The CALPHAD (CALculation of PHAse Diagrams) method is widely recognized as a powerful tool in both scientific and industrial development of new materials and processes. For the implementation of consistent databases, where each phase is described separately, models are used which are based on physical principles and parameters assessed from experimental data. Such a database makes it possible to perform realistic calculations of thermodynamic properties of multi-component systems. However, a commercial available TiAl database can be applied for thermodynamic calculations to both conventional Ti-base alloys and complex intermetallic TiAl alloys to describe experimentally evaluated phase fractions as a function of temperature. In the present study calculations were done for a β-solidifying TiAl alloy with a nominal composition of Ti-43.5Al-4Nb-1Mo-0.1B (in at. %), termed TNMTM alloy. At room temperature this alloy consists of ordered γ-TiAl, α2-Ti3Al and β0-TiAl phases. At a certain temperature α2 and β0 disorder to α and β, respectively. Using the commercial database the thermodynamic calculations reflect only qualitative trends of phase fractions as a function of temperature. For more exact quantitative calculations the commercial available thermodynamic database had to be improved for TiAl alloys with high Nb (and Mo) contents, as recently reported for Nb-rich γ-TiAl alloys. Therefore, the database was modified by experimentally evaluated phase fractions obtained from quantitative microstructure analysis of light-optical and scanning electron micrographs as well as conventional X-ray diffraction after long-term heat treatments and by means of in-situ highenergy X-ray diffraction experiments. Based on the CALPHAD-conform thermodynamic assessment, the optimized database can now be used to correctly predict the phase equilibria of this multi-component alloying system, which is of interest for applications in automotive and aircraft engine industry.

Visible (λ > 420 nm) light-driven photooxidation of water at TiO2-polyheptazine (TiO2-PH) hybrid photoanodes loaded with two different metal oxide co-catalysts was investigated in a twoelectrode setup. As compared to TiO2-PH photoanodes loaded with colloidal IrO2, photoelectrodes modified with photodeposited CoOx oxygen-evolving co-catalyst (Co-Pi) showed both higher photocurrents and more efficient oxygen evolution. The minimum external electric bias needed to observe complete photooxidation of water to dioxygen at TiO2-PH photoanodes modified with Co-Pi was estimated to be ca. 0.6 V at pH 7.

In this paper we discuss the formation of InN on GaN heterostructures. Film growth was accomplished using a new method coined Migration Enhanced Epitaxial Afterglow (MEAglow), an improved form of pulsed delivery Plasma Enhanced Chemical Vapour Deposition (PECVD) [1]. Initial x-ray diffraction (XRD) analysis results indicated that an InGaN alloy layer formed under the InN during growth. No GaN was seen from the original buffer layer. It was postulated that indium metal deposited prior to complete nitridation diffused into the relatively thin GaN layer producing InGaN. To verify the integrity of the insulating GaN layer, a third party GaN substrate was substituted. Results were unchanged. Parameters were then modified to reduce the amount of indium used for the initial metal deposition. XRD results indicated a sharper interface between the semi-insulating GaN and conductive InN layer. Hall Effect measurements are included. We’ve shown that the growth of a device suitable heterostructure is possible using the MEAglow technique.

Here we report studies of photoelectrochemical (PEC) properties and ultrafast charge carrier relaxation dynamics of hydrogen-treated TiO2 (H:TiO2) nanowire arrays. PEC measurements showed the photocurrent density of the H:TiO2 was approximately double that of TiO2, attributed to increased donor density due to the formation of oxygen vacancies in H:TiO2 due to hydrogen treatment Charge carrier dynamics of H:TiO2, measured using fs transient absorption spectroscopy, showed a fast decay of ∼20 ps followed by slower decay persisting to tens of picoseconds. The fast decay is attributed to bandedge electron-hole recombination and the slower decay is attributed to recombination from trap states. Visible absorption is attributed to either electronic transitions from the valence band to oxygen vacancy states or from oxygen vacancy states to the conduction band of the TiO2, which is supported by incident photon to current conversion efficiency (IPCE) data. H:TiO2 represents a unique material with improved photoelectrochemical properties for applications including PEC water splitting, solar cells, and photocatalysis.

