A detailed description of the phenomenon of catastrophic optical-damage (COD) in short (380μm cavity-length), 12μm aperture, proton-bombarded, double-heterostructure laser-diodes with uncoated facets was first presented in 1974.In these devices, COD generally initiates at the facets due to high optical-power density and propagate along transverse-mode filaments. To achieve reliable operation at high optical-power, broad-area laser-diodes have evolved to long (several-millimeter cavity-length), wide-aperture (50-200μm), dielectric-defined, broadened-waveguide, separate-confinement, double-heterostructure, quantum-well laser-diodes with coated, passivated facets. COD in these devices involve both transverse modes and ring-cavity modes.

We report the terahertz (THz) emission from the wurzite indium nitride (InN) films grown by molecular beam epitaxy (MBE). More than two orders of magnitude of THz power enhancement has been achieved from the InN film grown along the a-axis and magnesium (Mg) doped InN with a critical carrier concentration. The primary radiation mechanism of the a-plane InN film is found to be due to the acceleration of photoexcited carriers under the polarization-induced in-plane electric field perpendicular to the a-axis. Apparent azimuthal angle dependences of THz wave amplitude and the second harmonic generation are observed from a-plane InN. In the Mg-doped films, Mg as the acceptors compensate the native donors in the InN films and large band bending over a wider space-charge region causes the enhancement of THz emission power compared to the undoped InN.

One of the new applications of focused Ga ion beam (Ga FIB) techniques to fabricate micro fluid channels on plate glass was demonstrated. After discussing features of the FIB etched patterns, narrow channel or Y-shaped channels were fabricated by FIB etching on a patterned plate glass which was prepared by photo-lithography and wet etching processes. Micro fluid devices were then constructed using polydimethylsiloxane (PDMS) sheet and silicone rubber tubes and the water (or ink) flow in the devices was observed under a microscope using a syringe pump. Although no discussion based on fluid mechanics has done at present, the present results indicate a possibility of applying FIB techniques to fabricate micro fluid devices which can be used in bio- and/or chemical-related fields.

In this investigation the swelling pressure of confined samples of a real waste form, consisting of bitumen containing washing water concentrate, was measured. The theoretically reachable swelling pressure was estimated as high as ∼ 273 bar (27 MPa).

A first simple experimental set-up was a sample of bituminized radwaste embedded in a cylinder of sintered bronze with a piezo-resistive pressure transducer. This was put into a leaching medium. A maximum pressure of 2 bar (0.2 MPa) was measured. The leaching rates of these confined samples were similar to those of unconfined ones.

The second set-up was a sample of bituminized radwaste embedded in a cylinder of stainless steel, also equipped with a pressure transducer. The open bottom of the cylinder was closed with a disc of porous cement with water/cement ratio of 1.3. In two similar experiments with this set-up the swelling pressure reached in one case a value of 9 bar = 0.9 MPa and in the second improved one about 15 bar = 1.5 MPa.

Lanthanide-Borosilicate (LaBS) glass capable to dissolve up to ∼10 wt.% PuO2 is designed for immobilization of plutonium-bearing wastes. The sample of LaBS glass with a target chemical composition (wt %): 9.0 Al2O3, 11.8 B2O3, 12.2 Gd2O3, 6.3 HfO2, 17.2 La2O3, 13.6 Nd2O3, 9.5 PuO2, 18.1 SiO2, 2.3 SrO was prepared from PuO2 powder and mechanically activated mixture of chemicals at 1500 °C. The obtained product was visually homogeneous. Xraydiffraction of the as-prepared glass showed that it mostly consists of a vitreous phase withsmall amounts of crystalline PuO2 (or PuO2-HfO2 solid solution with minor HfO2), britholite andan oxide with a fluorite structure and a composition close to GdHfO1.75. The crystalline fractionincreased after storage for ∼1 year. Magnitude of the FT of EXAFS spectrum at Pu LIII edgeshows that the peak due to first coordination sphere is much more intense than that of the secondshell. This indicates that though some Pu entered crystalline phases (mainly distorted PuO2), itsmajor fraction remained in the vitreous phase. Fit of the spectrum (R-factor = 0.02) gives thefollowing distances: R (Pu-O1)1 = 1.98 (σ = 0.04), R (Pu-O1)2 = 2.18 (σ = 0.04), R (Pu-O1)3= 2.35, R (Pu-Pu) = 3.72 (σ = 0.04), R (Pu-O2) = 4.4 (σ = 0.06). Oxygen environment ofthe Pu4+ ions in the vitreous phase resembles axially squeezed tetragonal pyramid with acoordination number ∼5. The distances ∼2.35 and ∼4.4 correspond to the pairs Pu-O in thefirst and the second shells in the crystalline PuO2. The distance ∼3.72 corresponds to the Pu-Pu and/or Pu-M (M = Ln, Hf) distances. EXAFS spectra of Hf show that Hf is present mostly in thevitreous phase with major neighbors at 2.17 and ∼3.2 A.

