bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improved Tribological Properties of Diamondlike Carbon/Metal Nanocomposites
Authors: Narayan Roger J. , Scholvin Dirk 
Published: April 2011

ABSTRACTOne of the many forms of carbon, diamondlike carbon (DLC), consists mainly of sp3-bonded carbon atoms. DLC coatings possess properties close to diamond in terms of hardness, atomic bonding, and chemical inertness. Unfortunately, DLC exhibits poor adhesion to metals and polymers. The adhesion of the DLC film is determined by internal stresses in the film and by interfacial bonding. This work involves processing, characterization and modeling of diamondlike composite films on metal and polymer substrates to improve adhesion and wear properties. A novel target design was adopted to incorporate metal (silver or titanium) atoms into DLC films during pulsed laser deposition. STEM of the DLC/metal nanocomposites has shown that the metals that do not form carbides (e.g., silver) form 2–10 nm inclusions within the DLC matrix. Wear resistance measurements made on these samples have demonstrated that DLC/metal nanocomposites possess exceptional wear resistance. Diamond-like carbon nanocomposites also exhibit significantly enhanced adhesion. Careful analysis of the Raman data also indicated a significant shift to shorter wavelength in DLC nanocomposite films, indicating a reduction in compressive stress within these films. The sp3 content of these films was studied using electron energy loss spectroscopy (EELS). By varying the metal concentration as a function of distance from the interface, we have created functionally gradient DLC nanocomposites. These DLC/metal nanocomposite coatings have multiple biomedical applications.
Characterization of Porous Silicate Low-k Films by Ellipsometric Porosimetry and Variable-energy Positron Annihilation Spectroscopy
Authors: Ito Kenji , Kobayashi Yoshinori , Suzuki Ryoichi , Ohdaira Toshiyuki , Yu Runsheng , Sato Kiminori , Hirata Kouichi , Togashi Hisashi , Egami Miki , Arao Hiroki , Nakashima Akira , Komatsu Michio 
Published: April 2011

ABSTRACTWe a pplied ellipsometric porosimetry and variable-energy positron annihilation spectroscopy to the pore characterization of spin-on-glass silicon-oxide-backboned porous thin films with different relative dielectric constants between 2.3 and 3.2. It was found that the relative dielectric constant decreases linearly with increasing open porosity deduced by ellipsometric porosimetry. Comparison of the open porosity with the average pore size deduced by positron annihilation lifetime spectroscopy suggested that mesopores less contribute to open porosity and are not so effective in decreasing film relative dielectric constant in comparison with micropores.
Mesoporous Silica Film Preparation by Novel Supercritical Fluid Extraction of Organic Templates
Authors: Kawakami Nobuyuki , Hirano Takayuki , Fukumoto Yoshito , Nagase Yoshiyuki 
Published: April 2011

ABSTRACTSupercritical fluid extraction (SFE) technique which enables to fabricate mesoporous film at low temperature has been developed. Meso-structure silica films are prepared by sol-gel process based on the self-organization of surfactant templates, and the organic templates are successfully extracted from the films by supercritical CO2 (sc-CO2) modified with hydrogen peroxide at 80 °C and 19.6 MPa. The extraction process is analyzed by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy of the films. In order to discuss the feasibility of such films obtained at low temperature for electronics applications with low dielectric and low dielectric loss, the mechanical properties and the densities of the films are compared with various silica films prepared by different method.
Synthesis and Characterization of Novel Organic-Inorganic Nancomposite Coatings
Authors: Mosher Brian P. , Zeng Taofang 
Published: April 2011

ABSTRACTIn this paper, we report the synthesis and characterization of three novel water-based nanocomposite coatings. Throughout the paper, these coatings will be referred to as coatings 1, 2 and 3. The coatings are silica-based and are sol-gel derived using surfactant assemblies, with aluminum perchlorate as a catalyst. After synthesis, curing causes cross-link polymerization of silica, forming Si-O-Si network. The formation of this 3-Dimensional network can be verified using Fourier Transform Infrared Spectroscopy (FTIR) and Transmission Electron Microscopy (TEM). Incorporating metal oxide nanoparticles gives the material unique properties.
Reptation in Artificial Tubes and the Corset Effect of Confined Polymer Dynamics
Authors: Kimmich Rainer , Fatkullin Nail , Fischer Elmar , Mattea Carlos , Beginn Uwe 
Published: April 2011

