We present a comprehensive study of using diblock copolymer micelle templates to synthesize ordered nanoparticle arrays. Ionic and coordination bonds have been exploited to incorporate nanoparticle precursors into cores of block copolymer micelles. Polystyrene-b-poly (4-vinylpyridine) (PS-b-P4VP) has been shown to be able to localize anions via electrostatic attraction with protonated pyridine cations while transitional metals can be sequestered through coordination bonds. Polystyrene-b-poly (acrylic acid) (PS-PAA) can localize a variety of cations via ionic bonds with acrylic anions. We have demonstrated that the size of nanoparticles can be tuned by controlling the solution concentration of an ionic precursor. By mixing these two distinct block copolymers which can selectively interact with different precursor species, complex nanoparticle architectures can be generated thus paving a path for new applications.

This paper investigated an inexpensive way to improve the overall photocatalytic activity of TiO2 by N- doping using anhydrous ammonia as the nitrogen source. Doping amount could be further optimized by controlling the reaction time. Experiments showed that photocatalytic effect has one threshold concentration. Lower or higher reaction will decrease the photocatalytic efficiency. Experiments showed that the suitable reaction temperature should be lower than 650oC.

The relation between impurity content in Solar Grade Silicon (SGS) and solar cell quality is the subject of intensive research. The PV industry has developed around the use of silicon made by the Siemens process for the semiconductor industry, with impurity levels typically in the parts per billion by weight (ppbw) range. There is a growing consensus that SGS with impurities in the parts per million range (ppmw) can be obtained cost effectively from Metallurgical Grade Silicon (MGS) and used to yield solar cells with comparable performance (see for example ‘Beneficial Effects of Dopant Compensation on Carrier Lifetime in Upgraded Metallurgical Silicon’ by S. Dubois et al. in the 23rd European Photovoltaic Solar Energy Conference, Valencia, September, 2008). This provides insight on the success encountered by Timminco, an early SGS market entrant, in commercializing silicon material with [P] levels of the order of 2 ppmw.Current WorkWe have successfully reduced P to about 2 ppmw, a level that appears acceptable for solar cell fabrication, by application of a novel unidirectional solidification (UDS) technique at a 50% material yield. This is important as UDS, by its nature, implies a loss of silicon, while little or no silicon is lost in B reduction, partially achieved in this furnace using a glass slagging process. Figure 1 shows [P] data from 16 UDS runs on samples taken from the melt, before and after UDS, and a solid sample taken from the silicon frozen on the cold silicon collection surface. The error bars represent a standard 20% error value. We note that the average values of [P] in the molten silicon samples increase from 11.9 ppmw before UDS to 15.9 ppmw after UDS. The average value of [P] in the solid silicon sample is 4.9 ppmw.The average value of the solid silicon, 4.9 ppmw P, taken with the average value of the starting silicon, 11.9 ppmw P, demonstrates an effective refining ratio of 0.41, even at a 50% solid fraction. Performing a second UDS on silicon obtained from runs in Figure 1, yields [P] around 2 ppmw (Figure 2).In addition to P and B reduction, in this paper we also discuss the hardware designed to implement this process in commercial production in volumes exceeding 4,000 MT per year. MB Scientific, the original process developer, and NC Consulting, an engineering company, have developed a plant design that can produce SGS at an estimated cost that will allow for profitable large scale production, and have joined in a new company, Silicon Forge, to commercialize the large-scale production technology.

Atmospheric Pressure Chemical Vapor Deposition (APCVD) thin film coating process is one of the most cost efficient large area thin film coating solutions presently available on the market and can be up to 2.5 times lower in cost compared with a low pressure sputtering system. Advanced materials such as transparent conductive oxides (TCO) used for solar panel manufacturing and for energy saving (Low-E) windows already have been deposited with APCVD Tools incorporating one or more deposition modules. Thin films such as SiO2, TiO2 and F: SnO2, etc have been successfully deposited onto glass sheets. However further improvement in material efficiencies and operational cost reductions are needed to satisfy the growing demand for such highly customized materials. It is also desirable in the future to be able to deposit other material films which traditionally have not yet been available on this lower cost APCVD manufacturing platform, such as zinc oxide (ZnO).

