A5008934626- Ferroelectric and Piezoelectric Materials
- Ferroelectric and Negative Capacitance Devices
- Semiconductor materials and devices
- Acoustic Wave Resonator Technologies
- Multiferroics and related materials
- Electronic and Structural Properties of Oxides
- Immune Response and Inflammation
- MXene and MAX Phase Materials
- Crystallization and Solubility Studies
- X-ray Diffraction in Crystallography
- Microwave Dielectric Ceramics Synthesis
- Semiconductor materials and interfaces
- Silkworms and Sericulture Research
- Veterinary medicine and infectious diseases
- Magnetic and transport properties of perovskites and related materials
- Advancements in Semiconductor Devices and Circuit Design
- Machine Learning in Materials Science
- Coastal and Marine Dynamics
- Pediatric health and respiratory diseases
- Welding Techniques and Residual Stresses
- Metal and Thin Film Mechanics
- Mycobacterium research and diagnosis
- Crystallography and molecular interactions
- Advanced Thermoelectric Materials and Devices
- Metal Alloys Wear and Properties
National Institute for Materials Science
2016-2025
Aalto University
2024-2025
Tokyo Institute of Technology
2015-2024
Japan Science and Technology Agency
2002-2024
Kumamoto University
2023
Takeda (United States)
2023
Tokyo University of Science
2021-2023
National Institute of Advanced Industrial Science and Technology
2020-2022
Nagoya University
2021-2022
Shimizu (Japan)
2022
The ferroelectric properties and crystal structure of doped HfO2 thin films were investigated for different thicknesses, electrode materials, annealing conditions. Metal-ferroelectric-metal capacitors containing Gd:HfO2 showed no reduction the polarization within studied thickness range, in contrast to hafnia with other dopants. A qualitative model describing influence basic process parameters on was proposed. structural field cycling behavior examined. This revealed wake-up effect be...
To investigate the impact of mechanical stress on their ferroelectric properties, polycrystalline (Hf0.5Zr0.5)O2 thin films were deposited (111)Pt-coated SiO2, Si, and CaF2 substrates with thermal expansion coefficients 0.47, 4.5, 22 × 10−6/ °C, respectively. In-plane X-ray diffraction measurements revealed that SiO2 Si under in-plane tensile strain volume fraction monoclinic phase decreased as this increased. In contrast, compressive strain, was largest among three kinds substrates. The...
Abstract Ferroelectricity and Curie temperature are demonstrated for epitaxial Y-doped HfO 2 film grown on (110) yttrium oxide-stabilized zirconium oxide (YSZ) single crystal using Sn-doped In O 3 (ITO) as bottom electrodes. The XRD measurements enabled us to investigate its detailed structure including orientations of the film. ferroelectricity was confirmed by electric displacement filed – hysteresis measurement, which revealed saturated polarization 16 μC/cm . Estimated spontaneous based...
The ferroelectricity of (Al1−xScx)N (x = 0–0.34) thin films with various thicknesses was investigated. were prepared at 400 °C on (111)Pt/TiOx/SiO2/(001)Si substrates by the radio frequency dual-source reactive magnetron sputtering method using Al and Sc targets under pure N2 gas or a mixture Ar gases. film deposited showed larger remanent polarization than those + mixture. Ferroelectricity observed for x 0.10–0.34 about 140-nm-thick gas. 0.22 down to 48 nm in thickness from...
Ferroelectric hafnium and zirconium oxides have undergone rapid scientific development over the last decade, pushing them to forefront of ultralow-power electronic systems. Maximizing potential application in memory devices or supercapacitors these materials requires a combined effort by community address technical limitations, which still hinder their application. Besides favorable intrinsic material properties, HfO2–ZrO2 face challenges regarding endurance, retention, wake-up effect, high...
YO1.5-substituted HfO2 thin films with various substitution amounts were grown on (100) YSZ substrates by the pulsed laser deposition method directly from vapor phase. The epitaxial growth of film different YO1.5 was confirmed X-ray diffraction method. Wide-area reciprocal lattice mapping measurements performed to clarify crystal symmetry films. formed phases changed low-symmetry monoclinic baddeleyite high-symmetry tetragonal/cubic fluorite through an orthorhombic phase as amount increased...
