This research project aims at the development of new biopolymer nanocomposites which enable to act as a critical component to next generation medical device. In this paper, we developed an in situ method to encapsulate model protein, bovine serum albumin (BSA), within gelatin nanoparticles (NPs). The results demonstrate that the average diameter of the BSA-containing gelatin NPs is approximately 180 nm±10 nm. They can absorb up to 70% of water. The gelatin- nanoencapuslated BSA afterwards were loaded in the biopolymer film with thickness around 150 μm composed of poly(2-hydroxyethyl methacrylate) (pHEMA) through the photopolymerization. The release kinetics of BSA from the nanoparticles and the nanoparticle-laden p(HEMA) were studied through UV-Vis spectrometry, respectively. The releasing concentration of BSA increased with time (t), and about 80% of the encapsulated BSA was released in 80 hrs; while, the releasing profile of BSA from the gelatin nanoparticles-loaded hydrogel can be monitored up to10 days. These studies show that the gelatin nanoparticles are able to encapsulate water-soluble protein. The hydrogel film, pHEMA, enable to further prolong the releasing profile for the water soluble protein. It is expected that this new biodegradable polymer nanocomposites can be an alternative materials for consisting of implant medical device for protein therapy.

The road to achieve ultra high efficiency is through multi-junction solar cells operating at high solar concentrations, larger than 1000 suns. Critical to the success of this approach is the development of tunnel junctions (TJ) that serve as electrically low loss interconnections, yet are optically transparent, using high band gap semiconductor material systems. We have previously reported the fabrication of a TJ made of n+-InGaP/ p+-AlGaAs with a band gap about 1.9 eV using Se and C doping, respectively. This TJ structure has a peak current density of 88 A/cm2 allowing it to be implemented in a three junction cell structure at solar concentrations as high as 4000 suns (x4000). Almost all reported conversion efficiencies higher than 40% have used this tunnel junction. This very high peak current density is unexpected in a high band gap material system, which is good news for the multi junction solar community. This seems to be due to the fact that the InGaP/AlGaAs interface has a staggered band line up. We will present the effect of this band line up at the heterointerface and its effect on the width of the depletion region and the peak current density. We also compare the current result from this heterostructure junction with an artificial homojunction made of n+-AlGaAs/ p+-AlGaAs doped to the same levels as that of the heterojunction. Results from the homojunction showed that peak current density is about one half of that obtained from the heterojunction at the same doping levels. A reasonable match between experimental result and the model was obtained when a value of 150 meV was used for ΔEc, the conduction band discontinuity at the interface. Both experiment and theory predicted that at a current density of about 80 A/cm2 with only about a few tens of meV drop across the TJ. This will have a minimal effect on the overall efficiency of the tandem solar cell structure when used at high solar concentrations.

An exhaustive study on the resulting impurity profile in Si samples implanted with Ti with high doses and subsequently Pulsed-Laser Melting (PLM) annealed is presented. Two different effects are shown to be present in the two different stages of the annealing. In the melting stage the box-shaped effect tends to increase the thickness of the implanted layer and to decrease the maximum peak concentration as the energy density of the annealing increases. On the contrary, in the solidifying stage, the snow-plow effect decreases the thickness of the layer and increases the maximum peak concentration as the energy density of the annealing increases. Moreover, as a direct consequence of the snow-plow effect, part of the impurities is expelled from the sample by the surface.

A solder ball is the key material of the bump fabrication in the BGA and μBGA high integrated packaging. The nodulizer type is the main factor to affect the quality of the solder ball. In the paper the solder balls are fabricated by the fine wire cutting–remelting method. The influence of different nodulizers on the real sphericity and the surface appearance of the solder balls are investigated. Results show that, the real sphericity of the 63Sn37Pb solder balls is maximum and the surface quality of the solder balls is the best compared with the engine oil, heavy oil and silicon oil when the arachis oil is used as the nodulizer.