In preparation for actual repository implementation, designs that could be tailored to specific sites need to be considered. This requires a paradigm shift in design philosophy, moving away from a single reference design towards a flexible and systematic “catalogue” of engineered barrier components and associated repository infrastructure. To support this development, novel methodology for both developing and comparing repository design options for Japanese vitrified high-level radioactive waste (HLW) has been examined. This paper will outline the background of the project and, in particular, some novel approaches examined for facilitating optimisation of practical repository designs. It is complemented by a companion paper - Matsumoto et al: Application of Formal Knowledge Engineering Approaches to Develop A Design Catalogue for A Japanese HLW Repository -, which describes the repository design process in more detail and illustrates results of first dry runs of the methodology.

The choice of surrogate for plutonium oxide for use during the initial stages of research into the immobilization of intermediate level pyrochemical wastes containing plutonium andamericium oxides in a calcium phosphate host has been investigated by powder X-ray diffraction and X-ray absorption spectroscopy. Two non-radioactive surrogates, hafnium oxide and cerium oxide, together with radioactive thorium oxide were compared. Similarities in behaviour were observed for all three surrogates when calcined at the lowest temperature, 750°C but differences became more pronounced as the calcination temperature was increased to 950°C. Although some reaction occurred between all the surrogates and the host to form a substituted whitlockite phase, increasing the temperature led to a significant increase in the cerium reaction and the formation of an additional phase, monazite. Additionally it was observed that the cerium became increasingly trivalent at higher temperatures.

Conductive Atomic Force Microscopy was applied to study the lateral uniformity of current transport at the interface between graphene and 4H-SiC, both in the case of epitaxial graphene (EG) grown on the Si face of 4H-SiC and in the case of graphene exfoliated from HOPG and deposited (DG) on the same substrate. This comparison is aimed to investigate the role played by the C-rich buffer layer present at EG/4H-SiC interface and absent in the case of DG/4H-SiC. The distribution of the local Schottky barrier heights at EG/4H-SiC interface (ΦEG) was compared with the distribution measured at DG/4H-SiC interface (ΦDG), showing that ΦEG (0.36±0.1eV ) is ˜0.49eV lower than ΦDG (0.85 ± 0.06eV). This difference is explained in terms of the Fermi level pinning ˜0.49eV above the Dirac point in EG, due to the presence of positively charged states at the interface between the Si face of 4H-SiC and the buffer layer.

We have been investigating fabrication of a crystallized Si (c-Si) film deposited on a glass substrate at low temperature, using a poly-yttria-stabilized zirconia (poly-YSZ) film as a seed layer. It can be expected that the crystallographic information of the YSZ layer transmits to the deposited Si film so that it stimulates its crystallization even at lower temperature. To reduce the crystallization temperature further, we focused on the surface treatment of the YSZ layer, in which it was dipped in the HF solution, followed by rinsing with deionized water (DIW) or with ethanol.

