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result(s) for
"Kang, Minseung"
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Comprehensive Structural and Interfacial Characterization of Laser-Sliced SiC Wafers
by
Cho, Chae-Ryong
,
Lee, Seul
,
Chen, Hong
in
Atomic force microscopy
,
Atomic properties
,
Carrier density
2025
Laser slicing has emerged as a promising low-kerf and low-damage technique for SiC wafer fabrication; however, its effects on the crystal integrity, near-surface modification, and charge-transport properties require further clarification. Here, a heavily N-doped 4° off-axis 4H-SiC wafer was sliced using an ultraviolet (UV) picosecond laser, and both laser-irradiated and laser-sliced surfaces were comprehensively characterized. X-ray diffraction and pole figure measurements confirmed that the 4H stacking sequence and macroscopic crystal orientation were preserved after slicing. Raman spectroscopy, including analysis of the folded transverse-optical and longitudinal-optical phonon–plasmon coupled modes, enabled dielectric function fitting and determination of the plasmon frequency, yielding a free-carrier concentration of ~3.1 × 1018 cm−3. Hall measurements provided consistent carrier density, mobility, and resistivity, demonstrating that the laser slicing process did not degrade bulk electrical properties. Multi-scale Atomic Force Microscopy (AFM), Angle-Resolved X-Ray Photoelectron Spectroscopy (ARXPS), Secondary Ion Mass Spectrometry (SIMS), and Transmission Electron Microscopy (TEM)/Selected Area Electron Diffraction (SAED) analyses revealed the formation of a near-surface thin amorphous/polycrystalline modified layer and an oxygen-rich region, with significantly increased roughness and thicker modified layers on the hilly regions of the sliced surface. These results indicate that UV laser slicing maintains the intrinsic crystalline and electrical properties of 4H-SiC while introducing localized nanoscale surface damage that must be minimized by optimizing the slicing parameters and the subsequent surface-finishing processes.
Journal Article
Super-Fast Sodium Storage Properties of Nitrogen-Doped Graphene-Based Material Synthesized via Arc-Discharge Method
2025
We investigated the electrochemical performance of undoped artificial graphene-based material (UAG) and N-doped graphene-based material (NAG, ~3.5% nitrogen doping), synthesized by the arc-discharge method, for sodium-ion battery anodes. The NAG demonstrated slightly superior fast-charging capability compared to UAG, achieving a specific capacity of 46.8 mAh g−1 at 30 A g−1, compared to UAG’s capacity of 36.7 mAh g−1, representing an enhancement of approximately 28%. It also showed high cycle stability, retaining a capacity of 100 mAh g−1 (retention ratio ~99.9%) after 2500 cycles at 5 A g−1, compared to UAG’s retention of 90 mAh g−1 (retention ratio ~95%). The diffusion behavior of the UAG and NAG samples was significantly higher than that of graphite. The improvement in electrochemical properties is attributed to the successful doping of nitrogen in NAG, which results in enhanced electrical conductivity and structural disordering.
Journal Article
Ternary Content Addressable Memory with In–Ga–Zn–O Thin‐Film Transistor Technology for Enhanced Uniformity and Endurance in Efficient Distance‐Based Algorithm Acceleration
by
Kim, Sangbum
,
Byun, Kanghyeon
,
Kang, Minseung
in
Algorithms
,
Artificial intelligence
,
Associative memory
2025
The growing computation complexity arising from recent advancements in data similarity‐based artificial intelligence and machine learning algorithms has amplified the demand for specialized hardware accelerators, such as ternary content‐addressable memory (TCAM). An InGaZnO (IGZO) thin film transistor (TFT)‐based dynamic random access memory (DRAM) TCAM is employed to accelerate the distance computation between binary vectors. The device offers greater scalability compared to the conventional static random access memory (SRAM) TCAMs, while providing enhanced uniformity and endurance performance relative to nonvolatile memory TCAMs. The fabricated device demonstrates a relaxed refresh rate, all cells retaining over 95% of data after 3 h, and withstands over 109 $\\left(10\\right)^{9}$program‐erase cycles. The feasibility of the suggested IGZO DRAM TCAM for accelerating Hamming distance calculation is further examined through simulations of two distance‐based algorithms, which are few‐shot learning and k‐nearest neighbor search. The accuracy of the algorithm exhibits limited tolerance to device variations, with deterioration for standard deviation surpassing 10%. However, the task performance remains comparable to the ideal level due to the excellent uniformity of the IGZO DRAM TCAM, and its performance can be further enhanced when combined with the hardware‐friendly null encoding method. Ternary content addressable memory based on InGaZnO transistors is fabricated and its performance is evaluated through simulations for various distance‐based computing applications. Due to its high areal density, enhanced switching characteristics, and uniformity compared to other data similarity‐computing hardware candidates, the proposed memory is suitable for accelerating state‐of‐the‐art artificial intelligence or machine learning algorithms.
