bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pattern Formation During Nanowear of Gold Films
Authors: Pendergast Megan E. , Volinsky Alex A. , Pang Xiaolu 
Published: April 2011

ABSTRACTThe effects of water on the wear resistance of 3 μm thick sputtered gold film on silicon substrate using contact AFM and a scanning nanoindenter were investigated. In performing wear tests on gold samples in the presence of water, a significant increase in depth of the wear area was observed compared to the same tests performed in the ambient atmosphere (∼55% humidity). These results were obtained using Hysitron Triboindenter on areas of 10×10 μm2 and an Atomic Force Microscope on areas of 1×1 μm2. Nanowear tests were preformed using silicon nitride cantilevers on the AFM and diamond Berkovich or blunt conical tips on the Hysitron. Normal loads used were 2000 μN and 10 μN, respectively. Tests performed in the ambient atmosphere resulted in a slightly reduced surface roughness, while a much higher wear rate was observed in the wear tests performed in water. Additionally, gold surface ripples formed under certain scanning conditions, in water for the Hysitron Triboindenter and in ambient atmosphere for the AFM. Nanoscale stick slip is being investigated as a possible explanation to the rippling phenomenon, and single scan line tests provide valuable information about the mechanisms and progression of the nanoscale wear.
A General Nonlithographic Method for Producing Nanodots by RIE Etching
Authors: Leach Jacob H. , Morkoç Hadis 
Published: April 2011

ABSTRACTIn this work, thin layers of poly(methyl methacrylate) (PMMA) on Ni on silicon <111> substrates were etched almost completely away by oxygen RIE, leaving only the topmost portion of the roughness, generating nanodots of PMMA approximately 30-40nm or smaller in size. After sufficiently hard baking the samples to promote PMMA adhesion to the Ni and to increase the robustness of the PMMA, the nanodots were used as a mask to etch the thin Ni films, thus generating Ni nanodots on Si. The Ni nanodots were then used as a reactive ion (RIE) etch mask, thereby generating Si nanopillars. With further understanding of the mechanism of the generation of the roughness of the PMMA, or with the use of other polymeric materials suitable as wet etching masks, nanodots of varying size should be attainable. This method represents a very simple, low cost, scalable, and general technique to produce nanodots of various thin metals on various substrates.
Raman Spectrum of Graphene Coated Nano-Holes
Authors: Banerjee Amrita , Li Ruiqiong , Grebel Haim 
Published: April 2011

ABSTRACTIt was assumed in the past that aluminum is not a platform of choice for surface enhanced Raman scattering (SERS) experiments: this was in spite of its large negative permittivity value, larger than gold or silver at optical wavelength. It was also assumed that any oxide on top of metallic platform significantly hinders SERS signals. In addition, graphene has not been studied on perforated substrates. Here we use periodically perforated and oxidized aluminum surfaces to examine electrical and optical properties of multi layered graphene. Linear and nonlinear optical methods were used to characterize single and multi layered structures.
Oriented Film Growth of Organic Semiconductor Sexithiophene on Artificial Periodic Grooves and Electrical Conduction Properties of the Films
Authors: Ikeda Susumu , Wada Yasuo , Inaba Katsuhiko , Terashima Kazuo , Shimada Toshihiro , Saiki Koichiro 
Published: April 2011

ABSTRACTFilm growth of organic semiconductor α-sexithiophene (6T) was studied using substrates with artificial periodic grooves. The grooves were fabricated on thermally oxidized silicon substrates by electron beam lithography. Based on the orientation analysis by atomic force microscopy and grazing-incidence x-ray diffraction, part of the 6T grains grew having the in-plane orientational relationship with the artificial grooves. This phenomenon corresponds to “ggraphoepitaxy” which has been well known in inorganic materials research field. As well as the in-plane preferred orientation, one-dimensional structure consisting of connected 6T grains was observed. The electrical conduction properties of the films were also evaluated.
Geometric confinement governs the rupture strength of H-bond assemblies at a critical length scale
Authors: Keten Sinan , Buehler Markus J. 
Published: April 2011