Carbon nanotubes (CNT) have seen a wide variety of applications, spread well beyond the semiconductor industries - especially in field emission related devices. For its widest possible application, it has become very much important to grow CNTs on a variety of metallic substrates and understand their field emission response. In the present study, multiwall CNTs (MWCNT), grown on pure metallic substrates like Cu, Al and W, were subjected to field emission tests under DC and AC bias. Choice of diffusion barrier layer and catalyst was also varied, to verify their effects on the emission response. Field emission behaviors from all such structures were compared with MWCNTs grown on Si. It was found that the MWCNTs grown on pure Cu substrate showed excellent field electron emission response, in terms of low turn-on field, high emission current, long time stability and very high field enhancement factor.

The fabrication of surface nano-roughened zinc oxide (ZnO) is demonstrated by using a zinc/air fuel cell based chemical reactor. The chemical reaction creates the hydroxyl near the Zn and randomizes the pores with accumulated hydroxyls, which causes Zn to be oxidized to form thick and nano-roughened ZnO upon Zn anode or to be transformed into a soluble complex zincate ion in the excess electrolyte. Furthermore, controlling the quantity of (Zn(OH)2) and [Zn(OH)4]2− can significantly decrease the defect-related emission and blue-shift PL spectra to the UV range.

The aim of this paper is to find a parameter space for deposition of amorphous silicon films at low substrate temperature by VHF PECVD process for application in solar cell fabrication on cheap plastics. Our studies show that at lower substrate temperature, keeping the pressure constant, the ion energy flux reaching the growth surface decreases, which we partly attribute to increasing gas phase collisions arising from an increase in gas density. The role of hydrogen is two fold: (1) higher hydrogen dilution increases the ion energy and restores it to its required value at low temperatures; (2) a normal to dusty plasma transition occurs at lower hydrogen to silane flow ratio and this transition regime shifts to higher dilution ratios for lower substrate temperatures. Thus the role of high hydrogen dilution at low temperature is to avoid the dusty regime. Thus the role of high hydrogen dilution at low temperature is to avoid the dusty regime. The ion energy flux at low substrate temperature can also be restored to the value obtained at high substrate temperature, without increasing hydrogen dilution, by simply lowering the chamber pressure or increasing the delivered plasma power, though the IEDFs in these cases differ substantially from the IEDF at high temperature conditions. We propose that a low pressure or high power in combination with a modest hydrogen dilution (high enough to avoid dusty regime) will deliver silicon films at low temperature without sacrificing deposition rate.

Since its introduction in 2001 [1], the concept of topological interlocking has advanced to reasonable maturity, and various research groups have now adopted it as a promising avenue for developing novel structures and materials with unusual mechanical properties. In this paper, we review the known geometries of building blocks and their arrangements that permit topological interlocking. Their properties relating to stiffness, fracture resistance and damping are discussed on the basis of experimental evidence and modeling results. An outlook to prospective engineering applications is also given.

We demonstrate the growth of lateral concentric BR on ZnO nano-pillars. It opens the opportunity to be used for (i) the enhancement of the lateral confinement in classical pillar-resonators in order to increase the emission rates in the regime of weak exciton-photon coupling (Purcell-effect), (ii) to enhance the exciton-polariton coupling strength in the strong-coupling regime, and (iii) to be used for two-dimensional confinement in free-standing photonic wire resonators. Spatially resolved PL experiments in dependence on the pillar diameter and on the temperature provide strong hints for the ZnO nano-pillar resonator being in the strong-coupling regime. The coupling strength can be estimated to be V = 80 meV.

Blending of red and blue photoluminescent silicon nanocrystals (Si-ncs) with poly(3-hexylthiophene (P3HT) conjugated polymer is demonstrated. The room temperature luminescent and ambient conditions stable Si-ncs prepared by electrochemical etching and laser ablation in water are used for the blend fabrication. Furthermore photo-electric properties in parallel configuration on platinum interdugitated contact are shown. Both types of Si-ncs results the bulk-heterojunction formation and photoconductivity is observed when the blends are irradiated AM1.5. The increase in photoconductivity is rather the same and ratio between photo- and dark-conductivity is about 1.7. The nanocrystal oxidation during laser ablation fabrication process in water hinders the transport properties of the blend.

