WorldWideScience

Sample records for amorphous biophotonic nanostructure

  1. Structural Diversity of Self-Assembled Iridescent Arthropod Biophotonic Nanostructures

    Science.gov (United States)

    Saranathan, Vinod Kumar; Prum, Richard O.

    2015-03-01

    Many organisms, especially arthropods, produce vivid interference colors using diverse mesoscopic (100-350 nm) integumentary biophotonic nanostructures that are increasingly being investigated for technological applications. Despite a century of interest, we lack precise structural knowledge of many biophotonic nanostructures and mechanisms controlling their development, when such knowledge can open novel biomimetic routes to facilely self-assemble tunable, multi-functional materials. Here, we use synchrotron small angle X-ray scattering and electron microscopy to characterize the photonic nanostructure of 140 iridescent integumentary scales and setae from 127 species of terrestrial arthropods in 85 genera from 5 orders. We report a rich nanostructural diversity, including triply-periodic bicontinuous networks, close-packed spheres, inverse columnar, perforated lamellar, and disordered sponge-like morphologies, commonly observed as stable phases of amphiphilic surfactants, block copolymer, and lyotropic lipid-water systems. Diverse arthropod lineages appear to have independently evolved to utilize the self-assembly of infolding bilayer membranes to develop biophotonic nanostructures that span the phase-space of amphiphilic morphologies, but at optical length scales.

  2. Biophotonics

    CERN Document Server

    Pavesi, Lorenzo

    2008-01-01

    More profound understanding of the nature of light and light-matter interactions in biology has enabled many applications in the biology and medical fields. So a new discipline is born, namely biophotonics. The aim of this book is to review the current state-of-the-art of the field by means of authoritative chapters written by the world leaders of the respective fields. Biosensors, biochips, optical tomography, optical microsurgery, photodynamics therapy, bioactivation of gene, photobiology of skin, and nanobiophotonics are each introduced and recent advances presented. This book will be useful not only to physicians, biologists, physicists, chemists, materials scientists, and engineers but also to graduate students who are interested in these rapidly developing fields.

  3. Room temperature photoluminescence from nanostructured amorphous carbon

    OpenAIRE

    Henley, SJ; Carey, JD; Silva, SRP

    2004-01-01

    Visible room-temperature photoluminescence (PL) was observed from hydrogen-free nanostructured amorphous carbon films deposited by pulsed laser ablation in different background pressures of argon (PAr). By varying PAr from 5 to 340 mTorr, the film morphology changed from smooth to rough and at the highest pressures, low-density filamentary growth was observed. Over the same pressure regime an increase in the ordering of sp2 bonded C content was observed using visible Raman spectroscopy. Th...

  4. Amorphous Silicon-Carbon Nanostructure Solar Cells

    Science.gov (United States)

    Schriver, Maria; Regan, Will; Loster, Matthias; Zettl, Alex

    2011-03-01

    Taking advantage of the ability to fabricate large area graphene and carbon nanotube networks (buckypaper), we produce Schottky junction solar cells using undoped hydrogenated amorphous silicon thin films and nanostructured carbon films. These films are useful as solar cell materials due their combination of optical transparency and conductance. In our cells, they behave both as a transparent conductor and as an active charge separating layer. We demonstrate a reliable photovoltaic effect in these devices with a high open circuit voltage of 390mV in buckypaper devices. We investigate the unique interface properties which result in an unusual J-V curve shape and optimize fabrication processes for improved solar conversion efficiency. These devices hold promise as a scalable solar cell made from earth abundant materials and without toxic and expensive doping processes.

  5. Domain morphology, boundaries, and topological defects in biophotonic gyroid nanostructures of butterfly wing scales.

    Science.gov (United States)

    Singer, Andrej; Boucheron, Leandra; Dietze, Sebastian H; Jensen, Katharine E; Vine, David; McNulty, Ian; Dufresne, Eric R; Prum, Richard O; Mochrie, Simon G J; Shpyrko, Oleg G

    2016-06-01

    Many organisms in nature have evolved sophisticated cellular mechanisms to produce photonic nanostructures and, in recent years, diverse crystalline symmetries have been identified and related to macroscopic optical properties. However, because we know little about the distributions of domain sizes, the orientations of photonic crystals, and the nature of defects in these structures, we are unable to make the connection between the nanostructure and its development and functionality. We report on nondestructive studies of the morphology of chitinous photonic crystals in butterfly wing scales. Using spatially and angularly resolved x-ray diffraction, we find that the domains are highly oriented with respect to the whole scale, indicating growth from scale boundaries. X-ray coherent diffractive imaging reveals two types of crystalline domain interfaces: abrupt changes between domains emerging from distinct nucleation sites and smooth transitions with edge dislocations presumably resulting from internal stresses during nanostructure development. Our study of the scale structure reveals new aspects of photonic crystal growth in butterfly wings and shows their similarity to block copolymer materials. It opens new avenues to exploration of fundamental processes underlying the growth of biological photonic nanostructures in a variety of species. PMID:27386575

  6. A Next Generation BioPhotonics Workstation

    DEFF Research Database (Denmark)

    Glückstad, Jesper; Palima, Darwin; Tauro, Sandeep; Bañas, Andrew Rafael

    2011-01-01

    We are developing a Next Generation BioPhotonics Workstation to be applied in research on regulated microbial cell growth including their underlying physiological mechanisms, in vivo characterization of cell constituents and manufacturing of nanostructures and meta-materials.......We are developing a Next Generation BioPhotonics Workstation to be applied in research on regulated microbial cell growth including their underlying physiological mechanisms, in vivo characterization of cell constituents and manufacturing of nanostructures and meta-materials....

  7. Next Generation BioPhotonics Workstation

    DEFF Research Database (Denmark)

    Glückstad, Jesper

    2010-01-01

    We are developing a Next Generation BioPhotonics Workstation to be applied in research on regulated microbial cell growth including their underlying physiological mechanisms, in vivo characterization of cell constituents and manufacturing of nanostructures and meta-materials.......We are developing a Next Generation BioPhotonics Workstation to be applied in research on regulated microbial cell growth including their underlying physiological mechanisms, in vivo characterization of cell constituents and manufacturing of nanostructures and meta-materials....

  8. Nanostructured amorphous nickel oxide with enhanced antioxidant activity

    Energy Technology Data Exchange (ETDEWEB)

    Madhu, G. [Department of Physics, University of Kerala, Kariavattom Campus, Thiruvananthapuram, Kerala 695581 (India); Department of Physics, University College, Thiruvananthapuram, Kerala 695034 (India); Biju, V., E-mail: bijunano@gmail.com [Department of Physics, University of Kerala, Kariavattom Campus, Thiruvananthapuram, Kerala 695581 (India)

    2015-07-15

    Highlights: • Synthesis of nanostructured amorphous nickel oxide by a facile chemical route. • Enhanced antioxidant activity of amorphous NiO compared to crystalline samples. • Role of O{sup 2−} vacancies and high specific surface area in antioxidant activity. • Use of DC conductivity, XPS and BET to explain enhanced antioxidant activity. - Abstract: Nanostructured amorphous nickel oxide was synthesized by the thermal decomposition of nickel chloride–ethanol amine complex. The X-ray diffraction and Transmission Electron Microscopic studies established the amorphous nature of the sample. The Fourier Transform Infrared, Scanning Electron Microscopy, Energy Dispersive and X-ray Photoelectron Spectroscopic studies of the sample revealed the formation of NiO. The specific surface area of the sample is measured using Brunauer–Emmett–Teller analysis and the mesoporous nature of the sample is established through Barrett–Joyner–Halenda pore size distribution analysis. The antioxidant activity of the amorphous sample measured by 1,1-diphenyl-2-picryl hydrazyl (DPPH) scavenging is found to be nearly twice greater than that reported for nanocrystalline NiO samples. The estimated radical scavenging activity of the sample is correlated with the DC conductivity values measured in vacuum and air ambience. The enhanced antioxidant activity of the amorphous NiO is accounted by the increase in the concentration of O{sup 2−} vacancies and the specific surface area. The Ni 2p and O 1s X-ray Photoelectron Spectroscopic studies of the sample support the inference.

  9. PREFACE: Ultrafast biophotonics Ultrafast biophotonics

    Science.gov (United States)

    Gu, Min; Reid, Derryck; Ben-Yakar, Adela

    2010-08-01

    The use of light to explore biology can be traced to the first observations of tissue made with early microscopes in the mid-seventeenth century, and has today evolved into the discipline which we now know as biophotonics. This field encompasses a diverse range of activities, each of which shares the common theme of exploiting the interaction of light with biological material. With the rapid advancement of ultrafast optical technologies over the last few decades, ultrafast lasers have increasingly found applications in biophotonics, to the extent that the distinctive new field of ultrafast biophotonics has now emerged, where robust turnkey ultrafast laser systems are facilitating cutting-edge studies in the life sciences to take place in everyday laboratories. The broad spectral bandwidths, precision timing resolution, low coherence and high peak powers of ultrafast optical pulses provide unique opportunities for imaging and manipulating biological systems. Time-resolved studies of bio-molecular dynamics exploit the short pulse durations from such lasers, while other applications such as optical coherence tomography benefit from the broad optical bandwidths possible by using super-continuum generation and additionally allowing for high speed imaging with speeds as high as 47 000 scans per second. Continuing progress in laser-system technology is accelerating the adoption of ultrafast techniques across the life sciences, both in research laboratories and in clinical applications, such as laser-assisted in situ keratomileusis (LASIK) eye surgery. Revolutionizing the field of optical microscopy, two-photon excitation fluorescence (TPEF) microscopy has enabled higher spatial resolution with improved depth penetration into biological specimens. Advantages of this nonlinear optical process include: reduced photo-interactions, allowing for extensive imaging time periods; simultaneously exciting multiple fluorescent molecules with only one excitation wavelength; and

  10. Studies of nanostructured copper/hydrogenated amorphous carbon multilayer films

    International Nuclear Information System (INIS)

    Research highlights: → Multilayer coatings have been grown by RF-PECVD and RF-sputtering techniques under varied bilayers from one to four. → After deposition these coatings were characterized for stress, hardness, elastic modulus, SEM, AFM, XPS, EDAX, SIMS, PL, transmission, and conductivity. → Observed results were correlated fairly with each other. - Abstract: Nanostructured copper/hydrogenated amorphous carbon (a-C:H) multilayer grown in a low base vacuum (1 x 10-3 Torr) system combining plasma-enhanced chemical vapor deposition and sputtering techniques. These nanostructured multilayer were found to exhibit improved electrical, optical, surface and structural properties, compared to that of monolayer a-C:H films. The residual stresses of such multilayer structure were found well below 1 GPa. Scanning electron microscopy and atomic force microscopy results revealed a nanostructured surface morphology and low surface roughnesses values. X-ray photoelectron spectroscopy, secondary ion mass spectroscopy and energy dispersive X-ray analysis confirmed a very small amount of copper in these films. These structures exhibited very high optical transparency in the near infrared region (∼90%) and the optical band gap varied from 1.35 to 1.7 eV. It was noticed that the temperature dependent conductivity improved due to the presence of both copper and the nano-structured morphology.

  11. Physicochemical determinants in the cellular responses to nanostructured amorphous silicas.

    Science.gov (United States)

    Gazzano, Elena; Ghiazza, Mara; Polimeni, Manuela; Bolis, Vera; Fenoglio, Ivana; Attanasio, Angelo; Mazzucco, Gianna; Fubini, Bice; Ghigo, Dario

    2012-07-01

    Amorphous silicas, opposite to crystalline polymorphs, have been regarded so far as nonpathogenic, but few studies have addressed the toxicity of the wide array of amorphous silica forms. With the advent of nanotoxicology, there has been a rising concern about the safety of silica nanoparticles to be used in nanomedicine. Here, we report a study on the toxicity of amorphous nanostructured silicas obtained with two different preparation procedures (pyrolysis vs. precipitation), the pyrogenic in two very different particle sizes, in order to assess the role of size and origin on surface properties and on the cell damage, oxidative stress, and inflammatory response elicited in murine alveolar macrophages. A quartz dust was employed as positive control and monodispersed silica spheres as negative control. Pyrogenic silicas were remarkably more active than the precipitated one as to cytotoxicity, reactive oxygen species production, lipid peroxidation, nitric oxide synthesis, and production of tumor necrosis factor-α, when compared both per mass and per unit surface. Between the two pyrogenic silicas, the larger one was the more active. Silanols density is the major difference in surface composition among the three silicas, being much larger than the precipitated one as indicated by joint calorimetric and infrared spectroscopy analysis. We assume here that full hydroxylation of a silica surface, with consequent stable coverage by water molecules, reduces/inhibits toxic behavior. The preparation route appears thus determinant in yielding potentially toxic materials, although the smallest size does not always correspond to an increased toxicity. PMID:22491428

  12. Optical studies of amorphous Ge nanostructures in Al2O3 produced by pulsed laser deposition

    International Nuclear Information System (INIS)

    Thin films with embedded amorphous Ge nanostructures are characterised by in-situ and post-deposition techniques in order to study their size-dependent properties. The films are multilayer structures in which Ge nanostructured layers with effective thickness are separated by amorphous aluminium oxide layers (Al2O3). During deposition in-situ reflectivity measurements are used to achieve information on the amount of Ge deposited and on the Al2O3 coverage. The effective optical properties of the films were obtained from spectroscopic ellipsometry measurement analysis. Our results suggest a topological evolution of the Ge nanostructures as a function of the Ge content and the existence of size-dependent quantum confinement effects in the nanostructures. - Highlights: ► Amorphous Ge nanostructures with tunable optical band-gap embedded in Al2O3 matrix ► In-situ reflectivity characterisation of amorphous Ge nanostructure ► Ex-situ spectroscopic ellipsometry characterisation of amorphous Ge nanostructures ► Size-dependent optical band-gap study of amorphous Ge nanostructures

  13. BioPhotonics Workstation: a university tech transfer challenge

    DEFF Research Database (Denmark)

    Glückstad, Jesper; Bañas, Andrew Rafael; Tauro, Sandeep;

    2011-01-01

    Conventional optical trapping or tweezing is often limited in the achievable trapping range because of high numerical aperture and imaging requirements. To circumvent this, we are developing a next generation BioPhotonics Workstation platform that supports extension modules through a long working...... generation BioPhotonics Workstation to be applied in three-dimensional studies on regulated microbial cell growth including their underlying physiological mechanisms, in vivo characterization of cell constituents and manufacturing of nanostructures and new materials....

  14. Quantum Dots for Biophotonics

    OpenAIRE

    Ken-Tye Yong

    2012-01-01

    This theme issue provides an excellent collection of reviews and original research articles on the study of various bioconjugated quantum dot formulations for diagnostics and therapy applications using biophotonic imaging and sensing approaches.

  15. Amorphous mixed-metal hydroxide nanostructures for advanced water oxidation catalysts

    Science.gov (United States)

    Gao, Y. Q.; Liu, X. Y.; Yang, G. W.

    2016-02-01

    The design of highly efficient, durable, and earth-abundant catalysts for the oxygen evolution reaction (OER) is crucial in order to promote energy conversion and storage processes. Here, we synthesize amorphous mixed-metal (Ni-Fe) hydroxide nanostructures with a homogeneous distribution of Ni/Fe as well as a tunable Ni/Fe ratio by a simple, facile, green and low-cost electrochemical technique, and we demonstrate that the synthesized amorphous nanomaterials possess ultrahigh activity and super long-term cycle stability in the OER process. The amorphous Ni0.71Fe0.29(OH)x nanostructure affords a current density of 10 mA cm-2 at an overpotential of a mere 0.296 V and a small Tafel slope of 58 mV dec-1, while no deactivation is detected in the CV testing even up to 30 000 cycles, which suggests the promising application of these amorphous nanomaterials in electrochemical oxidation. Meanwhile, the distinct catalytic activities among these amorphous Ni-Fe hydroxide nanostructures prompts us to take notice of the composition of the alloy hydroxides/oxides when studying their catalytic properties, which opens an avenue for the rational design and controllable preparation of such amorphous nanomaterials as advanced OER electrocatalysts.The design of highly efficient, durable, and earth-abundant catalysts for the oxygen evolution reaction (OER) is crucial in order to promote energy conversion and storage processes. Here, we synthesize amorphous mixed-metal (Ni-Fe) hydroxide nanostructures with a homogeneous distribution of Ni/Fe as well as a tunable Ni/Fe ratio by a simple, facile, green and low-cost electrochemical technique, and we demonstrate that the synthesized amorphous nanomaterials possess ultrahigh activity and super long-term cycle stability in the OER process. The amorphous Ni0.71Fe0.29(OH)x nanostructure affords a current density of 10 mA cm-2 at an overpotential of a mere 0.296 V and a small Tafel slope of 58 mV dec-1, while no deactivation is detected in the CV

  16. HRTEM study of Popigai impact diamond: heterogeneous diamond nanostructures in native amorphous carbon matrix

    Science.gov (United States)

    Kis, Viktoria K.; Shumilova, Tatyana; Masaitis, Victor

    2016-07-01

    High-resolution transmission electron microscopy was applied for the detailed nanostructural investigation of Popigai impact diamonds with the aim of revealing the nature of the amorphous carbon of the matrix. The successful application of two complementary specimen preparation methods, focused ion beam (FIB) milling and mechanical cleavage, allowed direct imaging of nanotwinned nanodiamond crystals embedded in a native amorphous carbon matrix for the first time. Based on its stability under the electron beam, native amorphous carbon can be easily distinguished from the amorphous carbon layer produced by FIB milling during specimen preparation. Electron energy loss spectroscopy of the native amorphous carbon revealed the dominance of sp 2-bonded carbon and the presence of a small amount of oxygen. The heterogeneous size distribution and twin density of the nanodiamond crystals and the structural properties of the native amorphous carbon are presumably related to non-graphitic (organic) carbon precursor material.

  17. Information optics in biophotonics

    DEFF Research Database (Denmark)

    Glückstad, Jesper

    2010-01-01

    I will outline the specifications of a portable Biophotonics Workstation we recently have developed that utilizes a single high-speed spatial light modulator to generate an array of currently up to 100 reconfigurable laser-traps with adjustable power ratios making 3D real-time manipulation possib...

  18. In Situ Mechanical Property Measurements of Amorphous Carbon-Boron Nitride Nanotube Nanostructures

    Science.gov (United States)

    Kim, Jae-Woo; Lin, Yi; Nunez, Jennifer Carpena; Siochi, Emilie J.; Wise, Kristopher E.; Connell, John W.; Smith, Michael W.

    2011-01-01

    To understand the mechanical properties of amorphous carbon (a-C)/boron nitride nanotube (BNNT) nanostructures, in situ mechanical tests are conducted inside a transmission electron microscope equipped with an integrated atomic force microscope system. The nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation. We demonstrate multiple in situ tensile, compressive, and lap shear tests with a-C/BNNT hybrid nanostructures. The tensile strength of the a-C/BNNT hybrid nanostructure is 5.29 GPa with about 90 vol% of a-C. The tensile strength and strain of the end-to-end joint structure with a-C welding is 0.8 GPa and 5.2% whereas the lap shear strength of the side-by-side joint structure with a-C is 0.25 GPa.

  19. In situ mechanical property measurements of amorphous carbon-boron nitride nanotube nanostructures

    Science.gov (United States)

    Kim, Jae-Woo; Carpena Núñez, Jennifer; Siochi, Emilie J.; Wise, Kristopher E.; Lin, Yi; Connell, John W.; Smith, Michael W.

    2012-01-01

    To understand the mechanical properties of amorphous carbon (a-C)/boron nitride nanotube (BNNT) nanostructures, in situ mechanical tests are conducted inside a transmission electron microscope equipped with an integrated atomic force microscope system. The nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation. We demonstrate multiple in situ tensile, compressive, and lap shear tests with a-C/BNNT hybrid nanostructures. The tensile strength of the a-C/BNNT hybrid nanostructure is 5.29 GPa with about 90 vol% of a-C. The tensile strength and strain of the end-to-end joint structure with a-C welding is 0.8 GPa and 5.2% whereas the lap shear strength of the side-by-side joint structure with a-C is 0.25 GPa.

  20. Optical contrast in ion-implanted amorphous silicon carbide nanostructures

    International Nuclear Information System (INIS)

    Topographic and optical contrasts formed by Ga+ ion irradiation of thin films of amorphous silicon carbide have been investigated with scanning near-field optical microscopy. The influence of ion-irradiation dose has been studied in a pattern of sub-micrometre stripes. While the film thickness decreases monotonically with ion dose, the optical contrast rapidly increases to a maximum value and then decreases gradually. The results are discussed in terms of the competition between the effects of ion implantation and surface milling by the ion beam. The observed effects are important for uses of amorphous silicon carbide thin films as permanent archives in optical data storage applications

  1. Biophotonics: a European perspective

    Science.gov (United States)

    Robin, Thierry; Cochard, Jacques; Breussin, Frédéric

    2013-03-01

    The objective of the present work is to determine the opportunities and challenges for Biophotonics business development in Europe for the next five years with a focus on sensors and systems: for health diagnostics and monitoring; for air, water and food safety and quality control. The development of this roadmap was initiated and supported by EPIC (The European Photonics Industry Consortium). We summarize the final roadmap data: market application segments and trends, analysis of the market access criteria, analysis of the technology trends and major bottlenecks and challenges per application.

  2. Biophotonic integrated circuits

    Science.gov (United States)

    Cohen, Daniel A.; Nolde, Jill A.; Wang, Chad S.; Skogen, Erik J.; Rivlin, A.; Coldren, Larry A.

    2004-12-01

    Biosensors rely on optical techniques to obtain high sensitivity and speed, but almost all biochips still require external light sources, optics, and detectors, which limits the widespread use of these devices. The optoelectronics technology base now allows monolithic integration of versatile optical sources, novel sensing geometries, filters, spectrometers, and detectors, enabling highly integrated chip-scale sensors. We discuss biophotonic integrated circuits built on both GaAs and InP substrates, incorporating widely tunable lasers, novel evanescent field sensing waveguides, heterodyne spectrometers, and waveguide photodetectors, suitable for high sensitivity transduction of affinity assays.

  3. Interfacial defects of hard magnetic Pr2Fe14B phase from amorphous to nanostructures

    Institute of Scientific and Technical Information of China (English)

    吴玉程

    2004-01-01

    The interfacial defects of hard magnetic Pr2 Fe14 B phase from amorphous to nanostructures have been investigated by positron lifetime spectroscopy. The nanostructure was produced by melt-spinning and nanocrystallization route. The two main components can be ascribed to vacancy-like defects in the intergranular layers or the interfaces, and microvoids or large free volumes with size compared to several missing atoms at the interactions of the atomic aggregates or the crystallites. The remarkable changes in the positron lifetimes from the amorphous structure to the nanocrystructure with varied sizes can be interpreted, indicating that the structural transformation and the grain growth induce the defect changes occurring at the interfaces with different shapes and sizes.

  4. Nanostructuring of GeTiO amorphous films by pulsed laser irradiation

    Directory of Open Access Journals (Sweden)

    Valentin S. Teodorescu

    2015-04-01

    Full Text Available Laser pulse processing of surfaces and thin films is a useful tool for amorphous thin films crystallization, surface nanostructuring, phase transformation and modification of physical properties of thin films. Here we show the effects of nanostructuring produced at the surface and under the surface of amorphous GeTiO films through laser pulses using fluences of 10–30 mJ/cm2. The GeTiO films were obtained by RF magnetron sputtering with 50:50 initial atomic ratio of Ge:TiO2. Laser irradiation was performed by using the fourth harmonic (266 nm of a Nd:YAG laser. The laser-induced nanostructuring results in two effects, the first one is the appearance of a wave-like topography at the film surface, with a periodicity of 200 nm and the second one is the structure modification of a layer under the film surface, at a depth that is related to the absorption length of the laser radiation. The periodicity of the wave-like relief is smaller than the laser wavelength. In the modified layer, the Ge atoms are segregated in spherical amorphous nanoparticles as a result of the fast diffusion of Ge atoms in the amorphous GeTiO matrix. The temperature estimation of the film surface during the laser pulses shows a maximum of about 500 °C, which is much lower than the melting temperature of the GeTiO matrix. GeO gas is formed at laser fluences higher than 20 mJ/cm2 and produces nanovoids in the laser-modified layer at the film surface. A glass transition at low temperatures could happen in the amorphous GeTiO film, which explains the formation of the wave-like topography. The very high Ge diffusivity during the laser pulse action, which is characteristic for liquids, cannot be reached in a viscous matrix. Our experiments show that the diffusivity of atomic and molecular species such as Ge and GeO is very much enhanced in the presence of the laser pulse field. Consequently, the fast diffusion drives the formation of amorphous Ge nanoparticles through the

  5. Biophotonics concepts to applications

    CERN Document Server

    Keiser, Gerd

    2016-01-01

    This book is designed to introduce senior-level and postgraduate students to the principles and applications of biophotonics. It also will serve well as a working reference to practicing physicians, clinicians, biomedical researchers, and biomedical engineers dealing with photonics-based tools and instruments. The book topics include the fundamentals of optics and photonics, the optical properties of biological tissues, various types of light-tissue interactions, microscopy for visualizing tissue components, spectroscopy for optically analyzing the properties of healthy and diseased tissue, and optical biomedical imaging. The tools and techniques described in the book include laser and LED optical sources, photodetectors, optical fibers, bioluminescent probes for labeling cells, optical-based biosensors, nanophotonics, surface plasmon resonance, and lab-on-a-chip technologies. Among the applications are optical coherence tomography (OCT), flow cytometery, photodynamic therapy (PDT), low-level light therapy (L...

  6. Leading research on super metal. 3. Amorphous and nanostructured metallic materials; Super metal no sendo kenkyu. 3. Kogata buzai

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-03-01

    Very fine structure control technique for amorphous and nanostructured metallic materials was reviewed to exceed the marginal performance of small metallic member materials. In Japan, high strength alloys and anticorrosion alloys are currently developed as an amorphous structure control technique, and ultra fine powder production and nano-compaction molding are studied for nanostructured materials. Fabrication of amorphous alloy wire materials and metal glass in USA are also introduced. Fabrication of metallic nanocrystals deposited within gas phase in Germany are attracting attention. The strength and abrasion resistance are remarkably enhanced by making nanostructured crystals and dispersing them. It may be most suitable to utilize amorphous and nanostructured metallic materials for earth-friendly materials having anticorrosion, and catalyst and biomaterial affinities, and also for magnetic materials. It is important for controlling micro-structures to clarify the formation mechanism of structures. For their processing techniques, the diversity and possibility are suggested, as to the condensation and solidification of gaseous and liquid phase metals, the molding and processing of very fine solid phase alloys, and the manufacturing members by heat treatment. 324 refs., 109 figs., 21 tabs.

  7. Sculpting light for contemporary biophotonics

    DEFF Research Database (Denmark)

    Glückstad, Jesper

    manipulation, active microscopy, structured illumination, optical security, parallel laser marking trials and recently in contemporary biophotonics applications such as for real-­‐time parallel two-­‐photon optogenetics and neurophotonics. Our most recent GPC light sculpting developments geared towards these...

  8. A next generation biophotonics workstation

    DEFF Research Database (Denmark)

    Glückstad, Jesper

    imaging, image based information security, image recognition, bio-photonics, and novel image sensors. It will be a forum for scientific interaction and collaboration between well known scientists in the field and educational outreach to students. This workshop will consist of keynote and invited talks (by...

  9. Nanostructural properties of amorphous silicon carbide by GISAXS and optical spectroscopy

    International Nuclear Information System (INIS)

    The nano-structural properties of non-stehiometric hydrogenated amorphous silicon carbide thin films, deposited by magnetron sputtering in wide range of carbon concentration (5-50 at.%) and high hydrogen content (17-45 at.%), were analysed by GISAXS (Grazing Incidence Small Angle X-ray Scattering). The film composition and density were estimated by combining vibrational spectroscopy, RBS (Rutherford Backscattering Spectrometry) and ERDA (Elastic Recoil Detection Analysis). It was found that by increasing carbon and hydrogen concentration, the film density decreases, indicating the increase of voids contribution. The GISAXS was performed on ELETTRA synchrotron radiation source, Trieste (Italy). The obtained results show the presence of 'particles' with variation in mean dimensions between 1.7 and 2.5 nm and broad size distribution. The size of 'particles', most probably large voids or voids agglomerates, increases with carbon to silicon ratio and decreases with hydrogen concentration

  10. Mescoscopic Toolbox for Biophotonics

    DEFF Research Database (Denmark)

    Glückstad, Jesper

    ‐fabricated structures possible with the use of a simple joystick. The fabrication of microstructures with nanometer‐sized features, for example a nano‐needle, coupled with the real‐time user‐interactive optical control allows a user to “robotically” actuate appended nanostructures depending on their intended function....... These micro‐platforms carrying nanotools are seen to have potential uses in a variety of micro‐biological experiments. Optically actuated nano‐needles may be functionalized or directly used to perforate targeted cells at specific locations or force the complete separation of dividing cells, among other...

  11. Biophoton Emission Induced by Heat Shock

    OpenAIRE

    Kobayashi, Katsuhiro; Okabe, Hirotaka; Kawano, Shinya; Hidaka, Yoshiki; Hara, Kazuhiro

    2014-01-01

    Ultraweak biophoton emission originates from the generation of reactive oxygen species (ROS) that are produced in mitochondria as by-products of cellular respiration. In healthy cells, the concentration of ROS is minimized by a system of biological antioxidants. However, heat shock changes the equilibrium between oxidative stress and antioxidant activity, that is, a rapid rise in temperature induces biophoton emission from ROS. Although the rate and intensity of biophoton emission was observe...

  12. Biophoton emission induced by heat shock.

    Directory of Open Access Journals (Sweden)

    Katsuhiro Kobayashi

    Full Text Available Ultraweak biophoton emission originates from the generation of reactive oxygen species (ROS that are produced in mitochondria as by-products of cellular respiration. In healthy cells, the concentration of ROS is minimized by a system of biological antioxidants. However, heat shock changes the equilibrium between oxidative stress and antioxidant activity, that is, a rapid rise in temperature induces biophoton emission from ROS. Although the rate and intensity of biophoton emission was observed to increase in response to elevated temperatures, pretreatment at lower high temperatures inhibited photon emission at higher temperatures. Biophoton measurements are useful for observing and evaluating heat shock.

  13. Inductively Coupled Plasma etching of amorphous silicon nanostructures over nanotopography using C4F8/SF6 chemistry

    OpenAIRE

    Harvey-Collard, Patrick; Jaouad, Abdelatif; Drouin, Dominique; Pioro-Ladrière, Michel

    2013-01-01

    Inductively Coupled Plasma (ICP) etching of amorphous silicon (a-Si) nanostructures using a continuous C4F8/SF6 plasma over nanotopography in silicon dioxide (SiO2) is investigated. The coil power of the ICP system is used to tune the a-Si etch rate from 20 to 125 nm/min. The etch rates of a-Si, SiO2 and electroresist are measured depending on the SF6 ratio, platen power and chamber pressure and used to optimize the a-Si:SiO2 etch selectivity. The results on nanostructures show that the prese...

  14. Preparation and characterizations of amorphous nanostructured SiC thin films by low energy pulsed laser deposition

    International Nuclear Information System (INIS)

    Amorphous silicon carbide (SiC) thin films were deposited on silicon substrates by pulsed laser ablation at room temperature. Thicknesses and surface morphology of the thin films were characterized using optical profilers, atomic force and field emission scanning electron microscopy. Nanohardnes, modulus and scratch resistance properties were determined using XP nanoindenter. The results show that crack free, smooth and nanostructured thin films can be deposited using low laser energy densities.

  15. Biophotons Contribute to Retinal Dark Noise.

    Science.gov (United States)

    Li, Zehua; Dai, Jiapei

    2016-06-01

    The discovery of dark noise in retinal photoreceptors resulted in a long-lasting controversy over its origin and the underlying mechanisms. Here, we used a novel ultra-weak biophoton imaging system (UBIS) to detect biophotonic activity (emission) under dark conditions in rat and bullfrog (Rana catesbeiana) retinas in vitro. We found a significant temperature-dependent increase in biophotonic activity that was completely blocked either by removing intracellular and extracellular Ca(2+) together or inhibiting phosphodiesterase 6. These findings suggest that the photon-like component of discrete dark noise may not be caused by a direct contribution of the thermal activation of rhodopsin, but rather by an indirect thermal induction of biophotonic activity, which then activates the retinal chromophore of rhodopsin. Therefore, this study suggests a possible solution regarding the thermal activation energy barrier for discrete dark noise, which has been debated for almost half a century. PMID:27059222

  16. Organic Nanocrystals for Nanomedicine and Biophotonics

    OpenAIRE

    Baba, Koichi; Kasai, Hitoshi; Nishida, Kohji; Nakanishi, Hachiro

    2010-01-01

    In this chapter we described three topics; first, we explained how to prepare the organic nanocrystals in aqueous dispersion system using the reprecipitation method. Second, we referred the recent our achievements of organic nanocrystals in nanomedicine and biophotonics. Third, we remarked the future direction of organic nanocrystals in nanomedicine and biophotonics. We believe that our organic nanocrystals technology, recent results, and ideas will be helpful especially for biochemist, bioph...

  17. Band-gap engineering by molecular mechanical strain-induced giant tuning of the luminescence in colloidal amorphous porous silicon nanostructures

    KAUST Repository

    Mughal, Asad Jahangir

    2014-01-01

    Nano-silicon is a nanostructured material in which quantum or spatial confinement is the origin of the material\\'s luminescence. When nano-silicon is broken into colloidal crystalline nanoparticles, its luminescence can be tuned across the visible spectrum only when the sizes of the nanoparticles, which are obtained via painstaking filtration methods that are difficult to scale up because of low yield, vary. Bright and tunable colloidal amorphous porous silicon nanostructures have not yet been reported. In this letter, we report on a 100 nm modulation in the emission of freestanding colloidal amorphous porous silicon nanostructures via band-gap engineering. The mechanism responsible for this tunable modulation, which is independent of the size of the individual particles and their distribution, is the distortion of the molecular orbitals by a strained silicon-silicon bond angle. This mechanism is also responsible for the amorphous-to-crystalline transformation of silicon. This journal is

  18. The toxicological mode of action and the safety of synthetic amorphous silica—A nanostructured material

    International Nuclear Information System (INIS)

    Synthetic amorphous silica (SAS), in the form of pyrogenic (fumed), precipitated, gel or colloidal SAS, has been used in a wide variety of industrial and consumer applications including food, cosmetics and pharmaceutical products for many decades. Based on extensive physico-chemical, ecotoxicology, toxicology, safety and epidemiology data, no environmental or health risks have been associated with these materials if produced and used under current hygiene standards and use recommendations. With internal structures in the nanoscale size range, pyrogenic, precipitated and gel SAS are typical examples of nanostructured materials as recently defined by the International Organisation for Standardisation (ISO). The manufacturing process of these SAS materials leads to aggregates of strongly (covalently) bonded or fused primary particles. Weak interaction forces (van der Waals interactions, hydrogen bonding, physical adhesion) between aggregates lead to the formation of micrometre (μm)-sized agglomerates. Typically, isolated nanoparticles do not occur. In contrast, colloidal SAS dispersions may contain isolated primary particles in the nano-size range which can be considered nano-objects. The size of the primary particle resulted in the materials often being considered as “nanosilica” and in the inclusion of SAS in research programmes on nanomaterials. The biological activity of SAS can be related to the particle shape and surface characteristics interfacing with the biological milieu rather than to particle size. SAS adsorbs to cellular surfaces and can affect membrane structures and integrity. Toxicity is linked to mechanisms of interactions with outer and inner cell membranes, signalling responses, and vesicle trafficking pathways. Interaction with membranes may induce the release of endosomal substances, reactive oxygen species, cytokines and chemokines and thus induce inflammatory responses. None of the SAS forms, including colloidal nano-sized particles, were

  19. The toxicological mode of action and the safety of synthetic amorphous silica-a nanostructured material.

    Science.gov (United States)

    Fruijtier-Pölloth, Claudia

    2012-04-11

    Synthetic amorphous silica (SAS), in the form of pyrogenic (fumed), precipitated, gel or colloidal SAS, has been used in a wide variety of industrial and consumer applications including food, cosmetics and pharmaceutical products for many decades. Based on extensive physico-chemical, ecotoxicology, toxicology, safety and epidemiology data, no environmental or health risks have been associated with these materials if produced and used under current hygiene standards and use recommendations. With internal structures in the nanoscale size range, pyrogenic, precipitated and gel SAS are typical examples of nanostructured materials as recently defined by the International Organisation for Standardisation (ISO). The manufacturing process of these SAS materials leads to aggregates of strongly (covalently) bonded or fused primary particles. Weak interaction forces (van der Waals interactions, hydrogen bonding, physical adhesion) between aggregates lead to the formation of micrometre (μm)-sized agglomerates. Typically, isolated nanoparticles do not occur. In contrast, colloidal SAS dispersions may contain isolated primary particles in the nano-size range which can be considered nano-objects. The size of the primary particle resulted in the materials often being considered as "nanosilica" and in the inclusion of SAS in research programmes on nanomaterials. The biological activity of SAS can be related to the particle shape and surface characteristics interfacing with the biological milieu rather than to particle size. SAS adsorbs to cellular surfaces and can affect membrane structures and integrity. Toxicity is linked to mechanisms of interactions with outer and inner cell membranes, signalling responses, and vesicle trafficking pathways. Interaction with membranes may induce the release of endosomal substances, reactive oxygen species, cytokines and chemokines and thus induce inflammatory responses. None of the SAS forms, including colloidal nano-sized particles, were shown

  20. Inductively Coupled Plasma etching of amorphous silicon nanostructures over nanotopography using C4F8/SF6 chemistry

    CERN Document Server

    Harvey-Collard, Patrick; Drouin, Dominique; Pioro-Ladrière, Michel; 10.1016/j.mee.2013.02.099

    2013-01-01

    Inductively Coupled Plasma (ICP) etching of amorphous silicon (a-Si) nanostructures using a continuous C4F8/SF6 plasma over nanotopography in silicon dioxide (SiO2) is investigated. The coil power of the ICP system is used to tune the a-Si etch rate from 20 to 125 nm/min. The etch rates of a-Si, SiO2 and electroresist are measured depending on the SF6 ratio, platen power and chamber pressure and used to optimize the a-Si:SiO2 etch selectivity. The results on nanostructures show that the presence of an insulating etch-stop layer affects the passivation ratio required to achieve vertical sidewalls. A low pressure is also necessary in order to etch the silicon nanostructure embedded into the oxide nanotrenches to form a highly conformable a-Si nanowire. We argue that both of these behaviors could be explained by surface charging effects. Finally, etching of 20 nm a-Si nanowires that cross 15 nm trenches in oxide with vertical sidewalls and a 4.3:1 a-Si:SiO2 etch selectivity is demonstrated. This etching process ...

  1. Label-Free Direct Electronic Detection of Biomolecules with Amorphous Silicon Nanostructures

    OpenAIRE

    Lund, John; Mehta, Ranjana; Parviz, Babak A.

    2006-01-01

    We present the fabrication and characterization of a nano-scale sensor made of amorphous silicon for the label-free, electronic detection of three classes of biologically important molecules: ions, oligonucleotides, and proteins. The sensor structure has an active element which is a 50 nm wide amorphous silicon semicircle and has a total footprint of less than 4 μm2. We demonstrate the functionalization of the sensor with receptor molecules and the electronic detection of three targets: H+ io...

  2. Nano-structural Modification of Amorphous Carbon Thin Films by Low-energy Electron Beam Irradiation

    Institute of Scientific and Technical Information of China (English)

    EijiIwamura; MasanoriYamaguchi

    2004-01-01

    A new approach using a low-energy electron beam radiation system was investigated to synthesize carbon hybrid structures in amorphous carbon thin films. Two types of amorphous carbon films, which were 15at% iron containing film and with column/inter-column structures, were deposited onto Si substrates by a sputtering technique and subsequently exposed to an electron shower of which the energy and dose rate were much smaller compared to an intense electron beam used in a transmission electron microscopy. As a result of the low-energy and low-dose electron irradiation process, graphitic structures formed in amorphous matrix at a relatively low temperature up to 450 K. Hybrid carbon thin films containing onion-like structures in an amorphous carbon matrix were synthesized by dynamic structural modification of iron containing amorphous carbon thin films. It was found that the graphitization progressed more in the electron irradiation than in annealing at 773K, and it was attributed to thermal and catalytic effects which are strongly related to grain growth of metal clusters. On the other hand, a reversal of TEM image contrast was observed in a-C films with column/inter-column structures. It is presumed that preferable graphitization occurred in the inter-column regions induced by electron irradiation.

  3. Nano-structural Modification of Amorphous Carbon Thin Films by Low-energy Electron Beam Irradiation

    Institute of Scientific and Technical Information of China (English)

    Eiji Iwamura; Masanori Yamaguchi

    2004-01-01

    A new approach using a low-energy electron beam radiation system was investigated to synthesize carbon hybrid structures in amorphous carbon thin films. Two types of amorphous carbon films, which were 15at% iron containing film and with column/inter-column structures, were deposited onto Si substrates by a sputtering technique and subsequently exposed to an electron shower of which the energy and dose rate were much smaller compared to an intense electron beam used in a transmission electron microscopy. As a result of the low-energy and low-dose electron irradiation process,graphitic structures formed in amorphous matrix at a relatively low temperature up to 450 K. Hybrid carbon thin films containing onion-like structures in an amorphous carbon matrix were synthesized by dynamic structural modification of iron containing amorphous carbon thin films. It was found that the graphitization progressed more in the electron irradiation than in annealing at 773K, and it was attributed to thermal and catalytic effects which are strongly related to grain growth of metal clusters. On the other hand, a reversal of TEM image contrast was observed in a-C films with column/inter-column structures. It is presumed that preferable graphitization occurred in the inter-column regions induced by electron irradiation.

  4. Next Genertation BioPhotonics Workstation

    DEFF Research Database (Denmark)

    Bañas, Andrew Rafael; Palima, Darwin; Tauro, Sandeep;

    We will outline the specs of our Biophotonics Workstation that can generate up to 100 reconfigurable laser-traps making 3D real-time optical manipulation of advanced structures, cells or tiny particles possible with the use of joysticks or gaming devices. Optically actuated nanoneedles may be fun...

  5. Low-Temperature Preparation of Amorphous-Shell/Nanocrystalline-Core Nanostructured TiO2 Electrodes for Flexible Dye-Sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Dongshe Zhang

    2008-01-01

    Full Text Available An amorphous shell/nanocrystalline core nanostructured TiO2 electrode was prepared at low temperature, in which the mixture of TiO2 powder and TiCl4 aqueous solution was used as the paste for coating a film and in this film amorphous TiO2 resulted from direct hydrolysis of TiCl4 at 100∘C sintering was produced to connect the particles forming a thick crack-free uniform nanostructured TiO2 film (12 μm, and on which a photoelectrochemical solar cell-based was fabricated, generating a short-circuit photocurrent density of 13.58 mA/cm2, an open-circuit voltage of 0.647 V, and an overall 4.48% light-to-electricity conversion efficiency under 1 sun illumination.

  6. Reflectivity of the gyroid biophotonic crystals in the ventral wing scales of the Green Hairstreak butterfly, Callophrys rubi

    OpenAIRE

    Michielsen, K.; De Raedt, H.; Stavenga, D.G.

    2010-01-01

    We present a comparison of the computer simulation data of gyroid nanostructures with optical measurements (reflectivity spectra and scattering diagrams) of ventral wing scales of the Green Hairstreak butterfly, Callophrys rubi. We demonstrate that the omnidirectional green colour arises from the gyroid cuticular structure grown in the domains of different orientation. We also show that this three-dimensional structure, operating as a biophotonic crystal, gives rise to various polarization ef...

  7. Physical vapor deposition synthesis of amorphous silicate layers and nanostructures as cosmic dust analogs

    Science.gov (United States)

    De Sio, A.; Tozzetti, L.; Wu, Ziyu; Marcelli, A.; Cestelli Guidi, M.; Della Ventura, G.; Zhao, Haifeng; Pan, Zhiyun; Li, Wenjie; Guan, Yong; Pace, E.

    2016-05-01

    Cosmic dust grains (CD) are part of the evolution of stars and planetary systems and pervade the interstellar medium. Thus, their spectral signature may be used to deduce the physical features of the observed astronomical objects or to study many physical and chemical processes in the interstellar medium. However, CD samples are available only from sample-and-return space missions. Thus, they are rare and not sufficient to be used to perform laboratory experiments of astrophysical interest, such as to produce reference spectra. In this contribution, we describe a new physical vapor deposition (PVD) technique that allows the production of amorphous samples with controlled chemical and morphological characteristics. In particular, this technique was developed to grow uniform or microstructured layers of Mg-Fe amorphous silicates (olivine or pyroxene) that are materials of wide interest for laboratory experiments. We discuss the first results that were achieved by applying this new synthesis method. The layers were studied by combining infrared spectroscopy, scanning electron microscopy, and X-ray spectroscopy. The X-ray microscopy was used for the first time to characterize the internal structure of the grains in these synthetic samples. Finally, future improvements of the technique and foreseen applications are discussed.

  8. Dual-Layer Nanostructured Flexible Thin-Film Amorphous Silicon Solar Cells with Enhanced Light Harvesting and Photoelectric Conversion Efficiency.

    Science.gov (United States)

    Lin, Yinyue; Xu, Zhen; Yu, Dongliang; Lu, Linfeng; Yin, Min; Tavakoli, Mohammad Mahdi; Chen, Xiaoyuan; Hao, Yuying; Fan, Zhiyong; Cui, Yanxia; Li, Dongdong

    2016-05-01

    Three-dimensional (3-D) structures have triggered tremendous interest for thin-film solar cells since they can dramatically reduce the material usage and incident light reflection. However, the high aspect ratio feature of some 3-D structures leads to deterioration of internal electric field and carrier collection capability, which reduces device power conversion efficiency (PCE). Here, we report high performance flexible thin-film amorphous silicon solar cells with a unique and effective light trapping scheme. In this device structure, a polymer nanopillar membrane is attached on top of a device, which benefits broadband and omnidirectional performances, and a 3-D nanostructure with shallow dent arrays underneath serves as a back reflector on flexible titanium (Ti) foil resulting in an increased optical path length by exciting hybrid optical modes. The efficient light management results in 42.7% and 41.7% remarkable improvements of short-circuit current density and overall efficiency, respectively. Meanwhile, an excellent flexibility has been achieved as PCE remains 97.6% of the initial efficiency even after 10 000 bending cycles. This unique device structure can also be duplicated for other flexible photovoltaic devices based on different active materials such as CdTe, Cu(In,Ga)Se2 (CIGS), organohalide lead perovskites, and so forth. PMID:27052357

  9. Carbohydrate polymers in amorphous states: an integrated thermodynamic and nanostructural investigation.

    Science.gov (United States)

    Kilburn, Duncan; Claude, Johanna; Schweizer, Thomas; Alam, Ashraf; Ubbink, Job

    2005-01-01

    The effect of water on the structure and physical properties of amorphous polysaccharide matrices is investigated by combining a thermodynamic approach including pressure- and temperature-dependent dilatometry with a nanoscale analysis of the size of intermolecular voids using positron annihilation lifetime spectroscopy. Amorphous polysaccharides are of interest because of a number of unusual properties which are likely to be related to the extensive hydrogen bonding between the carbohydrate chains. Uptake of water by the carbohydrate matrices leads to a strong increase in the size of the holes between the polymer chains in both the glassy and rubbery states while at the same time leading to an increase in matrix free volume. Thermodynamic clustering theory indicates that, in low-moisture carbohydrate matrices, water molecules are closely associated with the carbohydrate chains. Based on these observations, we propose a novel model of plasticization of carbohydrate polymers by water in which the water dynamically disrupts chains the hydrogen bonding between the carbohydrates, leading to an expansion of the matrix originating at the nanolevel and increasing the number of degrees of freedom of the carbohydrate chains. Consequently, even in the glassy state, the uptake of water leads to increased rates of matrix relaxation and mobility of small permeants. In contrast, low-molecular weight sugars plasticize the carbohydrate matrix without appreciably changing the structure and density of the rubbery state, and their role as plasticizer is most likely related to a reduction of the number of molecular entanglements. The improved molecular packing in glassy matrices containing low molecular weight sugars leads to a higher matrix density, explaining, despite the lower glass transition temperature, the reduced mobility of small permeants in such matrices. PMID:15762653

  10. Advanced light sculpting for contemporary biophotonics

    DEFF Research Database (Denmark)

    Glückstad, Jesper; Palima, Darwin; Villangca, Mark Jayson;

    , structured illumination, optical security, parallel laser marking and recently in contemporary biophotonics applications such as for real-­‐time parallel two-­‐photon optogenetics and neurophotonics. Our most recent GPC light sculpting developments geared towards these applications will be presented. This......Our proprietary Generalized Phase Contrast (GPC) method is a light efficient approach for generating speckle-­‐free contiguous optical distributions using binary-­‐only or analog spatial phase modulation. It has been used in applications such as optical trapping and manipulation, active microscopy...

  11. Photo-induced oxidation and amorphization of trigonal tellurium: A means to engineer hybrid nanostructures and explore glass structure under spatial confinement

    International Nuclear Information System (INIS)

    Controlled photo-induced oxidation and amorphization of elemental trigonal tellurium are achieved by laser irradiation at optical wavelengths. These processes are monitored in situ by time-resolved Raman scattering and ex situ by electron microscopies. Ultrathin TeO2 films form on Te surfaces, as a result of irradiation, with an interface layer of amorphous Te intervening between them. It is shown that irradiation, apart from enabling the controllable transformation of bulk Te to one-dimensional nanostructures, such as Te nanotubes and hybrid core-Te/sheath-TeO2 nanowires, causes also a series of light-driven (athermal) phase transitions involving the crystallization of the amorphous TeO2 layers and its transformation to a multiplicity of crystalline phases including the γ-, β-, and α-TeO2 crystalline phases. The kinetics of the above photo-induced processes is investigated by Raman scattering at various laser fluences revealing exponential and non-exponential kinetics at low and high fluence, respectively. In addition, the formation of ultrathin (less than 10 nm) layers of amorphous TeO2 offers the possibility to explore structural transitions in 2D glasses by observing changes in the short- and medium-range structural order induced by spatial confinement.

  12. Biophotonics: Spectroscopy, Imaging, Sensing, and Manipulation

    CERN Document Server

    Bartolo, Baldassare Di

    2011-01-01

    This volume describes an impressive array of the current photonic-related technologies being used in the investigation of biological systems. The topics include various types of microscopy (fluorescence correlation microscopy, two-photon microscopy), sensitive detection of biological molecules, nano-surgery techniques, fluorescence resonance energy transfer, nano-plasmonics, terahertz spectroscopy, and photosynthetic energy conversion. The emphasis is on the physical principles behind each technique, and on examining the advantages and limitations of each.The book begins with an overview by Paras Prasad, a leader in the field of biophotonics, of several important optical techniques currently used for studying biological systems. In the subsequent chapters these techniques are discussed in depth, providing the reader with a detailed understanding of the basic physical principles at work. An excellent treatment of terahertz spectroscopy demonstrates how photonics is being extended beyond the visible region. Rec...

  13. High cycle fatigue behavior of a nanostructured composite produced via extrusion of amorphous Al89Gd7Ni3Fe1 alloy powders

    International Nuclear Information System (INIS)

    A nanostructured composite Al89Gd7Ni3Fe1 alloy was created by extruding atomized amorphous Al89Gd7Ni3Fe1 powders at different extrusion ratios (ER = 5:1, 10:1, 20:1). The microstructures and mechanical properties produced were examined with special attention given to the high cycle fatigue properties. High cycle fatigue tests were conducted at room temperature under three-point bending at a stress ratio R = 0.1. Increasing the extrusion ratio (ER) improved the hardness, bend strength, and fatigue behavior, with alloys extruded at higher ER exhibiting bend strengths exceeding 1000 MPa and high cycle fatigue behavior well in excess of conventional aluminum alloys. The results obtained are compared to conventional aluminum alloys and particulate reinforced composites.

  14. Nanoplasmonic structures for biophotonic applications: SERS overview

    International Nuclear Information System (INIS)

    Various nanoplasmonic devices were fabricated using top-down method such as electron beam lithography, electroplating and focused ion beam techniques. These substrates were investigated after depositing the molecules from dye to protein, using chemisorptions techniques. Theoretical simulations were also performed on these model nanostructures in order to understand the electrical field distribution. Furthermore, the future prospects of these nanostructures were also mentioned in this report. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Biological Electric Fields and Rate Equations for Biophotons

    CERN Document Server

    Alvermann, M; Swain, J; Widom, A

    2014-01-01

    Ultraweak bioluminescence - the emission of biophotons - remains an experimentally well-established, but theoretically poorly understood phenomenon. This paper presents several related investigations into the physical process of both spontaneous biophoton emission and delayed luminescence. Since light intensities depend upon the modulus squared of their corresponding electric fields we first make some general estimates about the inherent electric fields within various biological systems. Since photon emission from living matter following an initial excitation ("delayed luminescence") typically does not follow a simple exponential decay law after excitation we discuss such non-exponential decays from a general theoretical perspective and argue that they are often to be expected and why. We then discuss the dynamics behind some nonlinear rate equations, connecting them both to biological growth rates and biophoton emission rates, noting a possible connection with cancer. We then return to non-exponential decay ...

  16. Biophotonics: Optical Science and Engineering for the 21st Century

    Science.gov (United States)

    Shen, Xun; van Wijk, Roeland

    It is now well established that all living systems emit a weak but permanent photon flux in the visible and ultraviolet range. This biophoton emission is correlated with many, if not all, biological and physiological functions. There are indications of a hitherto-overlooked information channel within the living system. Biophotons may trigger chemical reactivity in cells, growth control, differentiation and intercellular communication, i.e. biological rhythms. The basic experimental and theoretical framework as well as the technical problems and the wide field of applications in the biotechnical, biomedical engineering, engineering, medicine, pharmacology, environmental science and basic science fields are presented in this book.

