A5047225732- Metallic Glasses and Amorphous Alloys
- Electronic and Structural Properties of Oxides
- Ferroelectric and Piezoelectric Materials
- Phase-change materials and chalcogenides
- Glass properties and applications
- High Entropy Alloys Studies
- Multiferroics and related materials
- Semiconductor materials and devices
- Additive Manufacturing Materials and Processes
- Quasicrystal Structures and Properties
- Magnetic and transport properties of perovskites and related materials
- Graphene research and applications
- High-Temperature Coating Behaviors
- Material Dynamics and Properties
- Advanced materials and composites
- Advancements in Solid Oxide Fuel Cells
- Metal and Thin Film Mechanics
- Nanoporous metals and alloys
- Aluminum Alloys Composites Properties
- Magnetic properties of thin films
- Aluminum Alloy Microstructure Properties
- Advancements in Battery Materials
- 2D Materials and Applications
- Gas Sensing Nanomaterials and Sensors
- Ferroelectric and Negative Capacitance Devices
National Cheng Kung University
2025
Korea Institute of Science and Technology
2015-2024
Korea University of Science and Technology
2015-2024
Korea Advanced Institute of Science and Technology
2013-2023
Korea Research Institute of Chemical Technology
2019-2022
Korea Institute of Science & Technology Information
2019-2022
KIST Medical College
2020
Government of the Republic of Korea
2020
Seoul Institute
2017-2020
University of Rochester
2017
Oxygen octahedral tilts underpin the functionality of a large number perovskite-based materials and heterostructures with competing order parameters. We show how precise analysis atomic column shapes in Z-contrast scanning transmission electron microscopy images can reveal polarization tilt behavior across uncharged charged domain walls BiFeO3. This method is capable visualizing to much higher thicknesses than phase contrast imaging. find that transition wall atomically abrupt, while...
Abstract For the utilization of graphene in various energy storage and conversion applications, it must be synthesized bulk with reliable controllable electrical properties. Although nitrogen-doped shows a high doping efficiency, its properties can easily affected by oxygen water impurities from environment. We here report that boron-doped nanoplatelets desirable prepared simultaneous reduction boron-doping oxide (GO) at annealing temperature. B-doped 1000 °C show maximum boron concentration...
Many applications, most notably memory and optical devices use ferroelectric materials. For many years the evolution of field has revolved around understanding materials science behind complex structures like artificial superlattices based mainly on perovskite-structure oxides. The recent discovery ferroelectricity in fluorite-structure oxides opened a new research direction. However, formation unstable or metastable phases atomic layer deposited fluorite inhibited full origin these This...
The origin of the irreversible capacity O3-type NaFeO2 charged to high voltage is investigated by analyzing oxidation state Fe and phase transition layered cathodes for sodium-ion batteries during charging process. In-situ X-ray absorption spectroscopy results revealed that charge compensation does not occur through Fe3+/Fe4+ redox reaction sodium extraction as no significant shift energy was observed in K-edge. These were reinforced with ex-situ near-edge spectroscopy, which suggests oxygen...
van der Waals (vdW) magnetic materials provide an ideal platform to study low-dimensional magnetism. However, observations of characteristics these layered truly distinguishing them from conventional thin film systems have been mostly lacking. In effort investigate properties unique vdW materials, we examine the exchange bias effect, a phenomenon emerging at ferromagnetic-antiferromagnetic interface. Exchange is observed in naturally oxidized ferromagnet Fe3GeTe2, owing antiferromagnetic...
Chemical short-range order in disordered solid solutions often emerges with specific heat treatments. Unlike thermally activated ordering, mechanically derived (MSRO) a multi-principal-element Fe40Mn40Cr10Co10 (at%) alloy originates from tensile deformation at 77 K, and its degree/extent can be tailored by adjusting the loading rates under quasistatic conditions. The mechanical response multi-length-scale characterisation pointed to minor contribution of MSRO formation yield strength,...
