In this paper, we will report on the formation of HfSixOy layer on an HF-last Si(100) substrate by atomic layer deposition from tetrakis(dimethylamido)hafnium (TDMAH) and atomic oxygen generated by a microwave remote plasma. Transmission electron microscopy observations of HfSixOy /Si structures deposited at 100 and 300℃ revealed that 3∼5-nm-thick amorphous HfSixOy layers were unintentionally formed preceded the growth of crystalline Hf-rich HfSixOy layers. To understand the mechanism of this unintentional growth of HfSixOy, the depth profiles of Hf, O and Si elements were measured by X-ray photoelectron spectroscopy. It was found that Hf atoms deeply diffused into the Si substrate. From these results, suppression of Hf in diffusion to the Si substrate must be important to reduce the capacitance equivalent thickness of the metal-oxide-semiconductor capacitors. The roles of TDMAH and plasma-generated oxygen radical on the enhanced diffusion of Hf will be discussed in detail.

NUMO and JAEA have been conducting a joint research since FY2011, which is aimed to enhance the methodology of repository design and performance assessment in preliminary investigation stage for the deep geological disposal of high-level radioactive waste. As a part of this joint research, we have been developing glass dissolution models which include various processes derived from glass-overpack-bentonite buffer interaction, considering the precipitation of Fe-silicates associated with steel overpack corrosion, and Si transport through altered layer of glass. The objective of this modeling work is to show comprehensively the lifetime of the vitrified waste due to glass matrix dissolution timescales through sensitivity analysis, and to identify the feature/process that most strongly influences the lifetime, and to identify future R&D issues that would help to improve the nuclide transport analysis with confidential value and the safety case in future. The sensitivity analysis suggested that the duration of the glass dissolution might be predicted in the ranges from 3.8×103 to 1.9×105 years. Also, the results indicated that the precipitation of Fe–silicate has the strongest influence on the long-team behavior of vitrified waste.

In an attempt to understand the structure and dynamics of ssDNA on graphene based surfaces, we performed all-atom implicit solvent molecular dynamics simulations of ssDNA on graphene and graphene oxide (GO) surfaces. Simulations indicate that adsorption of poly(A), poly(T) and poly (AT) have similar mechanisms of adsorption to free standing graphitic flakes, which are governed by a surface oxygen content. Specifically, higher oxygen content of a surface leads to decrease in persistence length of ssDNA. However, the role of DNA sequence on the physisorption mechanism is minimal.

The microfluidic production of droplets is a well controllable process, which allows templating small spherical containers that can subsequently be transferred into uniformly sized polymer microgel particles by a crosslinking reaction. Recently, the per-channel production rate of N-isopropylacrylamide (NIPAAm) droplets (w-phase) dispersed in a low-viscosity fluorocarbon oil (o-phase) could be increased by a delayed surfactant addition, while maintaining the advantageous dripping regime. Here it should be evaluated, if delayed surfactant addition can be applied to enhance droplet production also for high viscosity continuous phases, which is associated with a change to an inviscid drop scenario compared to the previously used setting of viscous drops. It could be illustrated that the concept of delayed surfactant addition holds true also for viscous continuous phases and allows ∼8 fold increased flow rates in the dripping regime. Surprisingly, the droplet size increased at higher total flow rate with constant flow rate ratios of w- and o-phases, which is discussed in the light of viscous dissipation, microchannel bulging and viscosity of the continuous phase. More rigid microchannels such as from glass may allow further exploring this phenomenon in the future.

Raman spectroscopy studies have been performed on one hand to identify different materials related to spent nuclear fuel (SNF), and on the other hand to study the behavior of SNF at different storage conditions. Specifically, the expected oxidation of the SNF matrix under dry storage conditions and the formation of secondary phases (SP), as a result of corrosion of SNF in a deep geological repository, have been studied. In order to perform these experiments, two protocols based on the Raman spectroscopy technique have been developed. The results show U4O9/U3O7 and U3O8 as oxidation products of UO2 powder at high temperatures in air, and the secondary phase formation (rutherfordine, UO2(CO3), soddyite, (UO2)2SiO4•2H2O, uranophane alpha Ca(UO2)2(SiO3OH)2•5H2O and kasolite, PbUO2SiO4•H2O), due to uraninite corrosion under the conditions of Sierra Albarrana (Spain).

