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Electrochemical phenomena in ferroelectrics are of particular interest for catalysis and sensing applications, with recent studies highlighting the combined role of the ferroelectric polarisation, applied surface voltage and overall switching history. Here, we present a systematic Kelvin probe microscopy study of the effect of relative humidity and polarisation switching history on the surface charge dissipation in ferroelectric Pb(Zr0.2Ti0.8)O3 thin films. We analyse the interaction of surface charges with ferroelectric domains through the framework of physically constrained unsupervised machine learning matrix factorisation, Dictionary Learning, and reveal a complex interplay of voltage-mediated physical processes underlying the observed signal decays. Additional insight into the observed behaviours is given by a Fitzhugh–Nagumo reaction–diffusion model, highlighting the lateral spread and charge passivation process contributors within the Dictionary Learning analysis., The authors acknowledge Dr Sergei V. Kalinin of Oak Ridge National Laboratory, for helpful discussions about machine learning and the initial suggestion to explore reaction–diffusion modelling. This work was supported by Division II of the Swiss National Science Foundation under project 200021_178782. A.V. acknowledges support by the Spanish Government under the project PID2019-110907GB-I00 and the “Severo Ochoa” Program for Centres of Excellence in R&D (CEX2019-000917-S). N.D. acknowledges support by the Spanish Government under the project PID2019- 109931GB-I00. N.B.G. acknowledges support by the National Science Foundation under the project DMR-20269676. The authors would like to thank S. Muller for technical support., With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).

Lead zirconate titanate samples are used for their piezoelectric and ferroelectric properties in various types of micro-devices. Epitaxial layers of tetragonal perovskites have a tendency to relax by forming [Formula: see text] ferroelastic domains. The accommodation of the a/c/a/c polydomain structure on a flat substrate leads to nanoscale deformation gradients which locally influence the polarization by flexoelectric effect. Here, we investigated the deformation fields in epitaxial layers of Pb(Zr0.2Ti0.8)O3 grown on SrTiO3 substrates using transmission electron microscopy (TEM). We found that the deformation gradients depend on the domain walls inclination ([Formula: see text] or [Formula: see text] to the substrate interface) of the successive [Formula: see text] domains and we describe three different a/c/a domain configurations: one configuration with parallel a-domains and two configurations with perpendicular a-domains (V-shaped and hat-[Formula: see text]-shaped). In the parallel configuration, the c-domains contain horizontal and vertical gradients of out-of-plane deformation. In the V-shaped and hat-[Formula: see text]-shaped configurations, the c-domains exhibit a bending deformation field with vertical gradients of in-plane deformation. Each of these configurations is expected to have a different influence on the polarization and so the local properties of the film. The deformation gradients were measured using dark-field electron holography, a TEM technique, which offers a good sensitivity (0.1%) and a large field-of-view (hundreds of nanometers). The measurements are compared with finite element simulations.

Detection of dynamic surface displacements associated with local changes in material strain provides access to a number of phenomena and material properties. Contact resonance-enhanced methods of Atomic Force Microscopy (AFM) have been shown capable of detecting ~1-3 pm-level surface displacements, an approach used in techniques such as piezoresponse force microscopy, atomic force acoustic microscopy, and ultrasonic force microscopy. Here, based on an analytical model of AFM cantilever vibrations, we demonstrate a guideline to quantify surface displacements with a high accuracy by taking into account the cantilever shape at the first resonant contact mode depending on the tip-sample contact stiffness. The approach has been experimentally verified and further developed for the piezoresponse force microscopy (PFM) using well-defined ferroelectric materials. These results open up a way to accurate and precise measurements of the surface displacement as well as piezoelectric constants at the pm-scale with nanometer spatial resolution and will allow avoiding erroneous data interpretations and measurement artefacts. This analysis is directly applicable to all cantilever-resonance-based SPM techniques., 21 page, 6 figures + Supplementary data (2 tables, 4 figures)

Scanning electrooptic microscopy provides optical imaging of surface ferroelectric polarization patterns by measuring modulation of the output optical signal induced by a sinusoidal electric field. Ferroelectric single crystals and inhomogeneous phase transitions in ferroelectric thin films were investigated by this technique. Here we report investigation of the domain structure in relaxor materials. We have observed formation and evolution of microscopic domains under the action of a dc bias electric field. Furthermore, the local electrooptic switching loops have been measured with sub-micron resolution. Features of electrooptic imaging in ceramic samples are also discussed.

