https://scholarworks.unist.ac.kr/handle/201301/97 2026-05-13T13:14:11Z https://scholarworks.unist.ac.kr/handle/201301/91663 Title: Device simulation of ceria-based interfacial switching memristor Author(s): Khot, Sagar; Jung, Dongmyung; Yoon, Tae-Sik; Kwon, Yongwoo Abstract: We present a device simulation on the interfacial switching behavior of ceria (CeO2)-based memristors, considering the migration of oxygen ions and the resulting modulation of Schottky barrier height (SBH). A voltage pulse pulls or pushes oxygen ions depending on its polarity. The SBH can be modulated by the change of the ionic concentration near the contact, which is the mechanism for interfacial switching memristors. A gradual change in conductance can be produced by well-controlled successive pulses, making it suitable for synaptic device applications. Our simulation is composed of two parts. One is calculating the electromigration of oxygen ions to obtain their spatial distribution in the ceria. The other is calculating thermionic current through the SBH to estimate the device's conductance. Our simulation successfully reproduced the previously reported experimental results for the long-term potentiation and depression cycles. We believe that our simulation may provide device engineers with many insights into optimizing the device's performance. 2026-03-31T15:00:00Z https://scholarworks.unist.ac.kr/handle/201301/91661 Title: Role of the orthorhombic phase in endurance degradation of Hf0.5Zr0.5O<hr>memristors Author(s): Park, Jun-Cheol; Seol, WooJun; Baek, Sihyeon; Lee, Donghyeon; Park, Seong Min; Kim, Seon Je; Kim, Young-Min; Jeong, Hu Young; Jo, Ji Young; Lee, Sanghan Abstract: The development of next-generation memory architectures is essential to overcoming limitations of conventional architectures, notably the von Neumann bottleneck. Among emerging technologies, memristors have attracted considerable attention due to their scalability, low power consumption, and neuromorphic potential. However, limited endurance and retention, as well as process-integration constraints, continue to impede practical deployment. HfO2-based memristors are promising due to silicon compatibility and thermal stability, yet switching stability remains a key challenge. Here, we systematically investigate the structural role of the orthorhombic phase in Hf0.5Zr0.5O2 (HZO)-based memristors during the degradation process. Using in situ synchrotron X-ray diffraction (XRD) under an applied electric field, we tracked the field-driven structural evolution over repeated SET/RESET cycles. The orthorhombic phase diffraction intensity progressively decreases and peak broadening increases with cycling, while no distinct shift indicative of a macroscopic phase transition is observed within the experimental resolution. This degradation of crystallinity correlates with the rupture of conductive filaments and eventual device breakdown. These findings highlight the critical role of the orthorhombic phase in both switching behavior and device failure, providing insight into phase-engineered stability in memristive devices. (c) 2026 The Authors. Published by Elsevier B.V. on behalf of The Chinese Ceramic Society. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). 2026-04-30T15:00:00Z https://scholarworks.unist.ac.kr/handle/201301/91637 Title: Epitaxial n-ZnO/MoS2/p-GaN Heterostructure Light-Emitting Diodes Author(s): Rahmatulloh, Imasda; Dalayoan, Daryll J. C.; Ali, Asad; Shin, Soobeom; Nguyen, Anh T. D.; Kwon, Taenam; Behera, Satyabrat; Lee, Jaehyun; Kim, Heekyeong; Jeong, Hu Young; Namgung, Seon; Yi, Gyu-Chul; Chung, Kunook Abstract: We investigated an epitaxial strategy for fabricating MoS2 light-emitting diodes (LEDs). A full-coverage MoS2 active layer was grown on p-type GaN, and n-type ZnO nanorods were then vertically aligned on the MoS2 to form a p-n junction with negligible damage to the MoS2. All materials have nearly matched hexagonal structures, enabling single-crystal alignment. Although the continuous MoS2 film formed multiple layers (MLs), the ZnO/MoS2/GaN heterostructure yielded favorable optical characteristics of the ML-MoS2, including internal quantum efficiency comparable to that of the single-layer MoS2. The ZnO/MoS2/GaN LED exhibited stable A and B exciton emissions, which imply direct bandgap transition with spin-orbit coupling. Without mechanically exfoliated or transferred 2D films, this epitaxial approach satisfies the key requirements for fabricating 2D-based optoelectronic and quantum light sources. The strength of epitaxy, such as large-scale scalability and multiple quantum-well formation, will further advance 2D optoelectronics, making them more practical and efficient. 2026-03-31T15:00:00Z https://scholarworks.unist.ac.kr/handle/201301/91628 Title: Ballistic transport in nanodevices based on single-crystalline Cu thin films Author(s): Cho, Yongjin; Kim, Su Jae; Jung, Min-Hyoung; Lee, Yousil; Jeong, Hu Young; Kim, Young-Min; Lee, Hu-Jong; Kim, Seong-Gon; Jeong, Se-Young; Lee, Gil-Ho Abstract: In ballistic transport, the movement of charged carriers remains unimpeded by scattering events. In this limit, microscopic parameters such as crystal momentum, spin and quantum phase are well conserved, allowing electrons to maintain their quantum coherence over longer distances. Nanoscale materials, such as carbon nanotubes, graphene, and nanowires, can exhibit ballistic transport. However, their scalability in devices is significantly limited. While deposited metal films offer scalability for nanodevices, their short electronic mean free paths hinder ballistic transport. In this study, we investigated the electronic transport in cross-geometry devices fabricated with 90-nm-thick Cu films without grain boundaries. We demonstrated ballistic transport in devices with channel widths of 150 nm at temperatures below 85 K via negative bend resistance measurements. Our findings establish a scalable platform for exploring the intrinsic quantum mechanical properties of Cu, advancing both the fundamental understanding of quantum transport in metals and its practical applications in next-generation electronic quantum technologies. 2026-02-28T15:00:00Z