bluuebunny/crossref_metadata_2025_split huggingface dataset:
Low Temperature Synthesis of Silicon Oxide Nanowires
Authors: Siddique Rezina , Sirinakis George , Carpenter Michael A. 
Published: June 2019

AbstractSilicon Nanowires (SiNWs) have many potential applications that include diodes, transistors, logic gates, circuitry, and sensors. SiNWs also open the possibility for integrating optoelectronics with microelectronics, since silicon has semiconducting properties and amorphous silicon nanowires have been shown to emit blue light. It has been demonstrated that SiNWs have tunable electrical properties, depending on the dopant used. With such a range of applications, the ability to mass-produce silicon nanowires simply and easily with no other source of silicon needed other than the substrate itself will prove very useful. Such methods have previously been reported, but our method involves production of the SiNWs at a lower temperature than those widely observed. A (100) silicon substrate was cleaned for five minutes each in ethanol followed by acetone. Films with thicknesses of less than 20 nm of either gold or 60/40 gold/palladium were deposited on the substrate through physical vapor deposition to serve as the growth center for the SiNWs. The samples were placed in a furnace and annealed to 900° C, under a 1500 sccm flow of argon at atmospheric pressure. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used for characterization of the SiNWs. The resulting SiNWs were amorphous in structure and very convoluted, with lengths on the order of tens of microns, diameters of 40 nm and a bed thickness of approximately 10 m. The effect of varying gold concentration, annealing time, temperature, and gas flow rate were then investigated. The results, which will be discussed in further detail, indicate that adjusting these parameters allows for control over the length, thickness, density, and morphology of the nanowires.
AC Electrodeposition of Uniform High Aspect-Ratio Metal Nanowires in Porous Aluminum Oxide Templates
Authors: Gerein Nathan J. , Mithani Shazma S. , Haber Joel A. 
Published: June 2019

AbstractThe use of alternating current (ac) electrodeposition permits deposition through the resistive Al2O3 barrier layer, enabling the use of the as-grown porous aluminum oxide (PAO) template. This results in a process that is cost effective, simple, and scalable. However, achieving uniform filling using this technique is challenging. We have carried out a systematic study of the effect of multiple variables on the ac electrodeposition of copper nanowires using a fractional factorial design of experiment (FFDOE). This experiment led to the identification of template damage that occurs when continuous wave ac deposition conditions are employed, as well as to effective pulsed wave ac electrodeposition conditions. Subsequent examination of the effect of wave shape has identified the impact of this variable on electrodeposition, producing a further optimized set of ac electrodeposition conditions. The utility of these electrodeposition conditions has also been extended to the deposition of iron nanowires with similar results.
Interactions of Ge Atoms with High- ê Oxide Dielectric Surfaces
Authors: Stanley Scott K. , Ekerdt John G. 
Published: June 2019

AbstractGe is deposited on HfO2 surfaces by chemical vapor deposition (CVD) with GeH4. 0.7-1.0 ML GeHx (x = 0-3) is deposited by thermally cracking GeH4 on a hot tungsten filament. Ge oxidation and bonding are studied at 300-1000 K with X-ray photoelectron spectroscopy (XPS). Ge, GeH, GeO, and GeO2 desorption are measured with temperature programmed desorption (TPD) at 400-1000 K. Ge initially reacts with the dielectric forming an oxide layer followed by Ge deposition and formation of nanocrystals in CVD at 870 K. 0.7-1.0 ML GeHx deposited by cracking rapidly forms a contacting oxide layer on HfO2 that is stable from 300-800 K. Ge is fully removed from the HfO2 surface after annealing to 1000 K. These results help explain the stability of Ge nanocrystals in contact with HfO2.
Sol Gel Preparation of Ta2O5 Nanorods Using DNA as Structure Directing Agent
Authors: Monreala Humberto A. , Villafañe Alberto M. , Chacón José G. , García Perla E. , Martínez Carlos A. 
Published: June 2019

AbstractTransition metal oxides are being considered as the next generation materials in field such as electronics and advanced catalysts; between them is Tantalum (V) Oxide; however, there are few reports for the synthesis of this material at the nanometer size which could have unusual properties. Hence, in this work we present the synthesis of Ta2O5 nanorods by sol gel method using DNA as structure directing agent, the size of the nanorods was of the order of 40 to 100 nm in diameter and several microns in length; this easy method can be useful in the preparation of nanomaterials for electronics, biomedical applications as well as catalysts.
Synthesis of Nanocarbon Materials by Carburization of Nanocrystalline Iron
Authors: Narkiewicz U. , Arabczyk W. , Kucharewicz I. , Wozniak M.J. , Matysiak H. , Kurzydlowski K.J. 
Published: June 2019