Low level nuclear waste (LLW) will be stored in a series of modular vaults at the UK's principal LLW repository located near the village of Drigg in west Cumbria. The design of the new vaults is reviewed in the context of likely volume, composition and packaging of future waste streams; planning and regulatory considerations; and the site's geological and hydrogeological setting. Site construction work for the first of the new vaults (Vault 9) commenced in September 2008 and is anticipated to be substantially complete by the end of 2009 with future vaults constructed as required. The vaults are designed as a series of containment cells comprising a composite basal and sidewall lining system with an engineered capping system. Provision has been made for an extensive, deep cut-off wall as part of the longterm containment system for the whole repository site, which includes areas where LLW was historically tumble tipped into a series of trenches. Constraints on the design of the vaults include a complex hydrogeological setting controlled by two groundwater bodies influencing maximum excavation depth; geometrical limitations on the height, level and plan extents to which LLW could be stacked within the vaults; and strict limitations on the movement of construction materials by road.

We report the increase in open-circuit voltage (Voc ) by inserting of MoO3 layer on ITO substrate to improve built-in potential of organic solar cells (OSCs). In the OSCs using 5,10,15,20-tetraphenylporphyrine (H2TPP) as a p-type material and C60 as a n-type material, the Voc effectively increased from 0.57 to 0.97 V as increasing MoO3 thickness. The obtained highest Voc (0.97 V) is consistent with the theoretical value estimated from the energy difference between the LUMO (−4.50 eV) of C60 and the HOMO (−5.50 eV) of H2TPP layer. Importantly, the enhancement in the Voc was achieved without affecting the short-circuit current density (Jsc ) and the fill-factor (FF). Thus, the power conversion efficiency of the device linearly increased from 1.24% to 1.88%. We also demonstrated that a MoO3 buffer layer enhances the stability of OSCs after photo-irradiation. We have investigated the stability of OSCs using H2TPP and N,N′-di(1-naphthyl)-N,N′-diphenylbenzidine as a p-type layer. The both devices with MoO3 layer showed improved stability. These results clearly suggest that the interface at ITO/p-type layer affects the device stability.

Microwave assisted syntheses of stable solvent based colloidal sols of tailored ceria nanoparticlesOlivier Poncelet*, Julien Jouhannaud*, Denis Chaumont***CEA Liten DTNM/L2T , 17 rue des Martyrs F-38054 Grenoble Cedex9, France**Institut Carnot Bourgogne (ICB), UMR5209 CNRS, Facult� des Sciences Mirande, Universit� de Bourgogne, 9 Av. Alain Savary, BP 47870, F-21078 Dijon CedexThe pressure of environmental laws in many advanced countries becoming more restricting year after year, it is asked to automobile companies to strongly control the carburant consumption of cars that they put on the market and also to eliminate toxic chemicals coming from exhaust emission gases. This is particularly true for diesel oil which is particularly efficient in terms of carburant consumption but known to release toxic chemicals in exhaust gases. Among the materials able to solve these concerns, ceria (CeO2) is a choice catalyst because it can work in two different ways first as an oxygen store by release of oxygen in the presence of reductives gases (CnHn and CO), and also by removing oxygen by interaction with oxidising species (NOx), leaving finally in exhaust gases H2O, CO2 and N2.To be efficient ceria has to be used under nanoparticle form directly added in the diesel oil. The surface developed by the nanoparticles due to their small size positively influence the catalytic properties (both oxidation and reduction step) in terms of kinetic, so the ignition delay time for nanosized particles in the combustion chamber of diesel motors fits well with the high performance diesel motor characteristics. The true challenge is to be able to prepare stable solvent based sols of crystalline ceria nanoparticles which could be used without plugging the injection nozzles. We present various synthetic ways to produce ceria nanoparticles in water followed by their surface modification allowing stable colloidal sols in organic medium to be designed. We emphasize more particularly the microwave assisted synthesis which by enhancing nucleation of the nanosized particles versus growth of nanoparticles allows very narrow sized distribution of nanoparticles to be obtained. Moreover in terms of synthetic processes, microwave assisted syntheses allow to strongly reduced the synthetic time without compromise in terms of cristallinity (TEM and XRD). Surface modifications of the nanoparticles have been monitored by FT-IR, FT-Raman, while their sizes have been monitored by DLS (differential light scattering) from water to solvents suspension proving the efficiency of ether carboxylic acids as surface modifiers. Finally we will show preliminary results on the microwave assisted syntheses of mixed oxides materials (CeZrOx) and the way to design organic based sols of nanoparticles.

