Transparent polymer nanocomposites with high refractive index were prepared by grafting polymer chains onto TiO2 nanoparticles. Reversible addition-fragmentation chain transfer (RAFT) polymerization was used to prepare poly(methyl methacrylate) (PMMA) polymer brushes grafted from TiO2 nanoparticles. The refractive index of the hybrid material increased from 1.49 for neat PMMA to 1.6 by increasing the loading of TiO2 to 40 weight percent. UV-vis spectra showed that grafted particles had a transparency of more than 90% in the visible light range. The hybrid particles can be processed into transparent, high refractive index coatings and self-standing films. The grafted TiO2 nanoparticles can also be easily dispersed into a polymer matrix forming thick, robust transparent polymer nanocomposites.

In this article, (100) Ib diamond substrates are pre-treated for different durations in an O2/H2-plasma, influencing the etching of defects like unepitaxial crystals, flat top hillocks, and pyramidal hillocks [1-3]. Such procedure is used to prevent those to incorporate into the ~ 100μm thick CVD diamond film, which is subsequently grown on top. While the surface morphology and structure of substrates and films are studied by SEM, the time-resolved Light-Induced Transient Grating (LITG) technique provides information on the excess carrier parameters close to the front surface of the grown layers. This technique is particularly useful as it does not requires a separation of the CVD film from its substrate. It will be shown that O2/H2-plasma treatments of more than 150 minutes but less than 240 minutes largely reduce the incorporation of defects in the bulk of the grown film. This, in turn, influences the carrier dynamics as measured by LITG, but also the surface roughness and growth rate as shown by SEM.

Properties of hydrogenated icosahedral aluminum clusters were investigated using density functional theory in comparison with those of aluminum bulk systems. Two surface models simulating f.c.c. and icosahedral (111) surfaces were introduced. Results show that the H atom interacts weakly with surface of clusters when the cluster size is increased. The migration energy of H atom between neighboring T and O sites becomes smaller for icosahedral subsurface than for either bulk material or the f.c.c. subsurface. The results indicate that the icosahedral surface is more favored for H atom to adsorp than f.c.c. surface, the icosahedral surface increases the migration barriers of H atom from the surface to the subsurface.

United Solar Ovonic has leveraged its history of making amorphous silicon solar cells on stainless steel substrates to develop amorphous silicon alloy (a-Si:H)-based solar cells and modules on ∼25 μm thick polymer substrate using high-throughput roll-to-roll deposition technology for space and near-space applications. The solar cells have a triple-junction a-Si:H/a-SiGe:H/a-SiGe:H structure deposited by conventional plasma enhanced CVD (PECVD) using roll-to-roll processing. The cells have distinct advantages in terms of high specific power (W/kg), high flexibility, ruggedness, rollability for stowage, and irradiation resistance. The large area (23.9 cm x 32.1 cm) individual cells manufactured in large quantity can be readily connected into modules and have achieved initial, 25 °C, AM0 aperture-area efficiency of 9.8% and initial specific power of 1200 W/kg. We have conducted light-soak studies and measured the temperature coefficient of the current-voltage characteristics to determine the stable values at an expected operating temperature of 60 °C. The stable total-area efficiency and specific power at 60 °C are 7.2% and 950 W/kg, respectively. In this paper, we review the challenges and progress made in development of the cells, highlight some applications, and discuss current efforts aimed at improving performance.

A soluble polyaniline was synthesized through emulsion polymerization and characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), gel permeation chromatography (GPC), viscosity analysis, and coefficient of linear thermal expansion (CLTE) determination. The electrical conductivity is found to reach 1000 S/cm with specific post doping treatments. Multiple printing processes, such as inkjet printing, screen printing and aerosol jet printing etc, make it feasible to print a variety of sensor patterns. The electromechanical response of these sensors was used to measure strain/stress or damage of composite structures under various load conditions expected to be experienced by aircraft. These unique conductive polymer sensors provide a feasible, near real time monitoring system for composites without adding significant additional weight to the structure.