Pentacene and poly 3-hexylthiophene (P3HT) are the most promising p-type organic semiconducting materials for fabrication of organic field effect transistors (OFETs). OFETs with aforesaid organic semiconducting materials have been demonstrated as total dose detectors for ionizing radiation, wherein the changes in the electrical characteristic parameters, such as, increase in the OFF current, increase in the ON current, change in the current ratio, shift in the threshold voltage, change in the subthreshold swing, etc., were used as a measure of ionizing radiation dose. Upon exposure to ionizing radiation P3HT based OFET sensor has shown an OFF current sensitivity of 4.4 nA/Gy while pentacene based OFET sensor has shown an OFF current sensitivity of 26.7 nA/Gy for a total of 50 Gy dose of ionizing radiation. Change in the conductivity of the thin-films of pentacene and P3HT were observed and compared using electrostatic force microscopy (EFM) imaging before and after exposure to ionizing radiation. Effects of ionizing radiation on the energy band structures of the organic semiconducting materials, pentacene and P3HT, have been studied using UV-visible spectroscopy. Moreover, analysis of UV-visible spectra of the thin-films suggested the generation of energy states in larger quantity in case of pentacene thin-film as compared to P3HT thin-film upon exposure to the same dose of ionizing radiation. These results confirm the higher sensitivity observed in pentacene OFET sensor as compared to P3HT OFET sensor in terms of the change in electrical parameters.

We investigate the influence of the crystallinity of the absorber layer and parasitic absorption in the doped layers and electrodes on the external quantum efficiency and reflection of microcrystalline silicon (μc-Si:H) solar cells. Using an optical light scattering model we systematically study variations in the crystallinity and validate a simple normalization procedure that allows assessing the gains that can be achieved by reducing the parasitic absorption. The optimization potential is demonstrated with solar cell samples with increased crystallinity and eliminated parasitic absorption.

Aqueous corrosion of zirconium alloys has become the major factor limiting prolonged fuel campaigns in nuclear plant. Studies using SEM, TEM and electrochemical impedance measurements have been interpreted as showing a dense inner-most oxide layer, and an increased thickness of the layer has been correlated to a better corrosion resistance. Many authors have reported that an ‘intermediate layer’ at the metal oxide interface has a complex structure or/and stochiometry different to that of both the bulk oxide and bulk metal, sometimes claimed to be a suboxide phase. Diffraction evidence has suggested the presence of both cubic ZrO and rhombohedral Zr3O phases, and compositional analysis has revealed similar variations in local oxygen stoichiometry.

We have carried out a systematic investigation of the structure and chemistry of the metal/oxide interface in samples of commercial ZIRLO corroded for times up to 180 days. We have developed new experimental techniques for the study of these interfaces both by Electron Energy Loss Spectroscopy (EELS) analysis in the Transmission Electron Microscope (TEM) and by Atom Probe Tomography (APT), and exactly the same samples have been investigated by both techniques. Our results show the development of a clearly defined suboxide layer of stoichiometry close to ZrO, and the subsequent disappearance of this layer at the first of the characteristic ‘breakaway’ transitions in the oxidation kinetics. We can correlate this behaviour with changes in the structure of the oxide layer, and particularly the development of interconnected porosity that links the corroding interface with the aqueous environment. Using high resolution SIMS analysis of isotopically spiked samples we demonstrate the penetration of the oxidising species through these porous outer oxide layers.