Herein, ferroelastic domain switching from the nonpolar b-axis to polar c-axis oriented in 7%-YO1.5-substituted HfO2 (YHO-7) epitaxial ferroelectric films is demonstrated. Scanning transmission electron microscopy (STEM) indicates that polarization of a pristine film deposited on Sn-doped In2O3/(001)YSZ substrate by pulsed laser deposition method tends be along in-plane direction avoid strong depolarization field with respect out-of-plane direction. Applying an electric aids YHO-7 films....
In this study, the growth of (111)-oriented epitaxial and textured YO1.5-HfO2 (0.07:0.93 ratio) films using pulsed laser deposition method is presented. Epitaxial were prepared on ITO//(111)yttria-stabilized zirconia (YSZ) substrates (ITO: Sn-doped In2O3; YSZ: yttria-stabilized zirconia), while (111)Pt/TiOx/SiO2//Si with without an ITO buffer layer via grain coherent growth. Inserting increased volume fraction ferroelectric orthorhombic phase. Both uniaxially exhibited similar...
The ferroelectric properties of the (Hf0.5Zr0.5)O2 films on Pt/Ti/SiO2/Si substrate are investigated. It is found that crystallized by annealing in O2 and N2 atmospheres have similar crystal structures as well remanent polarization coercive fields. Weak temperature frequency dependences indicate hysteretic behavior HfO2-based originates not from mobile defects but rather lattice ionic displacement, case typical materials.
The possibility of the new class ferroelectric materials wurtzite structure simple chalcogenide was discussed using modern first-principles calculation technique. Ferroelectricity in (P63mc) can be understood by distortion from centrosymmetric P63/mmc relative displacement cation against anion along c-axis. Calculated potential surface these compounds shows typical double well between two polar variants. barriers for polarization switching were estimated to 0.25 eV/f.u. ZnO. It is slightly...
The effect of the heat treatment conditions on constituent phases and electrical properties (Hf0.5Zr0.5)O2 films deposited by metalorganic chemical vapor deposition was investigated. By using a low temperature or short duration for post-heat after deposition, volume fraction tetragonal phase increases, resulting in high dielectric constant. On other hand, monoclinic increased that were heat-treated at higher temperatures exposed to longer duration. ferroelectric with these greatly inferior....
Orientation control of {100}-oriented epitaxial orthorhombic 0.07YO1.5-0.93HfO2 films grown by pulsed laser deposition was investigated. To achieve in-plane lattice matching, indium tin oxide (ITO) and yttria-stabilized zirconia (YSZ) were selected as underlying layers. We obtained (100)- (001)/(010)-oriented on ITO YSZ, respectively. Ferroelastic domain formation confirmed for both X-ray diffraction using the superlattice that appeared only symmetry. The ferroelastic domains is believed to...
Ferroelectricity has been demonstrated in polycrystalline 7%Y-doped HfO2 (YHO7) films with thicknesses ranging from 10 to 930 nm, which were grown on (111)Pt/TiOx/SiO2/(001)Si substrates by pulsed laser deposition at room temperature and subsequent annealing 1000 °C. The X-ray diffraction pattern suggested that the major crystal phase consists of orthorhombic/tetragonal phases a small amount monoclinic even for 930-nm-thick film despite its thickness. Moreover, hysteresis loops associated...
The thickness dependences of the crystal structure and electric properties (111)-oriented epitaxial 0.07YO1.5-0.93HfO2 (YHO7) ferroelectric films were investigated for film range 10–115 nm. YHO7 grown by pulsed laser deposition or sputtering at room temperature subsequent heat treatment. As a substrate growth film, 10 wt. % Sn-doped In2O3(ITO)//(111) yttria-stabilized zirconia was used. X-ray diffraction measurements confirmed that main phase these orthorhombic up to 115-nm-thick films....