ABSTRACTA spinodal demixing technique was employed for the preparation of linear poly(ethylene oxide) (PEO) confined to nanoscopic strands which in turn are embedded in a quasi-solid and impenetrable methacrylate matrix. Both the molecular weight of the PEO and the mean diameter of the strands are variable to a certain degree. Chain dynamics of the PEO in the molten state was examined with the aid of field-gradient NMR diffusometry (time scale: 10−2 s … 100 s) and field-cycling NMR relaxometry (time scale: 10−9 s … 10−4 s). The dominating mechanism for translational displacements probed in the nanoscopic strands by either technique is shown to be reptation. A corresponding evaluation formalism for NMR diffusometry is presented. It permits the estimation of the mean PEO strand diameter. Depending on the chemical composition of the matrix, the diameters range from 9 to 58 nm. The strands were visualized by electron microscopy. On the time scale of spin-lattice relaxation time measurements, the frequency dependence signature of reptation, that is T1 ∝ ν3/4, showed up in all samples. A “tube” diameter of only 0.6 nm was concluded to be effective on this time scale even when the strand diameter was larger than the radius of gyration of the PEO random coils. This “corset effect” is traced back to the lack of the local fluctuation capacity of the free volume in nanoscopic confinements. The confinement dimension is estimated at which the cross-over from “confined” to “bulk” chain dynamics is expected.
Poly(methyl phenyl siloxane) in Random Nanoporous Glasses: Molecular Dynamics and Structure
Authors: Schönhals Andreas. , Goering Harald. , Schick Christoph , Frick Bernhard. , Zorn Reiner 
Published: April 2011

ABSTRACTThe effect of a nanometer confinement on the molecular dynamics of poly(methyl phenyl siloxane) (PMPS) was studied by dielectric spectroscopy (DS), temperature modulated DSC (TMDSC) and neutron scattering (NS). DS and TMDSC experiments show that for PMPS in 7.5 nm pores the molecular dynamics is faster than in the bulk which originates from an inherent length scale of the underlying molecular motions. At a pore size of 5 nm the temperature dependence of the relaxation times changes from a Vogel / Fulcher / Tammann like behavior to an Arrhenius one. At the same pore size Δcp vanishes. These results give strong evidence that the glass transition has to be characterized by an inherent length scale of the relevant molecular motions. Quasielastic neutron scattering experiments reveal a strong change even in the microscopic dynamic.
Modeling the Contact Stiffness Between a 2D Voronoi Honeycomb and a Flat Rigid Surface
Authors: Widdle Richard D. , Farris Thomas N. , Bajaj Anil K. , Davies Patricia 
Published: April 2011

ABSTRACTOpen-cell foam can be thought of as a network of interconnected struts. To study the contact stiffness behavior, one can imagine the foam boundary to be characterized by struts that are free at one end, while the base-end is connected to the interior of the foam. In previous studies, the base-end was assumed to be built into a rigid surface, i.e., the surface struts were constrained to have zero displacement where they would connect to the foam interior. In this study the assumption that the surface elements are built-in is relaxed by modeling the elastic behavior of the foam interior. The foam interior is modeled as a network of struts within a finite element formulation. The analysis is simplified by considering two-dimensional honeycomb structures. It is found that including the foam interior in the model results in a significant reduction in the predicted contact stiffness.
Nanoindentation of silicon: hardness and semiconductor-metal phase transition
Authors: Hebbache M. 
Published: April 2011

ABSTRACTThe hardness of a thin film of silicon is studied in the framework of the 3D Hertzian contact theory. The anisotropy and the anharmonicity of silicon are taken into account for the first time. It is shown that the contribution of plasticity to the hardness of silicon is significant while we know that it possesses strong covalent bonds and dislocations must be thermally activated in this material. The semiconductor-metal phase transition, driven by the tetragonal shear strain superimposed on the non-hydrostatic pressure generated by a diamond indenter, is also studied. For this aim, the Landau theory of phase transitions and the contact theory are combined. The comparison with available nanoindentation experiments is made.
A Study on the Microstructure of the Nano Concrete Composite Materials
Authors: Changa Ping-Kun , Houb Wei-Ming , Hwang Chao-Lung 
Published: April 2011

