A plutonia stabilised zirconia doped with yttria and erbia has been selected as inert matrix fuel (IMF) at PSI. The results of experimental irradiation tests on yttria-stabilised zirconia doped with plutonia and erbia pellets in the Halden research reactor as well as a study of zirconia solubility are presented. Zirconia must be stabilised by yttria to form a solid solution such as MAz(Y,Er)yPuxZr1-yO2-ζ where minor actinides (MA) oxides are also soluble. (Er,Y,Pu,Zr)O2-ζ (with Pu containing 5% Am) was successfully prepared at PSI and irradiated in the Halden reactor. Emphasis is given on the zirconia-IMF properties under in-pile irradiation, on the fuel material centre temperatures and on the fission gas release. The retention of fission products in zirconia may be stronger at similar temperature, compared to UO2. The outstanding behaviour of plutonia-zirconia inert matrix fuel is compared to the classical (U,Pu)O2 fuels. The properties of the spent fuel pellets are presented focusing on the once through strategy. For this strategy, low solubility of the inert matrix is required for geological disposal. This parameter was studied in detail for a range of solutions corresponding to groundwater under near field conditions. Under these conditions the IMF solubility is about 109 times smaller than glass, several orders of magnitude lower than UO2 in oxidising conditions (Yucca Mountain) and comparable in reducing conditions, which makes the zirconia material very attractive for deep geological disposal. The behaviour of plutonia-zirconia inert matrix fuel is discussed within a burn and bury strategy.

We compute the strain fields and the interactions between dislocations at the junctions of classical small-angle grain boundaries. It is shown that, in contrast with the results for infinite small-angle boundaries, there are always forces acting on the dislocations in the arrays that define the grain boundaries, and that there is also an excess elastically stored energy associated with the triple junction (TJ). The forces on the dislocations and the excess stored energy of the TJ are shown to vary with the dihedral angles formed by the grain boundaries, and that the “equilibrium” dihedral angle based upon the Herring equation and the energies of the individual grain boundaries does not correspond to any kind of force or energy minimum. This relates to an unwarranted assumption in Herring's original derivation, that no interactions occur between the grain boundaries that make up a TJ.

The thermal oxidation kinetics of Si(110) surface up to oxide layer thickness of 1 ML has been investigated by real-time monitoring of chemical shifted in the Si 2p core-level photoemission using synchrotron radiation. The uptake profiles of every Si oxidation states (Sin+: n = 1 − 4) indicate that the top surface Si(110) oxidation proceeds through a two-step oxidation pathway via Si2+ state, just like the Si(001) surface. In contrast to the Si(001) oxidation, however, Si3+ state is always more abundant than Si4+ state during oxidation. This is related to occurrence of imperfect oxidation of this surface, most probably due to accumulation of compressive strain during oxidation.

High quality MIM capacitors with improved capacitance density, low leakage currents and linear C(V) behaviour are the object of active research, with potential applications in CMOS, BICMOS and bipolar technologies as filters, analog to digital converters and related radio-frequency operating devices. Several high-k materials (Ta2O5, HfO2, Y2O3, Al2O3-HfTiO, HfON-SiO2) have been put on trial as possible candidates for SiO2 substitution which is required by the aggressive downscaling of electronic devices. Among those, HfO2- based materials seem to offer promising properties, combining a high chemical stability with Si and a high k value. However, HfO2 shows a strong ability to favour charge defects such as oxygen vacancies, which in turn affect the intrinsic properties of devices such as threshold voltage or leakage currents. These oxygen vacancies are actually thought to accumulate in the vicinity of the electrode, thus forming an oxidized interfacial layer and inducing a significant voltage linearity degradation of MIM capacitors.

In this work, it will be shown that this oxide layer thickness can be strongly minimized by using appropriate bottom electrode material. Indeed, high work function materials can efficiently prevent oxygen vacancies charge stocking on their surface. Several MIM devices have been prepared based on HfO2, Al2O3 and SrTiO3 as dielectric materials, and TiN, WSi2.7 and Pt as bottom electrode material. All these devices have been fully characterized in terms of materials properties and electrical behaviour. These results have been analysed and show that a reduced dielectric thickness is preferred to achieve high capacitance density, but is also responsible for voltage linearity degradation. High work function electrode material can help improve this degraded linear behaviour, thanks to the formation of a reduced interfacial oxygen trap layer thickness. Leakage currents seem to be deeply correlated with the morphological state of the dielectric material, an amorphous state being obviously more efficient to prevent current pathways through grain boundaries.

All these results will be presented in detail and discussed with regards to different models proposed in the literature to account for these data.