  17. Development of a biophotonics option within a photonics technology degree program

    Science.gov (United States)

    Gellman, Joel; Vasan, Srini; Hall, Robert; Goodwin, Don; Matthews, Dennis; Molinaro, Marco; Shackelford, James F.

    2005-10-01

    Albuquerque Technical Vocational Institute (TVI) has developed a collaboration with the National Science Foundation (NSF) Center for Biophotonics Science and Technology (CBST) headquartered at the University of California, Davis in order to develop a transportable biophotonics curriculum for community colleges. A "Biophotonics Option" has been developed within the well-established Photonics Technology Degree program at TVI, centered on two elective courses ("Introduction to Biophotonics" and "Biophotonics Applications"). In addition, TVI is a part of the "Albuquerque Model" that involves exposure to photonics education from the middle school level through graduate education at the University of New Mexico.

  18. Effect of exogenous hydrogen peroxide on biophoton emission from radish root cells.

    Science.gov (United States)

    Rastogi, Anshu; Pospísil, Pavel

    2010-01-01

    Biophotons spontaneously emitted from radish root cells were detected using highly sensitive photomultiplier tube. Freshly isolated radish root cells exhibited spontaneous photon emission of about 4 counts s(-1). Addition of hydrogen peroxide to the cells caused significant enhancement in biophoton emission to about 500 counts s(-1). Removal of molecular oxygen using glucose/glucose oxidase system and scavengering of reactive oxygen species by reducing agents such are sodium ascorbate and cysteine completely diminished biophoton emission. Spectral analysis of the hydrogen peroxide-induced biophoton emission indicates that biophotons are emitted mainly in green-red region of the spectra. The data provided by electron paramagnetic resonance spin-trapping technique showed that formation of singlet oxygen observed after addition of H2O2 correlates with enhancement in biophoton emission. These observations provide direct evidence that singlet oxygen is involved in biophoton emission from radish root cells. PMID:20106674

  19. Functionalized 2PP structures for the BioPhotonics Workstation

    DEFF Research Database (Denmark)

    Matsuoka, Tomoyo; Nishi, Masayuki; Sakakura, Masaaki;

    2011-01-01

    In its standard version, our BioPhotonics Workstation (BWS) can generate multiple controllable counter-propagating beams to create real-time user-programmable optical traps for stable three-dimensional control and manipulation of a plurality of particles. The combination of the platform with...

  20. Bio-optofluidics and biophotonics at the cellular level

    DEFF Research Database (Denmark)

    Bañas, Andrew Rafael; Palima, Darwin; Tauro, Sandeep; Pedersen, Finn; Glückstad, Jesper

    2012-01-01

    We present ongoing research and development activities for constructing a compact next generation BioPhotonics Workstation and a Bio-optofluidic Cell Sorter (cell-BOCS) for all-optical micro-manipulation platforms utilizing low numerical aperture beam geometries. Unlike conventional high NA optic...

  1. FDTD Modeling of Nano- and Bio-Photonic Imaging

    DEFF Research Database (Denmark)

    Tanev, Stoyan; Tuchin, Valery; Pond, James

    2010-01-01

    address newly emerging problems and not so much on its mathematical formulation. We will first discuss the application of a traditional formulation of the FDTD approach to the modeling of sub-wavelength photonics structures. Next, a modified total/scattered field FDTD approach will be applied to the...... modeling of biophotonics applications including Optical Phase Contrast Microscope (OPCM) imaging of cells containing gold nanoparticles (NPs) as well as its potential application as a modality for in vivo flow cytometry configurations....

  2. Developing a compact and portable BioPhotonics Workstation

    OpenAIRE

    Bañas, Andrew Rafael; Tauro, Sandeep; Palima, Darwin; Glückstad, Jesper

    2011-01-01

    We will outline the specifications of a portable Biophotonics Workstation we recently have developed that utilizes high-speed spatial light modulation to generate an array of rapidly reconfigurable laser-traps making 3D real-time optical manipulation of advanced structures possible with the use of joysticks or gaming devices. The fabrication of microstructures with nanometer-sized features, for example a nano-needle, coupled with the real-time user-interactive optical control allows a user to...

  3. Role of Inelastic Electron–Phonon Scattering in Electron Transport through Ultra-Scaled Amorphous Phase Change Material Nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jie; Xu, Xu; Anantram, M.P.

    2014-09-01

    The electron transport through ultra-scaled amorphous phase change material (PCM) GeTe is investigated by using ab initio molecular dynamics, density functional theory, and non-equilibrium Green’s function, and the inelastic electron–phonon scattering is accounted for by using the Born approximation. It is shown that, in ultra-scaled PCM device with 6 nm channel length, < 4 % of the energy carried by the incident electrons from the source is transferred to the atomic lattice before reaching the drain, indicating that the electron transport is largely elastic. Our simulation results show that the inelastic electron–phonon scattering, which plays an important role to excite trapped electrons in bulk PCM devices, exerts very limited influence on the current density value and the shape of current–voltage curve of ultra-scaled PCM devices. The analysis reveals that the Poole–Frenkel law and the Ohm’s law, which are the governing physical mechanisms of the bulk PCM devices, cease to be valid in the ultra-scaled PCM devices.

  4. Structure-­mediated nano-­biophotonics

    DEFF Research Database (Denmark)

    Glückstad, Jesper; Villangca, Mark Jayson; Bañas, Andrew Rafael;

    2015-01-01

    The synergy between photonics, nanotechnology and biotechnology is spawning the emerging fields of nano-biotechnology and nano-biophotonics. Photonic innovations already hurdle the diffraction barrier for imaging with nanoscopic resolutions. However, scientific hypothesis testing demands tools, not...... only for observing nanoscopic phenomena, but also for reaching into and manipulating nanoscale constituents in this domain. This report is two- fold desribing the new use of proprietary strongholds we currently are establishing at DTU Fotonik on new means of sculpting of both light and matter for bio...

  5. Lunisolar tidal synchronism with biophoton emission during intercontinental wheat-seedling germination tests

    Czech Academy of Sciences Publication Activity Database

    Gallep, C.M.; Moraes, T.A.; Červinková, Kateřina; Cifra, Michal; Katsumata, M.; Barlow, P. W.

    2014-01-01

    Roč. 9, č. 3 (2014), e28671. ISSN 1559-2324 Institutional support: RVO:67985882 Keywords : Biophoton emission * Chronobiology * Germination Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  6. Biophotons, coherence and photocount statistics: a critical review

    CERN Document Server

    Cifra, Michal; Nerudová, Michaela; Kučera, Ondřej

    2015-01-01

    Biological samples continuously emit ultra-weak photon emission (UPE, or "biophotons") which stems from electronic excited states generated chemically during oxidative metabolism and stress. Thus, UPE can potentially serve as a method for non-invasive diagnostics of oxidative processes or, if discovered, also of other processes capable of electron excitation. While the fundamental generating mechanisms of UPE are fairly elucidated together with their approximate ranges of intensities and spectra, statistical properties of UPE is still a highly challenging topic. Here we review claims about nontrivial statistical properties of UPE, such as coherence and squeezed states of light. After introduction to the necessary theory, we categorize the experimental works of all authors to those with solid, conventional interpretation and those with unconventional and even speculative interpretation. The conclusion of our review is twofold; while the phenomenon of UPE from biological systems can be considered experimentally...

  7. Counter-propagating patterns in the BioPhotonics Workstation

    DEFF Research Database (Denmark)

    Palima, Darwin; Lindballe, T.; Kristensen, M.V.;

    2010-01-01

    stable three-dimensional manipulation of multiple particles. In this work, we analyze counter-propagating shaped-beam traps that depart from this conventional geometry. We show that projecting shaped beams with separation distances previously considered axially unstable can, in fact, enhance the trap by......The counter-propagating geometry opens an extra degree of freedom for shaping light while subsuming single-sided illumination as a special case (i.e., one beam set turned off). In its conventional operation, our BioPhotonics Workstation (BWS) uses symmetric, co-axial counter-propagating beams for...... improving axial and transverse trapping stiffness. We also show interesting results of trapping and micromanipulation experiments that combine optical forces with fluidic forces. These results hint about the rich potential of using patterned counter-propagating beams for optical trapping and manipulation...

  8. Efficient detection of internal infestation in wheat based on biophotonics.

    Science.gov (United States)

    Shi, Weiya; Jiao, Keke; Liang, Yitao; Wang, Feng

    2016-02-01

    In the process of grain storage, there are many losses of grain quantity and quality for the sake of insects. As a result, it is necessary to find a rapid and economical method for detecting insects in the grain. The paper innovatively proposes a model of detecting internal infestation in wheat by combining pattern recognition and BioPhoton Analytical Technology (BPAT). In this model, the spontaneous ultraweak photons emitted from normal and insect-contaminated wheat are firstly measured respectively. Then, position, distribution and morphological characteristics can be extracted from the measuring data to construct wheat feature vector. Backpropagation (BP) neural network based on genetic algorithm is employed to take decision on whether wheat kernel has contaminated by insects. The experimental results show that the proposed model can differentiate the normal wheat from the insect-contaminated one at an average accuracy of 95%. The model can also offer a novel thought for detecting internal infestation in the wheat. PMID:26774558

  9. Physics and engineering of compact quantum dot-based lasers for biophotonics

    CERN Document Server

    Rafailov, Edik U

    2013-01-01

    Written by a team of European experts in the field, this book addresses the physics, the principles, the engineering methods, and the latest developments of efficient and compact ultrafast lasers based on novel quantum-dot structures and devices, as well as their applications in biophotonics. Recommended reading for physicists, engineers, students and lecturers in the fields of photonics, optics, laser physics, optoelectronics, and biophotonics.

  10. Functionalizing 2PP-fabricated microtools for optical manipulation on the BioPhotonics Workstation

    DEFF Research Database (Denmark)

    Matsuoka, Tomoyo; Nishi, Masayuki; Sakakura, Masaaki;

    Functionalization of the structures fabricated by two-photon polymerization was achieved by coating them with sol-gel materials, which contain calcium indicators. The structures are expected to work potentially as nano-sensors on the BioPhotonics Workstation.......Functionalization of the structures fabricated by two-photon polymerization was achieved by coating them with sol-gel materials, which contain calcium indicators. The structures are expected to work potentially as nano-sensors on the BioPhotonics Workstation....

  11. Detecting presence of cardiovascular disease through mitochondria respiration as depicted through biophotonic emission

    OpenAIRE

    Nancy R. Rizzo; Hank, Nicole C.; Jian Zhang

    2016-01-01

    Aims: Increased production of reactive oxygen species (ROS) in mitochondria, play an important role in the cardiovascular system. Furthermore, oxidative metabolism of mitochondria comprised of biophoton emissions, are linked to ROS and oxidative stress. In this review we investigated the association between the ability of ClearViewTM system (ClearView) to indicate the presence or absence of cardiovascular disease through mitochondria respiration as depicted through biophotonic emission. Me...

  12. Detecting presence of cardiovascular disease through mitochondria respiration as depicted through biophotonic emission

    OpenAIRE

    Nancy R. Rizzo; Hank, Nicole C.; Zhang, Jian

    2015-01-01

    Aims Increased production of reactive oxygen species (ROS) in mitochondria, play an important role in the cardiovascular system. Furthermore, oxidative metabolism of mitochondria comprised of biophoton emissions, are linked to ROS and oxidative stress. In this review we investigated the association between the ability of ClearViewTM system (ClearView) to indicate the presence or absence of cardiovascular disease through mitochondria respiration as depicted through biophotonic emission. Method...

  13. Development of a biophotonics technician-training program: directions for the 21st Century

    Science.gov (United States)

    Shackelford, James F.; Gellman, Joel; Vasan, Srini; Hall, Robert A.; Goodwin, Don E.; Molinaro, Marco; Matthews, Dennis

    2005-06-01

    Albuquerque Technical Vocational Institute (TVI) is collaborating with the National Science Foundation (NSF) funded Center for Biophotonics Science and Technology (CBST) headquartered at the University of California, Davis in order to develop a biophotonics curriculum for community colleges nationwide. TVI began the formal collaboration to bring about critically needed training and education that will ultimately create new jobs and employment opportunities in the field of biophotonics. "Biophotonics" is the science of generating and harnessing light to detect, image and manipulate biological materials. CBST chose TVI as a partner because of the Institute's current high-level photonics and biotechnology programs. In addition, TVI is a part of the "Albuquerque Model" that involves exposure to photonics education from the middle school level through graduate education at the University of New Mexico. Three middle schools feed into the West Mesa High School Photonics Academy, whose students then move on to TVI for advanced training. CBST brings together scientists, industry, educators and the community to research and develop applications for biophotonics. Roughly 100 researchers-including physical scientists, life scientists, physicians and engineers from UC Davis, Lawrence Livermore National Laboratory, UC Berkeley, UC San Francisco, Alabama A&M University, Stanford University, University of Texas at San Antonio, Fisk University and Mills College-are collaborating in this rapidly developing area of research. Applications of biophotonics range from using light to image or selectively treat tumors, to sequencing DNA and identifying single biomolecules within cells.

  14. Biophotonics: a new link between physical and life sciences

    International Nuclear Information System (INIS)

    Photonics is the science of generating, manipulating and measuring light (ultraviolet-UV, visible-vis and infrared-IR). It involves ultrafast processes (lasers producing pulses -15), ultrahigh power densities (>1012 W.cm-2) and ultrahigh information density (1015 bits per cm3 of optical storage material). Photonic technologies have many applications, including optical fiber communications, laser precision machining, materials analysis, remote sensing, and optical information storage. The enabling technologies include lasers and other light sources, optical fibers, and photodetectors and detector arrays. These are ubiquitous in everyday life, from the CD player to the supermarket checkout scanner, to the digital camera. Biophotonics is a rapidly developing field that applies photonics in exploiting the interaction of light with tissues, cells and biomolecules for biomedical research and clinical medicine. Although the therapeutic use of light was known to the ancient Egyptians, it has only been in the last few decades that the key technologies and sufficient understanding of optical biophysics have become available to enable light-based therapeutic and diagnostic in vivo techniques to be developed. Similarly, although the optical microscope was invented by Leeuwenhoek over 300 years ago, there is now a renaissance in optical micro-imaging of cells and tissues based on different optical interactions, and a rapidly expanding range of other analytic optical tools for biotechnology applications. Therapeutic applications exploit the effect of light on tissues, cells and biomolecules. That is, optical energy is absorbed by specific molecules and results in biophysical and/or biochemical changes. Conversely, analytic applications and in vivo clinical diagnostics exploit the effect of tissues, cells and biomolecules on light, i.e., the interactions cause changes in wavelength, spatial or temporal distribution, phase, or polarization of the light that give information on the

  15. Study on Spectrum Estimation in Biophoton Emission Signal Analysis of Wheat Varieties

    Directory of Open Access Journals (Sweden)

    Yitao Liang

    2014-01-01

    Full Text Available The photon emission signal in visible range (380 nm–630 nm was measured from various wheat kernels by means of a low noise photomultiplier system. To study the features of the photon emission signal, the spectrum estimation method of the photon emission signal is described for the first time. The biophoton emission signal, belonging to four varieties of wheat, is analyzed in time domain and frequency domain. It shows that the intensity of the biophoton emission signal for four varieties of wheat kernels is relatively weak and has dramatic changes over time. Mean and mean square value are obviously different in four varieties; the range was, respectively, 3.7837 and 74.8819. The difference of variance is not significant. The range is 1.1764. The results of power spectrum estimation deduced that the biophoton emission signal is a low frequency signal, and its power spectrum is mostly distributed in the frequency less than 0.1 Hz. Then three parameters, which are spectral edge frequency, spectral gravity frequency, and power spectral entropy, are adopted to explain the features of the kernels’ spontaneous biophoton emission signal. It shows that the parameters of the spontaneous biophoton emission signal for different varieties of wheat are similar.

  16. Advances in Photonics Design and Modeling for Nano- and Bio-photonics Applications

    DEFF Research Database (Denmark)

    Tanev, Stoyan

    2010-01-01

    In this invited paper we focus on the discussion of two recent unique applications of the Finite-Difference Time-Domain (FDTD) simulation method to the design and modeling of advanced nano- and bio-photonic problems. We will first discuss the application of a traditional formulation of the FDTD...... approach to the modeling of sub-wavelength photonics structures. Next, a modified total/scattered field FDTD approach will be applied to the modeling of biophotonics applications including Optical Phase Contrast Microscope (OPCM) imaging of cells containing gold nanoparticles (NPs) as well as its potential...

  17. 77 FR 19744 - Advanced BioPhotonics, Inc., Advanced Viral Research Corp., Brantley Capital Corp., Brilliant...

    Science.gov (United States)

    2012-04-02

    ... Technologies Corporation, 4C Controls, Inc., and 2-Track Global, Inc.; Order of Suspension of Trading March 29... information concerning the securities of Advanced BioPhotonics, Inc. because it has not filed any periodic... Research Corp. because it has not filed any periodic reports since the period ended September 30, 2008....

  18. Using biophotonics to study signaling mechanisms in a single living cell

    CERN Document Server

    Chang, Donald C

    2014-01-01

    To illustrate the power of the biophysical approach in solving important problems in life science, I present here one of our current research projects as an example. We have developed special biophotonic techniques to study the dynamic properties of signaling proteins in a single living cell. Such a study allowed us to gain new insight into the signaling mechanism that regulates programmed cell death.

  19. Developing a compact and portable BioPhotonics Workstation

    DEFF Research Database (Denmark)

    Bañas, Andrew Rafael; Tauro, Sandeep; Palima, Darwin;

    joysticks or gaming devices. The fabrication of microstructures with nanometer-sized features, for example a nano-needle, coupled with the real-time user-interactive optical control allows a user to robotically actuate appended nanostructures depending on their intended function. These micro......-platforms carrying nanotools are seen to have potential uses in a variety of micro-biological experiments. Optically actuated nanoneedles may be functionalized or directly used to approach and probe cells at specific locations or even to assist the separation of dividing cells, among a host of other functions useful...

  20. The BioPhotonics Workstation: from university research to commercial prototype

    OpenAIRE

    Glückstad, Jesper

    2011-01-01

    I will outline the specifications of the compact BioPhotonics Workstation we recently have developed that utilizes high-speed spatial light modulation to generate an array of reconfigurable laser-traps making 3D real-time optical manipulation of advanced structures possible with the use of joysticks or gaming devices. The fabrication of microstructures with sub-micron features coupled with the real-time user-interactive optical control allows a user to robotically actuate appended structures ...

  1. Capturing structure and function in an embryonic heart with Biophotonic tools

    Directory of Open Access Journals (Sweden)

    Ganga eKarunamuni

    2014-09-01

    Full Text Available Disturbed cardiac function (flow, excitation, contraction, calcium transients at an early stage of development has been shown to correlate with and may lead to cellular/molecular, functional and structural cardiac anomalies at later stages culminating in the congenital heart defects (CHDs that present at birth. It is not surprising that cardiac function, which drives embryonic and extraembryonic circulation, is also connected to neural and placental development. While our knowledge of molecular and cellular steps in cardiac development is growing rapidly, our understanding of the role of cardiovascular function in the embryo is still rudimentary. One reason for the scanty information in this area is that the tools to study early cardiac function are limited. Recently developed and adapted Biophotonic tools may overcome the challenges of studying the tiny fragile beating heart. In this chapter, the strengths and limitations of Biophotonic tools will be described with emphasis on Optical Coherence Tomography (OCT. OCT can be used for detailed structural and functional studies of the tubular and looping avian embryo heart under physiological conditions. The same hearts can be subsequently rapidly and quantitatively phenotyped at a later stage using OCT. When combined with other tools such as Optimal Mapping (OM and Optical Pacing (OP, OCT has the potential to reveal in spatial and temporal detail the biophysical changes that can potentially impact mechanotransduction pathways. This information may provide better explanations for the etiology of the CHDs when interwoven with our understanding of the multiple molecular pathways that have been described to be involved. Examples of application of these tools to study the etiology of CHDs are presented. Directions for future directions and advances in the use of Biophotonic tools are discussed.

  2. Advances in the FDTD design and modeling of nano- and bio-photonics applications

    DEFF Research Database (Denmark)

    Tanev, Stoyan; Tuchin, Valery; Cheben, Pavel;

    2011-01-01

    address newly emerging problems and not so much on its mathematical formulation. We will first discuss the application of a traditional formulation of the FDTD approach to the modeling of sub-wavelength photonics structures. Next, a modified total/scattered field FDTD approach will be applied to the...... modeling of biophotonics applications including optical phase contrast microscope (OPCM) imaging of cells containing gold nanoparticles (NPs) as well as its potential application as a modality for in vivo flow cytometry configurations. The conclusion provides a justification for the selection of the two...

  3. Special issue on Laser Biophotonics, dedicated to the seventieth birthday of V.V. Tuchin

    Science.gov (United States)

    Priezzhev, A. V.; Bashkatov, A. N.; Genina, E. A.

    2014-07-01

    Prominent Researcher and Educator, Honoured Scientist of the Russian Federation, Professor Valery V. Tuchin celebrated his seventieth birthday this year. V.V. Tuchin heads the Department of Optics and Biophotonics at N.G. Chernyshevsky Saratov State University and the Laboratory of Laser Diagnostics of Technical and Living Systems at the Institute of Precise Mechanics and Control of the Russian Academy of Sciences. He is a Vice-President of the Russian Photobiology Society. V.V. Tuchin is widely known for his achievements in optics of biological tissues, in developing methods of optical and laser measurements in biomedicine and nanobiophotonics, and in many other fields.

  4. Nanostructured superconductors

    CERN Document Server

    Moshchalkov, Victor V

    2011-01-01

    The main focus of the book is to present the effects of nanostructuring on superconducting critical parameters. Optimizing systematically flux and condensate confinement in various nanostructured superconductors, ranging from single nano-cells to their hu

  5. Matched filtering Generalized Phase Contrast using binary phase for dynamic spot- and line patterns in biophotonics and structured lighting

    DEFF Research Database (Denmark)

    Bañas, Andrew Rafael; Aabo, Thomas; Palima, Darwin;

    2013-01-01

    This work discusses the use of matched filtering Generalized Phase Contrast (mGPC) as an efficient and cost-effective beam shaper for applications such as in biophotonics, optical micromanipulation, microscopy and two-photon polymerization. The theoretical foundation of mGPC is described as a...

  6. Monolithically integrated biophotonic lab-on-a-chip for cell culture and simultaneous pH monitoring

    NARCIS (Netherlands)

    Munoz-Berbel, Xavier; Rodriguez-Rodriguez, Rosalia; Vigues, Nuria; Demming, Stefanie; Mas, Jordi; Buettgenbach, Stephanus; Verpoorte, Elisabeth; Ortiz, Pedro; Llobera, Andreu

    2013-01-01

    A poly(dimethylsiloxane) biophotonic lab-on-a-chip (bioPhLoC) containing two chambers, an incubation chamber and a monitoring chamber for cell retention/proliferation and pH monitoring, respectively, is presented. The bioPhLoC monolithically integrates a filter with 3 mu m high size-exclusion microc

  7. Highly Reversible Lithium Storage in Nanostructured Silicon

    OpenAIRE

    Graetz, J.; Ahn, C. C.; Yazami, R.; Fultz, B.

    2003-01-01

    Anode materials of nanostructured silicon have been prepared by physical vapor deposition and characterized using electrochemical methods. The electrodes were prepared in thin-film form as nanocrystalline particles (12 nm mean diameter) and as continuous amorphous thin films (100 nm thick). The nanocrystalline silicon exhibited specific capacities of around 1100 mAh/g with a 50% capacity retention after 50 cycles. The amorphous thin-film electrodes exhibited initial capacities of 3500 mAh/g w...

  8. Thermal properties of amorphous/crystalline silicon superlattices.

    Science.gov (United States)

    France-Lanord, Arthur; Merabia, Samy; Albaret, Tristan; Lacroix, David; Termentzidis, Konstantinos

    2014-09-01

    Thermal transport properties of crystalline/amorphous silicon superlattices using molecular dynamics are investigated. We show that the cross-plane conductivity of the superlattices is very low and close to the conductivity of bulk amorphous silicon even for amorphous layers as thin as ≃ 6 Å. The cross-plane thermal conductivity weakly increases with temperature which is associated with a decrease of the Kapitza resistance with temperature at the crystalline/amorphous interface. This property is further investigated considering the spatial analysis of the phonon density of states in domains close to the interface. Interestingly, the crystalline/amorphous superlattices are shown to display large thermal anisotropy, according to the characteristic sizes of elaborated structures. These last results suggest that the thermal conductivity of crystalline/amorphous superlattices can be phonon engineered, providing new directions for nanostructured thermoelectrics and anisotropic materials in thermal transport. PMID:25105883

  9. Irradiation-Induced Nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Birtcher, R.C.; Ewing, R.C.; Matzke, Hj.; Meldrum, A.; Newcomer, P.P.; Wang, L.M.; Wang, S.X.; Weber, W.J.

    1999-08-09

    This paper summarizes the results of the studies of the irradiation-induced formation of nanostructures, where the injected interstitials from the source of irradiation are not major components of the nanophase. This phenomena has been observed by in situ transmission electron microscopy (TEM) in a number of intermetallic compounds and ceramics during high-energy electron or ion irradiations when the ions completely penetrate through the specimen. Beginning with single crystals, electron or ion irradiation in a certain temperature range may result in nanostructures composed of amorphous domains and nanocrystals with either the original composition and crystal structure or new nanophases formed by decomposition of the target material. The phenomenon has also been observed in natural materials which have suffered irradiation from the decay of constituent radioactive elements and in nuclear reactor fuels which have been irradiated by fission neutrons and other fission products. The mechanisms involved in the process of this nanophase formation are discussed in terms of the evolution of displacement cascades, radiation-induced defect accumulation, radiation-induced segregation and phase decomposition, as well as the competition between irradiation-induced amorphization and recrystallization.

  10. Superhydrophilic nanostructure

    Science.gov (United States)

    Mao, Samuel S; Zormpa, Vasileia; Chen, Xiaobo

    2015-05-12

    An embodiment of a superhydrophilic nanostructure includes nanoparticles. The nanoparticles are formed into porous clusters. The porous clusters are formed into aggregate clusters. An embodiment of an article of manufacture includes the superhydrophilic nanostructure on a substrate. An embodiment of a method of fabricating a superhydrophilic nanostructure includes applying a solution that includes nanoparticles to a substrate. The substrate is heated to form aggregate clusters of porous clusters of the nanoparticles.

  11. Growth Control and Biophoton Radiation by Plant Hormones in Red Bean

    Science.gov (United States)

    Kai, Shoichi; Moriya, Tomoyuki; Fujimoto, Tokio

    1995-12-01

    The growth kinetics of seeds of red beans ( Phaseolus angularis ) was investigated by externally adding various hormones (gibberellin (GA3)), abscisic acid (ABA) and indole acetic acid (IAA)) during germination. For root growth of red beans, GA3 always acted as an activator while ABA as an inhibitor. IAA was both an activator and an inhibitor depending on its concentration. Root growth could be described by a stochastic logistic equation. The hormone concentration dependences of coefficients of the equation were determined. The hormone influences on biophoton radiation were also investgated. With GA3, the intensity of spontaneous bioluminescence increased with time and showed two strong radiation periods, in which strong localization of bioluminescence was induced. However with ABA and IAA, weaker bioluminescences were observed. The location of the strong radiation induced by GA3 was determined as the growing point near a root cap, by use of a two-dimensional photon counting system.

  12. Frontiers in biophotonics for translational medicine in the celebration of year of light (2015)

    CERN Document Server

    Dinish, U

    2016-01-01

    The present book provides recent developments in various in vivo imaging and sensing techniques such as photo acoustics (PA) imaging and microscopy, ultrasound-PA combined modalities, optical coherence tomography (OCT) and micro OCT, Raman and surface enhanced Raman scattering (SERS), Fluorescence lifetime imaging (FLI) techniques and nanoparticle enabled endoscopy etc. There is also a contributing chapter from leading medical instrumentation company on their view of optical imaging techniques in clinical laparoscopic surgery. The UN proclaimed 2015 as the International Year of Light and Light-based Technologies, emphasizing achievements in the optical sciences and their importance to human beings. In this context, this book focusses on the recent advances in biophotonics techniques primarily focused towards translational medicine contributed by thought leaders who have made cutting edge developments in various photonics techniques.

  13. BioPhotonics Workstation supporting 3D joystick-control of microplatforms [invited

    DEFF Research Database (Denmark)

    Tauro, Sandeep; Palima, Darwin; Perch-Nielsen, Ivan R.; Kelemen, Lóránd; Ormos, Pál; Glückstad, Jesper

    2010-01-01

    handles provides leverage enabling submicron positioning accuracy of the tip. The tip can be joystick positioned in 3D with full rotational freedom, as close to the cell as desired. Using microtools allows experiments on cells without requiring extensive sample preparation. Furthermore, each tip of the...... positioning of several microtools simultaneously near one single cell. The experiments are performed in our BioPhotonics Workstation with counterpropagating beam geometry. This geometry provides a large manipulation area and allows realtime manipulation or a plurality or traps (euITenl1y 100 independently...... reconfigurable traps), facilitating precise control and a rapid response of the optically manipulated microtools • The microtools are prefabricated by two-photon polymerization. The tools consist of a tip with submicron features, connected to three spheres functioning as trapping handles. The separation of...

  14. Monolithic Highly Stable Yb-Doped Femtosecond Fiber Lasers for Applications in Practical Biophotonics

    DEFF Research Database (Denmark)

    Liu, Xiaomin; Lægsgaard, Jesper; Turchinovich, Dmitry

    2012-01-01

    Operational and environmental stability of ultrafast laser systems is critical for their applications in practical biophotonics. Mode-locked fiber lasers show great promise in applications such as supercontinuum sources or multiphoton microscopy systems. Recently, substantial progress has been made...... in the development of all-fiber nonlinear-optical laser control schemes, which resulted in the demonstration of highly stable monolithic, i.e., not containing any free-space elements, lasers with direct fiber-end delivery of femtosecond pulses. This paper provides an overview of the progress in the...... development of such all-fiber mode-locked lasers based on Yb-fiber as gain medium, operating at the wavelength around 1 $\\mu$m, and delivering femtosecond pulses reaching tens of nanojoules of energy....

  15. Ultrafast biophotonics

    CERN Document Server

    Vasa, P

    2016-01-01

    This book presents emerging contemporary optical techniques of ultrafast science which have opened entirely new vistas for probing biological entities and processes. The spectrum reaches from time-resolved imaging and multiphoton microscopy to cancer therapy and studies of DNA damage. The book displays interdisciplinary research at the interface of physics and biology. Emerging topics on the horizon are also discussed, like the use of squeezed light, frequency combs and terahertz imaging as the possibility of mimicking biological systems. The book is written in a manner to make it readily accessible to researchers, postgraduate biologists, chemists, engineers, and physicists and students of optics, biomedical optics, photonics and biotechnology.

  16. Laser biophotonics

    Science.gov (United States)

    Bashkatov, A. N.; Genina, E. A.; Priezzhev, A. V.; Tuchin, V. V.

    2016-06-01

    This issue of Quantum Electronics presents the papers that reflect the state-of-the-art of laser technologies used in biomedical studies and medical practice. Among the new technologies, one can note the methods of correlation and Doppler spectroscopy, as well as THz spectroscopy, in which biologically significant molecules are characterised by specific resonances. The latter topic is considered in the paper by Nazarov et al., where the dielectric function of aqueous solutions of glucose and albumin is studied using pulsed THz spectroscopy.

  17. Shock induced crystallization of amorphous Nickel powders

    Science.gov (United States)

    Cherukara, Mathew; Strachan, Alejandro

    2015-06-01

    Recent experimental work has shown the efficacy of amorphous Ni/crystalline Al composites as energetic materials, with flame velocities twice that of a comparable crystalline Ni/crystalline Al system. Of further interest is the recrystallization mechanisms in the pure amorphous Ni powders, both thermally induced and mechanically induced. We present large-scale molecular dynamics simulations of shock-induced recrystallization in loosely packed amorphous Nickel powders. We study the time dependent nucleation and growth processes by holding the shocked samples at the induced pressures and temperatures for extended periods following the passage of the shock (up to 6 ns). We find that the nanostructure of the recrystallized Ni and time scales of recrystallization are dependent on the piston velocity. At low piston velocities, nucleation events are rare, leading to long incubation times and a relatively coarse nanostructure. At higher piston velocities, local variations in temperature due to jetting phenomena and void collapse, give rise to multiple nucleation events on time scales comparable to the passage of the shock wave, leading to the formation of a fine-grained nanostructure. Interestingly, we observe that the nucleation and growth process occurs in two steps, with the first nuclei crystallizing into the BCC structure, before evolving over time into the expected FCC structure. U.S. Defense Threat Reduction Agency, HDTRA1-10-1-0119 (Program Manager Suhithi Peiris).

  18. Matched filtering Generalized Phase Contrast using binary phase for dynamic spot- and line patterns in biophotonics and structured lighting

    OpenAIRE

    Bañas, Andrew Rafael; Aabo, Thomas; Palima, Darwin; Glückstad, Jesper

    2013-01-01

    This work discusses the use of matched filtering Generalized Phase Contrast (mGPC) as an efficient and cost-effective beam shaper for applications such as in biophotonics, optical micromanipulation, microscopy and two-photon polymerization. The theoretical foundation of mGPC is described as a combination of Generalized Phase Contrast and phase-only correlation. Such an analysis makes it convenient to optimize an mGPC system for different setup conditions. Results showing binary-only phase gen...

  19. MICCAI ´06 - Workshop on Biophotonics Imaging for Diagnostics and Treatment, October 6, 2006 proceedings, 9th MICCAI Conference

    OpenAIRE

    Ersbøll, Bjarne Kjær; Jørgensen, Thomas Martini

    2006-01-01

    Preface: Biophotonics can be defined as the study of the interaction of light with biological material. With the recent advances in biomedical science, our understanding of the mechanisms of human health and disease has extended into the regime of cellular and molecular structure and function. The ability to image, analyze, and manipulate living tissue at this level (and to do so in a minimally- or noninvasive manner) has become essential for continued progress in biomedical research and deve...

  20. The mechanism and properties of bio-photon emission and absorption in protein molecules in living systems

    Science.gov (United States)

    Pang, Xiao-feng

    2012-05-01

    The mechanism and properties of bio-photon emission and absorption in bio-tissues were studied using Pang's theory of bio-energy transport, in which the energy spectra of protein molecules are obtained from the discrete dynamic equation. From the energy spectra, it was determined that the protein molecules could both radiate and absorb bio-photons with wavelengths of effects produced by the infrared light absorbed by the bio-tissues, using the above results. No temperature rise was observed; instead, the absorbed infrared light promoted the vibrations of amides as well the transport of the bio-energy from one place to other in the protein molecules, which changed their conformations. These experimental results, therefore, not only confirmed the validity of the mechanism of bio-photon emission, and the newly developed theory of bio-energy transport mentioned above, but also explained the mechanism and properties of the non-thermal biological effects produced by the absorption of infrared light by the living systems.

  1. Amorphous Computing

    Science.gov (United States)

    Sussman, Gerald

    2002-03-01

    agents constructed by engineered cells, but we have few ideas for programming them effectively: How can one engineer prespecified, coherent behavior from the cooperation of immense numbers of unreliable parts that are interconnected in unknown, irregular, and time-varying ways? This is the challenge of Amorphous Computing.

  2. Amorphous carbon for photovoltaics

    Science.gov (United States)

    Risplendi, Francesca; Grossman, Jeffrey C.

    2015-03-01

    All-carbon solar cells have attracted attention as candidates for innovative photovoltaic devices. Carbon-based materials such as graphene, carbon nanotubes (CNT) and amorphous carbon (aC) have the potential to present physical properties comparable to those of silicon-based materials with advantages such as low cost and higher thermal stability.In particular a-C structures are promising systems in which both sp2 and sp3 hybridization coordination are present in different proportions depending on the specific density, providing the possibility of tuning their optoelectronic properties and achieving comparable sunlight absorption to aSi. In this work we employ density functional theory to design suitable device architectures, such as bulk heterojunctions (BHJ) or pn junctions, consisting of a-C as the active layer material.Regarding BHJ, we study interfaces between aC and C nanostructures (such as CNT and fullerene) to relate their optoelectronic properties to the stoichiometry of aC. We demonstrate that the energy alignment between the a-C mobility edges and the occupied and unoccupied states of the CNT or C60 can be widely tuned by varying the aC density to obtain a type II interface.To employ aC in pn junctions we analyze the p- and n-type doping of a-C focusingon an evaluation of the Fermi level and work function dependence on doping.Our results highlight promising features of aC as the active layer material of thin-film solar cells.

  3. Non-invasive monitoring of Streptococcus pyogenes vaccine efficacy using biophotonic imaging.

    Directory of Open Access Journals (Sweden)

    Faraz M Alam

    Full Text Available Streptococcus pyogenes infection of the nasopharynx represents a key step in the pathogenic cycle of this organism and a major focus for vaccine development, requiring robust models to facilitate the screening of potentially protective antigens. One antigen that may be an important target for vaccination is the chemokine protease, SpyCEP, which is cell surface-associated and plays a role in pathogenesis. Biophotonic imaging (BPI can non-invasively characterize the spatial location and abundance of bioluminescent bacteria in vivo. We have developed a bioluminescent derivative of a pharyngeal S. pyogenes strain by transformation of an emm75 clinical isolate with the luxABCDE operon. Evaluation of isogenic recombinant strains in vitro and in vivo confirmed that bioluminescence conferred a growth deficit that manifests as a fitness cost during infection. Notwithstanding this, bioluminescence expression permitted non-invasive longitudinal quantitation of S. pyogenes within the murine nasopharynx albeit with a detection limit corresponding to approximately 10(5 bacterial colony forming units (CFU in this region. Vaccination of mice with heat killed streptococci, or with SpyCEP led to a specific IgG response in the serum. BPI demonstrated that both vaccine candidates reduced S. pyogenes bioluminescence emission over the course of nasopharyngeal infection. The work suggests the potential for BPI to be used in the non-invasive longitudinal evaluation of potential S. pyogenes vaccines.

  4. Cyclable Condensation and Hierarchical Assembly of Metastable Reflectin Proteins, the Drivers of Tunable Biophotonics.

    Science.gov (United States)

    Levenson, Robert; Bracken, Colton; Bush, Nicole; Morse, Daniel E

    2016-02-19

    Reversible changes in the phosphorylation of reflectin proteins have been shown to drive the tunability of color and brightness of light reflected from specialized cells in the skin of squids and related cephalopods. We show here, using dynamic light scattering, electron microscopy, and fluorescence analyses, that reversible titration of the excess positive charges of the reflectins, comparable with that produced by phosphorylation, is sufficient to drive the reversible condensation and hierarchical assembly of these proteins. The results suggest a two-stage process in which charge neutralization first triggers condensation, resulting in the emergence of previously cryptic structures that subsequently mediate reversible, hierarchical assembly. The extent to which cyclability is seen in the in vitro formation and disassembly of complexes estimated to contain several thousand reflectin molecules suggests that intrinsic sequence- and structure-determined specificity governs the reversible condensation and assembly of the reflectins and that these processes are therefore sufficient to produce the reversible changes in refractive index, thickness, and spacing of the reflectin-containing subcellular Bragg lamellae to change the brightness and color of reflected light. This molecular mechanism points to the metastability of reflectins as the centrally important design principle governing biophotonic tunability in this system. PMID:26719342

  5. Synergistic effect of amorphous carbon coverage and enlarged voltage window on the superior lithium storage performance of nanostructured mesoporous anatase TiO2: Emphasis on interfacial storage phenomena

    International Nuclear Information System (INIS)

    Highlights: • Interconnected agglomerates of nanoparticles are assembled into a porous network. • Both bulk insertion and interfacial storage contribute to the high capacity. • The enlarged voltage window of 0.01–3.0 V is employed firstly. • An ultrathin carbon layer (1 nm thick) helps to avoid the structure instability. • The obtained nanoparticles have a high capacity of 270 mA h g−1 at 300th cycle. - Abstract: Mesoporous anatase TiO2 nanoparticles coated with an ultrathin layer of amorphous carbon are hydrothermally synthesized. Used as an anode material, it achieves a sustained superior lithium storage performance, presenting a high reversible capacity of 270 mA h g−1 up to 300 cycles at a current density of 30 mA h g−1 in an enlarged voltage window of 0.01–3 V, which is firstly adopted for TiO2 anode material. Remarkably, the carbon coated TiO2 nanoparticles can still maintain a capacity of 171 mA h g−1 at 300 mA g−1 after 1000 cycles, and even 93 mA h g−1 at 600 mA g−1 after 1000 cycles. We propose an overall view on the diverse features influencing the electrochemical performance of the high-surface-area mesoporous carbon coated TiO2 nanoparticles and emphasize that the excellent performance is the synergistic result of the enlarged voltage window, which leads to higher interfacial lithium storage, and the uniform amorphous carbon coverage, which not only improves electrical conductivity, minimizes the direct solid-electrolyte interphase (SEI) formation, but also helps to avoid the structure instability arising from the enlargement of the potential window

  6. Electrodeposited nanostructures

    Science.gov (United States)

    Schwarzacher, W.; Attenborough, K.; Michel, A.; Nabiyouni, G.; Meier, J. P.

    1997-01-01

    Electrodeposition may be used to prepare a range of nanostructured materials with interesting magnetic and magnetotransport properties. For example, on annealing, Co-Ni-Cu/Cu alloy superlattices electrodeposited from a single electrolyte show a previously unreported transition from giant magnetoresistance (GMR), to anisotropic magnetoresistance (AMR), and then back to GMR. Superlattice nanowires, electrodeposited in the pores of nuclear track-etched polycarbonate membranes, are another example of an electrodeposited nanostructure. They may be considered as columns of disc-shaped magnetic particles with diameter e.g. 80 nm and thickness e.g. 1 nm separated by non-magnetic material. Here we present evidence for demagnetizing interactions in such samples.

  7. Analytic device including nanostructures

    KAUST Repository

    Di, Fabrizio, E.

    2015-07-02

    A device for detecting an analyte in a sample comprising: an array including a plurality of pixels, each pixel including a nanochain comprising: a first nanostructure, a second nanostructure, and a third nanostructure, wherein size of the first nanostructure is larger than that of the second nanostructure, and size of the second nanostructure is larger than that of the third nanostructure, and wherein the first nanostructure, the second nanostructure, and the third nanostructure are positioned on a substrate such that when the nanochain is excited by an energy, an optical field between the second nanostructure and the third nanostructure is stronger than an optical field between the first nanostructure and the second nanostructure, wherein the array is configured to receive a sample; and a detector arranged to collect spectral data from a plurality of pixels of the array.

  8. Advanced biosensing methodologies developed for evaluating performance quality and safety of emerging biophotonics technologies and medical devices (Conference Presentation)

    Science.gov (United States)

    Ilev, Ilko K.; Walker, Bennett; Calhoun, William; Hassan, Moinuddin

    2016-03-01

    Biophotonics is an emerging field in modern biomedical technology that has opened up new horizons for transfer of state-of-the-art techniques from the areas of lasers, fiber optics and biomedical optics to the life sciences and medicine. This field continues to vastly expand with advanced developments across the entire spectrum of biomedical applications ranging from fundamental "bench" laboratory studies to clinical patient "bedside" diagnostics and therapeutics. However, in order to translate these technologies to clinical device applications, the scientific and industrial community, and FDA are facing the requirement for a thorough evaluation and review of laser radiation safety and efficacy concerns. In many cases, however, the review process is complicated due the lack of effective means and standard test methods to precisely analyze safety and effectiveness of some of the newly developed biophotonics techniques and devices. There is, therefore, an immediate public health need for new test protocols, guidance documents and standard test methods to precisely evaluate fundamental characteristics, performance quality and safety of these technologies and devices. Here, we will overview our recent developments of novel test methodologies for safety and efficacy evaluation of some emerging biophotonics technologies and medical devices. These methodologies are based on integrating the advanced features of state-of-the-art optical sensor technologies and approaches such as high-resolution fiber-optic sensing, confocal and optical coherence tomography imaging, and infrared spectroscopy. The presentation will also illustrate some methodologies developed and implemented for testing intraocular lens implants, biochemical contaminations of medical devices, ultrahigh-resolution nanoscopy, and femtosecond laser therapeutics.

  9. Carbon nanostructures produced through ion irradiation

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Several nanostructures we produced by ion irradiation have been reviewed in this paper. By using ions to irradiate two ultrahigh molecular weight polyethylene targets respectively, it was found that small fullerenes C20 and C26 were grown, adding two members to the fullerene family. Meanwhile, crystalline diamonds also have been produced by Ar+ ions irradiation of graphite. In the experiment of double ions Ni+ and Ar+ irradiation, nanoscale argon bubbles formed. On the other side, when multi-wall carbon nanotubes were irradiated by C+, many MWCNTs evolved to amorphous carbon nanowires and amorphous carbon nanotubes. And there are possible welding in the crossed nanotubes.

  10. Quantitative assessment of biophotonic imaging system performance with phantoms fabricated by rapid prototyping

    Science.gov (United States)

    Wang, Jianting; Coburn, James; Woolsey, Nicholas; Liang, Chia-Pin; Ramella-Roman, Jessica; Chen, Yu; Pfefer, Joshua

    2014-03-01

    In biophotonic imaging, turbid phantoms that are low-cost, biologically-relevant, and durable are desired for standardized performance assessment. Such phantoms often contain inclusions of varying depths and sizes in order to quantify key image quality characteristics such as penetration depth, sensitivity and contrast detectability. The emerging technique of rapid prototyping with three-dimensional (3D) printers provides a potentially revolutionary way to fabricate these structures. Towards this goal, we have characterized the optical properties and morphology of phantoms fabricated by two 3D printing approaches: thermosoftening and photopolymerization. Material optical properties were measured by spectrophotometry while the morphology of phantoms incorporating 0.2-1.0 mm diameter channels was studied by μCT, optical coherence tomography (OCT) and optical microscopy. A near-infrared absorbing dye and nanorods at several concentrations were injected into channels to evaluate detectability with a near-infrared hyperspectral reflectance imaging (HRI) system (650-1100 nm). Phantoms exhibited biologically-relevant scattering and low absorption across visible and near-infrared wavelengths. Although limitations in resolution were noted, channels with diameters of 0.4 mm or more could be reliably fabricated. The most significant problem noted was the porosity of phantoms generated with the thermosoftening-based printer. The aforementioned three imaging methods provided a valuable mix of insights into phantom morphology and may also be useful for detailed structural inspection of medical devices fabricated by rapid prototyping, such as customized implants. Overall, our findings indicate that 3D printing has significant potential as a method for fabricating well-characterized, standard phantoms for medical imaging modalities such as HRI.

  11. Synthesis of ferroelectric nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Roervik, Per Martin

    2008-12-15

    respectively BaTi2O5/BaTi5O11 and Na2Ti6O13 for the two different systems, in contradiction to the previous studies. It was shown that NaCl reacted with BaO(PbO) resulting in loss of volatile BaCl2 (PbCl2 ) and formation and preferential growth of titanium oxide-rich nanorods instead of the target phase BaTiO3 (or PbTiO3 ). The molten salt synthesis route may therefore not necessarily yield nanorods of the target ternary oxide as reported previously. In addition, the importance of NaCl(g) for the growth of nanorods below the melting point of NaCl was demonstrated in a special experimental setup, where NaCl and the precursors were physically separated. In Paper II and III, a hydrothermal synthesis method to grow arrays and hierarchical nanostructures of PbTiO3 nanorods and platelets on substrates is presented. Hydrothermal treatment of an amorphous PbTiO3 precursor in the presence of a surfactant and PbTiO3 or SrTiO3 substrates resulted in the growth of PbTiO3 nanorods and platelets aligned in the crystallographic <100> orientations of the SrTiO3 substrates. PbTiO3 nanorods oriented perpendicular to the substrate surface could also be grown directly on the substrate by a modified synthesis method. The hydrothermal method described in Paper II and III was developed on the basis of the method described in Appendices I and II. In Paper IV, a template-assisted method to make PbTiO3 nanotubes is presented. An equimolar Pb-Ti sol was dropped onto porous alumina membranes and penetrated into the channels of the template. Single-phase PbTiO3 perovskite nanotubes were obtained by annealing at 700 degrees Celsius for 6 h. The nanotubes had diameters of 200 - 400 nm with a wall thickness of approximately 20 nm. Excess PbO or annealing in a Pb-containing atmosphere was not necessary in order to achieve single phase PbTiO3 nanotubes. The influence of the heating procedure and the sol concentration is discussed. In Paper V, a piezoresponse force microscopy study of single PbTiO3 nanorods is

  12. Synthesis of ferroelectric nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Roervik, Per Martin

    2008-12-15

    respectively BaTi2O5/BaTi5O11 and Na2Ti6O13 for the two different systems, in contradiction to the previous studies. It was shown that NaCl reacted with BaO(PbO) resulting in loss of volatile BaCl2 (PbCl2 ) and formation and preferential growth of titanium oxide-rich nanorods instead of the target phase BaTiO3 (or PbTiO3 ). The molten salt synthesis route may therefore not necessarily yield nanorods of the target ternary oxide as reported previously. In addition, the importance of NaCl(g) for the growth of nanorods below the melting point of NaCl was demonstrated in a special experimental setup, where NaCl and the precursors were physically separated. In Paper II and III, a hydrothermal synthesis method to grow arrays and hierarchical nanostructures of PbTiO3 nanorods and platelets on substrates is presented. Hydrothermal treatment of an amorphous PbTiO3 precursor in the presence of a surfactant and PbTiO3 or SrTiO3 substrates resulted in the growth of PbTiO3 nanorods and platelets aligned in the crystallographic <100> orientations of the SrTiO3 substrates. PbTiO3 nanorods oriented perpendicular to the substrate surface could also be grown directly on the substrate by a modified synthesis method. The hydrothermal method described in Paper II and III was developed on the basis of the method described in Appendices I and II. In Paper IV, a template-assisted method to make PbTiO3 nanotubes is presented. An equimolar Pb-Ti sol was dropped onto porous alumina membranes and penetrated into the channels of the template. Single-phase PbTiO3 perovskite nanotubes were obtained by annealing at 700 degrees Celsius for 6 h. The nanotubes had diameters of 200 - 400 nm with a wall thickness of approximately 20 nm. Excess PbO or annealing in a Pb-containing atmosphere was not necessary in order to achieve single phase PbTiO3 nanotubes. The influence of the heating procedure and the sol concentration is discussed. In Paper V, a piezoresponse force microscopy study of single PbTiO3 nanorods is

  13. Self-assembled MoS2–carbon nanostructures: influence of nanostructuring and carbon on lithium battery performance

    KAUST Repository

    Das, Shyamal K.

    2012-01-01

    Composites of MoS 2 and amorphous carbon are grown and self-assembled into hierarchical nanostructures via a hydrothermal method. Application of the composites as high-energy electrodes for rechargeable lithium-ion batteries is investigated. The critical roles of nanostructuring of MoS 2 and carbon composition on lithium-ion battery performance are highlighted. © 2012 The Royal Society of Chemistry.

  14. Optical properties of silver doped amorphous films of composition Ge28S72 and Ge22Ga6S72

    Czech Academy of Sciences Publication Activity Database

    Bartoš, M.; Wágner, T.; Válková, S.; Pavlišta, M.; Vlček, Milan; Beneš, L.; Frumar, M.

    Bucharest: National Institute R&D of Materials Physics, 77125-Bucharest, Magurele, P.O. Box Mg. 7, Bucharest, Romania, 2011. s. 38. [Fifth International Conference on Amorphous and Nanostructured Chalcogenides. 26.06.2011-01.07.2011, Magurele - Bucharest] Institutional research plan: CEZ:AV0Z40500505 Keywords : amorphous films * chalcogenides * optical properties Subject RIV: CA - Inorganic Chemistry

  15. TEM of nanostructured metals and alloys

    Energy Technology Data Exchange (ETDEWEB)

    Karnthaler, H.P.; Waitz, T.; Rentenberger, C.; Mingler, B

    2004-12-15

    Nanostructuring has been used to improve the mechanical properties of bulk metals and alloys. Transmission electron microscopy (TEM) including atomic resolution is therefore appropriate to study these nanostructures; four examples are given as follows. (1) The early stages of precipitation at RT were investigated in an Al-Mg-Si alloy. By high resolution TEM it is shown that the precipitates lie on (0 0 1) planes having an ordered structure. (2) In Co alloys the fronts of martensitic phase transformations were analysed showing that the transformation strains are very small thus causing no surface relief. (3) Re-ordering and recrystallization were studied by in situ TEM of an Ni{sub 3}Al alloy being nanocrystalline after severe plastic deformation. (4) In NiTi severe plastic deformation is leading to the formation of amorphous shear bands. From the TEM analysis it is concluded that the amorphization is caused by plastic shear instability starting in the shear bands.

