bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Impact of Material Nanotopography on Cell Functions and Filopodia Extension: Experiments and Modeling
Authors: Yang Lei , Li Qunyang , Chinthapenta Viswanath , Liang Amy , Sheldon Brian W , Webster Thomas J 
Published: August 2010

AbstractExploring the cell-material interface is an emerging area of great interest in biomaterial science. Specifically, creating nanostructured surface interfaces to improve biomaterial efficacy is one of these key focus topics. As an example, an increasing number of studies have demonstrated the positive role nanostructured surfaces can have towards promoting various cell functions. However, the relevant mechanism behind this improvement in biological interactions at the cell-implant interface is not well understood. For this reason, here, osteoblast (bone forming cells) and fibroblast (fibrous, soft tissue forming cells) functions (including adhesion and proliferation) on two carefully fabricated diamond films with dramatically different topographies were tested. The results revealed greater cell responses on nanocrystalline diamond (grain sizes <100nm) compared to submicron crystalline diamond (grain sizes 200˜1000nm). In order to understand this positive impact of diamond nanotopography on cell responses, fibronectin absorption and subsequent cell spreading were studied. More importantly, cell filopodia extensions were also studied through computational mechanical modeling. A deflection-diffusion model of cell filopodia extension was established and clearly suggested that increasing the lateral dimension or height of nanometer surface features could inhibit cell filopodia extension and decrease cell spreading. Both the experiments and modeling from this study indicated that a nanometer surface topography can enhance cell responses to promote implant efficacy.
Fluorescence Measurements and AFM Imaging of Bacteriorhodopsin Coupled with CdSe Quantum Dots for Optoelectronic Applications
Authors: Bouchonville Nicolas , Molinari Michael , Sukhanova Alyona , Troyon Michel , Nabiev Igor 
Published: August 2010

AbstractA new nanohybrid material with a potential impact on energy transfer processes in biomolecules was developed by coupling colloidal fluorescent semiconductor CdSe/ZnS quantum dots (QDs) with a photochromic membrane protein, the bacteriorhodopsin (bR). The interactions between the nanocrystals and the proteins were studied by fluorescence spectroscopy and atomic force microscopy (AFM) measurements. A quenching in the photoluminescence (PL) of QDs emitting in the range of the bR absorption suggests a fluorescence resonance energy transfer effect from QDs (donors) to bR (acceptor). As the quenching evolution is different with the surface charges of the QDs, it suggests that the QDs interact with bR through electrostatic interactions. The AFM images of bR coupled with QDs capped with positive or negative surface groups confirm that the electrostatic interactions between QDs and bR play a dominant role in the way they are coupling together. The observed interactions between QDs and bR can provide the basis for the development of novel functional materials with unique photonic properties and having applications in the all-optical switching, photovoltaics and data storage.
On Mechanics of Connective Tissue: Assessing the Electrostatic Contribution to Corneal Stroma Elasticity
Authors: Hatami-Marbini Hamed , Pinsky Peter M. 
Published: August 2010

AbstractThe extracellular matrix plays a crucial role in defining the mechanical properties of connective tissues like cornea, heart, tendon, bone and cartilage among many others. The unique properties of these collagenous tissues arise because of both the hierarchal structure of collagens and the presence of negatively charged proteoglycans (PGs) which hold collagen fibers together. Here, in an effort to understand the mechanics of these structures, using the nonlinear Poison-Boltzmann (PB) equation, we study the electrostatic contribution to the elasticity of corneal stroma due to the presence of negatively charged PG glycosminoglycans (GAGs). Since collagens and GAGs have a regular hexagonal arrangement inside the corneal stroma, a triangular unit cell is chosen. The finite element method is used to solve the PB equation inside this domain and to obtain the electric potential and ionic distributions. Having the ion and potential distributions throughout the unit cell, the electrostatic free energy is computed and the tissue elasticity is calculated using the energy method. It is shown that as the ionic bath concentration increases; the electrostatic contribution to tissue elasticity is reduced.
Hierarchical Biomaterials Mechanics of Bone and Bone Substitutes
Authors: Hellmich Christian , Fritsch Andreas , Dormieux Luc 
Published: August 2010

