Publications by authors named "Sung Jin An"

We report tellurium (Te) thin-film-based artificial photonic synapses and their application to physical reservoir computing (PRC). The Te-based artificial photonic synapses were fabricated by using sputtered Te thin films and spray-coated MXene (TiC) electrodes. A thorough investigation of the field-dependent persistent photoconductivity (PPC) of the Te channel revealed that the relaxation speed of the transient photocurrent depended on the gate bias.

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In recent years, there has been growing interest in the development of metal-free, environmentally friendly, and cost-effective biopolymer-based piezoelectric strain sensors (bio-PSSs) for flexible applications. In this study, we have developed a bio-PSS based on pure deoxyribonucleic acid (DNA) and curcumin materials in a thin-film form and studied its strain-induced current-voltage characteristics based on piezoelectric phenomena. The bio-PSS exhibited flexibility under varying compressive and tensile loads.

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It is essential to understand the barrier height, ideality factor, and role of inhomogeneities at the metal/semiconductor interfaces in nanowires for the development of next generation nanoscale devices. Here, we investigate the drain current ()-gate voltage () characteristics of GaN nanowire wrap-gate transistors (WGTs) for various gate potentials in the wide temperature range of 130-310 K. An anomalous reduction in the experimental barrier height and rise in the ideality factor with reducing the temperature have been perceived.

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We used capacitance-voltage (-), conductance-voltage (-), and noise measurements to examine the carrier trap mechanisms at the surface/core of an AlGaN/GaN nanowire wrap-gate transistor (WGT). When the frequency is increased, the predicted surface trap density promptly drops, with values ranging from 9.1 × 10 eV∙cm at 1 kHz to 1.

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For the creation of next-generation nanoscale devices, it is crucial to comprehend the carrier transport mechanisms in nanowires. Here, we examine how temperature affects the properties of GaN nanowire wrap-gate transistors (WGTs), which are made via a top-down technique. The predicted conductance in this transistor remains essentially unaltered up to a temperature of 240 K and then increases after that as the temperature rises.

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Graphene oxide (GO) is one of the interesting ink materials owing to its fascinating properties, such as high dissolubility in water and high controllable electric properties. For versatile printing application, the viscosity of GO colloids should be controlled in order to meet the specific process requirements. Here, we report on the relatively rapid fabrication of viscosity-increased GO (VIGO) colloids mixed with electrophoretically deposited GO sheets (EPD-GO).

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We compare the adiabatic quantized charge pumping performed in two types of InAs nanowire double quantum dots (DQDs), either with tunnel barriers defined by closely spaced narrow bottom gates, or by well-separated side gates. In the device with an array of bottom gates of 100 nm pitch and 10 μm lengths, the pump current is quantized only up to frequencies of a few MHz due to the strong capacitive coupling between the bottom gates. In contrast, in devices with well-separated side gates with reduced mutual gate capacitances, we find well-defined pump currents up to 30 MHz.

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We fabricated and characterized AlGaN/GaN high-electron mobility transistors (HEMTs) with a nano-sized in situ cap layer (one is a silicon carbon nitride (SiCN) layer, and the other is a silicon nitride (SiN) layer) comparing to the conventional device without an in situ cap layer. The pulse characteristics and noise behaviors for two devices with in situ cap layers are much superior to those of the reference device without a cap layer, which means that the in situ cap layer effectively passivates the AlGaN surface. On the other hand, the device with an in situ SiCN cap layer showed the excellent device characteristics and noise performances compared to the other devices because of the reduced positive ionic charges and enhanced surface morphology caused by carbon (C) surfactant atoms during the growth of the SiCN cap layer.

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Replantation of multilevel amputation of the hand requires considerable hospital resources, and the surgical outcomes in older adults have not been described in detail. Thus, replantation for this injury was mostly confined to young patients. Here, we describe the case of a 63-year-old patient with multilevel amputation of the hand in whom replantation surgery was successful with grasp and pinch functions by the last follow-up.

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Article Synopsis
  • Thermal properties like conductivity, heat capacity, and melting temperature are crucial for the performance of 2D materials, but existing research on these properties is limited, especially regarding melting temperatures.
  • The study investigated the melting temperature of 2D Tellurium (2D Te) using nano-thermal analysis and uncovered unusual behavior prior to melting.
  • The findings suggest that defects in 2D Te contribute to surface pre-melting, which could enhance practical applications by providing insights into its surface characteristics.
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The bottom-up synthesis process often allows the growth of metastable phase nanowires instead of the thermodynamically stable phase. Herein, we synthesized CdAs nanowires with a controlled three-dimensional Dirac semimetal phase using a chemical vapor transport method. Three different phases such as the body centered tetragonal (bct), and two metastable primitive tetragonal (4/ and 4/) phases were identified.

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We investigate the DC, , and pulse performances in GaN-based nanowire gate-all-around (GAA) transistors with two kinds of geometry: one is AlGaN/GaN heterostructure with two dimensional electron gas (2DEG) channel and the other is only GaN layer without 2DEG channel. From and curves, the fabricated GaN nanowire GAA transistor with AlGaN layer clearly exhibits normally-on operation with negative threshold voltage () due to the existence of 2DEG channel on the trapezoidal shaped GaN nanowire. On the other hand, the GaN nanowire GAA transistor without AlGaN layer presents a positive (normally-off operation) due to the absent of 2DEG channel on the triangle shaped GaN nanowire.

