bluuebunny/crossref_metadata_2025 huggingface dataset:
Developing Nanoscale Materials Using Biomimetic Assembly Processes
Authors: Bachand George D. , Rivera Susan B. , Boal Andrew K. , Bauer Joseph M. , Koch Steven J. , Manginell Ronald P. , Liu Jun , Bunker Bruce C.
Published: April 2011

The formation and nature of living materials are fundamentally different from those of synthetic materials. Synthetic materials generally have static structures, and are not capable of adapting to changing environmental conditions or stimuli. In contrast, living systems utilize energy to assemble, reconfigure, and dismantle materials in a dynamic, highly non-equilibrium fashion. The overall goal of this work is to identify and explore key strategies used by living systems to develop new types of materials in which the assembly, configuration, and disassembly can be programmed or “self-regulated” in microfluidic environments. As a model system, kinesin motor proteins and microtubule fibers have been selected as a means of directing the transport of molecular cargo, and assembly of nanostructures at synthetic interfaces. Initial work has focused on characterizing and engineering the properties of these active biomolecules for robust performance in microfluidic systems. We also have developed several strategies for functionalizing microtubule fibers with metal and semiconductor nanoparticles, and demonstrated the assembly of composite nanoscale materials. Moreover, transport of these composite assemblies has been demonstrated using energy-driven actuation by kinesin motor proteins. Current work is focused on developing mechanisms for directing the linear transport of microtubule fibers, and controlling the loading/unloading of nanoparticle cargo in microfluidic systems.
Non-impact electrostatic micromanipulation by voltage sequence for time
Authors: Saito Shigeki , Takahashi Kunio , Urago Masataka
Published: April 2011

This paper proposes how to determine a voltage sequence for time to realize a non-impact electrostatic micromanipulation by kinetic control of a detached particle. The system consists of a manipulation probe, a spherical microparticle, and a substrate plate. These objects are all conductive. The particle initially sticks to the probe tip due to adhesional force and is detached by the applied voltage. The force on the particle, which is generated by electrostatic interaction, is evaluated through a boundary element method. Although the numerical method is used, all the parameters are normalized. Based on the evaluation, we propose the simple method by accelerating and decelerating voltage, and clearly express the conditions of voltage and time by considering the total work to the particle during its flight. The discussion about the time reveals the feasibility of the method from the viewpoint of the through-rate of a power-source.
Ellipsometry Measurement Accuracy of Gate Oxides under Polysilicon
Authors: Jiang Gary , Pelcher Don , Kwon Daewon , Clerico Jana , Collins George
Published: April 2011

Precisely controlling the thickness of ultrathin silicon dioxide (SiO2) gate dielectric films is critical for high yield advanced generation semiconductor manufacturing. Advanced methods for producing ultrathin gates deposit both the gate dielectric and the polysilicon (poly-Si) gate electrode in a single cluster tool. This avoids the opportunity for adsorption of molecular airborne contamination (MAC) between deposition of the two layers, but necessitates measuring gate oxide thickness through a thick poly-Si layer.

Variations in poly-Si grain size, amorphous silicon content, and roughness, make it very difficult to model the optical feedback in the visible spectral range to resolve ultrathin (10–20 Å) gate oxides with sufficient accuracy and repeatability for process control.

This paper studies the optical behavior of the poly-Si/dielectric filmstack from 190 nm to 900 nm and the physical properties of the poly-Si layer. A more accurate modeling method is proposed to characterize the poly-Si and its top roughness layer using effective medium approximation (EMA) models. Using the new model, both a spectroscopic ellipsometer (SE) and a multi-angle multi-wavelength laser ellipsometer (MWLE) were employed to measure wafers with different poly-Si and gate oxide thicknesses. TEM was used to characterize the film thickness while roughness was determined using AFM. Good correlation was obtained between the TEM, AFM, and ellipsometry results. Excellent repeatability (0.04 Å 1σ on a 15 Å gate oxide for 10 days) and across the wafer uniformity (0.2 Å 1σ for a 49-point map) were also achieved when measuring gate dielectric films under the poly-Si with the MWLE.
Effects of Softbake Parameters on a Benzocyclobutene (BCB) Adhesive Wafer Bond
Authors: Pascual Daniel N.
Published: April 2011

This study explores the effects of softbake parameters including temperature and duration on the homogeneity and toughness of a Benzocyclobutene (BCB) adhesive bond. Experiments were initially performed on silicon wafer pieces and then verified using quartered wafers bonded on a different machine. A four-point bend delamination test was employed to quantitatively measure interface toughness while uniformity was analyzed visually. A softbake temperature of 150 °C for 10 minutes yielded strong void-free bonds with an interface toughness of 23 J/m2.
Adhesion force and Nanotribological Characteristics of Chemical Vapor Deposited Fluorocarbon Films
Authors: Kim Nam-Kyun , Kim Tae-Gon , Park Jin-Goo , Kim Woon-Bae , Shin Hyung- Jae
Published: April 2011