  16. TEM of nanostructured metals and alloys

    International Nuclear Information System (INIS)

    Nanostructuring has been used to improve the mechanical properties of bulk metals and alloys. Transmission electron microscopy (TEM) including atomic resolution is therefore appropriate to study these nanostructures; four examples are given as follows. (1) The early stages of precipitation at RT were investigated in an Al-Mg-Si alloy. By high resolution TEM it is shown that the precipitates lie on (0 0 1) planes having an ordered structure. (2) In Co alloys the fronts of martensitic phase transformations were analysed showing that the transformation strains are very small thus causing no surface relief. (3) Re-ordering and recrystallization were studied by in situ TEM of an Ni3Al alloy being nanocrystalline after severe plastic deformation. (4) In NiTi severe plastic deformation is leading to the formation of amorphous shear bands. From the TEM analysis it is concluded that the amorphization is caused by plastic shear instability starting in the shear bands

  17. Corrosion resistant amorphous alloys

    International Nuclear Information System (INIS)

    A review of publication data on corrosion resistance of amorphous alloys and the methods of amorphization of surface layers of massive materials (laser treatment, iron implantation, detonation-gas spraying, cathode and ion sputtering, electrodeposition) was made. A study was made on corrosion properties of Fe66Cr11B10Si4 alloy in cast state and after laser irradiation, rendering the surface amorphous as well as the samples of Arenco iron and steel 20 with ion-plasma coatings of Fe-Cr-Ni-Ti alloy. It was established that amorphous coatings posses much higher corrosion resistance as compared to crystalline alloys on the same base

  18. BioPhotonics workstation: A versatile setup for simultaneous optical manipulation, heat stress, and intracellular pH measurements of a live yeast cell

    DEFF Research Database (Denmark)

    Aabo, Thomas; Bañas, Andrew Rafael; Glückstad, Jesper; Siegumfeldt, Henrik; Arneborg, Nils

    2011-01-01

    In this study we have modified the BioPhotonics workstation (BWS), which allows for using long working distance objective for optical trapping, to include traditional epi-fluorescence microscopy, using the trapping objectives. We have also added temperature regulation of sample stage, allowing for...

  19. Amorphous iron (II) carbonate

    DEFF Research Database (Denmark)

    Sel, Ozlem; Radha, A.V.; Dideriksen, Knud;

    2012-01-01

    Abstract The synthesis, characterization and crystallization energetics of amorphous iron (II) carbonate (AFC) are reported. AFC may form as a precursor for siderite (FeCO3). The enthalpy of crystallization (DHcrys) of AFC is similar to that of amorphous magnesium carbonate (AMC) and more...

  20. Nanostructured photovoltaics

    Science.gov (United States)

    Fu, Lan; Tan, H. Hoe; Jagadish, Chennupati

    2013-01-01

    Energy and the environment are two of the most important global issues that we currently face. The development of clean and sustainable energy resources is essential to reduce greenhouse gas emission and meet our ever-increasing demand for energy. Over the last decade photovoltaics, as one of the leading technologies to meet these challenges, has seen a continuous increase in research, development and investment. Meanwhile, nanotechnology, which is considered to be the technology of the future, is gradually revolutionizing our everyday life through adaptation and incorporation into many traditional technologies, particularly energy-related technologies, such as photovoltaics. While the record for the highest efficiency is firmly held by multijunction III-V solar cells, there has never been a shortage of new research effort put into improving the efficiencies of all types of solar cells and making them more cost effective. In particular, there have been extensive and exciting developments in employing nanostructures; features with different low dimensionalities, such as quantum wells, nanowires, nanotubes, nanoparticles and quantum dots, have been incorporated into existing photovoltaic technologies to enhance their performance and/or reduce their cost. Investigations into light trapping using plasmonic nanostructures to effectively increase light absorption in various solar cells are also being rigorously pursued. In addition, nanotechnology provides researchers with great opportunities to explore the new ideas and physics offered by nanostructures to implement advanced solar cell concepts such as hot carrier, multi-exciton and intermediate band solar cells. This special issue of Journal of Physics D: Applied Physics contains selected papers on nanostructured photovoltaics written by researchers in their respective fields of expertise. These papers capture the current excitement, as well as addressing some open questions in the field, covering topics including the

  1. Ion beam induced dissolution and precipitation of in situ formed Si-nanostructures in a-SiNx:H matrix

    International Nuclear Information System (INIS)

    We report here the response of in situ formed Si-nanostructures embedded in Si-rich hydrogenated amorphous silicon nitride matrix to 100 MeV Ni8+ ions irradiation under normal incidence at room temperature. Prior to irradiation, Si-nanostructures are amorphous in nature having partial crystallinity. Irradiation with a fluence of 5 × 1012 ions/cm2 leads to dissolution of Si-nanostructures. Nevertheless, irradiation with a relatively higher fluence of 1 × 1014 ions/cm2 enhances the nucleation and leads to the formation of amorphous Si-nanostructures. The results are understood on the basis of intense electronic energy loss induced hydrogen desorption and consequent rearrangement of the amorphous network under thermal spike formalism of ion–material interaction.

  2. Direct laser planting of hybrid Au-Ag/C nanostructures - nanoparticles, flakes and flowers

    CERN Document Server

    Manshina, Alina; Bashouti, Muhammad; Povolotskiy, Alexey; Petrov, Yuriy; Koshevoy, Igor; Christiansen, Silke; Tunik, Sergey; Leuchs, Gerd

    2015-01-01

    We demonstrate a new approach for forming hybrid metal/carbonaceous nanostructures in a controlled direct laser planting process. Au-Ag nanoclusters in amorphous or crystalline carbonaceous matrices are formed with different morphology: nanoparticles, nanoflakes, and nanoflowers. In contrast to other generation techniques our approach is simple, involving only a single laser-induced process transforming supramolecular complexes dissolved in solvent such as acetone, acetophenone, or dichloroethane into hybrid nanostructures in the laser-affected area of the substrate. The morphology of the hybrid nanostructures can be steered by controlling the deposition parameters, the composition of the liquid phase and the type of substrate, amorphous or crystalline. The carbonaceous phase of the hybrid nanostructures consists of hydrogenated amorphous carbon in the case of nanoparticles and of crystalline orthorhombic graphite of nanoscale thickness in the case of flakes and flowers. To the best of our knowledge this is t...

  3. Amorphous silicon thermometer

    International Nuclear Information System (INIS)

    The carbon glass resistance thermometers (CGRT) shows an unstable drift by heat cycles. Since we were looking for a more stable element of thermometer for cryogenic and high magnetic field environments, we selected amorphous silicon as a substitute for CGRT. The resistance of many amorphous samples were measured at 4K, at 77K, and 300K. We eventually found an amorphous silicon (Si-H) alloy whose the sensitivity below 77K was comparable to that of the germanium resistance thermometer with little magnetic field influence. (author)

  4. Programmable SERS active substrates for chemical and biosensing applications using amorphous/crystalline hybrid silicon nanomaterial

    OpenAIRE

    Jeffery Alexander Powell; Krishnan Venkatakrishnan; Bo Tan

    2016-01-01

    We present the creation of a unique nanostructured amorphous/crystalline hybrid silicon material that exhibits surface enhanced Raman scattering (SERS) activity. This nanomaterial is an interconnected network of amorphous/crystalline nanospheroids which form a nanoweb structure; to our knowledge this material has not been previously observed nor has it been applied for use as a SERS sensing material. This material is formed using a femtosecond synthesis technique which facilitates a laser plu...

  5. MICCAI ´06 - Workshop on Biophotonics Imaging for Diagnostics and Treatment, October 6, 2006 proceedings, 9th MICCAI Conference

    DEFF Research Database (Denmark)

    Ersbøll, Bjarne Kjær; Jørgensen, Thomas Martini

    2006-01-01

    Preface: Biophotonics can be defined as the study of the interaction of light with biological material. With the recent advances in biomedical science, our understanding of the mechanisms of human health and disease has extended into the regime of cellular and molecular structure and function....... Contents: 1 Hyperspectral image analysis: Some applications in biotechnology and their prospective solutions / Mark Berman et al., CSIRO, Australia 7 Quantifying composition of human tissues from multispectral images using a model of image formation / Ela Claridge et al., School of Computer Science...... of Medical Biophysics, University of Toronto, Canada 41 Biomedical applications of terahertz technology / Vincent Wallace, Teraview, United Kingdom 43 The physical principles of chemical recognition in terahertz spectral imaging / Peter Uhd Jepsen and Stewart J. Clark, COM, DTU, Denmark 51 A bidimensional...

  6. Injection moulding antireflective nanostructures

    DEFF Research Database (Denmark)

    Christiansen, Alexander Bruun; Clausen, Jeppe Sandvik; Mortensen, N. Asger;

    We present a method for injection moulding antireflective nanostructures on large areas, for high volume production. Nanostructured black silicon masters were fabricated by mask-less reactive ion etching, and electroplated with nickel. The nickel shim was antistiction coated and used in an...... index of the nanostructured surfaces was estimated from atomic force micrographs and the theoretical reflectance was calculated using the transfer matrix method and effective medium theory. The measured reflectance shows good agreement with the theory of graded index antireflective nanostructures...

  7. 生物光子与藏药七十味珍珠丸的药理机制%Biophotons are Involved in the Pharmacological Mechanisms of Ratnasampil

    Institute of Scientific and Technical Information of China (English)

    孙燕; 冯斌; 龙运然; 戴甲培

    2011-01-01

    A highly sensitive biophoton detection (imaging) system ( mainly consisting of an Electron multiplying CCD and a stereoscope) was utilized to detect the biophoton activities in adult female Kunming mice treated with Ratnasampil (RNSP) (ig). Ten days after RNSP treatment, the effects of RNSP on the changes of biophoton emission from the isolated brain slices, liver and kidney samples were investigated. Experimental results showed that the brain slices, liver and kidney can emit spontaneous uhraweak photons, which were more intensive after light illumination. The maximum values of induced photon emission of the brain slices were higher in RNSP treated group than that in control group, and the decay was slower. These results suggest that the pharmacological effect of RNSP may take place by influencing the biophotonic activities in the target tissues such as the brain. The possible mechanism may be that RNSP regulates the functions of tissue cells by influence of biophoton signal communications, although the exact mechanisms need to be investigated further.%采用高度敏感的生物光子检测(成像)系统(主要由电子倍增CCD和体视显微镜组成),研究了藏药七十味珍珠丸(RNSP)灌胃处理对健康成年雌性昆明小鼠脑片、肝和肾组织的生物光子活动调控的影响.实验结果表明:脑片、肝和肾均具有自发光现象(生物光子).在光刺激下,脑片、肝和。肾具有不同程度的诱发光现象.RNSP处理后的脑组织诱发光的最大值高于对照组,并且衰减较慢.研究结果提示RNSP可能通过影响效应组织如脑组织的生物光子的活动来发挥其药理作用.其作用机制可能是通过影响生物光子信号传递对组织细胞功能产生调节作用,确切的作用机制值得进一步研究.

  8. Nanostructured thin films and coatings mechanical properties

    CERN Document Server

    2010-01-01

    The first volume in "The Handbook of Nanostructured Thin Films and Coatings" set, this book concentrates on the mechanical properties, such as hardness, toughness, and adhesion, of thin films and coatings. It discusses processing, properties, and performance and provides a detailed analysis of theories and size effects. The book presents the fundamentals of hard and superhard nanocomposites and heterostructures, assesses fracture toughness and interfacial adhesion strength of thin films and hard nanocomposite coatings, and covers the processing and mechanical properties of hybrid sol-gel-derived nanocomposite coatings. It also uses nanomechanics to optimize coatings for cutting tools and explores various other coatings, such as diamond, metal-containing amorphous carbon nanostructured, and transition metal nitride-based nanolayered multilayer coatings.

  9. Optical probing of long-range spatial correlation and symmetry in complex biophotonic architectures on transparent insect wings

    International Nuclear Information System (INIS)

    We experimentally probe the structural organization of complex bio-photonic architecture on transparent insect wings by a simple, non-invasive, real-time optical technique. A stable and reproducible far-field diffraction pattern in transmission was observed using collimated cw and broadband fs laser pulses. A quantitative analysis of the observed diffraction pattern unveiled long-range quasi-periodic order in the arrangement of the microstructures over mm scale. These observations agree well with the Fourier analysis of SEM images of the wing taken at various length scales. We propose a simple quantitative model based on optical diffraction by an array of non overlapping microstructures with minimal disorder which supports our experimental observations. We observed a rotation of the original diffraction profile by scanning the laser beam across the wing sample which gives direct signature of organizational symmetry in microstructure arrangements at various length scales. In addition, we report the first optical detection of reorganization in the photonic architecture on the Drosophila wings by various genetic mutations. These results have potential for the design and development of diffractive optical components for applied photonics and may open up new opportunities in biomimetic device research. (letter)

  10. Nanostructured composite reinforced material

    Science.gov (United States)

    Seals, Roland D.; Ripley, Edward B.; Ludtka, Gerard M.

    2012-07-31

    A family of materials wherein nanostructures and/or nanotubes are incorporated into a multi-component material arrangement, such as a metallic or ceramic alloy or composite/aggregate, producing a new material or metallic/ceramic alloy. The new material has significantly increased strength, up to several thousands of times normal and perhaps substantially more, as well as significantly decreased weight. The new materials may be manufactured into a component where the nanostructure or nanostructure reinforcement is incorporated into the bulk and/or matrix material, or as a coating where the nanostructure or nanostructure reinforcement is incorporated into the coating or surface of a "normal" substrate material. The nanostructures are incorporated into the material structure either randomly or aligned, within grains, or along or across grain boundaries.

  11. Plasmonics in composite nanostructures

    Directory of Open Access Journals (Sweden)

    Hong Wei

    2014-10-01

    Full Text Available Plasmonics is a rapidly developing research field with many potential applications in fields ranging from bioscience, information processing and communication to quantum optics. It is based on the generation, manipulation and transfer of surface plasmons (SPs that have the ability to manipulate light at the nanoscale. Realizing plasmonic applications requires understanding how the SP-based properties depend on the nanostructures and how these properties can be controlled. For that purpose composite nanostructures are particularly interesting because many novel and extraordinary properties unattainable in single nanostructures can be obtained by designing composite nanostructures with various materials. Here, we review recent advances in the studies of three classes of composite nanostructure that are important for plasmonics: metal–metal, metal–dielectric, and metal–semiconductor composite nanostructures.

  12. Advanced Magnetic Nanostructures

    CERN Document Server

    Sellmyer, David

    2006-01-01

    Advanced Magnetic Nanostructures is devoted to the fabrication, characterization, experimental investigation, theoretical understanding, and utilization of advanced magnetic nanostructures. Focus is on various types of 'bottom-up' and 'top-down' artificial nanostructures, as contrasted to naturally occurring magnetic nanostructures, such as iron-oxide inclusions in magnetic rocks, and to structures such as perfect thin films. Chapter 1 is an introduction into some basic concepts, such as the definitions of basic magnetic quantities. Chapters 2-4 are devoted to the theory of magnetic nanostructures, Chapter 5 deals with the characterization of the structures, and Chapters 6-10 are devoted to specific systems. Applications of advanced magnetic nanostructures are discussed in Chapters11-15 and, finally, the appendix lists and briefly discusses magnetic properties of typical starting materials. Industrial and academic researchers in magnetism and related areas such as nanotechnology, materials science, and theore...

  13. Nanostructured Materials for Magnetoelectronics

    CERN Document Server

    Mikailzade, Faik

    2013-01-01

    This book provides an up-to-date review of nanometer-scale magnetism and focuses on the investigation of the basic properties of magnetic nanostructures. It describes a wide range of physical aspects together with theoretical and experimental methods. A broad overview of the latest developments in this emerging and fascinating field of nanostructured materials is given with emphasis on the practical understanding and operation of submicron devices based on nanostructured magnetic materials.

  14. Amorphous silicon based particle detectors

    OpenAIRE

    Wyrsch, N; Franco, A; Riesen, Y.; Despeisse, M; S. Dunand; Powolny, F; Jarron, P.; Ballif, C.

    2012-01-01

    Radiation hard monolithic particle sensors can be fabricated by a vertical integration of amorphous silicon particle sensors on top of CMOS readout chip. Two types of such particle sensors are presented here using either thick diodes or microchannel plates. The first type based on amorphous silicon diodes exhibits high spatial resolution due to the short lateral carrier collection. Combination of an amorphous silicon thick diode with microstrip detector geometries permits to achieve micromete...

  15. Microwave plasma-enhanced chemical vapour deposition growth of carbon nanostructures

    Directory of Open Access Journals (Sweden)

    Shivan R. Singh

    2010-05-01

    Full Text Available The effect of various input parameters on the production of carbon nanostructures using a simple microwave plasma-enhanced chemical vapour deposition technique has been investigated. The technique utilises a conventional microwave oven as the microwave energy source. The developed apparatus is inexpensive and easy to install and is suitable for use as a carbon nanostructure source for potential laboratory-based research of the bulk properties of carbon nanostructures. A result of this investigation is the reproducibility of specific nanostructures with the variation of input parameters, such as carbon-containing precursor and support gas flow rate. It was shown that the yield and quality of the carbon products is directly controlled by input parameters. Transmission electron microscopy and scanning electron microscopy were used to analyse the carbon products; these were found to be amorphous, nanotubes and onion-like nanostructures.

  16. Influence of the atmosphere on the growth by CVD of silicon based nanostructures.

    Science.gov (United States)

    López-Camacho, E; Fernández, M; Gómez-Aleixandre, C

    2009-07-01

    Silica nanowires (phi = 70-80 nm) and core crystalline silicon carbide/amorphous silica coaxial nanocables (phi = 30-50 nm) have been grown on Ni (5 nm) covered silicon substrates by thermal CVD at 950 degrees C. Heating the sample in different atmospheres and the addition of methane lead to the growth of the nanostructures. The as-grown product was characterized by Scanning Electron (SEM) and Transmission Electron (TEM) Microscopies, Infrared (IR) and Glow Discharge Optical Emission (GDOES) Spectroscopies. High contents of Ni, O and Si have been detected in the surface layer for argon and nitrogen treatments and in both cases silica based nanostructures grew. However, no nanostructures were obtained in hydrogen environment probably due to the detected Ni migration inward the substrate making the nanostructures nucleation more difficult. In this work we have studied and proven that previous processes on the substrate surface affect significantly the nanostructures growth. PMID:19916427

  17. Magnetic carbon nanostructures: microwave energy-assisted pyrolysis vs. conventional pyrolysis.

    Science.gov (United States)

    Zhu, Jiahua; Pallavkar, Sameer; Chen, Minjiao; Yerra, Narendranath; Luo, Zhiping; Colorado, Henry A; Lin, Hongfei; Haldolaarachchige, Neel; Khasanov, Airat; Ho, Thomas C; Young, David P; Wei, Suying; Guo, Zhanhu

    2013-01-11

    Magnetic carbon nanostructures from microwave assisted- and conventional-pyrolysis processes are compared. Unlike graphitized carbon shells from conventional heating, different carbon shell morphologies including nanotubes, nanoflakes and amorphous carbon were observed. Crystalline iron and cementite were observed in the magnetic core, different from a single cementite phase from the conventional process. PMID:23172110

  18. Single-photon sensitive fast ebCMOS camera system for multiple-target tracking of single fluorophores: application to nano-biophotonics

    Science.gov (United States)

    Cajgfinger, Thomas; Chabanat, Eric; Dominjon, Agnes; Doan, Quang T.; Guerin, Cyrille; Houles, Julien; Barbier, Remi

    2011-03-01

    Nano-biophotonics applications will benefit from new fluorescent microscopy methods based essentially on super-resolution techniques (beyond the diffraction limit) on large biological structures (membranes) with fast frame rate (1000 Hz). This trend tends to push the photon detectors to the single-photon counting regime and the camera acquisition system to real time dynamic multiple-target tracing. The LUSIPHER prototype presented in this paper aims to give a different approach than those of Electron Multiplied CCD (EMCCD) technology and try to answer to the stringent demands of the new nano-biophotonics imaging techniques. The electron bombarded CMOS (ebCMOS) device has the potential to respond to this challenge, thanks to the linear gain of the accelerating high voltage of the photo-cathode, to the possible ultra fast frame rate of CMOS sensors and to the single-photon sensitivity. We produced a camera system based on a 640 kPixels ebCMOS with its acquisition system. The proof of concept for single-photon based tracking for multiple single-emitters is the main result of this paper.

  19. Reflectivity of the gyroid biophotonic crystals in the ventral wing scales of the Green Hairstreak butterfly, Callophrys rubi

    NARCIS (Netherlands)

    Michielsen, K.; De Raedt, H.; Stavenga, D. G.

    2010-01-01

    We present a comparison of the computer simulation data of gyroid nanostructures with optical measurements (reflectivity spectra and scattering diagrams) of ventral wing scales of the Green Hairstreak butterfly, Callophrys rubi. We demonstrate that the omnidirectional green colour arises from the gy

  20. Microstructure, thermal, and mechanical properties of nanostructured Cu-9.5Ni-4.0Sn-7.5P

    Science.gov (United States)

    Li, J.; Wang, T. M.

    1995-04-01

    Nanostructured Cu-9.5Ni-4.0Sn-7.5P samples represent a polycrystal microstructure of nanometer-sized α-Cu and Cu3P crystallites for crystallite sizes less than 20 nm and of nanometer-sized α-Cu, Cu3P, and Ni2P crystallites for crystallite sizes greater than 20 nm. The specific heat values between 300 K and 400 K for the nanostructured sample with crystallite size of 10 nm are about 20% higher than for the amorphous sample and about 40% higher than for the coarse-grained sample. The hardness of the nanostructured sample with crystallite size of 10 nm is 30% higher than that of the amorphous sample and 110% higher than that of the coarse-grained sample. The variation in hardness with the crystallite size for the nanostructured samples follows the Hall-Petch relationship.

  1. Light-emitting diode therapy in exercise-trained mice increases muscle performance, cytochrome c oxidase activity, ATP and cell proliferation [J. Biophotonics 8, No. 9, 740-754 (2015)].

    Science.gov (United States)

    Ferraresi, Cleber; Parizotto, Nivaldo Antonio; Pires de Sousa, Marcelo Victor; Kaippert, Beatriz; Huang, Ying-Ying; Koiso, Tomoharu; Bagnato, Vanderlei Salvador; Hamblin, Michael R

    2016-09-01

    In the article by C. Ferraresi et al. (DOI: http://dx.doi.org/10.1002/jbio.201400087), published in J. Biophotonics 8, 740-754 (2015), a statement regarding the approval of some data the authors used is incorrect. This erratum is published to rectify this. PMID:27592534

  2. On the formation of an interface amorphous layer in nanostructured ferroelectric Ba{sub 0.8}Sr{sub 0.2}TiO{sub 3} thin films integrated on Pt–Si and its effect on the electrical properties

    Energy Technology Data Exchange (ETDEWEB)

    Silva, J.P.B., E-mail: josesilva@fisica.uminho.pt [Centre of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Sekhar, K.C.; Rodrigues, S.A.S.; Pereira, M. [Centre of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Parisini, A. [CNR-IMM Sezione di Bologna, via P. Gobetti 101, 40129 Bologna (Italy); Alves, E.; Barradas, N.P. [IST/ITN, Instituto Superior Técnico, EN10, 2686-953 Sacavém (Portugal); Gomes, M.J.M. [Centre of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal)

    2013-08-01

    The thin films of Ba{sub 0.8}Sr{sub 0.2}TiO{sub 3} (BST) investigated in this work were produced by pulsed laser deposition at different pulse-repetition frequencies (PRFs). First measurements by X-ray diffraction suggested a crystalline nature of the deposited films. However, scanning transmission electron microscopy and transmission electron microscopy images have revealed that a BST amorphous layer of considerable thickness is formed at the interface between the film and the Pt layer in the films deposited at 10 Hz. Moreover, energy-dispersive X-ray spectroscopy shows that the composition of the BST layer is the same in both the amorphous and the crystalline phases whereas Rutherford backscattering spectrometry measurements have revealed a stoichiometry of the films identical to that of the target. A new interpretation is proposed to explain the formation of this amorphous layer, based on the PRF used during the deposition. Finally, measurements of dielectric and electric properties were performed on as-grown and annealed samples. The results of these measurements are explained by a model, where a low-permittivity amorphous layer is connected in series with the crystalline BST layer.

  3. Preparation and characterization of rare-earth bulks with controllable nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Song Xiaoyan [College of Materials Science and Engineering, Key Laboratory of Advanced Functional Materials, Ministry of Education, Beijing University of Technology, Beijing 100022 (China); Zhang Jiuxing [College of Materials Science and Engineering, Key Laboratory of Advanced Functional Materials, Ministry of Education, Beijing University of Technology, Beijing 100022 (China); Li Erdong [College of Materials Science and Engineering, Key Laboratory of Advanced Functional Materials, Ministry of Education, Beijing University of Technology, Beijing 100022 (China); Lu Nianduan [College of Materials Science and Engineering, Key Laboratory of Advanced Functional Materials, Ministry of Education, Beijing University of Technology, Beijing 100022 (China); Yin Fuxing [National Institute for Materials Science, Sengen 1-2-1, Tsukuba 305-0047 (Japan)

    2006-11-28

    The preparation and characterization of pure rare-earth-metal bulks with controllable nanostructures are reported in this paper. A novel 'oxygen-free' in situ synthesis technique that combines inert-gas condensation with spark plasma sintering (SPS) technology is proposed. Taking into account the special mechanisms of SPS consolidation and the scale effects of nanoparticles, we introduced practical procedures for preparing rare-earth bulks of amorphous, mixed amorphous and nanocrystals, and nanocrystalline microstructures, respectively. Compared with the conventional polycrystalline bulk, these nanostructured bulks exhibit substantially improved physical and mechanical properties. This technique enables comprehensive studies on the microstructures and properties of a large variety of nanostructured metallic materials that are highly reactive in the air.

  4. Preparation and characterization of rare-earth bulks with controllable nanostructures

    International Nuclear Information System (INIS)

    The preparation and characterization of pure rare-earth-metal bulks with controllable nanostructures are reported in this paper. A novel 'oxygen-free' in situ synthesis technique that combines inert-gas condensation with spark plasma sintering (SPS) technology is proposed. Taking into account the special mechanisms of SPS consolidation and the scale effects of nanoparticles, we introduced practical procedures for preparing rare-earth bulks of amorphous, mixed amorphous and nanocrystals, and nanocrystalline microstructures, respectively. Compared with the conventional polycrystalline bulk, these nanostructured bulks exhibit substantially improved physical and mechanical properties. This technique enables comprehensive studies on the microstructures and properties of a large variety of nanostructured metallic materials that are highly reactive in the air

  5. Ultrafast pulsed laser deposition of carbon nanostructures: Structural and optical characterization

    Science.gov (United States)

    Pervolaraki, M.; Komninou, Ph.; Kioseoglou, J.; Othonos, A.; Giapintzakis, J.

    2013-08-01

    Carbon nanostructured materials were obtained by high-repetition rate pulsed laser ablation of a graphite target using a train of 10-ps duration pulses at 1064 nm in different pressures of high-purity Ar gas. It is demonstrated that their microstructure and optical properties vary as a function of the argon pressure. High-resolution transmission electron microscopy revealed the existence of onion-like carbon nanostructures embedded in a matrix of amorphous carbon nanofoam for samples prepared at 300 Pa. In comparison samples prepared at 30 Pa show evidence of both onion-like and turbostratic carbon coexisting in a matrix of amorphous carbon nanofoam whereas samples prepared in vacuum are continuous films of amorphous carbon. Transient transmission spectroscopy measurements suggested that free carrier absorption is the dominant effect following photo-excitation for probing wavelengths in the range of 550-1000 nm and its magnitude varies among the materials investigated due to their different microstructures.

  6. Ultrafast pulsed laser deposition of carbon nanostructures: Structural and optical characterization

    International Nuclear Information System (INIS)

    Carbon nanostructured materials were obtained by high-repetition rate pulsed laser ablation of a graphite target using a train of 10-ps duration pulses at 1064 nm in different pressures of high-purity Ar gas. It is demonstrated that their microstructure and optical properties vary as a function of the argon pressure. High-resolution transmission electron microscopy revealed the existence of onion-like carbon nanostructures embedded in a matrix of amorphous carbon nanofoam for samples prepared at 300 Pa. In comparison samples prepared at 30 Pa show evidence of both onion-like and turbostratic carbon coexisting in a matrix of amorphous carbon nanofoam whereas samples prepared in vacuum are continuous films of amorphous carbon. Transient transmission spectroscopy measurements suggested that free carrier absorption is the dominant effect following photo-excitation for probing wavelengths in the range of 550–1000 nm and its magnitude varies among the materials investigated due to their different microstructures.

  7. Ultrafast pulsed laser deposition of carbon nanostructures: Structural and optical characterization

    Energy Technology Data Exchange (ETDEWEB)

    Pervolaraki, M., E-mail: pervolaraki@ucy.ac.cy [Nanotechnology Research Center and Department of Mechanical and Manufacturing Engineering, University of Cyprus, 75 Kallipoleos Avenue, P.O. Box 20537, 1678 Nicosia (Cyprus); Komninou, Ph.; Kioseoglou, J. [Department of Physics, Aristotle University of Thessaloniki, GR-54124 Thessaloniki (Greece); Othonos, A. [Department of Physics, Research Centre of Ultrafast Science, University of Cyprus, P.O. Box 20537, 1678 Nicosia (Cyprus); Giapintzakis, J., E-mail: giapintz@ucy.ac.cy [Nanotechnology Research Center and Department of Mechanical and Manufacturing Engineering, University of Cyprus, 75 Kallipoleos Avenue, P.O. Box 20537, 1678 Nicosia (Cyprus)

    2013-08-01

    Carbon nanostructured materials were obtained by high-repetition rate pulsed laser ablation of a graphite target using a train of 10-ps duration pulses at 1064 nm in different pressures of high-purity Ar gas. It is demonstrated that their microstructure and optical properties vary as a function of the argon pressure. High-resolution transmission electron microscopy revealed the existence of onion-like carbon nanostructures embedded in a matrix of amorphous carbon nanofoam for samples prepared at 300 Pa. In comparison samples prepared at 30 Pa show evidence of both onion-like and turbostratic carbon coexisting in a matrix of amorphous carbon nanofoam whereas samples prepared in vacuum are continuous films of amorphous carbon. Transient transmission spectroscopy measurements suggested that free carrier absorption is the dominant effect following photo-excitation for probing wavelengths in the range of 550–1000 nm and its magnitude varies among the materials investigated due to their different microstructures.

  8. Nanostructures of zinc oxide

    Directory of Open Access Journals (Sweden)

    Zhong Lin Wang

    2004-06-01

    Full Text Available Zinc oxide (ZnO is a unique material that exhibits semiconducting, piezoelectric, and pyroelectric multiple properties. Using a solid-vapor phase thermal sublimation technique, nanocombs, nanorings, nanohelixes/nanosprings, nanobows, nanobelts, nanowires, and nanocages of ZnO have been synthesized under specific growth conditions. These unique nanostructures unambiguously demonstrate that ZnO is probably the richest family of nanostructures among all materials, both in structures and properties. The nanostructures could have novel applications in optoelectronics, sensors, transducers, and biomedical science because it is bio-safe.

  9. Shear amorphization of boron suboxide

    International Nuclear Information System (INIS)

    We report for the first time the shear-induced local amorphization of boron suboxide subjected to nanoindentation. The amorphous bands have a width of ∼1–3 nm and a length of 200–300 nm along the (01¯11) crystal plane. We show direct experimental evidence that the amorphous shear bands of boron suboxide are driven from the coalescence of dislocation loops under high shear stresses. These observations provide insights into the microscopic deformation and failure of high-strength and lightweight ceramics

  10. Three-dimensional amorphous silicon solar cells on periodically ordered ZnO nanocolumns

    Czech Academy of Sciences Publication Activity Database

    Neykova, Neda; Moulin, E.; Campa, A.; Hruška, Karel; Poruba, Aleš; Stückelberger, M.; Haug, F.J.; Topič, M.; Ballif, C.; Vaněček, Milan

    2015-01-01

    Roč. 212, č. 8 (2015), s. 1823-1829. ISSN 1862-6300 R&D Projects: GA MŠk 7E12029; GA ČR(CZ) GA14-05053S EU Projects: European Commission(XE) 283501 - FAST TRACK Institutional support: RVO:68378271 Keywords : amorphous materials * hydrothermal growth * nanostructures * silicon * solar cells * ZnO Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.616, year: 2014

  11. Simulation in Amorphous Silicon and Amorphous Silicon Carbide Pin Diodes

    OpenAIRE

    Gonçalves, Dora; Fernandes, Miguel; Louro, Paula; Fantoni, Alessandro; Vieira, Manuela

    2014-01-01

    Part 21: Electronics: Devices International audience Photodiodes are devices used as image sensors, reactive to polychromatic light and subsequently color detecting, and they are also used in optical communication applications. To improve these devices performance it is essential to study and control their characteristics, in fact their capacitance and spectral and transient responses. This study considers two types of diodes, an amorphous silicon pin and an amorphous silicon carbide pi...

  12. Self-assembled nanostructures

    CERN Document Server

    Zhang, Jin Z; Liu, Jun; Chen, Shaowei; Liu, Gang-yu

    2003-01-01

    Nanostructures refer to materials that have relevant dimensions on the nanometer length scales and reside in the mesoscopic regime between isolated atoms and molecules in bulk matter. These materials have unique physical properties that are distinctly different from bulk materials. Self-Assembled Nanostructures provides systematic coverage of basic nanomaterials science including materials assembly and synthesis, characterization, and application. Suitable for both beginners and experts, it balances the chemistry aspects of nanomaterials with physical principles. It also highlights nanomaterial-based architectures including assembled or self-assembled systems. Filled with in-depth discussion of important applications of nano-architectures as well as potential applications ranging from physical to chemical and biological systems, Self-Assembled Nanostructures is the essential reference or text for scientists involved with nanostructures.

  13. Amorphous drugs and dosage forms

    DEFF Research Database (Denmark)

    Grohganz, Holger; Löbmann, K.; Priemel, P.;

    2013-01-01

    The transformation to an amorphous form is one of the most promising approaches to address the low solubility of drug compounds, the latter being an increasing challenge in the development of new drug candidates. However, amorphous forms are high energy solids and tend to recry stallize. New...... formulation principles are needed to ensure the stability of amorphous drug forms. The formation of solid dispersions is still the most investigated approach, but additional approaches are desirable to overcome the shortcomings of solid dispersions. Spatial separation by either coating or the use of micro......-containers has shown potential to prevent or delay recrystallization. Another recent approach is the formation of co-amorphous mixtures between either two drugs or one drug and one low molecular weight excipient. Molecular interactions between the two molecules provide an energy barrier that has to be overcome...

  14. Aqueous ultracapacitors using amorphous MnO2 and reduced graphene oxide

    Science.gov (United States)

    Mery, Adrien; Ghamouss, Fouad; Autret, Cécile; Farhat, Douaa; Tran-Van, François

    2016-02-01

    Herein, synthesis and characterization of amorphous MnO2 and application in asymmetric aqueous ultracapacitors are reported. Different amorphous manganese oxide (MnO2) materials were synthesized from the reduction of KMnO4 in different media such as ethanol (EtOH) or dimethylformamide (DMF). The electrochemical behavior of amorphous MnO2, labeled MnO2-Et and MnO2-DMF, were studied by using cyclic voltammetry, impedance spectroscopy, and galvanostatic cycling in aqueous electrolyte. XRD, BET, TEM, and SEM characterizations highlighted the amorphous nature and the nanostructuration of these MnO2 materials. BET measurement established that these amorphous MnO2 are mesoporous. In addition, MnO2-Et exhibits a larger specific surface area (168 m2 g-1), a narrower pore diameters distribution with lower diameters compared to MnO2-DMF. These results are in agreement with the electrochemical results. Indeed, MnO2-Et shows a higher specific capacitance and lower impedance in aqueous K2SO4 electrolyte. Furthermore, aqueous asymmetric ultracapacitors were assembled and studied using amorphous MnO2 as positive electrode and reduced graphene oxide (rGO) as negative electrode. These asymmetric systems exhibit an electrochemical stability for more than 20,000 galvanostatic cycles at current density of 1 A g-1 with an operating voltage of 2 V.

  15. Field Emission and Radial Distribution Function Studies of Fractal-like Amorphous Carbon Nanotips

    Directory of Open Access Journals (Sweden)

    Lebrón-Colón M

    2009-01-01

    Full Text Available Abstract The short-range order of individual fractal-like amorphous carbon nanotips was investigated by means of energy-filtered electron diffraction in a transmission electron microscope (TEM. The nanostructures were grown in porous silicon substrates in situ within the TEM by the electron beam-induced deposition method. The structure factorS(k and the reduced radial distribution functionG(r were calculated. From these calculations a bond angle of 124° was obtained which suggests a distorted graphitic structure. Field emission was obtained from individual nanostructures using two micromanipulators with sub-nanometer positioning resolution. A theoretical three-stage model that accounts for the geometry of the nanostructures provides a value for the field enhancement factor close to the one obtained experimentally from the Fowler-Nordheim law.

  16. Ion irradiation induced element-enriched and depleted nanostructures in Zr-Al-Cu-Ni metallic glass

    International Nuclear Information System (INIS)

    The microstructural evolution of a Zr-Al-Cu-Ni metallic glass induced by irradiation with Ar ions was investigated. Under ion irradiation, the Cu- and Ni-enriched nanostructures (diameter of 30–50 nm) consisted of crystalline and amorphous structures were formed. Further, Cu- and Ni-depleted nanostructures with diameters of 5–20 nm were also observed. The formation of these nanostructures can be ascribed to the migration of Cu and Ni atoms in the irradiated metallic glass

  17. Nanostructured electronic and magnetic materials

    Indian Academy of Sciences (India)

    R V Ramanujan

    2003-02-01

    Research and development in nanostructured materials is one of the most intensely studied areas in science. As a result of concerted R & D efforts, nanostructured electronic and magnetic materials have achieved commercial success. Specific examples of novel industrially important nanostructured electronic and magnetic materials are provided. Advantages of nanocrystalline magnetic materials in the context of both materials and devices are discussed. Several high technology examples of the use of nanostructured magnetic materials are presented. Methods of processing nanostructured materials are described and the examples of sol gel, rapid solidification and powder injection moulding as potential processing methods for making nanostructured materials are outlined. Some opportunities and challenges are discussed.

  18. Biophotonics and Bone Biology

    Science.gov (United States)

    Zimmerli, Gregory; Fischer, David; Asipauskas, Marius; Chauhan, Chirag; Compitello, Nicole; Burke, Jamie; Tate, Melissa Knothe

    2004-01-01

    One of the more serious side effects of extended space flight is an accelerated bone loss. Rates of bone loss are highest in the weight-bearing bones of the hip and spine regions, and the average rate of bone loss as measured by bone mineral density measurements is around 1.2% per month for persons in a microgravity environment. It is well known that bone remodeling responds to mechanical forces. We are developing two-photon microscopy techniques to study bone tissue and bone cell cultures to better understand the fundamental response mechanism in bone remodeling. Osteoblast and osteoclast cell cultures are being studied, and the goal is to use molecular biology techniques in conjunction with Fluorescence Lifetime Imaging Microscopy (FLIM) to study the physiology of in-vitro cell cultures in response to various stimuli, such as fluid flow induced shear stress and mechanical stress. We have constructed a two-photon fluorescence microscope for these studies, and are currently incorporating FLIM detection. Current progress will be reviewed. This work is supported by the NASA John Glenn Biomedical Engineering Consortium.

  19. Biophotonics and Bone Biology

    Science.gov (United States)

    Zimmerli, Gregory; Fischer, David; Asipauskas, Marius; Chauhan, Chirag; Compitello, Nicole; Burke, Jamie; Tate, Melissa Knothe

    2004-01-01

    One of the more-serious side effects of extended space flight is an accelerated bone loss [Bioastronautics Critical Path Roadmap, http://research.hq.nasa.gov/code_u/bcpr/index.cfm]. Rates of bone loss are highest in the weight-bearing bones of the hip and spine regions, and the average rate of bone loss as measured by bone mineral density measurements is around 1.2% per month for persons in a microgravity environment. It shows that an extrapolation of the microgravity induced bone loss rates to longer time scales, such as a 2.5 year round-trip to Mars (6 months out at 0 g, 1.5 year stay on Mars at 0.38 g, 6 months back at 0 g), could severely compromise the skeletal system of such a person.

  20. Nanostructured Diamond-Like Carbon Films Grown by Off-Axis Pulsed Laser Deposition

    Directory of Open Access Journals (Sweden)

    Seong Shan Yap

    2015-01-01

    Full Text Available Nanostructured diamond-like carbon (DLC films instead of the ultrasmooth film were obtained by pulsed laser ablation of pyrolytic graphite. Deposition was performed at room temperature in vacuum with substrates placed at off-axis position. The configuration utilized high density plasma plume arriving at low effective angle for the formation of nanostructured DLC. Nanostructures with maximum size of 50 nm were deposited as compared to the ultrasmooth DLC films obtained in a conventional deposition. The Raman spectra of the films confirmed that the films were diamond-like/amorphous in nature. Although grown at an angle, ion energy of >35 eV was obtained at the off-axis position. This was proposed to be responsible for subplantation growth of sp3 hybridized carbon. The condensation of energetic clusters and oblique angle deposition correspondingly gave rise to the formation of nanostructured DLC in this study.

  1. Nanostructures having high performance thermoelectric properties

    Science.gov (United States)

    Yang, Peidong; Majumdar, Arunava; Hochbaum, Allon I; Chen, Renkun; Delgado, Raul Diaz

    2014-05-20

    The invention provides for a nanostructure, or an array of such nanostructures, each comprising a rough surface, and a doped or undoped semiconductor. The nanostructure is an one-dimensional (1-D) nanostructure, such a nanowire, or a two-dimensional (2-D) nanostructure. The nanostructure can be placed between two electrodes and used for thermoelectric power generation or thermoelectric cooling.

  2. Nanostructures having high performance thermoelectric properties

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Peidong; Majumdar, Arunava; Hochbaum, Allon I.; Chen, Renkun; Delgado, Raul Diaz

    2015-12-22

    The invention provides for a nanostructure, or an array of such nanostructures, each comprising a rough surface, and a doped or undoped semiconductor. The nanostructure is an one-dimensional (1-D) nanostructure, such a nanowire, or a two-dimensional (2-D) nanostructure. The nanostructure can be placed between two electrodes and used for thermoelectric power generation or thermoelectric cooling.

  3. Synthesis, morphology and optical properties of pure and Eu3+ doped β-Ga2O3 hollow nanostructures by hydrothermal method

    International Nuclear Information System (INIS)

    Pure and Eu3+ doped β-Ga2O3 hollow nanostructures were synthesized by hydrothermal and calcination processes using carbon spheres as templates in ethanol–water solution. Field-emission scanning electron microscopy and high-resolution transmission electron microscopy analysis revealed β-Ga2O3 hollow nanostructures with diameters of approximately 200 nm and shell thickness of about 20 nm. The X-ray diffraction analysis revealed that the carbon@Ga(OH)CO3 core–shell nanostructures were in amorphous phase before calcination. After calcination, the amorphous core–shell structures yielded highly crystalline β-Ga2O3 hollow nanostructures with spherical shape. The presence of the Ga(OH)CO3 in the shell components is confirmed by the Fourier transform infrared spectrum. The Eu3+ doped β-Ga2O3 hollow nanostructures showed strong red emission corresponding to the 5D4 → 7FJ transition. - Highlights: • The hollow nanostructures were synthesized by hydrothermal and calcination processes. • The shells consist of Ga(OH)CO3 and are amorphous phase with thickness 20 nm. • The highly crystalline β-Ga2O3 hollow structures were formed with diameters of 200 nm. • The β-Ga2O3:Eu3+ (3 mol%) hollow nanostructures at 900 °C show the highest red emission

  4. Micromachining with Nanostructured Cutting Tools

    CERN Document Server

    Jackson, Mark J

    2013-01-01

    The purpose of the brief is to explain how nanostructured tools can be used to machine materials at the microscale.  The aims of the brief are to explain to readers how to apply nanostructured tools to micromachining applications. This book describes the application of nanostructured tools to machining engineering materials and includes methods for calculating basic features of micromachining. It explains the nature of contact between tools and work pieces to build a solid understanding of how nanostructured tools are made.

  5. Fundamentals of amorphous solids structure and properties

    CERN Document Server

    Stachurski, Zbigniew H

    2014-01-01

    Long awaited, this textbook fills the gap for convincing concepts to describe amorphous solids. Adopting a unique approach, the author develops a framework that lays the foundations for a theory of amorphousness. He unravels the scientific mysteries surrounding the topic, replacing rather vague notions of amorphous materials as disordered crystalline solids with the well-founded concept of ideal amorphous solids. A classification of amorphous materials into inorganic glasses, organic glasses, glassy metallic alloys, and thin films sets the scene for the development of the model of ideal amorph

  6. Nanostructured materials for hydrogen storage

    Science.gov (United States)

    Williamson, Andrew J.; Reboredo, Fernando A.

    2007-12-04

    A system for hydrogen storage comprising a porous nano-structured material with hydrogen absorbed on the surfaces of the porous nano-structured material. The system of hydrogen storage comprises absorbing hydrogen on the surfaces of a porous nano-structured semiconductor material.

  7. Synthesis of porphyrin nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Hongyou; Bai, Feng

    2014-10-28

    The present disclosure generally relates to self-assembly methods for generating porphyrin nanostructures. For example, in one embodiment a method is provided that includes preparing a porphyrin solution and a surfactant solution. The porphyrin solution is then mixed with the surfactant solution at a concentration sufficient for confinement of the porphyrin molecules by the surfactant molecules. In some embodiments, the concentration of the surfactant is at or above its critical micelle concentration (CMC), which allows the surfactant to template the growth of the nanostructure over time. The size and morphology of the nanostructures may be affected by the type of porphyrin molecules used, the type of surfactant used, the concentration of the porphyrin and surfactant the pH of the mixture of the solutions, and the order of adding the reagents to the mixture, to name a few variables.

  8. Nano-Structured Silicon Thin Films for Photovoltaic Applications

    Science.gov (United States)

    Taylor, P. Craig

    2008-03-01

    The current technology for thin-film silicon photovoltaic panels is based on hydrogenated amorphous silicon and related alloys, such as silicon-germanium and silicon-carbon. Currently there is great interest in using some form of thin-film silicon that includes nano-structured components. This interest is driven in part by the potential for decreased cost, increased efficiency, and increased stability. Also driving this interest is the abundance of silicon as an element and its lack of toxicity. I will review various structures that have been suggested, and discuss recent results on inhomogeneous films of hydrogenated amorphous silicon that contain nanocrystalline inclusions. In particular, I will describe the mechanisms for optical absorption, carrier transport and the role of defects.

  9. Structure and physical properties of Fe6 O8/ba Fe6 O11 nanostructure

    Science.gov (United States)

    Naseri, Mahmoud; Ghasemi, Rahmat

    2016-05-01

    The thermal treatment method was employed to prepare barium hexaferrite (Fe6 O8/Ba Fe6 O11) nanostructure. This method was attempted to achieve higher homogeneity of the final product. Specimens of barium hexaferrite nanostructure were characterized by various experimental techniques including X-ray diffraction (XRD), high resolution Field emission scanning electron microscope (FESEM) and Fourier transform infrared spectroscopy (FT-IR). X-ray diffraction results showed that there was no crystallinity in the predecessor and it had still amorphous phase. The formations of crystalline phases of barium hexaferrite nanostructures started from 673 to 973 K and the final products had different crystallite sizes ranging from 29 to 48 nm. The chemical analysis of the barium hexaferrite nanostructures was performed by energy dispersion X-ray analysis (EDXA), demonstrated that the barium hexaferrite nanostructures contained the elements of Ba, Fe, and O. The effect of calcination temperature on band gap energy was studied by UV-vis absorption spectra disclosed when calcination temperature increased, the appraised band gap energy values of the BaFe12O19 nanostructures decreased. The formed nanostructures exhibited ferromagnetic behaviors which were confirmed by using a vibrating sample magnetometer (VSM). The technique of the Electron paramagnetic resonance (EPR) spectroscopy was carried out at 300 K on the calcined specimens that exhibited the variation of the line-shapes of the spectra of with calcination temperature.

  10. Structural analysis of nanocrystals and their role in the coercivity mechanism of Nd–Fe–Al–Dy bulk amorphous ferromagnets

    International Nuclear Information System (INIS)

    The magnetic property and microstructure of Nd60−xFe30Al10Dyx (x=0, 2, 4) bulk ferromagnets have been investigated. At room temperature, each alloy sample shows hard magnetic behavior, and the intrinsic coercivity increases significantly with increasing Dy content. Transmission electron microscopy (TEM) and Atom probe tomography (APT) results show nanocrystals of width 5–20 nm embedded in the Fe-rich amorphous matrix. The coercivity mechanism of the Nd60−xFe30Al10Dyx (x=0, 2, 4) amorphous alloys is discussed in the context of Gaunt's strong pinning model of domain walls. The crystallographic phases of nanocrystals identified by high-resolution TEM can act as pinning centers. Our findings give further insight into the coercivity mechanism of Nd-based bulk amorphous alloys through a better understanding of the nanostructural environment. - Highlights: • Study of the crystallographic phases present in the nanocrystals in Nd–Fe–Al–Dy bulk ferromagnets. • The phase composition of the nanocrystals varies with Dy content. • Shows the amorphous matrix is Fe-rich by atom probe tomography. • This work gives further insight into the coercivity mechanism of Nd-based bulk amorphous alloys through a better understanding of the nanostructural environment

  11. Antibacterial Au nanostructured surfaces

    Science.gov (United States)

    Wu, Songmei; Zuber, Flavia; Brugger, Juergen; Maniura-Weber, Katharina; Ren, Qun

    2016-01-01

    We present here a technological platform for engineering Au nanotopographies by templated electrodeposition on antibacterial surfaces. Three different types of nanostructures were fabricated: nanopillars, nanorings and nanonuggets. The nanopillars are the basic structures and are 50 nm in diameter and 100 nm in height. Particular arrangement of the nanopillars in various geometries formed nanorings and nanonuggets. Flat surfaces, rough substrate surfaces, and various nanostructured surfaces were compared for their abilities to attach and kill bacterial cells. Methicillin-resistant Staphylococcus aureus, a Gram-positive bacterial strain responsible for many infections in health care system, was used as the model bacterial strain. It was found that all the Au nanostructures, regardless their shapes, exhibited similar excellent antibacterial properties. A comparison of live cells attached to nanotopographic surfaces showed that the number of live S. aureus cells was technological platform for engineering Au nanotopographies by templated electrodeposition on antibacterial surfaces. Three different types of nanostructures were fabricated: nanopillars, nanorings and nanonuggets. The nanopillars are the basic structures and are 50 nm in diameter and 100 nm in height. Particular arrangement of the nanopillars in various geometries formed nanorings and nanonuggets. Flat surfaces, rough substrate surfaces, and various nanostructured surfaces were compared for their abilities to attach and kill bacterial cells. Methicillin-resistant Staphylococcus aureus, a Gram-positive bacterial strain responsible for many infections in health care system, was used as the model bacterial strain. It was found that all the Au nanostructures, regardless their shapes, exhibited similar excellent antibacterial properties. A comparison of live cells attached to nanotopographic surfaces showed that the number of live S. aureus cells was information (ESI) available. See DOI: 10.1039/c5nr06157a

  12. Amorphous yttrium-iron alloys

    International Nuclear Information System (INIS)

    The magnetic properties of amorphous yttrium-iron alloys Ysub(1-x)Fesub(x) have been studied over a wide concentration range 0.32 2Fe17 alloys, lead in the amorphous state to spin-glass behaviour and asperomagnetic order. The dominant positive interactions produce short-range ferromagnetic correlations which persist up to room temperature. However magnetic saturation cannot be achieved for any of the alloys in applied fields of up to 180 kOe, indicating that strong negative interactions are also present. Exchange interactions become increasingly positive with increasing x, and the magnetic properties of iron-rich alloys approach those of a normal ferromagnet. (author)

  13. Iron - based bulk amorphous alloys

    Directory of Open Access Journals (Sweden)

    R. Babilas

    2010-07-01

    Full Text Available Purpose: The paper presents a structure characterization, thermal and soft magnetic properties analysis of Fe-based bulk amorphous materials in as-cast state and after crystallization process. In addition, the paper gives some brief review about achieving, formation and structure of bulk metallic glasses as a special group of amorphous materials.Design/methodology/approach: The studies were performed on Fe72B20Si4Nb4 metallic glass in form of ribbons and rods. The amorphous structure of tested samples was examined by X-ray diffraction (XRD, transmission electron microscopy (TEM and scanning electron microscopy (SEM methods. The thermal properties of the glassy samples were measured using differential thermal analysis (DTA and differential scanning calorimetry (DSC. The magnetic properties contained initial and maximum magnetic permeability, coercive force and magnetic after-effects measurements were determined by the Maxwell-Wien bridge and VSM methods.Findings: The X-ray diffraction and transmission electron microscopy investigations revealed that the studied as-cast bulk metallic glasses in form of ribbons and rods were amorphous. Two stage crystallization process was observed for studied bulk amorphous alloy. The differences of crystallization temperature between ribbons and rods with chosen thickness are probably caused by different amorphous structures as a result of the different cooling rates in casting process. The SEM images showed that studied fractures could be classified as mixed fractures with indicated two zones contained “river” and “smooth” areas. The changing of chosen soft magnetic properties (μr, Bs, Hc obtained for samples with different thickness is a result of the non-homogenous amorphous structure of tested metallic glasses. The annealing process in temperature range from 373 to 773 K causes structural relaxation of tested amorphous materials, which leads to changes in their physical properties. The qualitative

  14. Hidden structure in amorphous solids

    Energy Technology Data Exchange (ETDEWEB)

    Inam, F. [Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701 (United States); Lewis, James P. [Department of Physics, West Virginia University, Morgantown, West Virginia 26506 (United States); Drabold, D.A. [Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701 (United States); Trinity College, Cambridge CB2 1TQ (United Kingdom)

    2010-03-15

    Recent theoretical studies of amorphous silicon (a-Si) [Pan et al., Phys. Rev. Lett. 100, 206403 (2008)] have revealed subtle but significant structural correlations in network topology: the tendency for short (long) bonds to be spatially correlated with other short (long) bonds. These structures were linked to the electronic band tails in the optical gap. In this paper, we further examine these issues for a-Si, and demonstrate that analogous correlations exist in amorphous SiO{sub 2}, and in the organic molecule, {beta}-carotene. We conclude with a discussion of the origin of the effects and its possible generality. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  15. Physics of carbon nanostructures

    International Nuclear Information System (INIS)

    Carbon is a prominent element that appears in various structures with new promising technological applications. The physics of carbon nanostructures is one of the hot topics in modern condensed matter theory. I plan to present a brief introduction into the theory of variously shaped carbon nanostructures paying special attention to generic field-theory models. The preliminary plan is the following: (1) a brief historical excursus, (2) the most interesting experimental observations, (3) generic models for the description of electronic states in carbon nanoparticles (Dirac-type equations, defects, geometry, etc.), (4) open problems. (author)

  16. Nanostructured piezoelectric energy harvesters

    CERN Document Server

    Briscoe, Joe

    2014-01-01

    This book covers a range of devices that use piezoelectricity to convert mechanical deformation into electrical energy and relates their output capabilities to a range of potential applications. Starting with a description of the fundamental principles and properties of piezo- and ferroelectric materials, where applications of bulk materials are well established, the book shows how nanostructures of these materials are being developed for energy harvesting applications. The authors show how a nanostructured device can be produced, and put in context some of the approaches that are being invest

  17. Thermal transport in nanostructures

    Directory of Open Access Journals (Sweden)

    Nuo Yang

    2012-12-01

    Full Text Available This review summarizes recent studies of thermal transport in nanoscaled semiconductors. Different from bulk materials, new physics and novel thermal properties arise in low dimensional nanostructures, such as the abnormal heat conduction, the size dependence of thermal conductivity, phonon boundary/edge scatterings. It is also demonstrated that phonons transport super-diffusively in low dimensional structures, in other words, Fourier's law is not applicable. Based on manipulating phonons, we also discuss envisioned applications of nanostructures in a broad area, ranging from thermoelectrics, heat dissipation to phononic devices.

