bluuebunny/crossref_metadata_2025_split huggingface dataset:
Statistical Analysis of Nanoimpact Testing of Hard CrAl(Si)N Coatings
Authors: Mosquera A. , Mera L. , Fox-Rabinovich G.S. , Martínez A. , Azkona I. , Endrino J. L 
Published: September 2011

ABSTRACTStatistical studies involving the fracture behavior of coatings can play an important role in the mechanical analysis of films employed in the hard coating industry. In this study, Nanoimpact tests using a cube corner indenter were carried out in various CrAl(Si)N coatings for the quantitative assessment of properties of coatings like non-catastropic failure time and catastrophic failure time. These parameters decrease in value as silicon is incorporated in coatings, showing that this addition results in a decrease in ductility. Scanning electron microscope images were taken to the analyzed coatings exhibiting the residual imprints after nanoimpact test that were correlated with the fracture behavior of CrAl(Si)N coatings.
Scattering Under Shear: Alignment of a Disordered Bicontinuous Mesophase
Authors: Seddon Annela M. , Lötze Gudrun , Plivelic Tomás , Squires Adam M. 
Published: September 2011

ABSTRACTIn this work we demonstrate that the application of shear to a disordered lyoptropic liquid phase formed by a biological lipid, monoolein formed in water and butanediol results in the formation of an aligned lamellar phase. Furthermore we show that if shear is applied to this disordered phase in the presence of additional water, an highly oriented inverse bicontinous cubic phase is created. We suggest that these two phase may have applications as biological models, as templates for nanostructured materials and in improved protein crystallization techniques.
Energy Harvesting Technology Development at DARPA
Authors: Greanya Viktoria , Daniell Cynthia , Nehl Colleen 
Published: September 2011

ABSTRACTPrograms in the Defense Sciences Office (DSO) at the Defense Advanced Research Projects Agency (DARPA) bridge the gap from fundamental science to applications by identifying and pursuing the most promising ideas within the science and engineering research communities and transforming these ideas into new DoD capabilities. The Department of Defense (DoD) recognizes that our dependence on fossil fuel must be reduced and is actively supporting new technical solutions to this challenge. Moreover, advancements in alternative energy generation and storage technologies will render the warfighter more efficient, capable and mobile. Energy harvesting is a central pathway to solving this critical need. This paper will highlight two DARPA DSO programs which are making significant strides in the advancement in materials to improve energy harvesting technology with a focus on rapid transition to the end user. The Nanostructured Materials for Power (NMP) program is developing high performance thermoelectric materials and devices for energy harvesting with goals of energy conversion of 30%. The Low-Cost, Lightweight Portable Photovoltaics (PoP) program is developing integrated PV technologies with high power conversion efficiency (20%) in a form factor capable of being produced at low cost on flexible substrates. The paper will review the goals of the programs, discuss their implications, and highlight some of the research strategies underway.
Electron emission from deep traps in hydrogenated amorphous silicon and silicon-germanium: Meyer-Neldel behavior and ionization entropy
Authors: Long Qi , Dinca Steluta , Schiff Eric A. , Yan Baojie , Yang Jeff , Guha Subhendu 
Published: September 2011

ABSTRACTWe have measured electron drift in amorphous silicon-germanium nip photodiodes using the photocarrier time-of-flight technique. The samples show electron deep-trapping shortly after photogeneration, which is generally attributed to capture by a neutral dangling bond (D0) to form a negatively charged center (D-). An unusual feature is that electron re-emission from the trap is also clearly seen in the transients. Temperature-dependent measurements on the emission yield an activation energy of about 0.8 eV and the remarkably large value of 1015 Hz for the emission prefactor frequency. We also compiled results on electron emission from deep traps in a-Si:H, a-SiGe:H, and a-SiC:H from six previous publications. Collectively, these measurements exhibit "Meyer Neldel" behavior for electron emission over a range of activation energies from 0.2–0.8 eV and a prefactor range extending over nine decades, from 106 to 1015 Hz. The Meyer-Neldel behavior is consistent with the predictions of the multi-excitation entropy model. We extract a ionization entropy of 20kB from the measurements, which is very large compared to crystal silicon. We discuss this result in terms of a bond charge model.
Amorphous Silicon Photosensors for Detection of Intrinsic Cell Fluorophores
Authors: Joskowiak A. , Chu V. , Prazeres D.M.F. , Conde J.P. 
Published: September 2011