In the field of tissue engineering, design and fabrication of precisely and spatially patterned, highly porous scaffolds/matrixes are required to guide overall shape of tissue growth and replacement. Although rapid prototyping fabrication techniques have been used to fabricate the scaffolds with desired design characteristics, controlling the interior architecture of the scaffolds has been a challenge due to Computer-aided Design (CAD) constrains. Moreover, thick engineered tissue scaffolds show inadequate success due to the limited diffusion of oxygen and nutrients to the interior part of the scaffolds. These limitations lead to improper tissue regeneration. In this work, in order to overcome these design and fabrication limitations, research has been expanded to generation of scaffolds which have inbuilt micro and nanoscale fluidic channels. Branching channels serve as material delivery paths to provide oxygen and nutrients for the cells. These channels are designed and controlled with Lindenmayer Systems (L-Systems) which is an influential way to create the complex branching networks by rewriting process. In this research, through the computational modeling process, to control the thickness, length, number and the position of the channels/branches, main attributes of L-Systems algorithms are characterized and effects of algorithm parameters are investigated. After the L-System based branching design is completed, 3D tissue scaffolds were fabricated by “UV-Maskless Photolithography”. In this fabrication technique, Polyethylene (glycol) Diacrylate (PEGDA), which is biodegradable and biocompatible polymer, was used as a fabrication material. Our results show that L-System parameters can be successfully controlled to design of 3D tissue engineered scaffolds. Our fabrication results also show that L-System based designed scaffolds with internal branch structures can be fabricated layer-by-layer fashion by Maskless Photolithography. This technology can be easily applied to engineering living systems.

This research describes thiol-ene/epoxy hybrid networks for core-shell encapsulation of semiconductor devices. A thiol-ene network was formed using ultraviolet-induced radical polymerization, with unreacted thiols and epoxide monomers remaining in the network. Immersion in tributylamine catalyzed the thiol-epoxy coupling to produce a diffusion-limited hard outer shell. Tensile testing shows that the initial thiol-ene product (core) has elastomeric behavior, while the secondary curing creates a glassy material (shell) at room temperature due to thiol-epoxy coupling. Bulk samples of the material form a hard outer shell surrounding a soft core depending on the secondary cure conditions. There are positive relationships between wall thickness and secondary cure temperature and cure time, enabling control of shell thickness by varying reaction conditions. Shell thicknesses were measured up to 1.8 mm when immersed in tributylamine for up to 150 minutes and up to 140 °C. The ability to control core-shell thickness of dual-cured networks is applicable in device encapsulation processes. Core-shell encapsulants for microelectronics may provide further shock and impact protection for durable electronic devices. Further aging and operational studies will be needed to determine time-stability and optimal processing of the core-shell structure.

The aluminum doped SrFe12O19 hexaferrite samples were prepared via co-precipitation method using cetyltrimethyl ammonium bromide (CTAB) as a surfactant. The effects of CTAB content (x = 0, 1, 3, 6 and 9 wt. %) on the structure, morphology, and electrocapacitive behavior of the SrFe10Al2O19 nanoparticles were investigated. The use of CTAB was observed to be effective in eliminating α-Fe2O3 phase from samples. Morphological changes including grain and crystallite size was noticed with the increase in the CTAB content. With the increase in CTAB, powder particles grew in size and thickness. A concomitant increase in magnetization due to crystal growth was observed. Electrochemical performance of supercapacitors was evaluated by cyclic voltammetry (CV). Highest power density of 368.09 WKg-1 and energy density of 0.916 WhKg-1 was observed for 3% and 1% CTAB samples, respectively.