  18. Injection moulding antireflective nanostructures

    DEFF Research Database (Denmark)

    Christiansen, Alexander Bruun; Clausen, Jeppe Sandvik; Mortensen, N. Asger;

    2014-01-01

    We present a method for injection moulding antireflective nanostructures on large areas, for high volume production. Nanostructured black silicon masters were fabricated by mask-less reactive ion etching, and electroplated with nickel. The nickel shim was antistiction coated and used in an...... injection moulding process, to fabricate the antireflective surfaces. The cycle-time was 35 s. The injection moulded structures had a height of 125 nm, and the visible spectrum reflectance of injection moulded black polypropylene surfaces was reduced from 4.5±0.5% to 2.5±0.5%. The gradient of the refractive...

  19. Injection moulding antireflective nanostructures

    DEFF Research Database (Denmark)

    Christiansen, Alexander Bruun; Clausen, Jeppe Sandvik; Mortensen, N. Asger;

    We present a method for injection moulding antireflective nanostructures on large areas, for high volume production. Nanostructured black silicon masters were fabricated by mask-less reactive ion etching, and electroplated with nickel. The nickel shim was antistiction coated and used in an...... injection moulding process, to fabricate the antireflective surfaces. The cycle-time was 35 s. The injection moulded structures had a height of 125 nm, and the visible spectrum reflectance of injection moulded black polypropylene surfaces was reduced from 4.5±0.5% to 2.5±0.5%. The gradient of the refractive...

  20. A Template-Free, Ultra-Adsorbing, High Surface Area Carbonate Nanostructure

    OpenAIRE

    Johan Forsgren; Sara Frykstrand; Kathryn Grandfield; Albert Mihranyan; Maria Strømme

    2013-01-01

    We report the template-free, low-temperature synthesis of a stable, amorphous, and anhydrous magnesium carbonate nanostructure with pore sizes below 6 nm and a specific surface area of ∼ 800 m(2) g(-1), substantially surpassing the surface area of all previously described alkali earth metal carbonates. The moisture sorption of the novel nanostructure is featured by a unique set of properties including an adsorption capacity ∼50% larger than that of the hygroscopic zeolite-Y at low relative hu...

  1. Resolving the nanostructure of plasma-enhanced chemical vapor deposited nanocrystalline SiOx layers for application in solar cells

    Science.gov (United States)

    Klingsporn, M.; Kirner, S.; Villringer, C.; Abou-Ras, D.; Costina, I.; Lehmann, M.; Stannowski, B.

    2016-06-01

    Nanocrystalline silicon suboxides (nc-SiOx) have attracted attention during the past years for the use in thin-film silicon solar cells. We investigated the relationships between the nanostructure as well as the chemical, electrical, and optical properties of phosphorous, doped, nc-SiO0.8:H fabricated by plasma-enhanced chemical vapor deposition. The nanostructure was varied through the sample series by changing the deposition pressure from 533 to 1067 Pa. The samples were then characterized by X-ray photoelectron spectroscopy, spectroscopic ellipsometry, Raman spectroscopy, aberration-corrected high-resolution transmission electron microscopy, selected-area electron diffraction, and a specialized plasmon imaging method. We found that the material changed with increasing pressure from predominantly amorphous silicon monoxide to silicon dioxide containing nanocrystalline silicon. The nanostructure changed from amorphous silicon filaments to nanocrystalline silicon filaments, which were found to cause anisotropic electron transport.

  2. Amorphous-silicon cell reliability testing

    Science.gov (United States)

    Lathrop, J. W.

    1985-01-01

    The work on reliability testing of solar cells is discussed. Results are given on initial temperature and humidity tests of amorphous silicon devices. Calibration and measurement procedures for amorphous and crystalline cells are given. Temperature stress levels are diagrammed.

  3. Amorphization and reduction of thermal conductivity in porous silicon by irradiation with swift heavy ions

    International Nuclear Information System (INIS)

    In this article, we demonstrate that the thermal conductivity of nanostructured porous silicon is reduced by amorphization and also that this amorphous phase in porous silicon can be created by swift (high-energy) heavy ion irradiation. Porous silicon samples with 41%-75% porosity are irradiated with 110 MeV uranium ions at six different fluences. Structural characterisation by micro-Raman spectroscopy and SEM imaging show that swift heavy ion irradiation causes the creation of an amorphous phase in porous Si but without suppressing its porous structure. We demonstrate that the amorphization of porous silicon is caused by electronic-regime interactions, which is the first time such an effect is obtained in crystalline silicon with single-ion species. Furthermore, the impact on the thermal conductivity of porous silicon is studied by micro-Raman spectroscopy and scanning thermal microscopy. The creation of an amorphous phase in porous silicon leads to a reduction of its thermal conductivity, up to a factor of 3 compared to the non-irradiated sample. Therefore, this technique could be used to enhance the thermal insulation properties of porous Si. Finally, we show that this treatment can be combined with pre-oxidation at 300 °C, which is known to lower the thermal conductivity of porous Si, in order to obtain an even greater reduction

  4. Laser annealing of amorphous carbon films

    International Nuclear Information System (INIS)

    Amorphous (a-C) Carbon thin films were deposited, using pulsed laser deposition (PLD) with a Nd:YAG laser (1064 nm, 7 ns), from a pyrolytic graphite target, on silicon and refractory metal (Mo) substrates to a film thickness of 55, 400 and 500 nm. Samples were grown at RT and then annealed by a laser annealing technique, to reduce residual stress and induce a locally confined 'graphitization' process. The films were exposed to irradiation, in vacuum, by a Nd:YAG pulsed laser, operating at different wavelengths (VIS, N-UV) and increasing values of energy from 6-100 mJ/pulse. The thinner films were completely destroyed by N-UV laser treatment also at lower energies, owing to the almost direct propagation of heat to the Si substrate with melting and ruinous blistering effects. For thicker films the Raman micro-analysis evidenced the influence of laser treatments on the sp3/sp2 content evolution, and established the formation of aromatic nano-structures of average dimension 4.1-4.7 nm (derived from the ID/IG peak ratio), at fluence values round 50 mJ/cm2 for N-UV and 165 mJ/cm2 for VIS laser irradiation. Higher fluences were not suitable for a-Carbon 'graphitization', since a strong ablation process was the prominent effect of irradiation. Grazing incidence XRD (GI-XRD) used to evaluate the dimension and texturing of nano-particles confirmed the findings of Raman analysis. The effects of irradiation on surface morphology were studied by SEM analysis

  5. Nanostructured intense-laser cleaner

    CERN Document Server

    Li, Xiao Feng; Kong, Qing; Wang, Ping Xiao; Yu, Qin; Gu, Yan Jan; Qu, Jun Fan

    2016-01-01

    A nanostructured target is proposed to enhance an intense-laser contrast: when a laser prepulse is injected on a nanostructured solid target surface, the prepulse is absorbed effectively by the nanostructured surface. The nanostructure size should be less than the laser wavelength. After the prepulse absorption, the front part of the main pulse destroys the microstructure and makes the surface a flat plasma mirror. The body of the main pulse is reflected almost perfectly. Compared with the plasma mirrors, the nanostructured surface is effective for the absorption of the intense laser prepulse, higher than 10^14 W/cm2. By the nanostructured laser cleaner, the laser pulse contrast increases about a hundredfold. The nanostructured laser cleaner works well for near-future intense lasers.

  6. Nanostructured polymer- and metal surfaces

    DEFF Research Database (Denmark)

    Christiansen, Alexander Bruun

    well as structural enhancement of light absorption in thin metal films, deposited on nanostructured substrates. Large areas of nanostructures were realized using the black silicon (BSi) method: a mask less reactive ion etching process, resulting in tapered nanostructures with tunable dimensions, on......, the optical properties of thin metal films deposited on nanostructured surfaces was studied. When a metal film was deposited on BSi structures in Ormocomp, the reflectance of the metal film was lowered significantly, and the absorption was increased. In contrast to their reflective planar counterparts......This Ph.D. thesis explores the optical properties of nanostructured dielectric and metallic surfaces. Focusing on scalable fabrication methods for antireflective nanostructures, this experimental study has resulted in the proof of concept of inexpensive, large area antireflective nanostructures, as...

  7. Investigation of Sb diffusion in amorphous silicon

    OpenAIRE

    Csik, A.; Langer, G A; Erdelyi, G.; Beke, D. L.; Erdelyi, Z.; Vad, K.

    2009-01-01

    Amorphous silicon materials and its alloys become extensively used in some technical applications involving large area of the microelectronic and optoelectronic devices. However, the amorphous-crystalline transition, segregation and diffusion processes still have numerous unanswered questions. In this work we study the Sb diffusion into an amorphous Si film by means of Secondary Neutral Mass Spectrometry (SNMS). Amorphous Si/Si1-xSbx/Si tri-layer samples with 5 at% antimony concentration were...

  8. Fracture Phenomena in Amorphous Selenium

    DEFF Research Database (Denmark)

    Lindegaard-Andersen, Asger; Dahle, Birgit

    1966-01-01

    Fracture surfaces of amorphous selenium broken in flexure at room temperature have been studied. The fracture velocity was found to vary in different regions of the fracture surface. Peculiar features were observed in a transition zone between fast and slower fracture. In this zone cleavage steps...

  9. Amorphous metal matrix composite ribbons

    International Nuclear Information System (INIS)

    Composite ribbons with amorphous matrix and ceramic (SiC, WC, MoB) particles were produced by modified planar melt flow casting methods. Weldability, abrasive wear and wood sanding examinations were carried out in order to find optimal material and technology for elevated wear resistance and sanding durability. The correlation between structure and composite properties is discussed. (author)

  10. Atomistic Models of Amorphous Semiconductors

    NARCIS (Netherlands)

    Jarolimek, K.

    2011-01-01

    Crystalline silicon is probably the best studied material, widely used by the semiconductor industry. The subject of this thesis is an intriguing form of this element namely amorphous silicon. It can contain a varying amount of hydrogen and is denoted as a-Si:H. It completely lacks the neat long ran

  11. Organized nanostructured polymer networks

    Czech Academy of Sciences Publication Activity Database

    Matějka, Libor; Donato, Ricardo Keitel; Pleštil, Josef; Janata, Miroslav; Schrekker, H. S.

    Istanbul : Istanbul Technical University, 2009. s. 21. [Baekeland 2009 International Symposium on Thermosets /2./. 22.11-25.11.2009, Antalya ] R&D Projects: GA AV ČR IAA400500701 Institutional research plan: CEZ:AV0Z40500505 Keywords : nanostructured networks * block copolymers * epoxy-silica hybrids Subject RIV: CD - Macromolecular Chemistry

  12. Magnetic Nano-structures

    Institute of Scientific and Technical Information of China (English)

    姚永德

    2004-01-01

    Fabrication of magnetic nano-structures with dots array and wires has been paid attention recently due to the application of high-density magnetic recording. In this study, we fabricated the magnetic dots array and wires through several ways that ensure the arrangement of magnetic dots and wires to be the structures we designed. Their magnetic properties are studied experimentally.

  13. Silicon nanostructures for photonics

    International Nuclear Information System (INIS)

    Nanostructuring silicon is an effective way to turn silicon into a photonic material. In fact, low-dimensional silicon shows light amplification characteristics, non-linear optical effects, photon confinement in both one and two dimensions, photon trapping with evidence of light localization, and gas-sensing properties. (author)

  14. Nanostructured porous silicon: The winding road from photonics to cell scaffolds. A review.

    Directory of Open Access Journals (Sweden)

    Jacobo eHernandez-Montelongo

    2015-05-01

    Full Text Available For over 20 years nanostructured porous silicon (nanoPS has found a vast number of applications in the broad fields of photonics and optoelectronics, triggered by the discovery of its photoluminescent behavior in 1990. Besides, its biocompatibility, biodegradability, and bioresorbability make porous silicon (PSi an appealing biomaterial. These properties are largely a consequence of its particular susceptibility to oxidation, leading to the formation of silicon oxide which is readily dissolved by body fluids. This paper reviews the evolution of the applications of PSi and nanoPS from photonics through biophotonics, to their use as cell scaffolds, whether as an implantable substitute biomaterial, mainly for bony and ophthalmological tissues, or as an in-vitro cell conditioning support, especially for pluripotent cells. For any of these applications, PSi/nanoPS can be used directly after synthesis from Si wafers, upon appropriate surface modification processes, or as a composite biomaterial. Unedited studies of fluorescently active PSi structures for cell culture are brought to evidence the margin for new developments.

  15. Synthesis and Characterization of Chemically Etched Nanostructured Silicon

    KAUST Repository

    Mughal, Asad Jahangir

    2012-05-01

    Silicon is an essential element in today’s modern world. Nanostructured Si is a more recently studied variant, which has currently garnered much attention. When its spatial dimensions are confined below a certain limit, its optical properties change dramatically. It transforms from an indirect bandgap material that does not absorb or emit light efficiently into one which can emit visible light at room temperatures. Although much work has been conducted in understanding the properties of nanostructured Si, in particular porous Si surfaces, a clear understanding of the origin of photoluminescence has not yet been produced. Typical synthesis approaches used to produce nanostructured Si, in particular porous Si and nanocrystalline Si have involved complex preparations used at high temperatures, pressures, or currents. The purpose of this thesis is to develop an easier synthesis approach to produce nanostructured Si as well as arrive at a clearer understanding of the origin of photoluminescence in these systems. We used a simple chemical etching technique followed by sonication to produce nanostructured Si suspensions. The etching process involved producing pores on the surface of a Si substrate in a solution containing hydrofluoric acid and an oxidant. Nanocrystalline Si as well as nanoscale amorphous porous Si suspensions were successfully synthesized using this process. We probed into the phase, composition, and origin of photoluminescence in these materials, through the use of several characterization techniques. TEM and SEM were used to determine morphology and phase. FT-IR and XPS were employed to study chemical compositions, and steady state and time resolved optical spectroscopy techniques were applied to resolve their photoluminescent properties. Our work has revealed that the type of oxidant utilized during etching had a significant impact on the final product. When using nitric acid as the oxidant, we formed nanocrystalline Si suspensions composed of

  16. Biophotons in Relation to the Neural Signal Transmission and Processing%生物光子与神经信号传递和处理

    Institute of Scientific and Technical Information of China (English)

    戴甲培; 何晴; 刘丽雯; 汤仁东

    2013-01-01

    指出了针对神经信号传递和处理的主流理论的争论,即神经信号以电信号和化学信号的形式进行传递处理的理论虽然可以很好地解释感觉、运动、反射等神经系统的低级功能,但很难构建出解释大脑高级功能和精神活动的一般概念或原则。提出了神经回路中存在有生物光子(又称生物超弱发光)传递,并可能介导神经信号的传递和处理、参与人脑的高级功能和精神活动。综述了生物光子在神经回路中传递及介导神经信号传递处理的相关理论假说和实验研究。%The processing of neural information in neural circuits plays key roles in neural functions .It is well accepted that neural communication is mediated by bioelectricity and chemical molecules via the processes called bioelectrical and chemical transmission, respectively, which mainly occur in axons and synapses .Indeed, they seem to provide reasonable explanations for the basic functions and neural encoding of the nervous system , but difficultly to construct general accepted concepts or principles to provide reasonable explanations of neural functions and mental activities , such as perception , learning and memory , emotion and consciousness , etc.It has recently been suggested that biophotons , also called ultra-weak photon emissions , may play a potential role in neural signal transmission and processing , contributing to the understanding of the high functions of nervous system .In this paper , we briefly review the relevant experimental studies and theoretical hypothesis on neural signal transmission and processing via biophotons , and the possible mechanisms .

  17. Nanohole Structuring for Improved Performance of Hydrogenated Amorphous Silicon Photovoltaics.

    Science.gov (United States)

    Johlin, Eric; Al-Obeidi, Ahmed; Nogay, Gizem; Stuckelberger, Michael; Buonassisi, Tonio; Grossman, Jeffrey C

    2016-06-22

    While low hole mobilities limit the current collection and efficiency of hydrogenated amorphous silicon (a-Si:H) photovoltaic devices, attempts to improve mobility of the material directly have stagnated. Herein, we explore a method of utilizing nanostructuring of a-Si:H devices to allow for improved hole collection in thick absorber layers. This is achieved by etching an array of 150 nm diameter holes into intrinsic a-Si:H and then coating the structured material with p-type a-Si:H and a conformal zinc oxide transparent conducting layer. The inclusion of these nanoholes yields relative power conversion efficiency (PCE) increases of ∼45%, from 7.2 to 10.4% PCE for small area devices. Comparisons of optical properties, time-of-flight mobility measurements, and internal quantum efficiency spectra indicate this efficiency is indeed likely occurring from an improved collection pathway provided by the nanostructuring of the devices. Finally, we estimate that through modest optimizations of the design and fabrication, PCEs of beyond 13% should be obtainable for similar devices. PMID:27227369

  18. Geometric photovoltaics applied to amorphous silicon thin film solar cells

    Science.gov (United States)

    Kirkpatrick, Timothy

    Geometrically generalized analytical expressions for device transport are derived from first principles for a photovoltaic junction. Subsequently, conventional planar and unconventional coaxial and hemispherical photovoltaic architectures are applied to detail the device physics of the junction based on their respective geometry. For the conventional planar cell, the one-dimensional transport equations governing carrier dynamics are recovered. For the unconventional coaxial and hemispherical junction designs, new multi-dimensional transport equations are revealed. Physical effects such as carrier generation and recombination are compared for each cell architecture, providing insight as to how non-planar junctions may potentially enable greater energy conversion efficiencies. Numerical simulations are performed for arrays of vertically aligned, nanostructured coaxial and hemispherical amorphous silicon solar cells and results are compared to those from simulations performed for the standard planar junction. Results indicate that fundamental physical changes in the spatial dependence of the energy band profile across the intrinsic region of an amorphous silicon p-i-n junction manifest as an increase in recombination current for non-planar photovoltaic architectures. Despite an increase in recombination current, however, the coaxial architecture still appears to be able to surpass the efficiency predicted for the planar geometry, due to the geometry of the junction leading to a decoupling of optics and electronics.

  19. Nebulization of nanoparticulate amorphous or crystalline tacrolimus--single-dose pharmacokinetics study in mice.

    Science.gov (United States)

    Sinswat, Prapasri; Overhoff, Kirk A; McConville, Jason T; Johnston, Keith P; Williams, Robert O

    2008-08-01

    Developing a pulmonary composition of tacrolimus (TAC) provides direct access to the graft in lung transplant offering the possibility of high drug levels. The objective of this study was to investigate the physicochemical and pharmacokinetic characteristics of the nanostructured aggregates containing amorphous or crystalline nanoparticles of TAC produced by ultra-rapid freezing (URF). TAC and lactose (1:1 ratio; URF-TAC:LAC) and TAC alone (URF-TAC) were investigated for pulmonary delivery and compared to unprocessed TAC. X-ray diffraction (XRD) results indicated that URF-TAC was crystalline, whereas URF-TAC:LAC was amorphous. In vitro results revealed the superior physiochemical characteristics of both URF formulations compared to unprocessed TAC. The surface area of URF processed TAC was higher (25-29 m2/g) than that of the unprocessed TAC (0.53 m2/g) and subsequently enhanced dissolution rates. In addition, URF-TAC:LAC displayed the ability to supersaturate in the dissolution media to about 11 times the crystalline equilibrium solubility. Similar aerodynamic particle sizes of 2-3 microm, and fine particle fraction between 70% and 75% were found in both formulations. The local and systemic pharmacokinetic studies in mice showed similar AUC(0-24), higher Cmax, and lower Tmax for the URF-TAC:LAC compared to the URF-TAC. Nanostructured aggregates containing amorphous or crystalline nanoparticles of TAC were demonstrated to be effectively delivered via nebulization, with similar in vitro and in vivo performances. PMID:18406587

  20. Programmable SERS active substrates for chemical and biosensing applications using amorphous/crystalline hybrid silicon nanomaterial

    Science.gov (United States)

    Powell, Jeffery Alexander; Venkatakrishnan, Krishnan; Tan, Bo

    2016-01-01

    We present the creation of a unique nanostructured amorphous/crystalline hybrid silicon material that exhibits surface enhanced Raman scattering (SERS) activity. This nanomaterial is an interconnected network of amorphous/crystalline nanospheroids which form a nanoweb structure; to our knowledge this material has not been previously observed nor has it been applied for use as a SERS sensing material. This material is formed using a femtosecond synthesis technique which facilitates a laser plume ion condensation formation mechanism. By fine-tuning the laser plume temperature and ion interaction mechanisms within the plume, we are able to precisely program the relative proportion of crystalline Si to amorphous Si content in the nanospheroids as well as the size distribution of individual nanospheroids and the size of Raman hotspot nanogaps. With the use of Rhodamine 6G (R6G) and Crystal Violet (CV) chemical dyes, we have been able to observe a maximum enhancement factor of 5.38 × 106 and 3.72 × 106 respectively, for the hybrid nanomaterial compared to a bulk Si wafer substrate. With the creation of a silicon-based nanomaterial capable of SERS detection of analytes, this work demonstrates a redefinition of the role of nanostructured Si from an inactive to SERS active role in nano-Raman sensing applications.

  1. Improving Reversible Capacities of High-Surface Lithium Insertion Materials – The Case of Amorphous TiO2

    OpenAIRE

    Ganapathy, Swapna; Basak, Shibabrata; Lefering, Anton; Rogers, Edith; Zandbergen, Henny W; Wagemaker, Marnix

    2014-01-01

    Chemisorbed water and solvent molecules and their reactivity with components from the electrolyte in high-surface nano-structured electrodes remains a contributing factor toward capacity diminishment on cycling in lithium ion batteries due to the limit in maximum annealing temperature. Here, we report a marked improvement in the capacity retention of amorphous TiO2 by the choice of preparation solvent, control of annealing temperature, and the presence of surface functional groups. Careful he...

  2. Formation of nanostructured TiO2 by femtosecond laser irradiation of titanium in O2

    International Nuclear Information System (INIS)

    We used femtosecond laser irradiation of titanium metal in an oxidizing environment to form a highly stable surface layer of nanostructured amorphous titanium dioxide (TiO2). We studied the influence of atmospheric composition on these surface structures and found that gas composition and pressure affect the chemical composition of the surface layer but not the surface morphology. Incorporation of nitrogen is only possible when no oxygen is present in the surrounding atmosphere.

  3. Exoelectron analysis of amorphous silicon

    Science.gov (United States)

    Dekhtyar, Yu. D.; Vinyarskaya, Yu. A.

    1994-04-01

    The method based on registration of photothermostimulated exoelectron emission (PTSE) is used in the proposed new field of investigating the structural defects in amorphous silicon (a-Si). This method can be achieved if the sample under investigation is simultaneously heated and illuminated by ultraviolet light. The mechanism of PTSE from a-Si has been studied in the case of a hydrogenized amorphous silicon (a-Si:H) film grown by glow discharge method. The electronic properties and annealing of defects were analyzed in the study. It has been shown from the results that the PTSE from a-Si:H takes place as a prethreshold single-photon external photoeffect. The exoemission spectroscopy of a-Si:H was shown to be capable in the study of thermally and optically stimulated changes in the electronic structure of defects, their annealing, as well as diffusion of atomic particles, such as hydrogen.

  4. Amorphous metal based nanoelectromechanical switch

    KAUST Repository

    Mayet, Abdulilah M.

    2013-04-01

    Nanoelectromechanical (NEM) switch is an interesting ultra-low power option which can operate in the harsh environment and can be a complementary element in complex digital circuitry. Although significant advancement is happening in this field, report on ultra-low voltage (pull-in) switch which offers high switching speed and area efficiency is yet to be made. One key challenge to achieve such characteristics is to fabricate nano-scale switches with amorphous metal so the shape and dimensional integrity are maintained to achieve the desired performance. Therefore, we report a tungsten alloy based amorphous metal with fabrication process development of laterally actuated dual gated NEM switches with 100 nm width and 200 nm air-gap to result in <5 volts of actuation voltage (Vpull-in). © 2013 IEEE.

  5. Nanostructured sulfur cathodes

    KAUST Repository

    Yang, Yuan

    2013-01-01

    Rechargeable Li/S batteries have attracted significant attention lately due to their high specific energy and low cost. They are promising candidates for applications, including portable electronics, electric vehicles and grid-level energy storage. However, poor cycle life and low power capability are major technical obstacles. Various nanostructured sulfur cathodes have been developed to address these issues, as they provide greater resistance to pulverization, faster reaction kinetics and better trapping of soluble polysulfides. In this review, recent developments on nanostructured sulfur cathodes and mechanisms behind their operation are presented and discussed. Moreover, progress on novel characterization of sulfur cathodes is also summarized, as it has deepened the understanding of sulfur cathodes and will guide further rational design of sulfur electrodes. © 2013 The Royal Society of Chemistry.

  6. Growth of hybrid carbon nanostructures on iron-decorated ZnO nanorods.

    Science.gov (United States)

    Mbuyisa, Puleng N; Rigoni, Federica; Sangaletti, Luigi; Ponzoni, Stefano; Pagliara, Stefania; Goldoni, Andrea; Ndwandwe, Muzi; Cepek, Cinzia

    2016-04-01

    A novel carbon-based nanostructured material, which includes carbon nanotubes (CNTs), porous carbon, nanostructured ZnO and Fe nanoparticles, has been synthetized using catalytic chemical vapour deposition (CVD) of acetylene on vertically aligned ZnO nanorods (NRs). The deposition of Fe before the CVD process induces the presence of dense CNTs in addition to the variety of nanostructures already observed on the process done on the bare NRs, which range from amorphous graphitic carbon up to nanostructured dendritic carbon films, where the NRs are partially or completely etched. The combination of scanning electron microscopy and in situ photoemission spectroscopy indicate that Fe enhances the ZnO etching, and that the CNT synthesis is favoured by the reduced Fe mobility due to the strong interaction between Fe and the NRs, and to the presence of many defects, formed during the CVD process. Our results demonstrate that the resulting new hybrid shows a higher sensitivity to ammonia gas at ambient conditions (∼60 ppb) than the carbon nanostructures obtained without the aid of Fe, the bare ZnO NRs, or other one-dimensional carbon nanostructures, making this system of potential interest for environmental ammonia monitoring. Finally, in view of the possible application in nanoscale optoelectronics, the photoexcited carrier behaviour in these hybrid systems has been characterized by time-resolved reflectivity measurements. PMID:26916977

  7. A Universal Flying Amorphous Computer

    Czech Academy of Sciences Publication Activity Database

    Petrů, Lukáš; Wiedermann, Jiří

    Berlin: Springer, 2011 - (Calude, C.; Kari, J.; Petre, I.; Rozenberg, G.), s. 189-200. (Lecture Notes in Computer Science. 6714). ISBN 978-3-642-21340-3. ISSN 0302-9743. [UC 2011. Unconventional Computation /10/. Turku (FI), 06.06.2011-10.06.2011] R&D Projects: GA ČR GAP202/10/1333 Institutional research plan: CEZ:AV0Z10300504 Keywords : amorphous computing * model of computation * universality Subject RIV: IN - Informatics, Computer Science

  8. Amorphous silicon based betavoltaic devices

    OpenAIRE

    Wyrsch, N; Riesen, Y.; Franco, A; S. Dunand; Kind, H.; Schneider, S.; Ballif, C.

    2013-01-01

    Hydrogenated amorphous silicon betavoltaic devices are studied both by simulation and experimentally. Devices exhibiting a power density of 0.1 μW/cm2 upon Tritium exposure were fabricated. However, a significant degradation of the performance is taking place, especially during the first hours of the exposure. The degradation behavior differs from sample to sample as well as from published results in the literature. Comparisons with degradation from beta particles suggest an effect of tritium...

  9. Thermal transport in nanostructures

    OpenAIRE

    Nuo Yang; Xiangfan Xu; Gang Zhang; Baowen Li

    2013-01-01

    This review summarizes recent studies of thermal transport in nanoscaled semiconductors. Different from bulk materials, new physics and novel thermal properties arise in low dimensional nanostructures, such as the abnormal heat conduction, the size dependence of thermal conductivity, phonon boundary/edge scatterings. It is also demonstrated that phonons transport super-diffusively in low dimensional structures, in other words, Fourier's law is not applicable. Based on manipulating phonons, we...

  10. Nanostructured polymers for photonics

    OpenAIRE

    Chantal Paquet; Eugenia Kumacheva

    2008-01-01

    We review recent progress in the development of polymer nanostructured materials with periodic structures and compositions having applications in photonics and optical data storage. This review provides a brief description of the microfabrication and self-assembly methods used for the production of polymer materials with periodic structures, and highlights the properties and applications of photonic materials derived from block copolymers, colloid crystals, and microfabricated polymers. We co...

  11. Nanostructured Superhydrophobic Coatings

    Energy Technology Data Exchange (ETDEWEB)

    None

    2009-03-01

    This factsheet describes a research project that deals with the nanostructured superhydrophobic (SH) powders developed at ORNL. This project seeks to (1) improve powder quality; (2) identify binders for plastics, fiberglass, metal (steel being the first priority), wood, and other products such as rubber and shingles; (3) test the coated product for coating quality and durability under operating conditions; and (4) application testing and production of powders in quantity.

  12. Nanostructures for Medical Diagnostics

    OpenAIRE

    Md. Motasim Bellah; Shawn M. Christensen; Iqbal, Samir M.

    2012-01-01

    Nanotechnology is the art of manipulating materials on atomic or molecular scales especially to build nanoscale structures and devices. The field is expanding quickly, and a lot of work is ongoing in the design, characterization, synthesis, and application of materials, structures, devices, and systems by controlling shape and size at nanometer scale. In the last few years, much work has been focused on the use of nanostructures toward problems of biology and medicine. In this paper, we focus...

  13. Effects of applied radio frequency power on low-temperature catalytic-free nanostructured carbon nitride films by rf PECVD

    Science.gov (United States)

    Ritikos, Richard; Othman, Maisara; Abdul Rahman, Saadah

    2016-06-01

    Low-temperature catalytic-free carbon nitride, CN x nanostructured thin films were produced by using radio frequency (rf) plasma-enhanced chemical vapor deposition employing a parallel-plate electrode configuration. The effects of varying applied rf power, P rf (30-100 W), on the formation of these structures were studied. Aligned nanostructured CN x films were produced at P rf as low as 40 W, but uniform highly vertical-aligned CN x nanorods were produced at P rf of 60 and 80 W. This was induced by the presence of high ion bombardment on the growing films and the preferential bonding of isonitrile to aromatic bonds in the nanostructures. It was also observed that nitrogen incorporation is highest in this range and the structure and bonding in the nanostructure reflects those of typical polymeric/amorphous carbon nitride films.

  14. Surface properties and biocompatibility of nanostructured TiO2 film deposited by RF magnetron sputtering.

    Science.gov (United States)

    Majeed, Asif; He, Jie; Jiao, Lingrui; Zhong, Xiaoxia; Sheng, Zhengming

    2015-01-01

    Nanostructured TiO2 films are deposited on a silicon substrate using 150-W power from the RF magnetron sputtering at working pressures of 3 to 5 Pa, with no substrate bias, and at 3 Pa with a substrate bias of -50 V. X-ray diffraction (XRD) analysis reveals that TiO2 films deposited on unbiased as well as biased substrates are all amorphous. Surface properties such as surface roughness and wettability of TiO2 films, grown in a plasma environment, under biased and unbiased substrate conditions are reported according to the said parameters of RF power and the working pressures. Primary rat osteoblasts (MC3T3-E1) cells have been cultured on nanostructured TiO2 films fabricated at different conditions of substrate bias and working pressures. The effects of roughness and hydrophilicity of nanostructured TiO2 films on cell density and cell spreading have been discussed. PMID:25852353

  15. In Situ Transmission Electron Microscopy Observation of Nanostructural Changes in Phase-Change Memory

    KAUST Repository

    Meister, Stefan

    2011-04-26

    Phase-change memory (PCM) has been researched extensively as a promising alternative to flash memory. Important studies have focused on its scalability, switching speed, endurance, and new materials. Still, reliability issues and inconsistent switching in PCM devices motivate the need to further study its fundamental properties. However, many investigations treat PCM cells as black boxes; nanostructural changes inside the devices remain hidden. Here, using in situ transmission electron microscopy, we observe real-time nanostructural changes in lateral Ge2Sb2Te5 (GST) PCM bridges during switching. We find that PCM devices with similar resistances can exhibit distinct threshold switching behaviors due to the different initial distribution of nanocrystalline and amorphous domains, explaining variability of switching behaviors of PCM cells in the literature. Our findings show a direct correlation between nanostructure and switching behavior, providing important guidelines in the design and operation of future PCM devices with improved endurance and lower variability. © 2011 American Chemical Society.

  16. Colloidal Photoluminescent Amorphous Porous Silicon, Methods Of Making Colloidal Photoluminescent Amorphous Porous Silicon, And Methods Of Using Colloidal Photoluminescent Amorphous Porous Silicon

    KAUST Repository

    Chaieb, Sahraoui

    2015-04-09

    Embodiments of the present disclosure provide for a colloidal photoluminescent amorphous porous silicon particle suspension, methods of making a colloidal photoluminescent amorphous porous silicon particle suspension, methods of using a colloidal photoluminescent amorphous porous silicon particle suspension, and the like.

  17. Strength, Deformation and Fracture in Metallic Nanostructures

    Science.gov (United States)

    Gu, Xun Wendy

    An understanding of the mechanics of nanoscale metals and semiconductors is necessary for the safe and prolonged operation of nanostructured devices from transistors to nanowire- based solar cells to miniaturized electrodes. This is a fascinating but challenging pursuit because mechanical properties that are size-invariant in conventional materials, such as strength, ductility and fracture behavior, can depend critically on sample size when materials are reduced to sub-micron dimensions. In this thesis, the effect of nanoscale sample size, microstructure and structural geometry on mechanical strength, deformation and fracture are explored for several classes of solid materials. Nanocrystalline platinum nano-cylinders with diameters of 60 nm to 1 μm and 12 nm sized grains are fabricated and tested in compression. We find that nano-sized metals containing few grains weaken as sample diameter is reduced relative to grain size due to a change from deformation governed by internal grains to surface grain governed deformation. Fracture at the nanoscale is explored by performing in-situ SEM tension tests on nanocrystalline platinum and amorphous, metallic glass nano-cylinders containing purposely introduced structural flaws. It is found that failure location, mechanism and strength are determined by the stress concentration with the highest local stress whether this is at the structural flaw or a microstructural feature. Principles of nano-mechanics are used to design and test mechanically robust hierarchical nanostructures with structural and electrochemical applications. 2-photon lithography and electroplating are used to fabricate 3D solid Cu octet meso-lattices with micron-scale features that exhibit strength higher than that of bulk Cu. An in-situ SEM lithiation stage is developed and used to simultaneously examine morphological and electrochemical changes in Si-coated Cu meso-lattices that are of interest as high energy capacity electrodes for Li-ion batteries.

  18. Silicon and aluminum doping effects on the microstructure and properties of polymeric amorphous carbon films

    Science.gov (United States)

    Liu, Xiaoqiang; Hao, Junying; Xie, Yuntao

    2016-08-01

    Polymeric amorphous carbon films were prepared by radio frequency (R.F. 13.56 MHz) magnetron sputtering deposition. The microstructure evolution of the deposited polymeric films induced by silicon (Si) and aluminum(Al) doping were scrutinized through infrared spectroscopy, multi-wavelength Raman spectroscopy, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The comparative results show that Si doping can enhance polymerization and Al doping results in an increase in the ordered carbon clusters. Si and Al co-doping into polymeric films leads to the formation of an unusual dual nanostructure consisting of cross-linked polymer-like hydrocarbon chains and fullerene-like carbon clusters. The super-high elasticity and super-low friction coefficients (amorphous carbon films with different elements doping are also discussed in detail.

  19. Controlled synthesis and structure tunability of photocatalytically active mesoporous metal-based stannate nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Caihong [Department of Materials Science and Engineering and Institute of Materials Science, University of Connecticut, Storrs, CT 06269-3136 (United States); Chen, Haiyan [Mineral Physics Institute, Stony Brook University, Stony Brook, NY 11794 (United States); Ren, Zheng [Department of Materials Science and Engineering and Institute of Materials Science, University of Connecticut, Storrs, CT 06269-3136 (United States); Dardona, Sameh; Piech, Martin [Department of Physical Sciences, United Technologies Research Center, East Hartford, CT 06108 (United States); Gao, Haiyong [Department of Materials Science and Engineering and Institute of Materials Science, University of Connecticut, Storrs, CT 06269-3136 (United States); Gao, Pu-Xian, E-mail: puxian.gao@ims.uconn.edu [Department of Materials Science and Engineering and Institute of Materials Science, University of Connecticut, Storrs, CT 06269-3136 (United States)

    2014-03-01

    Highlights: • A generic process has been developed for fabricating metal stannate nanostructures by simple substitution solution reactions followed by post-thermal treatments. • Band energy alignment, high carrier mobility and large specific surface area are found to play key roles for the enabled high efficiency in stannate nanostructured photocatalysts. • The developed process can be easily extended to the fabrication of other complex metal oxide nanostructures. - Abstract: A variety of stannate nanostructures have been fabricated for UV photocatalysis, including zinc- and cadmium-based stannates. As the template nanostructures, high surface-area mesoporous metal hydroxystannate [ZnSn(OH){sub 6} and CdSn(OH){sub 6}] nanoparticles (>100 m{sup 2}/g) have been synthesized using a simple, low-temperature substitution chemical process with controlled porosity, morphology and crystallinity. Post-synthetic thermal treatments were employed to obtain amorphous ZnSnO{sub 3}, CdSnO{sub 3}, ilmenite CdSnO{sub 3}, and crystalline Zn{sub 2}SnO{sub 4}–SnO{sub 2} nanoparticles. As a result, the band gaps can be tuned from 5.4 eV to 3.3 eV and from 4.9 eV to 2.1 eV for Zn-based and Cd-based stannates, respectively. Amorphous ZnSnO{sub 3} porous nanoparticles showed highest activity toward dye degradation under UV illumination followed by the Zn{sub 2}SnO{sub 4}-SnO{sub 2} and ilmenite CdSnO{sub 3} nanostructures due to their beneficial band structure alignment, high conductivities, and high specific surface areas. This study may provide an important strategy for high throughput synthesis and screening of functional complex metal oxide nanomaterials, while the enabled stannate nanomaterials could be utilized in various applications.

  20. Low Temperature Growth of Nanostructured Diamond Films on Metals

    Science.gov (United States)

    Baker, Paul A.; Catledge, Shane A.; Vohra, Yogesh K.

    2001-01-01

    The field of nanocrystalline diamond and tetrahedral amorphous carbon films has been the focus of intense experimental activity in the last few years for applications in field emission display devices, optical windows, and tribological coatings, The choice of substrate used in most studies has typically been silicon. For metals, however, the thermal expansion mismatch between the diamond film and substrate gives rise to thermal stress that often results in delamination of the film. To avoid this problem in conventional CVD deposition low substrate temperatures (less than 700 C) have been used, often with the incorporation of oxygen or carbon monoxide to the feedgas mixture. Conventionally grown CVD diamond films are also rough and would require post-deposition polishing for most applications. Therefore, there is an obvious need to develop techniques for deposition of well-adhered, smooth nano-structured diamond films on metals for various tribological applications. In our work, nanostructured diamond films are grown on a titanium alloy substrate using a two-step deposition process. The first step is performed at elevated temperature (820 C) for 30 minutes using a H2/CH4/N2 gas mixture in order to grow a thin (approx. 600 nm) nanostructured diamond layer and improve film adhesion. The remainder of the deposition involves growth at low temperature (less than 600 C) in a H2/CH4/O2 gas mixture. Laser reflectance Interferometry (LRI) pattern during growth of a nanostructured diamond film on Ti-6Al-4V alloy. The first 30 minutes are at a high temperature of 820 C and the rest of the film is grown at a low temperature of 580 T. The fringe pattern is observed till the very end due to extremely low surface roughness of 40 nm. The continuation of the smooth nanostructured diamond film growth during low temperature deposition is confirmed by in-situ laser reflectance interferometry and by post-deposition micro-Raman spectroscopy and surface profilometry. Similar experiments

  1. Role of current profiles and atomic force microscope tips on local electric crystallization of amorphous silicon

    Czech Academy of Sciences Publication Activity Database

    Verveniotis, Elisseos; Rezek, Bohuslav; Šípek, Emil; Stuchlík, Jiří; Kočka, Jan

    2010-01-01

    Roč. 518, č. 21 (2010), s. 5965-5970. ISSN 0040-6090 R&D Projects: GA ČR GD202/09/H041; GA MŠk(CZ) LC06040; GA AV ČR KAN400100701; GA MŠk LC510 Institutional research plan: CEZ:AV0Z10100521 Keywords : amorphous materials * atomic force microscopy (AFM) * conductivity * crystallization * nanostructures * silicon * nickel Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.909, year: 2010

  2. Nanostructuring superconducting vortex matter with focused ion beams

    International Nuclear Information System (INIS)

    Highlights: • Nanostructuring vortex matter with focused ion beams. • Nanofabrication produces high vortex density gradients. • Patterning gives nanocrystalline vortex lattice. - Abstract: Focused ion beams provide new opportunities to create small nanofabricated structures. Materials where this technique is successfully applied are different from those that are widely used in e-beam or photolithography processes. Arrays of holes have been fabricated in several layered superconductors, such as the transition metal dichalcogenides. A focused ion beam system can be also used to deposit superconducting material. A Ga beam is used to decompose a precusor W(CO)6 molecule, giving an amorphous mixture of W–C–Ga–O which is superconducting below liquid helium temperatures. The amorphous nature of the deposit gives isotropic superconducting features, and vortex pinning is determined by the surface topography (or film thickness). Here we present vortex lattice images in an amorphous thin film with a nanofabricated array of dots. We find vortex confinement within the dots and inhomogeneous vortex distributions with large magnetic field gradients (around a Tesla in 10–20 nm). We discuss scaling behavior of the vortex lattice after nanofabrication

  3. Nanostructuring superconducting vortex matter with focused ion beams

    Energy Technology Data Exchange (ETDEWEB)

    Guillamón, I. [Laboratorio de Bajas Temperaturas, Departamento de Física de la Materia Condensada, Instituto de Ciencia de Materiales Nicolás Cabrera, Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Unidad Asociada de Bajas Temperaturas y Altos Campos Magnéticos, UAM, CSIC, Cantoblanco, E-28049 Madrid (Spain); Suderow, H., E-mail: hermann.suderow@uam.es [Laboratorio de Bajas Temperaturas, Departamento de Física de la Materia Condensada, Instituto de Ciencia de Materiales Nicolás Cabrera, Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Unidad Asociada de Bajas Temperaturas y Altos Campos Magnéticos, UAM, CSIC, Cantoblanco, E-28049 Madrid (Spain); Kulkarni, P.; Vieira, S. [Laboratorio de Bajas Temperaturas, Departamento de Física de la Materia Condensada, Instituto de Ciencia de Materiales Nicolás Cabrera, Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Unidad Asociada de Bajas Temperaturas y Altos Campos Magnéticos, UAM, CSIC, Cantoblanco, E-28049 Madrid (Spain); Córdoba, R.; Sesé, J. [Laboratorio de Microscopías Avanzadas (LMA) – Instituto de Nanociencia de Aragón (INA), Universidad de Zaragoza, Zaragoza 50009 (Spain); Departamento de Física de la Materia Condensada, Universidad de Zaragoza, 50009 Zaragoza (Spain); and others

    2014-08-15

    Highlights: • Nanostructuring vortex matter with focused ion beams. • Nanofabrication produces high vortex density gradients. • Patterning gives nanocrystalline vortex lattice. - Abstract: Focused ion beams provide new opportunities to create small nanofabricated structures. Materials where this technique is successfully applied are different from those that are widely used in e-beam or photolithography processes. Arrays of holes have been fabricated in several layered superconductors, such as the transition metal dichalcogenides. A focused ion beam system can be also used to deposit superconducting material. A Ga beam is used to decompose a precusor W(CO){sub 6} molecule, giving an amorphous mixture of W–C–Ga–O which is superconducting below liquid helium temperatures. The amorphous nature of the deposit gives isotropic superconducting features, and vortex pinning is determined by the surface topography (or film thickness). Here we present vortex lattice images in an amorphous thin film with a nanofabricated array of dots. We find vortex confinement within the dots and inhomogeneous vortex distributions with large magnetic field gradients (around a Tesla in 10–20 nm). We discuss scaling behavior of the vortex lattice after nanofabrication.

  4. The physics and applications of amorphous semiconductors

    CERN Document Server

    Madan, Arun

    1988-01-01

    This comprehensive, detailed treatise on the physics and applications of the new emerging technology of amorphous semiconductors focuses on specific device research problems such as the optimization of device performance. The first part of the book presents hydrogenated amorphous silicon type alloys, whose applications include inexpensive solar cells, thin film transistors, image scanners, electrophotography, optical recording and gas sensors. The second part of the book discusses amorphous chalcogenides, whose applications include electrophotography, switching, and memory elements. This boo

  5. Amorphous powders for inhalation drug delivery.

    Science.gov (United States)

    Chen, Lan; Okuda, Tomoyuki; Lu, Xiang-Yun; Chan, Hak-Kim

    2016-05-01

    For inhalation drug delivery, amorphous powder formulations offer the benefits of increased bioavailability for poorly soluble drugs, improved biochemical stability for biologics, and expanded options of using various drugs and their combinations. However, amorphous formulations usually have poor physicochemical stability. This review focuses on inhalable amorphous powders, including the production methods, the active pharmaceutical ingredients and the excipients with a highlight on stabilization of the particles. PMID:26780404

  6. Amorphous Phase Properties Of Oriented Polyethylene Solids

    OpenAIRE

    Zahran, R. R; Kardos, J. L.

    1993-01-01

    Solid-state deformation of polyethylene results in a preferential orientation of both crystalline and amorphous regions. Usually, one major problem in the prediction of the mechanical and thermal expansion properties of anisotropic polyethylene lies in determining values for the amorphous phase properties and, particularly, at a given level of solid-state deformation. This paper outlines simple procedures for determining the two-dimensional amorphous orientation function and values for the...

  7. Nanoparticle Decorated Ultrathin Porous Nanosheets as Hierarchical Co3O4 Nanostructures for Lithium Ion Battery Anode Materials

    DEFF Research Database (Denmark)

    Mujtaba, Jawayria; Sun, Hongyu; Huang, Guoyong;

    2016-01-01

    We report a facile synthesis of a novel cobalt oxide (Co3O4) hierarchical nanostructure, in which crystalline core-amorphous shell Co3O4 nanoparticles with a bimodal size distribution are uniformly dispersed on ultrathin Co3O4 nanosheets. When tested as anode materials for lithium ion batteries...

  8. Quantum Transport in Semiconductor Nanostructures

    OpenAIRE

    Beenakker, C. W. J.; Houten, van, H.

    2004-01-01

    I. Introduction (Preface, Nanostructures in Si Inversion Layers, Nanostructures in GaAs-AlGaAs Heterostructures, Basic Properties). II. Diffusive and Quasi-Ballistic Transport (Classical Size Effects, Weak Localization, Conductance Fluctuations, Aharonov-Bohm Effect, Electron-Electron Interactions, Quantum Size Effects, Periodic Potential). III. Ballistic Transport (Conduction as a Transmission Problem, Quantum Point Contacts, Coherent Electron Focusing, Collimation, Junction Scattering, Tunn...

  9. Optical switching systems using nanostructures

    DEFF Research Database (Denmark)

    Stubkjær, Kristian

    2004-01-01

    High capacity multiservice optical networks require compact and efficient switches. The potential benefits of optical switch elements based on nanostructured material are reviewed considering various material systems.......High capacity multiservice optical networks require compact and efficient switches. The potential benefits of optical switch elements based on nanostructured material are reviewed considering various material systems....

  10. Hydrophobic transition in porous amorphous silica

    International Nuclear Information System (INIS)

    Realistic models of amorphous silica surfaces with different silanol densities are built using Monte Carlo annealing. Water-silica interfaces are characterized by their energy interaction maps, adsorption isotherms, self-diffusion coefficients, and Poiseuille flows. A hydrophilic to hydrophobic transition appears as the surface becomes purely siliceous. These results imply significant consequences for the description of surfaces. First, realistic models are required for amorphous silica interfaces. Second, experimental amorphous silica hydrophilicity is attributed to charged or uncharged defects, and not to amorphousness. In addition, auto irradiation in nuclear waste glass releases hydrogen atoms from silanol groups and can induce such a transition. (authors)

  11. Fullerene nanostructures, monolayers and thin films

    International Nuclear Information System (INIS)

    The interaction of submonolayer, monolayer and multilayer coverages of C60 with the Ag/Si(111)-(√3x√3)R30 deg. (√3Ag/Si) and Si(111)-7x7 surfaces has been investigated using atomic force microscopy (AFM), photoelectron spectroscopy (PES) and ultra high vacuum scanning tunneling microscopy (UHV-STM). It is shown that it is possible to preserve the √3Ag/Si surface, normally corrupted by exposure to air, in ambient conditions when immersed beneath a few layers of C60 molecules. Upon removal of the fullerene layers in the UHV-STM some corruption is observed which is linked to the morphology of the fullerene film (defined by the nature of the interaction of C60 with √3Ag/Si). This technique opens up the possibility of performing experiments on the clean √3Ag/Si surface outside of UHV conditions. With the discovery of techniques whereby structures may be formed that are composed of only a few atoms/molecules, there is a need to perform electrical measurements in order to probe the fascinating properties of these 'nano-scale' devices. Using AFM, PES and STM evaporated metals and ion implantation have been investigated as materials for use in forming sub-micron scale contacts to nanostructures. It is found that ion implantation is a more promising approach after studying the response to annealing of treated surfaces. Electrical measurements between open/short circuited contacts and through Ag films clearly demonstrate the validity of the method, further confirmed by a PES study which probes the chemical nature of the near surface region of ion-implanted samples. Attempts have been made to form nanostructure templates between sub-micron scale contacts as a possible precursor to forming nanostructures. The bonding state of C60 molecules on the Si(111)-7x7 surface has been in dispute for many years. To properly understand the system a comprehensive AFM, PES and STM study has been performed. PES results indicate covalent bond formation, with the number of bonds

  12. Semiconductors and semimetals nanostructured systems

    CERN Document Server

    Willardson, Robert K; Beer, Albert C; Reed, Mark A

    1992-01-01

    This is the first available volume to consolidate prominent topics in the emerging field of nanostructured systems. Recent technological advancements have led to a new era of nanostructure physics, allowing for the fabrication of nanostructures whose behavior is dominated by quantum interference effects. This new capability has enthused the experimentalist and theorist alike. Innumerable possibilities have now opened up for physical exploration and device technology on the nanoscale. This book, with contributions from five pioneering researchers, will allow the expert and novice alike to explore a fascinating new field.Provides a state-of-the-art review of quantum-scale artificially nanostructured electronic systemsIncludes contributions by world-known experts in the fieldOpens the field to the non-expert with a concise introductionFeatures discussions of:Low-dimensional condensed matter physicsProperties of nanostructured, ultrasmall electronic systemsMesoscopic physics and quantum transportPhysics of 2D ele...

  13. Inelastic scattering from amorphous solids

    International Nuclear Information System (INIS)

    The potential of inelastic neutron scattering techniques for surveying various aspects of the dynamics of amorphous solids is briefly reviewed. The recent use of the Intense Pulsed Neutron Source to provide detailed information on the optical vibrations of glasses is discussed in more detail. The density of states represents an averaged quantity which gives information about the general characteristics of the structure and bonding. More extensive information can be obtained by studying the detailed wavevector dependence of the dynamic structure factor. 15 refs., 7 figs

  14. Plasma Deposition of Amorphous Silicon

    Science.gov (United States)

    Calcote, H. F.