AbstractTwo products are formed in the process of carburization of iron with hydrocarbons: iron carbide (Fe3C, cementite) and in the next stage - carbon deposit. This paper deals with the formation of carbon deposit on nanocrystalline iron from ethylene decomposition and the reduction of its product with hydrogen.The carburization process was controlled using spring thermobalance. The samples after carburization contained cementite and some amount of carbon deposit in the form of carbon nanofibers and carbon nanotubes. In the next step iron carbide had been reduced under hydrogen flow at 400 – 500°C and pure iron was obtained. Some carbon was hydrogenated and the morphology of the remaining carbon deposit was changed – thicker carbon nanofibers were eliminated and thinner carbon nanotubes remained.The samples after carburization and reduction processes were characterized using XRD (X-rays Diffraction) and HRTEM (High Resolution Transmission Electron Microscopy) methods.
A Novel Spray Based Method for the Production of Semiconductor Nanocrystals
Authors: Amirav Lilac , Lifshitz Efrat 
Published: June 2019

AbstractWe present a novel spray based method for the formation and production of semiconductor nanocrystals that provides an attractive alternative to the commonly used epitaxial and colloidal procedures. According to this spray-based method, mainly thermospray, solutions of semiconductor salts are first sprayed into monodispersed droplets, which subsequently become solid nanoparticles by solvent evaporation. A semiconductor nanoparticle is produced from a single spray droplet upon the full vaporization of the solvent. The average diameter and size distribution of the final nanocrystals are controlled and determined by the solute concentration of the sprayed solution and by the droplet size, hence by the spray production parameters. The spray-produced nanocrystals are collected on any selected solid support. Representative results, shown in this paper, reveal the formation of CdS nanocrystals in the size range of 3 to 6 nanometer and with a size distribution of as low as five percents. A further structural analysis of these nanocrystals showed that they were formed in the zinc blend phase with high degree of crystallinity.
Growth and Characterization of [001] ZnO Nanorod Array on ITO Substrate with Electric Field Assisted Nucleation
Authors: Kim Young Jung , Shang Huamei , Cao Guozhong 
Published: June 2019

AbstractThis paper reports direct growth of [001] ZnO nanorod arrays on ITO substrate from aqueous solution with electric field assisted nucleation, followed with thermal annealing. Xray diffraction analyses revealed that nanorods have wurtzite crystal structure. The diameter of ZnO nanorods was 60 ∼ 300 nm and the length was up to 2.5 μm depending on the growth condition. Photoluminescence spectra showed a broad emission band spreading from 500 to 870 nm, which suggests that ZnO nanorods have a high density of oxygen interstitials. Low and nonlinear electrical conductivity of ZnO nanorod array was observed, which was ascribed to non-ohmic contact between top electrode and ZnO nanorods and the low concentration of oxygen vacancies.
Synthesis of TiO2 Nanoparticles Using Chemical Vapor Condensation
Authors: Wu Jie , Bai Guo-Ren , Eastman Jeffrey A. , Zhou Guangwen , Vasudevan Vijay K. 
Published: June 2019

AbstractNano-sized TiO2 particles are of interest for many applications, including use as photocatalysts and in heat transfer fluids (nanofluids). In the present study, TiO2 nanoparticles with controllable phase and particle size have been obtained through homogeneous gas-phase nucleation using chemical vapor condensation (CVC). The phase and particle size of TiO2 nanoparticles under various processing conditions have been characterized using x-ray diffraction and transmission electron microscopy. Chamber temperature and pressure were found to be two key parameters affecting particle phase and size. Pure anatase phase was observed for synthesis temperatures as low as 600 °C with chamber pressure varying from 20-50 Torr. When the furnace temperature was increased to 1000 °C at a pressure of 50 Torr, a mixture of anatase and rutile phases was observed, with the predominant phase being anatase. The average particle size under all the experimental conditions was observed to be less than 20 nm.
N-alkyldithiocarbamato complexes [Cd(S2CNHR)2] (R = C2H5, C4H9, C6H13, C12H25); Synthesis, Characterisation and Deposition of II/VI Nanoparticles.
Authors: Memon A. A. , Malik M. A. , Afzaal M. , O'Brien P. 
Published: June 2019

