Yonhua Tzeng

National Cheng Kung University, 臺南市, Taiwan, Taiwan

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Publications (81)189.07 Total impact

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    ABSTRACT: We propose a simple system to investigate the influence of microstructure on the resistive switching behavior via bi-crystal CuO nanowires. CuO nanowires are prepared by thermally oxidizing transmission electron microscopy copper grids in air. Single-crystal and bi-crystal CuO nanowires can be selectively obtained by adjusting the temperature. The devices made of single-crystal nanowires follow Ohm's law, with a high resistance, within the sweeping voltage range of 0-4 V, whereas those made of bi-crystal nanowires exhibit threshold and memory resistive switching behaviors, which are due to the enrichment of copper ions in the grain boundaries of bi-crystal CuO nanowires providing sources for the formation of conductive filaments. Moreover, the bi-crystal nanowires with higher defect densities in grain boundaries result in lower threshold voltages of switching from high to low resistance states. The threshold resistive switching behavior can be turned into memory resistive switching behavior by increasing the thickness of the device electrodes or reducing the compliance current. The endurance of memory resistive switching through the pre-defined conduction paths in the single grain boundaries of bi-crystal CuO nanowires is at least 1000 cycles without any performance deterioration. This high reliability is ascribed to the single conductive filaments.
    Journal of Alloys and Compounds 12/2014; 615:754-760. DOI:10.1016/j.jallcom.2014.05.145 · 3.00 Impact Factor
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    ABSTRACT: Science and technology are presented for novel nitrogen-incorporated ultrananocrystalline diamond (N-UNCD) encapsulated NG/copper anode and UNCD coatings that may enable next generation Li-ion batteries (LIBs) with potential 10x longer lifetime and superior performance than current LIBs. N-UNCD films (∼5-10 nm grain size) exhibit electrical conductivity and extreme resistance to chemical corrosion, providing superior performance with respect to current uncoated anodes.
    Advanced Materials 06/2014; 26(22). DOI:10.1002/adma.201400280 · 17.49 Impact Factor
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    Khalil Amine · Ryoji Kanno · Yonhua Tzeng ·
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    ABSTRACT: This issue contains assessments of battery performance involving complex, interrelated physical and chemical processes between electrode materials and electrolytes. Transformational changes in battery technologies are critically needed to enable the effective use of renewable energy sources such as solar and wind to allow for the expansion of hybrid electric vehicles (HEVs) to plug-in HEVs and pure-electric vehicles. For these applications, batteries must store more energy per unit volume and weight, and they must be capable of undergoing many thousands of charge-discharge cycles. The articles in this theme issue present details of several growing interest areas, including high-energy cathode and anode materials for rechargeable Li-ion batteries and challenges of Li metal as an anode material for Li batteries. They also address the recent progress in systems beyond Li ion, including Li-S and Li-air batteries, which represent possible next-generation batteries for electrical vehicles. One article reviews the recent understanding and new strategies and materials for rechargeable Mg batteries. The knowledge presented in these articles is anticipated to catalyze the design of new multifunctional materials that can be tailored to provide the optimal performance required for future electrical energy storage applications.
    MRS Bulletin 05/2014; 39(05):395-401. DOI:10.1557/mrs.2014.62 · 5.67 Impact Factor
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    Yonhua Tzeng · Shoupu Yeh · Wei Cheng Fang · Yuehchieh Chu ·
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    ABSTRACT: Nitrogen-incorporated ultrananocrystalline diamond (N-UNCD) and multi-layer-graphene-like hybrid carbon films have been synthesized by microwave plasma enhanced chemical vapor deposition (MPECVD) on oxidized silicon which is pre-seeded with diamond nanoparticles. MPECVD of N-UNCD on nanodiamond seeds produces a base layer, from which carbon structures nucleate and grow perpendicularly to form standing carbon platelets. High-resolution transmission electron microscopy and Raman scattering measurements reveal that these carbon platelets are comprised of ultrananocrystalline diamond embedded in multilayer-graphene-like carbon structures. The hybrid carbon films are of low electrical resistivity. UNCD grains in the N-UNCD base layer and the hybrid carbon platelets serve as high-density diamond nuclei for the deposition of an electrically insulating UNCD film on it. Biocompatible carbon-based heaters made of low-resistivity hybrid carbon heaters encapsulated by insulating UNCD for possible electrosurgical applications have been demonstrated.