ABSTRACTThis study applies NMR, SRA, MIP, SEM and electric resistance tests to examine the microstructure of the composite materials of nano concrete. The test results show that owing to the pozzolanic reaction activated by the nanopowders, the CaOH2 content within the composite materials is decreasing, filling the capillary and gel pores. This way, the microstructure of the composite materials is transformed in its arrangement, which makes concrete much more well-mixed and densified, enhancing the compressive strength. The permeability is cut down as well. In conclusion, it ends in much better durability.
Effect of Surface Treatments on the Structural and Mechanical Properties of Nanostructured Diamond Coatings on Tungsten Carbide Cutting Tools
Authors: Vohra Vaibhav , Catledge Shane A. , Vohra Yogesh K. 
Published: April 2011

ABSTRACTChemical Vapor Deposition (CVD) using hydrogen, methane, and nitrogen feed gases has proven to be useful in depositing well-adhered diamond films on metal substrates. These films have already found a market in the cutting tool industry as coatings on cobalt-cemented tungsten carbide (WC-Co) inserts. The purpose of this investigation is to examine how the thermal and chemical pre-treatments typically used for carbide inserts (to remove the cobalt binder near the surface) affect the structure and interfacial adhesion of the diamond coating. Removal of the cobalt binder phase in various pre-treatment methods has been shown to minimize its catalytic effect of graphite formation during diamond deposition by CVD. The diamond-coated inserts in our study were characterized using x-ray diffraction, Raman spectroscopy, atomic force microscopy, and Rockwell indentation testing. We use an unconventionally high methane concentration in the feedgas in order to saturate the growth surface with carbon, thereby limiting cobalt migration from the bulk to the surface and reducing the dissolution and diffusion of carbon atoms coming from the plasma. Nitrogen is used in the feedgas in order to provide a tough, single-layer nanocrystalline diamond film structure. In addition, a multi-layer (nano-/micro-/nano-crystalline) CVD diamond film was grown by controlling the flow of nitrogen in order to show its characteristics in comparison with the single layer nanocrystalline diamond film. The multilayer film on the thermally-treated insert shows enhanced interfacial adhesion and fracture toughness when compared to other pretreatments and diamond coatings. This was demonstrated by indentation tests using 1470 N load.
Electrical Properties of Rutile Single Crystal Irradiated by High-Fluence-Reactor-Neutron
Authors: Lu Tiecheng , Lin Libin , Cheng Gang , Xu Xuechun , Zhao Chunpei , Tian Yunfei 
Published: April 2011

ABSTRACTElectrical properties of rutile (TiO2) single crystals irradiated by high-fluence-reactor neutrons have been investigated for the first time. In this paper, the colorless rutile single crystal turns into dark blue after being irradiated by high-fluence-reactor neutrons of 1019/cm2 and its electrical properties change, from high insulator to normal semiconductor. The relationship of sample resistance to temperature (at low temperature, room temperature and high temperature, respectively) and the effect of annealing atmosphere (in air or in vacuum) on the electrical property of the sample have been studied. The results show that the sample has semiconductor properties at low temperature. At high temperature, however, it is oxidized into colorless insulator in air and the activation energy gradual changes due to slow oxidization process. In 10-4 Pa vacuum condition, TiO2 becomes a semiconductor due to the presence of ion defects. The electrical conductance mechanism is also discussed.
The influence of the deposition energy on thin film formation: Co on Si(111)
Authors: Vanormelingen Koen , Degroote Bart , Vantomme André 
Published: April 2011