Electroceramics research is driven by technology and device applications. This growing field includes a vast number of magnetic, dielectric, ionically conducting, semiconducting, and superconducting ceramics used in domains as diverse as transportation, industrial production, power engineering, medicine and health care, consumer electronics, and communication. Al the turn of the decade, three major trends are gaining importance: Materials integration issues play an increasingly important role driven by the interest in integrating electroceramic functions into conventional semiconductor chips as well as by the evolution of multifunctional components and systems. The industrial production process currently is in a transition from empirical studies and physical demonstrators into virtual design and testing. To fit into this evolution, for integrated as well as for discrete electroceramic components, a rise in modeling and numerical simulation of material- and device-related properties presently occurs. Electroceramic materials are following in the footsteps of conventional semiconductors with respect to further miniaturization, and are experiencing the same evolution:from microtechnology towards nanotechnology. Nanosize effects and nanotechnology issues are therefore gaining importance. In the context of these three issues, we discuss the research in electroceramics during the last decade and basic trends for the future. (C) 2000 Published by Elsevier Science Ltd on behalf of Acta Metallurgica Inc. All rights reserved.

Fatigued state of the Pt-PZT-Pt system is studied by means of low-temperature conduction measurements. It is shown that the conduction in the temperature interval of 100-140 degrees K is determined by the cold field emission of electrons (tunneling conduction mechanism). The Fowler-Nordheim equation describes well the observed current-voltage relations for reasonable values of the system parameters. The conduction measurements in this regime show that the strong fatigue of the switching polarization provokes a substantial increase of the cold-field-emission-controlled current. The decrease of the switching polarization from 60 to 15 mu C/cm(2) due to fatigue results in a shift of the I-V characteristic towards the lower fields by some 500 kV/cm. Partial. rejuvenation of the sample by short-time beating to 490 degrees K results in a complete restoring of the initial current-voltage characteristic. It is shown that the fatigue-induced increase of the conduction can be modeled by the charging of the interfacial layers of thickness comparable with the tunneling length. This interpretation is consistent with the fatigue scenario related to the space charge-assisted blocking of the centers of the domain nucleation suggested earlier.

We report on the thickness dependence of the ferroelastic domains of PbTiO3 films grown on (110)-DyScO3 with low thicknesses (up to 240 nm), which fall outside the validity range of the square root law proposed by Roytburd. For slow-grown films, the data reveal the linear thickness dependence predicted by Pertsev and Zembilgotov, using a complete elastic description, while a 2/3 scaling exponent is found for fast-grown films. Extremely long domains running all through the samples have been observed in the latter case, compared to the short domains observed in slow-grown films. These differences are ascribed to the in-plane anisotropy for domain wall nucleation, which is likely caused by the anisotropic elastic modulus of the substrate. © 2013 AIP Publishing LLC., This work was supported by NanoNextNL, a micro and nanotechnology consortium of the Government of the Netherlands and 130 partners.

Strong coupling among external voltage, electrochemical potentials, concentrations of electronic and ionic species, and strains is a ubiquitous feature of solid state mixed ionic-electronic conductors (MIECs), the materials of choice in devices ranging from electroresistive and memristive elements to ion batteries and fuel cells. Here, we analyze in detail the electromechanical coupling mechanisms and derive generalized bias-concentration-strain equations for MIECs including effects of concentration-driven chemical expansion, deformation potential, and flexoelectric effect contributions. This analysis is extended towards the bias-induced strains in the uniform and scanning probe microscopy-like geometries. Notably, the contribution of the electron-phonon and flexoelectric coupling to the local surface displacement of the mixed ionic-electronic conductor caused by the electric field scanning probe microscope tip has not been considered previously. The developed thermodynamic approach allows evolving theoretical description of mechanical phenomena induced by the electric fields (electro-mechanical response) in solid state ionics towards analytical theory and phase-field modeling of the MIECs in different geometries and under varying electrical, chemical, and mechanical boundary conditions., 28 pages, 3 figures,1 table, 1 appendix