AbstractA series of N-alkyldithiocarbamato complexes of cadmium have been synthesised and characterized. [Cd(S2CNHC12H25)2] complex was used as a single source precursor to synthesize CdS nanoparticles. Synthesis of CdS nanoparticles was carried out at various thermolysis temperatures and concentration of the precursor to observe the morphological changes. At moderate or high temperature the 1D nanostructures (single-rods, bend rods or multi-rods) are generated. The shape of CdS nanocrystals varied from longer rods to shorter rods with increased width (average size: 4nm wide and 27nm long vs. 9nm wide and 27nm long) by simply increasing the quantity of precursor in the bulk solution from 0.05g/8ml HDA to 1g/8ml HDA at 250°C.
Mechanical Behavior of a Tri-modal Al Matrix Composite
Authors: Ye Jichun , Han Bing Q. , Tang Feng , Schoenung Julie M. 
Published: June 2019

AbstractMechanical milling at cryogenic temperatures (cryomilling) was applied to fabricate a composite powder with 20 wt. % B4C (submicron-to-several microns in size) in a nanocrystalline (NC) 5083 Al matrix. A uniformly blended powder with 50 wt. % cryomilled composite powder and 50 wt. % coarse-grained (CG) 5083 Al powder was degassed, cold isostatic pressed (CIPped) and extruded to form a composite with 10 wt. % B4C, 50 wt. % CG 5083 Al and balance NC 5083 Al. This tri-modal material was then tested for mechanical behavior under compressive and tensile load conditions at various temperatures. The composite exhibited an extremely high yield stress at room temperature, but limited ductility. Although the composite lost its strength at elevated testing temperatures rapidly, the retained strength was still much higher than that of the conventional 5083 Al. The composite exhibits its highest ductility of 26% at 200°C under tensile load. In compression, it plastically deformed uniformly at all the elevated temperatures (≥373 K) and did not fracture even when the deformation exceeded 30%. The microstructure of this composite, including the distribution of each phase, the grain sizes of the Al matrix, the interfaces between these three phases, and the fracture surfaces were characterized using transmission electron microscopy (TEM) and optical microscopy (OM) techniques. The relationship between the microstructures and mechanical properties was discussed.
Nanoconfinement Effect on the Mechanical Behavior of Polymer Thin Films
Authors: Zhou J. , Komvopoulos K. 
Published: June 2019

AbstractNanoimprint is one of the most promising fabrication techniques for nanoelectronics. The main feature of this process is the compression of a thin film of a polymer resist by a rigid mold to produce a surface pattern. Hence, nanoimprint is essentially a mechanical forming process that depends greatly on the nanoscale mechanical behavior of the plastically deformed polymer film. Consequently, basic understanding of nanoimprint mechanics is imperative for improving pattern quality, reproducibility, and automation. The objective of this study was to elucidate the mechanical response of thin polymer films subjected to nanoindentation loading. Three deformation regimes were identified in the experiments performed with poly(methyl methacrylate) (PMMA) films of thickness in the range of 200-400 nm with a Berkovich tip of nominal radius of curvature equal to 100 nm. A three-layer model consisting of surface, intermediate, and interface layers was introduced to explain the mechanical response of the indented PMMA films. The spatial constraints imposed to the plastic flow of the interface layer by the rigid indenter and substrate surfaces produce a dynamic effect, demonstrated by the loading rate dependence of the deformation response. This phenomenon is of great importance to polymer plastic flow in nanoimprinting.
Germanium Nanocrystals Embedded in Sapphire
Authors: Xu Q. , Sharp I.D. , Liao C.Y. , Yi D. O. , Ager J.W. , Beeman J.W. , Yu K.M. , Chrzan D. C. , Haller E.E. 
Published: June 2019

Abstract74Ge nanocrystals are formed in a sapphire matrix by ion implantation followed by thermal annealing. Transmission electron microscopy (TEM) of as-grown samples reveals that the nanocrystals are faceted and have a bi-modal size distribution. Notably, the matrix remains crystalline despite the large implantation dose and corresponding damage. Embedded nanocrystals experience large compressive stress relative to bulk, as measured by Raman spectroscopy of the zone center optical phonon. In contrast, ion-beam-synthesized nanocrystals embedded in silica are observed to be spherical and experience considerably lower stresses. Also, in situ TEM reveals that nanocrystals embedded in sapphire melt very close to the bulk melting point (Tm= 936 °C) whereas those embedded in silica exhibit a significant melting point hysteresis around Tm.
Multiscale Modeling of Strengthening Mechanism in Aluminum-Based Amorphous Nanocomposites
Authors: Liu H. T. , Sun L. Z. 
Published: June 2019