ABSTRACTThe deposition of a thin film on a substrate surface can be achieved with a wide variety of techniques. Deposition using low energy ion beams is not a common technique, but it yields promising features, due to the hyperthermal nature of the deposited ions. With low energy ion deposition, it is possible to grow films with good characteristics at significantly lower temperatures compared to thermal deposition. The quality of these films critically depends on the energy of the impinging ions. We investigated the influence of the energy on the surface morphology for the deposition of Co onto Si(111). The roughness of this surface decreases significantly when the ion energy is increased, until it reaches a minimum at 25 eV. When the ion energy is further increased, the surface roughness increases again. This behavior can be explained by taking into account the interplay between the beneficial and detrimental effects due to the ion energy. Beneficial effects such as enhanced mobility and improved layer-by-layer growth cause a decrease in surface roughness when the deposition energy is increased from thermal to 25 eV. For energies above that value, undesirable effects such as defect creation and pileup dominate, leading to an increase in surface roughness. This study shows that low energy ion deposition can be used to improve the surface quality of a thin film by choosing the optimal deposition energy.
Dynamic Recovery in Au Ion Irradiated Gallium Nitride
Authors: Jiang W. , Weber W. J. , Wang L. M. , Sun K. 
Published: April 2011

ABSTRACTGallium nitride single crystals were irradiated using energetic Au2+ ions to two fluences at room temperature. Two different damage levels and depth profiles that are characterized by near-surface damage accumulation and deeper-region damage saturation were produced. Thermal annealing at 873 K resulted in disorder recovery only in the near-surface region at low fluence. However, simultaneous irradiation with 5.4 MeV Si2+ ions during annealing at 873 K induced significant recovery over the entire damage profile at both low and high fluences. Results from high-resolution transmission electron microscopy show recovery of the crystal structure in the highly disordered surface region following the Si2+ ion irradiation. The irradiation-assisted recovery is primarily attributed to defect-stimulated recovery and epitaxial recrystallization processes due to the creation of mobile Frenkel pairs.
Application of High Energy Ion Beam on the Control of Boron Diffusion
Authors: Chu Wei-Kan , Shao Lin , Liu Jiarui 
Published: April 2011

ABSTRACTAnomalous diffusion of boron during annealing is a detriment on the fabrication of ultrashallow junction required by the next generation Si devices. This has driven the need to develop new doping methods. In the point defect engineering approach, high-energy ion bombardments inject vacancies near the surface region and create excessive interstitials near the end of projected range of incident ions. Such manipulation of point defects can retard boron diffusion and enhance activation of boron. We will review the current understanding of boron diffusion and our recent activities in point defect engineering.
Local Modification of Microstructure and of Properties by FIB-CVD
Authors: Wanzenboeck H. , Harasek S. , Langfischer H. , Basnar B. , Brezna W. , Smoliner J. , Bertagnolli E. 
Published: April 2011

ABSTRACTThe focused ion beam has been acknowledged as a versatile tool for local sputtering as well as local deposition of material. A beam diameter below 10 nm is feasible and renders FIB a powerful tool for microstructure fabrication and generation. This experimental study investigates the geometrical limitations of FIB processing as well as the implications on the processed material. The high energetic ions of the primary beam also change the properties of the processed material due to implantation and atomic mixing. The incorporation of Ga from the FIB may be beneficial in the case of deliberate implantation or unfavorable as a chemical impurity. Higher doses of ion irradiation caused amorphisation of the material. The effects of FIB processing on the substrates as well as deposited structures are illustrated.
Preparation of Ge (100) Substrates for High-Quality Epitaxial Growth of Group IV Materials
Authors: Nowakowski Mark , Bandaru Jordana , Bell L.D. , Nikzad Shouleh 
Published: April 2011

ABSTRACTWe compare various wet chemical treatments, in preparing high-quality Ge (100) surfaces suitable for molecular beam epitaxy (MBE). Various surface treatments are explored such as UV-ozone treatment followed by exposure to chemical solutions such as de-ionized (DI) water, hydrofluoric acid (HF), or hydrochloric acid (HCl). Chemical treatments to remove the oxide are performed in a nitrogen environment to prevent further formation of surface oxide prior to surface analysis. Following chemical treatments, in situ reflection high-energy electron diffraction (RHEED) analysis is performed to observe the surface evolution as a function of temperature. In a separate chamber, we analyze each sample, before and after chemical treatment by x-ray photoelectron spectroscopy (XPS) to directly determine the oxide desorption following each chemical treatment. Our results of this comparative study, the effectiveness of each chemical treatment, and the stability of the passivated surface suggest that UV ozone cleaning, followed by 10% HCl is the best choice for removing most of the oxide. Furthermore, we present evidence of high quality epitaxial growth of SnxGe1−x on wafers prepared by our method.
Charging effects in Si quantum dots for Non Volatile Memories applications monitored by Electrostatic Force Microscopy
Authors: Puglisi R.A. , Nicotra G. , Lombardo S. , Spinella C. , Ammendola G. , Gerardi C. 
Published: April 2011