    1982-01-01

    Strongly adhering films of silicon are deposited directly on such materials as Pyrex and Vycor (or equivalent materials) and aluminum by a non-equilibrium plasma jet. Amorphous silicon films are formed by decomposition of silicon tetrachloride or trichlorosilane in the plasma. Plasma-jet technique can also be used to deposit an adherent silicon film on aluminum from silane and to dope such films with phosphorus. Ability to deposit silicon films on such readily available, inexpensive substrates could eventually lead to lower cost photovoltaic cells.

  15. Amorphous silicon based solar cells

    OpenAIRE

    Al Tarabsheh, Anas

    2007-01-01

    This thesis focuses on the deposition of hydrogenated amorphous silicon (a-Si:H) films bymeans of plasma enhanced chemical vapour deposition (PECVD). This technique allows the growth of device quality a-Si:H at relatively low deposition temperatures, below 140 °C and, therefore, enables the use of low-cost substrates, e.g. plastic foils. The maximum efficiencies of a-Si:H solar cells in this work are η= 6.8 % at a deposition temperature Tdep = 180 °C and η = 4.9 % at a deposition ...

  16. Amorphous silicon based radiation detectors

    International Nuclear Information System (INIS)

    We describe the characteristics of thin(1 μm) and thick (>30μm) hydrogenated amorphous silicon p-i-n diodes which are optimized for detecting and recording the spatial distribution of charged particles, x-rays and γ rays. For x-ray, γ ray, and charged particle detection we can use thin p-i-n photosensitive diode arrays coupled to evaporated layers of suitable scintillators. For direct detection of charged particles with high resistance to radiation damage, we use the thick p-i-n diode arrays. 13 refs., 7 figs

  17. Nanoindentation of Carbon Nanostructures.

    Science.gov (United States)

    Kumar, Dinesh; Singh, Karamjit; Verma, Veena; Bhatti, H S

    2016-06-01

    In the present research paper carbon nanostructures viz. single walled carbon nanotubes, multi-walled carbon nanotubes, single walled carbon nanohorns and graphene nanoplatelets have been synthesized by CVD technique, hydrothermal method, DC arc discharge method in liquid nitrogen and microwave technique respectively. After synthesis 5 mm thick pallets of given nanomaterial are prepared by making a paste in isopropyl alcohol and using polyvinylidene difluoride as a binder and then these pallets were used for nanoindentation measurements. Hardness, reduced modulus, stiffness, contact height and contact area have been measured using nanoindenter. PMID:27427726

  18. Nanostructured polymers for photonics

    Directory of Open Access Journals (Sweden)

    Chantal Paquet

    2008-04-01

    Full Text Available We review recent progress in the development of polymer nanostructured materials with periodic structures and compositions having applications in photonics and optical data storage. This review provides a brief description of the microfabrication and self-assembly methods used for the production of polymer materials with periodic structures, and highlights the properties and applications of photonic materials derived from block copolymers, colloid crystals, and microfabricated polymers. We conclude with a summary of current and future research efforts and opportunities in the development of polymer materials for photonic applications.

  19. Polymeric amorphous carbon as p-type window within amorphous silicon solar cells

    NARCIS (Netherlands)

    Khan, R.U.A.; Silva, S.R.P.; Van Swaaij, R.A.C.M.M.

    2003-01-01

    Amorphous carbon (a-C) has been shown to be intrinsically p-type, and polymeric a-C (PAC) possesses a wide Tauc band gap of 2.6 eV. We have replaced the p-type amorphous silicon carbide layer of a standard amorphous silicon solar cell with an intrinsic ultrathin layer of PAC. The thickness of the p

  20. Laser surface treatment of amorphous metals

    Science.gov (United States)

    Katakam, Shravana K.

    Amorphous materials are used as soft magnetic materials and also as surface coatings to improve the surface properties. Furthermore, the nanocrystalline materials derived from their amorphous precursors show superior soft magnetic properties than amorphous counter parts for transformer core applications. In the present work, laser based processing of amorphous materials will be presented. Conventionally, the nanocrystalline materials are synthesized by furnace heat treatment of amorphous precursors. Fe-based amorphous/nanocrystalline materials due to their low cost and superior magnetic properties are the most widely used soft magnetic materials. However, achieving nanocrystalline microstructure in Fe-Si-B ternary system becomes very difficult owing its rapid growth rate at higher temperatures and sluggish diffusion at low temperature annealing. Hence, nanocrystallization in this system is achieved by using alloying additions (Cu and Nb) in the ternary Fe-Si-B system. Thus, increasing the cost and also resulting in reduction of saturation magnetization. laser processing technique is used to achieve extremely fine nanocrystalline microstructure in Fe-Si-B amorphous precursor. Microstructure-magnetic Property-laser processing co-relationship has been established for Fe-Si-B ternary system using analytical techniques. Laser processing improved the magnetic properties with significant increase in saturation magnetization and near zero coercivity values. Amorphous materials exhibit excellent corrosion resistance by virtue of their atomic structure. Fe-based amorphous materials are economical and due to their ease of processing are of potential interest to synthesize as coatings materials for wear and corrosion resistance applications. Fe-Cr-Mo-Y-C-B amorphous system was used to develop thick coatings on 4130 Steel substrate and the corrosion resistance of the amorphous coatings was improved. It is also shown that the mode of corrosion depends on the laser processing

  1. Photoexcitation-induced processes in amorphous semiconductors

    International Nuclear Information System (INIS)

    Theories for the mechanism of photo-induced processes of photodarkening (PD), volume expansion (VE) in amorphous chalcogenides are presented. Rates of spontaneous emission of photons by radiative recombination of excitons in amorphous semiconductors are also calculated and applied to study the excitonic photoluminescence in a-Si:H. Results are compared with previous theories

  2. Applied research on amorphous magnetic materials

    International Nuclear Information System (INIS)

    Amorphous magnetic materials are increasingly becoming an industrial reality, which a variety of applications to electronics and electrical engineering. Many research lines are in progress for what concerns the production techniques, the understanding of the structure and properties of amorphous ribbons, the optimization and extension of their applications. The fast quenching methods used to obtain amorphous materials will first be reviewed, also describing an experimental apparatus set up by the authors for laboratory investigations of rapid solidification processes. Because of the non equilibrium structure of amorphous metallic alloys, various relaxation effects are expected to occur, which may partially limit the use of these materials. Studies of these relaxation phenomena, performed by different methods, including Moessbauer spectroscopy will also be reviewed, showing their importance in better understanding the amorphous structure. Finally much attention will be devoted to actual applications of amorphous magnetic materials. Emphasis will be placed on the prospective applications of amorphous ribbons characterized by very low power losses to magnetic cores of distribution transformers, pointing to the possible advantages, but also to the technical problems involved with the substitution of crystalline laminations with the new amorphous materials. (orig.)

  3. Electron tunnelling into amorphous germanium and silicon.

    Science.gov (United States)

    Smith, C. W.; Clark, A. H.

    1972-01-01

    Measurements of tunnel conductance versus bias, capacitance versus bias, and internal photoemission were made in the systems aluminum-oxide-amorphous germanium and aluminium-oxide-amorphous silicon. A function was extracted which expresses the deviation of these systems from the aluminium-oxide-aluminium system.

  4. Band Gaps of an Amorphous Photonic Materials

    Institute of Scientific and Technical Information of China (English)

    WANG Yi-Quan; FENG Zhi-Fang; HU Xiao-Yong; CHENG Bing-Ying; ZHANG Dao-Zhong

    2004-01-01

    @@ A new kind of amorphous photonic materials is presented. Both the simulated and experimental results show that although the disorder of the whole dielectric structure is strong, the amorphous photonic materials have two photonic gaps. This confirms that the short-range order is an essential factor for the formation of the photonic gaps.

  5. Theoretical Considerations in Developing Amorphous Solid Dispersions

    DEFF Research Database (Denmark)

    Laitinen, Riikka; Priemel, Petra Alexandra; Surwase, Sachin; Graeser, Kirsten; Strachan, Clare J.; Grohganz, Holger; Rades, Thomas

    Before pursuing the laborious route of amorphous solid dispersion formulation and development, which is the topic of many of the subsequent chapters in this book, the formulation scientist would benefit from a priori knowledge whether the amorphous route is a viable one for a given drug and how m...

  6. Plasma Spray Forming of Nanostructured Composite Coatings

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The nanostructure composite coating is obtained via plasma spraying of Al2O3-13 wt pct TiO2 powder. Brittle and hard lamella results from melted nanostructured powder. Ductile nanostructured matrix forms from unmelted nanostructured particles. Through the adjustment of constituent and nanostructure, hardness/strength and toughness/ductility are balanced and overall properties of the structure composite are achieved.

  7. Arrays of ZnO nanocolumns for 3-dimensional very thin amorphous and microcrystalline silicon solar cells

    International Nuclear Information System (INIS)

    We report on the hydrothermal growth of high quality arrays of single crystalline zinc oxide (ZnO) nanocolumns, oriented perpendicularly to the transparent conductive oxide substrate. In order to obtain precisely defined spacing and arrangement of ZnO nanocolumns over an area up to 0.5 cm2, we used electron beam lithography. Vertically aligned ZnO (multicrystalline or single crystals) nanocolumns were grown in an aqueous solution of zinc nitrate hexahydrate and hexamethylenetetramine at 95 °C, with a growth rate 0.5 ÷ 1 μm/h. The morphology of the nanostructures was visualized by scanning electron microscopy. Such nanostructured ZnO films were used as a substrate for the recently developed 3-dimensional thin film silicon (amorphous, microcrystalline) solar cell, with a high efficiency potential. The photoelectrical and optical properties of the ZnO nanocolumns and the silicon absorber layers of these type nanostructured solar cells were investigated in details. - Highlights: • Vertically-oriented ZnO nanocolumns were grown by hydrothermal method. • The ZnO nanocolumns were grown over an area of 0.5 cm2. • For precise arrangement of the ZnO nanocolumns electron beam lithography was used. • We report on 3-D design of nanostructured solar cell. • Optical thickness of nanostructured cell was three times higher compared to flat cell

  8. Effect of flame conditions on abrasive wear performance of HVOF sprayed nanostructured WC-12Co coatings

    Institute of Scientific and Technical Information of China (English)

    WANG Yu-yue; LI Chang-jiu; MA Jian; YANG Guan-jun

    2004-01-01

    Nanostructured WC-12Co coatings were deposited by high velocity oxy-fuel (HVOF) spraying with an agglomerated powder. The effect of flame conditions on the microstructure of the nanostructured coatings was investigated. The wear properties of the coatings were characterized using a dry rubber-wheel wear test. The results show that the nanostructured WC-Co coatings consist of WC, W2C, W and an amorphous binder phase. The microstructure of the coating is significantly influenced by the ratio of oxygen flow to fuel flow. Under the lower ratio of oxygen/fuel flow, the nanostructured coating presents a relative dense microstructure and severe decarburization of WC phase occurs during spraying. With increasing ratio of oxygen/fuel flow, the bonding of WC particles in the coating becomes loose resulting from the original structure of feedstock and the decarburization of WC becomes less owing to limited heating to the powder. Both the decarburization of WC particles in spraying and the bonding among WC particles in the coatings affect the wear performance. The examination of the worn surfaces of the nanostructured coatings reveals that the dominant wear mechanisms would be spalling from the interface of WCCo splats when spray particles undergo a limited melting. While the melting state of the spray particles is improved,the dominant wear mechanisms become the plastic deformation and plowing of the matrix and spalling of WC particles from the matrix.

  9. Nanostructures formed on carbon-based materials with different levels of crystallinity using oxygen plasma treatment

    Energy Technology Data Exchange (ETDEWEB)

    Ko, Tae-Jun [Institute for Multidisciplinary Convergence of Matter, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Department of Materials Science and Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of); Jo, Wonjin; Lee, Heon Ju [Institute for Multidisciplinary Convergence of Matter, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Oh, Kyu Hwan [Department of Materials Science and Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of); Moon, Myoung-Woon, E-mail: mwmoon@kist.re.kr [Institute for Multidisciplinary Convergence of Matter, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of)

    2015-09-01

    Nanostructure formation was explored for various carbon-based materials, such as diamond, carbon fiber, polyethylene terephthalate and poly (methyl methacrylate), which have different levels of crystallinity, ranging from perfect crystal to polymeric amorphous. After treatment of oxygen plasma glow discharge, the nanostructures on these carbon-based materials were found to evolve via preferential etching due to the co-deposition of metal elements sputtered from the metal cathode plate. Local islands or clusters formed by the metal co-deposition have a low etching rate compared to pristine regions on each material, resulting in anisotropic patterns on the carbon-based materials. This pattern formation mechanism was confirmed by covering the cathode or preventing the co-deposition of metallic sources with a polymeric material. Regardless of the level of crystallinity of the carbon-based materials, no patterns were observed on the surfaces covered with the polymeric material, and the surfaces were uniformly etched. It was found that the materials with low crystallinity had a high etching rate due to low carbon atom density, which thus easily formed high-aspect-ratio nanostructures for the same plasma treatment duration. - Highlight: • Reactive ion etching & metal deposition were occurred in oxygen plasma treatment. • High-aspect-ratio nanostructures can be fabricated on carbon-based materials. • Materials with low crystallinity easily formed high-aspect-ratio nanostructure. • Amount of etching inhibitors affects the pattern formation and configuration.

  10. Nanostructures formed on carbon-based materials with different levels of crystallinity using oxygen plasma treatment

    International Nuclear Information System (INIS)

    Nanostructure formation was explored for various carbon-based materials, such as diamond, carbon fiber, polyethylene terephthalate and poly (methyl methacrylate), which have different levels of crystallinity, ranging from perfect crystal to polymeric amorphous. After treatment of oxygen plasma glow discharge, the nanostructures on these carbon-based materials were found to evolve via preferential etching due to the co-deposition of metal elements sputtered from the metal cathode plate. Local islands or clusters formed by the metal co-deposition have a low etching rate compared to pristine regions on each material, resulting in anisotropic patterns on the carbon-based materials. This pattern formation mechanism was confirmed by covering the cathode or preventing the co-deposition of metallic sources with a polymeric material. Regardless of the level of crystallinity of the carbon-based materials, no patterns were observed on the surfaces covered with the polymeric material, and the surfaces were uniformly etched. It was found that the materials with low crystallinity had a high etching rate due to low carbon atom density, which thus easily formed high-aspect-ratio nanostructures for the same plasma treatment duration. - Highlight: • Reactive ion etching & metal deposition were occurred in oxygen plasma treatment. • High-aspect-ratio nanostructures can be fabricated on carbon-based materials. • Materials with low crystallinity easily formed high-aspect-ratio nanostructure. • Amount of etching inhibitors affects the pattern formation and configuration

  11. Neutron irradiation induced amorphization of silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

    Snead, L.L.; Hay, J.C. [Oak Ridge National Lab., TN (United States)

    1998-09-01

    This paper provides the first known observation of silicon carbide fully amorphized under neutron irradiation. Both high purity single crystal hcp and high purity, highly faulted (cubic) chemically vapor deposited (CVD) SiC were irradiated at approximately 60 C to a total fast neutron fluence of 2.6 {times} 10{sup 25} n/m{sup 2}. Amorphization was seen in both materials, as evidenced by TEM, electron diffraction, and x-ray diffraction techniques. Physical properties for the amorphized single crystal material are reported including large changes in density ({minus}10.8%), elastic modulus as measured using a nanoindentation technique ({minus}45%), hardness as measured by nanoindentation ({minus}45%), and standard Vickers hardness ({minus}24%). Similar property changes are observed for the critical temperature for amorphization at this neutron dose and flux, above which amorphization is not possible, is estimated to be greater than 130 C.

  12. Solid-state diffusion in amorphous zirconolite

    Energy Technology Data Exchange (ETDEWEB)

    Yang, C.; Dove, M. T.; Trachenko, K. [School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom); Zarkadoula, E. [School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom); Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6138 (United States); Todorov, I. T. [STFC Daresbury Laboratory, Warrington WA4 1EP (United Kingdom); Geisler, T. [Steinmann-Institut für Geologie, Mineralogie und Paläontologie, University of Bonn, D-53115 Bonn (Germany); Brazhkin, V. V. [Institute for High Pressure Physics, RAS, 142190 Moscow (Russian Federation)

    2014-11-14

    We discuss how structural disorder and amorphization affect solid-state diffusion, and consider zirconolite as a currently important case study. By performing extensive molecular dynamics simulations, we disentangle the effects of amorphization and density, and show that a profound increase of solid-state diffusion takes place as a result of amorphization. Importantly, this can take place at the same density as in the crystal, representing an interesting general insight regarding solid-state diffusion. We find that decreasing the density in the amorphous system increases pre-factors of diffusion constants, but does not change the activation energy in the density range considered. We also find that atomic species in zirconolite are affected differently by amorphization and density change. Our microscopic insights are relevant for understanding how solid-state diffusion changes due to disorder and for building predictive models of operation of materials to be used to encapsulate nuclear waste.

  13. Neutron irradiation induced amorphization of silicon carbide

    International Nuclear Information System (INIS)

    This paper provides the first known observation of silicon carbide fully amorphized under neutron irradiation. Both high purity single crystal hcp and high purity, highly faulted (cubic) chemically vapor deposited (CVD) SiC were irradiated at approximately 60 C to a total fast neutron fluence of 2.6 x 1025 n/m2. Amorphization was seen in both materials, as evidenced by TEM, electron diffraction, and x-ray diffraction techniques. Physical properties for the amorphized single crystal material are reported including large changes in density (-10.8%), elastic modulus as measured using a nanoindentation technique (-45%), hardness as measured by nanoindentation (-45%), and standard Vickers hardness (-24%). Similar property changes are observed for the critical temperature for amorphization at this neutron dose and flux, above which amorphization is not possible, is estimated to be greater than 130 C

  14. Structure, thermodynamics, and crystallization of amorphous hafnia

    International Nuclear Information System (INIS)

    We investigate theoretically amorphous hafnia using the first principles melt and quench method. We identify two types of amorphous structures of hafnia. Type I and type II are related to tetragonal and monoclinic hafnia, respectively. We find type II structure to show stronger disorder than type I. Using the phonon density of states, we calculate the specific heat capacity for type II amorphous hafnia. Using the nudged elastic band method, we show that the averaged transition barrier between the type II amorphous hafnia and monoclinic phase is approximately 0.09 eV/HfO2. The crystallization temperature is estimated to be 421 K. The calculations suggest an explanation for the low thermal stability of amorphous hafnia

  15. Locomotion of Amorphous Surface Robots

    Science.gov (United States)

    Bradley, Arthur T. (Inventor)

    2016-01-01

    An amorphous robot includes a compartmented bladder containing fluid, a valve assembly, and an outer layer encapsulating the bladder and valve assembly. The valve assembly draws fluid from a compartment(s) and discharges the drawn fluid into a designated compartment to displace the designated compartment with respect to the surface. Another embodiment includes elements each having a variable property, an outer layer that encapsulates the elements, and a control unit. The control unit energizes a designated element to change its variable property, thereby moving the designated element. The elements may be electromagnetic spheres with a variable polarity or shape memory polymers with changing shape and/or size. Yet another embodiment includes an elongated flexible tube filled with ferrofluid, a moveable electromagnet, an actuator, and a control unit. The control unit energizes the electromagnet and moves the electromagnet via the actuator to magnetize the ferrofluid and lengthen the flexible tube.

  16. Defects in semiconductor nanostructures

    Indian Academy of Sciences (India)

    Vijay A Singh; Manoj K Harbola; Praveen Pathak

    2008-02-01

    Impurities play a pivotal role in semiconductors. One part in a million of phosphorous in silicon alters the conductivity of the latter by several orders of magnitude. Indeed, the information age is possible only because of the unique role of shallow impurities in semiconductors. Although work in semiconductor nanostructures (SN) has been in progress for the past two decades, the role of impurities in them has been only sketchily studied. We outline theoretical approaches to the electronic structure of shallow impurities in SN and discuss their limitations. We find that shallow levels undergo a SHADES (SHAllow-DEep-Shallow) transition as the SN size is decreased. This occurs because of the combined effect of quantum confinement and reduced dielectric constant in SN. Level splitting is pronounced and this can perhaps be probed by ESR and ENDOR techniques. Finally, we suggest that a perusal of literature on (semiconductor) cluster calculations carried out 30 years ago would be useful.

  17. Electrons in Nanostructures

    DEFF Research Database (Denmark)

    Flindt, Christian

    2007-01-01

    possibilities o®ered by the quantum mechanical behavior of electrons when it comes to informa- tion processing. This branch of research is also concerned with fundamental questions in physics. Besides an introduction to the above-mentioned subjects, the thesis con- tains a number of contributions to the ¯elds...... of coherent electron manip- ulation and the statistical description of electron transport through nano- devices. The physics of the electrons are described with a combination of numerical methods, developed and applied in the thesis, and more analytical approaches, which are also discussed. The...... quantum-based communication. The statistical description of electron transport through nanostructures is based on rate equations, and the primary contribution of the thesis in that respect is the development of a method that allows for the calculation of the distribution of electrons passing through a...

  18. Biogenic nanostructured silica

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Silicon is by far the most abundant element in the earth crust and also is an essential element for higher plants, yet its biology and mechanisms in plant tolerance of biotic and abiotic stresses are poorly understood. Based on the molecular mechanisms of the biosilicification in marine organisms such as diatoms and sponges, the cell wall template-mediated self-assembly of nanostructured silica in marine organisms and higher plants as well as the related organic molecules are discussed. Understanding of the templating and structure-directed effects of silicon-processing organic molecules not only offers the clue for synthesizing silicon-based materials, but also helps to recognize the anomaly of silicon in plant biology.

  19. METAL MELTS – NANOSTRUCTURED SYSTEMS

    Directory of Open Access Journals (Sweden)

    V. Yu. Stetsenko

    2015-05-01

    Full Text Available On the basis of thermodynamic analysis it is shown that metal melts are the nanostructured systems which consist of phases and atoms nanocrystals. Nanocrystalsmake 97% ofthemeltvolume.

  20. Nanostructured materials and their applications

    CERN Document Server

    Logothetidis, Stergios

    2012-01-01

    This book applies nanostructures and nanomaterials to energy and organic electronics, offering advanced deposition and processing methods and theoretical and experimental aspects for nanoparticles, nanotubes and thin films for organic electronics applications.

  1. Peptide nanostructures in biomedical technology.

    Science.gov (United States)

    Feyzizarnagh, Hamid; Yoon, Do-Young; Goltz, Mark; Kim, Dong-Shik

    2016-09-01

    Nanostructures of peptides have been investigated for biomedical applications due to their unique mechanical and electrical properties in addition to their excellent biocompatibility. Peptides may form fibrils, spheres and tubes in nanoscale depending on the formation conditions. These peptide nanostructures can be used in electrical, medical, dental, and environmental applications. Applications of these nanostructures include, but are not limited to, electronic devices, biosensing, medical imaging and diagnosis, drug delivery, tissue engineering and stem cell research. This review offers a discussion of basic synthesis methods, properties and application of these nanomaterials. The review concludes with recommendations and future directions for peptide nanostructures. WIREs Nanomed Nanobiotechnol 2016, 8:730-743. doi: 10.1002/wnan.1393 For further resources related to this article, please visit the WIREs website. PMID:26846352

  2. Anisotropic surface properties of micro/nanostructured a-C:H:F thin films with self-assembly applications

    OpenAIRE

    Freire Soler, Víctor Manuel; Corbella Roca, Carles; Bertrán Serra, Enric; Portal-Marco, S.; Rubio-Roy, M.; Andújar Bella, José Luis

    2012-01-01

    The singular properties of hydrogenated amorphous carbon (a-C:H) thin filmsdeposited by pulsed DC plasma enhanced chemical vapor deposition (PECVD), such as hardness and wear resistance, make it suitable as protective coating with low surface energy for self-assembly applications. In this paper, we designed fluorine-containing a-C:H (a-C:H:F) nanostructured surfaces and we characterized them for self-assembly applications. Sub-micron patterns were generated on silicon through laser lithograph...

  3. Multiphysics simulations of magnetic nanostructures

    OpenAIRE

    Franchin, Matteo

    2009-01-01

    Multiphysics simulations of magnetic nanostructures by Matteo Franchin In recent years the research on magnetism has seen a new trend emerging, characterised by considerable effort in developing new nanostructures and nding new ways to control and manipulate their magnetisation, such as using spin polarised currents or light pulses. The field of magnetism is thus moving towards the multiphysics direction, since it is increasingly studied in conjunction with other types of ph...

  4. Fabrication of nanowires and nanostructures

    DEFF Research Database (Denmark)

    Mátéfi-Tempfli, Stefan; Mátéfi-Tempfli, M.; Piraux, L.

    2009-01-01

    We report on different approaches that we have adopted and developed for the fabrication of nanowires and nanostructures. Methods based on template synthesis and on self organization seem to be the most promising for the fabrication of nanomaterials and nanostructures due to their easiness and low...... with microelectronic processes make it an ideal candidate for further integration into large-scale fabrication of various nanowire-based devices. © 2009 Springer-Verlag....

  5. Quantification of surface amorphous content using dispersive surface energy: the concept of effective amorphous surface area.

    Science.gov (United States)

    Brum, Jeffrey; Burnett, Daniel

    2011-09-01

    We investigate the use of dispersive surface energy in quantifying surface amorphous content, and the concept of effective amorphous surface area is introduced. An equation is introduced employing the linear combination of surface area normalized square root dispersive surface energy terms. This equation is effective in generating calibration curves when crystalline and amorphous references are used. Inverse gas chromatography is used to generate dispersive surface energy values. Two systems are investigated, and in both cases surface energy data collected for physical mixture samples comprised of amorphous and crystalline references fits the predicted response with good accuracy. Surface amorphous content of processed lactose samples is quantified using the calibration curve, and interpreted within the context of effective amorphous surface area. Data for bulk amorphous content is also utilized to generate a thorough picture of how disorder is distributed throughout the particle. An approach to quantifying surface amorphous content using dispersive surface energy is presented. Quantification is achieved by equating results to an effective amorphous surface area based on reference crystalline, and amorphous materials. PMID:21725707

  6. Structural relaxation in amorphous silicon carbide

    International Nuclear Information System (INIS)

    High purity single crystal and chemically vapor deposited (CVD) silicon carbide have been amorphized under fast neutron irradiation. The gradual transition in physical properties from the as-amorphized state to a more relaxed amorphous state prior to crystallization is studied. For the three bulk properties studied: density, electrical resistivity, and thermal conductivity, large property changes occur upon annealing between the amorphization temperature and the point of crystallization. These physical property changes occur in the absence of crystallization and are attributed to short and perhaps medium range ordering during annealing. It is demonstrated that the physical properties of amorphous SiC (a-SiC) can vary greatly and are likely a function of the irradiation state producing the amorphization. The initiation of crystallization as measured using bulk density and in situ TEM is found to be ∼875 deg. C, though the kinetics of crystallization above this point are seen to depend on the technique used. It is speculated that in situ TEM and other thin-film approaches to study crystallization of amorphous SiC are flawed due to thin-film effects

  7. Nanostructured thin ribbons of a shape memory TiNiCu alloy

    International Nuclear Information System (INIS)

    The present work deals with the investigation of the nanostructured shape memory alloys for the purpose of development of micromechanical devices. The Ti50Ni25Cu25 (at.%) alloy fabricated by the melt spinning technique in the form of a ribbon with a thickness around 40 μm and a width about 1.5 mm was chosen as a starting material. Technological parameters were optimized to produce the alloy in an amorphous state. The thickness of the ribbon was reduced to 5-10 μm by means of electrochemical polishing. A special nanostructurization of the thin ribbons was obtained via the dynamic crystallization of the amorphous alloy by application of a single electric pulse with duration near 500 μs. A composite micromanipulator with overall dimensions of 20 x 5 x 0.9 μm was developed and produced on the basis of the obtained nanostructured thin ribbons by means of the focused ion beam (FIB) technique.

  8. Simple Formation of Nanostructured Molybdenum Disulfide Thin Films by Electrodeposition

    Directory of Open Access Journals (Sweden)

    S. K. Ghosh

    2013-01-01

    Full Text Available Nanostructured molybdenum disulfide thin films were deposited on various substrates by direct current (DC electrolysis form aqueous electrolyte containing molybdate and sulfide ions. Post deposition annealing at higher temperatures in the range 450–700°C transformed the as-deposited amorphous films to nanocrystalline structure. High temperature X-ray diffraction studies clearly recorded the crystal structure transformations associated with grain growth with increase in annealing temperature. Surface morphology investigations revealed featureless structure in case of as-deposited surface; upon annealing it converts into a surface with protruding nanotubes, nanorods, or dumbbell shape nanofeatures. UV-visible and FTIR spectra confirmed about the presence of Mo-S bonding in the deposited films. Transmission electron microscopic examination showed that the annealed MoS2 films consist of nanoballs, nanoribbons, and multiple wall nanotubes.

  9. Thermal and Thermoelectric Transport in Thin Films and Nanostructures

    Science.gov (United States)

    Zink, B. L.; Sultan, R.; Avery, A. D.

    2009-03-01

    Interest in increasing efficiency of energy generation continues to spur the development of new thermoelectric materials. Though bulk materials hold the most promise for large-scale energy generation, many groups continue to explore increasing the thermoelectric figure-of-merit by taking advantage of techniques for creating nanostructured materials such as multilayered thin films and nanowires. These systems could prove to have high figures-of-merit and be important for integrating energy harvesting and/or cooling with micro- or nanoscale devices ``on chip.'' Though many promising systems have been identified, measuring their fundamental thermal transport often remains a major challenge. In this talk, we briefly describe our recent advances in measuring in-plane thermal transport, thermopower and electrical conductivity on thin-films or nanolithographically patterned systems. Our technique allows great flexibility for studying the thermoelectric properties of a wide range of materials, from amorphous semiconductors to semi-metallic nanowires.

  10. CVD of refractory amorphous metal alloys

    International Nuclear Information System (INIS)

    In this work, a novel process is described for the fabrication of multi-metallic amorphous metal alloy coatings using a chemical vapor deposition (CVD) technique. Of special interest in this work are amorphous metal alloys containing Mo and/or Cr which have high crystallization temperatures and readily available low decomposition temperature metal-bearing precursors. The conditions for amorphous alloy formation via CVD are described as well as the chemical properties of these materials. High temperature, aqueous corrosion tests have shown these materials (especially those containing Cr) are among the most corrosion resistant metal alloys known

  11. Photonic crystals, amorphous materials, and quasicrystals

    International Nuclear Information System (INIS)

    Photonic crystals consist of artificial periodic structures of dielectrics, which have attracted much attention because of their wide range of potential applications in the field of optics. We may also fabricate artificial amorphous or quasicrystalline structures of dielectrics, i.e. photonic amorphous materials or photonic quasicrystals. So far, both theoretical and experimental studies have been conducted to reveal the characteristic features of their optical properties, as compared with those of conventional photonic crystals. In this article, we review these studies and discuss various aspects of photonic amorphous materials and photonic quasicrystals, including photonic band gap formation, light propagation properties, and characteristic photonic states. (focus issue)

  12. Structural relaxation of amorphous silicon carbide

    International Nuclear Information System (INIS)

    We have examined amorphous structures of silicon carbide (SiC) using both transmission electron microscopy and a molecular-dynamics approach. Radial distribution functions revealed that amorphous SiC contains not only heteronuclear (Si-C) bonds but also homonuclear (Si-Si and C-C) bonds. The ratio of heteronuclear to homonuclear bonds was found to change upon annealing, suggesting that structural relaxation of the amorphous SiC occurred. Good agreement was obtained between the simulated and experimentally measured radial distribution functions

  13. Structural relaxation of amorphous silicon carbide.

    Science.gov (United States)

    Ishimaru, Manabu; Bae, In-Tae; Hirotsu, Yoshihiko; Matsumura, Syo; Sickafus, Kurt E

    2002-07-29

    We have examined amorphous structures of silicon carbide (SiC) using both transmission electron microscopy and a molecular-dynamics approach. Radial distribution functions revealed that amorphous SiC contains not only heteronuclear (Si-C) bonds but also homonuclear (Si-Si and C-C) bonds. The ratio of heteronuclear to homonuclear bonds was found to change upon annealing, suggesting that structural relaxation of the amorphous SiC occurred. Good agreement was obtained between the simulated and experimentally measured radial distribution functions. PMID:12144449

  14. Electrochromic Properties of Li+-Intercalated Amorphous Tungsten (aWO(3-x)) and Titanium (aTiO(2-x)) Oxide Thin Films

    OpenAIRE

    Triana, Carlos A.; Granqvist, Claes-Göran; Niklasson, Gunnar

    2014-01-01

    We report on electrochromic properties of stoichiometric and oxygen-deficient amorphous films, denoted aWO(3-x) and aTiO(2-x), under Li+-ion-electron inter/deintercalation. Optical characterization of the films in their as-deposited, fully intercalated (dark), and bleached states were performed by in-situ optical transmittance measurements. We explore electrochromism and optical absorption phenomena in the context of oxygen deficiency and nanostructure. Studies by cyclic voltammetry suggest g...

  15. Nanostructured polymer stable glasses via matrix assisted pulsed laser evaporation

    Science.gov (United States)

    Shepard, Kimberly B.

    Amorphous materials, or glasses, which lack a crystalline structure, are technologically ubiquitous with applications including structural components, pharmaceuticals, and electronic devices. Glasses are traditionally formed by rapid cooling from the melt state, where molecules become kinetically trapped into a non-equilibrium configuration. The temperature at which the material transforms from supercooled liquid to glass is the glass transition temperature. The glass transition temperature is the most important property of amorphous materials, as it determines the range of temperatures where they are fabricated, used and stored. Recent technological developments in which glasses are formed by alternative routes, such as physical vapor deposition and matrix assisted pulsed laser evaporation (MAPLE), enable tunability of Tg and related physical properties. High-Tg glasses formed by these techniques are termed "stable glasses" and exhibit a wide range of exceptional properties. This work focuses on the formation and characterization of stable polymer glasses fabricated via MAPLE. Bulk films (>1 microm thick) of glassy polymers fabricated by MAPLE at slow growth rates (polymer glasses. Building on molecular dynamics simulations from the literature on the MAPLE process, we experimentally study the origin of nanostructure in our MAPLE-deposited films. We measure the time-of-flight of MAPLE-deposited material, confirming that the velocity is sufficiently low for intact deposition of polymer nanoglobules. The size distribution of polymer nanoglobules fabricated in short MAPLE depositions provides insight into how nanostructured MAPLE films form. Using our atomic force microscopy-based nanoscale dilatometry technique, we directly probe the nanoscale thermal behavior of individual polymer nanoglobules. We confirm that bulk and nanoscale glasses share many of the same physical behavior: enhanced stability above the glass transition temperature, and ~40% excess volume. We

  16. Low-temperature graphitization of amorphous carbon nanospheres

    Institute of Scientific and Technical Information of China (English)

    Katia Barbera; Leone Frusteri; Giuseppe Italiano; Lorenzo Spadaro; Francesco Frusteri; Siglinda Perathoner; Gabriele Centi

    2014-01-01

    The investigation by SEM/TEM, porosity, and X-ray diffraction measurements of the graphitization process starting from amorphous carbon nanospheres, prepared by glucose carbonization, is re-ported. Aspects studied are the annealing temperature in the 750-1000 °C range, the type of inert carrier gas, and time of treatment in the 2-6 h range. It is investigated how these parameters influ-ence the structural and morphological characteristics of the carbon materials obtained as well as their nanostructure. It is shown that it is possible to maintain after graphitization the round-shaped macro morphology, a high surface area and porosity, and especially a large structural disorder in the graphitic layers stacking, with the presence of rather small ordered domains. These are charac-teristics interesting for various catalytic applications. The key in obtaining these characteristics is the thermal treatment in a flow of N2. It was demonstrated that the use of He rather than N2 does not allow obtaining the same results. The effect is attributed to the presence of traces of oxygen, enough to create the presence of oxygen functional groups on the surface temperatures higher than 750 °C, when graphitization occurs. These oxygen functional groups favor the graphitization pro-cess.

  17. Mechanically Strain-Induced Modification of Selenium Powders in the Amorphization Process

    International Nuclear Information System (INIS)

    For the fabrication of particles designed in the nanoscale structure, or the nanostructural modification of particles using mechanical grinding process, selenium powders ground by a planetary ball mill at various rotational speeds have been investigated. Structural analyses, such as particle size distributions, crystallite sizes, lattice strains and nearest neighbour distances were performed using X-ray diffraction, scanning electron microscopy and dynamical light scattering.By grinding powder particles became spherical composites consisting of nanocrystalline and amorphous phase, and had a distribution with the average size of 2.7 μm. Integral intensities of diffraction peaks of annealed crystal selenium decreased with increasing grinding time, and these peaks broadened due to lattice strains and reducing crystallite size during the grinding. The ground powder at 200 rpm did not have the lattice strain and showed amorphization for the present grinding periods. It indicates that the amorphization of Se by grinding accompanies the lattice strain, and the lattice strain arises from a larger energy concerning intermolecular interaction. In this process, the impact energy is spent on thermal and structural changes according to energy accumulation in macroscopic (the particle size distribution) and microscopic (the crystallite size and the lattice strain) range

  18. Structure and Optical Properties of Silicon Nanocrystals Embedded in Amorphous Silicon Thin Films Obtained by PECVD

    Directory of Open Access Journals (Sweden)

    B. M. Monroy

    2011-01-01

    Full Text Available Silicon nanocrystals embedded in amorphous silicon matrix were obtained by plasma enhanced chemical vapor deposition using dichlorosilane as silicon precursor. The RF power and dichlorosilane to hydrogen flow rate ratio were varied to obtain different crystalline fractions and average sizes of silicon nanocrystals. High-resolution transmission electron microscopy images and RAMAN measurements confirmed the existence of nanocrystals embedded in the amorphous matrix with average sizes between 2 and 6 nm. Different crystalline fractions (from 12% to 54% can be achieved in these films by regulating the selected growth parameters. The global optical constants of the films were obtained by UV-visible transmittance measurements. Effective band gap variations from 1.78 to 2.3 eV were confirmed by Tauc plot method. Absorption coefficients higher than standard amorphous silicon were obtained in these thin films for specific growth parameters. The relationship between the optical properties is discussed in terms of the different internal nanostructures of the samples.

  19. Production and characterization of nanostructured silicon carbide

    Science.gov (United States)

    Wallis, Kendra Lee

    Nanostructured materials continue to attract attention because of their new and interesting properties, which are very different from their macrostructured equivalents. Since the size of grain and surface differs, a better understanding of the microstructure, the mechanism of formation, and methods of controlling surface properties is necessary. In this study, nanostructured silicon carbide has been produced from the solid-solid reaction of a mixture of silicon nanopowder and carbon multiwalled nanotubes (MWNT) sintered by induction. A study of the reaction rate at different temperatures has yielded a value for the activation energy of 254 +/- 36 kJ/mol, and has led to the conclusion that the reaction is diffusion-controlled. A second method produced pure silicon carbide nanowires using a procedure which kept the solid reactants, silicon powder and MWNT, separated while sintering at a constant temperature of 1200°C. Silicon in the vapor-phase reacted at the surface of the MWNTs followed by diffusion of both precursors through the product phase boundary. The reaction time was varied, and a morphological study has been done describing changes in shape and size as a function of time. The initial reaction produced a layer of SiC providing the outer shell of coaxial structures with carbon nanotubes inside. As Si and C diffused through the product phase to react at the interface, the tube became filled with SiC to form solid SiC nanowires, and the outer diameter of the nanowires grew continuously as reaction time increased. After long sintering times, growth continued in two dimensions, fusing nanowires together into planar structures. In addition, the precursor form of carbon was varied, and nanowires produced by two different types of nanotubes have been studied. The produced SiC nanowires show cubic crystal structure. After a few hours of sintering, stacking faults began to occur inside the wires, and the frequency of occurrence of the stacking faults increased as

  20. Surface Acidity of Amorphous Aluminum Hydroxide

    Institute of Scientific and Technical Information of China (English)

    K. FUKUSHI; K. TSUKIMURA; H. YAMADA

    2006-01-01

    The surface acidity of synthetic amorphous Al hydroxide was determined by acid/base titration with several complementary methods including solution analyses of the reacted solutions and XRD characterization of the reacted solids. The synthetic specimen was characterized to be the amorphous material showing four broad peaks in XRD pattern. XRD analyses of reacted solids after the titration experiments showed that amorphous Al hydroxide rapidly transformed to crystalline bayerite at the alkaline condition (pH>10). The solution analyses after and during the titration experiments showed that the solubility of amorphous aluminum hydroxide, Ksp =aAl3+/a3H+,was 1010.3,The amount of consumption of added acid or base during the titration experiment was attributed to both the protonation/deprotonation of dissolved Al species and surface hydroxyl group. The surface acidity constants, surface hydroxyl density and specific surface area were estimated by FITEQL 4.0.

  1. LOCAL ATOMIC STRUCTURE OF AMORPHOUS METALS

    OpenAIRE

    Egami, T.; Maed, K.; Srolovitz, D.; Vitek, V.

    1980-01-01

    The local parameters are introduced to describe the local atomic structure of amorphous metals. They define the structural defects which facilitate the explanation of various properties, including the volume change by annealing.

  2. Diode Based on Amorphous SiC

    Directory of Open Access Journals (Sweden)

    V.S. Zakhvalinskii

    2013-12-01

    Full Text Available Diode structure on the basis of amorphous silicon carbide and p-type polycrystalline silicon (Eurosolar were obtained with magnetron RF-nonreactive sputtering method from solid-phase target in argon atmosphere.

  3. Diode Based on Amorphous SiC

    OpenAIRE

    V.S. Zakhvalinskii; L.V. Borisenko; A.J. Aleynikov; E.A. Piljuk; I. Goncharov; S.V. Taran

    2013-01-01

    Diode structure on the basis of amorphous silicon carbide and p-type polycrystalline silicon (Eurosolar) were obtained with magnetron RF-nonreactive sputtering method from solid-phase target in argon atmosphere.

  4. Bulk amorphous Mg-based alloys

    DEFF Research Database (Denmark)

    Pryds, Nini

    The present paper describes the preparation and properties of bulk amorphous quarternary Mg-based alloys and the influence of additional elements on the ability of the alloy to form bulk amorphous. The main goal is to find a Mg-based alloy system which shows both high strength to weight ratio and a...... low glass transition temperature. The alloys were prepared by using a relatively simple technique, i.e. rapid cooling of the melt in a copper wedge mould. The essential structural changes that are achieved by going from the amorphous to the crystalline state through the supercooled liquid state are...... discussed in this paper. On the basis of these measurements phase diagrams of the different systems were constructed. Finally, it is demonstrated that when pressing the bulk amorphous alloy onto a metallic dies at temperatures within the supercooled liquid region, the alloy faithfully replicates the surface...

  5. Fabrication and characterization of one dimensional zinc oxide nanostructures

    Science.gov (United States)

    Cheng, Chun

    role for the GL emission. On the other hand, those ZnO tapered structures fabricated by a modified carbon thermal method with the assistance of Au catalysts display strong UV emission, indicating a good crystallization quality. The stability, structural degradation and related PL property of ZnO NWs under different environments of surface treatments have been investigated by high-resolution transmission electron microscopy (HRTEM) and near field optical microscopy (NSOM). For high-quality ZnO NWs, the UV emission shows no change and no DL emission was generated during the structural degradation. For those ZnO NWs showing GL emission, the commonly used treatment methods e.g., post-annealing can not effectively eliminate the GL emission. The chemical stability and biocompatibility of ZnO nanostructures in simulated physiological solution (SPS) are studied by electron diffraction and HRTEM. ZnO nanostructures fabricated by the thermal evaporation method were found to survive much longer in SPS than those fabricated using a hydrothermal solution method. Calcium hydrogen phosphate amorphous layers structures have been observed to have excellent interfacial contacts with ZnO NWs. The shapes of the voids formed in the ZnO NWs are due to the interesting anisotropic etching behaviors in SPS which can be used to identify the polar directions of ZnO nanocrystals. Using hydrothermal reaction, TiO2/ZnO (TZO) nanohybrid structures have been found to form through the site-specific deposition of TiO2 on ZnO nanorods (NRs). TEM studies have revealed each ZnO NR to be assembled with one TiO2 cap at the Zn terminated (0001) surface. The polarity of the ZnO (0001) surface plays an important role in the formation of the TZO nanohybrid structures. The TZO nanohybrids contain uniform and atomically flat interfaces between ZnO and TiO2 with tunable crystal phases, which can be amorphous, anatase and rutile through annealing treatments. These nanohybrid structures demonstrate an enhanced

  6. Amorphous carbon and its surfaces

    International Nuclear Information System (INIS)

    Graphical abstract: Some examples of 2.0 g/cm3 surfaces. The cell contained 64 atoms. The top figure shows some tube-like formation, the central figure is an example of a wave-like surface, and the bottom figure is an example of the bending over of the carbons at the surface to form a surface sheet when the sheets in the bulk are not parallel to the surface. - Abstract: We have investigated bulk amorphous carbon at three densities (3.2, 2.6, and 2.0 g/cm3) using density functional theory (DFT). The variation in the structure with density is discussed. The bulk structures are used to create surface structures. If the surfaces are relaxed at 700 K, the surface structures, as a function of density, are more similar than the analogous bulk structures. The relaxed surfaces appear to be graphene sheets with defects, sizable distortions, and have covalently bonded carbon chains holding the sheets together.

  7. Structure of Amorphous Titania Nanoparticles

    Science.gov (United States)

    Zhang, H.; Chen, B.; Banfield, J. F.; Waychunas, G. A.

    2008-12-01

    Ultrafine (2 - 3 nm) titania (TiO2) nanoparticles show only diffuse scattering by both conventional powder x-ray diffraction and electron diffraction. We used synchrotron wide-angle x-ray scattering (WAXS) to probe the atomic correlations in this amorphous material. The atomic pair-distribution function (PDF) derived from Fourier transform of the WAXS data was used for reverse Monte Carlo (RMC) simulations of the atomic structure of the small nanoparticles. Molecular dynamics simulations were used to generate input structures for the RMC. X-ray absorption spectroscopy (XAS) simulations were used to screen candidate structures obtained from the RMC. The structure model that best describes both the WAXS and XAS data consists of particles with a highly distorted shell and a small strained anatase-like crystalline core. The average coordination number of Ti is 5.3 and the Ti-O bond length peaks at 1.940 Å. Relative to bulk titania, the reduction of the coordination number is primarily due to the truncation of the Ti-O octahedra at the titania nanoparticle surface, and the shortening of the Ti-O bond length is due to bond contraction in the distorted shell. Core-shell structures in ultrafine nanoparticles may be common in many materials (e.g. ZnS).

  8. Laser annealing of hydrogen implanted amorphous silicon

    International Nuclear Information System (INIS)

    Amorphous silicon, prepared by silicon bombardment at energies of 200 to 250 keV, was implanted with 40 keV H2+ to peak concentrations up to 15 at .% and recrystallized in air by single 20 nsec pulses at 1.06 μm from a Nd:glass laser. Amorphous layer formation and recrystallization were verified using Raman spectroscopy and ion backscattering/channeling analysis

  9. A Magnetic Sensor with Amorphous Wire

    Directory of Open Access Journals (Sweden)

    Dongfeng He

    2014-06-01

    Full Text Available Using a FeCoSiB amorphous wire and a coil wrapped around it, we have developed a sensitive magnetic sensor. When a 5 mm long amorphous wire with the diameter of 0.1 mm was used, the magnetic field noise spectrum of the sensor was about 30 pT/ÖHz above 30 Hz. To show the sensitivity and the spatial resolution, the magnetic field of a thousand Japanese yen was scanned with the magnetic sensor.

  10. Tests Of Amorphous-Silicon Photovoltaic Modules

    Science.gov (United States)

    Ross, Ronald G., Jr.

    1988-01-01

    Progress in identification of strengths and weaknesses of amorphous-silicon technology detailed. Report describes achievements in testing reliability of solar-power modules made of amorphous-silicon photovoltaic cells. Based on investigation of modules made by U.S. manufacturers. Modules subjected to field tests, to accelerated-aging tests in laboratory, and to standard sequence of qualification tests developed for modules of crystalline-silicon cells.

  11. DEFECTS IN AMORPHOUS CHALCOGENIDES AND SILICON

    OpenAIRE

    Adler, D.

    1981-01-01

    Our comprehension of the physical properties of amorphous semiconductors has improved considerably over the past few years, but many puzzles remain. From our present perspective, the major features of chalcogenide glasses appear to be well understood, and some of the fine points which have arisen recently have been explained within the same general model. On the other hand, there are a grear number of unresolved mysteries with regard to amorphous silicon-based alloys. In this paper, the valen...

  12. Amorphous Silicon Carbide for Photovoltaic Applications

    OpenAIRE

    JANZ, Stefan

    2006-01-01

    Within this work amorphous SiC is investigated for its applicability in photovoltaic devices. The temperature stability and dopability of SiC makes this material very attractive for applications in this area. Physical basics of amorphous SiC networks and plasma processes are discussed and first measurements with FTIR of the different layer types show the complexity of the network. The special features of the plasma reactor such as high temperature deposition and two-source excitation are also...

  13. Amorphous Carbon-Boron Nitride Nanotube Hybrids

    Science.gov (United States)

    Kim, Jae Woo (Inventor); Siochi, Emilie J. (Inventor); Wise, Kristopher E. (Inventor); Lin, Yi (Inventor); Connell, John (Inventor)

    2016-01-01

    A method for joining or repairing boron nitride nanotubes (BNNTs). In joining BNNTs, the nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation to form well bonded hybrid a-C/BNNT structures. In repairing BNNTs, the damaged site of the nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation to form well bonded hybrid a-C/BNNT structures at the damage site.

  14. Optics of anisotropic nanostructures

    Science.gov (United States)

    Rokushima, Katsu; Antoš, Roman; Mistrík, Jan; Višňovský, Štefan; Yamaguchi, Tomuo

    2006-07-01

    The analytical formalism of Rokushima and Yamakita [J. Opt. Soc. Am. 73, 901-908 (1983)] treating the Fraunhofer diffraction in planar multilayered anisotropic gratings proved to be a useful introduction to new fundamental and practical situations encountered in laterally structured periodic (both isotropic and anisotropic) multilayer media. These are employed in the spectroscopic ellipsometry for modeling surface roughness and in-depth profiles, as well as in the design of various frequency-selective elements including photonic crystals. The subject forms the basis for the solution of inverse problems in scatterometry of periodic nanostructures including magnetic and magneto-optic recording media. It has no principal limitations as for the frequencies and period to radiation wavelength ratios and may include matter wave diffraction. The aim of the paper is to make this formalism easily accessible to a broader community of students and non-specialists. Many aspects of traditional electromagnetic optics are covered as special cases from a modern and more general point of view, e.g., plane wave propagation in isotropic media, reflection and refraction at interfaces, Fabry-Perot resonator, optics of thin films and multilayers, slab dielectric waveguides, crystal optics, acousto-, electro-, and magneto-optics, diffraction gratings, etc. The formalism is illustrated on a model simulating the diffraction on a ferromagnetic wire grating.

  15. Phonon engineering for nanostructures.

    Energy Technology Data Exchange (ETDEWEB)

    Aubry, Sylvie (Stanford University); Friedmann, Thomas Aquinas; Sullivan, John Patrick; Peebles, Diane Elaine; Hurley, David H. (Idaho National Laboratory); Shinde, Subhash L.; Piekos, Edward Stanley; Emerson, John Allen

    2010-01-01

    Understanding the physics of phonon transport at small length scales is increasingly important for basic research in nanoelectronics, optoelectronics, nanomechanics, and thermoelectrics. We conducted several studies to develop an understanding of phonon behavior in very small structures. This report describes the modeling, experimental, and fabrication activities used to explore phonon transport across and along material interfaces and through nanopatterned structures. Toward the understanding of phonon transport across interfaces, we computed the Kapitza conductance for {Sigma}29(001) and {Sigma}3(111) interfaces in silicon, fabricated the interfaces in single-crystal silicon substrates, and used picosecond laser pulses to image the thermal waves crossing the interfaces. Toward the understanding of phonon transport along interfaces, we designed and fabricated a unique differential test structure that can measure the proportion of specular to diffuse thermal phonon scattering from silicon surfaces. Phonon-scale simulation of the test ligaments, as well as continuum scale modeling of the complete experiment, confirmed its sensitivity to surface scattering. To further our understanding of phonon transport through nanostructures, we fabricated microscale-patterned structures in diamond thin films.

