The performance of commercially available silicon carbide (SiC) power devices is limited due to inherently high density of screw dislocations (SD), which are necessary for maintaining polytype during boule growth and commercially viable growth rates. The NASA Glenn Research Center (GRC) has recently proposed a new bulk growth process based on axial fiber growth (parallel to the c-axis) followed by lateral expansion (perpendicular to the c-axis) for producing multi-faceted m-plane SiC boules that can potentially produce wafers with as few as one SD per wafer. In order to implement this novel growth technique, the lateral homoepitaxial growth expansion of a SiC fiber without introducing a significant number of additional defects is critical. Lateral expansion is being investigated by hot wall chemical vapor deposition (HWCVD) growth of 6H-SiC a/m-plane seed crystals (0.8mm x 0.5mm x 15mm) designed to replicate axially grown SiC single crystal fibers. The post-growth crystals exhibit hexagonal morphology with approximately 1500 μm (1.5 mm) of total lateral expansion. Preliminary analysis by synchrotron white beam x-ray topography (SWBXT) confirms that the growth was homoepitaxial, matching the polytype of the respective underlying region of the seed crystal. Axial and transverse sections from the as-grown crystal samples were characterized in detail by a combination of SWBXT, transmission electron microscopy (TEM) and Raman spectroscopy to map defect types and distribution. X-ray diffraction analysis indicates the seed crystal contained stacking disorders and this appears to have been reproduced in the lateral growth sections. Analysis of the relative intensity for folded transverse acoustic (FTA) and optical (FTO) modes on the Raman spectra indicate the existence of stacking faults (SFs). Further, the density of stacking faults is higher in the seed than in the grown crystal. Bundles of dislocations are observed propagating from the seed in m-axis lateral directions. Contrast extinction analysis of these dislocation lines reveals they are edge type basal plane dislocations that track the growth direction. Polytype phase transition and stacking faults were observed by high-resolution TEM (HRTEM), in agreement with SWBXT and Raman scattering.

We investigated the photovoltaic (PV) parameters of a planar hetero-junction solar cell with di-[4-(N,Nditolyl-amino)-phenyl] cyclohexane (TAPC) as donor (D) and C60 as acceptor (A), upon exposing the acceptor side to oxygen and moisture. We found that for the same time of exposure, even minor oxygen amounts lead to more detrimental results compared to moisture. We argue that the photo-conversion efficiency (PCE) decreases due to creation of recombination centers at the interface, which induce losses in exciton diffusion and charge generation. Under the same conditions, we also registered a direct connection between the cell PV parameters’ decay and a C60 thin-film conductivity loss.

The tube-length distribution in the semiconducting single-wall carbon nanotube (s-SWCNT) ink extracted by the electric-field-induced layer formation (ELF) method was characterized by atomic force microscopy, which revealed that the nonionic surfactant Brij 700 adopted in ELF causes the significant and homogeneous shortening of SWCNTs compared with sodium cholate that is frequently used for the dispersion of SWCNTs as an ionic surfactant. It was found that the shortened s-SWCNTs in the semiconducting ink positively effect on the uniformity of performance among the s-SWCNT thin-film transistors.

Catalyst-free vapor phase transport was applied for the growth of ZnO nanoemitters. A single-crystalline ZnO:Al seed layer was deposited and used as a pseudo-catalyst. The desired morphology of nanostructures can be achieved by means of modifying the growth rates of crystal planes via adjustment in the growth conditions. The field emission characteristics of ZnO nanoemitters satisfied the Fowler-Nordheim relationship. The high aspect ratio of nanoemitters had a low turn-on electric field of 0.18 MV/m at emission current density of 0.1 μA/cm2. A stable electron emission with a variation of less than 14% was measured.

C-14 contained in Hull waste is one of the most important radionuclides in the safety assessment of transuranic (TRU) waste disposal. For more realistic safety assessment, it is important to clarify the release mechanism and chemical species of C-14 from Hull waste. In this research, leaching tests were conducted using an irradiated Zry cladding tube from a boiling-water reactor (BWR) to obtain leaching data and to investigate the relationship between Zry metal corrosion and C-14 release behavior. Both organic and inorganic C-14 compounds existed in the the liquid phase, and some C-14 moved to the gaseous phase. The release rate of C-14 obtained from the BWR cladding tube after two-year leaching tests was lower than the release rate from a pressurize water reactor (PWR) cladding tube. It is considered that the BWR cladding tube used in this test did not easily corrode since it used a comparatively new material. The release rate of C-14 was slightly lower as compared with the corrosion rate of unirradiated Zry. This is thought to be the result of improved corrosion resistance conferred by neutron irradiation, which encouraged the dissolution of grain boundary precipitation elements, such as Fe, Cr, and Ni, into the crystal grains. The leaching tests will be continued for 10 years.

