We present results of extremely short carrier lifetime measurements on a series of hydrogenated nanocrystalline silicon (nc-Si:H) thin films by a novel, non-destructive, non-contact method. Transmission modulated photoconductive decay (TMPCD) is a newly developed technique which appears to have high enough sensitivity and time resolution to measure the extremely short carrier lifetimes on the order of a nanosecond. As a proof of this, we measure various nc-Si:H samples of varying crystalline volume fraction as well as a fully amorphous sample. To ascribe an effective lifetime to the materials, we use a simple model which assumes a single exponential decay. By using this model, effective lifetimes can be deconvoluted from our pump beam giving nanosecond lifetimes. Lifetimes of between 1.9 and 0.9 nanoseconds are reported and trend to decreasing lifetimes as crystalline volume fraction is increased.

Aluminum alloy series 2xxx, 6xxx, 7xxxx and 8xxx enjoy the widest use in aircraft structural applications. Among these materials, aluminum alloy 2024 remains the most commonly used and especially in T351 temper situation. The fatigue crack propagation behaviour of aluminum alloy 2024 T351 has been investigated using V-notch specimen in four bending test. A series of stress ratios from 0.10 to 0.50 was investigated in order to observe the influence of stress ratio on the fatigue life and fatigue crack growth rate (FCGR). The increase in FCGR, which occurs as the stress ratio is increased from 0.10 to 0.50, is generally attributed to an extrinsic crack opening effect. In T-S orientation and at low stress intensity factor, the increasing of stress ratio increase the FCG. Experimental results are presented by Paris law when coefficients C and m are affected by stress ratio. Contrary, at high stress intensity factor, the effect of stress ratio is reversed. We notice a decreasing of fatigue crack growth rate with an increasing of stress ratio. This effect may be explained by microstructure effect in (T-S) crack growth. The analysis of stress ratio effect by Elber model, shown that this model gives bad interpolation in this situation and the parameter characterized the crack closure factor will be adjusted.

Quantum efficiency measurements in (nc-Si:H) solar cells deposited onto textured substrates indicate that these cells are close to the “stochastic light-trapping limit“ proposed by Yablonovitch in the 1980s. An interesting alternative to texturing is “plasmonic“ light-trapping based on non-textured cells and using an overlayer of metallic nanoparticles to produce light-trapping. While this type of light-trapping has not yet been demonstrated for nc-Si:H solar cells, significant photocurrent enhancements have been reported on silicon-on-insulator devices with similar optical properties to nc-Si:H. Here we report our work on the measurerements of quantum efficiencies in nc-Si:H solar cells and normalized photoconductance spectra in SOI photdetectors with and without silver nanoparticle layers. As was done previously, the silver nanoparticles were created by thermal annealing of evaporated silver thin films. We observed enhancement in the normalized photoconductance spectra of SOI photodetectors at longer wavelengths with the silver nanoparticles. For nc-Si:H solar cells, we have not yet observed significant improvement of the quantum efficiency with the addition of annealed silver films.

Phosphorus is an important n-type dopant for both silicon and silicon carbide. Although solid-state diffusion of phosphorus in silicon has been well documented and experimentally proven, not much is known about phosphorus solid-state diffusion in silicon carbide, especially at lower temperatures. A convenient source of phosphorus for solid-state diffusion in silicon carbide is phosphorus oxide. The possibility of using phosphorus oxide as a dopant source for silicon carbide is investigated by considering the probable reactions between silicon carbide and phosphorus oxide at temperatures below 1700 K using published thermodynamic data. By considering the standard free energies of reactions, it can be shown that phosphorus can be introduced in silicon carbide at temperatures below 1700 K using phosphorus oxide. A successful development of low temperature dopant incorporation in silicon carbide would reduce the need for high temperature processes and prevent process-induced thermal degradation of critical device structures such as the oxide-semiconductor interface. Experimental results showing phosphorus impurity incorporation and activation in 4H-SiC are presented.

Major adsorbent materials used in heavy metal ion removal from polluted aqueous streams are expensive and difficult to regenerate. In this study, the possibility of using pectin, as an alternative biosorbent material to remediate heavy metal pollution was investigated. The effects of different parameters such as pH, concentration and temperature of metal solution, and contact time on the biosorption process were studied. The maximum removal efficiency was obtained at pH 2.0 for lead and zinc and pH 4.0 for cadmium. For most of the metals tested, a contact time of 15 minutes was sufficient for achieving the maximum removal. There was no significant influence on the removal capacity of pectin by the concentration and temperature of the metal solution. Under these experimental conditions the biosorption was favorable (65% lead, 42% zinc and 55% cadmium). The ability to use pectin for the removal or recovery of metals from aqueous solutions is evident.