AbstractBiomimetics deals with the application of nature-made ‘design solutions’ to the realm of engineering. In the quest to understand mechanical implications of structural hierarchies found in biological materials, multiscale mechanics may hold the key to understand ‘building plans’ inherent to entire material classes, here bone and bone replacement materials. Analyzing a multitude of biophysical hierarchical and biomechanical experiments through homogenization theories for upscaling stiffness and strength properties, reveals the following design principles: The elementary component ‘collagen’ induces, right at the nanolevel, the mechanical anisotropy of bone materials, which is amplified by fibrillar collagen-based structures at the 100 nm-scale, and by pores in the micrometer-to-millimeter regime. Hydroxyapatite minerals are poorly organized, and provide stiffness and strength in a quasi-brittle manner. Water layers between hydroxyapatite crystals govern the inelastic behavior of the nano-composite, unless the ‘collagen reinforcement’ breaks. Bone replacement materials should mimic these ‘microstructural mechanics’-features as closely as possible.
Electrically Modulated Drug Delivery using Nanoporous Electrodes
Authors: Robinson David B. , Gittard Shaun D. , Wu C.-A. Max , Ha Cindy M. , Narayan Roger J. 
Published: August 2010

AbstractNanoporous electrodes, such as those made from carbon or gold, can capture and release ionic analytes at concentrations near 1 mole per liter of pore volume through capacitive charging or electrochemically reversible adsorption. In vitro studies suggest that this phenomenon can be the basis for a noninvasive, precise, and programmable drug delivery method. It would eliminate the need for bulk fluid delivery to target tissue and require only a thin electrical connection, minimizing pain and tissue disruption. We have designed effective gold electrode assemblies and observed the depletion and release phenomena using electrochemical methods and charged dyes.
Synthesis and Characterization of Poly(2,5-benzimidazole) (ABPBI) Grafted Carbon Nanotubes
Authors: Kang Ji-Ye , Eo Su-Mi , Tan Loon-Seng , Baek Jong-Beom 
Published: August 2010

AbstractSingle-walled carbon nanotube (SWCNT) and multi-walled carbon nanotube (MWCNT) were functionalized with 3,4-diaminobenzoic acid via “direct” Friedel-Crafts acylation reaction in PPA/P2O5 to afford ortho-diamino-functionalized SWCNT (DIF-SWCNT) and MWCNT (DIF-MWCNT). The resultant DIF-SWCNT and DIF-MWCNT showed improved solubility and dispersibility. To improve interfacial adhesion between CNT and polymer matrix, the grafting of ABPBI onto the surface of DIF-SWCNT (10 wt%) or DIF-MWCNT (10 wt%) was conducted by simple in-situ polymerization of AB monomer, 3,4-diaminobenzoic acid dihydrochloride, in PPA. The resultant ABPBI-g-MWCNT and ABPBI-g-SWCNT showed improved the mechanical and electrical properties.
Electrospun Composite Nanofibers for Sensor Applications
Authors: Han Li , Andrady Anthony , Guzan Kim , Ensor David S 
Published: August 2010

AbstractElectrospun polymer nanofiber materials have attracted tremendous interest in sensor applications as their effective sensing surface area dramatically increases with decreasing fiber diameter. The highly tunable polymer composite chemistry and surface functionality of the nanofiber material provides a wide platform for exploring different applications, such as filtration media, sound isolation materials, and sensor components. This paper presents a nanofiber sensor platform device composed of electrospun polymer/carbon composite nanofibers combined with electrodes directly printed onto the surface of the electrospun fiber mat. This structure forms an integrated sensor system for detecting various chemical vapors including volatile organic compounds (VOCs) and oxidative gases. In this sensor, the composite polymer nanofibers form a chemo-resistor sensing material, and the conductivity of these composite sensing materials varies with chemical vapor exposure. The sensor performance exhibits very stable baselines with dramatically reduced noise levels compared to conventional interdigitated electrodes. Furthermore, the sensor response to different vapors shows a linear relationship between conductivity change and vapor concentration in the range of ppb – ppm for some analytes, including methanol, chloroform and ozone. The sensitivity and selectivity of these sensors to different vapor analytes will also be discussed.
Functional Controlled Release Systems Triggered by Photothermal Effect of Gold Nanorods
Authors: Yamashita Shuji , Fukushima Hiromitsu , Niidome Yasuro , Mori Takeshi , Katayama Yoshiki , Niidome Takuro 
Published: August 2010