    Scientific Reports 03/2014; 4:4531. DOI:10.1038/srep04531 · 5.58 Impact Factor
  • Yueh-Chieh Chu · Yonhua Tzeng · Orlando Auciello ·
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    ABSTRACT: Effects of biasing voltage-current relationship on microwave plasma enhanced chemical vapor deposition of ultrananocrystalline diamond (UNCD) films on (100) silicon in hydrogen diluted methane by bias-enhanced nucleation and bias-enhanced growth processes are reported. Three biasing methods are applied to study their effects on nucleation, growth, and microstructures of deposited UNCD films. Method A employs 320 mA constant biasing current and a negative biasing voltage decreasing from -490 V to -375 V for silicon substrates pre-heated to 800 °C. Method B employs 400 mA constant biasing current and a decreasing negative biasing voltage from -375 V to -390 V for silicon pre-heated to 900 °C. Method C employs -350 V constant biasing voltage and an increasing biasing current up to 400 mA for silicon pre-heated to 800 °C. UNCD nanopillars, merged clusters, and dense films with smooth surface morphology are deposited by the biasing methods A, B, and C, respectively. Effects of ion energy and flux controlled by the biasing voltage and current, respectively, on nucleation, growth, microstructures, surface morphologies, and UNCD contents are confirmed by scanning electron microscopy, high-resolution transmission-electron-microscopy, and UV Raman scattering.
    Journal of Applied Physics 12/2013; 115(2). DOI:10.1063/1.4861417 · 2.18 Impact Factor
  • Poying Chen · Jiheng Jiang · Yuming Cheng · M.J. Dai · Yonhua Tzeng ·
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    ABSTRACT: Three-dimensional Integrated-circuit (3DIC) needs coatings with both high thermal conductivity and high electrical insulation for isolating electronic devices and interconnects while spreading heat generated by stacked integrated circuits effectively. Single crystalline diamond possesses excellent electrical insulation and thermal conductivity, which is a perfect candidate for the need by 3DIC. However, a large-area coating of single crystalline diamond is difficult to achieve. So we use polycrystalline diamond films instead. But for polycrystalline diamond films with many grain boundaries, the severe phonon scattering and electrically conductive graphitic carbon contents in grain boundaries cause the electrical insulation and the thermal conductivity to decrease. The smaller the grain size is, usually the decrease is more severe. A good compromise is to retain the high thermal conductivity of diamond crystals while minimizing the electrical conductivity of polycrystalline diamond coatings by removing the charge-transfer doping mechanism enabled by hydrogen termination on diamond grains and minimizing graphitic carbon in the grain boundaries. This paper reports a large-area tri-layer diamond coating structure to achieve sustainable 1010 Ωcm electrical resistivity in the ambient atmosphere. A nanodiamond base layer provides a high-density diamond seeding layer for the polycrystalline diamond film to contain few voids and graphitic carbon in the grain boundaries. The second nanodiamond film is used to encapsulate the de-hydrogenated microcrystalline diamond film to prevent degradation of electrical resistance due to the ambient atmosphere.
    2013 IEEE 13th International Conference on Nanotechnology (IEEE-NANO); 08/2013
  • Chichun Lu · Yuehchieh Chu · Yonhua Tzeng ·
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    ABSTRACT: We report the application of nanodiamond prepared by microwave plasma chemical deposition system as the dielectric film with copper as top electrodes and a tungsten counter electrode for the fabrication of resistive random access memory (RRAM). The RRAM is switched between the high-resistivity state and a low-resistivity state of nanodiamond film. The high or low resistance state can be probed by applying a low voltage across two counter electrodes on two sides of the nanodiamond film and measuring its conduction current. We observed that the Cu/Nanodiamond/W structure shows good performance with ON/OFF current ratio >105 and retention time >104 s. Nanodiamond is known to be chemically inert, good for heat dissipation, and has very low solid solubility in copper. It is, therefore, a suitable dielectric material for RRAM for harsh environments.
    2013 IEEE 13th International Conference on Nanotechnology (IEEE-NANO); 08/2013
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    ABSTRACT: We report on a polarized Raman study on mechanically cleaved single-layer graphene films. Under a specific orientation of scattering measurement, the width and position of the G peak change with the incident polarization direction, while the integrated intensity of that is unaltered. This phenomenon is explained by a proposed mode in which the peak is contributed by a mixture of un-, compressive-, and tensile-strained G sub-modes. The compression and tension are both uniaxial and approximately perpendicular to each other. They are undesigned and located in either separated or overlapped sub-areas within the probed local region. Compared to the unstrained wavenumber of 1580 cm(-1), compression induces a blue shift while tension causes a red one. The sub-modes correlated with the light polarization through different relationships split the G peak into three sub-ones. We develop a method to quantitatively analyze the positions, widths, intensities, and polarization dependences of sub-peaks. This analysis quantitatively reveals local strain, which changes with the detected area of a graphene film. The method presented here can be extended to detect the strain distribution in the film and thus is a promising technology for graphene characterization.