Recently, it was proposed that graphene sheets deposited on silicon oxide can act as impermeable atomic membranes to standard gases, such as helium, argon, and nitrogen. It is assumed that graphene membrane is clamped over the surface due only to van der Waals forces. The leakage mechanism can be experimentally addressed only indirectly. In this work we have carried out molecular dynamics simulations to study this problem. We have considered nano-containers composed of a chamber of silicon oxide filled with gas and sealed by single and multi-layer graphene membranes. The obtained results are in good qualitative agreement with the experimental data. We observed that the graphene membranes remain attached to the substrate for pressure values up to two times the largest value experimentally investigated. We did not observe any gas leakage through the membrane/substrate interface until the critical limit is reached and then a sudden membrane detachment occurs.

Freestanding, strip-shaped magnetoelastic (ME) biosensors are a class ofwireless, mass-based biosensors that are being developed for the real-timedetection of pathogenic bacteria for food safety and bio-security. The masssensitivity of these biosensors operating in longitudinal-vibration modes isknown to be largely dependent on the position of masses attached to thesensor surfaces. Hence, considering this dependence is crucial to thedetection of low-concentration target pathogens, including single pathogenicbacteria, because their local attachment may cause varying sensor responses.In a worst case scenario, the resultant sensor responses (i.e., mass-inducedresonance frequency changes of the sensor) may be too small to be detecteddespite the attachment of the target pathogenic masses. To address theissue, phage-coated ME biosensors (magnetostrictive strips (4 mm × 0.8 mm ×30 μm) coated with a phage probe specifically binding streptavidin protein)with localized masses (streptavidin-coated polystyrene beads) werefabricated, and mass-position-dependence of the sensor’s sensitivity underthe fundamental-mode vibration was experimentally measured. In addition,three-dimensional finite element (FE) modal analysis was performed using theCalculiX software to simulate the phenomena. The experimental andtheoretical results show close agreement: (1) the mass sensitivity was lowwhen the mass was positioned in the middle of the sensor’s longest dimensionand (2) a much higher mass sensitivity was, by contrast, obtained for theequivalent masses placed at both ends of the strip-shaped sensor.Furthermore, FE models were constructed for differently sized, phage-coatedME biosensors (100 – 500 μm in length with different widths and thicknesses)loaded with a single bacterial mass (2 μm × 0.4 μm × 0.4 μm, 1.05 g/cm3) at varying longitudinal positions. The mass sensitivitywas found to be approximated by a mass-position-dependent Boltzmann functionwhose amplitude is inversely proportional to the length squared, width, andthickness of the sensor.

There is an acute and well-documented need for image processing of microscopy data in materials science regarding, for example, the characterization of the structure/property relationship of a given materials system. In our work, image processing has been used as a framework for conducting interdisciplinary team-based research that effectively integrates programs within the Center for Research on Interface Structures and Phenomena (CRISP) Materials Research Science and Engineering Center (MRSEC), e.g. research experiences for undergraduates (REU), teachers (RET) and high school fellowships. This research resulted from a five-year long collaboration between CRISP and the Physics and Computer Science Departments at Southern Connecticut State University (SCSU). This paper will focus on the implementation of team-based research experiences as a vehicle for interdisciplinary science and education. Representative results of several of the studies are presented and discussed.

Al2O3 films (2-5nm) deposited on SiO2/Si (100) n-type substrate with thickness 500μm were characterized by Synchrotron Radiation- X-ray Photoelectron Spectroscopy (SR-XPS). Excitation energy 730eV show surface sensitive results compare to 1000eV. Using excitation energy 730eV, Al, Si, O core-level elements and their excited species were analyzed. Plasmon loss peak with energy separation (18.8-19.1eV) for Al2p main peak and (14.7-15.3eV) for Al2s main peak is likely due to bulk plasmon. XPS spectra of O1s peak showed different onset and energy seperation for each sample. Energy seperation between O1s peak and onset of plasmon is 8.4eV for 5nm lead to band gap of Al2O3 layer. But and in case of 2nm this value is 9.2eV, hence, it is likely corresponds to SiO2 interfacial layer.The reason for this might consider as top Al2O3 form island rather than homogenous oxide layer.