AbstractGold nanorods, rod-shaped gold nanoparticles, have transverse and longitudinal surface plasmon (SP) bands at visible and near-infrared (IR) regions, respectively. Since the absorbed light energy is converted into heat, photothermal effect of gold nanorods can be triggered without damaging the tissues in the path of near-IR laser light. In this study, we tried to construct controlled release system of functional molecules from surface of gold nanorods mediated by the photothermal effect. First, we evaluated controlled release of poly(ethyleneglycol) (PEG) chains from PEG-modified gold nanorods (PEG-NR). Next, we employed double stranded oligonucleotide as a thermo-responsive dissociating group (DNA-NR). Finally, we evaluated photothermal release of PEG chains mediated retro-Diels-Alder reaction (PEG-DA-NR). For construction of controlled release system of functional molecules, these studies will provide important information about the photothermal reactions of surface molecules on the gold nanorods triggered by near-IR light irradiation.
UV-embossed textured back reflector structures for thin film silicon solar cells
Authors: Escarre Jordi , Söderström Karin , Cubero Oscar , Haug Franz-Josef , Ballif Christophe 
Published: August 2010

AbstractIn this work, we study the replication of nanotextures used in thin film silicon solar cells to enhance light trapping onto inexpensive substrates such as glass or polyethylene naphtalate (PEN). Morphological analysis was carried out to asses the quality of these replicas. Moreover, single and tandem a-Si:H solar cells were deposited on top of the master and replica structures to verify their suitability to be used as substrates for solar cells in n-i-p configuration. We find stabilized efficiencies around 8% which are similar for tandem cells on masters and PEN replicas.
The Study of Optical and Electrical Properties of a-SiC:H for Multi-junction Si Thin Film Solar Cell
Authors: Shim Jenny H. , Yoon W.K. , Hwang S.T. , Ahn S.W. , Lee H.M. 
Published: August 2010

AbstractStudies have shown that wide bandgap material is required for high efficiency multi-junction solar cell applications. Here, we address proper deposition condition for high quality a-SiC:H films. In high power high pressure regime, we observed that the defect density get much lowered to the similar defect level of a-Si:H film with high H2 dilution. Single junction solar cells fabricated with the optimized condition show high open circuit voltage and low LID effect. The degradation after the LID test was only 13 % reduction of the efficiency indicating that a-SiC:H could be promising material for multi-junction solar cells.
Micro-Channel Plate Detectors Based on Hydrogenated Amorphous Silicon
Authors: Wyrsch Nicolas , Powolny François , Despeisse Matthieu , Dunand Sylvain , Jarron Pierre , Ballif Christophe 
Published: August 2010

AbstractA new type of micro-channel plate detector based on hydrogenated amorphous silicon is proposed which overcomes the fabrication and performance issues of glass or bulk silicon ones. This new type of detectors consists in 80-100 μm thick layers of amorphous silicon which are micro-machined by deep reactive ion etching to form the channels. This paper focuses on the structure and fabrication process and presents first results obtained with test devices on electron detection which demonstrate amplification effects. Fabrication and performance issues are also discussed.
Optical Absorption in Co-Deposited Mixed-Phase Hydrogenated Amorphous/Nanocrystalline Silicon Thin Films
Authors: Wienkes Lee , Besaw Aaron , Anderson Curtis , Bobela David , Stradins Paul , Kortshagen Uwe , Kakalios James 
Published: August 2010

AbstractThe conductivity of amorphous/nanocrystalline hydrogenated silicon thin films (a/nc-Si:H) deposited in a dual chamber co-deposition system exhibits a non-monotonic dependence on the nanocrystal concentration. Optical absorption measurements derived from the constant photocurrent method (CPM) and preliminary electron spin resonance (ESR) data for similarly prepared materials are reported. The optical absorption spectra, in particular the subgap absorption, are found to be independent of nanocrystalline density for relatively small crystal fractions (< 4%). For films with a higher crystalline content, the absorption spectra indicate broader Urbach slopes and higher midgap absorption. The ESR spectra show an approximately constant defect density across all of the films. These data are interpreted in terms of a model involving electron donation from the nanocrystals into the amorphous material.
The Staebler-Wronski Effect: New Physical Approaches and Insights as a Route to Reveal its Origin
Authors: Smets Arno H.M. , Wronski Chris R. , Zeman Miro , van de Sanden M. 
Published: August 2010

