Polarization Switching Process Research Articles

In‐Depth Atomic Mapping of Polarization Switching in a Ferroelectric Field‐Effect Transistor

AbstractThe ferroelectric control of a Mott transistor is a promising strategy for nonvolatile low‐power electronics. Understanding the fundamental limits of the ferroelectric‐field effect is challenging, as the relevant length scales are restricted to a few atomic planes within the interface. Here, the polarization switching process of a prototypical ferroelectric Mott transistor combining BiFeO3, a ferroelectric material with a large polarization, and (Ca,Ce)MnO3, a charge‐transfer insulator in which a few percent of Ce doping triggers a metal–insulator transition is investigated. While scanning probe microscopy indicates a complete switching of the ferroelectric gate, in‐depth atomic‐scale polarization mapping with scanning transmission electron microscopy reveals incomplete polarization reversal at the interface. Therefore, transport measurements show that the electronic properties of the Mott channel are virtually unchanged by the polarization direction. Nevertheless, in nanometer size areas where interfacial polarization switching occurs, dramatic changes of the electronic properties of (Ca,Ce)MnO3 are revealed. These results indicate how the performance of mesoscale Mott devices is hindered, and at the same time reveal the possibility of nanoscale energy‐efficient Mott transistors.

Configurable Resistive Response in BaTiO3 Ferroelectric Memristors via Electron Beam Radiation.

Ferroelectric oxide memristors are currently in the highlights of a thriving area of research aiming at the development of nonvolatile, adaptive memories for applications in neuromorphic computing. However, to date a precise control of synapse-like functionalities by adjusting the interplay between ferroelectric polarization and resistive switching processes is still an ongoing challenge. Here, it is shown that by means of controlled electron beam radiation, a prototypical ferroelectric film of BaTiO3 can be turned into a memristor with multiple configurable resistance states. Ex situ and in situ analyses of current/voltage characteristics upon electron beam exposure confirm the quasi-continuous variation of BaTiO3 resistance up to two orders of magnitude under the typical experimental conditions employed in electron beam patterning and characterization techniques. These results demonstrate an unprecedented effective route to locally and scalably engineering multilevel ferroelectric memristors via application of moderate electron beam radiation.

Effect of Sr and La co-doping on structural and electrical properties of RF sputtered PZT thin films

Doping in lead-zirconate-titanate (PZT) thin films is on the rise for next generation micro-electro-mechanical systems (MEMS) and energy harvesting applications, owing to their improved ferroelectric and piezoelectric properties. Strontium, lanthanum and neodymium like elements are the most exploited for such applications. This paper reports realization of a PZT thin film with strontium and lanthanum co-doping in tandem, Pb1−x−3y/2SrxLay(Zr0.56Ti0.44)O3 x = 0.06, y = 0.03 (PSLZT), by RF sputtering process. Different process conditions like substrate temperature from 250 °C–350 °C and annealing temperature from 650 °C–750 °C are studied to achieve pyrochlore free PSLZT thin film. The structure, surface morphology, surface topography and ferroelectric characteristics are investigated using x-ray diffraction (XRD), Atomic Force Microscopy (AFM), Field Emission Scanning Electron Microscopy (FE-SEM) and P-E analyser, respectively. Nanoscale polarization switching processes and the local surface displacements are studied to ascertain that the PSLZT thin film exhibits the ferroelectric and piezoelectric properties. Experimental results reveal that the present PSLZT thin film has a polarization of 5.5 μC cm−2, leakage current density of 10−5 A cm−2 and piezoelectric charge coefficient, d33, of 87 pm V−1, which are suitable for realization of various new piezoelectric MEMS sensors.

Investigation on energy dissipation by polarization switching in ferroelectric materials and the feasibility of its application in sound wave absorption

In the current paper, energy dissipation via stress-induced polarization switching in ferroelectric material is investigated, and the feasibility of its application in sound wave absorption is analysed. For the system design and analysis, a phenomenological model based on the modified Landau phase transition theory is constructed to describe the polarization switching. A simple and robust energy dissipation prototype is introduced. The hysteretic dynamics associated with the polarization switching process and the energy dissipation process are investigated. The dependence of the energy dissipation on the bias voltage, frequency, and resistance is analysed in detail. The energy dissipation density in one cycle is calculated. It is shown that the resistance has a strong influence on the energy dissipation. Meanwhile, a better energy dissipation effect could be obtained by setting an appropriate resistance for the low-frequency excitation. The feasibility of using ferroelectric materials for low-frequency sound wave absorption is validated. For a specific acoustic energy dissipation device, corresponding design and analysis will be discussed in our future papers.