AbstractIn this work we focus upon theoretical exploration of the mechanical constitutive behavior of amorphous nanocomposites in terms of a multi-scale approach starting from the nanostructure. Local heterogeneous stress field and deformation are calculated based on the concept of eigenstrain and equivalent inclusion method. The overall elastoplastic constitutive model for amorphous nanocomposites is developed through homogenization averaging procedures. Explicit expressions of the effective elastic stiffness and yield strength of amorphous nanocomposites in terms of the constituents' properties and nanostructures are obtained. An interlayer phase between nanoparticles and the amorphous matrix is experimentally observed and incorporated in the proposed model. The interlayer thickness is treated as a characteristic length scale. Thus, the particle size effect on the nanocomposite properties is particularly investigated within continuum nanomechanics framework. It provides direct determination of the intrinsic mechanisms of the nanocomposite structure-property relationship at the nanoscale.
Determination of the Modulus and Hardness of Spin-on Zeolite Low-K Thin Films
Authors: Johnson Mark , Li Zijian , Yan Yushan , Wang Junlan 
Published: June 2019

AbstractWith the semiconductor technologies continuously pushing the miniaturization limits, there is a growing interest in developing novel low dielectric constant (low-k) materials to replace traditional dense SiO2 based insulators. In order to survive the multi-step integration process and provide reliable material and structure for the desired integrated circuit (IC) functions, the new low-k materials have to be mechanically strong and stable. Thus the material selection and mechanical characterization are vital in the successful development of next generation low-k dielectrics. A new class of low-k dielectric materials, nanoporous pure-silica zeolite, is prepared in thin films using IC compatible spin coating process and characterized using depth sensing nanoindentation technique. The elastic modulus measurements of the zeolite thin films are found to be significantly higher than that of other porous silicates with similar porosity and dielectric constants. Correlations of the mechanical, microstructural and electrical properties are discussed in detail.
Effect of Pile-up in Nanoindentation of Micro and Nano crystalline Ni using FEM
Authors: Pothapragada Raja Mahesh , Mirshams Reza A. , Vadlakonda Suman 
Published: June 2019

AbstractA much better understanding of the contact mechanics can be obtained through finite element modeling. The experimentally determined tip shape function was included to reproduce the same contact area for a given contact depth as in the experiment. The fundamental material properties affecting pile-up are the ratio of the effective modulus to yield stress Eeff/Y and the work hardening rate.
Deformation behavior and strain rate sensitivity of nanostructured materials at moderate temperatures
Authors: Duhamel Cécilie , Guérin Sandrine , Hÿtch Martin , Champion Yannick 
Published: June 2019

AbstractStrain-rate jump tests in compression are carried out on nanostructured copper (grain size = 90 nm) at moderate temperatures (353K - 393K). Strain-rate sensitivity m is measured as a function of temperature, T, and strain rate, έ. Increasing temperature or decreasing strain rate induces an increase in the strain-rate sensitivity. For (έ, T) = (1×10-5 s-1, 393K), m is equal to 0.17 which is the highest value reported for nanocrystalline copper. These results of enhanced m are encouraging in terms of gain in ductility. The measurements emphasize the existence of a thermally activated mechanism different from the normal rate-controlling process observed for microcrystalline fcc metals.
Fabrication and Characterization of Cold Rolled Ni/Al Multilayer Foils
Authors: Qiu Xiaotun , Graeter Jesse Harris , Kecskes Laszlo , Wang Jiaping 
Published: June 2019