Journal Article
Comparative Radiologic and Morphologic Analysis of Posterolateral Fusion and Percutaneous Pedicle Screw Fixation for Thoracolumbar Junction Burst Fractures
by
Kang, Minseung
,
Yang, Jae-Hyuk
,
Park, Jae Min
in
Clinical decision making
,
Comparative analysis
,
Comparative studies
2025
Background/Objectives: Thoracolumbar burst fractures often require surgical stabilization. Although posterolateral fusion (PLF) has been traditionally used, percutaneous posterior fixation (PPF) without fusion has emerged as a less invasive alternative. However, comparative data specifically addressing PPF and PLF are limited. This study aimed to compare the radiological and perioperative outcomes of PPF and PLF for thoracolumbar burst fractures. Methods: This retrospective cohort study analyzed 61 patients with T11–L2 burst fractures (PPF, 28; PLF, 33). Radiological parameters included local and global sagittal alignment and vertebral height ratio. Fracture morphology was assessed using a structured grading system based on anterior height ratios. Perioperative variables were also assessed. Statistical significance was set at p < 0.05. Results: PPF demonstrated significant advantages in operative time (160.7 min vs. 205.8 min, p < 0.01) and blood loss (165 cc vs. 317 cc, p < 0.01), with a shorter hospitalization time. PPF achieved outcomes comparable to PLF in global alignment and anterior height restoration. The PLF group showed greater local kyphotic angle correction (−7.77° vs. −1.53°, p = 0.01), whereas the PPF group showed significantly higher postoperative posterior height ratio (p = 0.02). Changes in morphological grades, assessed using the anterior height ratio-based grading system, showed similar patterns of improvement in both groups. All implant removals were performed due to patient-reported discomfort. Conclusions: PPF yielded radiological outcomes comparable to PLF in the treatment of thoracolumbar burst fractures. The use of a morphological grading system provided a structured descriptive tool to evaluate surgical impact, though its utility remains exploratory and requires further validation.
Journal Article
Device‐Algorithm Co‐Optimization for an On‐Chip Trainable Capacitor‐Based Synaptic Device with IGZO TFT and Retention‐Centric Tiki‐Taka Algorithm
by
Lee, Kwang‐Hee
,
Kim, Sangbum
,
Kang, Minil
in
Algorithms
,
device‐algorithm co‐optimization
,
indium gallium zinc oxide thin film transistor (IGZO TFT)
2023
Analog in‐memory computing synaptic devices are widely studied for efficient implementation of deep learning. However, synaptic devices based on resistive memory have difficulties implementing on‐chip training due to the lack of means to control the amount of resistance change and large device variations. To overcome these shortcomings, silicon complementary metal‐oxide semiconductor (Si‐CMOS) and capacitor‐based charge storage synapses are proposed, but it is difficult to obtain sufficient retention time due to Si‐CMOS leakage currents, resulting in a deterioration of training accuracy. Here, a novel 6T1C synaptic device using only n‐type indium gaIlium zinc oxide thin film transistor (IGZO TFT) with low leakage current and a capacitor is proposed, allowing not only linear and symmetric weight update but also sufficient retention time and parallel on‐chip training operations. In addition, an efficient and realistic training algorithm to compensate for any remaining device non‐idealities such as drifting references and long‐term retention loss is proposed, demonstrating the importance of device‐algorithm co‐optimization. A novel 6T1C synaptic device based on indium gallium zinc oxide thin film transistor (IGZO TFT) and capacitor and a novel optimized training algorithm, retention‐centric Tiki‐Taka algorithm, is proposed. Through a new training scheme by co‐optimizing the device and algorithm, modified national institute of standards and technology (MNIST) on‐chip training accuracy of over ≈97% even in wide retention requirements is obtained.
Journal Article
In Situ Electrochemical Impedance Measurements of α-Fe2O3 Nanofibers: Unravelling the Li-Ion Conduction Mechanism in Li-Ion Batteries
2022
Unravelling the lithium-ion transport mechanism in α-Fe2O3 nanofibers through in situ electrochemical impedance studies is crucial for realizing their application in high-performance anodes in lithium-ion batteries. Herein, we report the effect of heat treatment conditions on the structure, composition, morphology, and electrochemical properties of α-Fe2O3 nanofibers as an anode for lithium-ion batteries. The α-Fe2O3 nanofibers were synthesized via electrospinning and post-annealing with differences in their annealing temperature of 300, 500, and 700 °C to produce FO300, FO500, and FO700 nanofibers, respectively. Improved electrochemical performance with a high reversible specific capacity of 599.6 mAh g−1 at a current density of 1 A g−1 was achieved after 50 cycles for FO700. The in situ electrochemical impedance spectroscopy studies conducted during the charge/discharge process revealed that the charge transfer and Li-ion diffusion behaviors were related to the crystallinity and structure of the as-synthesized α-Fe2O3 nanofibers. The surfaces of the α-Fe2O3 nanofibers were converted into Fe metal during the charging/discharging process, which resulted in improved electrical conductivity. The electron lifetime, as determined by the time constant of charge transfer, revealed that, when a conversion reaction occurred, the electrons tended to travel through the iron metal in the α-Fe2O3 nanofibers. The role of iron as a pseudo-resistor with negligible capacitance was revealed by charge transfer resistance analysis.