We revisit the polymorphism of carbon along two directions. First, we discover novel polymorphs in the vicinity of graphite, with outstanding optical and mechanical properties. Using numerical methods and graph-theoretical tools, we find as many as 4 novel superhard and transparent polymorphs, with great technological potential. Second, scaling up a model of rod packing to carbon nanotube (CNT) scaffoldings, we discover that such complex assemblies of CNTs are outstanding adsorbers of hydrogen, capable of reaching the DOE target (~6.0 wt% at ambient conditions). Along this line, we highlight novel paradigms for revisiting carbon, in view of remarkable qualities and superior properties.

Co-implantation, with overlapping implantation projected ranges, of Si and of the doping species (P, As, or B), followed by a single thermal anneal step, is proved to be a viable route to form doped Si-nc’s embedded in SiO2, with diameters of a few nanometers. Extensive results of the evolution of the Si-nc’s related photoluminescence, as a function of the dopant implanted dose, are presented and discussed. Atomic Probe Tomography (APT) is used to image directly the spatial distribution of the various species at the atomic scale. The 3D APT data demonstrate that n-type dopant atoms (P and As) are efficiently introduced in the "bulk" of the Sinanocrystals, whereas B atoms are preferentially located at their periphery, at the Si/SiO2 interface.

Organic-inorganic hybrids have been prepared with tailorable and enhanced properties which are unachievable using polymers or ceramics alone. By combining the flexibility of polymers with the electronic and optical properties of ceramic materials, these hybrids offer great potential for many optical, electrical and mechanical applications. Silicone polymers because of their desirable surface properties, excellent physical properties, heat stability, and high resistance to chemical and UV attack, have been widely used. Hybrid siloxane-metal oxide gels have been prepared via sol-gel techniques, by using hydroxyl-terminated polydimethylsiloxanes (PDMS) crosslinked by metallic alkoxides, M(OR)n. In this technique, the use of organic solvents permits organic and inorganic components to be combined at a molecular level with the desired composition. By varying the type and percentage of metal alkoxides during synthesis, transparent and homogeneous organic-inorganic hybrid materials with unique properties were obtained. Also a secondary metal oxide species was introduced to synthesize binary metal oxide-PDMS hybrids. Systematic experiments were carried out to study the effect of the reaction conditions and metal alkoxides-PDMS ratios on the properties of the final hybrids. These hybrids were spin coating on silicon wafers or molded into bulk films to be tested. The composition and the properties of the transparent inorganic-organic hybrids were investigated and characterized by ellipsometer and Fourier Transform Infrared (FTIR) spectroscopy. Experimental results showed that the refractive index of the hybrid materials exhibits a proportional relationship with the metal oxide content, the higher the metal oxide content the higher the refractive index. The refractive index was increased from 1.4 of PDMS to 1.7 of metal oxide-PDMS hybrid with highest prepared metal oxide loading. From the FTIR spectra, the structures of the hybrids for various metal oxide-PDMS compositions were examined.

This paper reports the synthesis and characterization of the ZrO2:Co nanosystem, by incorporation of Co nanoparticles (CoNP) into tetragonal and monoclinic zirconia. ZrO2 was synthesized by a sol-gel process, while cobalt nanoparticles were obtained through a colloidal method by chemical reduction of a metal precursor. CoNP were incorporated by two different approaches: during the synthesis of the ZrO2 and by classical impregnation of CoNP on zirconium oxide. The size of Cobalt nanoparticles was controlled through the concentration of reducing agent (NaBH4) and passivanting agent (1-dodecanethiol). According to SEM and TEM analysis, the diameter of the zirconium oxide particles depends on the CoNP concentration added; the particle size for pure zirconia treated at 500°C is 200 nm and 180 nm for ZrO2:Co. X-Ray diffraction showed presence of the tetragonal and monoclinic zirconia, but the abundance of each one depends on the Co nanoparticles and thermally treatment.

We summarized in this paper the fabrication, properties, and electrochemical applications of diamond nanostructures, mainly diamond nanotextures and diamond nanowires. The characterizations of nanostructures were introduced with different techniques. As example of applications, electrochemical DNA sensing and protein trapping on diamond nanotextures are shown.