Many publications have examined the biodegradable polymer poly(propylene fumerate) (PPF) for use in tissue engineering applications. We have examined a similar crosslinkable polymer system, poly(propylene fumerate)-co-(propylene maleate) (PPFcPM), derived from maleic anhydride (MA) and 1,2-propanediol (PD). Two methods were examined in order to synthesis the copolymer. In the first case, the reaction was carried out at high temperature (250°C) under nitrogen using tosic acid as the catalyst. Only PPF was identified due to the thermal isomerization of the maleate groups to the more stable fumerate group. In the second case, toluene was used as the solvent to azeotropically (85 °C) remove water and drive the acid catalyzed esterification reaction. In the lower temperature case, a small amount of fumerate (<30%) was identified. Both polymer systems had glass transition temperatures (Tg) below room temperature. The PPFcPM copolymer was electrospun and crosslinked in situ to form porous micro- and nano fiber mats. Initial biocompatibility studies have also been preformed.

We demonstrated electrical characteristics of operational amplifier (OPAMP) circuits fabricated by GaN/AlGaN/GaN HEMTs operating over 100 oC. GaN/AlGaN/GaN HEMTs, with the extremely low source resistance were fabricated by multiple ion implantation, precisely controlled ion-implanted (I/I) resistors and Schottky barrier diodes were integrated on the silicon substrate. The GaN cap layer on the AlGaN was grown to decrease the gate leakage current and current collapse for AlGaN/GaN HEMTs.

The conjugated polymeric backbone of polydiacetylenes (PDAs), comprising of alternating ene-yne groups, undergo intriguing stress-, chemical- or temperature-induced chromatic phase transitions associated with the disruption of the backbone structure and shortening of the conjugation length. PDAs, such as polymerized 10, 12 pentacosadiynoic acids (PCDA), when incorporated with inorganic oxides form nanocomposites and uniform blends with polymers. Blends of poly-PCDA with polymers, such as polyvinyl alcohol, polyvinylidene fluoride and cellulose increase the blue to red transition temperature without affecting the irreversibility of the red phase. However, the addition of zinc oxide to pure poly-PCDA makes the red phase highly reversible and substantially increases the blue to red transition temperature. The addition of TiO2 to poly-PCDA on the other hand does not affect the irreversibility of the red phase and the chromatic transition temperature. In order to understand the atomic scale interactions associated with these changes in the chromatic transitions, we have investigated both the nanocomposites and polymer blends using Raman and Fourier-transform infrared spectroscopy, and extended X-ray absorption fine structure (EXAFS) measurements

Two photon photopolymerization (2PP) is a new and modern method in solid freeform fabrication. 2PP allows the fabrication of sub-micron structures from a photopolymerizable resin. By the use of near-infrared (NIR) lasers it is possible to produce 3D structures with a spatial feature resolution as good as 200 nm. This technique can be used in polymer-based photonic and micro-electromechanical systems (MEMS), for 3D optical data storage or for the inscription of optical waveguides based on a local refractive index change upon laser exposure. Since the 2PP only takes place inside the focus of the laser beam, complex 3D-structures can be in-scri-bed into a suitable matrix material.

In the presented work, 2PP is used to write optical waveguides into a prefabricated mechanically flexible polydimethylsiloxane matrix. The waveguides were structured by selectively irradiating a polymer network, which was swollen by a monomer mixture. The monomer was polymerized by two photon photopolymerization and the uncured monomer was removed by evaporation at elevated temperatures. This treatment led to a local change in refractive index in the order of Δn = 0.02, which was significantly above the industrial requirement of Δn = 0.003. The measured optical losses were around 2.3dB/cm. Since all unreacted monomers were removed by eva-po-ration, the final waveguide was stable up to temperatures of more than 200°C.