To investigate in a quantitative manner the improvement potential for the traditional APCVD deposition module design solution we performed a multidimensional computational fluid dynamics (CFD) parametric study using ANSYS FLUENT V12. As a baseline deposition module design we used a commercially available APCVD deposition module originally developed by Watkins-Johnson for SiO2 deposition trench fill of Si wafers from TEOS, O2 and Ozone from which we could locate in previously published papers for both experiment and CFD modeling results. The CFD software enabled us to perform a full parametric APCVD deposition module design study and allowed us to quantify the efficiency and throughput gains/losses of a wide variety of design change options. The main driver for this study was to learn in a quantitative, cost efficient and time efficient manner about what system design modifications have the potential for significant precursor efficiency increase and/or deposition throughput gain for a particular APCVD deposition process. The results of this study will be utilized to accelerate our proprietary, next generation Off-line and On-line CVDgCoat™ APCVD platform development.

The morphological and microstructural evolution associated with an exsolution driven self-nanostructurationprocess of La0.7Sr0.3MnO3 films, is investigated using scanning force microscopy, reciprocal space mapping and transmission electron microscopy. The focus is placed on the misfit strain relaxation mechanism. Surfaces with atomically flat terraces are already developed after 1hour at 1000 °C while first fingerprints of phase exsolution do not appear until 9-10 hours. X-ray diffraction reciprocal-space mapping reveals that 24 nm thick films remain strained during the whole microstructural evolution, while 12 hour annealed films undergo almost total plastic relaxation of the misfit strain at a thickness of 60 nm. Overall, these results point to a kinetic limitation of dislocation mechanisms. It is argued that chemical relaxation provides a significant contribution to misfit strain relief.

Growth of polycrystalline Lutetium Iron Oxide via pulsed laser deposition in thin film form is reported for the first time herein, and the multiferroic LuFe2O4 phase is stabilized. Fluence and pressure dependent phase growth is demonstrated, along with crystalline structure in vacuum (˜10-5 torr) conditions. Thermodynamic considerations at the laser-target interaction were investigated, as well as at the plume-substrate interface, which reveal that the necessary Gibbs free energy is available in the optimized growth environment to allow formation of the LuFe2O4 polycrystalline phase. The resulting growth rate is found to be related to the Gibbs free energy and concentration of nucleation sites on the substrate. Characterization of the multiferroic aspect of LuFe2O4 entailed direct measurement of the ferroelectricity in the thin film, as well as magnetic behavior, both at various temperatures. In particular, the ferroelectric polarization vs. voltage data yield values of 0.61 μC/cm2 at 300 K to 3.29 μC/cm2 at 183 K; moreover, these data are in agreement with those reported in the literature. Magnetization vs. applied field data shows the magnetization at 300 K to be 180 emu/cm3 and increasing to 200 emu/cm3 at 10 K.

Hydrogen is a reliable energy vector and its storage is strongly connected to the costs, performance and level of safety of the storage system components. Several materials for physical and chemical hydrogen storage have been proposed, but few research works were devoted to polymers, that generally are low cost and weight materials, easy to be managed and manufactured. In this work, a functionalised Poly(ether ether ketone) (PEEK) polymer was studied and chosen as a base polymeric matrix with the aim to produce both a low cost and low weight hydrogen storage material. The polymer was in situ functionalised starting from a manganese oxide precursor. The obtained oxide, bonded to the polymer chain, allows the hydrogen storage. In this work, the functionalisation process and preliminary results of the hydrogen storage capability are reported.