This paper presents an approach to model quantum mechanical effects in solid-state devices such as Metal Oxide Semiconductor (MOS) capacitor with and without nanocrystal in the oxide at the device simulation level. This quantum-mechanical model is developed to understand finite inversion layer width and threshold voltage shift. It allows a consistent determination of the physical oxide thickness based on an agreement between the measured and modeled C-V curves. However, as for thinner oxides finite inversion layer width effects become more severe, quantum-mechanical model predicts higher threshold voltage than the classical model. The inversion-layer charge density and MOS capacitance in multidimensional MOS structures are simulated with various substrate doping profiles and gate bias voltages. The effectiveness of the QM correct method for modeling quantum effects in ultrathin oxide MOS structures is also investigated. The CV characteristic is used as a tool to compare results of the QM correction with that of the Schrödinger–Poisson (SP) solution and Classical solution The variation of (different parameters) for various doping profiles at different gate voltages is investigated.

Thin films composed of poly(ethylene imine)-functionalized single-walled carbon nanotubes (CNTs) were formed through a vacuum filtration process and decorated with Au nanoparticles, roughly 40 nm in diameter. The Au nanoparticles, on the surface of the CNT fabric, accommodated the growth of GaAs nanowires (NWs), according to the vapour-liquid-solid (VLS) mechanism, in a gas-source molecular beam epitaxy (GS-MBE) system. Structural analysis indicated that the nanowires, up to 2.5 μm in length, were not preferentially oriented at specific angles with respect to the substrate surface. The NWs grew in the energetically favored [0001] direction of the wurtzite lattice while stacking faults, characterized as zincblende insertions, were observed along their lengths. Micro-photoluminescence spectroscopy demonstrated bulk-type optical behaviour. Current-voltage behaviour of the core-shell pn-junction heterostructured NWs exhibited asymmetric rectification. Thus, the potential for the incorporation of such hybrid NW/CNT architectures into an emerging class of flexible opto-electronic devices is demonstrated.

In this work, a possibility to further suppress silicon vapor condensation and formation of Si clusters in order to improve the growth rate and morphology during the low-temperature halo-carbon epitaxial growth of 4H-SiC was investigated. While a pronounced dissociating of Si clusters was clearly demonstrated, the enhancement of the growth rate and morphology was less significant then expected. In addition, the homogeneity of the growth rate and doping along the gas flow direction indicated that a significant and non-equal depletion of Si and C growth species takes place at sufficiently high HCl supply. HCl flow-dependent formation of polycrystalline Si and SiC deposits in the upstream portion of the hot zone was shown to be the source of this depletion.

Gelatin has been widely used to develop tissue engineering scaffolds because it has many attractive properties. Dendrimer provides a versatile, compositionally and structurally controlled architecture to construct nanomedicine. This study was aimed at developing a novel electrospun dendrimer-gelatin nanofiber scaffold to best mimic natural extracellular matrix (ECM) to promote tissue formation and serve as a reservoir for controlled drug delivery. Starburst™ polyamidoamine (PAMAM) dendrimer G3.5 was covalently bonded to the gelatin backbone and electrospun into nanofibers. Doxycycline (DC), which is an effective antibiotic that has the ability to inhibit matrix metalloproteinase, was encapsulated into the nanofiber scaffold. The electrospun DC-gelatin scaffold provides a bacterial free environment for cell growth and tissue regeneration. The resulting dendrimer-gelatin nanofiber scaffold achieved a unique structural configuration where covalently bound three-dimensional dendritic nanospheres were evenly distributed along the elongated dimension of the nanofiber, and both dendrimer and gelatin had numerous functional groups suitable for accommodating multiple functional entities and high payload of drugs. The development of this new scaffold with the capability of delivering multiple functional entities was an important step towards the use of bioactive nanofibers to facilitate tissue regeneration and controlled drug release.

Doping of thin body Si becomes very essential topic due to increasing interest of forming source/drain regions in fully depleted planar silicon-on-isolator (SOI) devices or vertical Fin field-effect-transistors (FinFETs). To diminish the role of the short-channel-control-effect (SCE) the Si layers thicknesses target the 10 nm range. In this paper many aspects of thin Si body doping are discussed: dopant retention, implantation-related amorphization, thin body recrystallization, sheet resistance (Rs) and carrier mobility in crystalline or amorphized material, impact of the annealing ambient on Rs for various SOI thicknesses. The complexity of 3D geometry for vertical Fin and the vicinity of the extended surface have an impact on doping strategies that are significantly different than for planar bulk devices.

