A5012578697- Ferroelectric and Negative Capacitance Devices
- Semiconductor materials and devices
- Electronic and Structural Properties of Oxides
- MXene and MAX Phase Materials
- Advanced Memory and Neural Computing
- Magnetic and transport properties of perovskites and related materials
- Ferroelectric and Piezoelectric Materials
- Advanced Condensed Matter Physics
- Autonomous Vehicle Technology and Safety
- Traffic control and management
- Vehicle Dynamics and Control Systems
- Multiferroics and related materials
- Advanced Nanomaterials in Catalysis
- ZnO doping and properties
- Thin-Film Transistor Technologies
- Computational and Text Analysis Methods
- Diverse Approaches in Healthcare and Education Studies
- Nanofluid Flow and Heat Transfer
- Nanopore and Nanochannel Transport Studies
- TiO2 Photocatalysis and Solar Cells
- Advanced Photocatalysis Techniques
- Acoustic Wave Resonator Technologies
- Technology and Data Analysis
- Fault Detection and Control Systems
- Quantum and electron transport phenomena
Seoul National University of Education
2017-2024
University of Wisconsin–Madison
2024
Seoul National University
2007-2020
Hyundai Motors (South Korea)
2017
Hanyang University
2011
North Carolina Agricultural and Technical State University
2008
The atomic-scale structure of hafnium oxide explains ferroelectric properties for very thin films.
Inorganic/organic nanocomposite counter electrodes comprised of sheetlike CoS nanoparticles dispersed in polystyrenesulfonate-doped poly(3,4-ethylenedioxythiophene (CoS/PEDOT:PSS) offer a synergistic effect on catalytic performance toward the reduction triiodide for dye-sensitized solar cells (DSSCs), yielding 5.4% power conversion efficiency, which is comparable to that conventional platinum electrode (6.1%). The electrochemical impedance spectroscopy (EIS) and cyclic voltammetry...
The ferroelectricity in ultrathin HfO2 offers a viable alternative to ferroelectric memory. A reliable switching behavior is required for commercial applications; however, many intriguing features of this material have not been resolved. Herein, we report an increase the remnant polarization after electric field cycling, known as "wake-up" effect, terms change polarization-switching dynamics Si-doped thin film. Compared with pristine specimen, film exhibited partial finite number behaviors....
The recent demand for analogue devices neuromorphic applications requires modulation of multiple nonvolatile states. Ferroelectricity with polarization states enables various architectures. However, deterministic control ferroelectric conventional materials has been met accessibility issues. Here, we report unprecedented stable robust stability in HfO2. Through the combination voltage measurements, hysteresis temperature dependence analysis, piezoelectric force microscopy, first-principles...
Abstract Investigations concerning oxygen deficiency will increase our understanding of those factors that govern the overall material properties. Various studies have examined relationship between and phase transformation from a nonpolar to polar in HfO 2 thin films. However, there are few reports on effects deficiencies switching dynamics ferroelectric itself. Herein, we report oxygen- induced enhancement properties Si-doped By controlling annealing conditions, controlled concentration...
Oxygen-vacancy-ordered brownmillerite oxides offer a reversible topotactic phase transition by significantly varying the oxygen stoichiometry of material without losing its lattice framework. This leads to substantial changes in physical and chemical properties oxides, including electrical ion conductivity, magnetic state, diffusivity. In this study, variations resistive switching mode epitaxial SrFeO2.5 thin film device were studied systematically controlling concentration, which could be...
Abstract Since the discovery of two-dimensional electron gas at LaAlO 3 /SrTiO interface, its intriguing physical properties have garnered significant interests for device applications. Yet, understanding response to electrical stimuli remains incomplete. Our in-situ transmission microscopy analysis a under bias reveals key insights. Inline holography visualized field-induced modulation while energy loss spectroscopy showed negligible electromigration oxygen vacancies. Instead, atom-resolved...
