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Gate-Insulator-Capacitance-Dependent Field-Effect Mobility in Solution-Processed Oxide Semiconductor Thin-Film Transistors

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ECS Meeting Abstracts 2014年第47期MA2014-02卷

作者： Eungkyu Lee Keon-Hee Lim Si Yun Park Kyongjun Kim Youn Sang Kim Seoul National University The Graduate School of Convergence Science and Technology Program in Nano Science and Technology Advanced Institutes of Convergence Technology

We theoretically and experimentally investigate how the field-effect mobility (MFE) depends on the gate capacitances (CI) in solution-processed oxide semiconductor (OS) thin-film transistors (TFTs). With recently developed solution-based techniques, high quality OS films can be deposited onto flexible substrates at low temperatures, which accelerate applying of flexible, transparent, and ink-jet printable OS TFTs to future mobile display and electronics. Meanwhile, another important issue is to sustainably use of portable devices using integrated OS TFT circuits for a long time. Empirically, Increasing CI has been used to increase the drain current (ID) for high-performance and low-energy consuming OS TFTs, which is based on a theory of conventional metal-oxide-semiconductor field-effect transistors (MOSFETs): ID∝CI. However, it has been observed that incremental features of ID as increasing CI in solution-processed OS TFTs are quite different to that of MOSFETs. It is because disordered metal ions and dense grain boundaries in the solution-processed OSs make MFE depend on total number of accumulated electrons. Thus, MFE relies on CI, and ID cannot be linear relationship to CI. Therefore, grasping the relationship between MFE and CI in theoretical manner is important to realize high-performance, low-operational voltage devices, and it is also useful to design, optimize, and integrate OS TFT circuits. The disordering nature of solution-processed OSs can be classified into nanocrystalline and amorphous states, which are determined by how many numbers of metal ions component are contained. When the number of metal ion component is '1', such as ZnO, InO2, and SnO2, the solution-processed OS films have nanocrystalline phase. As the number of metal ion component is larger than '1'(for example, ZnSnO, InGaZnO, InZnO), the states of the OS films are amorphous. Although electronic properties of both amorphous and nanocrystalline OS films arising from their atomic arrangement

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“Standby” EMT and “immune cell trapping” structure as novel mechanisms for limiting neuronal damage after CNS injury

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Neural Regeneration Research 2014年第23期9卷 2032-2035页

作者： Jong-Ho Cha Kyu-Won Kim SNU-Harvard Neuro Vascular Protection Research Center College of Pharmacy Seoul National University Department of Molecular Medicine and Biopharmaceutical Sciences Graduate School of Convergence Science and Technology and College of Medicine or College of PharmacySeoul National University

The central nervous system （CNS） contains the two most important organs, the brain and spinal cord, for the orchestration of the mental and physical activities of life. Because of its importance, the human body has evolved barrier systems to protect CNS tissue from the external environment. This barrier is a membrane composed of tightly apposed cells and is selectively permeable to specific molecules by way of membrane transporters.

关键词： EMT and immune cell trapping Standby CNS structure as novel mechanisms for limiting neuronal damage after CNS injury cell

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Characteristics of Anodic Aluminum Oxide As Separator for Li Ion Battery

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ECS Meeting Abstracts 2014年第5期MA2014-02卷

作者： Jeeyoung Yoo Yong Keon Ahn Si Yun Park Sanghun Cho Youn Sang Kim Seoul National University Seoul National University The Graduate School of Convergence Science and Technology Program in Nano Science and Technology Advanced Institutes of Convergence Technology

