Based on studies of simple oxides, this paper demonstrates that the specific energy deposition modes under irradiation induce modifications of materials over different length scales. On the other hand, we show the Landau phase transition theory, widely used to explain the structural stability of materials out of irradiation, can give a general framework to describe the behavior of these oxides under irradiation. The use of X-ray diffraction techniques coupled with the Raman spectroscopy allows defining in a quantitative way the phenomenological parameters leading to predictive results. This paper clearly shows that in two model systems, pure zirconia and spinels, no unexpected new phases are produced in these oxides irradiated at room temperature and with different fluxes. Such a phenomenological approach may be useful to study the radiation tolerance of many crystalline ceramics (e.g. the zirconium based americium ceramics).

We have investigated the local electron transport in polycrystalline silicon (pc-Si) thin-films by atomic force microscopy (AFM)-based measurements of the electron-beam-induced current (EBIC). EVA solar cells are produced at UNSW by <i>EVAporation</i> of a-Si and subsequent <i>solid-phase crystallization</i>–a potentially cost-effective approach to the production of pc-Si photovoltaics. A fundamental understanding of the electron transport in these pc-Si thin films is of prime importance to address the factors limiting the efficiency of EVA solar cells. EBIC measurements performed in combination with an AFM integrated inside an electron microscope can resolve the electron transport across individual grain boundaries. AFM-EBIC reveals that most grain boundaries present a high energy barrier to the transport of electrons for both p-type and n-type EVA thin-films. Furthermore, for p-type EVA pc-Si, in contrast with n-type, charged grain boundaries are seen. Recombination at grain boundaries seems to be the dominant factor limiting the efficiency of these pc-Si solar cells.

Current use of nanodiamond (ND) particles in electronic-related applications is mostly restricted to their role in seeding of substrates for growth of diamond films by chemical vapor deposition (CVD). While it is a niche application, nanometer-sized diamond particles are indispensable in this role. Seeding of substrates using a novel slurry of detonation nanodiamond particles in dimethylsulfoxide (DMSO) and methanol is one of the topics of this article. At the same time, optical applications of NDs, particularly development of photoluminescent NDs for biomedical applications is one of the most popular current research topics. In this paper perspectives for the use of detonation NDs and specifically the role of surface functionalization in imparting photoluminescent properties to detonation NDs as well as enhanced photoluminescence of proton irradiated ND-polydimethylsiloxane composites are discussed.

Recent progress in fabrication technology allows for the efficient control of electromagnetic waves by means of photonic devices. This could be attractive and promising also for high-temperature photonic structures to control electromagnetic heat transfer at temperatures above 1000 oC. We discuss the literature and present our own results on Fiber Matrix Composites (FMC), which could be superior to high-temperature metals or monolithic ceramics and can be designed for photonic applications. Possible applications include the protection of non-rotating components in high-temperature engines and turbines such as combustors and liners, coatings and parts for aerospace vehicles. Our discussion includes the material aspect and some relevant structure features. The use of woven fabrics to design new photonic band gap structures is discussed. An example of the use of the plane-wave expansion method for FMC design is given.

A kinetic study was performed on the growth of a reaction interlayer between molten Al and carbon steel substrates at temperatures between 665 to 820°C by holding Al/flux/steel assemblies, in a tube furnace, at temperature for times up to 120 min. An Ar atmosphere and a K-Al-F based flux were used to enable spreading of molten Al on the steel substrates. Chemical and microstructural characterization of the samples revealed that the interlayer is composed of FeAl3 and Fe2Al5, being the second phase significantly thicker. The Fe2Al5 phase grows toward the steel with a tongue like morphology. Isothermal growth profiles of the reaction interlayer followed a parabolic behavior, meaning that at the beginning the reaction is very rapid and once that a continuous interlayer is formed the growth of the interlayer is controlled by interdifussion of species across the interlayer.

A novel route to organic-inorganic composites was described based on biomineralization of poly(ethylene glycol) (PEG)-based hydrogels. The 3-dimensional hydrogels were synthesized by radical crosslinking polymerization of poly(ethylene glycol fumarate) (PEGF) in the presence of ethylene glycol methacrylate phosphate (EGMP) as an apatite-nuclating monomer, acrylamide (AAm) as a composition-modulating comonomer, and potassium persulfate (PPS) as a radical initiator. We used the urea-mediated solution precipitation technique for biomineralization of hydrogels. The apatite grown on the surface and interior of the hydrogel was similar to biological apatites in the composition and crystalline structure. Powder x-ray diffraction (XRD) showed that the calcium phosphate crystalline platelets on hydrogels are preferentially aligned along the crystallographic c-axis direction. Inductively-coupled plasma mass spectroscopy (ICP-MS) analysis showed that the Ca/P molar ratio of apatites grown on the hydrogel template was found to be 1.60, which is identical to that of natural bones. In vitro cell experiments showed that the cell adhesion/proliferation on the mineralized hydrogel was more pronounced than on the pure polymer hydrogel.