Phosphorus (P) doped ultra thin n+-layer is formed on crystalline silicon (c-Si) at low substrate temperatures of 80 – 350 °C using radicals generated by the catalytic reaction of phosphine (PH3) with a tungsten catalyzer heated at 1300 °C. The sheet carrier concentration obtained by Hall effect is in the range between 3×1012cm-2 and 8×1012cm-2. The distribution of P atoms obtained by secondary ion mass spectrometry (SIMS) indicates that P atoms locate within the depth of 4 nm from surface and the profile has almost the same distribution independent of any doping conditions such as substrate temperature or radical exposure time. The sheet carrier concentration is 1.15 – 2.12% of the amount of P atoms incorporated through the radical doping. The ratio of activated donors increases with substrate temperature during the radical doping, suggesting that P-related species bonded on the c-Si surface require thermal energy for their activation. Using the n+-layer formed by radical doping, the reduction of surface recombination velocity for n-type c-Si wafer is attempted. The effective minority carrier lifetime of the n-type c-Si sample covered with 6-nm-thick intrinsic amorphous Si (i-a-Si) layers on both side increases from 32 μs to1576 μs by the radical doping of P atoms to n-type c-Si surface, suggesting that the radical doping can be utilized for the formation of passivation layers on a-Si/ n-c-Si hetero-interface.

The challenge for all photovoltaic technologies is to maximize light absorption, convert photons with minimal losses to electrical charges and efficiently extract them towards the electrical circuit. For thin film silicon solar cells, a compromise must be found as light trapping is usually performed through textured interfaces, that are detrimental to the subsequent growth of dense and high quality silicon layers. We introduce here the concept of smoothening intermediate reflecting layers (IRL), enabling to combine high currents and good electrical quality in Micromorph devices in the superstrate configuration. After exposing the motivation for such structures, we validate the concept by showing a VOCenhancement when employing a polished silicon-oxide-based IRL. Shunting issues and additional reflection losses are pointed out with such technique, highlighting the need to develop alternative techniques for an efficient morphology adaptation before the microcrystalline silicon cell growth.

The effect of mechanical activation on the crystallization of glasses of the system SiO2-Fe2O3-BaO-Al2O3 is investigated. The ceramic-glasses are synthesized from silica and iron-rich Ferro-Titanium-Zirconiferous (FTZ) sands available in the state of Coahuila, Mexico. The parent glass is subjected to mechanical activation in a high-energy attrition mill during 4 or 8h. Then, both milled and non-milled glasses are subjected to a thermal crystallization treatment at temperatures of 900 or 1000ºC during 2 or 5h. It is found that, in the case of the thermal treatment carried out at 900°C/5h, an increment in the time employed for both the mechanical activation and the crystallization treatment enhanced the crystallization of the parent glasses and produced an increase in the compressive strength of the synthesized glass-ceramics.

We demonstrate that drop cast films of colloidal nanocrystals containing excess surfactants develop aggregation over several weeks after solvent evaporation. Fingered structures, typical of diffusion-limited aggregation, are created because of the residual mobility that nanocrystals retain in the film. We are able to control the aggregation through the concentration of surfactant molecules and the drying temperature of the films.

The use of semiconductor nanowires as new material building blocks for developing original devices is conditioned by the controllability of their growth. An important challenge is to form nanowires which include heterostructures of predictable dimensions. This objective requires a precise knowledge of the growth kinetics which appears much more complex for nanowires than for standard two-dimensional layers. Here, we present a method which provides detailed information on nanowire formation. The method is implemented with InP1-xAsx nanowires grown by Au-catalyzed molecular beam epitaxy. Controlled and periodic modulations of the incident vapor phase are generated. Due to these modulations, the nanowires show small and short oscillations of composition along their growth axis. These oscillations furnish a time scale which is recorded in the nanowire solid phase. The instantaneous growth rate and the total length of individual nanowires at any time of the growth are accessible. Moreover, the distribution of the oscillation lengths contains the nucleation statistics. This statistics is shown to be strongly sub-Poissonian, which indicates that some regulation mechanism operates. The rapid depletion of group V atoms in the catalyst drop which follows the growth of each ML could explain the self-regulation of nucleation events.