In epitaxial ferroelectric thin films under tensile strain, a transition from 180 degrees domains to 90 degrees domains can be achieved by increasing the film thickness. In many cases, the 90 degrees a/c domains appear in the form of wide c-domains separated by narrow a-stripes. We have deposited thin films of PbTiO(3) on DyScO(3) substrates and show that the condition of horizontal coherence forces the a-domains to adopt discrete sizes, the smallest of which is substrate-independent and depends only on the tetragonality of the ferroelectric film. Growing PbTiO(3) on DyScO(3), we have achieved the narrowest (6 nm) possible a-domains, as well as the shortest periodicity that allows to maintain the lateral coherence in the film.

In epitaxial ferroelectric thin films under tensile strain, a transition from 180 degrees domains to 90 degrees domains can be achieved by increasing the film thickness. In many cases, the 90 degrees a/c domains appear in the form of wide c-domains separated by narrow a-stripes. We have deposited thin films of PbTiO(3) on DyScO(3) substrates and show that the condition of horizontal coherence forces the a-domains to adopt discrete sizes, the smallest of which is substrate-independent and depends only on the tetragonality of the ferroelectric film. Growing PbTiO(3) on DyScO(3), we have achieved the narrowest (6 nm) possible a-domains, as well as the shortest periodicity that allows to maintain the lateral coherence in the film.

Compositionally graded Ba(1 − x)Sr x TiO3 thick films were fabricated using the airflow deposition technique. Bulk samples were fabricated from the same precursor powders for comparison purposes. Characterization revealed close similarity between thick films and bulk samples field behaviour. A simple model was proposed to allow estimating the electric field distribution in the vicinity of the Curie point based on the experimental data obtained for bulk samples.

Thin films of PbTiO3, a classical ferroelectric, have been grown under tensile strain on single-crystal substrates of DyScO3. The films, of only 5nm thickness, grow fully coherent with the substrate and show no crystallographic twin domains, as evidenced by synchrotron x-ray diffraction. A mapping of the reciprocal space reveals intensity modulations (satellites) due to regularly-spaced polar domains in which the polarization appears rotated away from the substrate normal, characterizing a low symmetry phase not observed in the bulk material. This could have important practical implications since these phases are known to be responsible for ultrahigh piezoelectric responses in complex systems., Nature of changes: Slightly modified abstract, introduction and conclusion paragraphs to make it more accessible to the general reader. Corrected a typo in the value of the domain period. These changes do not affect the content and results. To be published in PRL

In epitaxial ferroelectric thin films under tensile strain, a transition from 180 degrees domains to 90 degrees domains can be achieved by increasing the film thickness. In many cases, the 90 degrees a/c domains appear in the form of wide c-domains separated by narrow a-stripes. We have deposited thin films of PbTiO(3) on DyScO(3) substrates and show that the condition of horizontal coherence forces the a-domains to adopt discrete sizes, the smallest of which is substrate-independent and depends only on the tetragonality of the ferroelectric film. Growing PbTiO(3) on DyScO(3), we have achieved the narrowest (6 nm) possible a-domains, as well as the shortest periodicity that allows to maintain the lateral coherence in the film.

In this paper, we introduce a charge integrator as a read-out system for piezoelectric cantilever sensors. The charge integrator is used to monitor the surface charge induced by piezoelectric materials as a function of mechanical stress. This technique improves the response of piezoelectric cantilever sensors in low-frequency measurements, which makes them suitable for chemical and biological detection. Furthermore, it is capable of real-time, portable and all-electrical detection. The detection of alkanethiols on the Au-coated piezoelectric cantilevers is demonstrated to verify the concept.