Совместное исследование диэлектрического и пьезотклика релаксора Pb(Mg-=SUB=-1/3-=/SUB=-Nb-=SUB=-2/3-=/SUB=-)O-=SUB=-3-=/SUB=- в реальном масштабе времени при приложении электрического поля

The method of the study of the polarization switching processes in ferroelectrics by an external electric field using synchronous measurement of an electric impedance and piezoelectric response is described. Using the developed technique, the switching processes in the electric field-induced ferroelectric phase (FE) of lead magnoniobate are studied. It is shown that, upon the initial occurrence of the SE phase, a multidomain structure with a weak piezoelectric response is formed. A change in the direction of the external field leads to polarization switching, and the switching process passes through an intermediate glassy phase. raining a sample by repeated switching leads to a sharp increase in the piezoelectric response, which can be attributed to the formation of a single-domain state.

Ultrafast measurements of polarization switching dynamics on ferroelectric and anti-ferroelectric hafnium zirconium oxide.

The ultrafast measurements of polarization switching dynamics on ferroelectric (FE) and antiferroelectric (AFE) hafnium zirconium oxide (HZO) are studied. The transient current during the polarization switching process is probed directly on the nanosecond scale. The switching time is determined to be as fast as 10 ns to reach fully switched polarization with characteristic switching times of 5.4 ns for FE HZO and 4.5 ns for AFE HZO by the nucleation limited switching model. The limitation by the parasitic effect on capacitor charging is found to be critical in the correct and accurate measurements of intrinsic polarization switching speed of HZO.

Polarization and switching processes in multicomponent piezoceramic based on PZT with a highly diffuse phase transition

It is known that in a multicomponent piezoceramics with a certain ratio of the components of the solid solution and modifying impurities, the phase transition from the ferroelectric phase to the paraelectric phase occurs in several stages. The temperature interval of structural and polarization changes can reach hundreds of degrees. In the present work polarization switching processes and properties of a piezoceramic material based on PZT studied.

Investigation of polarization switching processes in 0.8PMN-0.2PT single crystal in a temperature range from 100 K to 300 K

Ferroelectric hysteresis loops were measured and the temperature evolution of the coercive field traced in [110]-oriented 0.8Pb(Mb1/3Nb2/3)O3–0.2PbTiO3 single crystal in the temperature range from 120 to 300 K at frequencies from 2 to 50 Hz. It was found that the coercive field rised with decreasing temperature in power-law manner at all frequencies. Temperature-dependent hysteresis model was used for approximation of acquired coercive field-temperature dependences. It was shown that nanoscale ferroelectric domains could be created at PMN-20PT surface by voltage pulses applied between the tip of atomic force microscope and bottom electrode at temperatures as low as 100 K.

Numerical investigation of nanoscale electromechanical response in a ferroelectric perovskite through an atomistic field theory

An atomistic field theory was introduced to study the electromechanical response in a ferroelectric perovskite at nanoscale. Based on a shell model potential, the polarization switching process of a ferroelectric perovskite PbTiO3 under electric field and mechanical loading was investigated. The simulation results showed that external electric field applied opposite to the initial polarization direction could result in 180° polarization switching in PbTiO3 nanostructures as the external electric field increased. On the other hand, mechanical loading applied parallel to initial polarization could cause 90° nanoscale polarization rotation in PbTiO3. Ultimately, the simulation results indicated that the coupled loads of electric field and mechanical loading would influence the polarization switching in PbTiO3 nanostructures.

Domain Wall Motions in a Near-Morphotropic Pb(Zr,Ti)O3 Under Mechanical Stress Observed by In Situ Piezoresponse Force Microscopy

Many important material properties of ferroelectric ceramics such as piezoelectric coefficient and hysteresis curve are governed by domain structures and their evolution processes. In the present work, domain wall motions in a near-morphotropic Pb(Zr,Ti)O3 under an external compressive stress were observed using in situ piezoresponse force microscopy (PFM). This specific PZT material was chosen due to its complex microstructure, which originates from the coexistence of tetragonal and rhombohedral phases. A micromechanical test rig was installed on the sample stage controller, enabling precise control of the sample position. For the real-time strain monitoring of the PZT sample, a strain gauge was attached to the sample surface on which the PFM scan was conducted. In addition, analysis of the ferroelectric domain structure was assisted by using the electron backscatter diffraction (EBSD) technique to identify the habit planes of non- 180° domain walls and grain boundaries in the PFM images. From a certain grain, a set of large non-180° needle-like domain patterns in the (101) plane were observed before applying a mechanical stress. With increasing compressive stress levels, another set of non-180° needle-like domain patterns grew in the (011) plane, overwriting the domain patterns in the (101) plane. This indicates that polarization switching processes in ferroelectric ceramics take place via a pattern evolution based on the pre-existing domain patterns. (Received October 22, 2018; Accepted November 19, 2018)