ABSTRACTAn amorphous silicon (a-Si:H) photoconductor array with two distinct integrated amorphous silicon carbon alloy (a-SiC:H) high pass filters is used to detect two of the cell intrinsic fluorophores. The cutoff wavelength of the filters is tuned by the carbon content in the film. The fluorophores of interest – reduced nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) are indicative of the redox state of the cells. Concentrations down to 1 μM for NADH and 50 μM for FAD were detected.
A Less Damaging Patterning Regime for a Successful Integration of Ultra Low-k Materials in Modern Nanoelectronic Devices
Authors: Zimmermann Sven , Ahner Nicole , Fischer Tobias , Schaller Matthias , Schulz Stefan E. , Gessner Thomas 
Published: September 2011

ABSTRACTThis paper describes a three-step process regime for the integration of porous SiCOH based ultra low-k materials in existing copper damascene technologies. During the work with these complex and sensitive materials, it became more and more clear, that a successful patterning depends not only on the etch step but also on the adjustment between the etch and the following cleaning and k-restore processes. The presented process regime starts with a reactive ion etch process for trench patterning followed by a post etch clean to remove etch residues. Finally a k-restore process was performed to repair the damaged regions in the trench sidewalls. In this work it became clear, that the etch chemistry influences not only the results of the etch process ostensibly sidewall damage but also kind and effect of the post etch clean. Each plasma composition results in the necessity of a customized post etch cleaning solution. Finally a k-restore process using Hexamethyldisilazane (HMDS) as restore chemical was demonstrated successfully. Enhanced temperatures and an additional UV-treatment are possibilities to promote the restore effect.
Array of silicon field effect transistors to detect charges propagation in neurons circuit
Authors: Delacour C. , Bugnicourt G. , Bres G. , Crozes T. , Villard C. 
Published: September 2011

ABSTRACTWe present transport properties of silicon nanowires field effect transistors realized on SOI substrates and their application to probe electrical activity of biological objects. Devices are sensitive to short and weak voltage pulses (ms, mV) applied in an electrolyte solution, allowing a future efficient detection of neuronal activity. For that purpose, the organized growth of neuronal cells along chosen patterns has been obtained, leading to an accurate coupling with silicon nanowire field effect transistors. Both network architectures, neural and semiconducting, have been designed to study some aspects of the propagation and the processing of information by the nervous system.
Electric field effect in amorphous semiconductor films assembled from transition-metal-encapsulating Si clusters
Authors: Uchida N. , Miyazaki T. , Matsushita Y. , Sameshima K. , Kanayama T. 
Published: September 2011

ABSTRACTWe synthesized amorphous semiconductor films composed of Mo-encapsulating Si clusters (MoSin:n∼10) on solid substrates. The MoSi10films had Si networks similar to hydrogenated amorphous Si and an optical gap of 1.5 eV. Electron spin resonance signals were not observed in the films indicating that dangling bonds of Si were terminated by Mo atoms. We fabricated thin-film-transistors using the MoSi10film as a channel material. The electric field effect of the film was clearly observed. This suggests that the density of mid-gap states in the film is low enough for the field effect to occur.
Multifunctional Fiber Solar Cell Based on TiO2 Composite Materials
Authors: Rice Adam , Kim Seong-Ku , Tanaka Zuki , Phuyal Dibya , Yang Xuan , Gu Claire , Pei Qibing , Chen Bin 
Published: September 2011

AbstractThe paper present a multimode optical fiber based solar lighting and photovoltaic multifunctional device. TiO2, PbS and conducting polymer poly(3-hexylthiophene) (P3HT) were coated on the optical core surface as active photovoltaic layers, with ITO and LiF/Al electrodes. The guided sunlight in the multi-moded fiber was totally internal reflected depending on the incident angle and the evanescent light mode from scattered radiation of light was absorbed by the active layer to generate the electric current. The optical-electrical behaviors such as the short circuit current, filling factor, and open circuit voltage were studied. Furthermore, optical loss and the evanescent field at the interface between the optical fiber core and ITO electrode thin layer was discussed in relation to the coupling light from the guiding medium to the devices. Comparison studies of chemical and physical thin film coating on optical fibers are discussed. In particular, we obtained in situ growth of quantum dot, composite electrolyte and plasmonic enhancement on TiO2. We have demonstrated waveguide like fiber device with photo current measurements and I-V characterizations. Furthermore, we have optimized the device transmission of visible light through total internal reflection, and PV conversion of evanescent light absorbed by solar active composite materials fabricated around optical fibers.
Improvement in the Thermoelectric Figure-of-Merit of TAGS-85 by Rare Earth Additions
Authors: Cook B. A. , Harringa J. L. , Besser M. , Venkatasubramanian R. 
Published: September 2011