Light trapping due to rough transparent conductive oxide (TCO) surfaces is a common and industrially applied technique in thin film silicon solar cells. In this study, we demonstrate a novel light trapping solution using electrochemically deposited, highly doped zinc oxide (ZnO) nanorod arrays which goes beyond standard light management concepts. The n-doped ZnO rods enable the application as front electrode in superstrate configuration. We explain our experimental results by multidimensional solar cell simulations and show how the nanorod array geometry influences the cell performance. The requirement is demonstrated to choose an appropriate average nanorod distance which strongly influences the electrical cell characteristics. The results clearly outline the potential of TCO nanorod technology for enhanced light trapping.

Reactive magnesium oxide (magnesia, MgO) was produced by calcining magnesite at comparatively low temperature, less than 800 ℃C. The reactive MgO and fly ash were used as additives to cementitious binder. The reactive MgO-ordinary Portland cement-fly ash is referred to as MgO-OPC-FA cement in further. The hydration expansion effect of active magnesia on the properties of cementitious binder in different mixing ratio was investigated. It is known that the “dead burnt” MgO reacts with water very slowly, which causes the expansion after the solidification of cement. Therefore, the MgO content in ordinary cement is commonly restricted to less than 5%. Effects of reactive MgO on the expansion properties of the cementitious binders were studied. Hydrated products of reactive MgO cements were investigated by X-ray diffraction (XRD) and Scanning electron microscope (SEM) analysis. The MgO-OPC-FA cement was sound, although the content of reactive MgO in cement was about 8 wt. %. Reactive MgO was hydrated at early age in 24 hours, thus causing rapid expansion. Mg(OH)2appeared on initial stage of cement hydration for active magnesia. The hydration rate of active magnesia was not equal to that of the dead burnt magnesia. The hydration of reactive MgO has a negative effect on the mechanical properties of reactive MgO-ordinary Portland cement-fly ash system, in spite of the inhibitive effect of the expansion of MgO hydration produced by fly ash. Our results shed light on the potential utilization of reactive MgO in the manufacturing of cementitious binders.

Post semiconductor manufacturing processes (PSM), including packaging and printed circuit board (PCB) manufacturing are now capable of producing trace widths of a few micrometers, high aspect ratio vias, three-dimensional constructions, and highly integrated systems in a single small package. Such PSM technology can in principle be used to manufacture micro electromechanical systems (MEMS) for sensing and actuation applications. Although MEMS are traditionally produced using silicon processes, the broad array of manufacturing approaches available in the packaging industry, including lamination, lithography, etching, electroforming, machining, bonding, etc., and the large number of available materials such as polymers, ceramics, metals, etc., provides greater design freedom for producing functional microdevices. The results of such processes applied to fabricating small systems are heterogeneously integrated MEMS devices. Since lamination of stacked layers is a critical component of this process, we refer to these devices as “laminate MEMS.”

In many cases laminate MEMS devices are more suited to their applications than their silicon counterparts, especially for applications such as biomedical, optical, and human computer interface. Furthermore, such microdevices can be built with a high degree of integration, pre-packaged, and at low cost. Indeed, the PCB and packaging industries stand to benefit greatly by expanding their offerings beyond serving the semiconductor industry and developing their own devices and products. This paper illustrates that good quality MEMS devices can be manufactured using packaging style fabrication, particularly using stacks of laminates, and discusses some of the unique benefits of such devices. This laminate MEMS technology promises not only improved methods for manufacturing microdevices but also for heterogeneously integrating them with silicon microelectronics and other components into a single package.