Residual stresses develop in the sol-gel-derived ferroelectric thin films during the transformation of the metalorganic gel to the metal oxide upon thermal treatment and due to the thermal and elastic mismatch between the Pb(Zrx,Ti1-x)O3 (PZT) film and the substrate materials during cooling. In this study, residual stresses were determined using the wafer curvature method after the deposition of multilayer PZT film on platinized (100) silicon wafers. A multilayer model for stress analysis was used to calculate the residual stress in PZT films of three different compositions, x=0.4, x=0.52 and x=0.6. Orientation dependent residual stresses were found in compositions containing the tetragonal phase, with x=0.4 and x=0.52. Depending on the fraction of (100) orientated domains low compressive or low tensile stress was found in Pb(Zr0.4Ti0.6)O3 (PZT 40/60). Higher residual stress was found in PZT films consisting of only rhombohedral crystallographic structure (PZT 60/40) while the residual stress in PZT films with morphotropic boundary composition (PZT 52/48) was significantly dependent on the film orientation and the phase composition and could range from 17 MPa to 90 MPa. The effect of the film orientation on residual stress was found to be a function of the anisotropic thermal expansion coefficient of PZT. The contribution of the thermal and elastic properties of materials to the total wafer curvature was investigated and discussed. Finally, the residual stress results calculated with the four layers model were compared to the results calculated using the Stoney equation.

This paper reports on the microfabrication and characterization of piezoelectric MEMS structures based on epitaxial Pb(Zr0.2Ti0.8)O-3 (PZT) thin films grown on silicon wafers. Membranes and cantilevers are realized using a sequence of microfabrication processes optimized for epitaxial oxide layers. Different issues related to the choice of materials and to the influence of the fabrication processes on the properties of the piezoelectric films are addressed. These epitaxial PZT transducers can generate relatively large deflections at low bias voltages in the static mode. Estimations of the piezoelectric coefficient d(31) of the epitaxial PZT thin film (100 nm) yield 130 pm V-1. In the dynamic mode, the performance of the epitaxial PZT transducers in terms of the resonant frequency, modal shape and quality factor are examined. An epitaxial PZT/Si cantilever (1000 x 2500 x 40 mu m(3)) resonating in air and in vacuum exhibits a deflection of several microns with quality factors of 169 and 284, respectively. For a 1500 mu m diameter membrane, the quality factor is 50 at atmospheric pressure, and this rises to 323 at a pressure of 0.1 mbar. These results indicate the high potential of epitaxial piezoelectric MEMS, which can impact a variety of technological applications.

The effect of 1 MeV ion implantation on leakage conduction, dielectric and ferroelectric properties of the Pt/Pb(ZrxTi1-x)(2)O-3/Pt capacitors is studied for a wide range of implantation doses (10(10)-10(16) cm(-2)). It is shown that the implantation of Pt+, with an implant and vacancy profile peaking at the bottom interface and a dose within the range of 10(13)-10(16) cm(-2), provokes a strong suppression of the leakage conduction and ferroelectric hysteresis. In addition, ion implantation results in a decrease of the static dielectric constant. Annealing of the specimens at 650 degrees C restores the initial conduction and dielectric properties. The phenomena observed can be interpreted in terms of formation of a non-switching dielectric layer at the interface of the ferroelectric film. For doses ranging from 10(13) to 10(14) cm(-2) the specimen shows the behavior of a linear capacitor with dielectric constant of 120-270 and low level of leakage currents (about 10(-9) A/cm(2) at de electric field of 150 kV/cm). The results obtained indicate that ion bombardment of the ferroelectric film surface can be of practical interest for creation of high dielectric constant hysteresis-free low-leakage capacitor materials.

Research and development in the field of electroceramics is driven by technology and device applications. It includes research on a broad spectrum of inorganic materials, and it covers all scales from the level of the crystalline lattice to that of final devices. The applications find a place in an increasing number of domains, ranging from environment monitoring and transportation, through medicine and health-care, to electronics and communications. Two tendencies are emerging: surface and interface phenomena play an increasingly important role, motivated by the interest to integrate electroceramic functions into microelectronics and MEMS technologies as well as by the evolution of bulk products from discrete components into materials systems. Electroceramics are following conventional semiconductors with respect to down-scaling. Nano-size effects, nanotechnology related processes, and the use of new characterization techniques to reveal nanometric scale features are therefore gaining in importance. Recent research in electroceramics and evolving trends for the future are discussed in the context of these two issues. (C) 2001 Elsevier Science Ltd. All rights reserved.