Double Hysteresis Loops in Proper Uniaxial Ferroelectrics

For the first time in a bulk proper uniaxial ferroelectrics, double antiferroelectric-like hysteresis loops have been observed in the case of Sn$_2$P$_2$S$_6$ crystal. The quantum anharmonic oscillator model was proposed for description of such polarization switching process. This phenomenon is related to three-well local potential of spontaneous polarization fluctuations at peculiar negative ratio of coupling constants which correspond to inter-site interaction in given sublattice and interaction between two sublattices of Sn$_2$P$_2$S$_6$ modeled crystal structure. Obtained data can be used for development of triple-level cell type memory technology.

Real-Time Polarization Switch Characterization of HfZrO4 for Negative Capacitance Field-Effect Transistor Applications

In this letter, the real-time polarization switching process in HfZrO4 ferroelectric film is investigated at high speed (100 MHz, highest up-to-date) by using the ultrafast measurements system. Based on the measurements over a wide range of speed from ms to ns, clear and detailed time-dependent behaviors of the polarization switch of HfZrO4 are captured. HfZrO4 film with 10 nm in thickness still exhibits ferroelectric characteristics measured with a voltage sweep period from 4 ms to 20 ns and a voltage amplitude of 4 V. The phenomenon of polarization switching diminishes distinctively with the increase of measurement speed. When the measurement speed reaches as fast as 10 ns, the polarization process could not be clearly observed. Therefore, high-speed application of negative capacitance field-effect transistor should be optimized to prevent potential problems caused by the insufficient polarization.

Flexible polarization rotation at the ferroelectric/metal interface as a seed for domain nucleation

The absence of a realistic polarization screening scenario at the pivotal ferroelectric-metal interface impedes the widespread application of low-dimensional ferroelectric heterostructures. Employing quantitative atom-resolved (scanning) transmission electron microscopy and first-principles calculations, we report that structural and chemical reconstruction universally lowers symmetry of the ferroelectric-metal interface. Irrespective of structural and strain mismatch, chemical termination and diffusion, polar catastrophe, and electrode type, the polarization screening is executed by a flexible polarization rotation at several-unit-cell-thick interfaces. By combining nanoscale and atomic-scale microscopy investigations, our ex situ electric-field biasing experiments reveal that the monoclinically distorted interfaces may act as seeds to nucleate new domains during the polarization switching process. These findings suggest that the long-standing fatigue issue is expected to be overcome by interface modification engineering at the monolayer scale.

Fractal model of polarization switching kinetics in ferroelectrics under nonequilibrium conditions of electron irradiation

The paper presents the results of the fractal and multifractal analysis of polarization switching current in ferroelectrics under electron irradiation, which allows statistical memory effects to be estimated at dynamics of domain structure. The mathematical model of formation of electron beam-induced polarization current in ferroelectrics was suggested taking into account the fractal nature of domain structure dynamics. In order to realize the model the computational scheme was constructed using the numerical solution approximation of fractional differential equation. Evidences of electron beam-induced polarization switching process in ferroelectrics were specified at a variation of control model parameters.

Ferroelectricity in Hf0.5Zr0.5O2 Thin Films: A Microscopic Study of the Polarization Switching Phenomenon and Field-Induced Phase Transformations.

Because of their full compatibility with the modern Si-based technology, the HfO2-based ferroelectric films have recently emerged as viable candidates for application in nonvolatile memory devices. However, despite significant efforts, the mechanism of the polarization switching in this material is still under debate. In this work, we elucidate the microscopic nature of the polarization switching process in functional Hf0.5Zr0.5O2-based ferroelectric capacitors during its operation. In particular, the static domain structure and its switching dynamics following the application of the external electric field have been monitored with the advanced piezoresponse force microscopy (PFM) technique providing a nm resolution. Separate domains with strong built-in electric field have been found. Piezoresponse mapping of pristine Hf0.5Zr0.5O2 films revealed the mixture of polar phase grains and regions with low piezoresponse as well as the continuum of polarization orientations in the grains of polar orthorhombic phase. PFM data combined with the structural analysis of pristine versus trained film by plan-view transmission electron microscopy both speak in support of a monoclinic-to-orthorhombic phase transition in ferroelectric Hf0.5Zr0.5O2 layer during the wake-up process under an electrical stress.