A new route for atom-economical synthesis of functional polymers was developed. Oxidative polycoupling of 3,5-dimethyl-1-phenylpyrazole with 4,4’-(α,ω-alkylenedioxy) bis(diphenylacetylene)s and 1,2-diphenyl-1,2-bis[4-(phenylethynyl)phenyl]ethene, respectively, were catalyzed by [Cp*RhCl2]2, 1,2,3,4-tetraphenylcyclopenta-1,3-diene and copper(II) acetate in dimethylformamide under stoichiometric imbalance conditions, affording soluble poly(pyrazolylnaphthalene)s in satisfactory yields (isolation yield up to 82%) with high molecular weights (M w up to 35700). All the polymers were thermally stable, losing little of their weight at high temperatures of 323–422 oC. They possessed good film-forming property and their thin solid films showed high refractive indices (RI = 1.747–1.593) in a wide wavelength region of 400−1000 nm. The polymer carrying tetraphenylethene unit displayed a phenomenon of aggregation-induced emission and showed enhanced light emission in the aggregated state.

Morphology of the active layer in bulk heterojunction P3HT:PCBM organic solar cell was studied using Monte Carlo (MC) and coarse-grained dynamics simulations. While coarse-grained molecular dynamics allow us to quickly estimate the P3HT:PCBM interfacial energy of bilayer structure as a function of underlying layer thickness, bridging the dimension and time gap between dynamics simulations and experiment is computationally expensive and therefore not viable. Using MC technique with input from dynamics simulations allowed us to speed up the calculation and obtain final morphological information based on energetics and entropy, and at the same time retained the physics fidelity in-built in our validated coarse-grained model. The final structure gives phase separated domains with dimension of approximately 12 nm, on par with reported experimental result. The method can be applied to other organic photovoltaics systems to predict active layer morphology relevant for device performance or 3-dimensional device modelling at continuum level.

In the study of cultural heritage, most of the analytical techniques are point-specific or give information about small areas of the object. Therefore it is essential to obtain an overview of which points are suitable for these further investigations. To fulfill this, a first imaging study is the best way to proceed. Hereby, we can record the entire piece at once and observe the behavior and relation between different materials of the object. Various types of light can be used to obtain a selection of images and consequently also different information about the artifacts. Among them, infrared (IR) photography can be used as a first analysis, for instance, to reveal the pigments’ response upon interaction with IR radiation.

In following we will present results obtained via IR video-photography on a selection of painted objects from the Mexican cultural heritage. These items are analyzed by False Color procedure, where colors are assigned to every grey tone of the pure IR photo. Hereby it is possible to distinguish between certain pigments on the painted surface.

Ba3-xKxHx(PO4)2 is a candidate solid-state proton conductor for solid acid fuel cells that is water-insoluble. The measured conductivity of ∼ 2.4 10-5 S cm-1 for the composition x=0.80 at 250°C is not competitive for solid acid fuel cell applications. This work investigates a methods for synthesizing solid acid electrolytes with the strategy of increasing proton conductivity by cation substitution and decreasing particle size. We report on the synthesis of nano Ba3-xKxHx(PO4)2 to a novel Ba3-xNaxHx(PO4)2. X-ray diffraction was used to confirm the Ba3(PO4)2 crystal structure and measure lattice strain as a function of cation substitution. SEM confirmed the morphology of micro Ba3-xNaxHx(PO4)2 is substantially different from micro Ba3-xKxHx(PO4)2, suggesting that Ba3-xNaxHx(PO4)2 has a different growth kinetics.

In recent years, studies have shown that single crystal metallic nanowires (NWs) can exhibit unique pseudoelastic behavior when their cross-sectional area is smaller than a certain critical value, which is on the order of a few nms. The mechanism responsible for this behavior is the formation of partial dislocations (twinning). In this paper we demonstrate using molecular dynamics simulations that thicker composite nanowires can exhibit pseudoelastic behavior at large cross-sectional dimensions to 28 nm and higher, as long as the individual layer thickness do not exceed a critical value of 1.8-2 nm, thus making their manufacturing feasible and more attractive.

In this study a scanning near-field ellipsometric microscope (SNEM), a hybrid device of an atomic force microscope (AFM) and an ellipsometer, is used to obtain optical images of heterogeneous polymer thin films with a resolution below the diffraction limit of light. SNEM optical images of a microphase separated PS-b-P2VP block copolymer film collected with gold coated and bare silicon AFM probe tips were compared to obtain a deeper insight into the nature of the SNEM contrast mechanism. Furthermore, intensity vs. distance curves were recorded on a PS-b-PMMA block copolymer film simultaneously during the acquisition of force-displacement curves to study the far-field contribution of the optical signal to the optical image.