AbstractTAGS-85 is a well-known thermoelectric material based on germanium monotelluride that exhibits a second-order displacive transformation from a high-temperature cubic to a low-temperature rhombohedral polymorph. Recent efforts to improve the thermoelectric figure-of-merit through the addition of small amounts of the rare earth elements Ce and Yb have demonstrated a 25 percent increase in ZT at 700K in materials obtained by solidification from the melt. Preliminary analysis by x-ray diffraction of the chemically-modified alloy suggests a partial stabilization of the high-temperature cubic polymorph. 125Te NMR studies confirm the incorporation of rare earth cations into the GeTe-based lattice. Solid state synthesis has been successfully applied to the processing of rare-earth-doped TAGS-85 and has resulted in a further increase in ZT beyond the levels initially observed in melt-solidified materials. This is believed to be due to improved homogeneity in the distribution of the lanthanide.
32nm Node Highly Reliable Cu/Low-k Integration Technology with CuMn Alloy Seed
Authors: Yao Shaoning , McGahay Vincent , Angyal Matthew S. , Simon Andrew H. , Lee Tom C. , Christiansen Cathryn , Li Baozhen , Chen Fen , McLaughlin Paul S. , Ogunsola Oluwafemi O. , Grunow Stephan 
Published: September 2011

ABSTRACTThis paper introduces a highly reliable Cu interconnect technology at the 32 nm node with CuMn alloy seed. A CuMn alloy liner seed process combined with a non-gouging liner has been integrated into the minimum-pitch wiring level. Stress migration fails with CuMn seed at plate-below-via structures were shut down by a non-gouging liner process. Integration with gouging liner and non-gouging liner is compared, and results of interaction with CuMn seed are discussed in this paper.
Comparison of TiN thin films grown on SiO2 by reactive dc magnetron sputtering and high power impulse magnetron sputtering
Authors: Magnus F. , Ingason A. S. , Sveinsson O. B. , Olafsson S. , Gudmundsson J. T. 
Published: September 2011

ABSTRACTThin TiN films were grown on SiO2 by a reactive dc magnetron sputtering (dcMS) and high power impulse magnetron sputtering (HiPIMS) at range of temperatures from 45 to 600oC and the properties compared. The HiPIMS process produces denser films at lower growth temperature than does dcMS and the surface is much smoother for films grown by the HiPIMS process. The grain sizes of both orientations are smaller in HiPIMS grown films than in dcMS grown films. The [200] crystallites have smaller size than the [111] crystallites for all growth temperatures. For the dcMS process the grain size increases with increased growth temperature for both the [111] and [200] crystallites. For the HiPIMS process the [200] grain size increases monotonically with increased growth temperature, whereas the size of the [111] oriented grains decreases to a minimum for growth temperature of 400 oC after which it starts to increase with growth temperature.
Microbump Impact on Reliability and Performance in Through-Silicon Via Stacks
Authors: Karmarkar Aditya P. , Xu Xiaopeng 
Published: September 2011

ABSTRACTThe impact of microbump geometry, layout and underfill material properties on the device performance as well as the structural reliability is examined. Numerical simulations reveal that the magnitude of n-type carrier mobility change correlates with the increase in the underfill CTE and modulus as well as microbump pitch and height, but the decrease in the microbump radius. The crack driving force dependence on material property and geometry differs from that of mobility change. While the driving force is crack location dependent, the greater crack driving force corresponds to larger underfill CTE and bump radius, but smaller underfill modulus and microbump pitch.
Low-cost Micro- and Nano-structures in Porous Nanomaterials Realized by Direct Imprinting of Porous Substrates
Authors: Ryckman Judson D. , Liscidini Marco , Sipe J. E. , Weiss S. M. 
Published: September 2011