After depositing the poly-YSZ layer by reactive magnetron sputtering on the quartz glass substrate, the Si film was deposited directly on it by e-beam vacuum evaporation in <10-6 Pa. The Raman spectra of the Si films deposited at 430 °C on the ethanol-rinsed glass without YSZ layer and on the DIW-rinsed YSZ layer showed amorphous phase. However, on the ethanol-rinsed YSZ layer, they showed a strong peak of c-Si of the deposited film, even at 350 °C, and indicated the beginning of the crystallization at 320 °C. This means that the YSZ layer enhanced the Si film crystallization, and that the ethanol-rinse was effective for low-temperature crystallization. The crystalline fraction of the Si film varied with the yttria content and the surface treatment of the YSZ layer prior to the Si film deposition. From the XPS results, we found out that fluorine F were adsorbed on the surface and were bonded with the Y. The Y 3d and F 1s peaks observed from the ethanol-rinsed YSZ were higher than those of the DIW rinse, which suggests that the Y and adsorbed F on the surface were removed by the DIW rinse, but remained even after the ethanol rinse. Based on the Raman and XPS results, we can speculate that the excessive amount of F on the YSZ layer surface prior to the Si film deposition play an important role on the Si film crystallization. We observed the surface of the Secco-etched Si/YSZ films deposited at 320, 350, and 430 °C by SEM. The number of crystallized Si grains was denser at higher temperature than that of lower temperature. That is, the Si film deposited at 430 °C was crystallized thoroughly on the whole substrate, but some regions of the Si films deposited at 350 and 320 °Cwere amorphous and removed by the Secco etching. The grain sizes were in the range from 20 to 40 nm, and the size at the lower deposition temperature was more uniform than the higher temperature. From SIMS observation, it was found that Zr atoms diffuse from the interface with the YSZ layer.

CdS is an important part of CIGS-based photovoltaics as a buffer layer between the absorber and the window layer. Chemical Bath Deposition (CBD) is the most common way of depositing CdS. Due to the nature of the CBD process CdS forms not only on the absorber layer surface but also in the bulk solution. In order to control the deposition of CdS at the surface and to avoidCdS formation in the bulk solution the kinetics of these reactions must be understood. In this work we study the formation of CdS in the chemical bath by using in situ spectroscopic extinction measurements. By monitoring the absorbance of the solution we are able to observe the bulk phase reaction (chemical formation of CdS in solution). Deposition of CdS (growth of the CdS layer at the surface) is investigated by measuring the CdS layer thickness after the reaction. The kinetics of both reactions were investigated by a systematic variation of temperature, initial reactant concentration, Reynold number as well as time. Finally the results of our study suggest a model of growth behaviour based on molecule-by-molecule deposition, which explains especially the dependency on temperature and hydrodynamics.

The effect of He plasma pretreatment on interaction of O and H atoms with SiCOH low-k materials is studied using a special experimental system designed for this purpose. The experimental system allowed separate study of the effects of He plasma, VUV light and He 21S0 metastable atoms. It is shown that the carbon depletion by oxygen atoms can be significantly reduced by He plasma pretreatment. Considerable increase of CH and CH2-CH2 groups in the surface area of low-k films is observed when the films were exposed to VUV light and metastable atoms generated by He plasma. FTIR and ellipsometry showed formation of densified surface layer. This carbon rich densified surface layer decreases damage of low-k film when it is exposed in O2 plasma. The impact of H atoms on low-K surface noticeably differs from O atoms effect. The H atoms saturate all unbounded remaining carbon bonds thereby promoting improvement of SiOCH structure.

Control of residual stress in thin films is critical in obtaining high mechanical quality coatings without cracking, buckling, or delamination. In this work, we present a simple and effective method of residual stress reduction in sputter deposited thin films by stacking low and high material density layers of the same material. This multilayer density modulated film is formed by successively changing working gas pressure between high and low values, which results in columnar nanostructured and dense continuous layers, respectively. In order to investigate the evolution of residual stress in density modulated thin films, we deposited ruthenium (Ru) films using a DC magnetron sputtering system at alternating argon (Ar) pressures of 20 and 2 mTorr. Wafer’s radius of curvature was measured to calculate the intrinsic thin film stress of multilayer Ru coatings as a function of total film thickness by changing the number of high density and low density layers. By engineering the film density, we were able to reduce film stress more than one order of magnitude compared to the conventional dense films produced at low working gas pressures. Due to their low stress and enhanced mechanical stability, we were able to grow these density modulated films to much higher thicknesses without suffering from buckling. Morphology and crystal structure of the thin films were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). A previously proposed model for stress reduction by means of relatively rough and compliant sublayers was used to explain the unusually low stress in the specimens investigated.

