bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bi-directional porous alumina templates for nanowire field-effect transistors
Authors: Wade Travis L. , Hoffer Xavier , Dayen Jean-Francois , Mohammed Al Dughaim , Humel Fahad , Wegrowe Jean-Eric 
Published: April 2011

AbstractUsing readily available materials and equipment we are able to sculpture aluminium wires into cylindrical, bi-directional templates for the synthesis and contacting of nanowires as field-effect transistors. The nanowire template is made by partial anodization of the wire perpendicular to its axis as an isolating layer for a gate electrode, vapour deposition of a metal on this layer as a gate, cutting the wire perpendicular to its axis, and finally anodizing the newly exposed area parallel to the wire axis as a template for nanowires. This results in a nanowire template surrounded by a gate electrode that is isolated from the template by the first anodisation layer.The utility of this structure is demonstrated by a ZnO nanowire field-effect transistor. The ZnO was made by electrodeposition of Zn nanowires in the interior nanoporous template during which an anodic pulse was applied to form a layer of ZnO in the middle of the zinc nanowires. The IV and transfer plots indicate that the ZnO is p-type in depletion mode.This 3-D transistor is unique in that it can be totally fabricated in a beaker without the need for costly clean room and lithography facilities. The ease and low cost of this new approach to nanodevices will have the effect of liberating nanoscience for scientists of moderate means. As a result this will open nanoscience to new ideas and more inputs.
A Chemical Approach to 3-D Lithographic Patterning of Si and Ge Nanocrystals
Authors: Sharp I. D. , Xu Q. , Yi D. O. , Liao C. Y. , Ager III J. W. , Beeman J. W. , Yu K. M. , Robinson J. T. , Dubon O. D. , Chrzan D. C. , Haller E. E. 
Published: April 2011

AbstractIon implantation into silica followed by thermal annealing is an established growth method for Si and Ge nanocrystals. We demonstrate that growth of Group IV semiconductor nanocrystals can be suppressed by co-implantation of oxygen prior to annealing. For Si nanocrystals, at low Si/O dose ratios, oxygen co-implantation leads to a reduction of the average nanocrystal size and a blue-shift of the photoluminescence emission energy. For both Si and Ge nanocrystals, at larger Si/O or Ge/O dose ratios, the implanted specie is oxidized and nanocrystals do not form. This chemical deactivation was utilized to achieve patterned growth of Si and Ge nanocrystals. Si was implanted into a thin SiO2 film on a Si substrate followed by oxygen implantation through an electron beam lithographically defined stencil mask. Thermal annealing of the co-implanted structure yields two-dimensionally patterned growth of Si nanocrystals under the masked regions. We applied a previously developed process to obtain exposed nanocrystals by selective HF etching of the silica matrix to these patterned structures. Atomic force microscopy (AFM) of etched structures revealed that exposed nanocrystals are not laterally displaced from their original positions during the etching process. Therefore, this process provides a means of achieving patterned structures of exposed nanocrystals. The possibilities for scaling this chemical-based lithography process to smaller features and for extending it to 3-D patterning is discussed.
Morphology Control of ZnO Nanomaterials using Double Hydrophilic Block Copolymers
Authors: Mezy A. , Gérardin C. , Tichit D. , Suwanboon S. , Ravot D. , Jean-Claude Tedenac , Bretagnon T. , Lefèbvre P. 
Published: April 2011

AbstractHighly crystalline zinc oxide (ZnO) nanomaterials are synthesized using a seeded growth sol-gel method. In order to control the morphology and the organization of the ZnO nanomaterials, a double hydrophilic block copolymer has been introduced during the seeded growth synthesis: the Polyacrylic acid-Polyacrylamide (PAA-PAM). Depending on the amount of PAA-PAM copolymers, different morphologies were obtained, such as ZnO nanostructured spheres or flat hexagonal crystals. Thus, systematic studies have been done to investigate the influence of the copolymer addition on ZnO nanomaterial morphologies and explain the mechanisms of the morphological modifications.
Analysis of plasma for carbon nanotube growth by plasma-enhanced chemical vapor deposition
Authors: Ozeki Atsushi , Suda Yoshiyuki , Okita Atsushi , Nakamura Junji , Oda Akinori , Sakai Yosuke , Sugawara Hirotake 
Published: April 2011

