Dilute magnetic semiconductors are ferromagnetic semiconductors recently discovered in nitride and oxide semiconductors by incorporating a small percentage of magnetic atoms into the semiconductors host. Recently it is reported that the structural and electrical properties of pure indium oxide can be modified by growth parameters. In this paper we investigate magneto-transport properties of Co-doped In2O3 dilute magnetic semiconductors thin films grown on sapphire and quartz substrates using pulsed laser deposition technique. The effect of partial oxygen pressure on structural, electrical, optical, and magneto-transport properties was discussed in details. The crystallinity of the films largely depends on growth temperature. Magneto-transport properties such as temperature dependent resistivity and magneto-resistance were found to be very sensitive to the micro-structural properties such as crystalinity as well as oxygen defect. The electrical carrier density of the films depends on oxygen pressure and a change of two orders of magnitude is observed. Depending on growth parameters, both positive and negative magneto-resistance is observed. Optical band-gap seems to vary with the growth partial oxygen pressure.

Etching of hydrogen-terminated Si(100) in deoxygenated water produces surfaces with a regular nanoscale topography. Surface infrared spectroscopy provides detailed information about this topography via interrogation of the silicon hydride species that populate this highly ordered surface. Here we investigate the feasibility of using siloxane chemistry to functionalize this surface while preserving the initial topography. The critical step in silanization to form high-quality organic layers is oxidative cleaning of the surface. By re-etching oxidized surfaces in hydrofluoric acid, we can repopulate surface hydride species and examine any apparent changes in topography that resulted from the oxidation step. We compare three different oxidation protocols and find that an SC-2 clean results in the least perturbation of the original topography. Preliminary results using both dynamic contact angle and atomic force microscopy suggest that the SC-2 oxidized surface can be functionalized with alkylsilane reagents to create a functionalized surface with regular, nanoscale topography, with all surface processing carried out under ambient conditions at or near room temperature.

High yielding and high strength Cu-Cu thermo-compression bonds have been obtained at temperatures as low as 175°C. Plated Cu bumps are used for bonding, without any surface planarization step or plasma treatment, and bonding is performed at atmospheric condition. In this work the 25μm diameter bumps are used at a bump pitch of 100μm and 40μm. Low temperature bonding is achieved by using immersion bonding in citric acid. Citric acid provides in-situ cleaning of the Cu surface during the bonding process. The daisy chain electrical bonding yield ranges from 84%-100% depending on the bonding temperature and pressure.

Efficient, high-frequency quantum light sources are a prerequisite for advanced quantum information processing. Here, we report the observation of a Purcell enhancement in the radiative decay rate of a single quantum dot, embedded in a microcavity light-emitting diode structure. An annulus of low-refractive-index aluminium oxide, formed by wet oxidation, is used to simultaneously achieve lateral confinement of both the optical mode and the current through the device. This technique reduces the active area of the device without impeding the electrical properties of the p-i-n diode. We measure a photon collection efficiency of 14 ± 1% and demonstrate single photon electroluminescence at repetition rates up to 0.5 GHz.

We fabricated highly transparent and high haze ZnO:Al film for front TCO of amorphous and microcrystalline silicon solar cells. We have sputtered ZnO:Al film of 1.3 μm on the thin seed layer of about 60nm which was previously sputtered on the glass substrate by using 4% dilution of oxygen to argon gas. The ZnO:Al film grown on the seed layer had much higher crystalline phase than one without any seed layer. Our bi-layer ZnO:Al film showed low resistivity of 2.66×10-4 Ω•cm and sheet resistance of 2.08 Ω/⇐ while conventional ZnO:Al film showed resistivity of 3.24×10-4 Ω•cm and sheet resistance of 2.46 Ω/⇐. After surface texturing by 0.5% HCl wet-chemical etching, the transmittance of ZnO:Al film was increased from 83.7% to 88.1% at wavelength of 550nm through the seed layer. Also the transmittance at 800nm was increased from 82.3% to 88.9%. Especially, haze values of the ZnO:Al film were drastically increased from 58.7% to 90.6% at wavelength of 550nm by employing the seed layer. Also haze values at 800nm were increased from 22.1% to 68.1%. It is expected that the seed layer method to improve the quality of ZnO:Al film will contribute to an increase of solar cell efficiency due to the high capability of light trapping and low electrical resistivity.