    Nanoscale 07/2013; 5(20). DOI:10.1039/c3nr00123g · 7.39 Impact Factor
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    ABSTRACT: Heteroepitaxial nucleation of {0 0 2} graphene sheets on {1 1 1} facets of plasma treated (1 0 0) silicon by direct-current plasma enhanced chemical vapor deposition in methane–hydrogen gas mixtures is confirmed by high-resolution transmission electron microscopy. Lattice mismatch by 12% is compensated by tilting the graphene {0 0 2} with respect to silicon {1 1 1} and matching the silicon lattice with fewer graphene layers. The interlayer spacing of graphene sheets near the silicon surface is 0.355 nm, which is larger than that of AB stacked graphite and confirmed as AA stacked graphitic phase. Subsequent growth of standing graphene nanowalls is characterized by scanning electron microscopy and Raman scattering (633 and 514 nm excitation). The Raman peaks of D-band, G-band, and 2D-band are discussed in correlation with SEM images of graphene nanowalls. A strong Raman peak corresponding to silicon–hydrogen stretch vibration is detected by 633 nm excitation at the early stage of graphene nucleation, indicating the silicon substrate etched by hydrogen plasma. With these analyses, the growth mechanism is also proposed in this paper.
    Carbon 04/2013; 54:234–240. DOI:10.1016/j.carbon.2012.11.034 · 6.20 Impact Factor
  • Yonhua Tzeng · Wai Leong Chen · Chiahao Wu · Jui-Yung Lo · Chiuan-Yi Li ·
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    ABSTRACT: Graphene nanowalls have been synthesized on diamond by direct-current plasma enhanced chemical vapor deposition (CVD) on silicon substrates pre-seeded with diamond nanoparticles in gas mixtures of methane and hydrogen. Switching from diamond CVD to graphene CVD is done by increasing the methane concentration and decreasing the plasma power without breaking the vacuum. Graphene nanowalls stand on the CVD diamond film to form a 3-dimensional network. Scanning electron microscopy, high-resolution transmission electron microscopy, UV and visible Raman scattering and electrochemical cyclic voltammetry measurements are used to characterize the multi-layer turbostratic graphitic carbon nanostructure and demonstrate its electrochemical durability with a low background current in a wide electrochemical potential window.
    Carbon 03/2013; 53:120–129. DOI:10.1016/j.carbon.2012.10.038 · 6.20 Impact Factor
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    ABSTRACT: Fluorescence quenching effects on graphene or hydrogen-terminated graphene covered sliver nanoparticles are studied and the results are explained with energy transfer models. The fluorescence signal of R6G is suppressed by the graphene flakes via Förster resonance energy transfer and by the silver nanoparticles via surface energy transfer. The relative fluorescence intensities of R6G are reduced to 28% and 69% on the single-atom-thick graphene flake and the hydrogen-terminated graphene covered silver film, respectively. The mechanism of the quenching effect is illustrated by the energy diagram of electron transition.
    Applied Physics Letters 02/2013; 102(5). DOI:10.1063/1.4790825 · 3.30 Impact Factor
  • Hsin-Yen Cheng · Jau-Wern Chiou · Jyh-Ming Ting · Yonhua Tzeng ·
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    ABSTRACT: Various chromium-containing amorphous hydrogenated carbon (a-C:H/Cr) coatings were deposited on oxygen-free copper and silicon substrates for use as solar selective absorber coatings. The deposition was performed using a magnetron co-sputter deposition method under various methane/Ar ratios, ranging from 0 to 8%. The obtained films were characterized using glazing incident X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, secondary ion mass spectrometer, and X-ray photoelectron spectroscopy. The optical absorptance and emittance at 100 °C were determined using UV–vis-NIR spectroscopy and Fourier transform infrared spectrometry, respectively. Effects of the material characteristics on the optical properties are reported and discussed.
    Thin Solid Films 02/2013; 529:164–168. DOI:10.1016/j.tsf.2012.10.025 · 1.76 Impact Factor
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    ABSTRACT: C K-, Cr L3.2-, and K-edge X-ray absorption near-edge structure (XANES) analysis, high-resolution transmission electron microscopy examination, and optical absorptance have been examined to obtain a correlation between the optical absorptance and electronic structure of chromium-containing amorphous hydrogenated carbon thin films (a-C:H/Cr) deposited using a dc magnetron sputter deposition technique. It was found that the C 2pCr 3d hybridization gradually increases as the Cr nanoparticle (NP) size decreases, accompanied by a C 2p interband transition. The amount of CH bonding and the change in crystalline structure are the main factors affecting the optical absorptance of the thin films. The size of the Cr NP affects the absorption wavelength range of the films. The optical absorptance and C K-edge XANES spectra indicate that a decrease in the size of Cr NP raises the conduction-band-minimum and may also increase the bandgap.