AbstractOptical emission spectra of a CH4/H2/Ar gas mixture plasma were observed during carbon nanotube (CNT) growth in RF plasma-enhanced chemical vapor deposition. CNTs with diameters of ∼10-30 nm and length of ∼6 μm were grown on double- and triple-layered films of catalyst/support materials (FexOy/TiO2 and Al2O3/FexOy/Al2O3) at the total gas pressures of 1-10 Torr with gas flow rates of CH4 = 27 sccm, H2 = 3 sccm, and Ar = 1 sccm. The number density of CNTs increased with the gas pressure, and Al2O3/FexOy/Al2O3 (each thickness of 1 nm) film yielded the thinnest CNTs with a high number density among the present catalysts. The spatial distributions of H atom relative density in the plasma were obtained by actinometry. The H relative density decreased with the pressure, and this suggests the suppression of CH3 radical generation in the plasma.
Phase Equilibria Studies of Hf44.5Ti5Cu27Ni13.5Al10 and Hf44.5Nb5Cu27Ni13.5Al10
Authors: Woodman Robert , Kecskes Laszlo 
Published: April 2011

AbstractWe report the equilibrium phase assemblage of two bulk-metallic-glass-forming alloys, Hf44.5Ti5Cu27Ni13.5Al10 and Hf44.5Nb5Cu27Ni13.5Al10. Using thermal analysis, scanning electron microscopy, and x-ray microanalysis, we examined the phase equilibria of the major components - Hf, Cu, and Ni. We then examined the effect of additions or substitutions of Nb, Ti, and Al on equilibrium phase assemblage and melting behavior.
Processing and Properties of Nanostructured Alloy Coatings in the Binary Ni-Cr System
Authors: Castro Pablo , Schuh Christopher A. , Liang Hong 
Published: April 2011

AbstractUsing a scalable electrodeposition process, nanocrystalline Ni-Cr alloy coatings have been produced on copper and steel substrates, and the roles of various processing variables on the resulting coating structure and properties have been investigated. The possibility of producing composite coatings of wear resistant nanostructured Ni-Cr alloys containing graphite or MoS2 particles has also been studied; the co-deposition of solid lubricant particles improved the tribological performance of the coatings in ball-on-disk testing. The combination of a hard material such as nanocrystalline Ni-Cr alloy with a solid lubricant has a great potential for new surface modification developments.
The Effect of As-quenched Structure on Primary Phase Crystallization in Amorphous Aluminum Alloys
Authors: Hamann Joseph , Perepezko John H 
Published: April 2011

AbstractFrom the reported experience, primary nanocrystallization in amorphous Al alloys involves transient kinetic behavior that is sensitive to the initial as-quenched structural arrangements. In order to examine the precursor effects, systematic studies outlining the evolving growth kinetics of primary aluminum nanocrystals (nc) during pre-crystallization annealing treatments, and investigations on the microstructure refining effect of specific alloying substitutions represent new approaches for an analysis of primary phase crystallization kinetics. In Al88Ni8Sm4 melt-spun ribbon (MSR), incremental substitutions of Cu for Ni (0 − 1at%) affect the thermal stability of the material (crystallization onset shifts to lower temperature) and refine the size of the primary phase nanocrystals. However, continuous heating calorimetry measurements indicate that the primary crystallization enthalpy remains approximately constant with increased Cu substitution. From a structural analysis standpoint, quantitative microstructure examinations applied in parallel with calorimetry measurements have been employed to characterize the as-quenched volume of MSR samples. The increased primary Al nanocrystal particle density with Cu substitution reflects the modification of local structural arrangements, necessitating an understanding of the local structure of the as-quenched sample in order to develop a description of primary phase nanocrystal growth kinetics.
Binormal Nanohelices
Authors: da Fonseca Alexandre F. , Galvao Douglas S. , Malta Coraci P. 
Published: April 2011