The structural property and electric field response of a single perovskite PbTiO3 nanowire were investigated by means of synchrotron X-ray diffraction (XRD) with a micro X-ray beam. XRD 0-20 patterns and Raman spectra confirmed the formation of the perovskite phase of PbTiO3 by annealing the PX-phase of Pb-Ti-O nanowires at 600 degrees C. In addition, the obtained nanowires showed multi-domain/grain features. By focusing the micro X-ray beam on a single perovskite PbTiO3 nanowire, both ends of which are connected to electrodes, the lattice distortion under the electric field was observed. (C) 2010 The Japan Society of Applied Physics

The dielectric response of a ferroelectric film with bilinear coupling between order parameter and strain is theoretically addressed. An exact solution for the total (lattice and domain contributions) dielectric permittivity of the system for the case where the domain spacing is much smaller than of film thickness is reported. An unusual temperature dependence of the permittivity in the polydomain state is found: it stays constant below the phase transition. The treated problem has been found to be a remarkable case where the choice of the order parameter between two linearly coupled variables is crucial.

Thin films of neodymium-modified bismuth titanate Bi3.44Nd0.56Ti3O12 (BNT) were grown on Pt/TiO2/SiO2/Si substrates using chemical solution deposition method. The capacitors made by applying top Au electrodes on BNT films showed significantly improved values of the remanent polarization as compared to that using bismuth titanate Bi4Ti3O12 (BT) films. The 2P(r) value for the BNT capacitors was determined to be equal to 38 muC/cm(2) at an applied voltage of 24 V, whereas, for Bi4Ti3O12 ( BT) capacitors a value of 20 muC/cm(2) was measured at the same applied voltage. The maximum piezoelectric and pyroelectric coefficients of 22 pm/V and 112 muC/m(2) K respectively, were measured for the BNT thin films.

The manner in which 90. ferroelectric-ferroelastic domains respond to changes in temperature has been mapped in BaTiO3 single crystals using atomic force microscopy. Domain periodicity remains unaltered until approximately 2 degrees C below the Curie temperature (T-C), whereupon domains coarsened dramatically. This behavior was successfully rationalized by considering the temperature dependence of the parameters associated with standard models of ferroelastic domain formation. However, while successful in describing the expected radical increase in equilibrium period with temperature, the model did not predict the unusual mechanism by which domain coarsening occurred; this was not continuous at a local level but instead involved discrete domain annihilation events. Subsequent insights from a combination of free energy analysis for the system and further experimental data from an analogous situation, in which domain period increases with increasing crystal thickness, suggested that domain annihilation is inevitablewhenever a component of the relevant gradient that affects domain period is orientated parallel to the domain walls. Consistent with this thesis, we note that, for the observations presented herein, the thermal gradient possessed a significant component parallel to the domain walls. We suggest that domain annihilation is a general feature of domain structures in gradient fields.

Fatigue phenomena occurring in Pb(ZrxTi1-x)O-3 ferroelectric thin-film capacitors (FECAP) with Pt electrodes are studied by means of conduction measurements in the cold-field-emission (tunneling) regime. We have determined that conduction in virgin FECAPs is controlled by tunneling at temperatures 100-140 K and electric fields (2.3-3.0 MV/cm). The Fowler-Nordheim equation successfully describes observed current-voltage relations for reasonable values of the semiconductor parameters of the system. Fatigue of the switching polarization induced by bipolar voltage cycling provokes a substantial increase in tunneling conduction, shifting the I-V curve to lower fields by some 0.5 MV/cm. The partial restoration of the switching polarization produced by heating of the sample up to 490 K results in a complete restoration of the initial current-voltage characteristic. It is shown that the fatigue-induced increase in conduction can be modeled by the charging of an interfacial layer of a thickness comparable with the tunneling length. This interpretation is consistent with a fatigue scenario related to the space-charge-assisted blocking of near-by-electrode centers of domain nucleation. (C) 1998 American Institute of Physics. [S0003-6951(98)03536-0].