To improve the safety of Li ion battery (LIB) in high energy applications, numerous efforts have been made in terms of choosing materials to be used.[1-2] However, these attempts have been limited by thermal stability and durability of separator including electrolyte. In this study, anodic aluminum oxide (AAO) film was used as a separator in Li ion battery for superior performance over commercialized polyolefin-based separator. The AAO film has been prepared by two-step anodization method which is consisted of etching and anodizing processes. The as-prepared AAO film is around the 20 um thick and they showed perpendicular nanopore arrays having a diameter of 40nm. The porosity of the AAO film is calculated about 58.79 %. [3] That value is higher than that of the commercial separator (55%, celgard 2500) The wettability of the AAO film was analyzed using contact angle measurement with liquid electrolyte (1M of LiPF6 in EC:DMC:DEC=1:1:1 (v/v/v)). The AAO film shows higher wettability with smaller contact angle as value of 0o than commercial separator (36o). Small contact angle means low cell resistance which is suitable for high power LIBs. [3] The test for electrolyte absorbance property of the AAO film was conducted. The electrolyte uptakes of the AAO film and the commercial separator are determined to be 126.88 wt% and 264.28 wt% respectively. [3] The density of the AAO film (3.98g/cm3) is smaller than the commercial separator (14.23g/cm3), so they required less electrolyte to operate LIB. Although less amount of electrolyte is used, the AAO film shows higher ionic conductivity of 2.06 mS/cm with SUS electrode than the commercial separator (0.66 mS/cm). This can be explained by low contact angle, which is agreed with low bulk resistance and higher permittivity of AAO film, it contributes to ionic conductivity. (Dielectric constant of AAO film : 28.59, relative permittivity of commercial separator: 9.06 at 1KHz) The interfacial compatibility of lithium metal with sep

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Material Classification of Multi-energy CT images Using Multiple Discriminant Analysis

Material Classification of Multi-energy CT images Using Mult...

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Annual International Conference of the IEEE Engineering in Medicine and Biology Society

作者： Woo-Jin Lee Dae-Seung Kim Se-Ryong Kang Sang-Yoon Woo Won-Jin Yi Interdisciplinary Program in Radiation Applied Life Science major College of Medicine Seoul National University Dental Research Seoul National University Department of Biomedical Radiation Sciences Graduate School of Convergence Science and Technology Seoul National University Department of Oral and Maxillofacial Radiology School of Dentistry Seoul National University

ISBN: (纸本)9781424479276

Energy resolved photon-counting detectors could achieve more than one spectral measurement. The goal of this study is to investigate, with experiment, the ability to decompose five materials using energy discriminating detectors and multiple discriminant analysis (MDA). A small field-of-view multi-energy CT system was built. Linear attenuation coefficient was considered as features of multiple energy CT. MDA was used to decompose five materials with six measurements of the energy dependent linear attenuation coefficients. The results of the experimental study showed that a CT system based on CdTe detectors with MDA can be used to decompose five materials.

关键词： Materials Computed tomography Detectors X-ray imaging Photonics Attenuation Educational institutions

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Low-frequency wide-band hybrid energy harvester based on piezoelectric and triboelectric mechanism

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science China(Technological sciences) 2013年第8期56卷 1835-1841页

作者： HAN MengDi ZHANG XiaoSheng LIU Wen SUN XuMing PENG XuHua ZHANG HaiXia National Key Laboratory of Science and Technology on Micro/Nano Fabrication Institute of MicroelectronicsPeking University Peking University Shenzhen Graduate School

Recently,hybrid energy harvester has been considered as an attractive potential approach to response the worldwide energy crisis due to the combination of advantages from different harvesting *** this paper,a novel low-frequency wide-band hybrid energy harvester based on piezoelectric and triboelectric mechanism is presented and systematically studied including structural design,fabrication process,working principle simulation and *** a vibrational excitation,the polyvinylidene fluoride(PVDF) cantilevers will vibrate and impact the polydimethylsiloxane(PDMS) film on the substrate,producing a piezoelectric output as well as a triboelectric *** structural parameters of each cantilever are optimized using finite element simulation,and the well-designed PVDF cantilevers with controllable PDMS mass not only reduce the device working frequency but also enlarge the *** a sweep-frequency test,three voltage peaks induced by the piezoelectric part are observed at 15,32.5 and 47.5 Hz,with the value of 320,288 and 264 mV,*** the combined triboelectric part,a 20 V peak-peak voltage is generated at 15 *** electrical driving ability of this hybrid energy harvester also has been demonstrated by lighting up a commercial light emitting diode(LED).

