https://scholar.dgist.ac.kr/handle/20.500.11750/10159 2026-08-05T16:07:31Z https://scholar.dgist.ac.kr/handle/20.500.11750/60551 Title: Intrinsically stretchable large-area pixelated electrochromic displays via direct photopatterning Author(s): Kim, Kang Sik; Eom, Soo Yeon; Yang, Seong Hwan; Jo, Jeong-Wan; Sun, Fayong; Lee, Roun; Jeong, Beomjin; Lee, Myoung-Jae; Kim, Jong-Woong; Kim, Yong-Hoon; Park, Jong S.; Park, Sung Kyu Abstract: Electrochromic displays (ECDs) have gained increasing attention for various stretchable applications, offering voltage-controlled optical modulation with low power consumption. However, realizing ECDs that include stretchability with high-resolution pixelation remains challenging. Here, we present an unprecedented combination of materials and device architectures that enable intrinsically stretchable and highly pixelated ECDs via direct photopatterning. Central to this strategy is a stretchable and photopatternable electrochromic (EC) material, containing acrylate-substituted RGB viologens, that supports direct photopatterning with high mechanical durability. To facilitate more strategic device architecture, a stretchable reactive spacer layer and a pixel-defining layer were introduced, ensuring uniform electrical contact and improving mechanical integrity with minimized crosstalk, respectively. Leveraging the cooperative function of the developed materials and device structures, we implemented a fully stretchable 20 & times; 20 passive matrix ECD (10 cm & times; 10 cm) that exhibits RGB pixelated coloration and maintains stable electrochromic performance under strains up to 30%, with durability sustained over 1500 mechanical cycles. 2026-04-30T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/60468 Title: Energy-efficient reservoir computing with 10 x 10 crossbar array memristor for high performance multitask recognition Author(s): Ghafoor, Faisal; Kim, Honggyun; Zhang, Hui; Ghafoor, Bilal; Lee, Myungjae; Shi, Tuo; Kim, Deok-kee Abstract: Memristors hold significant potential for developing energy-efficient artificial intelligence (AI) hardware through parallel in-memory computing, thereby overcoming the long-standing von Neumann bottleneck. However, their widespread adoption is hindered by pronounced cycle-to-cycle (C2C) and device-to-device (D2D) variability. This study presents a novel approach to addressing key challenges in memristor-based artificial intelligence devices. We developed a 10 x 10 crossbar array of Fe50W50 hybrid nanocomposite memristors, demonstrating forming-free operation, low variability, and high reliability with low power consumption. The devices exhibit forming-free, low-variability, and highly reliable switching with ultra-low power consumption. The aligned grain boundaries within the nanocomposite enable well-controlled filament formation, ensuring consistent resistive switching characteristics. Leveraging these features, a reservoir computing (RC) architecture is implemented, demonstrating robust performance characterized by 4-bit input separability, short-term (fading) memory, and a strong echo-state property. The system achieves outstanding pattern-recognition accuracies of 98.79% for handwritten character recognition, 88.92% for garment classification, and 91.51% for digit recognition, along with 87.82% accuracy in multi-attribute classification and 98.62% in gesture recognition, underscoring its versatility in spatiotemporal processing. This material algorithm co-design framework not only enhances computational efficiency but also addresses core reliability challenges in memristor-based AI systems, paving the way toward scalable and energy-efficient neuromorphic computing architectures. 2025-12-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/60452 Title: The anatomy of magnetic field pulse induced transverse domain wall dynamics Author(s): Cho, Jaehun; Yun, Won Seok; Kim, June-Seo Abstract: The microscopic anatomy of the precessional torque-induced magnetic domain wall racetrack memory is numerically investigated. A systematic analysis is performed to explain the efficiency and limitations of this domain wall motion architecture. A transverse domain wall in an in-plane magnetic nanowire is chosen, and the direction of the applied magnetic field is applied to be perpendicular to the film plane. The domain wall displacement upon the application of an out-of-plane magnetic field pulses is shown to be driven by the precessional torque and subsequently decelerated by the damping torque, causing the domain wall to settle at a specific position. Crucially, a characteristic frequency is exhibited by this domain wall dynamics. After removing the magnetic field, a reverse domain wall dynamics is observed with the same frequency, causing the domain wall to revert to its original position. To realize continuous domain wall motion, a notch structure is introduced, and the depinning field is calculated as a function of the out-of-plane field strength. The analysis reveals that the depinning field decreases linearly as the out-of-plane field strength increases. Finally, the principle of domain wall hopping in a multiple-notched nanowire is verified by the application of sequential out-of-plane field pulses. © The Author(s) 2026. 2026-03-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/60451 Title: Polarity-Programmable Bismuth Oxide Overlayers on Bi(111)/MoS2 Heterostructures via Oxidation and Annealing Author(s): Han, Sang Wook; Yun, Won Seok; Seong, Seungho; Kang, Jeongsoo; Ko, Minji; Ryu, Sunmin; Kim, Yong Soo Abstract: Band-structure engineering in bismuth (Bi) oxides is frequently hampered by their amorphous or poorly ordered nature, which obscures the relationship among stoichiometry, band dispersion, and transport polarity. We find that native BiOx overlayers on epitaxial Bi(111)/MoS2 undergo a reversible n → p → n polarity control of the heterostructure system under controlled air exposure and annealing. As-grown BiOx-rich surfaces are n-type and exhibit a photoluminescence peak at ∼2.1–2.2 eV. Mild air annealing (100 °C, 1 h) of native BiOx overlayers on epitaxial Bi(111)/MoS2 yields a p-type surface with a phase-mixed Bi2O3 (α+β) overlayer, characterized by a highly dispersive Bi–O valence band, and in-situ annealing at 300 °C reduces the thickness of the oxide layer and restores the n-type band alignment governed by the Bi(111)/MoS2 stack. First-principles calculations for hexagonal Bi2O3 monolayers and Bi2O3/Bi(111) heterostructures reveal a transition from a wide-gap, O-2p-dominated oxide to a narrow, Bi-dominated direct gap at Γ, which supports the observed p → n band structure evolution. These findings provide a fundamental mechanism for tuning the polarity and band alignment of Bi-oxide-based interfaces on 2D semiconductors. © 2026 American Chemical Society 2026-04-30T15:00:00Z