A phenomenological model has been proposed for the radial growth of the copper or silver nanobridge in the conductive bridge random access memory devices. In this model, the growth rate of the bridge is proportional to the local ion flux based on the hopping mechanism. Due to the differences of the local electric field, the growth rate is different along a conical shape nanobridge. The model accounts for the growth rate difference by introducing a geometrical form factor. Based on the model, the top and bottom radii are predicted for truncated conical copper nanobridge. The model is validated with data obtained on Cu/TaOx/Pt resistive devices.

Yttrium titanate belongs to a family of compounds called pyrochlores with significant properties such as ionic conduction, optical non-linearity and radiation tolerance that have resulted in applications thermal barrier coatings, high-permittivity dielectrics, and materials for safe disposal of actinide-containing nuclear waste, and hydrogen storage material. The application of these materials in ODS ferritic steels, photocatalytic water splitting and a more efficient host material than TiO2 for Er3+ luminescence have been evaluated. ErxY2-xTi2O7 has tremendous applications in fiber amplifiers, integrated optical devices and selective emitters for thermophotovoltaic applications. Since 1-D nanostructures are deemed to be important building blocks for future optical and optoelectronic nanodevices, we have used electrospinning methods to synthesize nanofibers and freestanding, non-woven nanofibers membranes of single phase yttrium titanate and ErxY2-xTi2O7 (Er/(Ti+Er) at. ratio= 0 -15 %) with diameters less than 150 nm and have characterized the physical, thermal and optical properties of these nanofibers.

The amyloidosis of amyloid β (1-42) was investigated by the well-defined glyco-cluster interface. We prepared monovalent, divalent, and trivalent 6-sulfo-N-acetyl-D-glucosamine immobilized substrates. The interaction between amyloid β and 6-sulfo-N-acetyl-D-glucosamine was amplified by multivalency of divalent and trivalent 6-sulfo-N-acetyl-D-glucosamine. The morphology of amyloid β were investigated by AFM, and we found the morphology of amyloid β aggregates were determined by the kinds of displayed saccharide-valency. Amyloid β had tendency to form spherical objects on the multivalent 6-sulfo-N-acetyl-D-glucosamine, but form fibrils on the monovalent 6-sulfo-N-acetyl-D-glucosamine. Spherical amyloid β was more toxic than fibrillar amyloid β to HeLa cells. These results suggested that the multivalency of was significant in its morphology and aggregation effects at the surface of the cell membrane mimic.

We present electrogenerated chemiluminescence (ECL) and fluorescence lifetime mapping of MEH-PPV/PCBM thin films. The ECL results show that the oxidation peak of MEH-PPV near 0.7 V (vs. SCE) and ECL response of films shifted positively towards 1.2 V in the presence of PCBM. At the same time, the oxidation current density of MEH-PPV increases along with the decrease of ECL intensity in the presence of PCBM. The fluorescence lifetime images clearly show that the lifetime spatial heterogeneities are affected by different substrates and MEH-PPV/PCBM ratios. Meanwhile, the lifetime of MEH-PPV decreases with the increasing of film thickness. The lifetimes of MEH-PPV films on TiO2 substrate are lower than films on glass.

Oblique angle deposition (OAD) is a self-organizing physical vapor deposition (PVD) technique that has been used to grow sculpted 3D nanostructures including helices, slanted rods, and zigzag structures, and other shapes. OAD structures can be fabricated from virtually any material that can be deposited using PVD including: polymers, metals, semiconductors, oxides, and nitrides. The control over the nano-scale structural anisotropy of these materials allows one to tailor their electrical, magnetic, mechanical, crystalline, and optical properties. Through the careful design of the OAD structure and material selection this technique can be used to create photonic materials (1D, 2D, and 3D) with unique properties. We will discuss ongoing work using OAD to develop oxide thin film interference filters that can withstand extreme temperatures (800-1000° C) at mTorr vacuum levels, which are being developed for thermal photovoltaic applications.