Abstract One of the general features ferroelectric systems is a complex nature polarization reversal, which involves domain nucleation and motion walls. Here, time‐resolved nanoscale imaging applied in conjunction with integral switching current measurements to investigate mechanism reversal yttrium‐doped HfO 2 (Y:HfO )—currently one most actively studied systems. More specifically, effect film microstructure on process investigated by performing comparative study behavior epitaxial...
The temperature dependence of ferroelectric properties was investigated for (Al0.8Sc0.2)N films 9–130 nm thick prepared on (111)Pt/TiOx/SiO2/Si substrates. coercive fields (Ec) these decreased with increasing measurement up to 523 K, irrespective film thickness, thus realizing polarization switching because the applicable maximum electric field is beyond Ec. As a resultant, remanent (Pr) above 100 μC cm−2 ascertained 9 at 373 and 423 which more than 5 times larger those HfO2-based same...
The crystal structure and ferroelectric properties of 12- to 18 nm-thick epitaxial YO1.5-HfO2 films with 5–9% YO1.5 on (111)ITO//(111)YSZ substrates are investigated clarify the formation mechanism phase. orthorhombic phase can be obtained by transformation from higher symmetric tetragonal surmounting a relatively low energy barrier. is for 6% 7% YO1.5-doped HfO2 heat treatment at 1000 °C. Although 5% film heat-treated °C in monoclinic phase, was increased 1200 because high temperature...
Semaphorin 3A (Sema3A) repels growing olfactory axons that express neuropilin-1 (NP-1), a receptor for Sema3A. The Sema3A-mediated axon guidance seems to be essential the formation of glomerular sensory map in bulb (OB). To understand whether and how Sema3A is involved formation, we examined OB adult Sema3A-deficient mice. In wild-type mice, NP-1-positive glomeruli form lateral medial bands avoid anteromedial ventral regions OB. OB, spread over entire consistently found ectopic arrangement...
The process of forming the ferroelectric orthorhombic phase was investigated for epitaxial 7% Y-doped (YHO7) films using in situ high-temperature X-ray diffraction. Epitaxial YHO7 were grown on (111) ITO-coated (111)YSZ substrates by pulsed laser deposition at room temperature and a subsequent heat treatment process. Films deposited crystallized as paraelectric monoclinic phase. partially changes to tetragonal above 600 °C perfectly transformed around 950 during heating. change from detected...
The effect of pure mechanical strain on ferroelectricity was investigated for (001)-one-axis-oriented (Al0.8Sc0.2)N films deposited (111)Pt-coated substrates with different thermal expansion coefficients. lattice strains were successfully controlled by using coefficients, though the composition is same. changes in remanent polarization (Pr) and coercive field (Ec) values these can be understood internal parameter u representing crystal anisotropy a wurtzite structure. These results suggest...
ABSTRACTABSTRACTA three-dimensional numerical model for predicting beach evolution has been developed by improving a wave calculation method and sediment transport formulas. The computation includes refraction, diffraction breaking. deformation adopts newly proposed formulas rates due to waves nearshore currents. validity of the confirmed applying it bottom topography around detached breakwater comparing results with experimental data.
GaFeO3-type AlFeO3 is consisted of oxygen octahedra and tetrahedra containing Al Fe ions known to have a non-centrosymmetric polar structure with space group Pna21. We tried grow epitaxial films on SrTiO3 (111) substrates by pulsed laser deposition technique. Both the atomic arrangement close-packed distance substrate surface played important roles in stabilizing substrate. Piezoresponse force microscopy measurements clearly showed that ferroelectricity at room temperature. In addition, film...
The properties of a potentially new class ferroelectric materials based on wurtzite-structured ZnO thin films are examined using the first-principles calculations. Theoretical P-E hysteresis loops were calculated fixed-D method for both unstrained and (biaxially) strained single crystals. Ferroelectric polarization switching in (S.G. P63mc) is shown to occur via an intermediate non-polar structure with centrosymmetric P63/mmc symmetry by displacement cations relative anions long-axis...