Anisotropic domain switching in Pb(Mg1/3Nb2/3)O3‐0.30PbTiO3 single crystals with rhombohedral structure

AbstractAnisotropic domain switching paths in [001]‐, [011]‐, and [111]‐poled Pb(Mg1/3Nb2/3)O3‐0.30PbTiO3 single crystals were studied by in situ polarized light microscopic driven by an antiparallel electric field. Orientation‐dependent electric field induced polarization and strain behaviors were investigated systematically. For [001]‐oriented crystals, only one‐step 71° switching occurred during the domain switching process, resulting in the appearance of stripe domain walls whose traces on (001) plane were along 45° or 135° with respect to [100] direction. But for [011]‐oriented samples, a two‐step 71° switching was observed during 109° switching and the projections of formed twin domain walls on the (011) plane are along 35.3° or 144.7° with respect to [01] direction. Moreover, a three‐step 71° switching was found during 180° switching in [111]‐oriented samples. It was demonstrated by the produced domain walls whose projections on the (10) plane are along 35.3°, 90° or 160.6° with respect to [11] direction. The energetically motivated mechanism based on multistep polarization switching process was also proposed to explain the anisotropic domain switching paths. Our results provided a visualized observation on the ferroelectric domain switching process and also laid the solid foundations for controlling polarization order parameter in ferroelectric single crystals.

Polarization switching mechanism in surface-emitting semiconductor lasers

Within the scope of the earlier proposed approach to the description of polarization dependences in VCSEL based on analysis of the experimental and theoretical data, an explicit expression for the function describing the relationship between the amplification anisotropy and the current density is suggested. The conducted numerical calculations support the peculiarities of the polarization switching (PS) process and enable one to explain the effect of the PS point anomalous shift when the current variation rate is high. A special attention is given to a fairly clear physical interpretation of the formation of polarization radiation in VCSEL.

Enhanced piezoelectric properties and strain response in 〈001〉 textured BNT-BKT-BT ceramics

Highly 〈001〉 textured (~81%) ternary BNT-BKT-BT ceramics are prepared by reactive templated grain growth (RTGG) method with plate-like Bi4Ti3O12 particles as templates. Outstanding electric properties, which are both higher than state of art BNT-based ceramics, emerge in the aforementioned sample due to the grain orientation. For the textured ceramics, a high piezoelectric constant d33 of 314pC/N could be obtained, which is ~1.4-fold larger than that of a random one (221pC/N). A high electro-strain response (~0.41%) is obtained at a low applied electric field (4kV/mm) in textured ceramics, with the normalized strain d33⁎ (Smax/Emax)=1030pm/V near the TF-R (the temperature of ferroelectric to ergodic relaxor state transition). Moreover, the evolution process of relaxor phases is studied. The texture technique also could improve the TF-R from 70°C to 100°C, enhancing the temperature stability. In addition, the polarization switching process in ferroelectric phase and ergodic relaxor state are analyzed in this work, respectively.

Polarization Switching Response and Domain Structure Dynamics Induced in Ferroelectrics by Incident Electron Beams

The article is devoted to the analysis of polarization reversal process arising in ferroelectrics under electron beam exposure. The advanced model was proposed to describe the polarization switching process in ferroelectrics as well as formation of polarization switching response in electron beam-induced polarization current mode of SEM taking into account the specific character of domain structure dynamics. Simulation of polarization switching current in TGS ferroelectric crystals was performed to estimate the main characteristics of electron beam-induced polarization reversal processes.

Mapping Nanoscale Switching Behavior of PZT Domain Patterns by Scanning Probe Microscope

The switching current of the PZT domain patterns was detected by the conductive atomic force microscopy. The impact of the scan rate on the current contrast was studied. Successive current images of domain evolution during the polarization switching process were obtained. The impact of the local force exerted by the tip and the polarization cycles of the patterns were studied. The results suggested that the compressive strain exerted by the tip can decrease the piezoelectric coercive field and the polarization fatigue can increase the piezoelectric coercive field in the polarization inversion process from bottom to top.