One-way to improve organic solar cell efficiency is blending conjugated polymer with a second nanocomposite. We report on blending of freestanding boron- and phosphorous-doped environmental friendly silicon nanocrystals (Si-ncs) with two conjugated polymers i.e. (poly(3-hexylthiophene) (P3HT) and poly[methoxy-ethylexyloxy-phenylenevinilene] (MEH PPV)). The electrochemical etching and pulverization of doped porous silicon films are used for fabrication of photesensitive Si-ncs/polymers blends. Processing of Si-ncs dispersed in polymers allows simple tuning of the Si-ncs concentrations in the blends. The blends with high Si-ncs concentrations are prepared and opto-electric properties are compared and discussed. Both types of polymers containing doped Si-ncs showed a photoconductivity response under illumination AM1.5 at ambient temperature and atmosphere.

We report dye-sensitized solar cells using low cost carbon nanoparticles as an alternative to platinum as a counter-electrode catalyst for triiodide reduction.The counter carbon-electrode was deposited onto fluorine-doped tin oxide (FTO) by spin coating from an aqueous colloidal suspension of the blend of carbon nanoparticles and TiO2 nanocrystals.DSSC devices were fabricated using a stable Ru complex dye (Z-907) as the sensitizer.The cells based on carbon-nanoparticle counter electrode were made and then compared with those cells from platinum counter electrode at similar fabrication conditions.The results have shown that the device performance in terms of short circuit current density (Jsc), open circuit voltage (Voc) and energy conversion efficiency (η) from the cells based on carbon nanoparticle counter electrode were comparable to those from platinum counter-electrode devices.The carbon nanoparticle based cells have achieved an overall energy conversion efficiency of 5.55% under one sun AM 1.5 illumination (100 mW/cm2). The carbon nanoparticles showed significant potential as a low cost alternative to the current widely-used platinum.

A perpetual increase in population and thus consumption of fossil fuels has led to increased pollution worldwide. Pollution in large metropolitan cities has reached an alarming level and is widely believed to be the leading contributor to chronic and deadly health disorders and diseases affecting millions of people each year. Although correlation between environmental pollution and global warming is debatable, the effects of pollution and its impact on human health are irrefutable and highly observable. Use of nanomaterials to generate energy, in an attempt to reduce environmental pollution, is in its preliminary stages and requires urgent and detailed investigation. This investigation focuses on three aspects of sustainability, (a): use of nanomaterials to monitor, detect, and remediate the environmental pollution, (b): responsible manufacturing of nanomaterials by employing principles of “green chemistry”, and (c): to drastically reduce waste and emission by-products employing use of nanomaterials as catalysts for enhanced efficiency. The synthesis of nanomaterials is accomplished by processes employing processes such as electrospinning, sol-gel, and MAPLE to drastically reduce and isolate emission and waste by-products. An exhaustive overview of the scope of our investigation and some specific applications relating to the use of nanomaterials in environmental friendly investigations, viz.; applications of nanomaterials as catalysts for enhanced efficiency, materials in CO2 sequestration, remediation of toxic metals in water streams, efficient thin film photovoltaic devices, fuel cells, and biodegradable consumable products is described. Fate and transport of nanomaterials in air, water, and soil; life-cycle analysis, and methodologies to conduct risk-assessment in the context of source reduction and conservation is discussed as a step towards sustainability.

The classical double well potential (DWP) model known to explain many phenomena in glasses, is extended to the nano glasses of chalcogenide phase change memory (PCM). We describe simple analytical expressions for the temporal drift of PCM reset parameters. The threshold voltage Vth and the amorphous state resistance R are shown to drift with the time (t) as deltaVth ∝ ν propotional to ln t and R proportional to t power alpha respectively in broad intervals spanning many decades in time. These dependencies saturate at long enough times that can be shorten with temperature increase. All the available data on the PCM drift are shown to be fully consistent with DWP model.

Large area digital imaging made possible by amorphous silicon thin-film transistor (a-Si TFT) technology, coupled with a-Si photo-sensors, provides an excellent readout platform to form an integrated medical image capture system. Major development challenges evolve around optimization of pixel architecture for detector fill factor, and manufacturability, while suppressing noise stemming from pixel array and external electronics. This work discusses the behavior and modeling of system noise that arises from imaging array operations. An active pixel sensor (APS) design with on-pixel amplification is studied. Our evaluation demonstrates that a 17 inch by 17 inch array can achieve system noise as low as 1000 electrons through proper design and optimization.