We have studied the Pulsed-Laser Melting (PLM) effects on Ti implanted GaP to form an Intermediate Band (IB). Structural analysis has been carried out by means of Time of Flight Secondary Ion Mass Spectroscopy (ToF-SIMS), Raman spectroscopy and Glancing Incidence X-Ray Diffraction (GIXRD). After the PLM annealing, Ti concentration is over the Mott limit. Nevertheless, the Raman spectra show a forbidden TO vibrational mode of GaP. This result suggests the formation of crystalline domains with a different orientation in the annealed region regarding to the GaP unannealed substrate. This conclusion has been corroborated by GIXRD measurements. As a result of the polycrystalline lattice, a drop of the mobility is produced.

A three dimensional thermal-fluid and stress model of a single chip SiC power sub-module was generated using ANSYS in order to determine the maximum temperature and deformation under various conditions. The effects of heat flux, working fluid temperature and differential pressure on temperature and thermal stress contours were of particular concern. Steady state analysis with water as the working fluid, a simulated heat flux of 11.12×104 W/m2, an interface coupling film coefficient of either 30 or 200 W/m2-K between the cooling plate and fluid, and ambient film coefficients from 6 W/m2-K to 300 W/m2-K, predicts maximum device junction temperatures between 374 and 316 K, and corresponding deformations from .0351% to .0293%. Under the same boundary and loading conditions, but with air as the working fluid, the deformations reached .0405% to .0296%, with temperatures between 427 and 316 K. Transient analysis also showed junction temperatures in the predicted range and determined the time to reach steady state to be between 150 and 2500 seconds depending on the boundary conditions. Experiments were conducted in order to validate ANSYS results.

In this work a novel package for the calculation of the diffracted intensity from nano-structures based on finite element simulations is presented. Besides a short introduction into the algorithm which we have developed two examples namely the diffraction from Si/SiGe systems with ripples and quantum dots with dislocations are shown.

Short-bandgap group II-VI compound cadmium telluride is widely used for the infrared optics, radiation detectors, and solar cells where p-type CdTe is needed. p-type conductivity of CdTe is mainly caused by the chlorine-based A-centers, and in part, by the less stable copper-oxygen complexes. As a rule, CdTe films are recrystallized by the help of a cadmium chloride flux that saturates CdTe with chlorine. In chlorine-saturated CdTe A-centers are converted to isoelectronic complexes that cause resistivity increasement of CdTe up to 9 orders of magnitude. Excess copper and oxygen or group I elements as sodium also deteriorate the p-type conductivity of CdTe like excess chlorine. p-type conductivity of CdTe can be restored e.g. by the vacuum annealing which removes excess chlorine from the film. Unfortunately, treatment that betters p-type conductivity of the CdTe film degrades the junction of the superstrate configuration cells. In this work we investigate possibilities to prepare p-type CdTe films on the molybdenum coated glass substrates. Samples were prepared by the vacuum evaporation and dynamic recrystallization of 6N purity CdTe on the top of Mo-coated glass substrates. Then samples were recrystallized with cadmium chloride flux under tellurium vapour pressure. Results of the test studies on the structure and electronic parameters of samples are presented and discussed.

Shape-memory polymers are of high scientific and technological interest in the biomedical field, e.g., as matrix for self-anchoring implantable devices. In this study, two different star-shaped copolyester tetroles, semi-crystalline oligo[(-caprolactone)-co-glycolide]tetrol (oCG) and amorphous oligo[(rac-lactide)-co-glycolide]tetrol (oLG), were synthesized and subsequently crosslinked by a low molecular weight diisocyanate resulting in copolyester urethane networks (N-CG, N-LG). Both networks could be loaded with model drugs and a diffusion controlled release of the drugs was observed without any effect on the mass loss as measure of hydrolytic degradation. However, the N-CG network’s capability of shape programming was disturbed as the crystallinity of the precursors got lost in the complex three dimensional architecture after crosslinking. By contrast, amorphous N-LG network showed an excellent shape-memory capability with a switching temperature around 36 °C corresponding to their glass transition temperature. This led to triple-functional materials combining biodegradability, shape-memory, and controlled drug release.

Two molecular modes of amphiphilic block copolymer-carbon nanotube interactions have been suggested in the literature, involving the adsorption of either individual block copolymer molecules or of multimolecular, spherical block copolymer micelles on the carbon nanotube. In both cases, the nature of stability imparted to the dispersion of nanotubes is kinetic, controlled by the steric barrier imposed by the adsorbed individual molecules or micelles. In this study we propose an alternate mode of molecular interaction, wherein the block copolymer molecules self-assemble around the nanotube to generate a thermodynamically stable aqueous dispersion. The possibility of such micellar solubilization of nanotubes is examined by constructing a phenomenological theory of nanotube solubilization. Illustrative calculations performed for polyethylene oxide- polypropylene oxide – polyethylene oxide (PEO-PPO-PEO) triblock copolymers show that they are capable of solubilizing carbon nanotubes in aqueous solutions. While the block copolymer molecules that spontaneously form cylindrical micelles are most likely to solubilize the nanotubes, other copolymers whose natural curvature is spherical or lamellar also are capable of forming cylindrical micelles around the nanotubes. Most interestingly, the solubilization is found to be size specific suggesting that this can be developed into a practical method to fractionate carbon nanotubes by size or chirality.