关键词： hybrid energy harvester piezoelectricity triboelectric nanogenerator low-frequency wide-band

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Application of dense nano-thin platinum films for low-temperature solid oxide fuel cells by atomic layer deposition

Application of dense nano-thin platinum films for low-temper...

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作者： Ji, Sanghoon Chang, Ikwhang Cho, Gu Young Lee, Yoon Ho Shim, Joon Hyung Cha, Suk Won Graduate School of Convergence Science and Technology Seoul National University Iui-dong Yeongtong-gu Suwon 443-270 Korea Republic of Department of Mechanical and Aerospace Engineering Seoul National University Daehak-dong Gwanak-gu Seoul 151-742 Korea Republic of Department of Mechanical Engineering Korea University Anam-dong Seongbuk-gu Seoul 136-713 Korea Republic of

nano-thin platinum (Pt) films with a dense microstructure for low-temperature solid oxide fuel cells (LT-SOFCs) were fabricated by atomic layer deposition (ALD) and were characterized in terms of their micro-structural properties and electrochemical performance. Pt thin films with a purity level of ∼99% were achieved by controlling the O2 pulsing time. The agglomeration behavior of the ALD Pt thin films was characterized by the annealing temperature, becoming extremely severe above 550°C. An LT-SOFC with a 25 nm thick dense ALD Pt cathode layer exhibited a peak power density of ∼110 mW/cm2 at 450°C. Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Atomic layer deposition

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Mechanism Analysis of Nonvolatile Graphene Oxide Based Reram with Laterally Structured Device

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ECS Meeting Abstracts 2014年第49期MA2014-02卷

作者： Youngmin Park Jieun Ko Jung Ah Lim Sanghun Cho Jeeyoung Yoo Youn Sang Kim Seoul National University Future Convergence Research Division Korea Institute of Science and Technology Seoul 136–791 Republic of Korea Seoul National University The Graduate School of Convergence Science and Technology Program in Nano Science and Technology

There has been an increase in demand for novel nonvolatile-memory technology for low-power, high speed and high scalability because of development of digital technology. With this background, various types of memory are now enthusiastically developed to overcome the limitations of traditional Si-based memory which is difficulty to miniaturize the device and to advance high performance. Resistive random access memory (ReRAM) is a good candidate for next generation devices due to its high speed, low voltage consumption and high scalability. Recently flexible electronic devices such as wearable electronics and optoelectronics have attracted interest, so flexible ReRAM devices are also required. Metal oxide thin film based memory in ReRAM have hitherto been studied mainly as next generation nonvolatile memory devices and have shown good properties such as retention, endurance, and programming characteristics. However, ReRAM based on metal oxide thin film has limitations of fabrication process for flexible device due to their material properties. ReRAM using graphene oxide (GO) is the most promising candidate for the flexible device due to graphene oxide's great electrical and mechanical properties. Graphene oxide ReRAM can be fabricated at room temperature on flexible substrates where metal oxides cannot be. Despite of its excellent properties, the resistive switching mechanisms remain unclear. It is generally assumed that filamentary theory and oxygen migration theory are the major mechanisms of resistive switching phenomena. In this work, we demonstrate the resistive switching mechanisms of ReRAM with laterally structured devices, which have two-terminal electrodes in the same plane. The laterally structured graphene oxide ReRAM devices are fabricated by simple spin-coating method on silicon dioxide substrates. The aluminum (Al) electrodes are deposited on spin-coated grapheme oxide layer by thermal evaporation as shown in Figure 1a. These Al/GO/Al lateral devices sho

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P-88: Enhancement of Electro-Optic Properties of Optically Isotropic Liquid Crystal Device for Flexible Display

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SID Symposium Digest of Technical Papers 2015年第1期46卷

作者： Eun Jeong Shin Seong Cheol Noh Tae Hyung Kim Jee Hun Kim Prasenjit Nayek Myong-Hoon Lee Min Su Kim Liang-Chy Chien Joun Ho Lee Byeong Koo Kim Seung Hee Lee Applied Materials Institute for BIN convergence Department of BIN Fusion Technology and the Department of Polymer Nano Science and Technology Chonbuk National University Jeonju Jeonbuk 567-756 Korea The Graduate School of Flexible and Printable Electronics Chonbuk National University Jeonju Jeonbuk 567-756 Korea Liquid Crystal Institute Kent State University Kent Ohio 44242 USA Mobile Product Development Department LG Display Co. Gumi Gyungbuk 730-350 Korea