ABSTRACTUsing theoretical considerations and MD simulation techniques, we show that the rupture strength of H-bond assemblies is governed by geometric confinement effects, suggesting that clusters of at most 3-4 H-bonds break concurrently, even under uniform shear loading of a much larger number of H-bonds. This universally valid result leads to an intrinsic strength limitation that suggests that shorter strands with less H-bonds achieve the highest shear strength. Our finding explains how the intrinsic strength limitation of H-bonds is overcome by the formation of a nanocomposite structure of H-bond clusters, thereby enabling the formation larger, much stronger beta-sheet structures. Our results explain recent experimental proteomics data, suggesting a correlation between the shear strength and the prevalence of beta-strand lengths in biology.
Protein Fingerprinting Using Flat-Surface Electrophoresis
Authors: Ramasamy Perumal Radha , Elmaghrabi Raafat , Halada Gary , Rafailovich Miriam 
Published: April 2011

ABSTRACTDevelopments in the field of proteomics are highly encouraging for medical researchers. While gel electrophoresis offers a successful means for protein recognition, it requires the use of a relatively large system and a rather long period of time. Here, a protocol is developed for electrophoresis of proteins using flat surfaces based on the principles of electrophoresis of DNA on flat surfaces. By further adapting this system, it is hoped to create a portable device for protein electrophoresis. Droplets of fluorescently tagged proteins such as albumin, casein, poly-L-lysine and their mixtures were placed on glass surfaces in an electrophoretic cell and allowed to dry. TBE buffer was added to the cell and the migration of the salt complexes was monitored using confocal microscopy. We show that different protein - salt complexes have different mobilities on a flat surface. The shape and size distributions of the protein-salt complexes and their mixtures on surfaces were also studied using atomic force microscopy and were found to be dependent upon the proteins. It is observed that the native charge of the proteins play a dominant role in the migration of the protein-salt complexes in the electrophoretic cell. From the morphology of the protein droplets it is observed that large aggregates are formed when oppositely charged proteins are mixed. Light scattering measurements and zeta potential measurements confirm the difference in the size and shape of the aggregates in solution leading to different mobilities of the protein-salt aggregates during electrophoresis.
Asymptotic Strength Limit of Hydrogen Bond Assemblies in Proteins at Vanishing Pulling Rates
Authors: Keten Sinan , Buehler Markus J. 
Published: April 2011

ABSTRACTExperimental and computational studies on mechanical unfolding of proteins suggest that rupture forces approach a limiting value of a few hundred pN at vanishing pulling velocities. We develop a fracture mechanics based theoretical framework that considers the free energy competition between entropic elasticity of polypeptide chains and rupture of peptide hydrogen bonds, which we use here to provide an explanation for the intrinsic strength limit of proteins. Our analysis predicts that individual protein domains stabilized by hydrogen bonds can not exhibit rupture forces larger than approximately ≈200 pN, regardless of the presence of a large number of hydrogen bonds. This result explains a wide range of experimental and computational observations.
The Detection and Characterization of Nanoparticulate Heavy Metals in Epithelial Tissues in Patients with Nephrogenic Fibrosing Dermopathy
Authors: Ayers Reed , High Whitney , Chandler John , Ranville Jim 
Published: April 2011