Spectral control is an enabling technology for greater than 10% efficient thermophotovoltaic (TPV) energy conversion [1-3]. Without control of the spectral distribution of photons reaching a TPV cell, the efficiency of a TPV energy conversion system suffers dramatically. Spectral control is the selection, design, and development of materials and structures used in TPV energy conversion systems to maximize the net flux of convertible (above band gap) photons, minimize the net flux of unconvertible (below band gap) photons, and recuperate (or reflect) any net flux of unconvertible (below band gap) photons that reach the TPV cell back to the radiating surface. Front surface, tandem filters consisting of an edge pass filter (short pass) in series with a highly doped, epitaxially grown layer have achieved the highest energy weighted spectral efficiency to date.

The performance, however, of these tandem filters is limited by at least two fundamental physical phenomena: the variation in performance with the incident angle of the photons and absorption in the filter materials. Three dimensional (3D), photonic crystal structures offer a potential solution to these fundamental limitations of tandem filters as well as the potential of spectral control for the radiating surfaces of TPV energy conversion system. First, 3D photonic crystal structures, in theory, perform equally for all incident angles. Second, the fabrication techniques for 3D photonic crystal structures may allow the use of materials (such as crystalline Si) with less absorption in the spectral range of interest (1-15μm) than the materials currently used in tandem filters. The fabrication techniques for 3D photonic crystal structures may also allow the use of high temperature (1000°C) materials for use as radiating surface spectral control. If so, 3D photonic crystal structures may be used to mitigate several of the inefficiencies associated with TPV systems.

The conclusion of this assessment is that 3D, photonic crystal structures can, in theory, provide near perfect TPV spectral control. If so, these structures may allow a 20% improvement over the performance achieved by tandem filters. Realizing this potential for TPV spectral control, however, will likely require significant development. At least two major challenges exist:

• Design techniques will likely need to be developed that will allow the analysis and design of 3D photonic crystal structures.

• Fabrication techniques will need to be developed for these structures that provide sufficient fidelity to a design to achieve the required performance and can be scaled to provide the area required for a given TPV application.

Molecular Dynamics (MD) simulations of nanoindentation on graphene membranes were performed. The 2-d Young's modulus of the graphene monolayer was determined as 243 ± 18 N/m and the breaking strength as 41 ± 3 N/m. These values agree reasonably well with recent experimental results [1]. In addition, the simulations allowed us to examine the atomic-scale dynamics of membrane breaking during the nanoindentation, involving formation of an increasing number of lattice defects until membrane is completely broken. The onset of defect appearance allowed us to determine the true elastic limit of graphene and the corresponding yield strength 29 ± 1 N/m which was not accessible experimentally. The defects consist of vacancies and Stone-Wales type defects. Long stable linear chains of sp bonded carbon atoms (carbynes) were observed under the indenter at the advanced stages of indentation. The dynamics of fracture propagation is governed by the shear stresses developed in the sample.

Gas jets play a key role in several steelmaking processes as in the Basic Oxygen Furnace (BOF) or in the Electric Arc Furnace (EAF). They improve heat, mass and momentum transfer in the liquid bath, improve mixing of chemical species and govern the formation of foaming slag in EAF. In this work experimental measurements are performed to determine the dimensions of the cavity formed at the liquid free surface when a gas jet impinges on it as well as liquid velocity vector maps measured in the zone affected by the gas jet. Cavities are measured using a high speed camera while the vector maps are determined using a Particle Image Velocimetry (PIV) technique. Both velocities and cavities are determined as a function of the main process variables: gas flow rate, distance from the nozzle to the free surface and lance angle. Cavity dimensions (depth and diameter) are statistically treated as a function of the process variables and also as a function of the adequate dimensionless numbers that govern these phenomena. It is found that Froude number and Weber number control the depression geometry.