The alkali niobate ferroelectrics ((K0.5Na0.5)NbO3, KNN) are promising candidates as alternatives for PZT (Pb(ZrxTi(1-x))O3) ceramics in piezoelectric technologies. In order to obtain dense compounds with desirable properties, CuO has been used as sintering aid. In this work, the defect chemistry of Cu2+ doped KNN was investigated by means of electron paramagnetic resonance (EPR). Copper is found to be incorporated as acceptor-type centers on B-site in the perovskite structure and, due to charge compensation, two kinds of mutually compensating defect dipoles are formed.

Thin films of CuInSe2 (CIS) and CuGaSe2 (CGS) were deposited on (100) Si substrates by RF magnetron sputtering using stoichiometric targets, at various substrate temperatures. Prior to film deposition, the Si substrates were cleaned using the RCA cleaning procedure and treated in a buffered oxide etch (BOE) solution. Deposited films were characterized using Rutherford backscattering spectroscopy (RBS), transmission electron microscopy (TEM) of cross-sectional samples and Hall measurements. Rutherford backscattering analysis indicated that the CIS films had a composition of Cu0.8In1.1Se1.9, whereas CGS films were Cu-poor and Ga-rich with a composition of Cu0.3Ga1.5Se1.5. Clean Cu-chalcopyrite/Si interfaces were obtained using BOE treated Si substrates. Transmission electron micrographs of cross-sectional samples indicated a polycrystalline film structure and that the native oxide on the Si substrate was eliminated. Energy dispersive X-ray spectroscopy (EDS) conducted in the TEM showed that contamination levels in the films were low. The Hall-mobility experiments performed the CIS film indicated that the material was of p-type conductivity with a carrier concentration of 9.6 x 1020/cm3 and a Hall mobility of 390 cm2V-1s-1.

The effects of the components of extracellular matrix on the bone formation and the kinetics of crystal growth of calcium phosphate have remained unknown. In this paper, we reported a method to investigate the role of Type I collagen and the interactions with other ECM proteins such as fibronectin and elastin during biomimic mineralization process in vitro. The early stage of mineralization was characterized by scanning probe microscopy (SPM) and shear modulation force microscopy (SMFM). The late stage of mineralization was investigated by synchrotron grazing incident x-ray diffraction (GIXD). The results demonstrate the cooperative interaction between type I collagen and noncollagenous proteins such as fibronectin or elastin could be essential for the biomineralization.

In recent years, the increasing energy costs have lead to power utility industries to seek/develop high efficiency systems of production and of energy utilization. In addition, environmental concerns regarding greenhouse gas emissions are playing a major role in the development of clean energy systems. The development of metallic materials that can withstand elevated temperatures is among the viable alternatives to increase energy efficiency. Nevertheless, for this to happen, the corrosion and oxidation resistance of Fe- and Ni-based alloys needs to be significantly improved. Among the possible ways to enhance the life of high temperature alloys is the application of protective ceramic coatings. Conventional coatings are expensive and the protective effects controversial at times. An alternative which offers a great potential is the application of nano-ceramic coatings. Hence, in this work nanocrystalline coatings based on nano-CeO2 are applied to an austenitic stainless steel 304L and then exposed to elevated temperatures. Weight changes are monitored as a function of time and the results are compared with uncoated alloys tested under similar conditions. In addition, computer simulations of possible rate limiting diffusion mechanisms are carried out. It is found that the nanocoatings provided remarkable high-temperature oxidation resistance and improved scale adhesion. In particular, it is found that the smaller the nanoparticles are, the more effective the nanocoatings in providing oxidation resistance.