Fiber optic sensors offer a novel approach to monitoring of fractures in concrete waste disposal vaults and offer the possibility of determining the quantity, width and location of the cracks as they form. Fiber optics can directly detect cracks if they form within the path of a fiber optic as well as monitor secondary indicators of cracking such as temperature changes and strain. When cracks form in concrete waste disposal vaults they can fill with water which has a high heat capacity, this enables cracks to be observed by monitoring temperature variations near the crack. An analytical solution for heat transfer is applied to estimate the propagation of temperature waves around cracks. It is demonstrated that discharge rates through the concrete which are less than 10-5 m3/m-s do not produce a meaningful temperature wave through the concrete. Fractures in the concrete must be larger than 0.07 cm to produce a measurable result and temperature sensors must be located within 0.5 meters of a crack to detect a change in temperature produced by seasonal groundwater flow through a crack. A distributed system of fiber optic sensors may be embedded in the concrete vault and used to monitor crack formation, temperature variations and strain.

The systematic investigation on the thermal stability of the CoO layer was carried out for various electrode materials. When Pt with higher oxygen potential (Gibbs free energy change of the oxidation reaction) compared to Co is used as electrodes, the resistance of the Pt/CoO/Pt devise was severely decreased by the post deposition annealing (PDA) process and the resistance switching into the high resistance state was observed in the first voltage sweep. This indicants that the reducing Ar ambient induces the quite local reduction of CoO. The reduction of the CoO layer is also expected even with the Co electrode, which is reasonably attributed to the oxygen concentration gradient at the Co/CoO interface in the Co/CoO/Pt device. With the Ti electrode having a much lower oxygen potential than Co, the reduction of CoO by Ti is also indicated electrically in the Pt/CoO/Ti device. On the other hands, W electrodes which is thought to have the solid-solution oxygen can stabilize the CoO layer during PDA although W is more affinitive with oxygen compared with Co. It can be pointed out the oxygen delivery at the electrode/oxide layer interface is a critical factor in designing the thermally stable stacking structure for resistance random access memory.

This paper addresses the characterization of the ferroelectric Ba0.6Sr0.4TiO3 on different substrates using three different microwave components. First, at low frequencies, metal-insulator-metal (MIM) capacitors are used to investigate the variation of the BST dielectric constant and loss tangent for different biasing voltages. BST shows a variation for the dielectric constant from 380 to 130, recording a tunability range of 66 %, and loss tangent of 0.027 to 0.005. In the range of frequency from 1 to 40 GHz, coplanar waveguides (CPW) are used to investigate the effective dielectric constant of BST on four different substrates, HR silicon substrates covered by silicon dioxide, silicon covered by silicon dioxide and silicon nitride, magnesium oxide (MgO (100)), and R-plane sapphire (Al2O3) substrate, all covered with 350 nm BST layer. The effective dielectric constant over silicon substrates covered by silica and BST is 7.2, 6.3 for Al2O3 substrates and 5.8 for MgO; and for the loss tangent, Al2O3 and MgO give about 0.03, while silicon substrates suffer higher values of 0.08 to 0.25. Finally, to study the tunability of microwave structures on the investigated substrates, interdigital capacitors (IDC) are fabricated and measured for different biasing voltages ranging from 0 to 55 V. IDCs over MgO show a tunability of 8.3%, while IDCs over sapphire show 20%.

In this paper we present results on the use of multilayered a-SiC:H heterostructures as an integrated device for simultaneous wavelength-division demultiplexing and measurement of optical signals. These devices are useful in optical communications applications that use the wavelength division multiplexing technique to encode multiple signals into the same transmission medium.

The device is composed of two stacked p-i-n photodiodes, both optimized for the selective collection of photo generated carriers. Band gap engineering was used to adjust the photogeneration and recombination rates profiles of the intrinsic absorber regions of each photodiode to short and long wavelength absorption and carrier collection in the visible spectrum. The generated photocurrent signal using different input optical channels was analyzed at reverse and forward bias and under steady state illumination. A demux algorithm based on the voltage controlled sensitivity of the device was proposed and tested. An electrical model of the WDM device is presented and supported by the solution of the respective circuit equations. Other possible applications of the device in optical communication systems are also proposed.

A Ni/MgO-La2O3-Al2O3 catalyst with Ni as active component, Al2O3 as support, MgO and La2O3 as additives was prepared and its catalytic activity was evaluated in the process of hydrogen production from catalytic steam reforming of bio-oil. In the catalytic evaluation, some typical components present in bio-oil such as acetic acid, butanol, furfural, cyclopentanone and m-cresol were mixed following a certain proportion as model compounds. Reaction parameters like temperature, steam to carbon molar ratio and liquid hourly space velocity were studied with hydrogen yield as index. The optimal reaction conditions were obtained as follows: temperature 750-850 °C, steam to carbon molar ratio 5-9, liquid hourly space velocity 1.5-2.5 h-1. The maximum hydrogen yield was 88.14%. The carbon deposits were formed on the catalyst surface but its content decreased as reaction temperature increased in the bio-oil steam reforming process.