ABSTRACTCertain diseases have been associated with the administration of heavy elements as contrast agents to patients undergoing medical imaging procedures. Recently, the presence of gadolinium (Gd) administered as a paramagnetic contrast agent for MRI contrast studies was associated with the incidence of Nephrogenic Fibrosing Dermopathy (NFD), also called Nephrogenic Systemic Fibrosis (NSF). To determine specific causation, Gd and other metallic nanoparticles in various tissues must be detected directly and characterized in-situ. This is done to develop specific mechanisms for the chemical modification of the metal elements as the result of a biologic response. Fixed biopsies embedded in paraffin were sectioned at 3-5 μm thick, deparaffinized by hand (xylene and 100% ethyl alcohol), placed on carbon planchettes, and allowed to air dry. Deparaffinized tissues were examined using a field emission SEM (FE-SEM) to directly detect and image the presence of Gd as well as other metals. Backscatter electron (BSE) imaging (20kV) was used to discern metal particles within tissues. Energy dispersive spectroscopy (EDS) (15kV) was used to verify the specific elements present. This allowed for the spatial characterization of the nanoparticles within the tissues but due to the physical limitations of SEM/EDS, quantification of the amount of metal was not possible. Mass concentration of the metal elements was determined using inductively coupled plasma mass spectrometry (ICP-MS) on digested tissues. Thick tissue sections, >30 μm, were used for ICP-MS to provide enough mass for detection. These sections were taken from the histology blocks adjacent to the thin sections used in the FE-SEM. Gadolinium was detected in skin, heart, lung and liver tissues. The highest concentrations were found in heart and skin; both had average tissue concentrations greater than 200μg/g (100-450μg/g range). In skin, gadolinium nano-particulates were readily seen near cell body locations in autopsy samples and within the cells in biopsy samples. The cells where gadolinium was most easily found were along blood vessels. In the cells the agglomerates appear granular with a size of less than 100 nm. They are diffused throughout the cell but as of this time not associated with any particular cell structure. Subsequent work using TEM will examine that aspect as well as the specific ultrastructure and chemistry of the nanoparticles. In this investigation, gadolinium was detected in the tissues of a number of patients with NSF. Although neither dispositive of a pathophysiologic mechanism, nor proof of causation, the detection and quantification of gadolinium within tissues of NSF patients is supportive of the epidemiologic association between exposure to gadolinium containing contrast material and development of the disease.
Device Structure for enhancement of DNA hybridization kinetics by Electrodeless Dielectrophoresis
Authors: Swami Nathan , Chou Chia-fu , Camacho-Alanis Fernanda 
Published: April 2011

ABSTRACTSignal transduction for purposes of biomolecular sensing can be enhanced through miniaturization (nanoscale sensors such as nanowires, cantilevers, etc), but this may impose insurmountable limitations on transport of analyte molecules to the surface. In order to improve biomolecular detection sensitivity, this study aims to develop electrodeless dielectrophoresis (EDEP) methods for the selective transport and trapping of analytes in close proximity to the sensor surface. A device design based on microscale dielectric constrictions of the fluidic channel and nanoscale metal electrode edges was used to locally enhance electric field gradients and trap biomolecules. The resulting electric field focusing effect was enhanced as a result of miniaturization and an instantaneous ten-fold EDEP preconcentration was obtained in high-salt buffers (50 mM NaCl) that enabled an equivalent improvement in DNA hybridization kinetics.
Carbon Nanospheres for Biomedical Applications
Authors: Styres Courtney , Stanishevskaya Inessa , Nasti Tahseen , Yusuf Nabiha , Everts Maaike , Yockell-Lelievre Helene , Stanishevsky Andrei 
Published: April 2011

ABSTRACTCarbon nanostructures, e.g., nanotubes, fullerenes, carbon blacks, etc., are being extensively explored for numerous biomedical applications. The most of such studies, however, deal with carbon nanotubes, and comparatively less is known on the biomedical potential of other nanosize carbon particles. In the present work, carbon and metal/carbon core/shell spherical nanoparticles have been prepared using the decomposition of monosaccharide-based compositions under hydrothermal conditions with or without the presence of metal seed particles. The effects of different process conditions on the particle size, structure, and composition have been examined using TEM, XRD, UV-Vis, FTIR and Raman spectroscopies. The nearly perfect spherical particles with the dimensions in the range of 20 – 100 nm have been obtained depending on the process parameters such as precursor concentration, presence of seed particles and polymeric additives, process temperature and time. The particles prepared with 5 – 20 nm gold seeds clearly showed the core/shell structure with the thickness of carbon shell in the range of 10 – 50 nm. The FTIR experiments have indicated a strong effect of the processing conditions on the chemical activity of nanoparticle surfaces in the attachment of the additional surface functional groups and organic molecules. It has been found that the both hydrothermally prepared carbon and metal/carbon core/shell nanoparticles possess very good dispersibility and stability in the both water and simulated body fluids in the most of experiments. The particles have been successfully functionalized with several molecules such as polyethyleneglucol and biotin. Selected samples of well-dispersed carbon nanospheres with different concentrations have been tested for their interaction with several cultured cell lines including epidermal keratinocytes, fibroblasts, and dog macrophages.
Detection of Viral Proteins using Human Receptor Functionalized Carbon Nanotubes
Authors: Chen Michelle , Khamis S.M. , Datta S.S. , Zhang Y.-B , Kanungo M. , Ho A.J. , Freimuth P. , van der Lelie Daniel , Johnson A.T. , Misewich J.A. , Wong S.S. 
Published: April 2011