In this study, Adhesion force and Nanotribological Characteristics of fluorocarbon (FC) films on Al deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) were evaluated. The contact angle of FC thin films on Al was measured to be around 110°. The surface energy was calculated to be 15 dynes/cm from the measurements of contact angles of polar and nonpolar solutions on surfaces. The contact angle hysteresis, which is an indicator for the surface heterogeneity, was lower than 30°. The friction force of FC films coated surfaces was three times lower than bare Al. The adhesion force of bare Al was measured to be around 9.6nN. The presence of FC films on Al reduced it to below 4nN. Fourier transform infra-red (FTIR) spectra showed the presence of fluorocarbon groups such as –CFn- and =CF=CF2.
Measurement of shape and deformation of MEMS at the wafer level
Authors: Furlong Cosme , Ferguson Curtis F. , Melson Michael J. , Pryputniewicz Ryszard J.
Published: April 2011

One of the approaches to fabrication of MEMS involves surface micromachining to define dies on single crystal silicon wafers, dicing of the wafers to separate the dies, and electronic packaging of the individual dies. Dicing and packaging of MEMS accounts for a large fraction of the fabrication costs, therefore, nondestructive evaluation at the wafer level, before dicing, can have significant implications on improving production yield and costs. In this paper, advances in development of optoelectronic holography (OEH) techniques for nondestructive, noninvasive, full-field of view evaluation of MEMS at the wafer level are described. With OEH techniques, quantitative measurements of shape and deformation of MEMS, as related to their performance and integrity, are obtained with sub-micrometer spatial resolution and nanometer measuring accuracy. To inspect an entire wafer with OEH techniques, measurements of overlapping regions of interest (ROI) on a wafer are recorded and adjacent ROIs are stitched together through efficient 3D correlation analysis algorithms.
Single Osteoblast Chemical Sensor via Non-invasive Bio-Electronic Interface
Authors: Yang Mo , Zhang Xuan , Kohr Bonnie , Morgan Andre , Ozkan Cengiz S
Published: April 2011

The broad-spectrum sensitivity of cell based biosensors offers the capability for detecting known and unknown chemical/biological agents. One cellular parameter that is often measured is the extracellular potential of electrically active cells. Membrane excitability in osteoblasts plays a key role in modulating the electrical activity in the presence of chemical agents. However, the complexity of this signal makes interpretation of the cellular response to a chemical agent difficult to interpret. By analyzing shifts in the signal's power spectrum, it is possible to determine a frequency spectrum also known as Signature Pattern Vectors (SPV) specific to a chemical. We used a 5x5 multiple microelectrode array system to spatially position osteoblast cells, by using a gradient AC field. Fast Fourier Transformation (FFT) analyses were used to extract information pertaining to the frequency of firing from the extracellular potential.
Kinetics and Mechanism of Nucleation, Growth and Stabilization of Metal Oxide Nanoparticles
Authors: Tannenbaum Rina , King Scott , Hyunh K. , Zubris Melissa , Dan Nily
Published: April 2011

Reactive metallic fragments that are formed by the decomposition of organometallic complexes, undergo a nucleation and growth process that gives rise to the formation of nanocrystals. In the absence of stabilizing molecules, the aggregation process is restricted mainly due to the decreasing mobility of the particles and their declining diffusional rates as a function of their increasing size. On the other hand, in the presence of a polymer in the reaction medium, the growing metallic particles are stabilized by the surface adsorption of the polymer chains, thus lowering their surface energy and creating a barrier to further aggregation. Studies of the nucleation and aggregation kinetics of metallic particles formed from the decomposition of organometallic precursors have been used to shed light on the mechanism of their formation. In these studies, the rate of decomposition of the precursor organometallic complexes used has been considered to represent the overall rate of the process. Moreover, it has been implicitly assumed that the formation kinetics of the metal nanoclusters directly coincides with the decomposition kinetics of their precursors. In this study, we attempt to decouple the kinetic characteristics of the various steps that comprise the overall nucleation and aggregation process cobalt oxide nanoclusters. A combination of infrared and x-ray photoelectron spectroscopies, and particle size determination by dynamic light scattering, are used to identify the individual contribution of each step to the overall mechanism of metal nanocluster formation.
Characterizing the Dopant Behavior of Functionalized Carbon Nanotubes in Conducting Polymers
Authors: Hughe Mark , Snook Graeme A. , Chen George Z. , Shaffer Milo S. P. , Fray Derek J. , Windle Alan H.
Published: April 2011

