Siyoung Choi

A theoretically designed van der Waals ferromagnet Fe 4 GeTe 2 is synthesized and shows the nearly room temperature ferromagnetism.

Determining the atomic structures of oxide surfaces is critical for understanding their physical and chemical properties but also challenging because the breaking of atomic bonds in the formation of the surface termination can involve complex reconstructions. We used advanced transmission electron microscopy to directly observe the atomic structure of reduced titania (TiO2) (110) surfaces from directions parallel to the surface. In our direct atomic-resolution images, reconstructed titanium atom

We demonstrate that an exceptionally large strain can be induced in CaZrO 3 -modified alkaline-niobates by electric fields. The maximum induced strain of our niobate-based ceramics could reach more than 1,000 pm/V, which is a much higher value than that of commercial soft PZT ceramics. Atomic-scale annular bright-field (ABF) and annular dark-field (ADF) scanning transmission electron microscopy (STEM) directly revealed that individual single grains were composed of an electrically duplex core–sh

Abstract Oxygen vacancies have been treated as an important material engineering tool to enhance catalytic performance; for instance, oxygen vacancies suppress charge recombination at the Schottky interface, and thus, the photocurrent can be improved. In this regard, the gradient distribution of oxygen vacancies in n‐type metal oxides produces the ideal band structure for minimizing e − /h + recombination by efficient hole extraction; however, its achievement remains a daunting challenge. Here,

Atomic-scale defects strongly influence the electrical and optical properties of materials, and their impact can be more pronounced in localized dimensions. Here, we directly demonstrate that strain triggers the formation of oxygen vacancies in complex oxides by examining the tilt boundary of SrTiO3 bicrystals. Through transmission electron microscopy and electron energy loss spectroscopy, we identify strains along the tilt boundary and oxygen vacancies in the strain-imposed regions between disl

. Using atomic-resolution imaging/spectroscopic techniques and first-principles calculations, we determine the atomic-scale structure, composition, and bonding at the interface. The epitaxial antiperovskite/perovskite heterointerface is mediated by a coherent interfacial monolayer that interpolates between the two antistructures. We anticipate our results to be an important step for the development of functional antiperovskite/perovskite heterostructures, combining their unique characteristics s

A hindrance to the practical use of sodium-ion batteries is the lack of adequate anode materials. By utilizing the co-intercalation reaction, graphite, which is the most common anode material of lithium-ion batteries, was used for storing sodium ion. However, its performance, such as reversible capacity and coulombic efficiency, remains unsatisfactory for practical needs. Therefore, to overcome these drawbacks, a new carbon material was synthesized so that co-intercalation could occur efficientl

Thick polycrystalline pure PbTiO3 films with nano size grains were synthesized for the first time by aerosol deposition. Annealed 7 μm thick films exhibit well-saturated ferroelectric hysteresis loops with a remanent polarization and coercive field of 35 μC/cm(2) and 94 kV/cm, respectively. A large-signal effective d33,eff value of >60 pm/V is achieved at room temperature. The measured ferroelectric transition temperature (Tc) of the films ∼550 °C is >50 °C higher than the reported values (∼490

Two-dimensional (2D) materials are attracting increasing research interest owing to their distinct tunable physical properties. Moreover, the ubiquitous defects in 2D materials offer an opportunity to tailor their electronic properties. Recently, atomic-level structural modification methods for 2D materials have been developed, further triggering the need for the precise control of defects. Following the ground-breaking advancements in the atomic-scale characterization of defects in 2D materials

Dual-atom catalysts (DACs) offer a potential to accelerate reaction kinetics and provide versatile active sites by the synergistic combination of two metal atoms. However, the effects of dual-atom configurations and interatomic distances on catalytic performance have yet to be thoroughly investigated. Herein, we report DACs composed of Cu/Ni species anchored on N-doped carbon (Cu/Ni-NC) for the electrochemical CO 2 reduction reaction (CO 2 RR). The role of intermetal interactions as a function o