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We demonstrate a controllable p-n junction in a three-dimensional Dirac semimetal (DSM) CdAs nanowire with two recessed bottom gates. The device exhibits four different conductance regimes with gate voltages, the unipolar (n-n and p-p) and bipolar (n-p and n-p) regimes, where p-n junctions are formed. The conductance in the p-n junction regimes decreases drastically when a magnetic field is applied perpendicular to the nanowire.

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The broadband light emission in low-dimensional organic lead halide perovskites (OHPs) is a fascinating property for white light-emitting diodes (LEDs). However, unique emission has been observed in highly distorted low-dimensional OHPs such as (110) and (111) perovskites. Herein, we report the first observation of white-light emission under ambient (21 °C) conditions in a rectangular microsheet of (CHNH)PbBr, a (100) perovskite.

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A low-cost and eco-friendly die attach process for high temperatures should be developed owing to the expansion of the field of high-temperature applications, such as high-power and high-frequency semiconductors. Pb-based and Au-based systems have been used as conventional die attach materials for high-temperature devices. However, these materials exhibit environmental problems and are expensive.

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Thin layer two-dimensional (2-D) transition metal dichalcogenide (TMD) materials have distinctive optoelectronic properties. Therefore, several methods including mechanical exfoliation, chemical vapor deposition, and liquid-phase exfoliation have been attempted to obtain uniform TMDs. However, such methods do not easily produce high-quality few-layer TMDs with high speed.

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Thin-film transistors (TFTs) have received great attention for their use in lightweight, large area, and wearable devices. However, low crystalline materials and inhomogeneous film formation limit the realization of high-quality electrical properties for channels in commercial TFTs, especially for flexible electronics. Here, we report a field-effect TFT fabricated via cross-linking of edge-1T basal-2H MoS sheets that are prepared by edge functional exfoliation of bulk MoS with soft organic exfoliation reagents.

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Objective: To evaluate the reliability and validity of an adapted Korean version of the Spinal Appearance Questionnaire (SAQ).

Methods: Translation/retranslation of the English version of the SAQ was conducted, and all steps of the cross-cultural adaptation process were performed. The Korean version of the SAQ (K-SAQ) and the previously validated appearance domain of the Korean version of the Scoliosis Research Society-22 Outcomes questionnaire (K-SRS-22) were mailed to 160 patients with adolescent idiopathic scoliosis (AIS).

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Background: Severe forefoot deformities, particularly those involving the dorsum of the foot, cause inconvenience in daily activities of living including moderate pain on the dorsal aspect of the contracted foot while walking and difficulty in wearing nonsupportive shoes due to toe contractures. This paper presents clinical results of reconstruction of severe forefoot deformity using the anterolateral thigh (ALT) free flap.

Methods: Severe forefoot deformities were reconstructed using ALT flaps in 7 patients (8 cases) between March 2012 and December 2015.

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We present a novel metal-insulator-semiconductor (MIS) diode consisting of graphene, hexagonal BN, and monolayer MoS2 for application in ultrathin nanoelectronics. The MIS heterojunction structure was fabricated by vertically stacking layered materials using a simple wet chemical transfer method. The stacking of each layer was confirmed by confocal scanning Raman spectroscopy and device performance was evaluated using current versus voltage (I-V) and photocurrent measurements.

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We propose a semiconductor-insulator-semiconductor (SIS) heterojunction diode consisting of monolayer (1-L) MoS2, hexagonal boron nitride (h-BN), and epitaxial p-GaN that can be applied to high-performance nanoscale optoelectronics. The layered materials of 1-L MoS2 and h-BN, grown by chemical vapor deposition, were vertically stacked by a wet-transfer method on a p-GaN layer. The final structure was verified by confocal photoluminescence and Raman spectroscopy.

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A MoSe2 p-n diode with a van der Waals homojunction is demonstrated by stacking undoped (n-type) and Nb-doped (p-type) semiconducting MoSe2 synthesized by chemical vapor transport for Nb substitutional doping. The p-n diode reveals an ideality factor of ≈1.0 and a high external quantum efficiency (≈52%), which increases in response to light intensity due to the negligible recombination rate at the clean homojunction interface.

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Introduction: Little data is available on the relationship between sagittal spinopelvic parameters and health related quality of life (HRQOL) in osteoporotic patients. The aim of this study was to identify relationships between spinopelvic parameters and HRQOL in osteoporosis.

Material And Methods: The patient and control groups comprised 138 osteoporotic patients and 40 controls.

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We report the synthesis of centimeter-scale, uniform 1T'- and 2H-MoTe2 thin films via the tellurization of Mo thin films. 1T'-MoTe2 was initially grown and converted gradually to 2H-MoTe2 over a prolonged growth time under a Te atmosphere. Maintaining excessive Te was essential for obtaining the stable stoichiometric 2H-MoTe2 phase.

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Purpose: The aim of this study was to analyze the factors affecting the outcomes after surgical treatment of acetabular fractures.

Materials And Methods: Between January 2000 and December 2012, 106 patients with acetabular fractures were treated with open reduction and internal fixation. We performed a retrospective cohort study to analyze the factors which may influence a patient's prognosis after surgical treatment of an acetabular fracture.

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