The electrical heating of Ni/Al laminate foils allows interrogation of phenomena at heating rates as high as 10^12 K/s. In the 2011 Fall MRS meeting, we reported on emission spectra from rapidly heated Ni/Al laminates resolved temporally over 350 ns, which provided qualitative evidence of rapid and exothermic vapor phase mixing of Ni and Al in these experiments which we term electrical explosions. These results were significant, because thermal diffusion processes normally limit Ni/Al reactions to much slower energy release rates, potentially limiting their applications. Here we present further evidence of exothermic Ni/Al mixing, quantified by experimental velocity measurements of encapsulation material and interpreted by numerical calculations of energy partitioning into different processes. These calculations agreed well with experiments from different Al, Cu, and Ni samples, sputter-deposited and lithographically patterned into bow-tie bridge structures. Velocity measurements of up to 5 km/s for 11.5 μm thick parylene encapsulation layers were accurately predicted using a single, empirical fitting parameter which depended on the electrical circuit used. The calculations also agreed with encapsulation layers accelerated by electrically exploded Ni/Al laminates as long as an additional 1.2 kJ/g of energy was included in the model. This value is precisely the enthalpy of mixing between Ni and Al, and therefore quantifies the transduction of energy into encapsulation layer kinetic energy.

Refractory metal alloy WTi films were elaborated by magnetron sputtering from an alloyed target (W:Ti ∼ 70:30 at%). Film continuity threshold has been determined at 4.5 ± 0.2 nm using in situ surface differential reflectance (SDR) technique. Prior to film continuity, deposition of a continuous interfacial layer is suggested by both in situ and real-time SDR and wafer-curvature techniques. After continuity, Wx Ti1-x films (9.5 nm thick WTi films) have a body-centered structure with a {110} fiber texture. Composition (x) and microstructure can be tuned varying working pressure. A transition from compressive to tensile residual stresses was observed by ex situ XRD and wafer-curvature methods. Size dependent resistivity is obtained and slightly varies as a function of working pressure.

Nanoporous metal-organic framework (MOF) materials are strong candidates for energy efficient carbon capture and storage (CCS) technologies. A total of ∼20,000 hypothetical MOFs were ab initio screened for CO2 adsorption using grand canonical Monte-Carlo (GCMC) simulations. Novel radial distribution function (RDF) scores were modified for periodic systems to predict the CO2 adsorption of MOFs using chemoinformatic models. The test set predictions yielded accuracies of 0.76 and 0.85 at 0.1 bar and 1 bar, respectively. The models were used to screen a large database for high performing MOFs and the top 100 structures were successfully validated by GCMC simulations. The chemoinformatic predictors of the CO2 adsorption of MOFs are available online at http://titan.chem.uottawa.ca/woolab/MOFIA/#carbondioxide.

Aluminum (Al) gate fill has been implemented in Replacement Metal Gate (RMG) due to its low resistivity. Titanium (Ti) has been widely used as wetting layer for Al to fill the gates. For low resistance gate fill in structures with small feature size and high aspect ratio, Ti-Al metal fill becomes increasingly more challenging as we move from 20nm into 14nm FinFET and 3D type structures.

Cobalt (Co) is a good wetting film for Al with better fill performance and lower resistance than Ti-Al based process. However, due to the difference in corrosion potential between Al and Co, Chemical Mechanical Planarization (CMP) creates pitting type defects on Al-Co film that increases resistance variability across pattern density. CMP induced corrosion is separated in two parts; first is the static Co corrosion happened in the acidic chemical environment in the Al slurry. Second is the galvanic corrosion from Co-Al metal boundary due to high metal electrical potential. Static corrosion can be resolved by adding a Co corrosion inhibitor in the slurry formulation1. Galvanic corrosion can be minimized by controlling Co thickness deposition and formation of complete intermetallic phase. By controlling the removal rate with respect to corrosion rate we were able to suppress corrosion significantly.

We looked into compositions where the corrosion potential (Ecorr) gap between Al and Co is reduced to ≤10mV leading to reduced galvanic currents. Stabilization of the corrosion currents in both Al and Co was observed using potentiodynamic scans. The effect of pH, several oxidizers and additives on the open circuit potentials (Eoc) of Al and Co was investigated and it was found that solutions of KMnO4, saccharides and sulfonate group containing compounds help reduce the Ecorr gap in between Al and Co to ∼10 mV.

Controlling the Al gate height across pattern densities and gate lengths to within few nm is another challenge for Al CMP. The industry widely used approach is to clear all Al using a slurry with high selectivity to dielectric, followed by a CMP step using a non-selective Al-to-oxide slurry. Both polishing steps need to be optimized in parallel in order to remove the incoming spacer SiN divot, minimize Al loss on gates with high pattern density or long gate length, minimize oxide loss on large open areas while maintaining low defectivity.