AbstractHelical structures can be classified in accordance with the orientation of its cross-section with respect to the normal or binormal vectors. We investigate the geometric features of several nanosprings verifying the non-existence of normal nanohelices. In this work, using the VLS growth model, we explain not only the absence of normal nanosprings but also the growing process of binormal nanosprings. The dynamical stability of crystalline ZnO binormal nanohelices is also addressed.
A Study on the Tribological Properties of DLC Films Deposited with Different Reaction Gases
Authors: Cho Yong Ki , Kim Gang San , Moon Kyoung Il , Kim Sang Gweon , Kim Sung Wan 
Published: April 2011

AbstractDiamond like carbon (DLC) coatings have attracted great attention for use in various applications in automobile industry and machinery because they have excellent properties such as low friction coefficient and ultra high strength. The low friction coefficient of DLC comes from anti-adhesion with other materials, smooth surface, lubrication of graphite structure at the contacting point of films, and the hydrogen content of the films. Many researches have been focused on the microstructure effects on the tribological properties of DLC films but few have been reported on the effect of hydrogen content. In this study, the effect of hydrogen content on the friction coefficient of DLC films has been investigated.DLC films have been deposited on D2 steel by plasma enhanced CVD (Pulsed DC PECVD) method with different precursor gas of C2H2and CH4and different gas pressure. The effects of gas composition on the hydrogen content in DLC films and the resulting tribological properties have been reviewed. Si interlayer was deposited on D2 to improve adhesion of DLC on steel substrates. The characteristics of microstructure were evaluated by Raman spectroscope and composition was measured by RBS and EDS. The tribological behaviors of DLC films were investigated using ball on disk tribometer. The hardness of films was examined by nano-indenter. The failure mechanism of DLC deposited on steel substrates was examined using optical microscope and SEM/EDS. The results showed that the friction coefficient of DLC films deposited with C2H2was 0.06 and that of the film with CH4was 0.15. The friction coefficient improved with decreasing hydrogen content in DLC films.
The Role of Multiple Polytypes in Determining the Catastrophic Failure of Boron Carbide at High Shock Velocities
Authors: Fanchini Giovanni , McCauley James W , Niesz Dale E , Chhowalla Manish 
Published: April 2011

AbstractThe absence of a plastic phase in boron carbide and its failure at shock impact velocities just above the Hugoniot elastic limit (HEL) has been a puzzle for a long time. In the present work, using self-consistent field density functional simulations we are able to account for many experimental observations by noticing that several boron carbide polytypes [(B11C)C2B, (B12)C3, etc …] coexist without significant lattice distortions. Our analysis also indicates that above a threshold pressure all the candidate microstructures are less stable than a phase involving segregated boron (B12) and amorphous carbon (a-C) but the energetic barrier between boron carbide and B12 + 3C, is by far lower for the B12(CCC) microstructure, requiring the lowest atomic displacement for a transformation B4C→3B+a-C, occurring at pressures of 6 GPa = P(HEL). For such a configuration, segregation of free carbon occurs in layers orthogonal to the (113) lattice directions, in excellent agreement with recent transmission electron microscopy (TEM) analysis
Preparation and Nanoindentating mechanical Analyses of Porous SiO2 Low-Dielectric-Constant Films
Authors: Chang Shou-Yi , Huang Yi-Chung , Yang Bo-Kang 
Published: April 2011

AbstractPorous SiO2 low-dielectric-constant films containing different porosities and sizes of pores were prepared in this study. Their mechanical properties were analyzed by a nanoindentation test. The hardness and elastic modulus of the films prepared with an ethanol molar ratio of 3 and an aging time of 16 hours reached maximum values of 2.4 and 40 GPa, respectively. With a higher ethanol ratio, the porosity increased, and the mechanical properties consequently decreased. With increasing aging time, the mechanical properties increased and then dropped due to enlarged pore sizes. The porous SiO2 films were found to yield at an ultimate stress of 3.1 GPa, and the maximum fracture energy release rate was calculated as 3.4 J/m2. The deformation and fracture behavior was observed through crack initiation and propagation along the large amount of pores.
ZITO (ZnO-SnO2-In2O3 ) Transparent Conducting Oxides: Electrical and Optical Properties of DC Magnetron Sputtered Films
Authors: Ow-Yang Cleva , Yeom Hyo-Yong , Yaglioglu Burag , Paine David C. 
Published: April 2011