We have investigated the change of the Schottky contact surface and the interface between Schottky metals and AlGaN/GaN heterostructure after the annealing process for 35 min at 300 °C. The secondary ion mass spectroscopy (SIMS) and the scanning electron microscopy (SEM) show that the Schottky metals and AlGaN/GaN heterostructure interacted actively during the annealing process. The atoms in Schottky contact and AlGaN/GaN heterostructure diffused interactively and the surface roughness of Schottky contact was increased. After the annealing process for fabricated AlGaN/GaN High-Electron-Mobility Transistor (HEMT), the threshold voltage was shifted by +0.2 V and the leakage current was decreased by 40 %.

The V2O5-MoO3 mixtures offer a whole range of materials where properties can be adjusted by simple modification of experimental parameters, which may be utilized for manufacturing metamaterials with on-demand properties. The V2O5-MoO3 system contains an intermediate phase V9Mo6O40, with a small fraction of V4+ instead of V5+. Consequently, this system should rather be considered as pseudobinary. The V4+ content depends on the oxygen partial pressure in the atmosphere. Thus, by changing the oxygen partial pressure one can tailor the electric properties of the system, and by changing the supercooling, the morphologic structure of crystallized bodies as well. For better understanding of this system differential thermal analysis and thermodynamic modeling was performed. Fibers of eutectic composition between V9Mo6O40 and MoO3 were grown by the micro-pulling-down technique. X-ray diffraction confirmed the existence of the V9Mo6O40 intermediate phase.

Due to their large conduction-band offsets, GaN/Al(Ga)N quantum wells are currently the subject of extensive research efforts aimed at extending the spectral range of intersubband optoelectronic devices towards shorter and shorter wavelengths. Here we report our recent measurement of optically pumped intersubband light emission from GaN/AlN quantum wells at the record short wavelength of about 2 μm. Nanosecond-scale optical pulses are used to resonantly pump electrons from the ground states to the second excited subbands, followed by radiative relaxation into the first excited subbands. The intersubband origin of the measured photoluminescence is confirmed via an extensive study of its polarization properties and pump wavelength dependence.

Exergy is the useful portion of energy that allows us to do work and perform energy services. While energy is conserved, exergy is not; some exergy is destroyed whenever energy undergoes a conversion. We gather exergy from distinct, energy-carrying resources that are found in the natural world. These resources are converted into energy carriers that are convenient to use in our factories, vehicles, and buildings for heating, lighting and mechanical services. While there is no shortage of exergy resources, there are considerable environmental, economic, and other constraints associated with the manner and magnitude of their use. This article describes an approach to examining and presenting data on energy use at a global scale. It provides insights into the efficiencies and carbon emissions of many energy pathways, and can provide a basis for an examination of future energy options. In this study, we trace the flow of exergy and carbon through the natural and human systems, revealing the major destructions of exergy, the exergy efficiency of engineered energy processes, and the processes with the highest associated atmospheric carbon emissions. These data have been collected in a relational database available online at http://gcep.stanford.edu/research/exergy/data.html and are presented here in a set of exergy and carbon flow charts.

ZnO has shown great promise for the application in optoelectronic devices. Since the modulation of conductivity is one of the key issues in device performances, we have applied the Monte Carlo method to analyze the mobility of poly-crystalline MgZnO/ZnO heterostructure thin film layer in this paper. The effects of the grain boundary scattering, ionized impurity scattering, as well as phonon scattering are considered. Our study shows that with a design of modulation doping by including the effects of spontaneous and piezoelectric polarization, the grain boundary potential can be suppressed to improve the mobility of the ZnO layer by order(s) of magnitude. Simulation results are also confirmed by our experimental works that polarization effects play an important role to attract carriers and to increase the mobility.

In Belgium, Eurobitum intermediate-level long-lived bituminized radioactive waste containing large amounts of NaNO3, which is a hygroscopic and soluble salt, is to be disposed of in an underground repository in a geologically stable clay formation. The Boom Clay is studied as a potential host formation because of its favourable properties to limit and delay the migration of the leached radionuclides and other contaminants (heavy metals, NaNO3, organic molecules) to the biosphere. The emplacement of the bituminized waste will induce multiple processes that could have a significant effect on the key properties of the clay. Because several of these processes are interdependent, the study of the compatibility of Eurobitum with geological disposal is complex. To structure the research and to identify possible knowledge gaps, the Belgian Radioactive Waste Management Agency ONDRAF/NIRAS developed a new methodology based on safety functions and safety statements. In this paper, this methodology is briefly explained, with reference to the disposal of Eurobitum. Experimental results obtained at the Belgian Nuclear Research Centre SCK•CEN are presented and discussed in the light of the safety functions and safety statements approach. The importance of the interdependence of the processes is highlighted. Special attention is given to the evolution of the disposal design as a result of the improved understanding of key processes.