  16. Fabrication and characterization of carbon and boron carbide nanostructured materials

    Science.gov (United States)

    Reynaud, Sara

    Carbon is present in nature in a variety of allotropes and chemical compounds. Due to reduced dimensionality, nanostructured carbon materials, i.e. single walled carbon nanotubes (SWNTs), are characterized by unique physical and chemical properties. There is a potential for SWNTs use as biological probes and assists for tunable tissue growth in biomedical applications. However, the presumed cytotoxicity of SWNTs requires investigation of the risks of their incorporation into living systems. Boron is not found in nature in elementary form. Boron based materials are chemically complex and exist in various polymorphic forms, i.e. boron carbide (BC). Because BC is a lightweight material with exceptional mechanical and elastic properties, it is the ideal candidate for armor and ballistic applications. However, practical use of BC as armor material is limited because of its anomalous glass-like behaviour at high velocity impacts, which has been linked to stress-induced structural instability in one of BC polymorphs, B12(CCC). Theoretical calculations suggest that formation of B12(CCC) in BC could be suppressed by silicon doping. In the first part of this thesis, biocompatibility of SWNTs is investigated. It is shown that under normal cell implantation conditions, the electrical conductivity of the SWNTs decreases due to an increase in structural disorder. This research suggests that SWNTs can be functionalized by protein and biological cells reducing the risk of cytotoxicity. In the second part of this thesis, boron carbide nanostructured materials are synthesized and investigated. Radio frequency sputtering deposition technique is employed for fabrication of BC (Si free) and BC:Si thin films. Variation of plasma conditions and temperature are found to affect chemical composition, adhesion to the substrate and morphology of the films. It is shown that BC films are predominantly amorphous and a small addition of Si largely improves their mechanical properties. In addition

  17. Amorphous boron nitride at high pressure

    Science.gov (United States)

    Durandurdu, Murat

    2016-06-01

    The pressure-induced phase transformation in hexagonal boron nitrite and amorphous boron nitrite is studied using ab initio molecular dynamics simulations. The hexagonal-to-wurtzite phase transformation is successfully reproduced in the simulation with a transformation mechanism similar to one suggested in experiment. Amorphous boron nitrite, on the other hand, gradually transforms to a high-density amorphous phase with the application of pressure. This phase transformation is irreversible because a densified amorphous state having both sp3 and sp2 bonds is recovered upon pressure release. The high-density amorphous state mainly consists of sp3 bonds and its local structure is quite similar to recently proposed intermediate boron nitrite phases, in particular tetragonal structure (P42/mnm), rather than the known the wurtzite or cubic boron nitrite due to the existence of four membered rings and edge sharing connectivity. On the basis of this finding we propose that amorphous boron nitrite might be best candidate as a starting structure to synthesize the intermediate phase(s) at high pressure and temperature (probably below 800 °C) conditions.

  18. Challenges in amorphous silicon solar cell technology

    International Nuclear Information System (INIS)

    Hydrogenated amorphous silicon is nowadays extensively used for a range of devices, amongst others solar cells. Solar cell technology has matured over the last two decades and resulted in conversion efficiencies in excess of 15%. In this paper the operation of amorphous silicon solar cells is briefly described. For tandem solar cell, amorphous silicon germanium is often used as material for the intrinsic layer of the bottom cell. This improves the red response of the cell. In order to optimize the performance of amorphous silicon germanium solar cells, profiling of the germanium concentration near the interfaces is applied. We show in this paper that the performance is strongly dependent on the width of the grading near the interfaces. The best performance is achieved when using a grading width that is as small as possible near the p-i interface and as wide as possible near the i-n interface. High-rate deposition of amorphous silicon is nowadays one of the main issues. Using the Expanding Thermal Plasma deposition method very high deposition rates can be achieved. This method has been applied for the fabrication of an amorphous silicon solar cell with a conversion efficiency of 5,8%. (authors)

  19. Can amorphization take place in nanoscale interconnects?

    International Nuclear Information System (INIS)

    The trend of miniaturization has highlighted the problems of heat dissipation and electromigration in nanoelectronic device interconnects, but not amorphization. While amorphization is known to be a high pressure and/or temperature phenomenon, we argue that defect density is the key factor, while temperature and pressure are only the means. For nanoscale interconnects carrying modest current density, large vacancy concentrations may be generated without the necessity of high temperature or pressure due to the large fraction of grain boundaries and triple points. To investigate this hypothesis, we performed in situ transmission electron microscope (TEM) experiments on 200 nm thick (80 nm average grain size) aluminum specimens. Electron diffraction patterns indicate partial amorphization at modest current density of about 105 A cm−2, which is too low to trigger electromigration. Since amorphization results in drastic decrease in mechanical ductility as well as electrical and thermal conductivity, further increase in current density to about 7 × 105 A cm−2 resulted in brittle fracture failure. Our molecular dynamics (MD) simulations predict the formation of amorphous regions in response to large mechanical stresses (due to nanoscale grain size) and excess vacancies at the cathode side of the thin films. The findings of this study suggest that amorphization can precede electromigration and thereby play a vital role in the reliability of micro/nanoelectronic devices. (paper)

  20. Irradiation Induced Microstructure Evolution in Nanostructured Materials: A Review

    Directory of Open Access Journals (Sweden)

    Wenbo Liu

    2016-02-01

    Full Text Available Nanostructured (NS materials may have different irradiation resistance from their coarse-grained (CG counterparts. In this review, we focus on the effect of grain boundaries (GBs/interfaces on irradiation induced microstructure evolution and the irradiation tolerance of NS materials under irradiation. The features of void denuded zones (VDZs and the unusual behavior of void formation near GBs/interfaces in metals due to the interactions between GBs/interfaces and irradiation-produced point defects are systematically reviewed. Some experimental results and calculation results show that NS materials have enhanced irradiation resistance, due to their extremely small grain sizes and large volume fractions of GBs/interfaces, which could absorb and annihilate the mobile defects produced during irradiation. However, there is also literature reporting reduced irradiation resistance or even amorphization of NS materials at a lower irradiation dose compared with their bulk counterparts, since the GBs are also characterized by excess energy (compared to that of single crystal materials which could provide a shift in the total free energy that will lead to the amorphization process. The competition of these two effects leads to the different irradiation tolerance of NS materials. The irradiation-induced grain growth is dominated by irradiation temperature, dose, ion flux, character of GBs/interface and nanoprecipitates, although the decrease of grain sizes under irradiation is also observed in some experiments.

  1. The effects of amorphous Al2O3 underlayer on the microstructure and magnetic properties of BaFe12O19 thin films

    International Nuclear Information System (INIS)

    Single phase nanostructured BaFe12O19 thin films have been deposited on Si(110) substrate and Si(110) substrate with amorphous Al2O3 underlayer by a sol–gel method. The effects of the amorphous Al2O3 underlayer on the composition, microstructure and magnetic properties were explored by X-ray diffraction, scanning electron microscopy and vibrating sample magnetometery techniques. The results revealed that the amorphous Al2O3 underlayer promoted some perpendicular c-axis orientation with ΔHc=Hcperpendicular−Hc∥=300 Oe. - Highlights: • The BaFe12O19 film fabricated by the Pechini method, deposited on Si(110), Si(110)/Al2O3 substrates. • The Al2O3 underlayer induced some c-axis perpendicular orientation. • Out-of-plane magnetic properties of the film with underlayer are better than those of in-plane orientation

  2. Key Physical Mechanisms in Nanostructured Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Dr Stephan Bremner

    2010-07-21

    The objective of the project was to study both theoretically and experimentally the excitation, recombination and transport properties required for nanostructured solar cells to deliver energy conversion efficiencies well in excess of conventional limits. These objectives were met by concentrating on three key areas, namely, investigation of physical mechanisms present in nanostructured solar cells, characterization of loss mechanisms in nanostructured solar cells and determining the properties required of nanostructured solar cells in order to achieve high efficiency and the design implications.

  3. Nonequilibrium phenomena in adjacent electrically isolated nanostructures

    OpenAIRE

    Khrapai, V. S.; Ludwig, S.; Kotthaus, J. P.; Tranitz, H. P.; Wegscheider, W.

    2008-01-01

    We report on nonequilibrium interaction phenomena between adjacent but electrostatically separated nanostructures in GaAs. A current flowing in one externally biased nanostructure causes an excitation of electrons in a circuit of a second nanostructure. As a result we observe a dc current generated in the unbiased second nanostructure. The results can be qualitatively explained in terms of acoustic phonon based energy transfer between the two mutually isolated circuits.

  4. Thermal Conductivity Suppression in Nanostructured Silicon and Germanium Nanowires

    Science.gov (United States)

    Özden, Ayberk; Kandemir, Ali; Ay, Feridun; Perkgöz, Nihan Kosku; Sevik, Cem

    2016-03-01

    The inherent low lattice thermal conductivity (TC) of semiconductor nanowires (s-NW) due to one-dimensional phonon confinement might provide a solution for the long-lasting figure-of-merit problem for highly efficient thermoelectric (TE) applications. Standalone diameter modulation or alloying of s-NW serve as a toolkit for TC control, but realizing the full potential of nanowires requires new atomic-scale designs, growth, characterization, and understanding of the physical mechanisms behind the structure-property (TC) relationship. Before undertaking time-consuming and expensive experimental work, molecular dynamics (MD) simulations serve as an excellent probe to investigate new designs and understand how nanostructures affect thermal transport properties through their capability to capture various phenomena such as phonon boundary scattering, phonon coherence resonance, and phonon backscattering. On the other hand, because different research groups use different structural and MD parameters in their simulations, it is rather difficult to make comparisons between different nanostructures and select appropriate ones for potential TE applications. Therefore, in this work, we systematically investigated pristine, core-shell (C-S), holey (H-N), superlattice (SL), sawtooth (ST), and superlattice sawtooth (SL-ST) nanowires with identical structural parameters. Specifically, we aim to compare the relative TC reduction achieved by these nanostructures with respect to pristine nanowires in order to propose the best structural design with the lowest lattice TC, using Green-Kubo method-based equilibrium molecular dynamics simulations at 300 K. Our results show that the TC can be minimized by changing specific parameters such as the core diameter and monolayer separation for C-S, H-N, and ST structures. In the case of SL structures, the TC is found to be independent of these parameters. However, surface roughness in the form of a ST morphology provides a TC value below 2 W

  5. Structure and magnetic properties of nanostructural strontium ferrite prepared by mechanochemical treatment

    International Nuclear Information System (INIS)

    Full text: It was recently-established for hexagonal barium ferrite-industrially important magnetically hard material that refinement of the crystallite dimensions into the nanoscale regime, typically ≤ 10 nm, leads after heat treatment at temperatures 800-1000 deg C to significant coercivity increase of up to 6.5 kOe (∼3-4 times) with saturation magnetisation values of 50-55 emu/g (∼95% of bulk at room temperature). High-energy mechanochemical processing has been applied to prepare nanostructural (nanocrystalline-amorphous) composites. High resolution electron microscopy studies reveal that the enhancement of the final magnetic properties was due to formation of magnetically noninteracting ∼l,μm Ba-ferrite particles with 5-10 nm amorphous surface layer - depending on annealing parameters. Similar situation was established also for ball milled strontium ferrite (SrFe12O19) powders where short annealing 4 h at 1000 deg C produced increased Hc value of up to ∼5 kOe compared to typical ∼3.6 kOe for anisotropic ceramic material. In this presentation we concentrate on microstructural features to be able to understand significant enlargement of coercivity values for such powders. The evolution of phases and magnetic properties in nanostructural powder obtained by prolonged ball milling of SrFe12O19 ferrite in vacuum and air atmosphere will be presented. We will address the following changes in strontium ferrite induced by mechanochemical processing: 1) generation of amorphous (disordered) and nanocrystalline phases, 2) polymorphic transformations due to solid-gas reactions at the surface and 3) alternations in magnetic properties due to nanostructure development

  6. Electron Microscopy of Nanostructures in Cells

    DEFF Research Database (Denmark)

    Købler, Carsten

    Nanostructures are small objects with a huge potential. They can be engineered in an endless number of different shapes and sizes and have almost as many future uses. Nanostructures have recently garnered an increasing interest from the life-sciences as nanostructures have the potential to be used...

  7. Simple Approach to Superamphiphobic Overhanging Silicon Nanostructures

    DEFF Research Database (Denmark)

    Kumar, Rajendra; Mogensen, Klaus Bo; Bøggild, Peter

    2010-01-01

    Superhydrophobic silicon nanostructures were fabricated by anisotropic etching of silicon coated with a thin hydrophobic layer. At certain etch parameters, overhanging nanostructures form at the apexes of the rod-shaped tips, This leads to superoleophobic behavior for several oily liquids with......, nonlithographic method for introducing amphiphobic behavior on a Surface consisting of vertically aligned micro- or nanostructures....

  8. Method of fabrication of anchored nanostructure materials

    Science.gov (United States)

    Seals, Roland D; Menchhofer, Paul A; Howe, Jane Y; Wang, Wei

    2013-11-26

    Methods for fabricating anchored nanostructure materials are described. The methods include heating a nano-catalyst under a protective atmosphere to a temperature ranging from about 450.degree. C. to about 1500.degree. C. and contacting the heated nano-catalysts with an organic vapor to affix carbon nanostructures to the nano-catalysts and form the anchored nanostructure material.

  9. Integrated three-dimensional photonic nanostructures for achieving near-unity solar absorption and superhydrophobicity

    Science.gov (United States)

    Kuang, Ping; Hsieh, Mei-Li; Lin, Shawn-Yu

    2015-06-01

    In this paper, we proposed and realized 3D photonic nanostructures consisting of ultra-thin graded index antireflective coatings (ARCs) and woodpile photonic crystals. The use of the integrated ARC and photonic crystal structure can achieve broadband, broad-angle near unity solar absorption. The amorphous silicon based photonic nanostructure experimentally shows an average absorption of ˜95% for λ = 400-620 nm over a wide angular acceptance of θ = 0°-60°. Theoretical studies show that a Gallium Arsenide (GaAs) based structure can achieve an average absorption of >95% for λ = 400-870 nm. Furthermore, the use of the slanted SiO2 nanorod ARC surface layer by glancing angle deposition exhibits Cassie-Baxter state wetting, and superhydrophobic surface is obtained with highest water contact angle θCB ˜ 153°. These properties are fundamentally important for achieving maximum solar absorption and surface self-cleaning in thin film solar cell applications.

  10. Interfacing nanostructures to biological cells

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xing; Bertozzi, Carolyn R.; Zettl, Alexander K.

    2012-09-04

    Disclosed herein are methods and materials by which nanostructures such as carbon nanotubes, nanorods, etc. are bound to lectins and/or polysaccharides and prepared for administration to cells. Also disclosed are complexes comprising glycosylated nanostructures, which bind selectively to cells expressing glycosylated surface molecules recognized by the lectin. Exemplified is a complex comprising a carbon nanotube functionalized with a lipid-like alkane, linked to a polymer bearing repeated .alpha.-N-acetylgalactosamine sugar groups. This complex is shown to selectively adhere to the surface of living cells, without toxicity. In the exemplified embodiment, adherence is mediated by a multivalent lectin, which binds both to the cells and the .alpha.-N-acetylgalactosamine groups on the nanostructure.

  11. Nanostructures for protein drug delivery.

    Science.gov (United States)

    Pachioni-Vasconcelos, Juliana de Almeida; Lopes, André Moreni; Apolinário, Alexsandra Conceição; Valenzuela-Oses, Johanna Karina; Costa, Juliana Souza Ribeiro; Nascimento, Laura de Oliveira; Pessoa, Adalberto; Barbosa, Leandro Ramos Souza; Rangel-Yagui, Carlota de Oliveira

    2016-02-01

    Use of nanoscale devices as carriers for drugs and imaging agents has been extensively investigated and successful examples can already be found in therapy. In parallel, recombinant DNA technology together with molecular biology has opened up numerous possibilities for the large-scale production of many proteins of pharmaceutical interest, reflecting in the exponentially growing number of drugs of biotechnological origin. When we consider protein drugs, however, there are specific criteria to take into account to select adequate nanostructured systems as drug carriers. In this review, we highlight the main features, advantages, drawbacks and recent developments of nanostructures for protein encapsulation, such as nanoemulsions, liposomes, polymersomes, single-protein nanocapsules and hydrogel nanoparticles. We also discuss the importance of nanoparticle stabilization, as well as future opportunities and challenges in nanostructures for protein drug delivery. PMID:26580477

  12. Improving the Capacity of Sodium Ion Battery Using a Virus-Templated Nanostructured Composite Cathode

    Energy Technology Data Exchange (ETDEWEB)

    Moradi, M; Li, Z; Qi, JF; Xing, WT; Xiang, K; Chiang, YM; Belcher, AM

    2015-05-01

    In this work we investigated an energy-efficient biotemplated route to synthesize nanostructured FePO4 for sodium-based batteries. Self-assembled M13 viruses and single wall carbon nanotubes (SWCNTs) have been used as a template to grow amorphous FePO4 nanoparticles at room temperature (the active composite is denoted as Bio-FePO4-CNT) to enhance the electronic conductivity of the active material. Preliminary tests demonstrate a discharge capacity as high as 166 mAh/g at C/10 rate, corresponding to composition Na0.9FePO4, which along with higher C-rate tests show this material to have the highest capacity and power performance reported for amorphous FePO4 electrodes to date.

  13. Comparative anomalous small-angle X-ray scattering study of hotwire and plasma grown amorphous silicon-germanium alloys

    OpenAIRE

    Goerigk, G.; Williamson, D. L.

    2001-01-01

    The nanostructure of hydrogenated amorphous silicon-germanium alloys, a-Si1-xGex:H, prepared by the hotwire deposition technique (x=0.06-0.79) and by the plasma enhanced chemical vapor deposition technique (x=0 and 0.50) was analyzed by anomalous small-angle x-ray scattering experiments. For all alloys with x >0 the Ge component was found to be inhomogeneously distributed with correlation lengths of about 1 nm. A systematic increase of the separated scattering was found due to the increasing ...

  14. Microstructural analyses of amorphic diamond, i-C, and amorphous carbon

    DEFF Research Database (Denmark)

    Collins, C. B.; Davanloo, F.; Jander, D.R.;

    1992-01-01

    comparative examinations of the microstructures of samples of amorphic diamond, i-C, and amorphous carbon. Four distinct morphologies were found that correlated closely with the energy densities used in preparing the different materials. Journal of Applied Physics is copyrighted by The American Institute of...... Physics....

  15. Electrons and phonons in amorphous semiconductors

    Science.gov (United States)

    Prasai, Kiran; Biswas, Parthapratim; Drabold, D. A.

    2016-07-01

    The coupling between lattice vibrations and electrons is one of the central concepts of condensed matter physics. The subject has been deeply studied for crystalline materials, but far less so for amorphous and glassy materials, which are among the most important for applications. In this paper, we explore the electron-lattice coupling using current tools of a first-principles computer simulation. We choose three materials to illustrate the phenomena: amorphous silicon (a-Si), amorphous selenium (a-Se) and amorphous gallium nitride (a-GaN). In each case, we show that there is a strong correlation between the localization of electron states and the magnitude of thermally induced fluctuations in energy eigenvalues obtained from the density-functional theory (i.e. Kohn–Sham eigenvalues). We provide a heuristic theory to explain these observations. The case of a-GaN, a topologically disordered partly ionic insulator, is distinctive compared to the covalent amorphous examples. Next, we explore the consequences of changing the charge state of a system as a proxy for tracking photo-induced structural changes in the materials. Where transport is concerned, we lend insight into the Meyer–Neldel compensation rule and discuss a thermally averaged Kubo–Greenwood formula as a means to estimate electrical conductivity and especially its temperature dependence. We close by showing how the optical gap of an amorphous semiconductor can be computationally engineered with the judicious use of Hellmann–Feynman forces (associated with a few defect states) using molecular dynamics simulations. These forces can be used to close or open an optical gap, and identify a structure with a prescribed gap. We use the approach with plane-wave density functional methods to identify a low-energy amorphous phase of silicon including several coordination defects, yet with a gap close to that of good quality a-Si models.

  16. Optical transitions in semiconductor nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Rupasov, Valery I. [ALTAIR Center LLC, Shrewsbury, MA 01545 (United States) and Landau Institute for Theoretical Physics, Moscow (Russian Federation)]. E-mail: rupasov@townisp.com

    2007-03-19

    Employing the Maxwell equations and conventional boundary conditions for the radiation field on the nanostructure interfaces, we compute the radiative spontaneous decay rate of optical transitions in spherical semiconductor nanocrystals, core-shell nanocrystals and nanostructures comprising more than one shell. We also show that the coupling between optical transitions localized in the shell of core-shell nanocrystals and radiation field is determined by both conventional electro-multipole momenta and electro-multipole 'inverse' momenta. The latter are proportional to the core radius even for interband transitions that should result in very strong optical transitions.

  17. Optical transitions in semiconductor nanostructures

    International Nuclear Information System (INIS)

    Employing the Maxwell equations and conventional boundary conditions for the radiation field on the nanostructure interfaces, we compute the radiative spontaneous decay rate of optical transitions in spherical semiconductor nanocrystals, core-shell nanocrystals and nanostructures comprising more than one shell. We also show that the coupling between optical transitions localized in the shell of core-shell nanocrystals and radiation field is determined by both conventional electro-multipole momenta and electro-multipole 'inverse' momenta. The latter are proportional to the core radius even for interband transitions that should result in very strong optical transitions

  18. Vortex ice in nanostructured superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Reichhardt, Charles [Los Alamos National Laboratory; Reichhardt, Cynthia J [Los Alamos National Laboratory; Libal, Andras J [Los Alamos National Laboratory

    2008-01-01

    We demonstrate using numerical simulations of nanostructured superconductors that it is possible to realize vortex ice states that are analogous to square and kagome ice. The system can be brought into a state that obeys either global or local ice rules by applying an external current according to an annealing protocol. We explore the breakdown of the ice rules due to disorder in the nanostructure array and show that in square ice, topological defects appear along grain boundaries, while in kagome ice, individual defects appear. We argue that the vortex system offers significant advantages over other artificial ice systems.

  19. Hidden symmetry in quantum nanostructures

    International Nuclear Information System (INIS)

    Full text: (author)The theoretical investigation of the hidden symmetries influence on the optical properties of the quantum nanostructures is presented. The problems connected with the parabolic approximation of the confinement potential of the system, as well as two-dimensional Coulomb problem on the character of optical transitions in semiconductor nanostructures are discussed. In particular excitonic absorption in quantum filma and character of arrangement of absorption peak depending on the principal quantum number of the two-dimensional Coulombic problem is also discussed

  20. Structural, thermal, optical and photoacoustic study of nanostructured FeSb2 prepared by mechanical alloying

    International Nuclear Information System (INIS)

    Mechanical alloying of elemental Fe and Sb powders yielded nanostructured FeSb2, an amorphous phase, along with unreacted Sb. The volume fractions of FeSb2, Sb nanocrystals and interfacial/amorphous components were estimated from the X-ray diffraction pattern of the as-miller powder. The thermal stability of FeSb2 was investigated by heating the powder at 250 °C and 400 °C. The XRD pattern of the sample annealed at 250 °C showed nucleation of Fe3O4 and decomposition of FeSb2. For an annealing temperature of 400 °C, besides crystallization of the amorphous phase, the volume fractions of Sb and Fe3O4 increased and the volume fraction of FeSb2 decreased. The optical band gap energy for samples as-milled and annealed at 400 °C was measured, and a slight decrease in the band gap was observed in the annealed sample. Thermal diffusivity parameter of the as-milled sample and of the annealed sample at 400 °C was also measured, as well as other transport properties. We also studied the contribution of the thermal diffusivity of the interfacial/amorphous component to the thermal diffusivity of the as-milled sample

  1. Iron-based amorphous alloys and methods of synthesizing iron-based amorphous alloys

    Science.gov (United States)

    Saw, Cheng Kiong; Bauer, William A.; Choi, Jor-Shan; Day, Dan; Farmer, Joseph C.

    2016-05-03

    A method according to one embodiment includes combining an amorphous iron-based alloy and at least one metal selected from a group consisting of molybdenum, chromium, tungsten, boron, gadolinium, nickel phosphorous, yttrium, and alloys thereof to form a mixture, wherein the at least one metal is present in the mixture from about 5 atomic percent (at %) to about 55 at %; and ball milling the mixture at least until an amorphous alloy of the iron-based alloy and the at least one metal is formed. Several amorphous iron-based metal alloys are also presented, including corrosion-resistant amorphous iron-based metal alloys and radiation-shielding amorphous iron-based metal alloys.

  2. Amorphous silicon detectors in positron emission tomography

    Energy Technology Data Exchange (ETDEWEB)

    Conti, M. (Istituto Nazionale di Fisica Nucleare, Pisa (Italy) Lawrence Berkeley Lab., CA (USA)); Perez-Mendez, V. (Lawrence Berkeley Lab., CA (USA))

    1989-12-01

    The physics of the detection process is studied and the performances of different Positron Emission Tomography (PET) system are evaluated by theoretical calculation and/or Monte Carlo Simulation (using the EGS code) in this paper, whose table of contents can be summarized as follows: a brief introduction to amorphous silicon detectors and some useful equation is presented; a Tantalum/Amorphous Silicon PET project is studied and the efficiency of the systems is studied by Monte Carlo Simulation; two similar CsI/Amorphous Silicon PET projects are presented and their efficiency and spatial resolution are studied by Monte Carlo Simulation, light yield and time characteristics of the scintillation light are discussed for different scintillators; some experimental result on light yield measurements are presented; a Xenon/Amorphous Silicon PET is presented, the physical mechanism of scintillation in Xenon is explained, a theoretical estimation of total light yield in Xenon and the resulting efficiency is discussed altogether with some consideration of the time resolution of the system; the amorphous silicon integrated electronics is presented, total noise and time resolution are evaluated in each of our applications; the merit parameters {epsilon}{sup 2}{tau}'s are evaluated and compared with other PET systems and conclusions are drawn; and a complete reference list for Xenon scintillation light physics and its applications is presented altogether with the listing of the developed simulation programs.

  3. Amorphous silicon detectors in positron emission tomography

    International Nuclear Information System (INIS)

    The physics of the detection process is studied and the performances of different Positron Emission Tomography (PET) system are evaluated by theoretical calculation and/or Monte Carlo Simulation (using the EGS code) in this paper, whose table of contents can be summarized as follows: a brief introduction to amorphous silicon detectors and some useful equation is presented; a Tantalum/Amorphous Silicon PET project is studied and the efficiency of the systems is studied by Monte Carlo Simulation; two similar CsI/Amorphous Silicon PET projects are presented and their efficiency and spatial resolution are studied by Monte Carlo Simulation, light yield and time characteristics of the scintillation light are discussed for different scintillators; some experimental result on light yield measurements are presented; a Xenon/Amorphous Silicon PET is presented, the physical mechanism of scintillation in Xenon is explained, a theoretical estimation of total light yield in Xenon and the resulting efficiency is discussed altogether with some consideration of the time resolution of the system; the amorphous silicon integrated electronics is presented, total noise and time resolution are evaluated in each of our applications; the merit parameters ε2τ's are evaluated and compared with other PET systems and conclusions are drawn; and a complete reference list for Xenon scintillation light physics and its applications is presented altogether with the listing of the developed simulation programs

  4. Crystallization of amorphous Zr-Be alloys

    Science.gov (United States)

    Golovkova, E. A.; Surkov, A. V.; Syrykh, G. F.

    2015-02-01

    The thermal stability and structure of binary amorphous Zr100 - x Be x alloys have been studied using differential scanning calorimetry and neutron diffraction over a wide concentration range (30 ≤ x ≤ 65). The amorphous alloys have been prepared by rapid quenching from melt. The studied amorphous system involves the composition range around the eutectic composition with boundary phases α-Zr and ZrBe2. It has been found that the crystallization of alloys with low beryllium contents ("hypoeutectic" alloys with x ≤ 40) proceeds in two stages. Neutron diffraction has demonstrated that, at the first stage, α-Zr crystallizes and the remaining amorphous phase is enriched to the eutectic composition; at the second stage, the alloy crystallizes in the α-Zr and ZrBe2 phases. At higher beryllium contents ("hypereutectic" alloys), one phase transition of the amorphous phase to a mixture of the α-Zr and ZrBe2 phases has been observed. The concentration dependences of the crystallization temperature and activation energy have been revealed.

  5. Controlled placement and orientation of nanostructures

    Science.gov (United States)

    Zettl, Alex K; Yuzvinsky, Thomas D; Fennimore, Adam M

    2014-04-08

    A method for controlled deposition and orientation of molecular sized nanoelectromechanical systems (NEMS) on substrates is disclosed. The method comprised: forming a thin layer of polymer coating on a substrate; exposing a selected portion of the thin layer of polymer to alter a selected portion of the thin layer of polymer; forming a suspension of nanostructures in a solvent, wherein the solvent suspends the nanostructures and activates the nanostructures in the solvent for deposition; and flowing a suspension of nanostructures across the layer of polymer in a flow direction; thereby: depositing a nanostructure in the suspension of nanostructures only to the selected portion of the thin layer of polymer coating on the substrate to form a deposited nanostructure oriented in the flow direction. By selectively employing portions of the method above, complex NEMS may be built of simpler NEMSs components.

  6. Computer Code for Nanostructure Simulation

    Science.gov (United States)

    Filikhin, Igor; Vlahovic, Branislav

    2009-01-01

    Due to their small size, nanostructures can have stress and thermal gradients that are larger than any macroscopic analogue. These gradients can lead to specific regions that are susceptible to failure via processes such as plastic deformation by dislocation emission, chemical debonding, and interfacial alloying. A program has been developed that rigorously simulates and predicts optoelectronic properties of nanostructures of virtually any geometrical complexity and material composition. It can be used in simulations of energy level structure, wave functions, density of states of spatially configured phonon-coupled electrons, excitons in quantum dots, quantum rings, quantum ring complexes, and more. The code can be used to calculate stress distributions and thermal transport properties for a variety of nanostructures and interfaces, transport and scattering at nanoscale interfaces and surfaces under various stress states, and alloy compositional gradients. The code allows users to perform modeling of charge transport processes through quantum-dot (QD) arrays as functions of inter-dot distance, array order versus disorder, QD orientation, shape, size, and chemical composition for applications in photovoltaics and physical properties of QD-based biochemical sensors. The code can be used to study the hot exciton formation/relation dynamics in arrays of QDs of different shapes and sizes at different temperatures. It also can be used to understand the relation among the deposition parameters and inherent stresses, strain deformation, heat flow, and failure of nanostructures.

  7. Some properties of electrochemical nanostructures

    Indian Academy of Sciences (India)

    E Santos; P Quaino; German Soldano; W Schmickler

    2009-09-01

    The physical and electronic properties of several platinum nanostructures have been investigated by density functional calculations. Particular attention has been paid to the structure of the -band. Our results predict, that nanowires and small platinum clusters supported on Au(111) should be excellent catalysts for the hydrogen evolution reaction; a monolayer of platinum on Au(111) should also be better than pure platinum.

  8. Noncollinear magnetism in manganese nanostructures

    Czech Academy of Sciences Publication Activity Database

    Zelený, Martin; Šob, Mojmír; Hafner, J.

    2009-01-01

    Roč. 80, č. 14 (2009), 144414/1-144414/19. ISSN 1098-0121 R&D Projects: GA AV ČR IAA100100920; GA MŠk OC09011 Institutional research plan: CEZ:AV0Z20410507 Keywords : magnetism of nanostructures * nanowires * noncollinear magnetism * manganese Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.475, year: 2009

  9. Nanostructures for Organic Solar Cells

    DEFF Research Database (Denmark)

    Goszczak, Arkadiusz Jarosław

    2016-01-01

    The experimental work in this thesis is focused on the fabrication of nanostructures that can be implemented in organic solar cell (OSC) architecture for enhancement of the device performance. Solar devices made from organic material are gaining increased attention, compared to their inorganic...... for organic solar cell applications, opening new patterning possibilities....

  10. Thermoelectric effects in magnetic nanostructures

    NARCIS (Netherlands)

    Hatami, M.; Bauer, G.E.W.; Zhang, Q.; Kelly, P.J.

    2009-01-01

    We model and evaluate the Peltier and Seebeck effects in magnetic multilayer nanostructures by a finite-element theory of thermoelectric properties. We present analytical expressions for the thermopower and the current-induced temperature changes due to Peltier cooling/heating. The thermopower of a

  11. Strain Rate Induced Amorphization in Metallic Nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Y.; Cagin, T.; Goddard, W.A. III [Materials and Process Simulation Center, California Institute of Technology, Pasadena, California 91125 (United States); Ikeda, H.; Samwer, K.; Johnson, W.L. [Keck Laboratory of Engineering Materials, California Institute of Technology, Pasadena, California 91125 (United States)

    1999-04-01

    Using molecular dynamics simulations with a many-body force field, we studied the deformation of single crystal Ni and NiCu random alloy nanowires subjected to uniform strain rates but kept at 300thinspthinspK. For all strain rates, the Ni nanowire is elastic up to 7.5{percent} strain with a yield stress of 5.5thinspthinspGPa, far above that of bulk Ni. At high strain rates, we find that for both systems the crystalline phase transforms continuously to an amorphous phase, exhibiting a dramatic change in atomic short-range order and a near vanishing of the tetragonal shear elastic constant perpendicular to the tensile direction. This amorphization which occurs directly from the homogeneous, elastically deformed system with no chemical or structural inhomogeneities exhibits a new mode of amorphization. {copyright} {ital 1999} {ital The American Physical Society}

  12. Fabrication and application of amorphous semiconductor devices

    International Nuclear Information System (INIS)

    This invention concerns the design and manufacture of elecric switching or memorisation components with amorphous semiconductors. As is known some compounds, particularly the chalcogenides, have a resistivity of the semiconductor type in the amorphous solid state. These materials are obtained by the high temperature homogeneisation of several single elements such as tellurium, arsenic, germanium and sulphur, followed by water or air quenching. In particular these compounds have useful switching and memorisation properties. In particular they have the characteristic of not suffering deterioration when placed in an environment subjected to nuclear radiations. In order to know more about the nature and properties of these amorphous semiconductors the French patent No. 71 28048 of 30 June 1971 may be consulted with advantage

  13. Amorphous metallic films in silicon metallization systems

    Science.gov (United States)

    So, F.; Kolawa, E.; Nicolet, M. A.

    1985-01-01

    Diffusion barrier research was focussed on lowering the chemical reactivity of amorphous thin films on silicon. An additional area of concern is the reaction with metal overlays such as aluminum, silver, and gold. Gold was included to allow for technology transfer to gallium arsenide PV cells. Amorphous tungsten nitride films have shown much promise. Stability to annealing temperatures of 700, 800, and 550 C were achieved for overlays of silver, gold, and aluminum, respectively. The lower results for aluminum were not surprising because there is an eutectic that can form at a lower temperature. It seems that titanium and zirconium will remove the nitrogen from a tungsten nitride amorphous film and render it unstable. Other variables of research interest were substrate bias and base pressure during sputtering.

  14. Transverse and longitudinal vibrations in amorphous silicon

    Science.gov (United States)

    Beltukov, Y. M.; Fusco, C.; Tanguy, A.; Parshin, D. A.

    2015-12-01

    We show that harmonic vibrations in amorphous silicon can be decomposed to transverse and longitudinal components in all frequency range even in the absence of the well defined wave vector q. For this purpose we define the transverse component of the eigenvector with given ω as a component, which does not change the volumes of Voronoi cells around atoms. The longitudinal component is the remaining orthogonal component. We have found the longitudinal and transverse components of the vibrational density of states for numerical model of amorphous silicon. The vibrations are mostly transverse below 7 THz and above 15 THz. In the frequency interval in between the vibrations have a longitudinal nature. Just this sudden transformation of vibrations at 7 THz from almost transverse to almost longitudinal ones explains the prominent peak in the diffusivity of the amorphous silicon just above 7 THz.

  15. Plasmonic Nanostructures for Biosensor Applications

    Science.gov (United States)

    Gadde, Akshitha

    Improving the sensitivity of existing biosensors is an active research topic that cuts across several disciplines, including engineering and biology. Optical biosensors are the one of the most diverse class of biosensors which can be broadly categorized into two types based on the detection scheme: label-based and label-free detection. In label-based detection, the target bio-molecules are labeled with dyes or tags that fluoresce upon excitation, indicating the presence of target molecules. Label-based detection is highly-sensitive, capable of single molecule detection depending on the detector type used. One method of improving the sensitivity of label-based fluorescence detection is by enhancement of the emission of the labels by coupling them with metal nanostructures. This approach is referred as plasmon-enhanced fluorescence (PEF). PEF is achieved by increasing the electric field around the nano metal structures through plasmonics. This increased electric field improves the enhancement from the fluorophores which in turn improves the photon emission from the fluorophores which, in turn, improves the limit of detection. Biosensors taking advantage of the plasmonic properties of metal films and nanostructures have emerged an alternative, low-cost, high sensitivity method for detecting labeled DNA. Localized surface plasmon resonance (LSPR) sensors employing noble metal nanostructures have recently attracted considerable attention as a new class of plasmonic nanosensors. In this work, the design, fabrication and characterization of plasmonic nanostructures is carried out. Finite difference time domain (FDTD) simulations were performed using software from Lumerical Inc. to design a novel LSPR structure that exhibit resonance overlapping with the absorption and emission wavelengths of quantum dots (QD). Simulations of a composite Au/SiO2 nanopillars on silicon substrate were performed using FDTD software to show peak plasmonic enhancement at QD emission wavelength

  16. Amorphous Fe-based metal foam

    International Nuclear Information System (INIS)

    A foam synthesis method that takes advantage of the viscous high-temperature liquid state of Fe-based bulk glass-forming alloys to produce amorphous steel foam is introduced. Zirconium hydride is utilized as a foaming agent taking advantage of the low hydrogen solubility of these glass-forming alloys. Amorphous foams with porosities up to 65% were produced having homogenous cellular morphologies that exhibit cell-size uniformity. Even though intracellular solid regions as thin as a few micrometers are detected, on a global scale the cellular structure is determined to be incapable of alleviating the foam from the brittle nature of the monolithic glass

  17. Ion bombardment and disorder in amorphous silicon

    International Nuclear Information System (INIS)

    The effect of ion bombardment during growth on the structural and optical properties of amorphous silicon are presented. Two series of films were deposited under electrically grounded and positively biased substrate conditions. The biased samples displayed lower growth rates and increased hydrogen content relative to grounded counterparts. The film structure was examined using Raman spectroscopy. The transverse optic like phonon band position was used as a parameter to characterize network order. Biased samples displayed an increased order of the amorphous network relative to grounded samples. Furthermore, biased samples exhibited a larger optical gap. These results are correlated and attributed to reduced ion bombardment effects

  18. Neutron scattering studies of amorphous Invar alloys

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez-Baca, J.A.

    1989-01-01

    This paper reviews recent inelastic neutron scattering experiments performed to study the spin dynamics of two amorphous Invar systems: Fe/sub 100-x/B/sub x/ and Fe/sub 90-x/Ni/sub x/Zr/sub 10/. As in crystalline Invar Fe/sub 65/Ni/sub 35/ and Fe/sub 3/Pt, the excitation of conventional long-wavelength spin waves in these amorphous systems cannot account for the relatively rapid change of their magnetization with temperature. These results are discussed in terms of additional low-lying excitations which apparently have a density of states similar to the spin waves.

  19. Raman Amplifier Based on Amorphous Silicon Nanoparticles

    OpenAIRE

    M.A. Ferrara; Rendina, I.; S. N. Basu; Dal Negro, L.; Sirleto, L.

    2012-01-01

    The observation of stimulated Raman scattering in amorphous silicon nanoparticles embedded in Si-rich nitride/silicon superlattice structures (SRN/Si-SLs) is reported. Using a 1427 nm continuous-wavelength pump laser, an amplification of Stokes signal up to 0.9 dB/cm at 1540.6 nm and a significant reduction in threshold power of about 40% with respect to silicon are experimentally demonstrated. Our results indicate that amorphous silicon nanoparticles are a great promise for Si-based Raman la...

  20. Nanoindentation-induced amorphization in silicon carbide

    Science.gov (United States)

    Szlufarska, Izabela; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya

    2004-07-01

    The nanoindentation-induced amorphization in SiC is studied using molecular dynamics simulations. The load-displacement response shows an elastic shoulder followed by a plastic regime consisting of a series of load drops. Analyses of bond angles, local pressure, and shear stress, and shortest-path rings show that these drops are related to dislocation activities under the indenter. We show that amorphization is driven by coalescence of dislocation loops and that there is a strong correlation between load-displacement response and ring distribution.

  1. Characterization of inhomogeneities in amorphous superconductors

    International Nuclear Information System (INIS)

    The structure and superconducting properties of rapidly quenched Zr-Ni and Zr-V alloys have been studied by XRD, EXAFS spectroscopy, TEM, electron diffraction, ED, electrical resistivity and ac susceptibility measurements. Amorphous Zr66Ni34 ribbons quenched with different cooling rates were also examined by flux pinning measurements. Characteristic differences are observed in the flux pinning mechanisms of microcrystalline and amorphous samples. The temperature dependence of upper critical fields have been measured down to 0.4 K and the results are analyzed in terms of WHH theory

  2. Fabrication of zein nanostructure

    Science.gov (United States)

    Luecha, Jarupat

    resins. The soft lithography technique was mainly used to fabricate micro and nanostructures on zein films. Zein material well-replicated small structures with the smallest size at sub micrometer scale that resulted in interesting photonic properties. The bonding method was also developed for assembling portable zein microfluidic devices with small shape distortion. Zein-zein and zein-glass microfluidic devices demonstrated sufficient strength to facilitate fluid flow in a complex microfluidic design with no leakage. Aside from the fabrication technique development, several potential applications of this environmentally friendly microfluidic device were investigated. The concentration gradient manipulation of Rhodamine B solution in zein-glass microfluidic devices was demonstrated. The diffusion of small molecules such as fluorescent dye into the wall of the zein microfluidic channels was observed. However, with this formulation, zein microfluidic devices were not suitable for cell culture applications. This pioneer study covered a wide spectrum of the implementation of the two nanotechnology approaches to advance zein biomaterial which provided proof of fundamental concepts as well as presenting some limitations. The findings in this study can lead to several innovative research opportunities of advanced zein biomaterials with broad applications. The information from the study of zein nanocomposite structure allows the packaging industry to develop the low cost biodegradable materials with physical property improvement. The information from the study of the zein microfluidic devices allows agro-industry to develop the nanotechnology-enabled microfluidic sensors fabricated entirely from biodegradable polymer for on-site disease or contaminant detection in the fields of food and agriculture.

  3. Polymeric amorphous carbon as p-type window within amorphous silicon solar cells

    OpenAIRE

    Khan, R U A; Silva, S. R. P.; Van Swaaij, R.A.C.M.M.

    2003-01-01

    Amorphous carbon (a-C) has been shown to be intrinsically p-type, and polymeric a-C (PAC) possesses a wide Tauc band gap of 2.6 eV. We have replaced the p-type amorphous silicon carbide layer of a standard amorphous silicon solar cell with an intrinsic ultrathin layer of PAC. The thickness of the p layer had to be reduced from 9 to 2.5 nm in order to ensure sufficient conduction through the PAC film. Although the resulting external parameters suggest a decrease in the device efficiency from 9...

  4. A Selective Metasurface Absorber with An Amorphous Carbon Interlayer for Solar Thermal Applications

    CERN Document Server

    Wan, Chenglong; Nunez-Sanchez, S; Chen, Lifeng; Lopez-Garcia, M; Pugh, J; Zhu, Bofeng; Selvaraj, P; Mallick, T; Senthilarasu, S; Cryan, M J

    2016-01-01

    This paper presents fabrication, measurement and modelling results for a metal-dielectric-metal metasurface absorber for solar thermal applications. The structure uses amorphous carbon as an inter-layer between thin gold films with the upper film patterned with a 2D periodic array using focused ion beam etching. The patterned has been optimised to give high absorptance from 400-1200nm and low absorptance above this wavelength range to minimise thermal radiation and hence obtain higher temperature performance. Wide angle absorptance results are shown and detailed modelling of a realistic nanostructured upper layer results in excellent agreement between measured and modelled results. The use of gold in this paper is a first step towards a high temperature metasurface where gold can be replaced by other refractory metals such as tungsten or chrome.

  5. Characteristics of Disorder and Defect in Hydrogenated Amorphous Silicon Nitride Thin Films Containing Silicon Nanograins

    Institute of Scientific and Technical Information of China (English)

    DING Wen-ge; YU Wei; ZHANG Jiang-yong; HAN Li; FU Guang-sheng

    2006-01-01

    The hydrogenated amorphous silicon nitride (SiNx) thin films embedded with nano-structural silicon were prepared and the microstructures at the interface of silicon nano-grains/SiNx were identified by the optical absorption and Raman scattering measurements. Characterized by the exponential tail of optical absorption and the band-width of the Raman scattering TO mode, the disorder in the interface region increases with the gas flow ratio increasing. Besides, as reflected by the sub-gap absorption coefficients, the density of interface defect states decreases, which can be attributed to the structural mismatch in the interface region and also the changes of hydrogen content in the deposited films. Additional annealing treatment results in a significant increase of defects and degree of disorder, for which the hydrogen out-diffusion in the annealing process would be responsible.

  6. Inverted amorphous silicon solar cell utilizing cermet layers

    Science.gov (United States)

    Hanak, Joseph J.

    1979-01-01

    An amorphous silicon solar cell incorporating a transparent high work function metal cermet incident to solar radiation and a thick film cermet contacting the amorphous silicon opposite to said incident surface.

  7. Low-Temperature Crystallization of Amorphous Silicate in Astrophysical Environments

    CERN Document Server

    Tanaka, Kyoko K; Kimura, Hiroshi

    2010-01-01

    We construct a theoretical model for low-temperature crystallization of amorphous silicate grains induced by exothermic chemical reactions. As a first step, the model is applied to the annealing experiments, in which the samples are (1) amorphous silicate grains and (2) amorphous silicate grains covered with an amorphous carbon layer. We derive the activation energies of crystallization for amorphous silicate and amorphous carbon from the analysis of the experiments. Furthermore, we apply the model to the experiment of low-temperature crystallization of amorphous silicate core covered with an amorphous carbon layer containing reactive molecules. We clarify the conditions of low-temperature crystallization due to exothermic chemical reactions. Next, we formulate the crystallization conditions so as to be applicable to astrophysical environments. We show that the present crystallization mechanism is characterized by two quantities: the stored energy density Q in a grain and the duration of the chemical reaction...

  8. Nano structures of amorphous silicon: localization and energy gap

    Directory of Open Access Journals (Sweden)

    Z Nourbakhsh

    2013-10-01

    Full Text Available Renewable energy research has created a push for new materials; one of the most attractive material in this field is quantum confined hybrid silicon nano-structures (nc-Si:H embedded in hydrogenated amorphous silicon (a-Si:H. The essential step for this investigation is studying a-Si and its ability to produce quantum confinement (QC in nc-Si: H. Increasing the gap of a-Si system causes solar cell efficiency to increase. By computational calculations based on Density Functional Theory (DFT, we calculated a special localization factor, [G Allan et al., Phys. Rev. B 57 (1997 6933.], for the states close to HOMO and LUMO in a-Si, and found most weak-bond Si atoms. By removing these silicon atoms and passivating the system with hydrogen, we were able to increase the gap in the a-Si system. As more than 8% hydrogenate was not experimentally available, we removed about 2% of the most localized Si atoms in the almost tetrahedral a-Si system. After removing localized Si atoms in the system with 1000 Si atoms, and adding 8% H, the gap increased about 0.24 eV. Variation of the gap as a function of hydrogen percentage was in good agreement with the Tight –Binding results, but about 2 times more than its experimental value. This might come from the fact that in the experimental conditions, it does not have the chance to remove the most localized states. However, by improving the experimental conditions and technology, this value can be improved.

  9. Phase transformation and microstructural evolution of nanostructured oxides and nitrides under ion irradiations

    Science.gov (United States)

    Lu, Fengyuan

    Material design at the nanometer scale is an effective strategy for developing advanced materails with enhanced radiation tolerance for advanced nuclear energy systems as high densities of surfaces and interfaces of the nanostructured materials may behave as effective sinks for defect recovery. However, nanostructured materials may not be intrinsically radiation tolerant, and the interplay among the factors of crystal size, temperature, chemical composition, surface energy and radiation conditions may eventually determine material radiation behaviors. Therefore, it is necessary to understand the radiation effects of nanostructured materials and the underlying physics for the design of advanced nanostructured nuclear materials. The main objective of this doctoral thesis is to study the behavior of nanostructured oxides and nitrides used as fuel matrix and waste forms under extreme radiation conditions with the focus of phase transformation, microstructural evolution and damage mechanisms. Radiation experiments were performed using energetic ion beam techniques to simulate radiation damage resulting from energetic neutrons, alpha-decay events and fission fragments, and various experimental approaches were employed to characterize materials’ microstructural evolution and phase stability upon intense radiation environments including transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. Thermal annealing experiments indicated that nanostructured ZrO2 phase stability is strongly affected by the grain size. Radiation results on nanostructured ZrO2 indicated that thermodynamically unstable or metastable high temperature phases can be induced by energetic beam irradiation at room temperature. Various phase transformation among different polymorphs of monoclinic, tetragonal and amorphous states can be induced, and different mechanisms are responsible for structural transformations including oxygen vacancies accumulation upon displacive

  10. Removing and Recovering Phosphate from Poultry Wastewater Using Amorphous Ceramics

    OpenAIRE

    Youhui Xie; Qin Li; Xianzhi Zhao; Yi Luo; Yangming Wang; Xiangwei Peng; Qigui Wang; Jian Su; Yin Lu

    2014-01-01

    A novel and effective technique for phosphate from poultry wastewater was developed using amorphous ceramics. Amorphous ceramics, which showed high performance for phosphate removal and recovery from poultry wastewater, were synthesized using unlimitedly available, inexpensive materials such as silica fume and lime. Dissolved phosphate in poultry wastewater can be deposited as a solid on the surface of amorphous ceramics. Phosphate content on the surface of amorphous ceramics could reach 14.2...

  11. Amorphization of embedded Cu nanocrystals by ion irradiation

    International Nuclear Information System (INIS)

    While bulk crystalline elemental metals cannot be amorphized by ion irradiation in the absence of chemical impurities, the authors demonstrate that finite-size effects enable the amorphization of embedded Cu nanocrystals. The authors form and compare the atomic-scale structure of the polycrystalline, nanocrystalline, and amorphous phases, present an explanation for the extreme sensitivity to irradiation exhibited by nanocrystals, and show that low-temperature annealing is sufficient to return amorphized material to the crystalline form

  12. Radiative recombination of excitons in amorphous semiconductors

    International Nuclear Information System (INIS)

    A theory for calculating the radiative lifetime of excitons in amorphous semiconductors is presented. Four possibilities of excitonic radiative recombination are considered and the corresponding rates are derived at thermal equilibrium. The radiative lifetime is calculated from the inverse of the maximum rate for all the four possibilities. Results agree very well with experiments

  13. A Robust Universal Flying Amorphous Computer

    Czech Academy of Sciences Publication Activity Database

    Petrů, Lukáš; Wiedermann, Jiří

    Cham: Springer, 2014 - (Calude, C.; Freivalds, R.; Kazuo, I.), s. 421-435. (Lecture Notes in Computer Science. 8808). ISBN 978-3-319-13349-2 R&D Projects: GA ČR GAP202/10/1333 Institutional support: RVO:67985807 Keywords : amorphous computing * universal computation * computational complexity Subject RIV: IN - Informatics, Computer Science

  14. Noise and degradation of amorphous silicon devices

    NARCIS (Netherlands)

    Bakker, J.P.R.

    2003-01-01

    Electrical noise measurements are reported on two devices of the disordered semiconductor hydrogenated amorphous silicon (a-Si:H). The material is applied in sandwich structures and in thin-film transistors (TFTs). In a sandwich configuration of an intrinsic layer and two thin doped layers, the obse

  15. Film adhesion in amorphous silicon solar cells

    Indian Academy of Sciences (India)

    A R M Yusoff; M N Syahrul; K Henkel

    2007-08-01

    A major issue encountered during fabrication of triple junction -Si solar cells on polyimide substrates is the adhesion of the solar cell thin films to the substrates. Here, we present our study of film adhesion in amorphous silicon solar cells made on different polyimide substrates (Kapton VN, Upilex-S and Gouldflex), and the effect of tie coats on film adhesion.

  16. Trap level spectroscopy in amorphous semiconductors

    CERN Document Server

    Mikla, Victor V

    2010-01-01

    Although amorphous semiconductors have been studied for over four decades, many of their properties are not fully understood. This book discusses not only the most common spectroscopic techniques but also describes their advantages and disadvantages.Provides information on the most used spectroscopic techniquesDiscusses the advantages and disadvantages of each technique

  17. Preparation of hydrogenated amorphous silicon tin alloys

    OpenAIRE

    Vergnat, M.; Marchal, G.; Piecuch, M.

    1987-01-01

    This paper describes a new method to obtain hydrogenated amorphous semiconductor alloys. The method is reactive co-evaporation. Silicon tin hydrogenated alloys are prepared under atomic hydrogen atmosphere. We discuss the influence of various parameters of preparation (hydrogen pressure, tungsten tube temperature, substrate temperature, annealing...) on electrical properties of samples.

  18. Neutron diffraction studies of amorphous solids

    International Nuclear Information System (INIS)

    A brief survey is presented of the role of neutron diffraction in structural studies of amorphous solids. The inherent limitations of the diffraction technique are discussed, together with modern instrumentation and methods for separating individual component correlation functions. An introduction is given to the use of modelling and the extraction of structural parameters from experimental data. (author)

  19. Structural studies of amorphous Se under pressure

    OpenAIRE

    Tanaka, Keiji

    1990-01-01

    X-ray-diffraction patterns, macroscopic compressibility, and crystallization in amorphous Se subject to pressure have been investigated. The material exhibits pressure-induced structural modifications in the glassy state and a phase transformation to the hexagonal phase at 120±20 kbar. The observations are discussed on the basis of microscopic and thermodynamic models.

  20. Ion-assisted recrystallization of amorphous silicon

    Science.gov (United States)

    Priolo, F.; Spinella, C.; La Ferla, A.; Rimini, E.; Ferla, G.

    1989-12-01

    Our recent work on ion-beam-assisted epitaxial growth of amorphous Si layers on single crystal substrates is reviewed. The planar motion of the crystal-amorphous interface was monitored in situ, during irradiations, by transient reflectivity measurements. This technique allows the measurement of the ion-induced growth rate with a very high precision. We have observed that this growth rate scales linearly with the number of displacements produced at the crystal-amorphous interface by the impinging ions. Moreover the regrowth onto oriented substrates is a factor of ≈ 4 faster with respect to that on substrates. Impurities dissolved in the amorphous layer influence the kinetics of recrystallization. For instance, dopants such as As, B and P enhance the ion-induced growth rate while oxygen has the opposite effect. The dependence of the rate on impurity concentration is however less strong with respect to pure thermal annealing. For instance, an oxygen concentration of 1 × 1021 / cm3 decreases the ion-induced growth rate by a factor of ≈ 3; this same concentration would have decreased the rate of pure thermal annealing by more than 4 orders of magnitude. The reduced effects of oxygen during ion-beam crystallization allow the regrowth of deposited Si layers despite the presence of a high interfacial oxygen content. The process is investigated in detail and its possible application to the microelectronic technology is discussed.