The Y28Ti28Al24Co20 alloy undergoes metastable liquid phase separation in the under-cooled state and subsequently solidifies into two different Y-rich Ti-rich amorphous phases. Secondary occurs due to supersaturation of primary separated liquids as temperature decreases. Depending on degree local undercooling, a wide range length scale microstructure is observed. characteristic phases ∼250nm near air side ribbon, ∼25nm wheel ribbon.
Phase separating systems present a unique opportunity for designing composites with hierarchical microstructure at different length scales. We report here our success in synthesizing phase metallic glasses exhibiting the entire spectrum of microstructural possibilities expected from system. In particular, we novel core shell and structures spherical glassy droplets, resulting critical wetting behavior limited diffusion. also synthesis bulk glass The combination opens new avenue design glasses.
Direct atomic displacement mapping at ferroelectric interfaces by aberration corrected scanning transmission electron microscopy(STEM) (a-STEM image, b-corresponding profile) is combined with Landau-Ginsburg-Devonshire theory to obtain the complete interface electrostatics in real space, including separate estimates for polarization and intrinsic charge contributions. Detailed facts of importance specialist readers are published as "Supporting Information". Such documents peer-reviewed, but...
Using piezoresponse force microscopy in an ultrahigh vacuum, polarization switching has been detected and quantified epitaxial BiFeO${}_{3}$ films from 200 to about 4 unit cells thick. Local remnant was utilized probe both ferroelectric properties effects of imperfect electrical contacts. It found that the shape electromechanical hysteresis loops is strongly influenced by extrinsic dielectric gap, primarily through suppressing effect depolarizing field on spontaneous ultrathin films....
It has been a difficulty to form well-distributed nano- and mesosized inclusions in Bi2Te3-based matrix thereby realizing no degradation of carrier mobility at interfaces between for high thermoelectric performances. Herein, we successfully synthesize multistructured Bi0.4Sb1.6Te3 materials with Fe-rich nanoprecipitates sub-micron FeTe2 by conventional solid-state reaction followed melt-spinning spark plasma sintering that could be facile preparation method scale-up production. This study...
Interfaces, such as grain boundaries in a solid material, are excellent regions to explore novel properties that emerge the result of local symmetry-breaking. For instance, at interface layered-chalcogenide potential reconfiguration atoms can lead significant modification electronic because their complex atomic bonding structure. Here, we report experimental observation an electron source 60° twin Bi2Te3, representative material. First-principles calculations reveal interatomic distance...
Single-atom Pt/ceria catalysts are extremely active and thermally stable at over 700 °C in high-temperature solid oxide cell electrodes.
We investigate the voltage control of magnetism in a van der Waals (vdW) heterostructure device consisting two distinct vdW materials, ferromagnetic Fe3-xGeTe2 and ferroelectric In2Se3. It is observed that gate voltages applied to Fe3-xGeTe2/In2Se3 modulate magnetic properties with significant decrease coercive field for both positive negative voltages. Raman spectroscopy on shows voltage-dependent increase in-plane In2Se3 lattice constants polarities. Thus, field, regardless polarity, can...
The plethora of lattice and electronic behaviors in ferroelectric multiferroic materials heterostructures opens vistas into novel physical phenomena including magnetoelectric coupling tunneling. development new classes electronic, energy-storage, information-technology devices depends critically on understanding controlling field-induced polarization switching. Polarization reversal is controlled by defects that determine activation energy, critical switching bias, the selection between...
Intense upconversion green light emitting LiGdF<sub>4</sub>:Yb,Er-based tetragonal bipyramidal nanophosphors are synthesized <italic>via</italic> Y<sup>3+</sup> doping. The highly transparent composites emit bright luminescence.
Abstract Spherical black carbon aggregates were frequently observed in dust dry deposition Daejeon, Korea. They tens of micrometers diameter and presented a mixture several mineral phases. Transmission electron microscopy (TEM) observations with energy-dispersive X-ray spectroscopy (EDS) selected area diffraction pattern (SADP) analyses confirmed that the compact included significant amounts lead chromate (PbCrO 4 ). The compositions morphologies nanosized particles suggest they probably...