We use a Thermoreflectance Thermal Imaging technique to study the transient cooling of SiGe-based microrefrigerators. Thermal imaging with submicron spatial resolution, 0.1C temperature resolution and 100 nanosecond temporal resolution is achieved. Transient temperature profiles of SiGe-based superlattice microrefrigerator devices of different sizes are obtained. The dynamic behavior of these microrefrigerators, show an interplay between Peltier and Joule effects. On the top surface of the device, Peltier cooling appears first with a time constant of about 10-30 microseconds, then Joule heating in the device starts taking over with atime constant of about 100-150 microseconds. The experimental results agree very well with the theoretical predictions based on Thermal Quadrupoles Method. The difference in the two time constants can be explained considering the thermal resistance and capacitance of the thin film. In addition this shows that the Joule heating at the top metal/semiconductor interface does not dominate the microrefrigerator performance or else we would have obtained the same time constants for the Peltier and Joule effects. Experimental results show that under high current values, pulse-operation the microrefrigerator device can provide cooling for about 30 microseconds, even though steady state measurements show heating. Temperature distribution on the metal leads connected to the microrefrigerator’s cold junction show the interplay between Joule heating in the metal as well as heat conduction to the substrate. Modeling is used to study the effect of different physical and geometrical parameters of the device on its transient cooling. 3D geometry of heat and current flow in the device plays an important role. One of the goals is to maximize cooling over the shortest time scales.

Nano-crystalline films of pure cubic ZrO2 have been produced by ion beam assisted deposition (IBAD) processes which combine physical vapor deposition with the concurrent ion beam bombardment in a high vacuum environment and exhibit superior properties and strong adhesion to the substrate. Oxygen and argon gases are used as source materials to generate energetic ions to produce these coatings with differential nanoscale (7 to 70 nm grain size) characteristics that affect the wettability, roughness, mechanical and optical properties of the coating. The nanostructurally stabilized chemically pure cubic phase has been shown to possess hardness as high as 16 GPa and a bulk modulus of 235 GPa. We examine the mechanical properties and the phase stability in zirconia nanoparticles using first principle electronic structure method. The elastic constants of the bulk systems were calculated for monoclinic, tetragonal and cubic phases. We find that calculated bulk modulus of cubic phase (237GPa) agrees well with the measured values, while that of monoclinic (189GPa) or tetragonal (155GPa) are considerably lower. We observe considerable relaxation of lattice in the monoclinic phase near the surface. This effect combined with surface tension and possibly vacancies in nanostructures are sources of stability of cubic zirconia at nanoscale.

We have demonstrated a 5-inch flexible color liquid crystal display (LCD) and organic light emitting display (OLED) driven by low-voltage operation organic TFT. In order to achieve high-quality and high-resolution moving images, OTFTs with high performances such as a high mobility, high ON/OFF ratio, low sub-threshold slope (SS) and low operating voltage, are developed. We fabricated pentacene-based low-voltage operation OTFT with a Ta2O5 gate dielectric prepared at a low temperature process. The resulting OTFT array showed a high mobility of 0.3-0.4 cm2/Vs, ON/OFF ratio over 107, VTH=2.7V, and low SS=0.3 V/decade. OTFTs with solution-processable materials such as fluoropolymer gate dielectric and liquid-crystalline semiconducting polymers, PBTTT, were also investigated. Electrical characteristics and stabilities of these devices will be discussed. In the final section, we will demonstrate OTFT-driven flexible displays. Both of the flexible LC device and the OLED device were successfully integrated on the pentacene-based OTFT arrays. Printing and lamination techniques were introduced to assemble the flexible LC device. Phosphorescent polymer materials, which can be patterned by ink-jet printing, were used for emitting layer of OLED. Color moving images were successively shown on the resulting 5-inch displays using an active-matrix driving technique of the OTFT at a low driving voltage of 15V.

Microcrystalline silicon (μc-Si:H) thin-film transistors (TFTs) have lately gained much attention due to their high charge carrier mobilities. We report on top-gate μc-Si:H TFTs fabricated by plasma-enhanced chemical vapor deposition at process temperatures below 180 °C with high electron and hole charge carrier mobilities exceeding 50 cm2/Vs and 12 cm2/Vs, respectively. Based on the μc-Si:H TFTs different thin-film inverters were realized including ambipolar and complimentary metal-oxide-semiconductor (CMOS) inverters. Microcrystalline CMOS inverters exhibit high voltage gains exceeding 22, whereas ambipolar inverters show reduced voltage gains of 10 at low operating voltages. The electrical characteristics of the μc-Si:H CMOS and ambipolar thin-film inverters will be discussed in terms of the voltage transfer curve, the voltage gain and the power dissipation.