AbstractIn the recent years more and more theoretical and experimental evidence have been found that the hydrogen bonded to silicon in dense hydrogenated amorphous silicon (a-Si:H) predominantly resides in hydrogenated divacancies. In this contribution we will philosophize about the option that the small fraction of divacancies, missing at least one of its bonded hydrogen, may correspond to some of the native and metastable defect states of a-Si:H. We will discuss that such defect entities are an interesting basis for new and alternative views on the origin of the SWE.
Accuracy of the Fatigue Lifetime of Polysilicon Predicted from its Strength Distribution
Authors: Vu Le Huy , Gaspar Joao , Paul Oliver , Kamiya Shoji 
Published: August 2010

AbstractThis paper discusses the accuracy of the distribution of the fatigue lifetime of polysilicon thin films predicted from their strength distribution. On the basis of the authors' previous studies, where the fatigue process determining the lifetime was formulated using the well-known fatigue crack extension Paris' law, prediction error ranges for polysilicon specimens with different levels of strength are determined. The errors of the predicted fatigue lifetime in the logarithmic scale, defined as △logN= |log10Nexp-log10Npred| whereNexpandNpredwere the experimental and predicted number of cycle, were found to be less than 1 in the range of the cumulative fracture probability F between 0.1 and 0.9. Therefore, based on the measured Paris' law parameters of polysilicon, the fatigue lifetimes of different polysilicon thin film structures can be predicted from their strength distributions with errors of roughly 10% in the logarithmic scale, which was average of percentages of △logNto log10Nof experimental data.
High Efficiency Hydrogenated Nanocrystalline Silicon Solar Cells Deposited at High Rates
Authors: Yue Guozhen , Sivec Laura , Yan Baojie , Yang Jeff , Guha Subhendu 
Published: August 2010

AbstractWe report recent progress on hydrogenated nanocrystalline silicon (nc-Si:H) solar cells prepared at different deposition rates. The nc-Si:H intrinsic layer was deposited, using a modified very high frequency (MVHF) glow discharge technique, on Ag/ZnO back reflectors (BRs). The nc-Si:H material quality, especially the evolution of the nanocrystallites, was optimized using hydrogen dilution profiling. First, an initial active-area efficiency of 10.2% was achieved in a nc-Si:H single-junction cell deposited at ~5 Å/s. Using the improved nc-Si:H cell, we obtained 14.5% initial and 13.5% stable active-area efficiencies in an a-Si:H/nc-Si:H/nc-Si:H triple-junction structure. Second, we achieved a stabilized total-area efficiency of 12.5% using the same triple-junction structure but with nc-Si:H deposited at ~10 Å/s; the efficiency was measured at the National Renewable Energy Laboratory (NREL). Third, we developed a recipe using a shorter deposition time and obtained initial 13.0% and stable 12.7% active-area efficiencies for the same triple-junction design.
Intrinsic Surface Defects on 4H SiC Substrates
Authors: Zvanut Mary Ellen , Thomas Sarah , Dashdorj Jamiyanaa 
Published: August 2010

AbstractWe have investigated a point defect, common to all SiC substrates, that is thought to be a broken carbon bond. Electron paramagnetic resonance spectroscopy performed in combination with three different etching methods using p-type, n-type, and semi-insulating substrates demonstrate that the center lies near the surface of a wafer. The results suggest that on the order of 1013 cm-2 defects are removed within the first micron of the surface of a wafer.
Single Shockley Faults Evolution Under UV Optical Pumping
Authors: Canino Andrea , Camarda Massimo , La Magna Antonino , La Via Francesco 
Published: August 2010