We studied oxygen migration in calcia-stabilized cubic zirconia (CSZ) using density functional theory. A Ca atom was substituted for a Zr atom in a 2×2×2 ZrO2 cubic supercell, and an oxygen vacancy was produced to satisfy the charge neutrality condition. We found that the formation energies of an oxygen vacancy, as a function of its location with respect to the Ca atom, were varied. The relative formation energies of the oxygen vacancies located at the first-, second-, third-, and fourth-nearest-neighbors were 0.0, −0.07, 0.19, and 0.19 eV, respectively. Therefore, the oxygen vacancy located at the second-nearest-neighbor site of the Ca atom was the most favorable, the oxygen vacancy located at the first-nearest-neighbor site was the second most favorable, and the oxygen vacancies at the third- and fourth-nearest-neighbor sites were the least favorable. We also calculated the energy barriers for the oxygen vacancy migration between oxygen sites. The energy barriers between the first and the second nearest sites, the second and third nearest sites, and the third and fourth nearest sites were 0.11, 0.46, and 0.23 eV, respectively. Therefore, the oxygen vacancies favored the first- and second-nearest-neighbor oxygen sites when they drifted under an electric field.

Microgel particles of poly(2-vinylpyridine) cross linked with 0.5 wt% divinylbenzene were synthesised. Due to differences in the scattering of light, a dispersion of the particles appears opaque milky white above pH 4.5 and transparent below pH 4.5. The pH of a 0.15 wt% dispersion was modified using a poly(aniline) film as a source/sink of protons and a Ag/AgCl electrode as a source/sink of chloride counterions. The absorption of the sample at 400 nm was typically reduced from c.a. 3.5 to c.a. 0.5 in less than 20 minutes and increased to c.a. 3.2 in less than 20 minutes. This system could form the basis for a new type of display device, but it is insufficiently fast or consistent in its current form.

The radiochemical decomposition of molecules in storage environment which could lead to the corrosion of container or the formation of dangerous gas mixtures is a critical problem for radioactive materials. The complexity of the chemical system makes numerical models suitable for the reproduction mechanisms and the prediction of phenomena. In this study, a mathematical model for the dose rate distribution in external medium surrounding an α emitter actinide material has been proposed. The model has been implemented in a Monte Carlo scheme. An evaluation of the dose rate in the surrounding medium as a function of the sample size was shown and a discussion of the expected reactivity was made.

The immobilization of U(VI) by C-S-H phases under conditions relevant for the cementitious near field of a repository for radioactive waste has been investigated. C-S-H phases have been synthesized using two different procedures: the “direct reaction” method and the “solution reaction” method.

The stabilities of alkaline solutions of U(VI) (presence of precipitates or colloidal material) were studied prior to sorption and co-precipitation tests in order to determine the experimental U(VI) solubility limits. These U(VI) solubility limits were compared with the U(VI) solubilities obtained from thermodynamic speciation calculations assuming the presence of combinations of different solid U(VI) phases. The solid phase controlling U(VI) solubility in the present experiments was found to be CaUO4(s).

The U(VI) uptake kinetics and sorption isotherms on C-S-H phases with different C:S ratios were determined under various chemical conditions; e.g., sorption and co-precipitation experiments and different pH’s. U(VI) was found to sorb fast and very strongly on C-S-H phases with distribution ratios (Rd values) ranging in value between 103 L kg-1 and 106 L kg-1. Both sorption and co-precipitation experiments resulted in Rd values which were very similar, thus indicating that no additional sorption sites for U(VI) were generated in the co-precipitation process. Furthermore, C-S-H synthesis procedures did not have a significant influence on U(VI) uptake. The U(VI) sorption isotherms were found to be non-linear, and further, increasing Ca concentrations resulted in increasing U(VI) uptake. The latter observation suggests that U(VI) uptake is controlled by a solubility-limiting process, while the former observation further indicates that pure Ca-uranate is not the solubility-limiting phase. It is proposed that a solid solution containing Ca and could control U(VI) uptake by C-S-H phases.

This paper studies the impact of LTPS (low temperature polycrystalline silicon) TFTs with fluorine implantation under NBTI (Negative bias temperature instability) stress. The fluorinated TFTs' devices can obtain better characteristics with samller threshold voltage shift, lower trap states and lower subthreshold swing variation. Therefore, the fluorine implantation does not only improve initial electrical characteristics, but also suppresses the NBTI-induced degradation.

With the current level of actinide materials used in civilian power generation and the need for safe and efficient methods for the chemical separation of these species from their daughter products and for long-term storage requirements, a detailed understanding of actinide chemistry is of great importance. Due to the unique bonding properties of the f-elements, the lanthanides are commonly used as structural and chemical models for the actinides, but differences in the bonding between these 4f and 5f elements has become a question of immediate applicability to separations technology. This brief overview of actinide coordination chemistry in the Raymond group at UC Berkeley/LBNL examines the validity of using lanthanide analogs as structural models for the actinides, with particular attention paid to single crystal X-ray diffraction structures. Although lanthanides are commonly accepted as reasonable analogs for the actinides, these comparisons suggest the careful study of actinide materials independent of their lanthanide analogs to be of utmost importance to present and future efforts in nuclear industries.