    Applied Surface Science 01/2013; 264:202–206. DOI:10.1016/j.apsusc.2012.09.172 · 2.71 Impact Factor
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    ABSTRACT: Bias-enhanced nucleation and growth of ultrananocrystalline diamond (UNCD) nano-pillars on silicon substrates by low-pressure microwave plasma chemical vapor deposition in a hydrogen-rich gas mixture with methane is reported. Direct-current biasing of the substrate in a constant-current mode is applied to substrates, which are pre-heated to 800 °C, to result in a negative bias voltage of greater than 350 V throughout the nucleation and growth process. Self-masking by UNCD clusters, angle dependent sputtering of UNCD clusters, and ion-assisted chemical vapor deposition by bias enhanced bombardment of energetic ions are attributed to the formation of UNCD nano-pillars. High-resolution transmission electron microscopy analysis indicates that an interfacial layer exists between the silicon substrate and the UNCD nano-pillars. The porous UNCD film with high-density nano-pillars exhibits excellent optical anti-reflectivity and improved electron field emission characteristics compared to smooth and solid UNCD films.
    Journal of Applied Physics 12/2012; 112(12). DOI:10.1063/1.4769861 · 2.18 Impact Factor
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    Chih-Yi Liu · Kengchih Liang · Chun-Cheng Chang · Yonhua Tzeng ·
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    ABSTRACT: Effects and mechanisms of conductivity variation of chemically vapor deposited single-layer graphene covering silver nanoparticles on SiO<sub>2</sub>/Si are reported based on blue-light (405nm) induced plasmonic coupling and electrical current induced annealing and desorption of surface adsorbates. With 1V applied voltage, photoconductivity is positive except a brief negative period when the graphene is first illuminated by light. At 10mV applied voltage, negative photoconductivity persists for hours. In comparison, negative photoconductivity of graphene on pristine SiO<sub>2</sub>/Si persists for tens of hours. When the applied voltage is increased to 1V, it takes tens of hours of light illumination to change to positive photoconductivity.
    Optics Express 09/2012; 20(20):22943-52. DOI:10.1364/OE.20.022943 · 3.49 Impact Factor
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    ABSTRACT: We report on effects of a tungsten layer deposited on silicon surface on the effectiveness for diamond nanoparticles to be seeded for the deposition of ultrananocrystalline diamond (UNCD). Rough tungsten surface and electrostatic forces between nanodiamond seeds and the tungsten surface layer help to improve the adhesion of nanodiamond seeds on the tungsten surface. The seeding density on tungsten coated silicon thus increases. Tungsten carbide is formed by reactions of the tungsten layer with carbon containing plasma species. It provides favorable (001) crystal planes for the nucleation of (111) crystal planes by Microwave Plasma Enhanced Chemical Vapor Deposition (MPECVD) in argon diluted methane plasma and further improves the density of diamond seeds/nuclei. UNCD films grown at different gas pressures on tungsten coated silicon which is pre-seeded by nanodiamond along with heteroepitaxially nucleated diamond nuclei were characterized by Raman scattering, field emission-scanning electron microscopy, and high resolution-transmission electron microscopy.
    Journal of Applied Physics 06/2012; 111(12). DOI:10.1063/1.4729798 · 2.18 Impact Factor
  • S.-T. Chen · Y.-C. Chu · C.-Y. Liu · C.-H. Huang · Y. Tzeng ·
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    ABSTRACT: Nanodiamond seeds on substrates and ultrananocrystalline diamond (UNCD) at the early-stage of CVD have been characterized by surface-enhanced Raman spectroscopy (SERS). Anodic aluminum oxide (AAO) films encapsulated with two-dimensional arrays of silver nanoparticles are used as the substrates. UNCD is grown by 400 W, 2.45 GHz microwave plasma CVD using detonation nanodiamond as seeds in a gas mixture of 1% methane diluted by 99% argon at the substrate temperature of 400 °C and gas pressure of 100 Torr for 15–45 min. Light illumination on Ag nanoparticles induces strong plasmonic coupled local electromagnetic fields for enhancing Raman scattering signals from nanodiamond seeds and UNCD films on AAO substrates at the early-stage of CVD. With electrodeposited silver nanoparticles photoluminescence signal is suppressed for revealing weak Raman signals. Fabrication of the Ag/AAO SERS substrates and the SERS spectra for nanodiamond seeded AAO substrates and ultra-thin UNCD at the early-stage of CVD growth are discussed.