Polymer dispersed nano-sized liquid crystal (LC) composite which is an optically isotropic liquid crystal (OILC) has been investigated looking for its application to flexible liquid crystal displays (LCDs). In the device, nematic LC droplets with its diameter of 242nm are dispersed in polymer matrix so that the LCD has many advantages such as free touch mura, high contrast ratio, rubbing free, wide viewing angle and its phase stability with least hysteresis. However, it needs to overcome high operating voltage and low transmittance. Optimization of LC mixture and controlling ratio of LC and Polymer in the mixture to overcome such barriers are required.

关键词： Optically isotropic liquid crystal high transmittance Flexible display

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Recent advances in parametric neuroreceptor mapping with dynamic PET:basic concepts and graphical analyses

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Neuroscience Bulletin 2014年第5期30卷 733-754页

作者： Seongho Seo Su Jin Kim Dong Soo Lee Jae Sung Lee Department of Nuclear Medicine College of Medicine Department of Brain and Cognitive Sciences College of Natural Sciences institute of Radiation Medicine Medical Research Center Institute of Radiation Medicine Medical Research Center Department of Molecular Medicine and Biopharmaceutical Sciences Graduate School of Convergence Science and Technology Department of Biomedical Sciences College of Medicine Seoul National University

Tracer kinetic modeling in dynamic positron emission tomography （PET） has been widely used to investigate the characteristic distribution patterns or dysfunctions of neuroreceptors in brain diseases. Its practical goal has progressed from regional data quantification to parametric mapping that produces images of kinetic-model parameters by fully exploiting the spatiotemporal information in dynamic PET data. Graphical analysis （GA） is a major parametric mapping technique that is independent on any compartmental model configuration, robust to noise, and computationally efficient. In this paper, we provide an overview of recent advances in the parametric mapping of neuroreceptor binding based on GA methods. The associated basic concepts in tracer kinetic modeling are presented, including commonly-used compartment models and major parameters of interest. Technical details of GA approaches for reversible and irreversible radioligands are described, considering both plasma input and reference tissue input models. Their statistical properties are discussed in view of parametric imaging.

关键词： dynamic positron emission tomography graphical analysis neuroreceptor imaging parametric image tracer kinetic modeling

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Evaluation of porous platinum, nickel, and lanthanum strontium cobaltite as electrode materials for low-temperature solid oxide fuel cells

Evaluation of porous platinum, nickel, and lanthanum stronti...

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作者： Jung, Hojean Bae, Kiho Jang, Dong Young Lee, Yoon Ho Cha, Suk-Won Shim, Joon Hyung School of Mechanical Engineering Korea University 145 Anam-ro Seongbuk-gu Seoul136-713 Korea Republic of 14-5 Hwarang-ro Seongbuk-gu Seoul136-791 Korea Republic of School of Mechanical and Aerospace Engineering Seoul National University 599 Gwanak-ro Gwanak-gu Seoul151-744 Korea Republic of Graduate School of Convergence Science and Technology Seoul National University 864-1 Iui-dong Yeongtong-gu Suwon443-270 Korea Republic of

Porous Pt, Ni, and lanthanum strontium cobaltite (LSC) are evaluated as electrode materials for solid oxide fuel cells at the low temperature range under 500 °C. Porous metal electrodes 150 nm thick are prepared by sputtering. Porous LSC was deposited to a typical thickness of 1.5 μm by pulsed laser deposition as the cathode. In terms of fuel cell performance, we confirm that Pt is the best material for both the cathode and the anode under 400 °C, but LSC outperforms Pt as a cathode at temperatures over 450 °C in our configurations. Porous Ni anode is identified as being less effective than the porous Pt. It is determined that these results are closely related to the differences in electrode performance and to morphological changes during fuel cell operation. © 2014 Hydrogen Energy Publications, LLC.

关键词： Cathodes

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