The electrochemical polymerization of conducting polymers, such as polypyrrole, generally requires the incorporation of an anionic dopant to balance the positive charge on the oxidized conducting polymer chains. The susceptibility of multiwalled carbon nanotube (MWNT) surfaces to functionalization makes them exciting candidates for a new class of dopant for conducting polymers. In this work, the doping of polypyrrole with functionalized MWNTs is investigated using a combination of electrochemical impedance spectroscopy, scanning electron microscopy, and quartz crystal microbalance work. The findings described here are particularly relevant in light of recent reports indicating that carbon nanotube-conducting polymer composites hold great promise for use in electrochemical capacitors, also known as supercapacitors [1,2].
Carbon Nanotubes and Nanofibers Grown by Microwave Plasma Enhanced Chemical Vapor Deposition on a Nickel Substrate
Authors: Belay K. G. , Jackson J , Xin Yan
Published: April 2011

Both carbon nanotubes and carbon nanofibers were grown on a thick nickel substrate by means of microwave plasma enhanced chemical vapor deposition (MPECVD) process using 20% CH4 and 80% H2 at a temperature of 750°C and a pressure of 50 Torr. The substrate was pre-abraded with 1.0μm diamond powder and 15.0 μm diamond paste to increase the rate of nucleation. When the substrate is taken out of the reactor the film detaches itself completely from the nickel. Unusual outgrowth structures appear jutted on one section of the substrate in a symmetrical manner. These structures were very hard and, when analyzed using environmental scanning electron microscope (ESEM), Raman microscopy and transmission electron microscope (TEM), micro-trees and an abundance of multi wall carbon nanotubes (MWCNTs) and nanofibers were observed. An attempt to measure the hardness of the film using a nano-indenter was inconclusive due to the extreme hardness of the material produced.
Proton Conducting Nano Hybrid Membranes Synthesized from Temperature Tolerant Polydimethylsiloxane (PDMS) Polymers
Authors: Kim Je-Deok , Honma Itaru
Published: April 2011

Flexible and temperature tolerant nano-hybrid membranes consisting of zirconium (titanium) oxides and polydimethysiloxane (PDMS) with the different molecular mass of 4500 and 600 have been synthesized by sol-gel processes. The membrane of zirconium/PDMS=2 (in molar) showed enhanced thermal stability and flexibility up to 300 °C due to the presence of cross-linkable inorganic nano-phase in the hybrid macromolecular matrix. The membrane becomes proton conducting polymer electrolyte when doped with 12-phosphotungstic acid (PWA). The proton conducting properties of the hybrid membranes with various PWA concentration were measured in the temperature range from room temperature to 150°C under saturated humidity conditions. A maximum conductivity of 2×10-2 S/cm was obtained at 150°C when the PDMS/zirconium oxides hybrid matrix was changed to gel state due to the higher water activity at elevated temperatures.
Improved Tribological Properties of Diamondlike Carbon/Metal Nanocomposites
Authors: Narayan Roger J. , Scholvin Dirk
Published: April 2011

One 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

We 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

Supercritical 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

In 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

A 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

The 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

Open-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

The 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

This 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

Chemical 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

Electrical 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

The 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

Gallium 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

Anomalous 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

The 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

We 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

Nanoscale 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

One-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

In 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.
Application of Diluted Magnetic Semiconductors and Quantum Dots to Spin Polarized Light Sources
Authors: Bhattacharya Pallab , Fathpour Sasan , Chakrabarti Subhananda , Holub Michael , Ghosh Siddhartha
Published: April 2011

The magnetic properties of single and multiple layers of GaMnAs, grown by molecular beam epitaxy, have been investigated for application as spin injector layers in spin polarized lights sources. Curie temperatures, TC, as high as 150K have been measured in 15nm Ga0.95Mn0.05As films and similar results are obtained for multiple thin layers of GaMnAs separated by 5nm thick GaAs layers. We have also investigated the properties of self-organized InMnAs quantum dots buried in a GaAs or GaMnAs matrix. Magnetization measurements indicate TC >300K in the dot heterostructures. Light-emitting diode heterostructures with 150nm Ga0.95Mn0.05As spin injector layers and In0.4Ga0.6As quantum dot active regions were grown and fabricated into 600μm diameter mesa-shaped surface-emitting devices. Polarized light at 1.05μm is observed with an output polarization efficiency of 26% at a record high temperature.
Fabrication of Flexible One-Dimensional Porous Silicon Photonic Band-Gap Structures
Authors: Tokranova Natalya , Xu Bai , Castracane James
Published: April 2011