  1. Amorphous track models: A numerical comparison study

    DEFF Research Database (Denmark)

    Greilich, Steffen; Grzanka, L.; Bassler, N.; Andersen, Claus Erik; Jäkel, O.

    2010-01-01

    We present an open-source code library for amorphous track modelling which is suppose to faciliate the application and numerical comparability as well as serve as a frame-work for the implementation of new models. We show an example of using the library indicating the choice of submodels has a...

  2. 13C NMR spectroscopy of amorphous hydrogenated carbon and amorphous hydrogenated boron carbide

    International Nuclear Information System (INIS)

    We report the 13C NMR spectrum of amorphous hydrogenated carbon and boron carbide. The amorphous hydrogenated carbon spectra consist primarily of an sp3 line at 40 ppm and an sp2 line at 140 ppm and are in reasonable agreement with the recent theoretical calculations of Mauri, Pfrommer, and Louie, but there are some notable discrepancies. The amorphous hydrogenated boron carbide spectra are very different from those of amorphous hydrogenated carbon, being dominated by one line at 15 ppm. We interpret this line as due to carbon bound in boron carbide icosahedra, because polycrystalline boron carbide with boron carbide icosahedra as the unit cell gives very similar NMR spectra. copyright 1999 The American Physical Society

  3. Characterization of Amorphous and Co-Amorphous Simvastatin Formulations Prepared by Spray Drying

    DEFF Research Database (Denmark)

    Craye, Goedele; Löbmann, Korbinian; Grohganz, Holger;

    2015-01-01

    In this study, spray drying from aqueous solutions, using the surface-active agent sodium lauryl sulfate (SLS) as a solubilizer, was explored as a production method for co-amorphous simvastatin-lysine (SVS-LYS) at 1:1 molar mixtures, which previously have been observed to form a co......-amorphous mixture upon ball milling. In addition, a spray-dried formulation of SVS without LYS was prepared. Energy-dispersive X-ray spectroscopy (EDS) revealed that SLS coated the SVS and SVS-LYS particles upon spray drying. X-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC) showed that in...... studied formulations were able to significantly extend the stability of amorphous SVS compared to previous co-amorphous formulations of SVS. The best stability (at least 12 months in dry conditions) was observed when SLS was spray-dried with SVS (and LYS). In conclusion, spray drying of SVS and LYS from...

  4. Annealing induced structural evolution and electrochromic properties of nanostructured tungsten oxide films

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Ching-Lin [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan, ROC (China); Lin, Chung-Kwei [School of Dental Technology, Taipei Medical University, Taipei City 110, Taiwan, ROC (China); Wang, Chun-Kai [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan, ROC (China); Wang, Sheng-Chang [Department of Mechanical Engineering, Southern Taiwan University, Tainan 710, Taiwan, ROC (China); Huang, Jow-Lay, E-mail: JLH888@mail.ncku.edu.tw [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan, ROC (China); Department of Chemical and Materials Engineering, National University of Kaohsiung, Kaohsiung 81148, Taiwan, ROC (China); Research Center for Energy Technology and Strategy, National Cheng Kung University, Tainan 701, Taiwan, ROC (China)

    2013-12-31

    The effect of microstructure on the optical and electrochemical properties of nanostructured tungsten oxide films was evaluated as a function of annealing temperature. The films using block copolymer as the template were prepared from peroxotungstic acid (PTA) by spin-coating onto the substrate and post-annealed at 250–400 °C to form tungsten oxide films with nanostructure. The microstructure of the films was measured by X-ray diffraction and surface electron microscopy. The films annealed at temperatures below 300 °C are characterized by amorphous or nanocrystalline structures with a pore size of less than 10 nm. The evaluated annealing temperature caused a triclinic crystalline structure and microcracks. Cyclic voltammetry measurements were performed in a LiClO{sub 4}-propylene carbonate electrolyte. The results showed that the ion inserted capacity were maximized for films annealed at 300 °C and decreased with the increasing of annealing temperature. The electrochromic properties of the nanostructured tungsten oxide films were evaluated simultaneously by potentiostat and UV–vis spectroscopy. The films annealed at 300 °C exhibit high transmission modulation (∆T ∼ 40%) at λ = 633 nm and good kinetic properties. As a result, the correlation between the microstructure and kinetic properties was established, and the electrochromic properties have been demonstrated. - Highlights: • Surfactant-assisted WO{sub 3} films have been prepared by sol–gel method. • Nanostructure of porous WO{sub 3} film is retained after crystallization. • Kinetic properties of WO{sub 3} can be improved by nanostructure and crystallinity.

  5. Synthesis, characterization and formation mechanism of single-phase nanostructure bredigite powder

    International Nuclear Information System (INIS)

    Single-phase nanocrystalline bredigite powder was successfully synthesized by mechanical activation of talc, calcium carbonate, and amorphous silica powder mixture followed by annealing. Simultaneous thermal analysis (STA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS),and Fourier transform infrared spectroscopy (FT-IR) techniques were employed to characterize various powders. Single-phase nanostructure bredigite powder with crystallite size of about 65 nm was synthesized by 20 h of mechanical activation with subsequent annealing at 1200 °C for 1 h. The bredigite formation mechanism was studied. During the formation process of nanostructure bredigite powder some intermediate compounds such as wollastonite (CaSiO3), larnite (Ca2SiO4), merwinite (Ca3MgSi2O8), and calcium magnesium silicate (Ca5MgSi3O12) were formed. It was found that bredigite was not produced directly and that the formation of merwinite, enstatite and Ca5MgSi3O12was unavoidable during the synthesis of bredigite. - Graphical abstract: This paper reports the successful synthesis of nanostructure bredigite powder by mechanical activation with subsequent annealing. The results showed that during the formation of bredigite powder some transition compounds such as wollastonite (CaSiO3), larnite (Ca2SiO4), merwinite (Ca3MgSi2O8), and calcium magnesium silicate (Ca5MgSi3O12) were formed. Highlights: ► Mechanical activation improved the kinetics of bredigite formation. ► A mechanism was suggested for the nanostructure bredigite formation. ► During the formation of bredigite powder some intermediate compounds were formed. ► The nanostructure bredigite powder had a mean crystallite size of about 65 nm.

  6. AMORPHOUS COATING FORMING IN THE CONDITIONS OF GAS THERMAL SPRAYING

    Directory of Open Access Journals (Sweden)

    V. V. Artemchuk

    2010-06-01

    Full Text Available In the article the issues of forming amorphous coatings in the conditions of gas thermal spraying of coating are considered. On the basis of theoretical analysis the technological factors, determining possibility of obtaining the amorphous coatings at detonation spraying, are formulated. Two groups of factors, influencing on formation of amorphous structure in detonation sprayed coatings from metallic alloys, are marked.

  7. Chemical Sensors Based on Metal Oxide Nanostructures

    Science.gov (United States)

    Hunter, Gary W.; Xu, Jennifer C.; Evans, Laura J.; VanderWal, Randy L.; Berger, Gordon M.; Kulis, Mike J.; Liu, Chung-Chiun

    2006-01-01

    This paper is an overview of sensor development based on metal oxide nanostructures. While nanostructures such as nanorods show significan t potential as enabling materials for chemical sensors, a number of s ignificant technical challenges remain. The major issues addressed in this work revolve around the ability to make workable sensors. This paper discusses efforts to address three technical barriers related t o the application of nanostructures into sensor systems: 1) Improving contact of the nanostructured materials with electrodes in a microse nsor structure; 2) Controling nanostructure crystallinity to allow co ntrol of the detection mechanism; and 3) Widening the range of gases that can be detected by using different nanostructured materials. It is concluded that while this work demonstrates useful tools for furt her development, these are just the beginning steps towards realizati on of repeatable, controlled sensor systems using oxide based nanostr uctures.

  8. Nanostructured materials for water desalination

    International Nuclear Information System (INIS)

    Desalination of seawater and brackish water is becoming an increasingly important means to address the scarcity of fresh water resources in the world. Decreasing the energy requirements and infrastructure costs of existing desalination technologies remains a challenge. By enabling the manipulation of matter and control of transport at nanometer length scales, the emergence of nanotechnology offers new opportunities to advance water desalination technologies. This review focuses on nanostructured materials that are directly involved in the separation of water from salt as opposed to mitigating issues such as fouling. We discuss separation mechanisms and novel transport phenomena in materials including zeolites, carbon nanotubes, and graphene with potential applications to reverse osmosis, capacitive deionization, and multi-stage flash, among others. Such nanostructured materials can potentially enable the development of next-generation desalination systems with increased efficiency and capacity. (topical review)

  9. Solar batteries based on nanostructures

    International Nuclear Information System (INIS)

    Currently, 90 percent of the solar cells based on silicon are single batteries. The main factors preventing the photoenergetics extensive operation can be applied as follows: 1) the high cost of silicon production for solar cells, which is the main material; 2) the production of solar cells requires increased financial charges; 3) the relatively low efficiency of silicon solar cells (12-18 percent) and finally the last reason - there is no enough effective investment mechanism to solve the problem in most countries. One of the most promising ways to reduce the cost of solar electrical power is the creation of a new generation of solar cells based on semiconductor nanostructures. There are huge amount of research works being done in the field of constant theoretical and practical consequences of implementation of nanostructures

  10. Topology optimization of piezoelectric nanostructures

    Science.gov (United States)

    Nanthakumar, S. S.; Lahmer, Tom; Zhuang, Xiaoying; Park, Harold S.; Rabczuk, Timon

    2016-09-01

    We present an extended finite element formulation for piezoelectric nanobeams and nanoplates that is coupled with topology optimization to study the energy harvesting potential of piezoelectric nanostructures. The finite element model for the nanoplates is based on the Kirchoff plate model, with a linear through the thickness distribution of electric potential. Based on the topology optimization, the largest enhancements in energy harvesting are found for closed circuit boundary conditions, though significant gains are also found for open circuit boundary conditions. Most interestingly, our results demonstrate the competition between surface elasticity, which reduces the energy conversion efficiency, and surface piezoelectricity, which enhances the energy conversion efficiency, in governing the energy harvesting potential of piezoelectric nanostructures.

  11. Nanostructuring of Solar Cell Surfaces

    DEFF Research Database (Denmark)

    Davidsen, Rasmus Schmidt; Schmidt, Michael Stenbæk

    Solar energy is by far the most abundant renewable energy source available, but the levelized cost of solar energy is still not competitive with that of fossil fuels. Therefore there is a need to improve the power conversion effciency of solar cells without adding to the production cost. The main...... objective of this PhD thesis is to develop nanostructured silicon (Si) solar cells with higher power conversion efficiency using only scalable and cost-efficient production methods. The nanostructures, known as 'black silicon', are fabricated by single-step, maskless reactive ion etching and used as front...... and characterized for comparison. Power conversion eciency of 16.5% was obtained for this batch of RIE-textured Si solar cells. The eciency of the KOH-textured reference cell was 17.8%. Quantum Efficiency measurements and carrier loss analysis show that the lower eciency of the RIE-textured cells is primarily due...

  12. Hematite nanostructuring using electrohydrodynamic lithography

    Energy Technology Data Exchange (ETDEWEB)

    Boudoire, Florent [Laboratory for High Performance Ceramics, Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstr. 129, CH-8600 Dübendorf (Switzerland); Department of Chemistry, University of Basel, Spitalstr. 51, CH-4056 Basel (Switzerland); Toth, Rita [Laboratory for High Performance Ceramics, Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstr. 129, CH-8600 Dübendorf (Switzerland); Heier, Jakob [Laboratory for Functional Polymers, Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstr. 129, CH-8600 Dübendorf (Switzerland); Braun, Artur, E-mail: Artur.Braun@alumni.ethz.ch [Laboratory for High Performance Ceramics, Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstr. 129, CH-8600 Dübendorf (Switzerland); Constable, Edwin C. [Department of Chemistry, University of Basel, Spitalstr. 51, CH-4056 Basel (Switzerland)

    2014-06-01

    Tailoring hematite thin film nanostructure is particularly interesting since this oxide's function is closely related to its structure, for example when implemented as a photoanode in water splitting solar cells. In this study, electrohydrodynamic destabilization was designed to grow hematite nanodroplets with morphologies controlled by a master electrode. A polymer/iron salt film was destabilized by electrohydrodynamic destabilization and the resulting structures were pyrolysed to achieve crystalline α-Fe{sub 2}O{sub 3} nanodroplets of 30 nm height and 70 nm radius. NEXAFS spectroscopy proved that the structures contain ferrihydrite, which is converted into hematite during pyrolysis, while the polymer was decomposed. Homogeneous nanoparticle precipitation in the bulk of the polymer, due to encapsulation of the iron precursor in the polymer matrix, is accounted for the good preservation of the structures. This study represents the first step towards the use of electrohydrodynamic destabilization for nanostructuring of hematite thin films, with a control over the feature size.

  13. Nanostructured materials for water desalination

    Energy Technology Data Exchange (ETDEWEB)

    Humplik, T; Lee, J; O' Hern, S C; Fellman, B A; Karnik, R; Wang, E N [Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge (United States); Baig, M A; Hassan, S F; Atieh, M A; Rahman, F; Laoui, T, E-mail: tlaoui@kfupm.edu.sa, E-mail: karnik@mit.edu, E-mail: enwang@mit.edu [Departments of Mechanical Engineering and Chemical Engineering and Research Institute, King Fahd University of Petroleum and Minerals, Dhahran (Saudi Arabia)

    2011-07-22

    Desalination of seawater and brackish water is becoming an increasingly important means to address the scarcity of fresh water resources in the world. Decreasing the energy requirements and infrastructure costs of existing desalination technologies remains a challenge. By enabling the manipulation of matter and control of transport at nanometer length scales, the emergence of nanotechnology offers new opportunities to advance water desalination technologies. This review focuses on nanostructured materials that are directly involved in the separation of water from salt as opposed to mitigating issues such as fouling. We discuss separation mechanisms and novel transport phenomena in materials including zeolites, carbon nanotubes, and graphene with potential applications to reverse osmosis, capacitive deionization, and multi-stage flash, among others. Such nanostructured materials can potentially enable the development of next-generation desalination systems with increased efficiency and capacity. (topical review)

  14. Nanostructured materials for water desalination.

    Science.gov (United States)

    Humplik, T; Lee, J; O'Hern, S C; Fellman, B A; Baig, M A; Hassan, S F; Atieh, M A; Rahman, F; Laoui, T; Karnik, R; Wang, E N

    2011-07-22

    Desalination of seawater and brackish water is becoming an increasingly important means to address the scarcity of fresh water resources in the world. Decreasing the energy requirements and infrastructure costs of existing desalination technologies remains a challenge. By enabling the manipulation of matter and control of transport at nanometer length scales, the emergence of nanotechnology offers new opportunities to advance water desalination technologies. This review focuses on nanostructured materials that are directly involved in the separation of water from salt as opposed to mitigating issues such as fouling. We discuss separation mechanisms and novel transport phenomena in materials including zeolites, carbon nanotubes, and graphene with potential applications to reverse osmosis, capacitive deionization, and multi-stage flash, among others. Such nanostructured materials can potentially enable the development of next-generation desalination systems with increased efficiency and capacity. PMID:21680966

  15. Nanostructured Biomaterials and Their Applications

    Directory of Open Access Journals (Sweden)

    Kirsten Parratt

    2013-05-01

    Full Text Available Some of the most important advances in the life sciences have come from transitioning to thinking of materials and their properties on the nanoscale rather than the macro or even microscale. Improvements in imaging technology have allowed us to see nanofeatures that directly impact chemical and mechanical properties of natural and man-made materials. Now that these can be imaged and quantified, substantial advances have been made in the fields of biomimetics, tissue engineering, and drug delivery. For the first time, scientists can determine the importance of nanograins and nanoasperities in nacre, direct the nucleation of apatite and the growth of cells on nanostructured scaffolds, and pass drugs tethered to nanoparticles through the blood-brain barrier. This review examines some of the most interesting materials whose nanostructure and hierarchical organization have been shown to correlate directly with favorable properties and their resulting applications.

  16. Imaging edges of nanostructured graphene

    DEFF Research Database (Denmark)

    Kling, Jens; Cagliani, Alberto; Booth, T. J.;

    Graphene, as the forefather of 2D-materials, attracts much attention due to its extraordinary properties like transparency, flexibility and outstanding high conductivity, together with a thickness of only one atom. However, graphene also possesses no band gap, which makes it unsuitable for many...... electronic applications like transistors. It has been shown theoretically that by nanostructuring pristine graphene, e.g. with regular holes, the electronic properties can be tuned and a band gap introduced. The size, distance and edge termination of these “defects” influence the adaptability....... Such nanostructuring can be done experimentally, but especially characterization at atomic level is a huge challenge. High-resolution TEM (HRTEM) is used to characterize the atomic structure of graphene. We optimized the imaging conditions used for the FEI Titan ETEM. To reduce the knock-on damage of the carbon atoms...

  17. Sintering and ripening resistant noble metal nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    van Swol, Frank B; Song, Yujiang; Shelnutt, John A; Miller, James E; Challa, Sivakumar R

    2013-09-24

    Durable porous metal nanostructures comprising thin metal nanosheets that are metastable under some conditions that commonly produce rapid reduction in surface area due to sintering and/or Ostwald ripening. The invention further comprises the method for making such durable porous metal nanostructures. Durable, high-surface area nanostructures result from the formation of persistent durable holes or pores in metal nanosheets formed from dendritic nanosheets.

  18. Metal chalcogenide nanostructures for renewable energy applications

    CERN Document Server

    Qurashi, Ahsanulhaq

    2014-01-01

    This first ever reference book that focuses on metal chalcogenide semiconductor nanostructures for renewable energy applications encapsulates the state-of-the-art in multidisciplinary research on the metal chalcogenide semiconductor nanostructures (nanocrystals, nanoparticles, nanorods, nanowires,  nanobelts, nanoflowers, nanoribbons and more).  The properties and synthesis of a class of nanomaterials is essential to renewable energy manufacturing and this book focuses on the synthesis of metal chalcogendie nanostructures, their growth mechanism, optical, electrical, and other important prop

  19. Advances in CZTS thin films and nanostructured

    Science.gov (United States)

    Ali, N.; Ahmed, R.; Bakhtiar-Ul-Haq; Shaari, A.

    2015-06-01

    Already published data for the optical band gap (Eg) of thin films and nanostructured copper zinc tin sulphide (CZTS) have been reviewed and combined. The vacuum (physical) and non-vacuum (chemical) processes are focused in the study for band gap comparison. The results are accumulated for thin films and nanostructured in different tables. It is inferred from the re- view that the nanostructured material has plenty of worth by engineering the band gap for capturing the maximum photons from solar spectrum.

  20. Nanostructured Substrates for Optical Sensing

    OpenAIRE

    Kemling, Jonathan W.; Qavi, Abraham J.; Bailey, Ryan C.; Suslick, Kenneth S.

    2011-01-01

    Sensors that change color have the advantages of versatility, ease of use, high sensitivity, and low cost. The recent development of optically based chemical sensing platforms has increasingly employed substrates manufactured with advanced processing or fabrication techniques to provide precise control over shape and morphology of the sensor micro- and nano-structure. New sensors have resulted with improved capabilities for a number of sensing applications, including the detection of biomolec...

  1. NANOSTRUCTURES FOR THERAPY AND DIAGNOSIS

    OpenAIRE

    Aruta, Rosaria

    2015-01-01

    The preparation of Nanostructures of desired shape, composition and with tailored properties is of wide scientific and technological interest. Indeed, a variety of nanoparticle architectures have been proposed as nanocarriers, these include liposomes, quantum dots (QD), gold-nanoshells, mesoporous materials, micelles, magnetic nanoparticles, dendrimers, and Carbon Nanotubes (CNTs) as so as several materials have been studied for use in active agents targeting. Among them, as asserted by diffe...

  2. Quantum rotor in nanostructured superconductors

    OpenAIRE

    Lin, Shi-Hsin; Milošević, M. V.; Covaci, L.; Jankó, B.; Peeters, F.M.

    2014-01-01

    Despite its apparent simplicity, the idealized model of a particle constrained to move on a circle has intriguing dynamic properties and immediate experimental relevance. While a rotor is rather easy to set up classically, the quantum regime is harder to realize and investigate. Here we demonstrate that the quantum dynamics of quasiparticles in certain classes of nanostructured superconductors can be mapped onto a quantum rotor. Furthermore, we provide a straightforward experimental procedure...

  3. Hydrogen storage in nanotubes & nanostructures

    OpenAIRE

    Froudakis, George E.

    2011-01-01

    Over the last several years, a significant share of the scientific community has focused its attention on the hydrogen storage problem. Since 1997, when carbon nanotubes appeared to be a promising storage material, many theoretical and experimental groups have investigated the hydrogen storage capacity of these carbon nanostructures. These efforts were not always successful and consequently, the results obtained were often controversial. In the current review we attempt to summarize some the ...

  4. Insulating oxide surfaces and nanostructures

    Science.gov (United States)

    Goniakowski, Jacek; Noguera, Claudine

    2016-03-01

    This contribution describes some peculiarities of the science of oxide surfaces and nanostructures and proposes a simple conceptual scheme to understand their electronic structure, in the spirit of Jacques Friedel's work. Major results on the effects of non-stoichiometry and polarity are presented, for both semi-infinite surfaces and ultra-thin films, and promising lines of research for the near future are sketched. xml:lang="fr"

  5. Thermoelectric effects in graphene nanostructures

    International Nuclear Information System (INIS)

    The thermoelectric properties of graphene and graphene nanostructures have recently attracted significant attention from the physics and engineering communities. In fundamental physics, the analysis of Seebeck and Nernst effects is very useful in elucidating some details of the electronic band structure of graphene that cannot be probed by conductance measurements alone, due in particular to the ambipolar nature of this gapless material. For applications in thermoelectric energy conversion, graphene has two major disadvantages. It is gapless, which leads to a small Seebeck coefficient due to the opposite contributions of electrons and holes, and it is an excellent thermal conductor. The thermoelectric figure of merit ZT of a two-dimensional (2D) graphene sheet is thus very limited. However, many works have demonstrated recently that appropriate nanostructuring and bandgap engineering of graphene can concomitantly strongly reduce the lattice thermal conductance and enhance the Seebeck coefficient without dramatically degrading the electronic conductance. Hence, in various graphene nanostructures, ZT has been predicted to be high enough to make them attractive for energy conversion. In this article, we review the main results obtained experimentally and theoretically on the thermoelectric properties of graphene and its nanostructures, emphasizing the physical effects that govern these properties. Beyond pure graphene structures, we discuss also the thermoelectric properties of some hybrid graphene structures, as graphane, layered carbon allotropes such as graphynes and graphdiynes, and graphene/hexagonal boron nitride heterostructures which offer new opportunities. Finally, we briefly review the recent activities on other atomically thin 2D semiconductors with finite bandgap, i.e. dichalcogenides and phosphorene, which have attracted great attention for various kinds of applications, including thermoelectrics. (topical review)

  6. Photoinduced magnetic force between nanostructures

    Science.gov (United States)

    Guclu, Caner; Tamma, Venkata Ananth; Wickramasinghe, Hemantha Kumar; Capolino, Filippo

    2015-12-01

    Photoinduced magnetic force between nanostructures, at optical frequencies, is investigated theoretically. Till now optical magnetic effects were not used in scanning probe microscopy because of the vanishing natural magnetism with increasing frequency. On the other hand, artificial magnetism in engineered nanostructures led to the development of measurable optical magnetism. Here two examples of nanoprobes that are able to generate strong magnetic dipolar fields at optical frequency are investigated: first, an ideal magnetically polarizable nanosphere and then a circular cluster of silver nanospheres that has a looplike collective plasmonic resonance equivalent to a magnetic dipole. Magnetic forces are evaluated based on nanostructure polarizabilities, i.e., induced magnetic dipoles, and magnetic-near field evaluations. As an initial assessment on the possibility of a magnetic nanoprobe to detect magnetic forces, we consider two identical magnetically polarizable nanoprobes and observe magnetic forces on the order of piconewtons, thereby bringing it within detection limits of conventional atomic force microscopes at ambient pressure and temperature. The detection of magnetic force is a promising method in studying optical magnetic transitions that can be the basis of innovative spectroscopy applications.

  7. Nonlinear spectroscopy of nanostructured materials

    International Nuclear Information System (INIS)

    Full text: Nanostructured materials present optical properties that are generally different from the corresponding bulk materials because of quantum phenomena and dielectric confinement effects. Presently a large variety of photonic materials is available and some of their properties can be controlled in the nanoscale. For instance, the appropriate modification of materials allows the change of their phonon density of states, the control of the electron dynamics as well as enhancement of energy transfer processes among luminophores embedded in a host medium. Our approach to this area is based on the exploitation of nonlinear (NL) optical techniques to investigate different composites. In this communication recent experiments performed at Recife with nanostructured systems will be reported. Particular emphasis will be given to processes related to NL refraction, NL absorption and NL light scattering. Experiments based on the use of lasers with pulse duration in the nano-, pico- and femto-second range will be described. Measurements of the NL optical response will be presented for colloids containing metallic or dielectric nanocrystals, luminescent ceramics containing metallic nanoparticles and polymers with silver nanostructures. The optical response of the materials is controlled changing the nanoparticles filling fraction. The materials investigated exhibit properties that make them useful for devices such as optical sensors, random lasers, optical limiters and all-optical switches

  8. Nanostructures for Electronic and Sensing Applications Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed project will develop sensors and electronic components from metal oxide based nanotubes and nanowires. These nanostructured materials will be grown...

  9. Is there a shift to 'active nanostructures'?

    International Nuclear Information System (INIS)

    It has been suggested that an important transition in the long-run trajectory of nanotechnology development is a shift from passive to active nanostructures. Such a shift could present different or increased societal impacts and require new approaches for risk assessment. An active nanostructure 'changes or evolves its state during its operation,' according to the National Science Foundation's (2006) Active Nanostructures and Nanosystems grant solicitation. Active nanostructure examples include nanoelectromechanical systems (NEMS), nanomachines, self-healing materials, targeted drugs and chemicals, energy storage devices, and sensors. This article considers two questions: (a) Is there a 'shift' to active nanostructures? (b) How can we characterize the prototypical areas into which active nanostructures may emerge? We build upon the NSF definition of active nanostructures to develop a research publication search strategy, with a particular intent to distinguish between passive and active nanotechnologies. We perform bibliometric analyses and describe the main publication trends from 1995 to 2008. We then describe the prototypes of research that emerge based on reading the abstracts and review papers encountered in our search. Preliminary results suggest that there is a sharp rise in active nanostructures publications in 2006, and this rise is maintained in 2007 and through to early 2008. We present a typology that can be used to describe the kind of active nanostructures that may be commercialized and regulated in the future.

  10. Anchored nanostructure materials and method of fabrication

    Science.gov (United States)

    Seals, Roland D; Menchhofer, Paul A; Howe, Jane Y; Wang, Wei

    2012-11-27

    Anchored nanostructure materials and methods for their fabrication are described. The anchored nanostructure materials may utilize nano-catalysts that include powder-based or solid-based support materials. The support material may comprise metal, such as NiAl, ceramic, a cermet, or silicon or other metalloid. Typically, nanoparticles are disposed adjacent a surface of the support material. Nanostructures may be formed as anchored to nanoparticles that are adjacent the surface of the support material by heating the nano-catalysts and then exposing the nano-catalysts to an organic vapor. The nanostructures are typically single wall or multi-wall carbon nanotubes.

  11. Nanostructured Catalytic Reactors for Air Purification Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR Phase II project proposes the development of lightweight compact nanostructured catalytic reactors for air purification from toxic gaseous organic...

  12. Nanostructured Catalytic Reactors for Air Purification Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR Phase I project proposes the development of lightweight compact nanostructured catalytic reactors for air purification from toxic gaseous organic...

  13. Tribological properties, corrosion resistance and biocompatibility of magnetron sputtered titanium-amorphous carbon coatings

    Science.gov (United States)

    Dhandapani, Vishnu Shankar; Subbiah, Ramesh; Thangavel, Elangovan; Arumugam, Madhankumar; Park, Kwideok; Gasem, Zuhair M.; Veeraragavan, Veeravazhuthi; Kim, Dae-Eun

    2016-05-01

    Amorphous carbon incorporated with titanium (a-C:Ti) was coated on 316L stainless steel (SS) by magnetron sputtering technique to attain superior tribological properties, corrosion resistance and biocompatibility. The morphology, topography and functional groups of the nanostructured a-C:Ti coatings in various concentrations were analyzed using atomic force microscopy (AFM), Raman, X-Ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Raman and XPS analyses confirmed the increase in sp2 bonds with increasing titanium content in the a-C matrix. TEM analysis confirmed the composite nature of the coating and the presence of nanostructured TiC for Ti content of 2.33 at.%. This coating showed superior tribological properties compared to the other a-C:Ti coatings. Furthermore, electrochemical corrosion studies were performed against stimulated body fluid medium in which all the a-C:Ti coatings showed improved corrosion resistance than the pure a-C coating. Preosteoblasts proliferation and viability on the specimens were tested and the results showed that a-C:Ti coatings with relatively high Ti (3.77 at.%) content had better biocompatibility. Based on the results of this work, highly durable coatings with good biocompatibility could be achieved by incorporation of optimum amount of Ti in a-C coatings deposited on SS by magnetron sputtering technique.

  14. Amorphous to crystalline phase transition in pulsed laser deposited silicon carbide

    International Nuclear Information System (INIS)

    SiC thin films were grown on Si (1 0 0) substrates by excimer laser ablation of a SiC target in vacuum. The effect of deposition temperature (up to 950 deg. C), post-deposition annealing and laser energy on the nanostructure, bonding and crystalline properties of the films was studied, in order to elucidate their transition from an amorphous to a crystalline phase. Infra-red spectroscopy shows that growth at temperatures greater than 600 deg. C produces layers with increasingly uniform environment of the Si-C bonds, while the appearance of large crystallites is detected, by X-ray diffraction, at 800 deg. C. Electron paramagnetic resonance confirms the presence of clustered paramagnetic centers within the sp2 carbon domains. Increasing deposition temperature leads to a decrease of the spin density and to a temperature-dependent component of the EPR linewidth induced by spin hopping. For films grown below 650 deg. C, post-deposition annealing at 1100 deg. C reduces the spin density as a result of a more uniform Si-C nanostructure, though large scale crystallization is not observed. For greater deposition temperatures, annealing leads to little changes in the bonding properties, but suppresses the temperature dependent component of the EPR linewidth. These findings are explained by a relaxation of the stress in the layers, through the annealing of the bond angle disorder that inhibits spin hopping processes

  15. Nanostructural activated carbons for hydrogen storage

    Science.gov (United States)

    Li, Suoding

    A series of nanostructured activated carbons have been synthesized from poly(ether ether ketone) (PEEK), and its derivatives. These carbons, with surface area exceeding 3000 m2/g and with average pore diameters of ≤ 20 A, are proven to be superior hydrogen storage materials, with hydrogen storage capacities up to 5.5 wt% at 77 K and 45 atm. The porous texture of these carbons was controlled via optimizing three synthetic steps: thermo-oxidation of PEEK in air, pyrolysis or carbonization of the oxidized PEEK in an inert atmosphere, and activation of the pre-carbonized PEEK with metal hydroxide. Thermo-oxidation of PEEK and carbonization process were thoroughly studied. These processes have been investigated by MDSC, FTIR, TGA and Py-MS. The pyrolysis or carbonization of PEEK involves the degradation of PEEK chains in three stages. Carbon morphology, including crystallinity and porous texture, is readily controlled by adjusting carbonization temperature. Activation of PEEK carbons, using inorganic bases and other activation agents, produces microporous carbons having a very narrow pore size distribution and an average pore diameter of ≤ 20 A. The activation control parameters including activation agent, activation temperature, time and carbon morphology have been investigated extensively. High surface area activated carbon is obtained by activating a highly amorphous carbon with a high activation agent/carbon ratio at 800°C. Theoretical calculations show that the pores with smaller diameter, especially smaller than 7 A, favor hydrogen adsorption. The experimental results confirm this fact and show that: (1) the hydrogen adsorption capacity per unit surface area at 77 K and 1 bar is larger in the smaller pores, (2) gravimetric hydrogen storage capacity (W(H2)) is directly proportional to the ultramicropore (< 7 A) volume; and (3) the volumetric hydrogen storage capacity is directly proportional to the volume fraction of ultramicropores in carbon. Hydrogen

  16. Direct growth of single-crystalline III-V semiconductors on amorphous substrates.

    Science.gov (United States)

    Chen, Kevin; Kapadia, Rehan; Harker, Audrey; Desai, Sujay; Seuk Kang, Jeong; Chuang, Steven; Tosun, Mahmut; Sutter-Fella, Carolin M; Tsang, Michael; Zeng, Yuping; Kiriya, Daisuke; Hazra, Jubin; Madhvapathy, Surabhi Rao; Hettick, Mark; Chen, Yu-Ze; Mastandrea, James; Amani, Matin; Cabrini, Stefano; Chueh, Yu-Lun; Ager Iii, Joel W; Chrzan, Daryl C; Javey, Ali

    2016-01-01

    The III-V compound semiconductors exhibit superb electronic and optoelectronic properties. Traditionally, closely lattice-matched epitaxial substrates have been required for the growth of high-quality single-crystal III-V thin films and patterned microstructures. To remove this materials constraint, here we introduce a growth mode that enables direct writing of single-crystalline III-V's on amorphous substrates, thus further expanding their utility for various applications. The process utilizes templated liquid-phase crystal growth that results in user-tunable, patterned micro and nanostructures of single-crystalline III-V's of up to tens of micrometres in lateral dimensions. InP is chosen as a model material system owing to its technological importance. The patterned InP single crystals are configured as high-performance transistors and photodetectors directly on amorphous SiO2 growth substrates, with performance matching state-of-the-art epitaxially grown devices. The work presents an important advance towards universal integration of III-V's on application-specific substrates by direct growth. PMID:26813257

  17. Amorphous Ge quantum dots embedded in crystalline Si: ab initio results

    International Nuclear Information System (INIS)

    We study amorphous Ge quantum dots embedded in a crystalline Si matrix through structure modeling and simulation using ab initio density functional theory including spin–orbit interaction and quasiparticle effects. Three models are generated by replacing a spherical region within diamond Si by Ge atoms and creating a disordered bond network with appropriate density inside the Ge quantum dot. After total-energy optimisations of the atomic geometry we compute the electronic and optical properties. We find three major effects: (i) the resulting nanostructures adopt a type-I heterostructure character; (ii) the lowest optical transitions occur only within the Ge quantum dots, and do not involve or cross the Ge–Si interface. (iii) for larger amorphous Ge quantum dots, with diameters of about 2.0 and 2.7 nm, absorption peaks appear in the mid-infrared spectral region. These are promising candidates for intense luminescence at photon energies below the gap energy of bulk Ge. (paper)

  18. Direct growth of single-crystalline III-V semiconductors on amorphous substrates

    Science.gov (United States)

    Chen, Kevin; Kapadia, Rehan; Harker, Audrey; Desai, Sujay; Seuk Kang, Jeong; Chuang, Steven; Tosun, Mahmut; Sutter-Fella, Carolin M.; Tsang, Michael; Zeng, Yuping; Kiriya, Daisuke; Hazra, Jubin; Madhvapathy, Surabhi Rao; Hettick, Mark; Chen, Yu-Ze; Mastandrea, James; Amani, Matin; Cabrini, Stefano; Chueh, Yu-Lun; Ager, Joel W., III; Chrzan, Daryl C.; Javey, Ali

    2016-01-01

    The III-V compound semiconductors exhibit superb electronic and optoelectronic properties. Traditionally, closely lattice-matched epitaxial substrates have been required for the growth of high-quality single-crystal III-V thin films and patterned microstructures. To remove this materials constraint, here we introduce a growth mode that enables direct writing of single-crystalline III-V's on amorphous substrates, thus further expanding their utility for various applications. The process utilizes templated liquid-phase crystal growth that results in user-tunable, patterned micro and nanostructures of single-crystalline III-V's of up to tens of micrometres in lateral dimensions. InP is chosen as a model material system owing to its technological importance. The patterned InP single crystals are configured as high-performance transistors and photodetectors directly on amorphous SiO2 growth substrates, with performance matching state-of-the-art epitaxially grown devices. The work presents an important advance towards universal integration of III-V's on application-specific substrates by direct growth.

  19. Carbon-assisted growth and high visible-light optical reflectivity of amorphous silicon oxynitride nanowires

    Directory of Open Access Journals (Sweden)

    Tang Zirong

    2011-01-01

    Full Text Available Abstract Large amounts of amorphous silicon oxynitride nanowires have been synthesized on silicon wafer through carbon-assisted vapor-solid growth avoiding the contamination from metallic catalysts. These nanowires have the length of up to 100 μm, with a diameter ranging from 50 to 150 nm. Around 3-nm-sized nanostructures are observed to be homogeneously distributed within a nanowire cross-section matrix. The unique configuration might determine the growth of ternary amorphous structure and its special splitting behavior. Optical properties of the nanowires have also been investigated. The obtained nanowires were attractive for their exceptional whiteness, perceived brightness, and optical brilliance. These nanowires display greatly enhanced reflection over the whole visible wavelength, with more than 80% of light reflected on most of the wavelength ranging from 400 to 700 nm and the lowest reflectivity exceeding 70%, exhibiting performance superior to that of the reported white beetle. Intense visible photoluminescence is also observed over a broad spectrum ranging from 320 to 500 nm with two shoulders centered at around 444 and 468 nm, respectively.

  20. AMORPHOUS MATTER IN KAOLINS AND ITS GEOLOGICAL IMPLICATIONS

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Selective dissolution with ammonium oxalate was carried out toextract amorphous matter in some kaolins from China.Ammonium oxalate extraction is an effective method to extract amorphous constituents without destroying the kaolinite crystalline structure.The study showed that,absolute amounts of amorphous constituents in kaolins are in the order Al>Si>Fe,but that relative amounts are in the order Fe>Al>Si.The amorphous phases are probably mainly in the form of separate particles,or colloidal particles absorbed on the surface of kaolinite particles.Compared to older kaolins,younger kaolins contain much more amorphous iron content.

  1. Synthesis, characterization, and properties of low-dimensional nanostructured materials

    Science.gov (United States)

    Hu, Xianluo

    2007-05-01

    Nanometer scale structures represent an exciting and rapidly expanding area of research. Studies on new physical/chemical properties and applications of nanomaterials and nanostructures are possible only when nanostructured materials are made available with desired size, morphology, crystal and microstructure, and composition. Thus, controlled synthesis of nanomaterials is the essential aspect of nanotechnology. This thesis describes the development of simple and versatile solution-based approaches to synthesize low-dimensional nanostructures. The first major goal of this research is to design and fabricate morphology-controlled alpha-Fe 2O3 nanoarchitectures in aqueous solution through a programmed microwave-assisted hydrothermal route, taking advantage of microwave irradiation and hydrothermal effects. Free-standing alpha-Fe2O3 nanorings are prepared by hydrolysis of FeCl3 in the presence of phosphate ions. The as-formed architecture of alpha-Fe2O 3 nanorings is an exciting new member in the family of iron oxide nanostructures. Our preliminary results demonstrate that sensors made of the alpha-Fe 2O3 nanorings exhibit high sensitivity not only for bio-sensing of hydrogen peroxide in a physiological solution but also for gas-sensing of alcohol vapor at room temperature. Moreover, monodisperse alpha-Fe 2O3 nanocrystals with continuous aspect-ratio tuning and fine shape control are achieved by controlling the experimental conditions. The as-formed alpha-Fe2O3 exhibits shape-dependent infrared optical properties. The growth process of colloidal alpha-Fe 2O3 crystals in the presence of phosphate ions is discussed. In addition, through an efficient microwave-assisted hydrothermal process, self-assembled hierarchical alpha-Fe2O3 nanoarchitectures are synthesized on a large scale. The second major goal of this research is to develop convenient microwave-hydrothermal approaches for the fabrication of carbon-based nanocomposites: (1) A one-pot solution-phase route, namely

  2. Effect of lamellar nanostructures on the second harmonic generation of polymethylmethacrylate films doped with 4-(4-nitrophenylazo)aniline chromophores

    CERN Document Server

    Franco, Alfredo; Valverde-Aguilar, Guadalupe; García-Macedo, Jorge; Brusatin, Giovanna; Guglielmi, Massimo

    2011-01-01

    The kinetics of the orientation of Disperse Orange 3 molecules embedded in amorphous and nanostructured Polymethylmethacrylate films was studied under the effect of an intense electrostatic poling field. Non-centrosymmetric chromophore distributions were obtained in Polymethylmethacrylate films by Corona poling technique. These distributions depends on the Corona poling time. The changes in the orientation of the Disperse Orange 3 molecules were followed by in-situ transmitted Second Harmonic Generation measurements. The Second Harmonic Generation signal was recorded as function of time at several temperatures; it was fitted as function of the Corona poling time, considering matrix-chromophore interactions. The Polymethylmethacrylate films were nanostructured by the incorporation of an anionic surfactant, the Sodium Dodecyl Sulfate. The lamellar nanostructures in the films were identified by X-ray diffraction measurements.

  3. Zinc oxide nanostructures and nanoengineering

    Science.gov (United States)

    Banerjee, Debasish

    ZnO is a large band-gap (3.37 eV) semiconductor, a potentially important material for numerous optoelectronic applications. Nanostructures, by definition are the structures having at least one dimension between 1--100 nm. In this thesis we will investigate a brief account of the strategies to grow ZnO nanostructures. Since invariably nanomaterial properties tend to change significantly during scale-up from development on limited volume equipment. Goal of this study is to demonstrate a practical technique which is able to synthesize large quantities of nanowires while keeping the unique properties of nano-sized materials. Using ZnO as an example, we discussed a strategy to produce nanowires in gram quantity. Ability to define position, size, and density of nanostructures on surfaces enable detailed studies of the properties of individual sites as well as collective properties of the assembly. These periodic structures are usually manufactured using electron beam lithography, photolithography, or x-ray lithography techniques. These methods allow fabrication of nanostructures and provide highly reproducible results. However, they are mostly not scalable to large areas, and are limited by a multistage, time-consuming, and expensive preparation procedure. We described an unique technique combining nanosphere self-assembly lithography and vapor-liquid-solid (VLS) approach of fabricating periodic array of catalyst dots in various geometry and subsequently grow vertically aligned ZnO nanowires in a large area hoping to achieve enhanced ultraviolet lasing and many other photonic devices. ZnO being a transparent conducting oxide, the fabrication of ZnO field emitters can be easily integrated with ITO and ZnO thin film fabrication process. Thus a low cost solution for fabrication of field emission display can be realized using ZnO nanowires as field emitters. There have been several demonstrations of using ZnO nanowires as field emitters. However no significant improvement in

  4. Amorphous Silica- and Carbon- rich nano-templated surfaces as model interstellar dust surfaces for laboratory astrochemistry

    Science.gov (United States)

    Pascual, Natalia; Dawes, Anita; González-Posada, Fernando; Thompson, Neil; Chakarov, Dinko; Mason, Nigel J.; Fraser, Helen Jane

    2015-08-01

    Experimental studies on surface astrochemistry are vital to our understanding of chemical evolution in the interstellar medium (ISM). Laboratory surface-astrochemists have recently begun to study chemical reactions on interstellar dust-grain mimics, ranging from graphite, HOPG and graphene (representative of PAHs or large C-grains in the ISM) to amorphous olivine (representative of silicate dust) and ablated meteoritic samples (representative of interplanetary dust). These pioneering experiments show that the nature of the surface fundamentally affects processes at the substrate surface, substrate-ice interface, and ice over-layer. What these experiments are still lacking is the ability to account for effects arising from the discrete nano-scale of ISM grains, which might include changes to electronic structure, optical properties and surface-kinetics in comparison to bulk materials. The question arises: to what extent are the chemical and optical properties of interstellar ices affected by the size, morphology and material of the underlying ISM dust?We have designed, fabricated and characterised a set of nano-structured surfaces, where nanoparticles, representative of ISM grains, are adhered to an underlying support substrate. Here we will show the nanoparticles that have been manufactured from fused-silica (FS), glassy carbon (GC) and amorphous-C (aC). Our optical characterisation data shows that the nanostructured surfaces have different absorption cross-sections and significant scattering in comparison to the support substrates, which has implications for the energetic processing of icy ISM dust. We have been able to study how water-ice growth differs on the nanoparticles in comparison to the “flat” substrates, indicating increased ice amorphicity when nanoparticles are present, and on C-rich surfaces, compared to Si-rich particles. These data will be discussed in the context of interstellar water-ice features.

  5. Characterization of Poly-Amorphous Indomethacin by Terahertz Spectroscopy

    Science.gov (United States)

    Otsuka, Makoto; Nishizawa, Jun-ichi; Fukura, Naomi; Sasaki, Tetsuo

    2012-09-01

    Since the stability of amorphous solids of pharmaceuticals differs depending on the method of preparation, there are several solid-state chemical structures in amorphous solids, which like poly-amorphous solids might have different characteristics the same as in crystalline solids. However, it is not easy to identify the differences in solid-state characteristics between amorphous solids using conventional analytical methods, such as powder X-ray diffraction analysis, since all of the poly-amorphous solids had similar halo X-ray diffraction patterns. However, terahertz spectroscopy can distinguish the amorphous solids of indomethacin with different physicochemical properties, and is expected to provide a rapid and non-destructive qualitative analysis for the solid materials, it would be useful for the qualitative evaluation of amorphous solids in the pharmaceutical industry.

  6. Amorphous-crystalline transition in thermoelectric NbO2

    International Nuclear Information System (INIS)

    Density functional theory was employed to design enhanced amorphous NbO2 thermoelectrics. The covalent-ionic nature of Nb–O bonding is identical in amorphous NbO2 and its crystalline counterpart. However, the Anderson localisation occurs in amorphous NbO2, which may affect the transport properties. We calculate a multifold increase in the absolute Seebeck coefficient for the amorphous state. These predictions were critically appraised by measuring the Seebeck coefficient of sputtered amorphous and crystalline NbO2 thin films with the identical short-range order. The first-order phase transition occurs at approximately 550 °C, but amorphous NbO2 possesses enhanced transport properties at all temperatures. Amorphous NbO2, reaching  −173 μV K−1, exhibits up to a 29% larger absolute Seebeck coefficient value, thereby validating the predictions. (paper)

  7. Atomic-scale disproportionation in amorphous silicon monoxide.

    Science.gov (United States)

    Hirata, Akihiko; Kohara, Shinji; Asada, Toshihiro; Arao, Masazumi; Yogi, Chihiro; Imai, Hideto; Tan, Yongwen; Fujita, Takeshi; Chen, Mingwei

    2016-01-01

    Solid silicon monoxide is an amorphous material which has been commercialized for many functional applications. However, the amorphous structure of silicon monoxide is a long-standing question because of the uncommon valence state of silicon in the oxide. It has been deduced that amorphous silicon monoxide undergoes an unusual disproportionation by forming silicon- and silicon-dioxide-like regions. Nevertheless, the direct experimental observation is still missing. Here we report the amorphous structure characterized by angstrom-beam electron diffraction, supplemented by synchrotron X-ray scattering and computer simulations. In addition to the theoretically predicted amorphous silicon and silicon-dioxide clusters, suboxide-type tetrahedral coordinates are detected by angstrom-beam electron diffraction at silicon/silicon-dioxide interfaces, which provides compelling experimental evidence on the atomic-scale disproportionation of amorphous silicon monoxide. Eventually we develop a heterostructure model of the disproportionated silicon monoxide which well explains the distinctive structure and properties of the amorphous material. PMID:27172815

  8. Atomic-scale disproportionation in amorphous silicon monoxide

    Science.gov (United States)

    Hirata, Akihiko; Kohara, Shinji; Asada, Toshihiro; Arao, Masazumi; Yogi, Chihiro; Imai, Hideto; Tan, Yongwen; Fujita, Takeshi; Chen, Mingwei

    2016-01-01

    Solid silicon monoxide is an amorphous material which has been commercialized for many functional applications. However, the amorphous structure of silicon monoxide is a long-standing question because of the uncommon valence state of silicon in the oxide. It has been deduced that amorphous silicon monoxide undergoes an unusual disproportionation by forming silicon- and silicon-dioxide-like regions. Nevertheless, the direct experimental observation is still missing. Here we report the amorphous structure characterized by angstrom-beam electron diffraction, supplemented by synchrotron X-ray scattering and computer simulations. In addition to the theoretically predicted amorphous silicon and silicon-dioxide clusters, suboxide-type tetrahedral coordinates are detected by angstrom-beam electron diffraction at silicon/silicon-dioxide interfaces, which provides compelling experimental evidence on the atomic-scale disproportionation of amorphous silicon monoxide. Eventually we develop a heterostructure model of the disproportionated silicon monoxide which well explains the distinctive structure and properties of the amorphous material. PMID:27172815

  9. Ion beam irradiation of relaxed amorphous silicon carbide

    International Nuclear Information System (INIS)

    In-situ transmittance measurements at λ=633 nm are used during ion irradiation to probe the defect generation in relaxed amorphous silicon carbide (SiC). The optical constants of amorphous SiC are strongly correlated to the thermal history of the material and the transmittance of ion implanted amorphous SiC (unrelaxed amorphous) increases after annealing in the temperature range 100-700 deg. C. The transmittance of annealed amorphous SiC (relaxed) during subsequent implantation decreases and saturates to the value of unrelaxed amorphous. In-situ transmittance measurements allow to follow directly the defect generation and to measure the fluence at which the transmittance saturates (derelaxation fluence). The effect of different ions (He and Ar) on these phenomena is explored. The obtained results are compared and discussed with similar measurements performed on amorphous silicon

  10. CdSe/ZnSe heteroepitaxy: Aspects of growth and self organization of nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Mahapatra, S.; Kiessling, T.; Astakhov, G.V.; Bass, U.; Schmitt, F.; Schumacher, C.; Ossau, W.; Geurts, J.; Molenkamp, L.W.; Brunner, K. [Universitaet Wuerzburg, Physikalisches Institut, EP3, Am Hubland, 97074 Wuerzburg (Germany); Margapoti, E.; Renner, J.; Schmidt, T.; Worschech, L.; Forchel, A. [Universitaet Wuerzburg, Physikalisches Institut, Technische Physik, Am Hubland, 97074 Wuerzburg (Germany); Bougerol, C. [CEA-CNRS NPSC, SP2M/DRFMC/CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble cedex (France); Bendounan, A.; Reinert, F. [Universitaet Wuerzburg, Physikalisches Institut, EP2, Am Hubland, 97074 Wuerzburg (Germany)

    2007-07-01

    Formation and properties of quantum dots (QDs) and related nanostructures by conventional molecular beam epitaxy (MBE) and two other variants of the technique, have been systematically investigated. While MBE growth of CdSe on ZnSe at 300 C results in the formation of rough CdSe quantum-well-like structures, by one of the variants, which combines epitaxial growth of a CdSe layer at 230 C and subsequent in-situ annealing at 310-340 C, tiny but distinct three-dimensional (3D) QDs are formed. We demonstrate that QD formation by this method, developed originally by Rabe et al. (J. Cryst. Growth 184/185, 248 (1998) [30]), essentially takes place during the annealing step, by a process of ''controlled roughening'' of the as-grown quasi-two-dimensional (2D) CdSe layer. In comparison to conventional MBE, this process results in reduction of the areal density of the self-organized QDs by up to two orders of magnitude, thus making them distinctly discernible. In the second variant technique, similar to that applied originally for the self-organization of CdTe/ZnTe quantum dots by Tinjod et al. (Appl. Phys. Lett. 82, 4340 (2003)), QD-formation takes place as a result of deposition of an amorphous group-VI layer onto a strained 2D CdSe layer at {proportional_to}50 C, and its subsequent re-desorption at temperatures of 280-320 C. While deposition and desorption of amorphous Se leads to the formation of large isolated QDs, we show that use of amorphous Te results in the self-assembly and ordering of a rich variety of nanostructures. Luminescence, morphology, and composition of QDs and the underlying formation mechanism of the three processes are discussed in detail. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Role of Amorphous Manganese Oxide in Nitrogen Loss

    Institute of Scientific and Technical Information of China (English)

    LILIANG-MO; WUQI-TU

    1991-01-01

    Studies have been made,by 15N-tracer technique on nitrogen loss resulting from adding amorphous manganese oxide to NH4+-N medium under anaerobic conditions.The fact that the total nitrogen recovery was decreased and that 15NO2,15N2O,15N14NO,15NO,15N2 and 15N14N were emitted has proved that,like amorphous iron oxide,amorphous manganese oxide can also act as an electron acceptor in the oxidation of NH4+-N under anaerobic conditions and give rise to nitrogen loss.This once again illustrates another mechanism by which the loss of ammonium nitrogen in paddy soils is brought about by amorphous iron and manganese oxides.The quantity of nitrogen loss by amorphous manganese oxide increased with an increase in the amount of amorphous manganese oxide added and lessened with time of its aging.The nitrogen loss resulting from amorphous manganese oxide was less than that from amorphous iron oxide.And the nitrogen loss resulting from amorphous manganese oxide was less than that from amorphous iron oxide.And the nitrogen loss by cooperation of amorphous manganese oxide and microorganisms (soil suspension) was larger than that by amorphous manganese oxide alone.In the system,nitrogen loss was associated with the specific surface ares and oxidation-reduction of amorphous manganese oxide.However,their quantitative relationship and the exact reaction processes of nitrogen loss induced by amorphous manganese oxide remain to be further studied.