Graphene quantum dots (GQDs), a nano version of graphene whose interesting properties that distinguish them from bulk graphene, have recently received significant scientific attention. The quantum confinement effect referring to the size-dependence of physical and chemical properties opens great possibility in the practical applications of this material. However, tuning the size of graphene quantum dots is still difficult to achieve. Here, an edge-etching mechanism which is able to tune the size of GQDs in a quasi-continuous manner is discovered. Different from the ‘unzipping’ mechanism which has been adopted to cut bulk graphitic materials into small fragments and normally cut through the basal plane along the ‘zig-zag’ direction where epoxy groups reside, the mechanism discovered in this research could gradually remove the peripheral carbon atoms of nano-scaled graphene (i.e. GQDs) due to the higher chemical reactivity of the edge carbon atoms than that of inner carbon atoms thereby tuning the size of GQDs in a quasi-continuous fashion. It enables the facile manipulate of the size and properties of GQDs through controlling merely the reaction duration. It is also believed the as discovered mechanism could be generalized for synthesizing various sizes of GQDs from other graphitic precursors (e.g. carbon fibres, carbon nanotubes, etc).

A nanoporous carbon (C) material, functionalized with Cobalt-Oxide/Cobalt (CoO/Co) core-shell nanoparticles (NPs), was structurally and chemically characterized with transmission electron microcopy (TEM) while its electrochemical response for Lithium ion battery (LIB) applications was evaluated as well. The results herein show that the nanoporous C material was uniformly functionalized with the CoO/Co core-shell NPs. Further the NPs were crystalline with fcc-type lattice on the Co2+ oxide shell and hcp-type core of metallic Co0. The electrochemical study was carried out by using galvanostatic charge/discharge cycling at a current density of 1000 mA g−1. The potential of this hybrid material for LIB applications was confirmed and it is attributed to the successful dispersion of the Co2+/ Co0 NPs in the C support.

Using molecular statics calculations, sodium silicate glasses are expanded in an isotropic manner to analyze the composition dependence of the mechanical response.

Increasing the amount of sodium makes the systems more ductile. The tensile strength is reduced and the final load bearing strain limit is increased.

Hydrostatic strain hardening appears in the ductile samples. To explain this phenomena, the density is coarse-grained to identify microscopic defects. In samples containing a significant amount of sodium, a large amount of nano-voids appear before reaching the maximum load bearing capacity. In high sodium content silicates these cracks may cause the hardening observed in the pressure results.

In samples with low sodium content, the failure is abrupt and only a large crack is observed. Increasing the amount of long term but weaker Na-O interactions, instead of the short range Si-O ones could explain the observed transition.

Using scanning tunneling microscopy (STM) we observed atomic scale interference patterns on quasi-freestanding WSe2 islands grown on top of graphene. The bias-independent double atomic size periodicity of these patterns and the sharp Brillouin zone edge revealed by 2D STM Fourier analysis indicate formation of optical phonon standing waves due to scattering on intercalating defects supporting these islands. Standing wave patterns of both synchronized and non-synchronized optical phonons, corresponding to resonant and non-resonant phonon scattering regimes, were experimentally observed. We also found the symmetry breaking effect for individual phonon wave packets, one of the unique features distinguishing phonon standing waves. We show that vibrational and electronic anharmonicities are responsible for STM detection of these patterns. A significant contribution to the interference contrast arises from quantum zero-point oscillations.

In order to enhance the photocatalytic efficiency of oxide semiconductors, variant processes have been proposed. The creation of the heterojunction composites has attracted considerable attentions and developed into an important research area for the high performance photocatalyst preparation. In this paper, we introduce the research progress on heterojunction composites which were prepared via a novel physical route with relatively high temperature treatments. It is hope that this mini-review can inspire research interest in the realm of heterojunction synthesis based on the thermal diffusion mechanism.