Scandium tungstate is investigated as a model material for solid electrolytes in which polyatomic anions, here WO4 2–, are mobile in the solid state. Simulations using structures with artificially induced WO4 2– vacancy, Frenkel defect and Schottky defects produced lower activation energy compared to the initially defect-free model. Simulations with Frenkel defect structures show low activation energy but the interstitial WO4 2– has initially a strong preference to return to the vacant tungstate site. The vacancy defect model reproduces the activation energy to the experimental conductivity studies more closely. Qualitative considerations support the idea that vacancies formed during the sample preparation are the most abundant mobile defect among the investigated cases. Nonstoichiometric samples with varying initial Sc2O3:WO3 ratios Sc2O3 - x WO3, where x = 2.9, 3.0 and 3.1, are synthesized and characterized by XRD and impedance measurements, but a significant influence on the conductivity could not be confirmed experimentally.

GABA and glutamate are known as the principal inhibitory and excitatory neurotransmitters in the vertebrate central nervous system, respectively. However, recent electro-physiological and immunogold data reported by Stell et al. [1] indicate that GABA may undergo also an excitatory action on presynaptic varicosities of parallel fibers (PFs) in the molecular layer of the rat cerebellum. PFs are axonal extensions, with a cross section of about 0.1 m, of the glutamatergic granule cells. Such an unexpected excitatory action of GABA indicates clearly the presence of GABA receptors in the PFs of granule cells. We show in this study that quantum dots may be used specifically and efficiently to label two endogenous synaptic proteins, namely R-GABAA-1 receptors (GABAA Rs) and glutamate transporters (VGLUT1) in order to target their localization in very small structures such as the presynaptic varicosities of the PFs, in agreement with the results recently reported by Stell et al..

The fabrication of NCs is carried out using an innovative method, ultra-low energy (≤5 keV) ion implantation (ULE-II) into thin (6-9 nm) HfO2–based layers in order to form after subsequent annealing a controlled 2D array of Si NCs. The implantation of Si into HfO2 leads to the formation of SiO2–rich regions at the projected range due to the oxidation of the implanted Si atoms. This anomalous oxidation that takes place at room temperature is mainly due to humidity penetration in damaged layers. Different solutions are investigated here in order to avoid this oxidation process and stabilize the Si-phase. Finally, unexpected structures as HfO2 NCs embedded with SiO2 matrix are obtained and show interesting memory characteristics. Interestingly, a large memory window of 1.18 V has been achieved at relatively low sweeping voltage of ± 6 V for these samples, indicating their utility for low operating voltage memory device.

The structure and vibrational spectrum of Gd2 and Gd2C2 endofullerenes are studied through Raman spectroscopy and universal force field (UFF) calculations. Hindered rotations, shown by both theory and experiment, indicate the formation of a Gd–cage bond, which reduces the ideal symmetry of the cage. We have conducted Raman studies of Gd2@C90, Gd2@C79N, and Gd2C2@C92. We have also studied Y2C2@C92 for comparison. Several modes have been identified which provide information about the endohedral complex.

It has been shown that Au and Ag nanoparticles present catalytic properties of pollutant gases, product of the hydrocarbons combustion processes, whose efficiency is strongly dependant on their size, morphology and supporting material. The activity of Ag subnanometric particles supported on alumina in the NOx reduction mechanism, for the reaction HC-SCR (Hydrocarbon Selective Catalytic Reaction) is a good example of these catalytic properties. It is also well established that both Au and Ag nanoparticles are oxygen poisoning resistant and that in certain reactions the bimetallic combination may be more efficient than their isolated parts. In this work we present a DFT calculation of the NOx (x =1, 2, 3) adsorption energies on the Au12Ag6 cluster surface. It is also discussed the possible synergetic effect of the different configurations, forming small Ag islands composed of one to five atoms, on the surface of the bimetallic cluster. The analysis was done using DFT in the ZORA approximation.

This paper presents a brief review of recent developments in the studies of fully hydrogenated graphene sheets, also known as “graphane,” and related initial results on partially hydrogenated structures. For the fully hydrogenated case, some important discrepancies exist between published first-principles calculations, and between calculations and experiment, with qualitative differences on whether or not the graphene sheet expands or contracts upon hydrogenation. The lattice change has important effects on partially hydrogenated structures. First-principles calculations of ribbon structures, with interfaces between graphane and graphene regions, show that the interfaces have substantial misfit strains. Calculating the interfacial energy must carefully account for the strain energy in the neighboring regions, and for sufficiently large regions between interfaces, defects at the interface that relieve the strain may be energetically preferable. Tight-binding simulations show that at ambient temperatures, segments of graphene sheets may spontaneously combine with atomic hydrogen to form regions of graphane. Small amounts of chemisorbed hydrogen distort the graphene layer, due to the lattice misfit.