Photonic crystals are periodic dielectric structures that have a photonic band gap to control the propagation of light in a certain wavelength range. This property offers a means to manipulate photons in the same way as electrons can be controlled in an atomic lattice. Porous silicon is an ideal candidate fo r the fabrication of photonic crystals because of the availability of a variety of silicon micromachining techniques. One-dimensional photonic crystals with customized parameters can be economically fabricated using porous silicon multilayer structures with periodically modulated porosity. Despite the structural non-homogeneities, porous silicon fabricated on a p-type Si substrate has optical properties similar to a dielectric material with a single effective refractive index. The exact value of the refractive index for each layer depends on its porosity. An engineered porosity can be obtained by changing the etching currents during the anodization process. This results in a modulation of the refractive index. A stack of alternating layers with high and low porosity produces a distributed Bragg reflector (DBR). Various designs incorporating multilayer porous silicon structures with an optical Fabry-Perot resonator and coupled microcavities are under development and can serve as an optical filter. Prototypes of such free-standing structures with 21–200 stacked layers to be used as DBRs, Fabry-Perot resonators or coupled microcavities are being fabricated. These structures are coated with polystyrenesulfonate on their backsides to increase mechanical strength and at the same time maintain flexibility. In this work, reflectance spectra of these porous silicon multilayers with and without polymer on the backside were measured. Simulations of the multilayer one-dimensional photonic crystals were performed to predic t the reflectance spectrum and optimize their structures before the fabrication and to compare to experimental data.
Strong light confinement in microporous photonic silicon structures
Authors: Lérondel G. , Reece P. , Bruyant A. , Gal M.
Published: April 2011

We have recently reported the fabrication of Si based subnanometer linewidth microcavities and omnidirectionnal mirrors. The structures were made of microporous silicon by electrochemical anodization. The structure high quality and the observation of omnidirectionnal stop bands have been made possible by the optimisation of the starting material, the etching conditions, and the structure design. In this paper we discuss more specifically the choice of these parameters considering the material intrinsic limitations.
Optical devices based on anisotropically nanostructured silicon
Authors: Diener J. , Künzner N. , Gross E. , Kovalev D. , Fujii M.
Published: April 2011

Anisotropic nanostructuring of bulk silicon (Si) leads to a significant optical anisotropy of single porous silicon (PSi) layers. A variation of the etching current in time allows a controlled modification of the porosity along the growth direction and therefore a three-dimensional variation of the refractive index (in plane an in depth). This technique can be important for photonic applications since it is the basis of a development of a variety of novel, polarization sensitive, silicon-based optical devices: retarders, dichroic Bragg Reflectors, dichroic microcavities and Si based polarizers.
Interaction of Periodically Arranged Point Defects in a Two Dimensional Photonic Crystal -The Photonic Analogue to a Doped Semiconductor
Authors: Richter S. , Schweizer S. L. , Hillebrand R. , Jamois C. , Wehrspohn R. B. , Zacharias M. , Goesele U.
Published: April 2011

We present and characterize hexagonal point defects in a two dimensional photonic crystal based on macroporous silicon. These point defects are prepatterned periodically, forming a superstructure within the photonic crystal after electrochemical etching. Spatially resolved, optical investigations related to morphological properties, like defect concentration and pore radius, are compared to bandstructure calculations. The confined defect states are identified and their interaction is evaluated quantitatively.
Innovation Providing New Multiple Functions in Phase-Change Materials To Achieve Cognitive Computing
Authors: Ovshinsky Stanford R. , Pashmakov Boil
Published: April 2011

This paper describes a basic new scientific and technological approach for information and computing use. It is based on Ovonic cognitive devices that utilize an atomically engineered Ovonic chalcogenide material as the active medium. We demonstrate how such a device possesses many unique functions including an intrinsic neurosynaptic functionality that permits the processing of information in a manner analogous to that of biological neurons and synapses. Our Ovonic cognitive devices can not only accomplish conventional binary computing, but are capable of non-binary generation of information, storage, encryption, higher mathematics, modular arithmetic and factoring. Uniquely, almost all of these functions can be accomplished in a single nanosized device. These devices and systems are robust at room temperature (and above). They are non-volatile and also can include other volatile devices such as the Ovonic Threshold Switch and Ovonic multi-terminal threshold and memory devices that can replace transistors.
Key Technology for Ultra Density Optical
Authors: Somekh Robert E. , Davies Clare E.
Published: April 2011