AbstractNi/Al reactive multilayer foils were fabricated by cold rolling method and self-propagating reactions in these foils were investigated. A two-stage phase formation process was observed in the ignition experiment. The first step is the lateral growth of Al3Ni phase from isolated nucleation sites and the following coalescence into a continuous layer; the second step is the growth of such Al3Ni layers in the perpendicular direction of the interface until all Al is consumed. As there is still Ni available, Al3Ni will continuously react with Ni until no Ni is left, and the final reaction product turns out to be ordered B2 AlNi compound. X-ray diffraction (XRD) experiments showed that the reaction product of the cold rolled foil was the same as the physical vapor deposition (PVD) foil. The reaction process was studied by differential scanning calorimetry (DSC). Three peaks can be identified from the DSC curve. Cold rolled foils were heated to different peak temperatures obtained from DSC curve with the same heating rate as DSC. XRD results for such foils showed that the first two peaks were the exothermic formation of Al3Ni, while the last one was for the formation of AlNi. The enthalpy of the reaction for the cold rolled foil was calculated to be -57.5 KJ/mol, which was in good agreement with the formation enthalpy of AlNi (-59 KJ/mol). The reaction velocities of the first formation stage were measured to be 7mm/s for cold rolled foils, which were much smaller than the reaction velocities of PVD foils (which range between 1-30 m/s).
Controlling Residual Stress in Metal Matrix Ceramic Fiber Composite
Authors: Al-Haik Marwan , Garmestani Hamid , Haik Yousef 
Published: June 2019

AbstractIn metal matrix composites the nature of the reinforcement can influence the development of residual stresses not only as a result of the mismatch in the thermal expansion coefficient between the fiber and the matrix but also caused by the interface of the materials during the processing cycles. The residual stress can be minimized through controlling the processing path and the thermal environment. We studied the residual stress formation and evolution in gamma titanium aluminide (Ti-47AL-2Ta) matrix. The matrix was reinforced with three different types of fibers: Alumina, Sapphikon, and Tiboride through hot isostatic pressing. The composite was heat treated for various combinations of time: 100, 200 and 500 hours; and temperature: 590&#61616;C, 815&#61616;C and 982 &#61616;C respectively. Residual stresses were measured in the gamma phase of the matrix using X-Ray diffraction
Processing-Microstructure-Property Relations in Anisotropic Thermal Sprayed Composites
Authors: Chi Weiguang , Srinivasan Vasudevan , Sharma Atin , Sampath Sanjay , Gambino Richard 
Published: June 2019

AbstractThermal spray is a significantly advanced but inherently complex deposition process that involves successive impingement of molten droplets on a substrate to form coating with a ¡°brick-wall¡± layered structure. The anisotropic microstructure of coatings is very sensitive to processing conditions and has significant influence on the properties. This study aims to understand the processing-microstructure-thermal property correlation of thermally sprayed coatings. Thermal transport properties of three coating systems forming composites with pores (yttria stabilized zirconia (YSZ) -Air), a second phase (Mo-Mo2C) and a graded material (YSZ-NiCrAlY) are interpreted from the point of view of microstructure and chemical composition. In the case of YSZ-Air composite, results indicate that porosity contribution from 20-35% decreases the thermal conductivity by 50-70% of the bulk value. For the intrinsic composite of Mo and Mo2C, which coexist as stable phases, thermal conductivity increases significantly with 1.75wt% carbon addition since it reduces formation of MoO2 during processing, but decreases with 3.5wt% carbon addition. This is attributed to larger carbide retention in the latter. For the discrete layered and graded composites of YSZ-NiCrAlY, which are made up of varying fractions of these two constituents, thermal conductivity decreases sharply up to 40wt% YSZ and then more gradually with increasing YSZ content. This paper examines these experimental findings by treating the these complex coatings as multiphase composites.
Properties of Transparent Conductive Oxide Films on Flexible Substrates
Authors: Hsiao Shih Hsiu , Tanaka Yoshikazu , Ide-Ektessabi Ari 
Published: June 2019

AbstractTransparent conductive oxide (TCO) thin films are extensively used in display industry and they can be utilized for flexible displays. The polymer and the plastic materials used as flexible substrates are more bendable and lighter weight compared to glass substrates. However, its mechanical and surface properties differed from glass substrates result in different quality of TCO layers deposited on it. In this study, Polyethylene Terephthalate (PET) and glass were used as substrates. Indium Tin Oxide (ITO), Zinc Oxide (ZnO), Mg-doped ZnO (MZO), Al-doped ZnO (AZO), Ga-doped ZnO (GZO), Al-doped MZO (AMZO), Ga-doped MZO (GMZO) were used as TCO materials deposited by RF sputtering. Rutherford Backscatter Spectroscopy (RBS) and X-Ray Diffraction (XRD) were used to analyze the chemical composition and crystal structure of TCO thin films. Light transmittance and surface resistivity were measured after the different deposited conditions. , Mg-, Al-, Ga- doped ZnO indeed modified the optical properties of ZnO and better than ITO. However, the electrical conductivity was not improved obviously compared to ITO when they deposited on PET substrate at room temperature.