We describe the concept of a 3D self-folding package (SFP) for sensors and electronic devices. The strategy is based on a self-assembly strategy wherein 2D panels interconnected with hinges spontaneously fold-up when they are released from the substrate; self-folding can be triggered by temperature or selected chemicals. The strategy enables packaging of devices in porous polyhedral geometries that can either be untethered or substrate-bound. Self-folding can enable packaging of devices in small 3D form factors and may enable efficient cooling due to porosity. The utilization of this self-folding platform to enable 3D packaging of cantilever sensors and magnetic field sensitive strain gauges is summarized.

Electron tomography and high-resolution transmission electron microscopy were used to characterize the unique 3-dimensional (3D) structures of twinned Zn3P2 (tetragonal) and InAs (zinc blende) nanowires synthesized by the vapor transport method. The Zn3P2 nanowires adopt a unique superlattice structure that consists of twinned octahedral slice segments having alternating orientations along the axial [111] direction of a pseudocubic unit cell. The apices of the octahedral slice segment are indexed as six equivalent <112> directions at the [111] zone axis. At each 30 degrees turn, the straight and zigzagged morphologies appear repeatedly at the <112> and <011> zone axes, respectively. The 3D structure of the twinned Zn3P2 nanowires is virtually the same as that of the twinned InAs nanowires. In addition, we analyzed the 3D structure of zigzagged CdO (rock salt) nanowires and found that they include hexahedral segments, whose six apices are matched to the <011> directions, linked along the [111] axial direction. We also analyzed the unique 3D structure of rutile TiO2 (tetragonal) nanobelts; at each 90 degree turn, the straight morphology appears repeatedly, while the in-between twisted form appears at the [011] zone axis. We suggest that the TiO2 nanobelts consist of twinned octahedral slices whose six apices are indexed by the <011>/<001> directions with the axial [010] direction.

A systematic approach was taken to identify methods to prevent post CMP corrosion of copper in 22nm interconnect structures. Line to line current leakage measurements (at various times post CMP) were used as a means to quantify the extent and time-dependence of copper corrosion. Interruption of the corrosion mechanism by the use of passivating agents in post-CMP clean chemistries is explored. A broad-based screening was conducted to identify aqueous formulations of passivating agents for protection of copper which do not have deleterious effects on line resistance and overall defectivity. A formulation was identified which was effective in preventing corrosion when applied during post CMP brush clean.

The vanadium (V)-doped titania (Ti0.95V0.05O2) was impregnated in the host matrix of the pre-synthesized siliceous mesoporous material MCM-41 in a single pot synthesis step, by the wet impregnation route. The samples were characterized by x-ray diffraction, transmission electron microscopy (TEM), N2 adsorption, diffuse reflectance ultraviolet–visible spectroscopy (DRUVS). As compared to Ti0.95V0.05O2, the DRUV spectra of the impregnated catalysts showed a blue shift; still the absorption lies in the visible region. Presence of nano-sized (∼2–12 nm) V-doped titania particles in V-TiO2/MCM-41 was revealed by TEM and the particle size was found to increase with the loading of the V-doped titania in the host matrix. All impregnated samples were found to be more active than either the bulk V-doped titania or titania for photocatalytic oxidation of ethylene in air at ambient conditions under both UV and visible irradiation.

We report the effect of adding NiO nanoparticles on the transport properties of the half-Heusler alloys Zr0.5Hf0.5Ni1-x PdxSn0.99Sb0.01 (x=0, and 0.2). The half-Heusler matrix materials are prepared by traditional powder metallurgy methods. The resulting bulk matrix is mixed with different volume fractions of nanometer-sized NiO particles, previously synthesized by solution-phase chemical methods. The resulting mixture is densified under uniaxial pressure to form a composite. The resulting material is found to contain both half-Heusler and full-Heusler phases. The corresponding compounds have higher thermal conductivity and electron mobility.

Metal nanoinclusions inside the bulk thermoelectric matrix have the potential to increase the power factor and reduce the lattice thermal conductivity. We have synthesized Bi2-xTe3+x (x=0, 0.05)compositions, to achieve better tenability in Seebeck and electrical conductivity. In this matrix phase, different volume fractions of Bi metal nanoinclusions were incorporated and its effect on thermoelectric properties is discussed. Ag metal nanoinclusions were incorporated into Bi2Te3(2:3) composition, and its effect on power factor is discussed here.

