Browsing by Author "Chen, Y. Y."

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Anisotropic Magnetism and Magnetoresistance in Iron Nanowire Arrays
(2009-12-01)
Ou, M. N.
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Yang, T. J.
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Chen, Y. Y.
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電子物理學系
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Department of Electrophysics
Highly ordered ferromagnetic iron nanowire (Fe NW) arrays with diameters of about 60 nm and 200 nm were fabricated by electro-chemical deposition into anodic aluminum oxide (AAO) templates. The magnetization measurements show the 60 nm NWs as having a larger anisotropic magnetization. This result was illustrated by the magnetic easy axis and preferred crystal orientation of [110] along with the longitudinal direction of the NWs, revealed by the X-ray diffraction (XRD) patterns. The obtained quadratic magnetic field dependence of the normalized magnetoresistance (MR) at low field for both 60 and 200 nm NWs is attributed to the anisotropic magnetoresistance in low-dimensional systems. Furthermore, the enhanced AIR, observed in the 60 nm NWs is attributed to additional spin-diffusion mechanisms.
Characterization of inter-poly high-kappa dielectrics for next generation stacked-gate flash memories
(2006)
Chen, Y. Y.
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Li, T. H.
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Kin, K. T.
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Chien, C. H.
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Lou, J. C.
In this paper, the inter-poly dielectric (IPD) thickness, scaling, and reliability characteristics of Al2O3 and HfO2 IPDs are studied, which are then compared with TEOS IPD. Regardless of deposition tools, drastically leakage current reduction and reliability improvements have been demonstrated by replacing TEOS IPD with high-permittivity (high-kappa) IPDs, which are suitable for mass production applications in the future. Moreover, MOCVD deposition can be used to further promote dielectric reliability when compared to reactive-sputtering deposition. By using MOCVD deposition, the QRD can be significantly improved, in addition to reduced leakage current density, enhanced breakdown voltage and effective breakdown field. Our results clearly demonstrate that both MOCVD-Al2O3 and MOCVD-HfO2 IPD possess great potential for next generation stacked-gate flash memories.
Dielectric properties of nitric oxide-annealed gate oxides grown on nitrogen-implanted silicon substrates
(2006-08-14)
Chen, Y. Y.
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Chien, C. H.
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Lou, J. C.
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
The characteristics of nitric oxide (NO)-annealed nitrided gate oxides grown on nitrogen-implanted silicon substrates (NIS) were studied in this paper. It was found that nitrogen accumulation occurred near the interface after NO-annealing, while NIS-grown nitrided oxide produced a uniform nitrogen distribution in the dielectric bulk. Moreover, it was found that the dielectric reliability is strongly dependent on the dosages used for NIS preparation. NIS with dosages smaller than 10(14) cm(-2) was found not to suppress the oxidation rate and to degrade the dielectric reliability. On the other hand, the samples with a dosage of 10(15) cm(-2) not only exhibited a significantly reduced oxidation rate, making it suitable for growing oxides of multiple thicknesses in sub-3 nm technologies meeting the Systems on Chip requirement, but also improved the dielectric reliability. NO-annealed NIS-grown nitrided oxides depict superior dielectric reliability and this technique appears to be suitable to replace the traditional SiO2 at 0.13 mu m technology node and beyond. (c) 2006 Elsevier B.V. All rights reserved.
Electrical and thermal transport in single nickel nanowire
(2008-02-11)
Ou, M. N.
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Yang, T. J.
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Harutyunyan, S. R.
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Chen, Y. Y.
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Chen, C. D.
The thermal conductivity and electrical resistivity of a suspended nickel nanowire have been measured for T=15-300 K. The temperature dependence of the thermal conductivity and the Lorenz number strongly differ from the bulk. The comparison of the transports in the Ni nanowire shows, that at temperatures 75 < T < 300 K Wiedemann-Franz (WF) law holds, whereas at temperatures T < 75 K the WF law is violated, indicating that thermal current in this material is suppressed more than electrical current. The results are explained by combined effect of confined dimension, enhanced disorder, and grown contribution of N-processes. (C) 2008 American Institute of Physics.