From Scanning Electron Microscopy (SEM) and surface area measurements (BET), it has been verified that the metallic compound introduction modifies the morphology of the material, supplies an increased surface area for hydrogen chemisorption, revealing a 1.2%wt/wt hydrogen adsorption capability at 77 K. Preliminary results by Gravimetric Hydrogen Absorption measurements show that by increasing the temperature, the hydrogen storage capability is reduced and a value of 0.3%wt/wt at 50°C and 80 absolute bar was obtained. The reversibility cycles of hydrogen adsorption-desorption seem to be confirmed. For this reason such approach has been considered as a promising pathway and deeper studies are in progress.

We report on the crystalline structure, morphology and thermomagnetic properties of glass-coated magnetic microwires with Cu56Ga28Mn16 composition, as well as the thermal annealing influence on its magneto-structural properties. As-cast CuMnGa microwires exhibit a majority cubic B2 phase, and upon annealing at temperatures up to 573 K a new hexagonal phase appears coexisting with the cubic B2 major phase. Thermal annealing treatments also shift the Curie temperature about 150 K with respect to the one for the as-cast microwire. Furthermore, the signature of a structural phase transition is observed for the microwire annealed at 523 K

Cathodic protection has been applied for many years as the best method to prevent the corrosion in systems which transported hydrocarbon pipelines. However, it has found the presence of stress corrosion cracking (SCC) in steel pipelines with high concentrations of carbonates and bicarbonates with pH final (9 to 11). The resistance to the stress corrosion cracking of the API X-52 and API X-65 steels was evaluated on compact modified wedge opening specimens (WOL). The specimens were loaded of 95% of the yield strength. The resistance of crack propagation and the corrosion rate were evaluated with different applied potentials (-850 and -650 mV), this with respect to a saturated copper/copper sulfate reference electrode. The used electrolytes were simulated soils (carbonate-bicarbonate solution). Evidence of crack propagation of the API X-52 and API X-65 steels were carried out by scanning electron microscopy. The obtained result showed susceptibility to SCC on specimens with cathodic protection. The cathodic protection applied (-850 mV vs Cu/CuSO4 electrode) decreases considerably the corrosion rate on the evaluated steels. In this work the loaded stress showed to be a very important variable on the susceptibility to SCC.

Ordered mesoporous silicas continue to find widespread use as supports for diverse applications such as catalysis, separations, and sensors. They provide a versatile platform for these studies because of their high surface area and the ability to control pore size, topology, and surface properties over wide ranges. Furthermore, there is a diverse array of synthetic methodologies for tailoring the pore surface with organic, organometallic, and inorganic functional groups. In this paper, we will discuss two examples of tailored mesoporous silicas and the resultant impact on chemical reactivity. First, we explore the impact of pore confinement on the thermochemical reactivity of phenethyl phenyl ether (PhCH2CH2OPh, PPE), which is a model of the dominant β-aryl ether linkage present in lignin derived from woody biomass. The influence of PPE surface immobilization, grafting density, silica pore diameter, and presence of a second surface-grafted inert “spacer” molecule on the product selectivity has been examined. We will show that the product selectivity can be substantially altered compared with the inherent gas-phase selectivity. Second, we have recently initiated an investigation of mesoporous silica supported, heterobimetallic oxide materials for photocatalytic conversion of carbon dioxide. Through surface organometallic chemistry, isolated M-O-M’ species can be generated on mesoporous silicas that, upon irradiation, form metal to metal charge transfer bands capable of converting CO2 into CO. Initial results from studies of Ti(IV)-O-Sn(II) on SBA-15 will be presented.