ABSTRACTNanoscale structures have been recently proposed as charge storage nodes due to their potential applications for future nanoscale memory devices. Our approach is based on the idea of using Si nanodots as discrete floating gates. To experimentally investigate such potential, we have fabricated MOS structures with Si nanocrystals. The dots have been deposited onto an ultra-thin tunnel oxide by chemical vapour deposition, and then annealed at 1000 °C for 40 s, to crystallize all the dots. After deposition the dots have been covered by a CVD SiO2 layer, thus resulting in dots completely embedded in stoichiometric silicon oxide. The nanocrystal density and size have been studied by energy filtered TEM (EFTEM) analysis. An electrostatic force microscope has been used to locally inject the charge. By applying a relatively large tip voltage a few dots have been charged, and the shift in the tip phase has been monitored. The shift in the phase is attributed to the presence of the charge in the sample. A comparison between n and p type samples is also shown.
(In,Ga)As Quantum Dot Array Formation by Self-Organized Anisotropic Strain Engineering of an (In,Ga)As/GaAs Quantum Wire Template: Shallow-Pattern Effects
Authors: Mano T. , Nötzel R. , Hamhuis G. J. , Eijkemans T. J. , Smalbrugge E. , Wolter J. H. 
Published: April 2011

ABSTRACTOne-dimensional (In,Ga)As quantum dot (QD) arrays are formed on planar singular and shallow-patterned (mesa gratings) GaAs (100) substrates by self-organized anisotropic strain engineering of an (In,Ga)As/GaAs quantum wire (QWR) superlattice (SL) template in molecular beam epitaxy. On planar singular substrates, highly uniform one-dimensional single QD arrays, which are extended over 10 μm length, are realized with efficient photoluminescence. The shallow mesa gratings along [0–11] and [011] induce two different types of steps which differently affect the surface migration processes crucial for QWR template development, i.e., strain driven In adatom migration along [011] and surface reconstruction induced adatom migration along [0–11]. While type-A steps along [0–11] have no significant effect on the adatom migration along [011] and [0–11], type-B steps along [011] hinder the surface reconstruction induced migration along [0–11] to prevent formation of QWR and ordered QD arrays.
Systematic studies of SiGe/Si islands nucleated via separate in situ, or ex situ, Ga+ focused ion beam-guided growth techniques
Authors: Vandervelde T. E. , Atha S. , Pernell T. L. , Hull R. , Bean J.C. 
Published: April 2011

ABSTRACTIn this study we use 25keV in situ and 30keV ex situ Ga+ focused ion beams (FIB) to locally modify the substrate before deposition to determine its affect on nucleation of MBE-grown Ge/Si islands. FIB processing may alter island formation in at least four ways: the surfactant effect of Ga+, doping effects of subsurface Ga+, crystalline damage, and surface roughening. To explore these possibilities, we milled square regions of increasing Ga+ doses and used AFM to monitor islanding in and around these regions. For in situ experiments, doses ranged from ∼1013 to 5×1017ions/cm2. We began to observe changes in island topology at doses as low as ∼1014ions/cm2. For doses of ∼1015ions/cm2 to ∼8×1016ions/cm2, implanted areas were surrounded by denuded zones that grew from ∼0.5 to 6 μm. Immediately inside the implanted area, island concentration (size and density) appeared to peak. At doses above ∼6×1016ions/cm2, Ga+ produced noticeable surface depressions, which were often surrounded by enhanced island densities, rather than a denuded zone. For ex situ FIB patterning, samples underwent both pre-growth cleaning and growth of a thin capping layer. Doses ranging from 7.5×1013 to ∼1017 ions/cm2 were used with varied capping layer thicknesses to study their combined affect on island nucleation. The results correspond well with in situ experiments for thin capping layers. Increased capping layer thickness show muted modifications for low Ga+ doses, while for higher doses trends similar to the in situ results are seen.