Imaging cells and sub-cellular structures with ultrahigh resolution full-field X-ray microscopy
(2013-05-01)
Chien, C. C.
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Tseng, P. Y.
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Chen, H. H.
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Hua, T. E.
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Chen, S. T.
Our experimental results demonstrate that full-field hard-X-ray microscopy is finally able to investigate the internal structure of cells in tissues. This result was made possible by three main factors: the use of a coherent (synchrotron) source of X-rays, the exploitation of contrast mechanisms based on the real part of the refractive index and the magnification provided by high-resolution Fresnel zone-plate objectives. We specifically obtained high-quality microradiographs of human and mouse cells with 29 nm Rayleigh spatial resolution and verified that tomographic reconstruction could be implemented with a final resolution level suitable for subcellular features. We also demonstrated that a phase retrieval method based on a wave propagation algorithm could yield good subcellular images starting from a series of defocused microradiographs. The concluding discussion compares cellular and subcellular hard-X-ray microradiology with other techniques and evaluates its potential impact on biomedical research. (C) 2012 Elsevier Inc. All rights reserved.
Investigation of normal and superconducting states in noncentrosymmetric Re24Ti5
(2013-05-01)
Lue, C. S.
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Liu, H. F.
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Kuo, C. N.
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Shih, P. S.
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Lin, J-Y
We report a detailed characterization of the noncentrosymmetric superconductor Re24Ti5 using powder x-ray diffraction (XRD), magnetic susceptibility, electrical resistivity, thermal conductivity, Seebeck coefficient, and specific heat measurements. Rietveld refinement of powder XRD data confirms that Re24Ti5 crystallizes in the alpha-Mn structure. All measured quantities demonstrate a bulk superconducting transition at T-c = 5.8 K. Our low-temperature specific heat data measured down to 0.5 K yield a Sommerfeld coefficient gamma = 111.8 mJ mol(-1) K-2, which implies a high density of states at the Fermi level. Moreover, the electronic specific heat in the superconducting state was found to obey a typical s-wave expression, revealing a single gap Delta/k(B) = 10.6 K. This value gives a ratio of 2D/k(B)T(c) = 3.68, higher than the value of 3.5 predicted from BCS theory. On this basis, we conclude that the noncentrosymmetric Re24Ti5 compound can be characterized as a moderately coupled BCS-type superconductor. Furthermore, the obtained parameters from the present study of Re24Ti5 were compared to those of the isostructural compound Re23.8Nb5.2, indicating the similarity between both systems.
Kondo interactions and magnetic correlations in CePt2 nanocrystals
(2007-04-13)
Chen, Y. Y.
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Huang, P. H.
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Ou, M. N.
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Wang, C. R.
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Yao, Y. D.
The evolution of the Kondo effect and antiferromagnetic (AF) correlations with size reduction in CePt2 nanoparticles (3.1-26 nm) is studied by analysis of the temperature-dependent specific heat and magnetic susceptibility. The AF correlations diminish with size reduction. The Kondo effect predominates at small particle size with trivalent, small Kondo temperature (T-K) magnetic regions coexisting with strongly mixed-valent, large T-K nonmagnetic regions. We discuss the role of structural disorder, background density of states and the electronic quantum size effect on the results.
Novel Design of Interactive Caption and Recognition Postures within the Wearable and Non-Vision System over Wireless Sensor Network
(2010)
Huang, W. T.
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Hung, C. N.
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Tuan, C. C.
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Chen, C. C.
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Chang, Y. J.
In this study, we design and present the novel wearable system with the interactive posture caption and recognition functions based on the non-vision over the ZigBee wireless sensor network (ZigBee-WSN). There are two type sensors, 3-axis accelerometer and clip type, to be employed in our wearable system. These sensors are arranged on user\'s four limbs such that the posture information can be gathered by them. Then, the posture information is transmitted to the data-controlling center over ZigBee-WSN. Finally, this center can analyze and distinguish various postures by our proposed algorithm through the friend user\'s interface to express. Our presented wearable system can distinguish out 28 kinds of hand postures and 13 kinds of leg postures altogether. Moreover, under our presented ZigBee-WSN system with small size, low-power consumption, and high-reliability characteristics, the data-controlling center can simultaneously tele-monitor the real-time body interactive postures of 8 persons, when the transmitting distance is less than 18 M and the package correct transmitted rate is more than 97.5%.