In this paper we are presenting an innovate Al CMP process that demonstrated low gate resistance with tight distribution up to 80% pattern density. This work has been supported by the independent Bulk CMOS and SOI technology development projects at the IBM Microelectronics Division Semiconductor Research & Development Center, Hopewell Junction, NY 12533.

Measurements with the CELLO (solar cell local characterization) technique in the LBIC (laser beam induced current) mode under dark conditions with various constant bias voltages are used to analyze the lateral distribution, and mean values, of photocurrent response maps. Local solar cell defects such as local shunts were found to have a characteristic bias voltage dependence: At negative and small positive voltages a local shunt resistance gives less current response than the adjacent area. Upon applying higher positive voltages, a transition of the mean value to lower current response and an inversion of the local defect characteristics are found. These results were modeled by a newly introduced three dimensional (3D) equivalent circuit model of a solar cell divided into subcells.

Measurements and simulations of solar cells with various local defects show our method to be a new powerful tool for the quantitative analysis of local solar cell defects.

Hemin immobilized reduced graphene(HGN) has been investigated to be an outstanding enzymatic catalysis in detection important molecular recently. In this work, two "clean" methods to prepare HGN through π-π stack were charactered by UV-vis spectra, TEM images, and δ-potential. The enzymatic catalysis of both materials was compared by catalytic hydrogen peroxide to oxidize pyrogallol. The colorimetric result shows HGN attached before reduction has stronger catalytic ability than the one after reduction. The optimized HGN was then used as an electrochemical biosensor to determine L-tyrosine levels. The cyclic voltammetry (CV) tests were carried out for the bare glass carbon electrode (GCE), and the optimized hemin-reduced graphene electrode (HGN1/GCE). The HGN1/GCE based biosensor exhibits a Tyrosine detection linear range from 5×10-7 M to 4×10-5 M with a detection limitation of 7.5×10-8 M at signal noise ratio (S/N) of 3. In comparison with other biosensor, electrochemical biosensors are easy-fabricated, easy-controlled, and cost-effective. Compared with other materials, the hemin-reduced graphene based biosensors demonstrate higher stability, a broader detection linear range, and better detection sensitivity. The study of oxidation scheme reveals that reduced graphene enhanced the electron transfer between electrode and hemin. Meanwhile, the hemin groups effectively electrocatalyzed the oxidation of tyrosine. This study contributes to a widespread clinical application of nanomaterial based biosensor devices with a broader detection linear range, improved stability, enhanced sensitivity, and reduced costs.

A sectional method for determining particle size distributions has been implemented within the particle tracking module included with CHEMKIN-PRO. The module is available for use with many types of reactor models, ranging from 0-D batch reactors to laminar flame simulations. Coupled with the Burner-stabilized Stagnation Flame (BSSF) Model, the sectional model offers a high-fidelity, robust, and efficient computational framework for simulating flame synthesis of particles in a laminar, premixed stagnation flame environment. The CHEMKIN-PRO coupling allows inclusion of detailed gas-phase chemistry that determines key particle-formation precursors, along with physical processes such as nucleation and coagulation of particles. These capabilities are demonstrated for two flame-particle systems of practical importance, viz. nanocrystalline titania synthesis and soot formation. The results are compared with experimental data obtained at the University of Southern California (USC) flame facility. Computed particle size distributions show good agreement with experimental data. Simulations have led to exploration of the parameter space for particle production and particle-size influences.

Hydrogels are considered smart materials because they respond to environmental stimuli. Sensors that monitor the body’s pH levels would be helpful for doctors to determine the severity of a patient’s condition, especially if they exhibit signs of shock. The motivation of this project is to create a biomedical device that can be worn sublingually or implanted into the body to help doctors with diagnosing a patient’s condition. The magnitude of the swelling/deswelling behavior can be measured by placing a sample of the hydrogel in a piezoresistive sensor. The degree of swelling/deswelling is directly proportional to the change in pH of the aqueous solution it is placed in. In this study, a variety of compositions of pH responsive hydrogels were designed and tested to determine the response time and magnitude for use in both macro and micro sensor arrays. This pressure sensor has been designed for use with thinner gels than have been used in the past. The results for swelling time and magnitude were compared to determine the effect of the thickness of the hydrogel samples on the swelling/deswelling kinetics of the material in order to find the appropriate composition, thickness and device that will yield the desired response rate and sensitivity.

