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Two distinct topological phases in the mixed-valence compound YbB6 and its differences from SmB6

Physical Review B 2015年第15期91卷 155151-155151页

作者： Tay-Rong Chang Tanmoy Das Peng-Jen Chen Madhab Neupane Su-Yang Xu M. Zahid Hasan Hsin Lin Horng-Tay Jeng A. Bansil Department of Physics National Tsing Hua University Hsinchu 30013 Taiwan Centre for Advanced 2D Materials and Graphene Research Centre National University of Singapore Singapore 117546 Department of Physics National University of Singapore Singapore 117542 Department of Physics National Taiwan University Taipei 10617 Taiwan Nano Science and Technology Program Taiwan International Graduate Program Academia Sinica Taipei 11529 Taiwan and National Taiwan University Taipei 10617 Taiwan Institute of Physics Academia Sinica Taipei 11529 Taiwan Joseph Henry Laboratory and Department of Physics Princeton University Princeton New Jersey 08544 USA Department of Physics Northeastern University Boston Massachusetts 02115 USA

We discuss the evolution of topological states and their orbital textures in the mixed-valence compounds SmB6 and YbB6 within the framework of the generalized gradient approximation plus onsite Coulomb interaction (GGA + U) scheme for a wide range of values of U. In SmB6, the topological Kondo insulator (TKI) gap is found to be insensitive to the value of U, but in sharp contrast, Kondo physics in isostructural YbB6 displays a surprising sensitivity to U. In particular, as U is increased in YbB6, the correlated TKI state in the weak-coupling regime transforms into a d−p-type topological insulator phase with a band inversion between Yb-5d and B-2p orbitals in the intermediate coupling range, without closing the insulating energy gap throughout this process. Our theoretical predictions related to the TKI and non-TKI phases in SmB6 and YbB6 are in substantial accord with recent angle-resolved photoemission spectroscopy experiments.

关键词： TOPOLOGICAL insulators VALENCE (Chemistry) YTTERBIUM compounds KONDO effect PHOTOELECTRON spectroscopy

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Time-dependent effect of combination therapy with erythropoietin and granulocyte colony-stimulating factor in a mouse model of hypoxic-ischemic brain injury

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Neuroscience Bulletin 2014年第1期30卷 107-117页

作者： Ji Hea Yu Jung Hwa Seo Jong Eun Lee Ji Hoe Heo Sung-Rae Cho Department and Research Institute of Rehabilitation Medicine Yonsei University College of Medicine Brain Korea 21 PLUS Project for Medical Science Yonsei University Graduate Program of Nano Science and Technology Yonsei University Department of Anatomy Yonsei University College of Medicine Department of Neurology Yonsei University College of Medicine Yonsei Stem Cell Center Avison Biomedical Research CenterYonsei University College of Medicine Rehabilitation Institute of Neuromuscular Disease Yonsei University College of Medicine

Erythropoietin （EPO） and granulocyte colony- stimulating factor （G-CSF） are likely to play broad roles in the brain. We investigated the effects of combination therapy with EPO and G-CSF in hypoxic- ischemic brain injury during the acute, subacute, and chronic phases. A total of 79 C57BL/6 mice with hypoxic-ischemic brain injury were randomly assigned acute （days 1-5）, subacute （days 11-15）and chronic （days 28-32） groups. All of them were treated with G-CSF （250 μg/kg） and EPO （5 000 U/kg） or saline daily for 5 consecutive days. Behavioral assessments and immunohistochemistry for angiogenesis, neuro- genesis, and astrogliosis were performed with an 8-week follow-up. Hypoxia-inducible factor-1 （HIF-1） was also measured by Western blot analysis. The results showed that the combination therapy with EPO and G-CSF in the acute phase significantly improved rotarod performance and forelimb-use symmetry compared to the other groups, while subacute EPO and G-CSF therapy exhibited a modest improvement compared with the chronic saline controls. The acute treatment significantly increased the density of CD31^＋（PECAM-1） and a-smooth muscle actin^＋ vessels in the frontal cortex and striatum, increased BrdU^＋/PSA- NCAM^＋ neurogenesis in the subventricular zone, and decreased astroglial density in the striatum. Furthermore, acute treatment significantly increased the HIF-1 expression in the cytosol and nucleus, whereas chronic treatment did not change the HIF-1 expression, consistent with the behavioral outcomes. These results indicate that the induction of HIF-1 expression by combination therapy with EPO and G-CSF synergistically enhances not only behavioral function but also neurogenesis and angiogenesis while decreasing the astroglial response in a time- dependent manner.