We report on the ferroelectricity of a Y-doped HfO2 thin film epitaxially grown Si substrate, with an yttria-stabilized zirconia buffer layer pre-deposited substrate. Piezoresponse force microscopy results show ferroelectric domain pattern, implying existence in epitaxial film. The stabilized form metal-ferroelectric-insulator-semiconductor structure exhibits hysteresis clear switching current polarization-voltage measurements. also demonstrates retention comparable to that perovskite-based...
This paper describes the design of a fully automated driving algorithm for in complex urban scenarios and motorways with satisfactory safety level. The proposed consists following three steps: surround recognition, motion planning, vehicle control. recognition system main modules: object classification, vehicle/non-vehicle tracking dynamic drivable area determination. All modules utilize information from potentially commercializable sensors such as vision sensors, radars, lidar sensors....
Abstract Ferroelectricity occurs in crystals with broken spatial inversion symmetry. In conventional perovskite oxides, concerted ionic displacements within a 3D network of transition‐metal–oxygen polyhedra ( M O x ) manifest spontaneous polarization. Meanwhile, some 2D networks foster geometric ferroelectricity magnetism, owing to the distortion polyhedra. Because fundamentally different mechanism network, one can further challenge an uncharted 1D channel and estimate its feasibility. Here,...
Herein, we report the ferroelectricity of HfxZr1–xO2 (HZO) thin films crystallized via excimer laser annealing at 25 °C under atmospheric conditions. We characterized structure and antiferroelectric/ferroelectric properties HZO using X-ray diffraction standard polarization–voltage hysteresis. The laser-annealed Hf0.5Zr0.5O2 film was gradually with increasing pulse number. series exhibited systemic changes in variations Zr concentration. In addition, constructed a phase diagram films.
Abstract Charge ordering (CO), characterized by a periodic modulation of electron density and lattice distortion, has been fundamental topic in condensed matter physics, serving as potential platform for inducing novel functional properties. The charge-ordered phase is known to occur doped system with high d -electron occupancy, rather than low occupancy. Here, we report the realization electron-doped (100) SrTiO 3 epitaxial thin films that have lowest occupancy i.e., 1 - 0 . Theoretical...
We report variations in the characteristic ferroelectric switching time and interface free carrier concentration associated with wake-up split-up behaviors of a 4.2 mol. % Si-doped HfO2 thin film. Prior to development behavior, films exhibited behavior; remanent polarization increased on repeated electric field cycling. After degradation values splitting current peaks when lower was swept; this is referred as behavior. An investigation dynamics revealed retardation, followed by recovery, for...
The scale-free ferroelectricity with superior Si compatibility of HfO2 has reawakened the feasibility scaled-down nonvolatile devices and beyond complementary metal–oxide–semiconductor (CMOS) architecture based on ferroelectric materials. However, despite rapid development, fundamental understanding, control metastable phase in terms oxygen ion movement remain ambiguous. In this study, we have deterministically controlled orientation a single-crystalline thin film via movement. We induced...
We report on the inhomogeneity of internal bias according to Zr alloy concentration confirmed by ferroelectric switching dynamics ${\mathrm{Hf}}_{1\ensuremath{-}x}{\mathrm{Zr}}_{x}{\mathrm{O}}_{2}$ thin films. The analytic model for was considered in terms dipole-dipole interaction accompanied variation. ferroelectricity and films were investigated using conventional electrical measurements local piezoresponse microscopy. Analysis static dynamic polarization reversal revealed a correlation...
Ferroelectric domain walls, recognized as distinct from the bulk in terms of symmetry, structure, and electronic properties, host exotic phenomena including conductive ferroelectric vortices, novel topologies, negative capacitance. Contrary to conventional understanding, our study reveals that structure walls HfO2 closely resembles its bulk. First, first-principles simulations unveil robust ferroelectricity is supported by bosonic pairing all anionic phonons HfO2. Strikingly, paired strongly...