Journal Article
Non-invasive digital etching of van der Waals semiconductors
2022
The capability to finely tailor material thickness with simultaneous atomic precision and non-invasivity would be useful for constructing quantum platforms and post-Moore microelectronics. However, it remains challenging to attain synchronized controls over tailoring selectivity and precision. Here we report a protocol that allows for non-invasive and atomically digital etching of van der Waals transition-metal dichalcogenides through selective alloying via low-temperature thermal diffusion and subsequent wet etching. The mechanism of selective alloying between sacrifice metal atoms and defective or pristine dichalcogenides is analyzed with high-resolution scanning transmission electron microscopy. Also, the non-invasive nature and atomic level precision of our etching technique are corroborated by consistent spectral, crystallographic, and electrical characterization measurements. The low-temperature charge mobility of as-etched MoS
2
reaches up to 1200 cm
2
V
−1
s
−1
, comparable to that of exfoliated pristine counterparts. The entire protocol represents a highly precise and non-invasive tailoring route for material manipulation.
Here, the authors exploit a non-invasive layer-bylayer etching technique to fabricate electronic devices based on 2D transition metal dichalcogenides with controlled thickness and transport properties comparable to those of exfoliated flakes.
Journal Article
Relationships of Lower Lung Fibrosis, Pleural Disease, and Lung Mass with Occupational, Household, Neighborhood, and Slate Roof-Dense Area Residential Asbestos Exposure
2018
This study aimed to evaluate the relationship between various asbestos exposure routes and asbestos-related disorders (ARDs). The study population comprised 11,186 residents of a metropolitan city who lived near asbestos factories, shipyards, or in slate roof-dense areas. ARDs were determined from chest X-rays indicating lower lung fibrosis (LFF), pleural disease (PD), and lung masses (LMs). Of the subjects, 11.2%, 10.4%, 67.2% and 8.3% were exposed to asbestos via occupational, household, neighborhood, and slate roof routes, respectively. The odds ratio (OR) of PD from household exposure (i.e., living with asbestos-producing workers) was 1.9 (95% confidence interval: 0.9–4.2), and those of LLF and PD from neighborhood exposure, or residing near asbestos factories) for <19 or >20 years, or near a mine, were 4.1 (2.8–5.8) and 4.8 (3.4–6.7), 8.3 (5.5–12.3) and 8.0 (5.5–11.6), and 4.8 (2.7–8.5) and 9.0 (5.6–14.4), respectively. The ORs of LLF, PD, and LM among those residing in slate-dense areas were 5.5 (3.3–9.0), 8.8 (5.6–13.8), and 20.5 (10.4–40.4), respectively. Substantial proportions of citizens residing in industrialized cities have potentially been exposed to asbestos, and various exposure routes are associated with the development of ARDs. Given the limitations of this study, including potential confounders such as socioeconomic status, further research is needed.
Journal Article
Non-invasive digital etching of van der Waals semiconductors
2023
The capability to finely tailor material thickness with simultaneous atomic precision and non-invasivity would be useful for constructing quantum platforms and post-Moore microelectronics. However, it remains challenging to attain synchronized controls over tailoring selectivity and precision. Here we report a protocol that allows for non-invasive and atomically digital etching of van der Waals transition-metal dichalcogenides through selective alloying via low-temperature thermal diffusion and subsequent wet etching. The mechanism of selective alloying between sacrifice metal atoms and defective or pristine dichalcogenides is analyzed with high-resolution scanning transmission electron microscopy. Also, the non-invasive nature and atomic level precision of our etching technique are corroborated by consistent spectral, crystallographic and electrical characterization measurements. The low-temperature charge mobility of as-etched MoS\\(_2\\) reaches up to \\(1200\\,\\)cm\\(^{2}\\cdot\\)V\\(^{-1}\\cdot\\)s\\(^{-1}\\), comparable to that of exfoliated pristine counterparts. The entire protocol represents a highly precise and non-invasive tailoring route for material manipulation.
Non-invasive digital etching of van der Waals semiconductors
2023
The capability to finely tailor material thickness with simultaneous atomic precision and non-invasivity would be useful for constructing quantum platforms and post-Moore microelectronics. However, it remains challenging to attain synchronized controls over tailoring selectivity and precision. Here we report a protocol that allows for non-invasive and atomically digital etching of van der Waals transition-metal dichalcogenides through selective alloying via low-temperature thermal diffusion and subsequent wet etching. The mechanism of selective alloying between sacrifice metal atoms and defective or pristine dichalcogenides is analyzed with high-resolution scanning transmission electron microscopy. Also, the non-invasive nature and atomic level precision of our etching technique are corroborated by consistent spectral, crystallographic and electrical characterization measurements. The low-temperature charge mobility of as-etched MoS2 reaches up to 1200 cm2V-1s-1, comparable to that of exfoliated pristine counterparts. The entire protocol represents a highly precise and non-invasive tailoring route for material manipulation.
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