Organic photovoltaic devices offer a potentially cheap source of electrical power due to the relative ease of processing compared to silicon devices. Over the last decade the efficiency of these devices has improved significantly and the best devices are currently have >6% power conversion efficiency and ~100% quantum efficiency.

A novel blend of ferroelectric nanostructures, poly(3-hexylthiophene) (P3HT) and [6, 6]-phenyl-C61-butyric acid methyl ester (PCBM) has been used to fabricate hybrid organic and inorganic photovoltaic devices. These devices comprise a glass substrate coated with indium tin oxide (ITO) and an layer of PEDOT:PSS to form the first electrode. The active layer was deposited by spin coating and finally metallic top contacts have been added by thermal evaporation. The devices were characterized using standard current-voltage (IV) measurements under illuminated and dark conditions using an AM1.5 solar simulator and a source-voltage device and the results indicate a difference in efficiency compared to similar devices fabricated at the same time without the novel nanostructures. Additional UV-Vis measurements were used to determine the absorption characteristics of the active layers. The initial results suggest an improvement in the absorption of light in the visible region and higher open circuit voltages and short circuit currents compared to P3HT/PCBM alone.

In this paper, we investigate the morphology variation of Au-assisted epitaxial InSb nanowires (NWs) dependence on growth temperature and growth duration by chemical vapor deposition (CVD). The NW length and tapering factor correlated to the NW morphology are determined as a function of growth temperature (300°C-480°C). Higher density and longer NWs were observed on the substrate as proportional to the growth duration. The growth direction of the NWs is <110> by Transmission Electron Microscopy (TEM) studies. The aim of this study is to gain better understanding of the III-V NWs growth mechanism and achieve control over the growth of InSb NWs.

We investigate theoretically and experimentally the temperature-dependent linear optical properties of the clean c(4×2) reconstructed Si(100) surface for a wide range of temperatures. We combine two theoretical formalisms: the first one incorporates the contribution of temperature-dependent atomic motion to the surface optical response and, the second uses a dielectric function layer-by-layer separation method. Using these formalisms, we model temperature-dependent reflectance anisotropy (RA) of this surface for the first time: finite temperature ab-initio Car-Parrinello Molecular Dynamics (CPMD) at different temperatures up to 1000 K provide temperature-dependent atomic structural inputs for optical calculations and subsequent average of dielectric functions. Experimentally, one-domain c(4x2) Si(100) surface was prepared and characterised by Reflectance Anisotropy Spectroscopy (RAS) in a temperature range between 300 K and 800 K. Good agreement between experiment and theory is demonstrated, including a temperature-induced red shift of both the surface and bulk optical peaks. Theoretical results indicate that the temperature-induced modification of the optical response is substantially more pronounced for the surface than for the bulk.

We report on the usage of a simple microfabricateddevice, that works in conjunction with a quantitative nanoindenter inside a scanning electron microscope (SEM), for the in situ quantitative tensile testing of individual sidewall fluorinated multi-wall carbon nanotubes (MWNTs). The stress vs. strain curves and the tensile strength values for five fluorinated specimens have been presented and compared to those of pristine MWNT specimens (data reported earlier). The fluorinated specimens were found to deform and fail in a brittle fashion similar to pristine MWNTs. However, sidewall fluorination was found to have considerably degraded the mechanical properties (tensile strength and load bearing capacity) of the MWNTs.

