Ulsan National Institute of Science and Technology · Engineering
Professor Ju-Young Kim's research lab specializes in the design, synthesis, and mechanical characterization of advanced functional materials, with a focus on enhancing the ductility and strength of metallic glasses and semiconductors through nanostructuring and hybrid architectures. The lab explores size-dependent mechanical behaviors in nanoscale materials, particularly the 'smaller is stronger' phenomenon in nanopillars, and develops stretchable, flexible, and robust electronic systems using novel substrates and interconnects. Key research directions include the integration of metallic glasses with ductile metals or polymers to achieve high strength and large plasticity, as well as the mechanical reliability of perovskite and chalcogenide thin films for next-generation flexible and wearable electronics.
Figures are computed from collected data and may differ slightly.
Abstract Homogeneous plasticity in metallic glasses is generally only observed at high temperatures or in very small structures (less than ≈100 nm), so their applications for structural performance have been very limited. Here, nanolaminates with alternating layers of Cu 50 Zr 50 metallic glass and nanocrystalline Cu are synthesized and it is found that samples with an optimal composition of 112‐nm‐thick metallic‐glass layers and 16‐nm‐thick Cu layers demonstrate a maximum strength of 2.513 GPa,
We report the deformation behavior of single crystalline molybdenum nanopillars in uniaxial compression, which exhibits a strong size effect called the “smaller is stronger” phenomenon. We show that higher strengths arise from the increase in the yield strength rather than through postyield strain hardening. We find the yield strength at nanoscale to depend strongly on sample size and not on the initial dislocation density, a finding strikingly different from that of the bulk metal.
Here we demonstrate fully-integrated, bezel-less transistor arrays using stretchable origami substrates and foldable conducting interconnects. Reversible folding of these arrays is enabled by origami substrates which are composed of rigid support fixtures and foldable elastic joints. In addition, hybrid structures of thin metal films and metallic nanowires worked as foldable interconnects which are located on the elastomeric joints.
The mechanical flexibility of perovskite solar cells as well as high power conversion efficiency is attracting increasing attention. In addition to existing empirical approaches, such as cyclic bending tests, in this study we report the tensile properties of the perovskite materials themselves. Measuring the tensile properties of free-standing perovskite materials is critical because (1) tensile properties represent the realistic mechanical properties of the film-type perovskite layer in the sol
Compared with the large plastic deformation observed in ductile metals and organic materials, inorganic semiconductors have limited plasticity (<0.2%) due to their intrinsic bonding characters, restricting their widespread applications in stretchable electronics. Herein, the solution-processed synthesis of ductile α-Ag<sub>2</sub> S thin films and fabrication of all-inorganic, self-powered, and stretchable memory devices, is reported. Molecular Ag<sub>2</sub> S complex solution is synthesized by
Abstract One considerable concern in metallic glass is enhancing ductility by suppressing catastrophic failure by the instantaneous propagation of shear bands. Compressed nanopillars with alternating CuZr metallic glass and polyisoprene nanolaminates exhibit >30% enhancement in plastic flow, as compared with monolithic glass, without sacrifice of strength. A suppression of stochastic strain burst signature in these metallic glass‐polymer composites is reported, which is an undesirable charact
Organic-inorganic hybrid perovskites have been investigated extensively for use in perovskite-based solar cells and light-emitting diodes (LEDs) because of their excellent electrical and optical properties. Although the flexibility of perovskite LEDs has been studied through empirical methods such as cyclic bending tests, the flexibility of the perovskite layer has not been investigated systemically. Here, flexible and semitransparent perovskite LEDs are fabricated: a PEDOT:PSS anode and Ag nano
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