Ultra Density Optical (UDO) has been designed as the Phase Change successor to 5¼-inch Magneto Optic data storage products, with a UDO road map spanning three product generations leading to 120GB capacity. First generation UDO will utilise 405nm wavelength, 0.7NA drive optics with 100 micron cover layer media construction in a robust, double-sided cartridged format with 30GB capacity. There will be two types of UDO, both aimed at the professional market: UDO Write Once for high density, high data rate, archival data storage applications, and high cyclability UDO Rewritable. The features of UDO and the underlying Media Engineering optimisation strategies are discussed.
Mechanisms of Initialization of Doped Sb-Te Phase-Change Media
Authors: Towlson Samantha J. , Elwell Clifford A. , Davies Clare E. , Greer A. Lindsay
Published: April 2011

Laser initialization of the chalcogenide optical-recording medium Ag-In-Sb-Te is investigated using transmission electron microscopy of the resulting microstructure. Initialization beam power and velocity are varied. The average inhomogeneous strain of the chalcogenide is estimated from X-ray peak broadening. At high power and low velocity a clearly defined columnar grain structure with low strain is produced, typical of directional solidification. At low power and high velocity the initialized structure has a high density of defects and high strain; this is attributed to crystallization from the amorphous rather than the liquid state. The beam power and linear velocity of laser initialization may therefore be used to control the microstructure.
Nonlinear characteristics of super resolution chalcogenide thin film
Authors: Kim Se-Young , Kang Myung-jin , Choi Se-Young
Published: April 2011

A third order nonlinear optical material, As2Se3 was proposed for super resolution near field structure disk. As2Se3 was deposited by thermal evaporation technique. Composition, phase, surface morphology, linear/non-linear optical properties were obtained from EPMA, XRD, AFM, UV-VIS-NIR spectrophotometer and VASE. As2Se3 thin film showed large non-linear optical characteristics (XR(3) =7.42×10-7 m2/w, γ=1.268×10-5m2/w) and self-focusing phenomenon. Super resolution effects of the As2Se3 thin films were measured by using the laser beam profiler. As a result, recording density can be enhanced by 2.3 times, in case of 350nm As2Se3 thin film was deposited as super-RENS.
Synthesis, Characterization and Study of the Radiation Effects on Hollandite Ceramics Developed for Cesium Immobilization
Authors: Aubin Virginie , Caurant Daniel , Gourier Didier , Baffier Noël , Advocat Thierry , Bart Florence , Leturcq Gilles , Costantini Jean M.
Published: April 2011

Progress on separating the long-lived fission products has notably implied basic research on specific host matrices, especially for the immobilization of cesium. Barium hollandite (BaAl2Ti6O16) ceramics have received considerable interest because of their high cesium incorporation ability and chemical stability. This study deals with the preparation of hollandite in the BaxCsy(Al,Fe)2x+yTi8–2x-yO16 (x+y<2) compositional range by an oxide route. Different parameters such as the grain size of the precursor or the temperature and duration of sintering were changed in order to optimize ceramics synthesis. To estimate the hollandite radiation resistance, external electron irradiation experiments (simulating the β particles emitted by radioactive cesium) were performed on hollandite of simple composition. The irradiation-induced defects were studied by Electron Paramagnetic Resonance (EPR) spectroscopy and their nature is discussed.
Quantitative Assessment of the Instant Release Fraction (IRF) for Fission Gases and Volatile Elements as a Function of Burnup and Time under Geological Disposal Conditions
Authors: Ferry Cécile , Lovera Patrick , Poinssot Christophe , Johnson Lawrence
Published: April 2011

The Instant Release Fraction at container failure time, IRF(t), is here considered as being the sum of (i) the initial labile fraction, corresponding to the sum of gap and grain boundary inventories of certain radionuclides on exit from the reactor, with a further possible contribution from segregation in the rim region and (ii) the time-dependent fraction of radionuclides accumulating at grain boundaries due to a self-irradiation enhanced diffusion through the grains. The initial labile fraction of radionuclides such as 14C, 36Cl, 79Se, 129I, and 135Cs has been estimated based on leaching experiments, post-irradiation fission gas release measurements and studies of solid-state chemistry of spent fuel, along with estimates of fission product segregation in the rim zone. The contribution of the a self-irradiation enhanced diffusion has also been estimated based on a diffusion coefficient decreasing with time proportionally with the volume α-activity of the spent fuel. Its contribution to the IRF is limited for UO2 fuels. The proposed bounding values of the IRF for fuel with a burnup of 55 GWd/tIHM for 14C, 36Cl, 79Se, 129I, and 135Cs are 11 % at t=0 and close to 15 % at a container failure time of 10,000 y.