 3 films have been grown on LaNiO 3−x /SrTiO 3 and Pt/Si substrates by RF magnetron sputtering. The films showed fully saturated ferroelectric hysteresis loops with large remanent polarization of 64 µC cm −2 , suitable for most device applications. Piezoresponse force microscopy confirmed that the films were electrically writable. In addition to the high-frequency intrinsic dielectric loss of epitaxial films, the Argand diagram also revealed low-frequency contributions from both dc conductivity and interfacial polarization at electrodes. For polycrystalline films on Pt/Si, the dominant contribution to dielectric loss was space charge polarization at grain boundaries.