Optically active InP nanowires were grown on a quartz substrate covered with a layer (100 nm) of hydrogenated amorphous silicon (a-Si:H) by metalorganic chemical vapor deposition (MOCVD), demonstrating that single-crystal semiconductor nanowires can be formed on non-single-crystal surfaces. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, cathodoluminescence (CL), and photoluminescence (PL) were used to characterize the structural and optical properties of the nanowires. The nanowires on a-Si:H grew in random directions with high density. The XRD suggests that nanowires having either hexagonal-close-packed or face-centered cubic lattices co-exist. The Raman spectrum shows peaks associated with transverse optical (TO) and longitudinal optical (LO) branches of InP. The CL intensity does not vary signi?cantly along the growth direction and appears to be originated from the entire structure of the nanowire when probed at various positions. The CL data suggests that recombination is slow enough to allow the carriers to diffuse the complete length of the nanowires (˜2 m in length) before recombining. The PL spectrum suggested the nanowire had a part that contributes to the observed blue shift while the other part had nearly bulk feature in their structure.

Directionally solidified alloys in the Ru-Mn-Si system exhibit a particular microstructure including columnar compositional variation due to the formation of many different chimney-ladder phases along the growth direction. Despite the existence of the compositional variation, the crystal orientations of the neighboring chimney-ladder phases are preserved. Over the compositional interfaces, the metal sublattice is considered to be continuous while the Si sublattice is not. Heat treatment of the directionally solidified alloy with the nominal composition of Ru0.10Mn0.90Si1.732 at 1100°C coarsens the compositional domains so as to reduce the density of the compositional interfaces. The values of the thermal conductivity increase with the decrease in the density of the compositional interfaces whereas those of the Seebeck coefficient and electrical resistivity are almost unchanged after the heat treatment. It is considered that the thermoelectric properties of the chimney-ladder compounds in the Ru-Mn-Si system can be enhanced by introducing a high density of the compositional interfaces.

Nanocrystalline ZnO thin films grown by the pulsed laser deposition technique were used to fabricate high performance thin film transistors suitable for RF applications. It was shown that drain current on/off ratios of higher than 1×1012, sub-threshold voltage swing values lower than 100 mV/decade and hysteresis-free operation could be maintained with films grown across a wide temperature range (25°C to 400°C). Films grown at 200°C have the lowest surface roughness and result in devices with the highest current density operation. Devices with 1.2 μm gate lengths and Au-based gate metals had record current gain and power gain cut off frequencies of fT = 2.9 GHz and fmax = 10 GHz, respectively.

A nitric acid (2M) pre-treatment is shown to increase the efficiency of a standard dye sensitized solar cell mounted on a FTO glass substrate from 4.15% to 5.12%. The pre-treatment involves immersing an FTO glass electrode coated with commercial ethyl cellulose based TiO2 paste for 1-60 minutes prior to sintering at 450°C. The pre-treatment leads to agglomeration of the TiO2 creating a scattering layer which covers the acid treated surface on short term immersion (<30 mins) and penetrates the bulk layer upon long immersion. The scattering layer itself takes up less of the sensitizing (N719) dye but scatters photons in the rest of the film. The optimum immersion time under room temperature conditions was found to be ca 20 minutes since at much longer immersion times the bulk film particle agglomeration reduced efficiency. The choice of anion in the acid is critical with certain species, notably phosphate, resulting in blockage of dye absorption sites in the entire film resulting in reduced cell efficiency.

Demand for high efficiency, low-cost solar cells has led to strong interest in post-deposition processing techniques that can improve the crystallinity of thick (1 to 40 μm) silicon films deposited at high growth rates. Here we describe a high temperature grain reorientation annealing process that enables the conversion of polycrystalline silicon (poly-Si) into a single crystal material having the orientation of an underlying single crystal Si seed layer. Poly-Si films of thickness 0.5 to 1.0 μm were deposited by low pressure chemical vapor deposition (LPCVD) on substrates comprising a surface thermal oxide or a 100-oriented single crystal silicon-on-insulator (SOI) layer. After annealing at 1300 °C for 1 hour, poly-Si on oxide shows very significant grain growth, as expected. In contrast, the poly-Si deposited on SOI showed no grain boundaries after annealing, transforming into a single crystal material with a fairly high density of stacking faults. Possible uses and drawbacks of this approach for solar cell applications will be discussed.