Over the past few decades, metallic nanoparticles (NPs) have been of great interest due to their unique properties which distinguish them from those of bulk metals. Many attempts have been conducted to investigate the characteristics of NPs and their applications. However, the sintering process which converts metallic NPs to conductive film was not established yet. In this study, the microstructure evolution of Au NPs after sintering under different thermal condition was examined and the film quality was studied based on densification, organic residues and electrical resistivity. Au NP ink dispersed in a toluene were spin coated on Ni-plated FCCL or Si substrates and thermally treated in a furnace under different sintering profiles under various types of flows such as air, nitrogen (N2), or reducing atmosphere of formic acid (FA). The Au ink was consisted of Au NPs coated with an organic capping molecule. The capping molecules not only help NPs to disperse but prevent aggregation and precipitation of NPs out of solution. When the NPs are treated by thermal process, the surface ligands from capping molecule start to decompose and necking and melting of NPs occur producing the film with the electrical conductivity. The diameter of Au NPs was approximately between 5-7 nm with spherical shape. The Au film sintered under air showed only necking between neighboring Au NPs without further grain growth. When Au NPs films were sintered under N2 atmosphere, NPs fused together in clusters. Under sintering with flows of FA, a larger area of pores due to the volume shrinkage of the film was observed since an agglomeration and melting of NPs were considerably progressed compared to the film sintered under N2. Sintering with a flow of a single gas such as air or N2 showed organic residues in the film indicated by C-H or C-O stretch peaks. However, when mixed flows of FA and N2 were applied, there was no IR peaks from organic substances observed in the film. It is assumed that the organic capping molecules surrounding the Au NPs were removed significantly with sintering with two flows of FA and N2. The microstructure showed less pore distribution and lower level of organic residues compared to those sintered under air, N2, or FA atmospheres. The electrical resistivity was about twice of bulk value of 2.44 μΩ -cm. Overall Au NPs film sintered under FA and N2 resulted in a better sintering effect based on densification of the film and level of residual organics, translating into a relatively high electrical conductivity.

Highly sinterable La10Si6O27 and La10Si5.5M0.5O27 (M = Mg, and Al) nanopowders with apatite-type structure have been synthesized via a homogeneous precipitation method using diethylamine (DEA) as a precipitant. The synthetic approach using an organic precipitant with dispersant characteristics is advantageous in configuring weakly agglomerated nanopowders, leading to desirable sintering activity. X-ray diffraction powder patterns confirmed the single-phase crystalline lanthanum silicate of hexagonal apatite structure at 800 °C, which is a relatively lower calcination temperature compared to conventionally prepared samples. Transmission electron microscopy images revealed particles ∼30 nm in size with a high degree of crystallinity. A dense grain morphology was recognized from the scanning electron microscopy images of the polished surface of the pellets that were sintered at 1400 and 1500 °C for 10 h. This low-temperature sintering is significant because conventional powder processing requires a temperature above 1700 °C to obtain the same dense electrolyte. The doped-lanthanum silicate electrolyte prepared by the DEA process and sintered at 1500 °C for 10 h exhibited electrical conductivity comparable with samples prepared at much higher sintering temperature (>1700 °C).

We report on the development of tungsten-oxide-based photoelectrochemical (PEC) water-splitting electrodes using surface modification techniques. The effect of molybdenum incorporation into the WO3 bulk or the surface region of the film is discussed. Our data indicate that Mo incorporation in the entire film (WO3:Mo) results in poor PEC performances, most likely due to defects that trap photo-generated charge carriers. However, compared to a pure WO3 (WO3:Mo)-based PEC electrode, a 20% (100%) increase of the photocurrent density at 1.6 V vs. SCE is observed if the Mo incorporation is limited to the near-surface region of the WO3 film. The resulting WO3:Mo/WO3 bilayer structure is formed by epitaxial growth of the WO3:Mo top layer on the WO3 bottom layer, which allows an optimization of the electronic structure induced by Mo incorporation while maintaining good crystallographic properties.

The suckers that line the arms and tentacles of squid are equipped with rigid toothed ring-like elements that increase the gripping power during prey capture and handling. The sucker rings of the Humboldt squid Dosidicus gigas, are fully proteinaceous and contain nanotubules with diameters ranging from 100 to 250 nm. It has been shown previously that the ensuing porosity is a prime determinant of the local elastic modulus [A. Miserez et al., Adv. Mater. <b>21</b>, 401 (2009)]. Here additional nanoindentation data are presented together with structural analyses. The nanomechanical data support our model that the measured modulus is determined by the local porosity. The dry moduli reach ca. 8 GPa and are reduced about two-fold in the hydrated state. This surprisingly small reduction is discussed in relation to possible chemistries responsible for assembly of these structures.