It has been an increase on the number of concrete structures with corrosion induced damage in Mexico in recent years. It is also well known that cathodic protection (CP) is the only method that stops corrosion in an efficient way. Since the 1990’s Florida and other USA states have been installing in concrete pile substructures, in bridges and piers, a three part hybrid galvanic CP system. This hybrid galvanic CP system includes a thermal sprayed part (located at the aerial zone of the pile), a zinc mesh encapsulated in mortar and inside a glass fiber jacket (located at the change in ties zone), and a submerged zinc bulk anode (in the submerged zone). From a previous investigation performed by the present authors, it has been found that the mortar inside the fiberglass form may decrease the mesh anode activation and thus decrease the CP system efficiency. Therefore, this investigation includes an evaluation of different additions placed in mortar to increase its electrical and ionic conductivity to increase the efficiency of the entire hybrid system. Additions include carbon, zinc and alumina powders, and this investigation presents preliminary experimental results obtained from the tested mortars (i.e. mortar physical characterization: electrical resistivity, ultrasonic pulse velocity, and total void content).

Opal particles, with diameter ca. 80 nm, were synthesized by the Stöber method. Samples were exposed to 100 Gy of beta particle irradiation and its thermoluminescence (TL) emission was recorded. TL response presents good reproducibility, standard deviation 1 %. The glow curve displays two TL peaks 86 and 400 °C and the afterglow (AG) phenomenon is observed immediately after irradiation (< 150°C). The synthetic opal-C exhibits a linear dependence of AG response as function of dose from 0.25 to 8 Gy. This dose range is of interest for personal and clinical dosimetry. Moreover, a previous study indicates that cytotoxic and genotoxic effects caused by opal nanoparticles, did not induce unrepairable DNA damage neither a cellular harm. Therefore, our results show synthetic opal-C is a material useful for in vivo radiation dosimetry.

With extremely disordered atomic structures, a glass possesses a thermal conductivity k that approaches the theoretical minimum of its composition, known as the Einstein’s limit.1 Depending on the material composition and the extent of disorder, the thermal conductivity of some glasses can be down to 0.1-0.3 W/m∙K at room temperature,2,3 representing some of the lowest k values among existing solids. Such a low k can be further reduced by the interfacial phonon scattering within a nanocomposite that can be used for thermal insulation applications. In this work, nanocomposites hot pressed from the mixture of glass nanopowder (GeSe4 or Ge20Te70Se10) and commercial SiO2 nanoparticles, or pure glass nanopowder, are investigated for the potential k reduction. It is found that adding SiO2 nanoparticles will instead increase k if the measured k values for usually porous nanocomposites are converted into those for the corresponding solid (k Solid) with Eucken’s formula. In contrast, pure glass nano-samples always show k Solid data significantly reduced from that for the starting glass. For a pure GeSe4 nano-sample, k Solid would beat the Einstein’s limit for its composition.

The boron-doped single crystal diamond films were grown homoepitaxially on synthetic (100) oriented Type Ib diamond substrates using a Microwave Plasma Chemical Vapor Deposition (MPCVD) technique. Raman spectrum showed a few additional bands at the lower wavenumber regions along with the zone center optical phonon mode for diamond. The change in the peak profile of the zone center optical phonon mode and its downshift were observed with the increasing boron content in the film. A modification in surface morphology of the film with increasing boron content had been observed by atomic force microscopy. Four point probe electrical measurement indicated that different conduction mechanisms are operating in various temperature regions for these semiconducting films.

The objective of this work is to examine the feasibility of electrically conductive hydrogel composites as scaffolds in tissue engineering and tissue regeneration, and to understand the properties of the composites as a growth matrix for clinically relevant cell lines. The composite is comprised of carbon nanobrushes embedded in a biocompatible poloxamer gel. This work assesses the ability of such composite gels to support the growth of fibroblasts and myocytes and eventually serve as a matrix to stimulate wound closure. In such a model, fibroblasts and myocytes are seeded on the hydrogel and bathed in culture medium. The experimental model assesses the ability of fibroblasts and myocytes to grow into and adhere to the gel. The work demonstrates that carbon nanobrushes can be dispersed within poloxamer gels, and that fibroblasts and myocytes can proliferate within homogenously dispersed carbon nanobrush-containing poloxamer gels. This work also examines the effects of carbon nanobrush content on the rheological properties of the poloxamer gel matrix and shows an improvement in several areas in the presence of carbon nanobrushes. Future work will examine the effects of design parameters such as carbon nanobrush content and matrix structure on wound healing, as well as the growth of tendons and other cell lines within the hydrogel composites. This work has relevance for tissue and cellular engineering and tissue regeneration in clinical medicine.