ABSTRACTWe present a simple one-step methodology for direct structuring of porous nanomaterials on the micro- and nano-scale. Our technique, direct imprinting of porous substrates (DIPS), relies on the application of a pre-patterned and reusable stamp to directly imprint porous substrates. DIPS is performed at room temperature and pressure in less than one minute, and circumvents the conventional requirement for resist processing and etching procedures. It is shown that arbitrarily shaped patterns and structures can be transferred to porous nanomaterials with a very high (sub-100nm) feature resolution that is primarily limited by the pore dimensions of the substrate material. DIPS is demonstrated on a wide variety of porous nanomaterials including metals, semiconductors, and insulators. Furthermore, DIPS can be utilized to locally modify material properties including pore dimensions, density, dielectric function, and surface roughness. Lastly, example structures fabricated by DIPS are discussed for their relevance to important applications ranging from drug delivery and imaging, to solar energy conversion, and biosensing.
Folding Graphene with Swift Heavy Ions
Authors: Akcöltekin Sevilay , Bukowska Hanna , Akcöltekin Ender , Lebius Henning , Schleberger Marika 
Published: September 2011

ABSTRACTSwift heavy ion induced modifications on graphene were investigated by means of atomic force microscopy and Raman spectroscopy. For the experiment graphene was exfoliated onto different substrates (SrTiO3 (100), TiO2(100), Al2O3(1102) and 90 nm SiO2/Si) by the standard technique. After irradiation with heavy ions of 93 MeV kinetic energy and under glancing angles of incidence, characteristic folding structures are observed. The folding patterns on crystalline substrates are generally larger and are created with a higher efficiency than on the amorphous SiO2. This difference is attributed to the relatively large distance between graphene and SiO2 of d ≈ 1 nm.
Improved Hole Collection in Polymer Heterojunction Solar Cells with DNA/Pt-DNA Layers
Authors: Guvenc Ali Bilge , Guo Shirui , Ozkan Cengiz S. , Ozkan Mihrimah 
Published: September 2011

ABSTRACTIn this study, we investigated the effects of DNA/Pt-DNA strands as hole collecting layers in polymer heterojunction solar cells based on ITO/PEDOT:PSS/P3HT:PCBM/LiF/Al structure. We demonstrated that by introducing DNA or Pt-DNA layers between the polymer electrode (PEDOT:PSS) and the active layer (P3HT:PCBM), lead to an improvement in the hole collection efficiency and power conversion efficiency and the absorbance spectra of the devices indicate that Pt particles work as surface plasmons and increase the absorbance of the devices.
Synthesis and Characterization of Rare Earth (Tb3+ and Yb3+) Doped CdS/ZnS Core/Shell Nanocrystals for Enhanced Photovoltaic Efficiency
Authors: Das Sandip , Mandal Krishna C. 
Published: September 2011

ABSTRACTCdS host nanocrystals with 4.2-5.5 nm in diameter have been synthesized from air stable precursors via a synthetic chemical route and doped with rare earth (RE) terbium (Tb3+) and ytterbium (Yb3+) ions. RE3+-doped CdS cores were shelled by ZnS layers of different thicknesses. The resulting core/shell nanocrystals show a complete broadband absorption below 400-460 nm to the deep UV region depending on the size of the cores. RE3+-doped CdS nanocrystals showed a red shift in the emission as observed under irradiation of 302 nm UV light and was confirmed by room temperature photoluminescence (PL) measurements. The nanocrystals were further characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), and energy dispersive x-ray (EDX) analysis. The results show that these RE3+-doped nanocrystals can be used as solar spectral matching downconversion material to enhance photovoltaic efficiency of existing solar cells.
Advanced Optical Modeling of Thin-film Silicon Solar Cells with 1-D Periodic Gratings.
Authors: Solntsev S. , Isabella O. , Caratelli D. , Kyriakou M. , Yarovyi O. , Zeman M. 
Published: September 2011