Direct heteroarylation polymerization was employed to synthesize a novel low bandgap polymer, used as a p-type material of polymer photovoltaic cells. To achieve low bandgap of conjugated polymers, electron donor-acceptor (D-A) alternating strategy was used. The electron-donating 3-alkylthiophene and electron-withdrawing cyanothiophene were coupled to be polymerized via direct heteroarylation polymerization. The cyano moiety of the polymer backbone allowed a strong intermolecular interaction between neighboring chains and improved the structural perfection of the crystal structure on the substrate. The solar cell devices of ITO/PEDOT:PSS/P3HT:PCBM/LiF/Al were fabricated on ITO-coated glass substrate.

Semiconducting and insulating polymers and copolymers/Au nanograins based hybrid multilayers (HyMLs) were fabricated on p-Si single-crystal substrate by an iterative method that involves, respectively, Langmuir-Blodgett and spin-coating techniques (for the deposition of organic film) and sputtering technique (for the deposition of metal nanograins) to prepare Au/HyMLs/p-Si Schottky device. The electrical properties of the Au/HyMLs/p-Si Schottky device were investigated by current-voltage (I–V) measurements in the thickness range of 1-5 bilayers (BL).

At different number of layers, current-voltage (I–V) measurements were performed. Results showed a rectifying behavior. Junction parameters, such as barrier height (BH), from the I–V measurements for example for the PMMA-b-PS based Au/HyMLs/p-Si structure were obtained as 0.72±0.02 eV at 1BL and 0.64±0.02eV at 5BL. It was observed that the BH value of 0.61 eV obtained for the 5 BL PS based Au/HyMLs/p-Si structure was lower than the value of 0.68 eV of conventional Au/p-Si Schottky diodes. Thus, modification of the interfacial potential barrier for Au/p-Si diodes has been achieved using a thin MLs of different polymers based HyMls semiconductor.

In biological applications, conjugated polymers offer many advantages compared to inorganic semiconductors, due to their favorable electrical properties and their biocompatibility. Many different parameters affect the cell-substrate interaction and in this work we focus our attention on the role played by the oxidation state and surface morphology of conducting polymer substrates. We realized cell culture substrates using a thin film of a biocompatible conducting polymer widely employed in organic electronics, poly(3,4-ethylene dioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS). The oxidation state of the samples was electrochemically modified through the application of a fixed potential, and they were subsequently characterized by atomic force microscopy and optical spectroscopy. Using these techniques we have been able to measure the oxidation state of the polymer films, and to asses that its surface roughness does not depend on its oxidation state. Furthermore, human dermal fibroblast (hDF) were grown on PEDOT:PSS films with different oxidation state, in order to test their efficacy as cell culture substrates and their biocompatibility.

Amyloid fibrils, which are linear proteins with widths of less than 10 nm and lengths of more than 1 μm, were used as an amorphous carbon template for graphene nanoribbons (GNRs) synthesized by solid-phase graphitization using liquid Ga as the catalyst. The crystal quality of the GNRs improved with increasing synthesis temperature. However, the shape of the GNRs synthesized at temperatures higher than 900 °C became broader, losing the original amyloid shape, whereas the GNRs synthesized at 900 °C seemed to maintain the original amyloid shape in the SEM observation. The conducting paths of GNRs synthesized at 900 °C were found to be slightly diffused outside the topography of the GNRs in the conductive atomic force microscopy map. In addition, some of the sapphire terrace edges of the substrate showed conductivity, which indicates that the growth mechanism of graphene on a sapphire substrate might be a step-flow growth mode.

A simulated Magnox glass which is Mg- and Al- rich was subjected to aqueous corrosion in static mode with deionised water at 90 °C for 7-28 days and assessed using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) with Energy X-Ray Dispersive Spectroscopy (EDS) and Inductively Coupled Plasma – Optical Emission Spectroscopy (ICP-OES). XRD revealed both amorphous phase and crystals in the glass structure. The crystals were Ni and Cr rich spinels and ruthenium oxide. After two weeks of incubation in deionised water, the glass surface was covered by a ∼11 μm thick Si-rich layer whilst mobile elements and transition metals like Na, B, and Fe were strongly depleted. The likely corrosion mechanism and in particular the role of Mg and Al in the glass structure are discussed.

We report photo induced minority carrier annihilation at the silicon surface in a metal–oxide–semiconductor (MOS) structure using 9.35 GHz microwave transmittance measurement. 7 Ωcm n-type 500-μm-thick crystalline silicon substrate coated with 100-nm-thick thermally grown SiO2 layers was used. 0.2-cm-long Al electrode bars were formed at the top and rear surfaces. 635 nm light illumination onto the top surface caused photo induced carriers to be in one side of the silicon region of the Al electrode. Microwave transmittance system detected photo induced carriers diffused from the light illuminated region via the MOS structured region. When the bias voltage was applied at +2.0 and -2.2 V to the electrode at the top surface, the surface recombination velocity increased from 44 (initial) to 83 and 86 cm/s, respectively because of depletion region formation at rear and top surface respectively. Those voltage applications caused change in the distribution of photo induced carriers in a 0.6-cm-wide region including light illuminated, MOS structured, microwave irradiated regions.