The present paper describes an unconventional approach to fabricate superhydrophilic-superhydrophobic template on the TiO2 nanotube structured film by a combination of electrochemical anodization and photocatalytic lithography. Based on template with extreme wetting contrast, various functional nanostructures micropattern with high resolution have been successfully fabricated. The resultant micropattern has been characterized with scanning electron microscopy, optical microscopy, X-ray photoelectron spectroscopy. It is shown that functional nanostructures can be selectively grown at superhydrophilic areas which are confined by the hydrophobic regions, indicating that the combined process of electrochemically self-assembly and photocatalytic lithography is a very promising approach for constructing well-defined templates for various functional materials growth.

We report on Scanning Thermal Lithography (SThL), a recently introduced lithographic tool, for local thermochemistry on tert-butyl acrylate based polymer films featuring chemical cross links. The tailored polymer films afford platforms for controlled high molecular density coupling and surface immobilization of biologically relevant molecules, such as proteins. The thermally labile tert-butyl ester groups in tert-butyl acrylate based polymer films can be cleaved in air at temperatures above 150 °C to yield carboxylic acid functional groups for further (bio)- conjugation. The films were optimized to avoid plastic deformation at the elevated temperatures used during SThL. Exploiting these properties patterns with length scales as small as 35 ± 6 nm have been successfully thermally activated with SThL. Hence SThL comprises an attractive approach for the development of e.g. (bio)sensors and platforms for cell surface interaction studies with nanoscale patterns.

The Coulomb blockade behavior was observed for both C60-PCBM and C70-PCBM at room temperature utilizing a nonvolatile memorycell fabricated through a liquid-transfer process. Room-temperature andlow-temperature (10K) electrical characterizations verified the blockadeeffect was originated from both molecular energy levels and single electroncharging energy. Molecular orbital energy was extracted and shown goodagreement with the literature [1].The successful integration and operationof this hybrid structure signified a strong potential for molecule-basedelectronic device design.

Silicon nanocrystals (nc-Si), have been shown to act as opto-electronic centers enabling light emission by carrier recombination, when precipitated in a silicon nitride (Si3N4) host. In this work, nc-Si and Germanium nanocrystals (nc-Ge) are studied in sputtered films of Si3N4 and SiGeN for application as tandem cell layers in a Si solar cell. The samples are annealed in a nitrogen gas and forming gas ambient, from 500 ºC to 900 ºC, to investigate the influence of temperature on photoluminescence and photoconductivity.

The structures, energies, and energy levels of a comprehensive set of simple intrinsic point defects in aluminum arsenide are predicted using density functional theory (DFT). The calculations incorporate explicit and rigorous treatment of charged supercell boundary conditions. The predicted defect energy levels, computed as total energy differences, do not suffer from the DFT band gap problem, spanning the experimental gap despite the Kohn-Sham eigenvalue gap being much smaller than experiment. Defects in AlAs exhibit a surprising complexity—with a greater range of charge states, bistabilities, and multiple negative-U systems—that would be impossible to resolve with experiment alone. The simulation results can be used to populate defect physics models in III-V semiconductor device simulations with reliable quantities in those cases where experimental data is lacking, as in AlAs.

Cu(In,Ga)Se2 (CIGS) is one of the most advanced absorber materials with conversion efficiencies reaching up to about 20%. Electrodeposition of CIGS precursors is highly attractive due to its low cost, efficient utilization of raw materials and scalability to high-volume manufacturing, however, a strict chemistry control of the plating baths is required in a manufacturing environment to ensure a consistent plating process with high yields. In the present study, we tested the use of ion chromatography (IC), for the quantitative analysis of both the cationic and anionic species in a variety of aqueous alkaline electroplating solutions we developed for the fabrication of CIGS precursors. Using ion chromatography we were able to precisely determine the concentrations of several key anions commonly employed in the plating baths including chloride, sulfate, selenite, selenate, tartrate, citrate, gluconate, and ethylenediaminetetraacetate. Our results indicated IC might not be a suitable method to determine the cationic concentrations for Cu, In, Ga ions when complexing species, such as ethylenediaminetetraacetate, are present in the electroplating solutions. We determined that inductively coupled plasma optical emission spectroscopy (ICP-OES) could be used instead for the precise determination of the cationic concentrations.