ABSTRACTDesign of one-dimensional periodic gratings is investigated for enhancing the light absorption in thin-film silicon solar cells due to scattering at rough interfaces that are introduced into solar cells by the gratings. A rigorous full-wave analysis is carried out in order to determine the optical properties of amorphous and microcrystalline silicon solar cells in PIN and NIP configurations, respectively. Optimal geometrical parameters of 1-D gratings for maximizing photocurrent density in thin-film silicon solar cells are determined.
The Dye Sensitized Solar Cell Stability and Performance Study Using Different Electrolytes
Authors: Radhakrishnan Sailaja , Munukutla Lakshmi V. , Htun Aung , Kannan Arunachalanadar M. 
Published: September 2011

ABSTRACTThe overarching goal of Dye Sensitized Solar Cells (DSSCs) is to improve photovoltaic performance and their long-term stability for use in practical applications because of their simple fabrication technology at a reasonable cost. The focus of this paper is to achieve cell stability and also to improve solar energy conversion efficiency experimenting with different electrolytes. The electrolyte’s role is critical to sustain the DSS cell performance over time to instill cell stability. Four different electrolytes, Iodolyte R-150, AN-50, PN-50 and MPN-100, are experimented in this work for fabricating the dye-sensitized solar cells for studying both the stability and efficiency of the DSSCs.The electrolyte selection was made using the following key electrolyte parameters; lower viscosity for easier injection into the cell, lower vapor pressure and higher boiling point to minimize electrolyte evaporation, wide redox window to generate sufficient donating electrons to the dye, lower cost and non-toxicity. Electrolytes with higher concentration of Iodolyte were chosen for this study to widen redox potential window. These are Iodide based redox electrolytes and are made with 100 mM of tri-iodide in 3-methoxypropionitrile. The results of this investigation revealed that the cell with Iodolyte R-150 electrolyte achieved improved performance having an efficiency of 10.2% when compared to the reference cell efficiency of 8.4% with Iodolyte R-50. These cells were stabilized over a time of 4 weeks. The fill factor of the cell changed about 10% and the internal resistance decreased from 6.7 to 4.3 Ω. The results of this experiment demonstrated reduced internal resistance, and improved fill factor contributed to higher cell efficiency and stability. The results of the work presented in this paper support the argument that electrolytes with higher Iodolyte concentration can enhance the cell efficiency and stability along with scaling down of the cell size.
Mesophase ordering and structuring of porous titanium dioxide with high surface area and strong light harvesting matrix for dye-sensitized solar cell
Authors: Ho Ghim W. , Agarwala Shweta , Kevin Moe 
Published: September 2011

ABSTRACTDye sensitized solar cells (DSSC) are attractive because they hold promise for devices that are easy to fabricate and inexpensive. In the present work, highly crystalline mesoporous TiO2 has been synthesized by evaporation induced self assembly (EISA) method using triblock copolymer Pluronic P123 as the organic template. The synthesized TiO2 is anatase in nature with a pore size of 10-15 nm. DSSC made from mesoporous TiO2 demonstrated solar conversion efficiency of ∼7%. This comes from the benefits of increased surface roughness, surface area and uniform porosity. In addition, well ordered and crystalline pores provided good sunlight absorption and low recombination path for charge carriers. To further enhance the efficiency of the DSSCs, light scattering centers were introduced in the mesoporous TiO2 film. Nanoparticles light scatterers are introduced to scatter the incoming light and hence to increase the light harvesting capability of the device. A 26 % increase in DSSC efficiency was observed with the implementation of scattering centers.
Structure and Stability of Olivine Phase FePO4
Authors: Nolis Gene M. , Chernova Natalya A. , Upreti Shailesh , Whittingham M. Stanley 
Published: September 2011

ABSTRACTLiFePO4 has shown considerable promise as a cathode material in Li-ion batteries due to its stability, low toxicity and high cyclability. However, the data on thermodynamic stability of olivine phase FePO4 (o-FePO4), the delithiated form of o-LiFePO4, remains scarce and contradictory. In this work, o-FePO4 was synthesized by chemical delithiation of o-LiFePO4 and characterized structurally and thermally. X-ray diffraction and absorption data indicate pure olivine phase, but with residual amount of Fe2+, most likely due to incomplete delithiation. Differential scanning calorimetry and thermal gravimetric analysis reveal that o-LixFePO4 decomposes exothermally above 550 °C with about 9% weight loss, the products being trigonal phase FePO4, Fe7(PO4)6, and LiPO3.