    Diamond and Related Materials 04/2012; 24:161–166. DOI:10.1016/j.diamond.2012.01.005 · 1.92 Impact Factor
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    ABSTRACT: For low-power and low-temperature microwave plasma CVD of UNCD in gas mixtures of methane and argon without hydrogen and oxygen additives, excessive carbon containing species often induce gas phase synthesis of non-diamond carbon phases, which fall on diamond growing surfaces to become part of the deposited diamond films. To prevent undesirable gas phase reactions, effects of gas residence time, or equivalently, the total gas flow rate at a fixed gas pressure and compositions, on the microwave plasma and its deposition of UNCD are studied. The gas residence time is increased by by-passing an increasing amount of a pre-set mixture of methane and argon at a fixed total flow rate through a mass flow controller to a vacuum pump while allowing the rest of the gas feed to flow through the reaction chamber. The gas composition, gas pressure, microwave power, and substrate temperature are kept constant. Optimization of the UNCD growth is, thus, achieved by increasing the gas residence time to deposit UNCD of high phase purity.
    Diamond and Related Materials 04/2012; 24:153–157. DOI:10.1016/j.diamond.2012.01.003 · 1.92 Impact Factor
  • Kengchih Liang · Chun-Cheng Chang · Chih-Yi Liu · Yonhua Tzeng ·
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    ABSTRACT: Effects of plasmonic coupling on blue laser induced positive and negative photoconductivity of chemically vapor deposited mono-layer graphene transferred onto SiO2/Si with or without silver nanoparticles in ambient atmosphere are reported. Ggraphene on silver nanoparticles coated SiO2/Si exhibits negative and rapidly decreasing photoconductivity upon light illumination. The photoconductivity recovers gradually and then become positive photoconductivity. In the subsequent on-off cycles of light illumination, the graphene exhibits positive photoconductivity. Graphene on SiO2/Si without silver nanoparticles also exhibits negative and rapidly decreasing photoconductivity upon light illumination followed by a gradual increase in conductivity. However, the negative photoconductivity persists for a test period longer than 30 hours when light is turned on and off. Adverse effects on electrical conductivity due to electron scattering by surface and interfacial charges, decrease in surface dopants due to desorption induced by incident photons, plasmonic coupling induced local electromagnetic fields combined with enhanced electron transport between silver nanoparticles, and photon generated electron-hole pairs in silicon contribute to the measured photoconductivity. Annealing by electrical current and Joule heating adds to the complexity of the observed effects of current density on positive and negative persistent photoconductivity.
    Nanotechnology (IEEE-NANO), 2012 12th IEEE Conference on; 01/2012
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    ABSTRACT: Synthesis of graphene of large domain sizes in order to minimize scattering of charge carriers in grain boundaries is an essential process to be achieved before the full merits of graphene can be realized for next-generation nanoelectronics. Independent control of nucleation processes and growth processes in the complicated chemical vapor deposition environments is a key to achieving this goal. Catalyst assisted chemical vapor deposition of graphene on copper at around 1000°C near the melting point of copper in hydrogen diluted methane is fine tuned to reach dynamic balance between etching and growth of graphene. Surface diffusion of carbon atoms generated from methane and other hydrocarbon species, including those from etching graphene by atomic hydrogen, generated by the assistance of copper catalyst on the surface of copper foil results in complicated network of graphene domains separated by alley-like gaps of nearly equal width. By controlling the dynamic balance point, independent control of nucleation and growth and the synthesis of large individual graphene of various unique shapes and graphene films with networked alleys have been demonstrated.
    Nanotechnology (IEEE-NANO), 2012 12th IEEE Conference on; 01/2012

Publication Stats

657 Citations
189.07 Total Impact Points


  • 2008-2014
    • National Cheng Kung University
      • • Institute of Microelectronics
      • • Department of Electrical Engineering
      臺南市, Taiwan, Taiwan
  • 2012
    • WWF United Kingdom
      Londinium, England, United Kingdom
  • 2011
    • Institute of Microelectronics
      Tumasik, Singapore
  • 1989-2010
    • Auburn University
      • • Department of Electrical & Computer Engineering
      • • Alabama Microelectronics Science and Technology Center
      Auburn, Alabama, United States