关键词： erythropoietin granulocyte colony-stimulating factor hypoxia-inducible factor-1 hypoxic-ischemic brain injury

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Solution- Processed Alkali Metals-Doped Amorphous Zinc Tin Oxide Thin-Film Transistors and Analysis of Alkali Metal Doping Mechanism through the UV-Visible Spectroscopic

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ECS Meeting Abstracts 2014年第47期MA2014-02卷

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

Recently, alkali metal doped ZnO has received much positive attention owing to its high performance and good electrical stability. In particular, since alkali metals such as Li and Na are general elements and show good potential as doping elements in ZnO semiconductors, several researchers have been interested in alkali metal doping process of polycrystalline zinc oxide semiconductors. However, only a few studies have been reported the doping mechanism to enhance the mobility. In addition, there have been few studies on alkali metal doping mechanism in amorphous metal oxide semiconductors. Most studies about alkali metal doped oxide semiconductor have been inquired in term of crystallinity, oxygen vacancy, and surface morphology properties. For these reasons, we also studied the mechanism of alkali metal doping in view of oxygen vacancy by spectroscopic study using XPS and surface morphology using AFM. However, although we observed that oxygen vacancy contents are reduced slightly with a correlation by interstitial or substitutional mechanism, it seems to be difficult to identify the correlation between the enhancement of electrical properties induced by interstitial doping and the changes of oxygen vacancy contents, because the difference of XPS spectra in doped ZTO films is too small. Also, as the decrease of oxygen vacancy contents means the decrease of electron mobility in metal oxide semiconductors, the tendency of oxygen vacancy spectra in XPS is inconsistence with general phenomena. It means that other mechanisms are required to precisely explain the electrical properties of the doped amorphous ZTO TFTs related to alkali metal doping mechanism. Otherwise, the change in the optical band gap supported by the Burstein-moss theory showed successfully that the enhancement of mobility was related to the interstitial doping of alkali metals. This result shows that the change of the optical band gap clearly applied to the study of the relationship between the change

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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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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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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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Oxidative Stable Cu 3 Sn nanoparticles for Novel Electrode Fabrication Using Pressure Under Ambient Condition

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ECS Meeting Abstracts 2014年第49期MA2014-02卷

作者： Sanghun Cho Keon-Hee Lim Jeeyoung Yoo Si Yun Park Youngmin Park Youn Sang Kim Seoul National University Seoul National University The Graduate School of Convergence Science and Technology Program in Nano Science and Technology 864-1 Iui-dong Yeongtong-gu Suwon-si Gyeonggi-do Korea

Manufacturing methods of conductive electrode is essential technology for printable electronics such as radio frequency identification tags (RFID), thin film transistor (TFT), ultra high frequency antennas and solar cell. Various fabrication methods of electrodes for printable electronics have been suggested to screen printing, gravure printing and inkjet printing. However, these methods have difficulties to the control of printing pressure, thickness, nozzle blocking, viscosity of ink and coffee ring effect. New technique for electrode for printable electronics needs to perform at room temperature and ambient condition. In addition, copper nanoparticles are good prospective candidate to replace high cost silver because of low-cost, abundant deposit and high conductivity. However, copper nanoparticles have the limitation which is highly oxidative materials and these drawbacks limited practical printing process. To overcome these limitations, conductive materials for electrodes requires high oxidative stable nanoparticles and low cost materials. In this study, we synthesized high oxidative stable, conductive Cu3Sn nanoparticles and fabricated electrode by pressure assisted method at room temperature and ambient condition. Prepared Cu3Sn nanoparticles were confirmed using X-ray diffraction (XRD) and Energy Dispersive X-ray Spectrum (EDS) with High Angle Annular Dark-Field Scanning TEM (HAADF-STEM). Measurement of electrical conductivity was carried out with the 4-point probe methods depending on various value of pressure. The conductive electrodes were obtained by pressure at 530MPa and showed electrical resistivity of less than 19.8 µΩ cm. Electrical resistivity of fabricated electrodes is similar to that of bulk Cu3Sn material (8.8. µΩ•cm). This result is caused by numerous and three dimensional contact of each conductive nanoparticle. To investigate the contact of each nanoparticle, Cross-sectional TEM analysis of pressed nanoparticles was performed. Also, we analy

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Light scattering from coupled plasmonic nanospheres on a stretchable substrate for application as a biosensor or mechanical sensor

Light scattering from coupled plasmonic nanospheres on a str...