AbstractAmorphous ZITO films were deposited by dc magnetron sputtering onto glass substrates from ceramic oxide targets containing Zn:In:Sn cation ratios of 1:2:1 and 1:2:1.5. The microstructure, carrier density, mobility, and resistivity of as-deposited and annealed samples were evaluated using x-ray diffraction and Hall effect measurements. The as-deposited films were amorphous and remained so after annealing at 200°C in air for up to five hours. Transmissivity of the films exceeded 80% in the visible spectral region. The minimum resistivity value (7.6×10−4 Ω-cm) was obtained from thin films deposited using the 1:2:1 composition target and a substrate temperature of 300°C.
Molybdenum doped Indium Oxide thin films prepared by rf sputtering
Authors: Elangovan Elamurugu , Marques Antonio , Pimentel Ana , Martins Rodrigo , Fortunato Elvira 
Published: April 2011

AbstractMolybdenum doped indium oxide (IMO) thin films rf sputtered at room temperature were studied as a function of oxygen volume percentage (O2 vol. %) varied between 0 and 17.5. The as-deposited films were amorphous irrespective of O2 vol. %. The minimum transmittance (<10 %) of the films deposited without oxygen has been increased on introducing oxygen (3.5 O2 vol. %) to a maximum of 90 %. The optical band gap has been increased from 3.80 eV (without oxygen) to 3.92 eV (3.5 O2 vol. %). The films were highly resistive and the hall coefficients were detectable only for the films deposited without oxygen. In order to increase the electrical conductivity, the films were annealed in the range 100-500°C in open-air and N2/H2 gas for 1 hour. The annealed films become polycrystalline with enhanced electrical and optical properties. The effect of annealing conditions on these films will be presented and discussed in detail.
Variable Temperature Capacitance-Voltage Measurements to Investigate the Density of Localized Trapping Levels in Organic Semiconductors
Authors: Sedghi Naser , Donaghy David , Raja Munira , Badriya Samer , Higgins Simon J. , Eccleston Bill 
Published: April 2011

AbstractWe have approximated the tail of the Gaussian distribution of states of organic semiconduc-tors with an exponential function. We have used this approach to calculate the carrier concentra-tion in organic materials, and subsequently the charge distribution in the accumulation region of a field effect device and the space-charge capacitance in accumulation mode. Small signal high frequency capacitance-voltage measurements performed at various temperatures show good agreement with this model and the characteristic temperature of the exponential function has been estimated from these measurements based on the theory developed.
In-situ TEM Study of Thermally Induced Voids in 180 nm Cu Interconnects
Authors: An Jin Ho , Ferreira P.J. 
Published: April 2011

AbstractCu interconnects have decreased in width and are at around 100 nm. A decrease in interconnect width have led to a predominately bamboo structured Cu lines. In Cu interconnects, void formation during high temperature is a reliability issue, and this study looks at the void formation behavior in damascene Cu interconnects with a predominately bamboo microstructure. First, the crystal texture and grain morphology of the Cu interconnects was observed. Then to determine the void formation behavior, in-situ Transmission Electron Microscopy (TEM) was performed. Voids that formed as a result of in-situ heating were analyzed in terms of preferential void formation sites and crystal orientation where voids formed. In bamboo structured lines, voids formed at the triple junction of grain boundary and Cu/diffusion barrier interface. The crystal orientation where voids nucleated was studied to identify diffusion paths during void nucleation and growth.
In-situ TEM observation of electromagnetic field in some real materials
Authors: Sasaki Katsuhiro , Wang Zhouguang , Fukunaga Keiichi , Hirayama Tsukasa , Kuroda Kotaro , Saka Hiroyasu 
Published: April 2011