ABSTRACTWe present proof-of-concept experiments for developing a highly-sensitive and fast-response miniaturized single-walled carbon nanotube field-effect transistor (SWNT-FET) biosensor for electrically detecting adenovirus using ligand-receptor-protein specificity. SWNTs are mildly oxidized to form carboxylic groups on the surfaces without compromising the electronic integrity of the nanotubes. Then the human coxsackievirus and adenovirus receptor (CAR) is covalently functionalized onto the nanotube surface via diimide-activated amidation process. Upon exposure of the device to adenovirus protein, Ad12 Knob (Knob), specific binding of Knob to CAR decreases the current that flows through the SWNT-FET device. For control experiment, the CAR-SWNT device is exposed to YieF, which is a virus protein that does not bind specifically to CAR, and no current change is observed. The biological activity of the CAR and Knob proteins that are immobilized on SWNTs has been confirmed by previous fluorescence studies [1]. AFM analysis is done to show height increase of a few nanometers at specific spots where the CAR-Knob complex are covalently linked to the nanotube surface. Therefore, our results show that the human receptor protein CAR does immobilize on SWNT surface while fully retains its biological activity. Moreover, the specific binding of CAR to its complementary adenovirus Knob can be electrically detected using individual SWNT-FET devices. These findings suggest that CAR-functionalized SWNT-FETs can ably serve as biosensors for detection of environmental adenoviruses.
Crystallinity Uniformity of Microcrystalline Silicon Thin Films Deposited in Large Area Radio Frequency Capacitively-coupled Reactors
Authors: Strahm Benjamin , Howling Alan A. , Hollenstein Christoph 
Published: April 2011

ABSTRACTThe microcrystalline silicon (μc-Si:H) intrinsic layer for application in micromorph tandem photovoltaic solar cells has to be optimized in order to achieve cost-effective mass production of solar cells in large area, radio frequency, capacitively-coupled PECVD reactors. The optimization has to be performed with regard to the deposition rate as well as to the crystallinity uniformity over the substrate area. The latter condition is difficult to achieve since the optimal solar grade μc-Si:H is deposited at the limit between a-Si:H and μc-Si:H material, where the film crystallinity is very sensitive to the plasma process. In this work, a controlled RF power nonuniformity was generated in a large area industrial reactor. The resulting film uniformity was studied as a function of the deposition regimes. Results show that the higher the input silane concentration, the more the uniformity of the crystallinity is sensitive to the RF power nonuniformity for films deposited at the limit between a-Si:H and μc-Si:H. The effect of the input silane concentration on the microstructure uniformity could be explained on the basis of an analytical plasma chemistry model. This result is important for reactor design. In reactors generating nonuniform plasma the input silane concentration has to be limited to low values in order to deposit films with uniform microstructure. To benefit from the high silane flow rate utilization fraction encountered only for higher input silane concentration, the RF power distribution has to be as uniform as possible over the whole substrate area.
Cone Kinetics Model: Insights into the Morphologies of Mixed-phase Silicon Film Growth
Authors: Branz Howard M. , Stradins Paul , Teplin Charles W. 
Published: April 2011

ABSTRACTThe ‘cone kinetics’ model, which explains development of cone-shaped inclusions during nanocrystalline silicon film growth and during low-temperature silicon epitaxy breakdown, is extended to protocrystalline (‘edge’) amorphous silicon, Si heterojunctions and other Si film morpholologies. We generalize the physics underlying cone formation and present diagrams that delineate the deposition regimes giving rise to the different film morphologies; these regimes are determined by the nucleation rate of the second phase and the relative growth rate of the phases present. The model predicts cone growth during thin-film deposition by plasma-enhanced and other chemical vapor deposition techniques when isotropic growth is coupled with the isolated nucleation of a second phase with a higher growth rate. Protocrystalline amorphous silicon and other embedded crystallite phases are formed when a second phase successfully nucleates but has a smaller growth rate than the surrounding amorphous film. The cone kinetics phase diagram provides a simple explanation of the various nanocrystalline film morphologies observed when silane precursors are diluted with different concentrations of hydrogen gas.
Metastable Defects in Light Soaked Amorphous Silicon at 77 K
Authors: Ju Tong , Stradins Paul , Taylor P. Craig 
Published: April 2011