In a second approach highly porous sol-gel materials (based on tetramethoxysilane (TMOS) as precursor and the surfactant cetylpyridinium chloride monohydrate as structural temp-late) were utilized as matrix materials. The precursor was organically modified with poly(ethylene glycol) spacers in order to increase the toughness and thus facilitate the fabrication of transparent porous monoliths and flexible films. The pores of the sol-gel-derived matrix were filled with acrylate-based monomers of high refractive index and after selective irradiation using 2PP waveguides (Δn = 0.015) could be written into the material.

Starting from a bio-based polyol through modification of soybean oil, BIOH™ X-210, two series of bio-based polyurethanes-clay nanocomposite foams have been prepared. The effects of organically-modified clay types and loadings on foam morphology, cell structure, and the mechanical and thermal properties of these bio-based polyurethanes-clay nanocomposite foams have been studied with optical microscopy, compression test, thermal conductivity, DMA and TGA characterization. Density of nanocomposite foams decreases with the increase of clay loadings, while reduced 10% compressive stress and yield stress keep constant up to 2.5% clay loading in polyol. The friability of rigid polyurethane-clay nanocomposite foams is high than that of foam without clay, and the friability for nanofoams from Cloisite® 10A is higher than that from 30B at the same clay loadings. The incorporation of clay nanoplatelets decreases the cell size in nanocomposite foams, meanwhile increases the cell density; which would be helpful in terms of improving thermal insulation properties. All the nanocomposite foams were characterized by increased closed cell content compared with the control foam from X-210 without clay, suggesting the potential to improve thermal insulation of rigid polyurethane foams by utilizing organically modified clay. Incorporation of clay into rigid polyurethane foams results in the increase in glass transition temperature: the Tg increased from 186 to 197 to 204 °C when 30B concentration in X-210 increased from 0 to 0.5 to 2.5%, respectively. Even though the thermal conductivity of nanocomposite foams from 30B is lower than or equal to that of rigid polyurethane control foam from X-210, thermal conductivity of nanocomposite foams from 10A is higher than that of control at all 10A concentrations. The reason for this abnormal phenomenon is not clear at this moment; investigation on this is on progress.

As electronic systems are scaling down further and further, there is the constant need to utilize all the board area with maximum efficiency. Since passive components occupy most of the space on boards, it is very important to scale them down. New techniques allow for “integrated” passives as opposed to their discrete counterparts. Integrated capacitors can be embedded within the substrate, leaving room for other components on the board surface. In order to improve the area efficiency of these integrated capacitors, researchers have formed multilayered capacitors in the past. This increases the capacitance density, but is time consuming and expensive due to too many process steps. With increased circuit density, a currently demonstrated dielectric, Ta2O5, could be replaced with a potential high-k dielectric that can store more charge in a smaller area than a capacitor with Ta2O5. Niobium pentoxide (Nb2O5) with k∼41 is an emerging dielectric for high-k capacitor applications. This paper investigates niobium pentoxide as a next generation high-k planar capacitor dielectric. Niobium pentoxide dielectric was formed by reactive sputtering and anodization. Dielectric characterization was done using X-ray photoelectron spectroscopy (XPS), Transmission Electron Microscopy (TEM), and Atomic Force Microscopy (AFM). Thin film planar capacitor structures were fabricated using Nb2O5 dielectric and electrically characterized. The results presented include dielectric material characterization, design, capacitance, and breakdown voltage measurements.

We previously reported the synthesis of nanostructured composite PbTe with excess Pb and Sb metal inclusions. The electrical conductivity shows an unusual temperature dependence that depends on the inclusion Pb/Sb ratio, resulting in marked enhancements in power factor and ZT at 700 K. Additional investigation of the transport and structure of these materials is reported here. Measurements of the scattering parameter reveals there is little change in electron scattering with respect to pure PbTe. High resolution electron microscopy was used to determine additional information about the nature of the precipitate phases present in the samples. High temperature transmission electron microscopy reveals that the precipitates begin to dissolve at high temperatures and completely disappear at T > 619K. A qualitative explanation of the unusual transport behavior of these materials is presented.