In this study, we introduce ‘molecularly imprinted polymer' (MIP) system, which has receptor or binding sites with specific molecular recognitions.

Due to the receptor or binding sites in MIP's systems, it can be used for developing bio- or chemical sensors.

To fabricate bio-sensors, bio-molecules have been incorporated into MIP's systems as template molecules, but some bio-molecules are sensitive thus denatured during engineering processes.

For this reason, bio-sensor fabrications by conventional UV photolithography have shown some limitations.

We demonstrate here a photopatterning process, a micromolding in capillary technique (MIMIC) technique, to photopatterning a MIP's system containing a bio-molecule template.

The MIMIC technique uses the photo-masks for photopolymerizing MIP's monomer solutions.

The photomask is based on silicon rubbers, which are optically transparent and also minimize any damages of sensitive bio-molecules during photo-polymerizations. For visualizing lithographic performances of MIP's systems, we used a fluorescent template molecule to present a comparative result of MIP's photo-cured patterns.

It shows a clear different in MIP's patterns with and without the template.

We also employed a microfluidic approach to produce micro-sized MIP's particles, which contribute to increase the sensitivity of bio-molecule sensors/devices.

Space environmental effects on materials are very severe and complex because of the synergistic interaction of orbital environments such as high-energy radiation particles, atomic oxygen, micrometeoroids, orbital debris, and ultraviolet irradiation interacting synergistically, along with thermal exposure. In addition, surface degradation associated with contamination can negatively impact optics performance. Materials flight experiments are critical to understanding the engineering performance of materials exposed to specific space environments. Likewise, the spacecraft designer must have an understanding of the specific environment in which a spacecraft will operate, enabling appropriate selection of materials to maximize engineering performance, increase mission lifetimes, and reduce risk. This article will present a methodology for assessing the engineering performance of materials baselined for a specific spacecraft or mission. In addition, an overview of the space environment, from low Earth orbit to interplanetary space, will be provided along with an overview on the effects of the space environment on materials performance. The majority of this article is devoted to materials flight experiments from the European Space Agency (ESA), the Japan Aerospace Exploration Agency (JAXA), and from the National Aeronautics and Space Administration (NASA). Some of the experiments reviewed include ESA's Materials Exposure and Degradation Experiment on the International Space Station (ISS), JAXA's Micro-Particles Capturer and Space Environment Exposure Device experiments on the ISS Service Module and on the ISS Japanese Experiment Module Exposed Facility, and NASA's Long Duration Exposure Facility satellite and the Materials International Space Station Experiment series flown on the exterior of ISS.

Quantum Dots (QDs) bound to gold nanoparticles have shown photoluminescence (PL) quenching dependent on distance between the two particles. The incident light from the QD couples to plasmon excitation of the metal when the frequencies of the light and the surface plasmon resonance (SPR) coincide, leading to a reduction in emitted PL in the system. The quenching effect of gold nanoparticles on QDs was used to study protein-protein interactions with the potential for drug screening applications. CdTe and CdHgTe QDs with emission wavelengths from 500˜900nm were synthesized and gold nanospheres and nanorods with controlled absorption in the visible and near-infrared (NIR) wavelength regions were prepared. The PL quenching of QD-Protein-Protein-Au complexes was studied as a function of Au concentration, QD size and protein type. A quenching efficiency of up to 90% was observed. The QD-Au complexes were also studied for electric potential sensing. The surface of the QDs was negatively charged due to thiol ligands capping. By applying a positive potential on the gold or gold nanoparticle attached substrate, the local electric field between the substrate and the statically charged QDs would pull the QDs closer to the gold surface and quench the QD PL. PL quenching of QD with Au was studied as a function of electric signal and QD type. In this methodology, electric signals were effectively converted to optical signals.

In this paper a light-activated multiplexer/demultiplexer silicon-carbon device is analysed. An electrical model for the device operation is presented and used to compare output signals with experimental data. An algorithm that takes into accounts the voltage and the optical bias controlled sensitivities is developed. The device is a double pi'n/pin a-SiC:H heterostructure with two optical gate connections for light triggering in different spectral regions. Multiple monochromatic pulsed communication channels were transmitted together, each one with a specific bit sequence. The combined optical signal was analyzed by reading out, under different applied voltages and optical bias, the generated photocurrent across the device. Experimental and simulated results show that the output multiplexed signal has a strong nonlinear dependence on the light absorption profile, i.e. on the incident light wavelength, bit rate and intensity under unbalanced light generation of carriers. By switching between positive and negative voltages the input channels can be recovered or removed from the output signal.