Programming efficiency of stacked-gate flash memories with high-kappa dielectrics
(2006)
Chen, Y. Y.
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Chien, C. H.
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Kin, K. T.
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Lou, J. C.
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電子工程學系及電子研究所
The programming efficiency of high-permittivity (K) inter-poly dielectrics (IPDs) and tunnel dielectrics (TDs) on the stacked-gate flash memory performance is evaluated. By 2D MEDICI simulation, stacked-gate flash memories with high-K IPDs clearly exhibited significant improvement in operation speed over those with conventional oxide/nitride/oxide IPD programmed with either channel Fowler-Nordheim (CFN) or channel hot electron (CHE) injection. Choosing HfO2 as the IPD and using CFN programming scheme, the operating voltage can be reduced by more than 48% under a typical lops programming time. However, the effect of high-kappa TDs was quite different when compared with high-K IPDs. High-kappa TDs were only beneficial for memories programmed with CHE injection instead of CFN tunneling. The operating voltage can be reduced by more than 27% under lops programming time by choosing HfO2 as both the IPD and TD with CHE programming scheme. Due to the contrary improvement in programming schemes, high-kappa IPDs and TDs were suitable for next-generation NAND-and NOR-type stacked-gate flash memories, respectively.
Short-term Travel Time Estimation and Prediction for Long Freeway Corridor using NN and regression
(2012)
Wang, J. Y.
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Wong, K. I.
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Chen, Y. Y.
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運輸與物流管理系註：原交通所+運管所
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Department of Transportation and Logistics Management
Travel time information is a fundamental component in Advanced Traveler Information System. In this paper, we propose a short-term travel time estimation and prediction framework for long freeway corridor, considering measurements from vehicle detectors (VD) and floating car data (FCD). The modeling approach is based on a modified Nearest-Neighborhood (NN) model with threshold and a regression model capturing the within day variations. The advantages are that our approach allows for missing data without the need of data imputation in real-time, and is suitable for travel time prediction of long corridors. The validation analysis using an 88 km long section of freeway shows satisfactory results.
Superconducting transition parameters in aluminum-lithium alloys (0-10 at.% Li)
(2007-05-01)
Ou, M. N.
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Yang, T. J.
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Chen, B. J.
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Chen, Y. Y.
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Ho, J. C.
The superconducting transition temperatures T-C of face-centered cubic Al1-x-Li-x alloys (x = 0-0.10) exhibit a minimum near x = 0.03 (3 at.% Li). The McMillan strong-coupling T, equation yields a similar trend of the electron-phonon coupling constant.. Meanwhile, the density of states at the Fermi level N(0) decreases monotonically with increasing x. It appears that T-C drops initially due to a reduced N(0), which is then overtaken by alloying-enhanced factors of phonon or electron-phonon interaction. (c) 2007 Elsevier Ltd. All rights reserved.
Thermal and electrical transport properties of a single nickel nanowire
(2007-12-01)
Ou, M. N.
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Harutyunyan, S. R.
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Lai, S. J.
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Chen, C. D.
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Yang, T. J.
The thermal conductivity (K), specific heat (C-p) and the resistivity (p) of a single nickel nanowire have been measured in the temperature range from 4 to 300 K by means of the "self heating 3 omega" technique. Starting with a 100 nm nickel film grown on a Si/Si3N4 substrate by thermal evaporation, a suspended nickel nanowire was then fabricated through e-beam lithography and etching processes. The width and length of the wire were determined by scanning electron microscope (SEM) as 180 nm and 35 mu m respectively. At 300 K the thermal conductivity of nanowire is similar to 20% of the bulk, it diminishes to lower value as temperature decreases. The consequence is opposite to that of the bulk and might be explained by the ristriction of mean free paths of electron/phonon-phonon interactions due to the grain boundaries. An enhancement of specific heat similar to 250% of the bulk is also observed. In addition, the resistivity of nanowire at room temperature is about four times larger than that of the bulk. The small relative resistiv-ity ratio (RRR) confirms the polycrystalline characteristic ofthe nanowire.