ABSTRACTWe have observed the growth of defects caused by optical illumination in liquid nitrogen. We kept the sample in liquid nitrogen over one year. After one year and half the ESR signal reached ∼1018 cm−3 with no evidence of saturation. After that, we step-wise annealed isochronal the sample up to room temperature, where two thirds of original defects were annealed out. After room temperature, the sample was annealing isothermally around 300 K for several months. At this temperature, the defects slowly anneal. After a hundred of hours at 295K, the defect density decreased 10x from its original value at 77K.
Studies on the Surface Reactions of Substituted Disilanes with Silica Surface
Authors: Blomberg Tom , Matero Raija , Haukka Suvi , Root Andrew 
Published: April 2011

ABSTRACTBoth CVD and ALD deposition techniques benefit from a detailed understanding of the reaction mechanisms of the precursor molecules with the surface. In this paper, the reactions of hexakis ethylaminodisilane (AHEAD™), hexamethoxydisilane and hexamethyldisilane were studied on high surface area silica granules at 200-375 °C. Silica was heat treated at 200-820 °C to control the number of surface Si-OH groups. The samples were characterized by FTIR and solid state NMR spectroscopy. After the chemisorption of the precursors with silica, Si-H bonds, not originally present in the molecules, were identified for AHEAD and hexamethoxydisilane, but not for hexamethyldisilane. It is suggested that with AHEAD and hexamethoxydisilane, cleavage of the Si-Si bond takes place during the chemisorption with Si-OH sites. Since no reaction for hexamethyldisilane at the studied temperatures was observed, a prerequisite for the reaction with Si-OH groups seems to be the presence of electronegative O or N atoms in the ligands. In the paper, possible reaction mechanisms with the various surface species are discussed.
Photoluminescence of Different Phase Si Nanoclusters in Amorphous Hydrogenated Silicon
Authors: Torchynska Tetyana V. 
Published: April 2011

ABSTRACTThis paper presents the results of XRD and PL spectrum studies for Si nano-clusters embedded in amorphous silicon matrix. Investigated layers were deposited by the hot-wire CVD method on glass substrates at the wafer temperature 300°C and different filament temperatures from the range 1735-1885°C. It was shown that variation of filament temperatures allows producing the films with desirable parameters. Using of X-ray diffraction and photoluminescence methods the correlation between the intensity of some photoluminescence bands and the concentrations of Si nanocrystallites and amorphous Si nanoclusters has been shown. The nature of light emission is discussed.
On determination of properties of ultrathin and very thin silicon oxide layers by FTIR and X - ray reflectivity
Authors: Kopani Martin , Jergel Matej , Kobayashi Hikaru , Takahashi Masao , Brunner Robert , Mikula Milan , Imamura Kentarou , Jurecka Stanislav , Pincik Emil 
Published: April 2011

ABSTRACTWe analyze properties of ultra-thin SiO2 + very thin SiOx double layer structure formed on high-doped n-type Si (100) wafers using FTIR, X-ray reflectivity and AFM methods. The observed absorption band around 1230 cm−1 is attributed to the longitudinal optical mode of SiOx precipitates incorporated in silicon matrix. In particular, the corresponding peak positions indicate that there are precipitates of SiOx with x >1.8. The absorption band around 1070 cm−1 is attributed to the Si–O–Si stretching bond. This position is characteristic for stoichiometric SiO2. From the results it can be concluded that differently shaped particles co-exist in the samples. This assumption is supported by the oxide density measurements performed by FTIR and X-ray reflectivity. We determined density of oxide layers, roughness of corresponding interfaces, and surface roughness by the X-ray reflectivity. The obtained values were compared with those determined by FTIR and AFM. Additionally, we present the results of multifractal analysis on a complete set of six samples.