AbstractElectromagnetic fields presents in some real materials have been observed using electron holography and a simple method named the Shadow Image Distortion (SID) method which we have developed. The in-situ electron holography observation of the electric field surrounding a ceramic particle showed the rapid degradation of dielectric properties of the particle at an elevated temperature. The cross sectional view of mean electrostatic potential distributions in a silicon device has been observed. In-situ electron holography and SID observations showed the electrostatic potential distribution across a reverse biased p-n junction in a compound semiconductor. The SID method using a dedicated tool allowed single-step imaging of 2D maps of electromagnetic field.
Quantifying the Order of Spontaneous Ripple Patterns on Ion-Irradiated Si(111)
Authors: George H. Bola , Brown Ari-David , McGrath Matthew R. , Erlebacher Jonah D. , Aziz Michael J. 
Published: April 2011

AbstractUniform keV ion irradiation causes a morphological instability known to result in the spontaneous formation of topographic ripple and dot patterns. The degree of order of these patterns, which has important implications for non-lithographic patterning applications, varies markedly with fabrication conditions. We investigate the influence of systematic variations of fabrication conditions, including current density, ion fluence and ion energy, on the degree of order of argon ion bombarded Si(111) surfaces. For quantifying order in sputter rippled topographic images, we develop an algorithm that evaluates the density of topological defects, such as ripple bifurcations and terminations, and suitably normalizes the result in order to present a scalar figure of merit: the normalized defect density. We discuss fabrication conditions that lead to extremely well ordered dot and ripple patterns upon irradiation.
Irradiation-Enhanced Second-Phase Precipitation in Zr-Fe Nanocrystalline Thin Films
Authors: Kaoumi Djamel , Motta Arthur T. , Birtcher Robert C. 
Published: April 2011

AbstractIn situ observations in a transmission electron microscope (TEM) were used to study ion-beam enhancement of second-phase precipitation in Zr-Fe nanocrystalline thin films. The free-standing films were prepared by co-sputter deposition with an Fe content of 1.2 at%. TEM diffraction analysis showed that only the hcp Zr crystal structure was present in the as-deposited films. No second phases were detected, although Rutherford Backscattering Spectroscopy (RBS) confirmed a Fe content beyond the solubility limit of Fe in Zr (of the order of ppm). This means the thin films were Zr solid solutions supersaturated with Fe. Heat treatment in the absence of irradiation was observed to cause precipitation of the Zr2Fe intermetallic phase, but only above 673 K. The same second-phase precipitation can occur at lower temperatures in the presence of ion irradiation. Samples were irradiated in-situ at the Intermediate Voltage Electron Microscope (IVEM) at Argonne National Laboratory with Kr ions to fluences in excess of 1016 ion/cm2, at temperatures ranging from 50 to 573 K. Second phase precipitation was detected by electron diffraction patterns and by dark field imaging comparing regions exposed to the beam with regions protected from the beam by the TEM support grid. Precipitation of Zr2Fe intermetallic phase was observed at all irradiating temperatures above room temperature. In the bulk, this phase is thermodynamically metastable in the range of temperatures investigated (relative to the orthorhombic Zr3Fe intermetallic phase). The kinetics of the irradiation-enhanced second-phase precipitation was followed by recording the diffraction patterns at regular intervals. The dose to precipitation was found to decrease with increasing irradiation temperature.
Nano-Sized Zirconium Carbides: Synthesis, Characterisation and Irradiation
Authors: Dollé Mickaël , Gosset Dominique , Bogicevic Christine , Baldinozzi Guido , Karolak Fabienne , Simeone David 
Published: April 2011

AbstractThe projects of a new generation of nuclear plants with improved yield and drastical reduction of waste production make necessary the development of materials able to withstand high temperature (1000-1200°C) in normal conditions. New materials such as the refractory transition metal carbides are then considered. These materials have a ceramic-like, brittle behaviour. Their mechanical properties might be improved by decreasing the particles size at a nanometer level. The behaviour under irradiation of such nano-sized materials have then to be compared with classical micro-sized ones. High density, nano-sized materials have been obtained by two different sintering techniques. In order to simulate neutron irradiation, the samples were irradiated with low energy heavy ions. Consequently, the damaged material has a low thickness (100-200 nm), requiring surface analysis methods. Here, the grazing incidence X-ray diffraction method is used. From a Rietveld analysis of the diffraction patterns, the micro-sized materials show a linear volume swelling in the range 20-40 dpa in the Zr sublattice. Nano- and micro-sized materials both show high internal distortions.