Many different sandwich panels are used for aeronautical applications. Open and closed cell structured foam, balsa wood or honeycomb are often used as core materials. When the core material contains closed cells, water accumulation into the cell has to be taken into account. This phenomenon occurs when in service conditions lead to operate in humidity atmosphere. Then, water vapor from air naturally condenses on cold surfaces when the sandwich panel temperature decreases. This water accumulation might increase significantly the weight of the core material. Core with a ventilated structure helps to prevent this phenomenon. Periodic cellular metal (PCM) has been motivated by potential multifunctional applications that exploit their open architecture as well as their apparent superior strength and stiffness: pyramidal, lattice, Kagome truss or woven. One of the drawbacks of these materials is the expensive cost of the manufacturing. Recently, a novel type of sandwich has been developed with bonded metallic fibers as core material. This material presents attractive combination of properties like high specific stiffness, good damping capacity and energy absorption. Metal fibers bonded with a polymeric adhesive or fabricated in a mat-like form consolidated by solid state sintering. Entangled cross-linked carbon fibers have been also studied for using as core material by Laurent Mezeix. In the present study, ventilated core materials are elaborated from networks fibers. The simplicity of elaboration is one of the main advantages of this material. Multifunctional properties are given by mixing different sorts of fibers, by example adding fibers with good electrical conduction to give electrical conductivity properties.In this study network fibers as core material are elaborated using carbon fibers, glass fibers and stainless steel fibers. In aeronautical skins of sandwich panels used are often carbon/epoxy prepreg, so epoxy resin was used to cross-link fibers. The core thickness was chosen at 30 mm and fibers length was chosen at 40 mm. Entanglement, separation of filaments and cross-linking are obtained in a specific blower room. Fibers are introduced in the blower room, compressed air is applied and in same time epoxy resin is sprayed. Indeed one of the sandwich core material properties required is low density, so yarns size need to be decreased by separating filaments. Network fibers are introduced in a specific mould and then are compressed. The density obtained before epoxy spaying is 150 kg/m3. Finally samples are polymerized at 80°C for 2 hours in a furnace under laboratory air. Compressive behavior is study to determinate the influence of fibers natures and the effect of cross-linking. Reproducibility is also checked.

There has been a significant effort to create spiral sensors by changing either the periodic d-spacing of the structure or the dielectric constants of the materials by combining the multi-faceted environmental responsiveness of polymer hydrogels with dielectrical structures.1 Reversible spiral switches with dimensional functionalities that respond to chemical environment were constructed. When the spiral photonic actuator was swollen in hydrophilic acetic acid, right-handed spiral structures are formed, while the spiral photonic actuator was swollen in hydrophobic hexane, left-handed spiral structures are formed. All actuators returned back to the transparent planar state after deswelling processes. These reversible spiral photonic actuators can be applied in the application of mechanical actuators, electrical devices, and optical components.

Lateral nMOSFETs have been fabricated on 4H-SiC utilizing deposited dielectrics and gate-last processing. A bi-layer dielectric was utilized consisting of thin nitrided SiO2 covered by 25nm of Al2O3 deposited using atomic layer deposition. Field-effect mobility and threshold voltage (VT) were found to vary with SiC nitric oxide (NO) anneal temperature. High peak mobility values of 106 cm2/V·s were obtained, with a corresponding VT of 0.8 V, using an 1175 °C 20 min NO anneal of the SiC before Al2O3 deposition. Constant voltage stressing (CVS) of the gate (3 MV/cm) for 1000s induces a VT increase of only 0.12 V for the devices stressed at RT, whereas a VT shift of 0.34 V occurs for devices stressed at 150 °C. Heating unstressed devices to 200 °C reveals a stable VT with temperature. Negative charge in the gate region allows for the attainment of positive VT, while VT stability does not suffer.

Low- and intermediate-level operational waste from the Swedish nuclear power plants is stored in the SFR repository. The facility is located in the bedrock at a depth of approximately 50 m and has been in operation for 20 years. According to present plans, all Swedish nuclear power plants will have been decommissioned by the end of the 2040s. The decommissioning phase will start by initially decommission the two Barseback reactors that have been non-operational since 1999 and 2005. In order to host the decommissioning waste, the storage volume of the SFR repository must be extended with approximately 140,000 m3. To do this, a project is ongoing with the objective of submitting an application to extend SFR by 2013 and the superior aim of having the facility in operation year 2020.