AbstractSingle Shockley faults (SSF) have been studied in 4H-SiC epitaxial layers by using a spatial resolved micro-photoluminescence technique. In particular the effect of the UV pumping laser has been investigated. Samples have been irradiated at different power densities in order to find a threshold for the growth of the SSF defects. A low power density (115 W/cm2) exposition at 325 nm does not affect the structural properties of the epitaxial layers. We observed a growth of this defect through the epitaxial layers when the power density is increased over the value of 115 W/cm2.
Afterglow Chemical Processing for Oxide Growth on Silicon Carbide
Authors: Hoff Andrew M , Short Eugene , Thomas Helen B , Oborina Elena I 
Published: August 2010

AbstractThe unique capabilities and characteristics provided by afterglow or remote plasma chemical oxide growth processing of silicon carbide are reviewed. Such processing provides for thermal growth of oxide films at temperatures far below those employed by conventional atmospheric processing methods. Overshadowing this growth capability is the ability to create chemistries, sequential procedures, and specific process environments to address material and defect issues in a manner not possible under conventional atmospheric conditions. The details and outcomes of multi-step afterglow oxidation processing of SiC will be discussed. An example sequence might include; 1) surface conditioning, 2) film growth at 850C and 1 Torr total pressure, and 3) reduced pressure unexcited media post-growth treatments. Surface conditioning impacts the thickness uniformity of the final oxide film and the oxidation rate. The film growth interval produces a nominal 500Å of oxide film in 90 minutes at 850C, a temperature that would not produce any significant oxide film at atmospheric pressure. And the post-growth processing improves the performance of the dielectric film. Using in-line corona-Kelvin metrology the electrical characteristics stemming from these processes have been determined. Electrical effective oxide thickness results were used to assess thickness uniformity and to estimate process rate constants for comparison to other process methods. Fowler-Nordheim, F-N, characteristics determined with the same metrology demonstrate that afterglow, AG, oxides require higher field levels to produce the same F-N current as thermal oxides and that AG films are less susceptible to stress fluence. Process extensions from these and other results are discussed and related to chemical, physical, and electrical film outcomes and potential pathways to improve control over dielectric SiC structures.
Reducing Time Dependent Line to Line Leakage Following Post CMP Clean
Authors: Canaperi Donald F , Papa Rao Satyavolu , Hurd Trace Q. , Medd Steven B , Levin T. M. , Penny Christopher J , Chen James H.-C. , Smalley Matthew D 
Published: August 2010

AbstractA systematic approach was taken to identify methods to prevent post CMP corrosion of copper in 22nm interconnect structures. Line to line current leakage measurements (at various times post CMP) were used as a means to quantify the extent and time-dependence of copper corrosion. Interruption of the corrosion mechanism by the use of passivating agents in post-CMP clean chemistries is explored. A broad-based screening was conducted to identify aqueous formulations of passivating agents for protection of copper which do not have deleterious effects on line resistance and overall defectivity. A formulation was identified which was effective in preventing corrosion when applied during post CMP brush clean.
Retaining Ring Design Impact on CMP Process Stability and Optimization
Authors: Smith Joseph , Wargo Christopher , Kakireddy Raghava , Singh Rakesh , Galpin Andrew , Philipossian Ara , Wei Xiaomin , Bennedine Karim , Reversat Claude , Chabourel Alain 
Published: August 2010

AbstractThe focus of this work is wafer retaining rings and their impact on chemical mechanical planarization (CMP) process stability, yield, and overall cost of ownership (CoO). The study looks at various CMP retaining ring materials and processing methods. Tribological investigations as well as wafer processing are critical to understand the retaining ring and polishing pad environment. Interactions at the ring/pad interface have a major effect on the planarization and defectivity of a polished wafer. Shear and normal forces at this interface, as well as temperature and lubrication regimes, were monitored to establish an empirical model. All process conditions equal, the material properties of retaining rings govern the coefficient of friction (COF) in the ring and pad contact area. Present study demonstrates a lower COF to be an indicator of extended ring lifetime, decreasing WTWNU and removal rate (RR) variation. The study correlates the findings on wafer level data from high volume manufacturing fabs with empirical data generated using applications lab tribological equipment to understand the on-wafer performance as a function of retaining ring material. The study's further aim is to understand for specific applications, the material interactions on-wafer using various retaining ring materials. CMP process optimization can be attained with a better understanding of retaining ring design and material characteristics, as well as polishing head and slurry parameters.