The effect of alloying elements Ta, Mo, W, Cr, Re, Ru, Co, and Ir on the elastic properties of both γ-Ni and γ′-Ni3Al is studied by first-principles method. Results for lattice properties, elastic moduli and the ductile/brittle behaviors are all presented. Our calculated values agree well with the existing experimental observations. Results show all the additions decrease the lattice misfit between and γ′ phases. Different alloying elements are found to have different effect on the elastic moduli of γ-Ni. Whereas all the alloying elements slightly increase the moduli of γ′-Ni3Al expect Co. Both of the two phases are becoming more brittle with alloying elements, but Co is excepted. The electronic structures of γ′ phase alloyed with different elements are provided as example to elucidate the different strengthening mechanisms.

We have theoretically evaluated the phase stability and electronic structure of Cu2ZnSnSe4 (CZTSe) and Cu2ZnSnS4 (CZTS). The enthalpies of formation for kesterite, stannite and wurtz-stannite phases of CZTSe and CZTS were calculated using a plane-wave pseudopotential method within the density functional formalism. For CZTSe, the calculated formation enthalpy (ΔH) of the kesterite phase (−312.7 kJ/mol) is a little smaller than that of the stannite phase (−311.3 kJ/mol) and much smaller than that of the wurtz-stannite phase (−305.7 kJ/mol). For CZTS, the ΔH of the kesterite phase (−361.9 kJ/mol) is smaller than that of the stannite phase (−359.9 kJ/mol) and much smaller than that of the wurtz-stannite phase (−354.6 kJ/mol). The difference of ΔH between the kesterite and stannite phases for CZTS is greater than that for CZTSe. This indicates the kesterite phase is more stable than the stannite phase in CZTS compared with CZTSe. The valence band maximums (VBMs) of both the kesterite- and stannite-type CZTSe(CZTS) are antibonding orbitals of Cu 3d and Se 4p (S 3p). The conduction band minimums (CBMs) are antibonding orbitals of Sn 5s and Se 4p (S 3p). The Zn atom does not affect the VBM or the CBM in either CZTSe(CZTS). The theoretical band gap of the kesterite phase calculated with sX-LDA in both CZTSe and CZTS is a little wider than that of the wurtz-stannite phase and much wider than that of the stannite phase.

Zinc oxide (ZnO) has attracted resurgent interest as an active material for energy-efficient lighting applications. An optically transparent crystal, ZnO emits light in the blue-to-UV region of the spectrum. The efficiency of the emission is higher than more “conventional” materials such as GaN, making ZnO a strong candidate for solid-state white lighting. Despite its advantages, however, ZnO suffers from a major drawback: as grown, it contains a relatively high level of donors. These unwanted defects compensate acceptors or donate free electrons to the conduction band, thereby keeping the Fermi level in the upper half of the band gap. This paper reviews recent work on hydrogen donors and nitrogen-hydrogen complexes in ZnO.

One of widely investigated materials for photodiode, light-emitting device, and solar cell applications is a soluble conjugated polymer poly(2-methoxy-5- (2,9-ethyl-hexyloxy)-1,4-phenylene vinylene) or MEH-PPV. In this paper we present experimental results on MEH-PPV polymer and ITO/PEDOT:PSS/MEH-PPV/Al photodetector, where ITO and PEDOT:PSS stand for indium tin oxide and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), respectively. Thin polymer films were fabricated by spin-coating technique. The characterization of the material and devices are done in air at room temperature. The experimental results include optical absorption of MEH-PPV and determination of the optical absorption coefficient, photocurrent dependence on optical power, light wavelength, bias voltage, and polymer thin film thickness. Theoretical modeling is based on drift-diffusion and continuity equations for hole polarons, as well as assumption that the charge carrier recombination process is bimolecular. The bimolecular recombination mechanism implies that the photocurrent depends on the square root of the optical power, which is confirmed with our experimental results.