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2013 3rd International Conference on Advanced Materials and Information technology Processing (AMITP 2013)

作者： Huai-Yi Xie Mohammad Tariq Yaseen Rakesh Singh Moirangthem Yia-Chung Chang Research Centre for Applied Sciences Academia Sinica Nano Science and Technology Program Taiwan International Graduate ProgramAcademia Sinica Department of Engineering and System Science NTHU Max-Planck-Institut fur Eisenforschung

ISBN: (纸本)9781845648534

The ellipsometric spectra(Ψ and ?) of coupled metallic nanoparticles on a stretchable substrate have been studied via the spherical-harmonics based Green's function *** use Au trimmer nanoparticles and dielectric *** calculated ellipsometric spectra show a plasmonic resonance peak with asymmetric *** a trimmer of metallic nanoparticles on a stretchable substrate,the separation between nanoparticles in the trimmer can be varied by the applied mechanical *** find that both the plasmonic resonance peak position and the signal strength at the resonance frequency are sensitive to the gap distance in the trimmer,which can be controlled by the stretchable *** simulation results indicate that the sensitivity of the plasmonic resonance lineshape to the inter-particle distance allows this coupled nanoparticle system to be used as a biosensor or mechanical *** experimental ellipsometric spectra for closely-spaced metallic nanoparticles on a PDMS substrate are also reported.

关键词： stretchable material optical metrology scattering theory

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Erratum to novel MRI contrast development by lock-in suppression (Magn Reson Med 2014;71:1676–1681)

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Magnetic Resonance in Medicine 2014年第5期72卷

作者： Yu-Wen Chen Chao-Hsiung Hsu Dennis W. Hwang Department of Chemistry and Biochemistry National Chung Cheng University Min-Hsiung Township Chiayi Taiwan These authors contributed equally to this work Molecular Science and Technology Program Taiwan International Graduate Program Institute of Atomic and Molecular Sciences Academia Sinica Taipei Taiwan Department of Chemistry National Tsing-Hua University Hsinchu Taiwan Center for Nano Bio-detection AIM-HI National Chung Cheng University Min-Hsiung Township Chiayi Taiwan

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Cross-plane Seebeck coefficient and thermal conductivity of CuFeSe2 thin film

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AIP Conference Proceedings 2012年第1期1449卷 405-408页

作者： P. C. Lee M. N. Ou J. Y. Luo M. K. Wu Y. Y. Chen Department of Engineering and System Science National TsingHua University Hsinchu Taiwan 30013 R.O.C. and Nano Science and Technology Program Taiwan International Graduate Program Institute of Taiwan Institute of Physics Academia Sinica 128 Academia Road Sec. 2. Nankang Taipei 115 Taiwan

The CuFeSe2 is a member of the I-III-VI2 semiconductors, whereas it shows different physical properties from the chalcopyrite family, include the tetragonal structure, the small band gap ∼0.16 eV and the weak magnetic behavior. Only a few articles focused on this material in recent years. The measurements of the Seebeck coefficient and thermal conductivity of the high quality CuFeSe2 thin film could provide valuable information for its thermal application. In this report, a CuFeSe2 thin film with thickness ∼200 nm on SiO2/Si substrate was prepared by pulse laser deposition (PLD). The highly crystallized film shows a preferred orientation (h 0 0) normal to the film surface. Two pairs of heater/sensor Au strips were thermally deposited on the thin film and substrate separately for thermal conductivity measurement using differential 3ω method. The Seebeck coefficient across the film plane was directly measured by two additional EMF probes below and above the film with temperature gradient generated by heater/sensor at frequency 2ω. The temperature dependence of thermal conductivity and Seebeck coefficient were measured in a wide temperature range from 150 to 300 K. The room-temperature thermal conductivity and Seebeck coefficient are obtained to be 3.5 W/m-K and −108 μV/K respectively.

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