A5079305068- Ferroelectric and Negative Capacitance Devices
- Advanced Memory and Neural Computing
- Ferroelectric and Piezoelectric Materials
- Multiferroics and related materials
- Semiconductor materials and devices
- MXene and MAX Phase Materials
- Electronic and Structural Properties of Oxides
- Magnetic and transport properties of perovskites and related materials
- Transition Metal Oxide Nanomaterials
- Acoustic Wave Resonator Technologies
- Advanced Condensed Matter Physics
- Neuroscience and Neural Engineering
- Conducting polymers and applications
- Neural dynamics and brain function
- Gas Sensing Nanomaterials and Sensors
- Solid-state spectroscopy and crystallography
- Machine Learning and ELM
- Fuel Cells and Related Materials
- Nonlocal and gradient elasticity in micro/nano structures
- Advanced Steganography and Watermarking Techniques
- Electrocatalysts for Energy Conversion
- Dielectric properties of ceramics
- CCD and CMOS Imaging Sensors
- Electrical Fault Detection and Protection
- Green IT and Sustainability
Seoul National University of Education
2016-2025
Seoul National University
2009-2025
Seoul Institute
2017
Government of the Republic of Korea
2017
Hankuk University of Foreign Studies
2017
Institute for Basic Science
2017
Gachon University
2014
Rutgers, The State University of New Jersey
2010-2013
Samsung (South Korea)
2011
The random circuit breaker network model is proposed for unipolar resistance switching behavior. This describes reversible dynamic processes involving two quasi-metastable states. formation and rupture of conducting channels (see figure) in the polycrystalline TiO2 thin films may be analyzed by self organized avalanche process model. Supporting information this article available on WWW under http://www.wiley-vch.de/contents/jc_2089/2008/adma200702024_s.pdf or from author. Please note:...
The atomic-scale structure of hafnium oxide explains ferroelectric properties for very thin films.
We observed two types of reversible resistance switching (RS) effects in a NiO film: memory RS at low temperature and threshold high temperature. were able to control the type by thermal cycling. These phenomena explained using new dynamic percolation model that can describe rupture formation conducting filaments. showed are governed stability filaments, which arise from competition between Joule heating dissipation. This work provides us understandings on basic mechanism their interrelation.
We discovered stripe patterns of trimerization-ferroelectric domains in hexagonal ${\mathrm{REMnO}}_{3}$ ($\mathrm{RE}=\mathrm{Ho},\ensuremath{\cdots},\mathrm{Lu}$) crystals (grown below ferroelectric transition temperatures (${T}_{c}$), reaching up to $1435\text{ }\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$), contrast with the vortex ${\mathrm{YMnO}}_{3}$. These roughen appearance numerous loop through thermal annealing just ${T}_{c}$, but domain turn vortex-antivortex a freezing process...
We fabricated Pt∕NiO∕Pt capacitor structures with various bottom electrode thicknesses tBE and investigated their resistance switching behaviors. The capacitors tBE⩾50nm exhibited typical unipolar memory switching, while those tBE⩽30nm showed threshold switching. This interesting phenomenon can be explained in terms of the temperature-dependent stability conducting filaments. In particular, thinner makes dissipation Joule heat less efficient, so filaments will at a higher temperature become...
Flexoelectricity can play an important role in the reversal of self-polarization direction epitaxial BiFeO3 thin films. The flexoelectric and interfacial effects compete with each other to determine state. In Region I, is downward because effect more dominant than effect. II, upward, becomes
A TiO2/VO2 oxide double-layer nanocrossbar to overcome the sneak path problem in bipolar resistive memory is proposed. TiO2 and VO2 thin films function as a bidirectional switch, respectively. The new structure suggests that ultrahigh densities can be achieved with 2D array layout. By stacking into 3D structure, density even higher. Detailed facts of importance specialist readers are published "Supporting Information". Such documents peer-reviewed, but not copy-edited or typeset. They made...
Field-induced switching of ferroelectric domains with a topological vortex configuration is studied by atomic imaging and electrical biasing in an electron microscope, revealing the role defects on topologically-guided change domain-wall pairs hexagonal manganite.
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....
Abstract The groundbreaking discovery of unconventional ferroelectricity in HfO 2 opens exciting prospects for next‐generation memory devices. However, the practical implementation, particularly its epitaxial stabilization and a clearer understanding intrinsic has been significant challenge. study arouses potential importance atomic layer deposition (ALD) mass production modern industries, demonstrating proficiency achieving growth ferroelectric Hf 0.5 Zr O (HZO) thin films on...
We fabricated Pb(Zr0.52Ti0.48)O3-NiFe2O4 composite films consisting of randomly dispersed NiFe2O4 nanoparticles in the Pb(Zr0.52Ti0.48)O3 matrix. The structural analysis revealed that crystal axes are aligned with those ferroelectric has good and magnetic properties. measured transverse longitudinal components magnetoelectric voltage coefficient, which supports postulate effect comes from direct stress coupling between magnetostrictive piezoelectric grains.
The interaction among topological defects can induce novel phenomena such as disclination pairs in liquid crystals and superconducting vortex lattices. Nanoscale vortices with swirling ferroelectric, magnetic, structural antiphase relationships were found multiferroic h-YMnO 3 . Herein, we report the discovery of intriguing, but seemingly irregular configurations a zoo antivortices. These be neatly analyzed terms graph theory reflect nature self-organized criticality complexity phenomena....
Resistive switching memory, which is mostly based on polycrystalline thin films, suffers from wide distributions in parameters-including set voltage, reset and resistance-in their low- high-resistance states. One of the most commonly used methods to overcome this limitation introduce inhomogeneity. By contrast, paper, we obtained uniform resistive parameters sufficiently low forming voltage by maximizing uniformity an epitaxial film. To achieve result, deposited SrFeOx/SrRuO3 heteroepitaxial...
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...
We investigated the resistive switching characteristics of two types Pt∕NiO∕Pt structures with epitaxial and polycrystalline NiO layers. Both these exhibited unipolar switching. Pt/epitaxial-NiO∕Pt showed unstable or no resistance state change after several repeated runs. Pt/polycrystalline-NiO∕Pt very reproducible The experimental data indicated that microstructural defects (e.g., grain boundaries) played crucial roles in reliability behavior. This was further supported by first-principles...
The wide distributions of switching voltages in unipolar currently pose major obstacles for scientific advancement and practical applications. Using NiO capacitors, we investigated the reset voltage current. We found that they scaled with resistance value Ro low state scaling exponents varied at Ro≈30 Ω. explain these intriguing behaviors their crossovers by analogy percolation theory. show connectivity conducting filaments plays a crucial role process.
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 Hafnium oxides‐based ferroelectric materials are promising for applications in nonvolatile memory devices. To control the ferroelectricity of such materials, it is necessary to tune their polymorphism, interfacial features, and defect (oxygen vacancy) distribution. A strategy described enhancing properties polycrystalline hafnium zirconium oxide (HZO) ultrathin films by modifying oxygen pressure during device preparation stage, which involves thermal annealing TiN electrodes that...
Utilizing the local dynamic charge behaviors, authors unveiled distinctive origins of various behaviors in oxides and hybrid halides by highly sensitive accumulative spectroscopy.
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...
An epitaxial brownmillerite thin-film platform with tuned oxygen vacancy channels is used to realize high ReRAM performance.