  12. Iso- and variothermal injection compression moulding of polymer micro- and nanostructures for optical and medical applications

    International Nuclear Information System (INIS)

    The surfaces of medical and optical polymer products are being increasingly functionalized with micro- and nanostructures using mass replication methods like injection moulding. We compared the filling behaviour and replication quality of such structures using four different moulding processes with two polymers of different viscosity and wetting behaviour. For this purpose, we replicated three representative 2D and 3D micro- and nanostructures into polymethylmethacrylate and amorphous polyamide by isothermal and variothermal injection moulding with and without compression, respectively, using the same mould. The parallel compression phase reduced the internal pressure in the cavity, leading to fewer demoulding issues but without significant influence on the replication fidelity. Variothermal heating of the mould in combination with a polymer of low viscosity and good wetting behaviour was favourable especially for filling of high aspect-ratio structures. For microstructure replication, melt viscosity and no-flow temperature were clearly more relevant than wetting as flow resistance and frozen layer formation are the main reasons for incomplete filling at this length scale. In nanostructures, the capillary effect becomes increasingly dominant depending on the surface energy of the polymer. (paper)

  13. Gradation of Nanostructures in Cold-Rolled and Annealed Ti-Ni Shape Memory Alloys

    Science.gov (United States)

    Prokoshkin, S.; Brailovski, V.; Dubinskiy, S.; Inaekyan, K.; Kreitcberg, A.

    2016-03-01

    Nanostructures formed in Ti-50.26 at.%Ni shape memory alloy as a result of post-deformation annealing (PDA) at 400 °C (1 h) after cold rolling (CR) in the e = 0.3-1.9 true strain range are classified and quantitatively studied. The statistical quantitative transmission electron microscopy analysis of bright and dark field images and selected area diffraction patterns reveal the following regularities. Two types of nanostructure form in B2-austenite as a result of PDA after CR: (a) a nanosubgrained structure, which consists of subgrains formed as a result of polygonization of the initially highly dislocated substructure; (b) a nanocrystalline structure, which represents a combination of the deformation-induced nano-grains grown during PDA and new nano-grains formed during crystallization of the amorphous phase. After moderate CR (e = 0.3), mainly nanosubgrained structure forms as a result of PDA. After CR of moderate-to-high intensity (e = 0.5-1.0) followed by PDA, the structure is mixed (nanosubgrained+nanocrystalline). After high-intensity CR (e = 1.2-1.9) and PDA, the structure is mainly nanocrystalline. This nanostructure identification allows adequate analysis of the nature of the parent phase boundaries in the thermomechanically processed Ti-Ni alloys and of their effect on the transformation and mechanical behaviors.

  14. Rational design of coaxial mesoporous birnessite manganese dioxide/amorphous-carbon nanotubes arrays for advanced asymmetric supercapacitors

    KAUST Repository

    Zhu, Shijin

    2015-03-01

    Coaxial mesoporous MnO2/amorphous-carbon nanotubes have been synthesized via a facile and cost-effective strategy at room temperature. The coaxial double nanotubes of inner (outer) MnO2 and outer (inner) amorphous carbon can be obtained via fine tuning the preparative factors (e.g., deposition order and processing temperature). Furthermore, the electrochemical properties of the coaxial nanotubes were evaluated by cycle voltammetric (CV) and galvanostatic charge-discharge (GC) measurements. The as-prepared coaxial double nanotubes of outer MnO2 and inner amorphous carbon exhibit the optimized pseudocapacitance performance (362 F g-1) with good cycling stability, and ideal rate capability owning to the unique nanostructures. When assembled into two-electrode asymmetric supercapacitor, an energy density of 22.56 W h kg-1 at a power density of 224.9 W kg-1 is obtained. These findings provide a new and facile approach to fabricate high-performance electrode for supercapacitors.

  15. Wear Resistant Amorphous and Nanocomposite Coatings

    Energy Technology Data Exchange (ETDEWEB)

    Racek, O

    2008-03-26

    Glass forming materials (critical cooling rate <10{sup 4}K.s{sup -1}) are promising for their high corrosion and wear resistance. During rapid cooling, the materials form an amorphous structure that transforms to nanocrystalline during a process of devitrification. High hardness (HV 1690) can be achieved through a controlled crystallization. Thermal spray process has been used to apply coatings, which preserves the amorphous/nanocomposite structure due to a high cooling rate of the feedstock particles during the impact on a substrate. Wear properties have been studied with respect to process conditions and feedstock material properties. Application specific properties such as sliding wear resistance have been correlated with laboratory tests based on instrumented indentation and scratch tests.

  16. The Local Structure of Amorphous Silicon

    Science.gov (United States)

    Treacy, M. M. J.; Borisenko, K. B.

    2012-02-01

    It is widely believed that the continuous random network (CRN) model represents the structural topology of amorphous silicon. The key evidence is that the model can reproduce well experimental reduced density functions (RDFs) obtained by diffraction. By using a combination of electron diffraction and fluctuation electron microscopy (FEM) variance data as experimental constraints in a structural relaxation procedure, we show that the CRN is not unique in matching the experimental RDF. We find that inhomogeneous paracrystalline structures containing local cubic ordering at the 10 to 20 angstrom length scale are also fully consistent with the RDF data. Crucially, they also matched the FEM variance data, unlike the CRN model. The paracrystalline model has implications for understanding phase transformation processes in various materials that extend beyond amorphous silicon.

  17. Disappearance and Creation of Constrained Amorphous Phase

    Science.gov (United States)

    Cebe, Peggy; Lu, Sharon X.

    1997-03-01

    We report observation of the disappearance and recreation of rigid, or constrained, amorphous phase by sequential thermal annealing. Tempera- ture modulated differential scanning calorimetry (MDSC) is used to study the glass transition and lower melting endotherm after annealing. Cold crystallization of poly(phenylene sulfide), PPS, at a temperature just above Tg creates an initial large fraction of rigid amorphous phase (RAP). Brief, rapid annealing to a higher temperature causes RAP almost to disappear completely. Subsequent reannealing at the original lower temperature restores RAP to its original value. At the same time that RAP is being removed, Tg decreases; when RAP is restored, Tg also returns to its initial value. The crystal fraction remains unaffected by the annealing sequence.

  18. Compaction of amorphous iron–boron powder

    DEFF Research Database (Denmark)

    Hendriksen, Peter Vang; Mørup, Steen; Koch, Christian;

    1993-01-01

    Large scale practical use of bulk amorphous alloys requires the capability of molding the material to a desired design, for instance by compaction of an amorphous powder. This is a difficult task because the sintering temperature is limited by the crystallization temperature of the alloy.1 Here we......, should facilitate a compaction. The passivation layer, however, impedes a compaction. Isostatic pressing at 540 K at a pressure of 200 MPa clearly illustrated this; pellets pressed from passivated powder were much more brittle than pellets pressed from unpassivated powder. The density of the pellets...... was very low ([approximately-equal-to]25% of the density of bulk FeB). We have designed a die for uniaxial pressing in which the compaction can be performed without exposing the powder to air and have obtained densities larger than 60% of that of bulk FeB. We have reported studies of the dependence...

  19. Metastable states in amorphous chalcogenide semiconductors

    CERN Document Server

    Mikla, Victor I

    2009-01-01

    This book addresses an interesting and technologically important class of materials, the amorphous chalcogenide semiconductors. Experimental results on the structural and electronic metastable states in Se-rich chalcogenides are presented. Special attention is paid to the states in the mobility gap and their sensitivity to various factors such as irradiation, annealing and composition. Photoinduced changes of structure and physical properties are also considered and structural transformation at photocrystallization is studied in detail. Finally, the authors discuss potential applications of th

  20. NMR INVESTIGATIONS OF HYDROGENATED AMORPHOUS SILICON

    OpenAIRE

    J. Reimer

    1981-01-01

    A review is presented of the N.M.R. (Nuclear Magnetic Resonance) studies to date of hydrogenated amorphous silicon-hydrogen films. Structural features of proton N.M.R. lineshapes, dynamics of hydrogen containing defect sites, and the promise of quantitative determinations of local silicon-hydrogen bonding environments are discussed in detail. Finally, some comments are given on future directions for N.M.R. studies of hydrogenated thin films.

  1. Stable Transistors in Hydrogenated Amorphous Silicon

    OpenAIRE

    J. M. Shannon

    2004-01-01

    Thin-film field-effect transistors in hydrogenated amorphous silicon are notoriously unstable due to the formation of silicon dangling bond trapping states in the accumulated channel region during operation. Here, we show that by using a source-gated transistor a major improvement in stability is obtained. This occurs because the electron quasi-Fermi level is pinned near the center of the band in the active source region of the device and strong accumulation of electrons is prevented. The use...

  2. Amorphous silicon for thin-film transistors

    OpenAIRE

    Schropp, Rudolf Emmanuel Isidore

    1987-01-01

    Hydrogenated amorphous silicon (a-Si:H) has considerable potential as a semiconducting material for large-area photoelectric and photovoltaic applications. Moreover, a-Si:H thin-film transistors (TFT’s) are very well suited as switching devices in addressable liquid crystal display panels and addressable image sensor arrays, due to a new technology of low-cost, Iow-temperature processing overlarge areas. ... Zie: Abstract

  3. Transverse and longitudinal vibrations in amorphous silicon

    OpenAIRE

    Beltukov, Y. M.; De Fusco, C; Tanguy, A.; Parshin, D. A.

    2015-01-01

    We show that harmonic vibrations in amorphous silicon can be decomposed to transverse and longitudinal components in all frequency range even in the absence of the well defined wave vector ${\\bf q}$. For this purpose we define the transverse component of the eigenvector with given $\\omega$ as a component, which does not change the volumes of Voronoi cells around atoms. The longitudinal component is the remaining orthogonal component. We have found the longitudinal and transverse components of...

  4. Amorphous computing: examples, mathematics and theory

    OpenAIRE

    Stark, W. Richard

    2013-01-01

    The cellular automata model was described by John von Neumann and his friends in the 1950s as a representation of information processing in multicellular tissue. With crystalline arrays of cells and synchronous activity, it missed the mark (Stark and Hughes, BioSystems 55:107–117, 2000). Recently, amorphous computing, a valid model for morphogenesis in multicellular information processing, has begun to fill the void. Through simple examples and elementary mathematics, this paper begins a comp...

  5. A neutron diffraction study of amorphous boron

    Science.gov (United States)

    Delaplane, R. G.; Lundström, T.; Dahlborg, U.; Howells, W. S.

    1991-07-01

    The structure of amorphous boron has been studied with pulsed neutron diffraction techniques using the ISIS facilities at the Rutherford Appleton Laboratory. The experimental static structure factor S(Q) and radial distribution function support a structural model based on units of B12 icosahedra resembling those found in crystalline β-rhombohedral boron, but with a certain degree of disorder occurring in the linking between these subunits.

  6. Amorphization and recrystallization of covalent tetrahedral networks

    International Nuclear Information System (INIS)

    In the present paper recent studies on the amorphization and recrystallization of the light covalent ceramics SiC, Si3N4 and SiO2 (and in comparison Si) shall be reviewed. By combining long and short range order sensitive analysis techniques new insights into the disordering/reordering mechanisms and the structure of the disordered materials were gained. The results will be discussed in the light of a topological approach of the transition between periodic and aperiodic networks

  7. Superconducting State Parameters of Bulk Amorphous Alloys

    Directory of Open Access Journals (Sweden)

    Aditya M. Vora

    2012-12-01

    Full Text Available Well recognized empty core (EMC pseudopotential of Ashcroft is used to investigate the superconducting state parameters viz; electron-phonon coupling strength λ, Coulomb pseudopotential μ*, transition temperature TC, isotope effect exponent α and effective interaction strength NOV of some (Ni33Zr671 – xVx (x = 0, 0.05, 0.1, 0.15 bulk amorphous alloys. We have incorporated five different types of local field correction functions, proposed by Hartree (H, Taylor (T, Ichimaru-Utsumi (IU, Farid et al. (F and Sarkar et al. (S to show the effect of exchange and correlation on the aforesaid properties. Very strong influence of the various exchange and correlation functions is concluded from the present study. The TC obtained from Sarkar et al. (S local field correction function are found an excellent agreement with available theoretical data. Quadratic TC equation has been proposed, which provide successfully the TC values of bulk amorphous alloys under consideration. Also, the present results are found in qualitative agreement with other such earlier reported data, which confirms the superconducting phase in the s bulk amorphous alloys.

  8. Plasma deposition of amorphous metal alloys

    International Nuclear Information System (INIS)

    Rapid solidification, sputtering and electroless chemical deposition have been used to produce amorphous metal alloys which possess excellent corrosion and abrasion resistance. This paper discusses a new technique for obtaining amorphous metal alloy coatings. Plasma decomposition of Ni(CO)4 and PH3 in argon and hydrogen carrier gases [Ni(CO4/PH3--8/1] yielded films that were black and silver, respectively, in appearance. Both films were amorphous as determined by transmission electron microscopy. Films deposited using a hydrogen carrier gas were three orders of magnitude more conductive than those deposited using an argon carrier gas. Analysis of both films using electron microprobe analysis and inductively-coupled plasma spectroscopy showed an enrichment of P in the films over the P content in the plasma gas mixtures. Reducing the P content of the plasma gas mixture [Ni(CO)4/PH3--17/11 yielded crystalline films with no P enrichment. The grain size in these films was --60Δ as determined by x-ray line-broadening

  9. Porphyrin-Based Nanostructures for Photocatalytic Applications

    OpenAIRE

    Yingzhi Chen; Aoxiang Li; Zheng-Hong Huang; Lu-Ning Wang; Feiyu Kang

    2016-01-01

    Well-defined organic nanostructures with controllable size and morphology are increasingly exploited in optoelectronic devices. As promising building blocks, porphyrins have demonstrated great potentials in visible-light photocatalytic applications, because of their electrical, optical and catalytic properties. From this perspective, we have summarized the recent significant advances on the design and photocatalytic applications of porphyrin-based nanostructures. The rational strategies, such...

  10. Multi-periodic nanostructures for photon control

    DEFF Research Database (Denmark)

    Kluge, Christian; Adam, Jost; Barié, Nicole; Jakobs, Peter-Jürgen; Guttmann, Markus; Gerken, Martina

    We propose multi-periodic nanostructures yielded by superposition of multiple binary gratings for wide control over photon emission in thin-film devices. We present wavelength- and angle-resolved photoluminescence measurements of multi-periodically nanostructured organic light-emitting layers. Th...

  11. Nucleation theory and growth of nanostructures

    CERN Document Server

    Dubrovskii, Vladimir G

    2013-01-01

    Semiconductor nanostructures such as nanowires are promising building blocks of future nanoelectronic, nanophotonic and nanosensing devices. Their physical properties are primarily determined by the epitaxy process which is rather different from the conventional thin film growth. This book shows how the advanced nucleation theory can be used in modeling of growth properties, morphology and crystal phase of such nanostructures.

  12. Nanostructuring steel for injection molding tools

    DEFF Research Database (Denmark)

    Al-Azawi, A.; Smistrup, Kristian; Kristensen, Anders

    2014-01-01

    ion beam etching are combined to nanostructure the planar surface of a steel wafer. Injection molded plastic parts with enhanced surface properties, like anti-reflective, superhydrophobic and structural colors can be achieved by micro-and nanostructuring the surface of the steel molds. We investigate...

  13. Vertically aligned nanostructure scanning probe microscope tips

    Science.gov (United States)

    Guillorn, Michael A.; Ilic, Bojan; Melechko, Anatoli V.; Merkulov, Vladimir I.; Lowndes, Douglas H.; Simpson, Michael L.

    2006-12-19

    Methods and apparatus are described for cantilever structures that include a vertically aligned nanostructure, especially vertically aligned carbon nanofiber scanning probe microscope tips. An apparatus includes a cantilever structure including a substrate including a cantilever body, that optionally includes a doped layer, and a vertically aligned nanostructure coupled to the cantilever body.

  14. Metal oxide nanostructures with hierarchical morphology

    Science.gov (United States)

    Ren, Zhifeng; Lao, Jing Yu; Banerjee, Debasish

    2007-11-13

    The present invention relates generally to metal oxide materials with varied symmetrical nanostructure morphologies. In particular, the present invention provides metal oxide materials comprising one or more metallic oxides with three-dimensionally ordered nanostructural morphologies, including hierarchical morphologies. The present invention also provides methods for producing such metal oxide materials.

  15. Nanoparticle Decorated Ultrathin Porous Nanosheets as Hierarchical Co3O4 Nanostructures for Lithium Ion Battery Anode Materials

    Science.gov (United States)

    Mujtaba, Jawayria; Sun, Hongyu; Huang, Guoyong; Mølhave, Kristian; Liu, Yanguo; Zhao, Yanyan; Wang, Xun; Xu, Shengming; Zhu, Jing

    2016-02-01

    We report a facile synthesis of a novel cobalt oxide (Co3O4) hierarchical nanostructure, in which crystalline core-amorphous shell Co3O4 nanoparticles with a bimodal size distribution are uniformly dispersed on ultrathin Co3O4 nanosheets. When tested as anode materials for lithium ion batteries, the as-prepared Co3O4 hierarchical electrodes delivered high lithium storage properties comparing to the other Co3O4 nanostructures, including a high reversible capacity of 1053.1 mAhg-1 after 50 cycles at a current density of 0.2 C (1 C = 890 mAg-1), good cycling stability and rate capability.

  16. Carbon/Clay nanostructured composite obtained by hydrothermal method; Compositos nanoestruturados carbono/argila obtidos por metodo hidotermico

    Energy Technology Data Exchange (ETDEWEB)

    Barin, G.B.; Bispo, T.S.; Gimenez, I.F.; Barreto, L.S., E-mail: gabriela.borin@gmail.co [Universidade Federal de Sergipe (UFS), Aracaju, SE (Brazil). Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais; Souza Filho, A.G. [Universidade Federal do Ceara (UFC), Fortaleza, CE (Brazil). Dept. de Fisica

    2010-07-01

    The development of strategies for converting biomass into useful materials, more efficient energy carrier and / or hydrogen storage is shown a key issue for the present and future. Carbon nanostructure can be obtained by severe processing techniques such as arc discharge, chemical deposition and catalyzed pyrolysis of organic compounds. In this study we used hydrothermal methods for obtaining nanostructured composites of carbon / clay. To this end, we used coir dust and special clays. The samples were characterized by infrared spectroscopy, X-ray diffraction and Raman. The presence of the D band at 1350 cm{sup -1} in the Raman spectrum shows the formation of amorphous carbon with particle size of about 8.85 nm. (author)

  17. Nanoparticle Decorated Ultrathin Porous Nanosheets as Hierarchical Co3O4 Nanostructures for Lithium Ion Battery Anode Materials.

    Science.gov (United States)

    Mujtaba, Jawayria; Sun, Hongyu; Huang, Guoyong; Mølhave, Kristian; Liu, Yanguo; Zhao, Yanyan; Wang, Xun; Xu, Shengming; Zhu, Jing

    2016-01-01

    We report a facile synthesis of a novel cobalt oxide (Co3O4) hierarchical nanostructure, in which crystalline core-amorphous shell Co3O4 nanoparticles with a bimodal size distribution are uniformly dispersed on ultrathin Co3O4 nanosheets. When tested as anode materials for lithium ion batteries, the as-prepared Co3O4 hierarchical electrodes delivered high lithium storage properties comparing to the other Co3O4 nanostructures, including a high reversible capacity of 1053.1 mAhg(-1) after 50 cycles at a current density of 0.2 C (1 C = 890 mAg(-1)), good cycling stability and rate capability. PMID:26846434

  18. The formation of carbon nanostructures by in situ TEM mechanical nanoscale fatigue and fracture of carbon thin films

    Energy Technology Data Exchange (ETDEWEB)

    Wang, J J; Lockwood, A J; Peng, Y; Xu, X; Inkson, B J [Department of Engineering Materials, University of Sheffield, Sheffield S1 3JD (United Kingdom); Bobji, M S, E-mail: beverley.inkson@sheffield.ac.u [Department of Mechanical Engineering, Indian Institute of Science, Bangalore 560012, Karnataka (India)

    2009-07-29

    A technique to quantify in real time the microstructural changes occurring during mechanical nanoscale fatigue of ultrathin surface coatings has been developed. Cyclic nanoscale loading, with amplitudes less than 100 nm, is achieved with a mechanical probe miniaturized to fit inside a transmission electron microscope (TEM). The TEM tribological probe can be used for nanofriction and nanofatigue testing, with 3D control of the loading direction and simultaneous TEM imaging of the nano-objects. It is demonstrated that fracture of 10-20 nm thick amorphous carbon films on sharp gold asperities, by a single nanoscale shear impact, results in the formation of <10 nm diameter amorphous carbon filaments. Failure of the same carbon films after cyclic nanofatigue, however, results in the formation of carbon nanostructures with a significant degree of graphitic ordering, including a carbon onion.

  19. Energy transfer in nanostructured materials

    Science.gov (United States)

    Haughn, Chelsea

    Energy transport and loss are critical to the performance of optoelectronic devices such as photovoltaics and terahertz imaging devices. Nanostructured materials provide many opportunities to tailor transport and loss parameters for specific device applications. However, it has been very difficult to correlate specific nanoscale structural parameters with changes in these performance metrics. I report the development of new ways of using time-resolved photoluminescence (TRPL) to probe charge and energy transport and loss dynamics. These techniques are applied to several types of nanostructured materials, including bulk semiconductors with defects, self-assembled quantum dots and colloidal quantum dots. First, GaAs/InP double heterostructures grown via metal organic chemical vapor deposition (MOCVD) were characterized with TRPL. TRPL is typically used to extract minority carrier lifetimes, but we discovered that the measured lifetime depended critically on the intensity of the exciting laser. We developed a Shockley-Read-Hall model to extract trap state densities from intensity-dependent TRPL measurements. Second, we characterized energy and charge transfer between InAs quantum dots and ErAs nanoinclusions within III-V heterostructures. Using intensity- and temperature-dependent TRPL, we confirmed tunneling as the dominant mechanism of charge transport and characterized the electronic structure of the ErAs nanoparticles. Finally, we characterized energy transport in colloidal quantum dot cascade structures. These cascade structures utilize Forster Resonance Energy Transfer and trap state recycling to funnel excitons from donor layers to acceptor layers and suggest a promising method for avoiding losses associated with surface trap states. Collectively, the analysis of these disparate material types advances our understanding of energy dynamics in nanostructured materials and improves our ability to design the next generation of photovoltaic and optoelectronic

  20. Vicinal surfaces for functional nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Tegenkamp, Christoph [Institut fuer Festkoerperphysik, Gottfried Wilhelm Leibniz Universitaet Hannover, Appelstrasse 2, D-30167 Hannover (Germany)], E-mail: tegenkamp@fkp.uni-hannover.de

    2009-01-07

    Vicinal surfaces are currently the focus of research. The regular arrangements of atomic steps on a mesoscopic scale reveal the possibility to functionalize these surfaces for technical applications, e.g. nanowires, catalysts, etc. The steps of the vicinal surface are well-defined defect structures of atomic size for nucleation of low-dimensional nanostructures. The concentration and therefore the coupling between the nanostructures can be tuned over a wide range by simply changing the inclination angle of the substrate. However, the coupling of these nano-objects to the substrate is just as important in controlling their electronic or chemical properties and making a functionality useable. On the basis of stepped insulating films, these aspects are fulfilled and will be considered in the first part of this review. Recent results for the epitaxial growth of wide bandgap insulating films (CaF{sub 2}, MgO, NaCl, BaSrO) on metallic and semiconducting vicinal substrates (Si(100), Ge(100), Ag(100)) will be presented. The change of the electronic structure, the adsorption behavior as well as the kinetics and energetics of color centers in the presence of steps is discussed. The successful bridging of the gap between the atomic and mesoscopic world, i.e. the functionalization of vicinal surfaces by nanostructures, is demonstrated in the second part by metal adsorption on semiconducting surfaces. For (sub)monolayer coverage these systems have in common that the surface states do not hybridize with the support, i.e. the semiconducting surfaces are insulating. Here I will focus on the latest results of macroscopic transport measurements on Pb quantum wires grown on vicinal Si(111) showing indeed a one-dimensional transport behavior. (topical review)

  1. Vicinal surfaces for functional nanostructures

    International Nuclear Information System (INIS)

    Vicinal surfaces are currently the focus of research. The regular arrangements of atomic steps on a mesoscopic scale reveal the possibility to functionalize these surfaces for technical applications, e.g. nanowires, catalysts, etc. The steps of the vicinal surface are well-defined defect structures of atomic size for nucleation of low-dimensional nanostructures. The concentration and therefore the coupling between the nanostructures can be tuned over a wide range by simply changing the inclination angle of the substrate. However, the coupling of these nano-objects to the substrate is just as important in controlling their electronic or chemical properties and making a functionality useable. On the basis of stepped insulating films, these aspects are fulfilled and will be considered in the first part of this review. Recent results for the epitaxial growth of wide bandgap insulating films (CaF2, MgO, NaCl, BaSrO) on metallic and semiconducting vicinal substrates (Si(100), Ge(100), Ag(100)) will be presented. The change of the electronic structure, the adsorption behavior as well as the kinetics and energetics of color centers in the presence of steps is discussed. The successful bridging of the gap between the atomic and mesoscopic world, i.e. the functionalization of vicinal surfaces by nanostructures, is demonstrated in the second part by metal adsorption on semiconducting surfaces. For (sub)monolayer coverage these systems have in common that the surface states do not hybridize with the support, i.e. the semiconducting surfaces are insulating. Here I will focus on the latest results of macroscopic transport measurements on Pb quantum wires grown on vicinal Si(111) showing indeed a one-dimensional transport behavior. (topical review)

  2. Nanostructuring steel for injection molding tools

    DEFF Research Database (Denmark)

    Al-Azawi, A.; Smistrup, Kristian; Kristensen, Anders

    2014-01-01

    The production of nanostructured plastic items by injection molding with ridges down to 400 nm in width, which is the smallest line width replicated from nanostructured steel shims, is presented. Here we detail a micro-fabrication method where electron beam lithography, nano-imprint lithography and...... ion beam etching are combined to nanostructure the planar surface of a steel wafer. Injection molded plastic parts with enhanced surface properties, like anti-reflective, superhydrophobic and structural colors can be achieved by micro-and nanostructuring the surface of the steel molds. We investigate...... replica has been produced by injection molding with good structure transfer fidelity. Thus we have demonstrated that by utilizing well-established fabrication techniques, nanostructured steel shims that are used in injection molding, a technique that allows low cost mass fabrication of plastic items, are...

  3. Nanostructures, systems, and methods for photocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Reece, Steven Y.; Jarvi, Thomas D.

    2015-12-08

    The present invention generally relates to nanostructures and compositions comprising nanostructures, methods of making and using the nanostructures, and related systems. In some embodiments, a nanostructure comprises a first region and a second region, wherein a first photocatalytic reaction (e.g., an oxidation reaction) can be carried out at the first region and a second photocatalytic reaction (e.g., a reduction reaction) can be carried out at the second region. In some cases, the first photocatalytic reaction is the formation of oxygen gas from water and the second photocatalytic reaction is the formation of hydrogen gas from water. In some embodiments, a nanostructure comprises at least one semiconductor material, and, in some cases, at least one catalytic material and/or at least one photosensitizing agent.

  4. Some nanostructural features in ceramics.

    Science.gov (United States)

    Wen, S L

    1987-12-01

    Nanostructural features in some ceramics have been discussed and reviewed. Based on our research results and recent published investigations, many topics, such as grain, grain boundary, interface film, grain boundary engineering, microcrack, microdomain, nanodomain, domain boundary, and phase transformation, etc., have been dealt with; and many materials, such as Si3N4, beta''-Al2O3, MgO, SiC, (Hg, Cd) Te, BNN, ZrO2, PLZT, CdSe, Ca10(PO4)6, (OH)2, etc., have been involved. The results are important to understand the relation between the structure and property of materials and to improve the materials' technology. PMID:3505597

  5. Superradiance in spherical layered nanostructures

    Science.gov (United States)

    Goupalov, S. V.

    2016-06-01

    We propose a design of a spherically symmetric nanostructure consisting of alternate concentric semiconductor and dielectric layers. The exciton states in different semiconductor layers of such a structure interact via the common electromagnetic field of light. We show that, if the exciton states in N semiconductor layers are in resonance with one another, then a superradiant state emerges under optical excitation of such a structure. We discuss the conditions under which superradiance can be observed and show that they strongly depend on the valence-band structure of the semiconductor layers.

  6. Covalent crosslinking of carbon nanostructures

    Indian Academy of Sciences (India)

    Urmimala Maitra; M Pandeeswar; T Govindaraju

    2012-05-01

    Covalent crosslinking of carbon nanostructures of different dimensionalities such as nanodiamond, single walled carbon nanotubes (SWNTs) and graphene can yield useful homo- and hetero-binary conjugates. Binary conjugation of the nanocarbons has been achieved by introducing symmetrical amide-linkages between acid (-COOH) functionalized nanocarbons and a diamine-linker. The binary conjugates have been characterized by using transmission electron microscopy as well as infrared, Raman and photoluminescence spectroscopies. Dispersions of covalently crosslinked binary conjugates of nanocarbons could be obtained in dimethyl formamide (DMF). Composites of the binary conjugates with polymer can be readily prepared by using the DMF suspensions.

  7. Supramolecular ordering of nanostructured polymers

    Czech Academy of Sciences Publication Activity Database

    Matějka, Libor; Donato, Ricardo Keitel; Janata, Miroslav; Pleštil, Josef; Schrekker, H. S.

    Madrid : Instituto de Ciencia y Tecnología de Polímeros, CSIC, 2010 - (Mijangos, C.; Kenny, J.; Hernández, R.; Sacristan, J.; Lopez-Manchado, M.; Verdejo, R.). s. 78 ISBN 978-84-613-9812-6. [International ECNP Conference on Nanostructured Polymers & Nanocomposites /6./. 28.04.2010-30.04.2010, Madrid] R&D Projects: GA AV ČR IAA400500701 Institutional research plan: CEZ:AV0Z40500505 Keywords : nanocomposites * self assembly Subject RIV: CD - Macromolecular Chemistry

  8. Investigations on silicon/amorphous-carbon and silicon/nanocrystalline palladium/ amorphous-carbon interfaces.

    Science.gov (United States)

    Roy, M; Sengupta, P; Tyagi, A K; Kale, G B

    2008-08-01

    Our previous work revealed that significant enhancement in sp3-carbon content of amorphous carbon films could be achieved when grown on nanocrystalline palladium interlayer as compared to those grown on bare silicon substrates. To find out why, the nature of interface formed in both the cases has been investigated using Electron Probe Micro Analysis (EPMA) technique. It has been found that a reactive interface in the form of silicon carbide and/silicon oxy-carbide is formed at the interface of silicon/amorphous-carbon films, while palladium remains primarily in its native form at the interface of nanocrystalline palladium/amorphous-carbon films. However, there can be traces of dissolved oxygen within the metallic layer as well. The study has been corroborated further from X-ray photoelectron spectroscopic studies. PMID:19049221

  9. Structural, thermal, optical and photoacoustic study of nanostructured FeSb{sub 2} prepared by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Poffo, C.M. [Departamento de Engenharia Mecânica, Universidade Federal de Santa Catarina, Campus Universitário Trindade, S/N, C.P. 476, 88040-900 Florianópolis, Santa Catarina (Brazil); Lima, J.C. de, E-mail: fsc1jcd@fisica.ufsc.br [Departamento de Física, Universidade Federal de Santa Catarina, Campus Universitário Trindade, S/N, C.P. 476, 88040-900 Florianópolis, Santa Catarina (Brazil); Souza, S.M.; Trichês, D.M. [Departamento de Física, Universidade Federal do Amazonas, 3000 Japiim, 69077-000 Manaus, Amazonas (Brazil); Grandi, T.A. [Departamento de Física, Universidade Federal de Santa Catarina, Campus Universitário Trindade, S/N, C.P. 476, 88040-900 Florianópolis, Santa Catarina (Brazil); Biasi, R.S. de [Seção de Engenharia Mecânica e de Materiais, Instituto Militar de Engenharia, 22290-270 Rio de Janeiro, RJ (Brazil)

    2013-03-15

    Mechanical alloying of elemental Fe and Sb powders yielded nanostructured FeSb{sub 2}, an amorphous phase, along with unreacted Sb. The volume fractions of FeSb{sub 2}, Sb nanocrystals and interfacial/amorphous components were estimated from the X-ray diffraction pattern of the as-miller powder. The thermal stability of FeSb{sub 2} was investigated by heating the powder at 250 °C and 400 °C. The XRD pattern of the sample annealed at 250 °C showed nucleation of Fe{sub 3}O{sub 4} and decomposition of FeSb{sub 2}. For an annealing temperature of 400 °C, besides crystallization of the amorphous phase, the volume fractions of Sb and Fe{sub 3}O{sub 4} increased and the volume fraction of FeSb{sub 2} decreased. The optical band gap energy for samples as-milled and annealed at 400 °C was measured, and a slight decrease in the band gap was observed in the annealed sample. Thermal diffusivity parameter of the as-milled sample and of the annealed sample at 400 °C was also measured, as well as other transport properties. We also studied the contribution of the thermal diffusivity of the interfacial/amorphous component to the thermal diffusivity of the as-milled sample.

  10. Effective magnetic anisotropy of amorphous and nanocrystalline Fe71.5Al2Cu1Nb3Si13.5B9 alloy ribbon

    International Nuclear Information System (INIS)

    The effective magnetic anisotropy of the Fe71.5Al2Cu1Nb3Si13.5B9 alloy with different nanostructures has been investigated. The nanostructured phase was produced by means of thermal treatment (520 - 600 degreeC during 1 h) to develop the devitrification of the precursor amorphous material. The effective magnetic anisotropy was evaluated from the measurement of the bias field dependence of the transverse susceptibility. Values of the effective anisotropy field, Hk, from 20 Oe (as-quenched sample) down to 7 Oe (optimum nanocrystalline state) were obtained. Such values of Hk are close to those obtained in the classical nanocrystalline Fe73.5Cu1Nb3Si13.5B9 alloy (8 - 10 Oe) alloy. The Al could enhance the intergranular coupling, leading to the ultrasoft magnetic character of this nanocrystalline Al-containing alloy. [copyright] 2001 American Institute of Physics

  11. Spontaneous Growth of ZnCO3 Nanowires on ZnO Nanostructures in Normal Ambient Environment: Unstable ZnO Nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Z.; Tao, J.; Zhu, Y.; Huang, J.-F.; Paranthaman, M.P.

    2009-12-09

    ZnO nanowires, one of the most investigated nanostructures that promise numerous applications in nanophotonics, opto-electronics, and energy, are generally thought to be highly stable under ambient conditions because of their oxide nature. Here, we report that ZnO nanowires are actually extremely unstable even in normal ambient environment (70% RH, and {approx}350 ppm CO{sub 2}) because of atmospheric corrosion. When placed on an oxide substrate (e.g., glass slide) and exposed in air, ZnO nanowires tend to react with airborne moisture and CO{sub 2} to form amorphous ZnCO{sub 3} thin films and nanowires. The factors that specially affect the corrosion of ZnO nanowires in a laboratory environment include CO{sub 2}, humidity, and substrates. Our results suggest that a CO{sub 2}{sup -} and/or moisture-free environment are required in order for optimal applications of ZnO nanowires.

  12. Monte Carlo simulation of magnetic nanostructured thin films

    Institute of Scientific and Technical Information of China (English)

    Guan Zhi-Qiang; Yutaka Abe; Jiang Dong-Hua; Lin Hai; Yoshitake Yamazakia; Wu Chen-Xu

    2004-01-01

    @@ Using Monte Carlo simulation, we have compared the magnetic properties between nanostructured thin films and two-dimensional crystalline solids. The dependence of nanostructured properties on the interaction between particles that constitute the nanostructured thin films is also studied. The result shows that the parameters in the interaction potential have an important effect on the properties of nanostructured thin films at the transition temperatures.

  13. Dispersion and separation of nanostructured carbon in organic solvents

    Science.gov (United States)

    Landi, Brian J. (Inventor); Raffaelle, Ryne P. (Inventor); Ruf, Herbert J. (Inventor); Evans, Christopher M. (Inventor)

    2011-01-01

    The present invention relates to dispersions of nanostructured carbon in organic solvents containing alkyl amide compounds and/or diamide compounds. The invention also relates to methods of dispersing nanostructured carbon in organic solvents and methods of mobilizing nanostructured carbon. Also disclosed are methods of determining the purity of nanostructured carbon.

  14. Correlating Raman-spectroscopy and high-resolution transmission-electron-microscopy studies of amorphous/nanocrystalline multilayered silicon thin films

    Energy Technology Data Exchange (ETDEWEB)

    Gajovic, Andreja, E-mail: gajovic@irb.h [Ruder Boskovic Institute, POB 180, HR-1002 Zagreb (Croatia); Institute Jozef Stefan, Jamova 39, SI-1000 Ljubljana (Slovenia); Gracin, Davor; Juraic, Krunoslav; Sancho-Parramon, Jordi [Ruder Boskovic Institute, POB 180, HR-1002 Zagreb (Croatia); Ceh, Miran [Institute Jozef Stefan, Jamova 39, SI-1000 Ljubljana (Slovenia)

    2009-07-31

    The nanostructure of multilayered silicon thin films was studied using Raman spectroscopy (RS) and high-resolution transmission electron microscopy (HRTEM). Since the properties of nanocrystalline silicon layer depend on the size of the nanocrystals, an accurate determination of the crystallite sizes and the crystalline fraction is of primary importance. The average sizes of the nanocrystals estimated by RS, assuming bi-modal distribution of crystal sizes, were close to 2 nm and above 5-20 nm. HRTEM confirmed the existence of nanocrystals with a mean square value of around 2 nm and certain number of larger nanocrystals, embedded in an amorphous matrix. The correlation between the results obtained by these two techniques is discussed. The optical properties of measured samples corresponded to an amorphous-crystalline mixture with indication of confinement effects compatible with 2 nm nanocrystals.

  15. Characterization of Amorphous and Co-Amorphous Simvastatin Formulations Prepared by Spray Drying

    OpenAIRE

    Goedele Craye; Korbinian Löbmann; Holger Grohganz; Thomas Rades; Riikka Laitinen

    2015-01-01

    In this study, spray drying from aqueous solutions, using the surface-active agent sodium lauryl sulfate (SLS) as a solubilizer, was explored as a production method for co-amorphous simvastatin–lysine (SVS-LYS) at 1:1 molar mixtures, which previously have been observed to form a co-amorphous mixture upon ball milling. In addition, a spray-dried formulation of SVS without LYS was prepared. Energy-dispersive X-ray spectroscopy (EDS) revealed that SLS coated the SVS and SVS-LYS particles upon sp...

  16. Suspension plasma spraying of nanostructured WC-12Co coatings

    Science.gov (United States)

    Berghaus, J. Oberste; Marple, B.; Moreau, C.

    2006-12-01

    Nanostructured WC-12% Co coatings were deposited by suspension plasma spraying of submicron feedstock powders, using an internal injection plasma torch. The liquid carrier used in this approach allows for controlled injection of much finer particles than in conventional thermal spraying, leading to thin coatings with a fine surface finish. A polyethylene-imine (PEI) dispersant was used to stabilize the colloidal suspension in an ethanol carrier. In-flight particle states were measured for a number of operating conditions of varying plasma gas flow rates, feed rates, and standoff distances and were related to the resulting microstructure, phase composition (EDS, SEM, XRD), and Vickers hardness. High in-flight particle velocities (>800 m/s) were generated, leading to dense coatings. It was observed that the coating quality was generally compromised by the high temperature and reactivity of the small particles. To compensate for this shortcoming, the suspension feed rate was adjusted, thereby varying the thermal load on the plasma. Results showed that a slightly larger agglomerate size, in conjunction with low particle jet temperatures, could somewhat limit the decomposition of WC into brittle W2C/W3C and amorphous cobalt containing binder phases.

  17. Process Development for Nanostructured Photovoltaics

    Energy Technology Data Exchange (ETDEWEB)

    Elam, Jeffrey W.

    2015-01-01

    Photovoltaic manufacturing is an emerging industry that promises a carbon-free, nearly limitless source of energy for our nation. However, the high-temperature manufacturing processes used for conventional silicon-based photovoltaics are extremely energy-intensive and expensive. This high cost imposes a critical barrier to the widespread implementation of photovoltaic technology. Argonne National Laboratory and its partners recently invented new methods for manufacturing nanostructured photovoltaic devices that allow dramatic savings in materials, process energy, and cost. These methods are based on atomic layer deposition, a thin film synthesis technique that has been commercialized for the mass production of semiconductor microelectronics. The goal of this project was to develop these low-cost fabrication methods for the high efficiency production of nanostructured photovoltaics, and to demonstrate these methods in solar cell manufacturing. We achieved this goal in two ways: 1) we demonstrated the benefits of these coatings in the laboratory by scaling-up the fabrication of low-cost dye sensitized solar cells; 2) we used our coating technology to reduce the manufacturing cost of solar cells under development by our industrial partners.

  18. Quantitative Characterization of Nanostructured Materials

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Frank (Bud) Bridges, University of California-Santa Cruz

    2010-08-05

    The two-and-a-half day symposium on the "Quantitative Characterization of Nanostructured Materials" will be the first comprehensive meeting on this topic held under the auspices of a major U.S. professional society. Spring MRS Meetings provide a natural venue for this symposium as they attract a broad audience of researchers that represents a cross-section of the state-of-the-art regarding synthesis, structure-property relations, and applications of nanostructured materials. Close interactions among the experts in local structure measurements and materials researchers will help both to identify measurement needs pertinent to real-world materials problems and to familiarize the materials research community with the state-of-the-art local structure measurement techniques. We have chosen invited speakers that reflect the multidisciplinary and international nature of this topic and the need to continually nurture productive interfaces among university, government and industrial laboratories. The intent of the symposium is to provide an interdisciplinary forum for discussion and exchange of ideas on the recent progress in quantitative characterization of structural order in nanomaterials using different experimental techniques and theory. The symposium is expected to facilitate discussions on optimal approaches for determining atomic structure at the nanoscale using combined inputs from multiple measurement techniques.

  19. Biocompatibility of plasma nanostructured biopolymers

    Energy Technology Data Exchange (ETDEWEB)

    Slepičková Kasálková, N. [Department of Solid State Engineering, Institute of Chemical Technology, 166 28 Prague (Czech Republic); Slepička, P., E-mail: petr.slepicka@vscht.cz [Department of Solid State Engineering, Institute of Chemical Technology, 166 28 Prague (Czech Republic); Bačáková, L. [Institute of Physiology, Academy of Sciences of the Czech Republic 142 20 Prague (Czech Republic); Sajdl, P. [Department of Power Engineering, Institute of Chemical Technology, 166 28 Prague (Czech Republic); Švorčík, V. [Department of Solid State Engineering, Institute of Chemical Technology, 166 28 Prague (Czech Republic)

    2013-07-15

    Many areas of medicine such as tissue engineering requires not only mastery of modification techniques but also thorough knowledge of the interaction of cells with solid state substrates. Plasma treatment can be used to effective modification, nanostructuring and therefore can significantly change properties of materials. In this work the biocompatibility of the plasma nanostructured biopolymers substrates was studied. Changes in surface chemical structure were studied by X-ray photoelectron spectroscopy (XPS). The morphology pristine and modified samples were determined using atomic force microscopy (AFM). The surface wettability was determined by goniometry from contact angle. Biocompatibility was determined by in vitro tests, the rat vascular smooth muscle cells (VSMCs) were cultivated on the pristine and plasma modified biopolymer substrates. Their adhesion, proliferation, spreading and homogeneous distribution on polymers was monitored. It was found that the plasma treatment leads to rapid decrease of contact angle for all samples. Contact angle decreased with increasing time of modification. XPS measurements showed that plasma treatment leads to changes in ratio of polar and non-polar groups. Plasma modification was accompanied by a change of surface morphology. Biological tests found that plasma treatment have positive effect on cells adhesion and proliferation cells and affects the size of cell’s adhesion area. Changes in plasma power or in exposure time influences the number of adhered and proliferated cells and their distribution on biopolymer surface.

  20. Hydrogen storage in nanotubes & nanostructures

    Directory of Open Access Journals (Sweden)

    George E. Froudakis

    2011-07-01

    Full Text Available Over the last several years, a significant share of the scientific community has focused its attention on the hydrogen storage problem. Since 1997, when carbon nanotubes appeared to be a promising storage material, many theoretical and experimental groups have investigated the hydrogen storage capacity of these carbon nanostructures. These efforts were not always successful and consequently, the results obtained were often controversial. In the current review we attempt to summarize some the highlights of the work on hydrogen storage in various types of nanotube and nanostructure, in a critical way. The nature of the interaction between hydrogen and the host nanomaterials, as revealed through theoretical modeling, helps us understand the basic mechanisms of hydrogen storage. Analysis of the results reveals why high hydrogen storage capacity at ambient conditions, which meets the DOE targets, cannot occur in bare carbon nanotubes. Through our analysis we also propose guidelines to enhance the hydrogen storage capacity of already synthesized materials and recommend advanced materials for this application.

  1. Biocompatibility of plasma nanostructured biopolymers

    International Nuclear Information System (INIS)

    Many areas of medicine such as tissue engineering requires not only mastery of modification techniques but also thorough knowledge of the interaction of cells with solid state substrates. Plasma treatment can be used to effective modification, nanostructuring and therefore can significantly change properties of materials. In this work the biocompatibility of the plasma nanostructured biopolymers substrates was studied. Changes in surface chemical structure were studied by X-ray photoelectron spectroscopy (XPS). The morphology pristine and modified samples were determined using atomic force microscopy (AFM). The surface wettability was determined by goniometry from contact angle. Biocompatibility was determined by in vitro tests, the rat vascular smooth muscle cells (VSMCs) were cultivated on the pristine and plasma modified biopolymer substrates. Their adhesion, proliferation, spreading and homogeneous distribution on polymers was monitored. It was found that the plasma treatment leads to rapid decrease of contact angle for all samples. Contact angle decreased with increasing time of modification. XPS measurements showed that plasma treatment leads to changes in ratio of polar and non-polar groups. Plasma modification was accompanied by a change of surface morphology. Biological tests found that plasma treatment have positive effect on cells adhesion and proliferation cells and affects the size of cell’s adhesion area. Changes in plasma power or in exposure time influences the number of adhered and proliferated cells and their distribution on biopolymer surface

  2. Electrochromic Properties of Li+-Intercalated Amorphous Tungsten (aWO3-x) and Titanium (aTiO2-x) Oxide Thin Films

    Science.gov (United States)

    Triana, C. A.; Granqvist, C. G.; Niklasson, G. A.

    2014-11-01

    We report on electrochromic properties of stoichiometric and oxygen-deficient amorphous films, denoted aWO3-x and aTiO2-x, under Li+-ion-electron inter/deintercalation. Optical characterization of the films in their as-deposited, fully intercalated (dark), and bleached states were performed by in-situ optical transmittance measurements. We explore electrochromism and optical absorption phenomena in the context of oxygen deficiency and nanostructure. Studies by cyclic voltammetry suggest good optical modulation and charge capacity upon Li+-ion-electron inter/deintercalation for almost stoichiometric films.

  3. Electrochromic Properties of Li+-Intercalated Amorphous Tungsten (aWO3-x) and Titanium (aTiO2-x) Oxide Thin Films

    International Nuclear Information System (INIS)

    We report on electrochromic properties of stoichiometric and oxygen-deficient amorphous films, denoted aWO3-x and aTiO2-x, under Li+-ion-electron inter/deintercalation. Optical characterization of the films in their as-deposited, fully intercalated (dark), and bleached states were performed by in-situ optical transmittance measurements. We explore electrochromism and optical absorption phenomena in the context of oxygen deficiency and nanostructure. Studies by cyclic voltammetry suggest good optical modulation and charge capacity upon Li+-ion-electron inter/deintercalation for almost stoichiometric films

  4. Crystallization inhibition of an amorphous sucrose system using raffinose

    Institute of Scientific and Technical Information of China (English)

    LEINEN K.M.; LABUZA T.P.

    2006-01-01

    The shelf life of pure amorphous sucrose systems, such as cotton candy, can be very short. Previous studies have shown that amorphous sucrose systems held above the glass transition temperature will collapse and crystallize. One study,however, showed that adding a small percent of another type of sugar, such as trehalose, to sucrose can extend the shelf life of the amorphous system by slowing crystallization. This study explores the hypothesis that raffinose increases the stability of an amorphous sucrose system. Cotton candy at 5 wt% raffinose and 95 wt% sucrose was made and stored at room temperature and three different relative humidities (%RH) 11%RH, 33%RH, and 43%RH. XRD patterns, and glass transition temperatures were obtained to determine the stability as a function of %RH. The data collected showed that raffinose slows sucrose crystallization in a low moisture amorphous state above the glass transition temperature and therefore improves the stability of amorphous sucrose systems.

  5. Emerging trends in the stabilization of amorphous drugs

    DEFF Research Database (Denmark)

    Laitinen, Riikka; Löbmann, Korbinian; Strachan, Clare J.;

    2013-01-01

    The number of active pharmaceutical substances having high therapeutic potential but low water solubility is constantly increasing, making it difficult to formulate these compounds as oral dosage forms. The solubility and dissolution rate, and thus potentially the bioavailability, of these poorly...... water-soluble drugs can be increased by the formation of stabilized amorphous forms. Currently, formulation as solid polymer dispersions is the preferred method to enhance drug dissolution and to stabilize the amorphous form of a drug. The purpose of this review is to highlight emerging alternative...... methods to amorphous polymer dispersions for stabilizing the amorphous form of drugs. First, an overview of the properties and stabilization mechanisms of amorphous forms is provided. Subsequently, formulation approaches such as the preparation of co-amorphous small-molecule mixtures and the use of...

  6. Amorphous-silicon module hot-spot testing

    Science.gov (United States)

    Gonzalez, C. C.

    1985-01-01

    Hot spot heating occurs when cell short-circuit current is lower than string operating current. Amorphous cell hot spot are tested to develop the techniques required for performing reverse bias testing of amorphous cells. Also, to quantify the response of amorphous cells to reverse biasing. Guidelines are developed from testing for reducing hot spot susceptibility of amorphous modules and to develop a qualification test for hot spot testing of amorphous modules. It is concluded that amorphous cells undergo hot spot heating similarly to crystalline cells. Comparison of results obtained with submodules versus actual modules indicate heating levels lower in actual modules. Module design must address hot spot testing and hot spot qualification test conducted on modules showed no instabilities and minor cell erosion.

  7. Formation of amorphous silicon by light ion damage

    International Nuclear Information System (INIS)

    Amorphization by implantation of boron ions (which is the lightest element generally used in I.C. fabrication processes) has been systematically studied for various temperatures, various voltages and various dose rates. Based on theoretical considerations and experimental results, a new amorphization model for light and intermediate mass ion damage is proposed consisting of two stages. The role of interstitial type point defects or clusters in amorphization is emphasized. Due to the higher mobility of interstitials out-diffusion to the surface particularly during amorphization with low energy can be significant. From a review of the idealized amorphous structure, diinterstitial-divacancy pairs are suggested to be the embryos of amorphous zones formed during room temperature implantation. The stacking fault loops found in specimens implanted with boron at room temperature are considered to be the origin of secondary defects formed during annealing

  8. Silicon-embedded copper nanostructure network for high energy storage

    Science.gov (United States)

    Yu, Tianyue

    2016-03-15

    Provided herein are nanostructure networks having high energy storage, electrochemically active electrode materials including nanostructure networks having high energy storage, as well as electrodes and batteries including the nanostructure networks having high energy storage. According to various implementations, the nanostructure networks have high energy density as well as long cycle life. In some implementations, the nanostructure networks include a conductive network embedded with electrochemically active material. In some implementations, silicon is used as the electrochemically active material. The conductive network may be a metal network such as a copper nanostructure network. Methods of manufacturing the nanostructure networks and electrodes are provided. In some implementations, metal nanostructures can be synthesized in a solution that contains silicon powder to make a composite network structure that contains both. The metal nanostructure growth can nucleate in solution and on silicon nanostructure surfaces.

  9. Determination of the optical band gap for amorphous and nanocrystalline copper oxide thin films prepared by SILAR technique

    Energy Technology Data Exchange (ETDEWEB)

    Abdel Rafea, M; Roushdy, N [Electronic Materials Department, Advanced Technologies and New Materials Institute, Mubarak City for Scientific Research and Technology Applications, PO Box 21934, New Borg El-Arab City, Alexandria (Egypt)], E-mail: m.abdelrafea@mucsat.sci.eg

    2009-01-07

    Amorphous copper oxide films were deposited using the SILAR technique. Both Cu{sub 2}O and CuO crystallographic phases exist in deposited and annealed films. Crystallization and growth processes by annealing at temperatures up to 823 K form grains with nano- and micro-spherical shapes. The calculated crystallite size from the XRD measurement was found to be in the range 14-21 nm while nano-spheres in the diameter range 50-100 nm were observed by SEM micrographs. The band gap for amorphous film was found to be 2.3 eV which increased slowly to 2.4 eV by annealing the film at 373 K. This was explained by defect redistribution in amorphous films. Annealing in the temperature range 373-673 K decreased the band gap gradually to 1.85 eV. The decrease of the band gap with annealing temperature in the range 373-673 K agrees well with the Brus model of the energy gap confinement effect in nanostructured semiconducting materials. Annealing in the temperature range 673-823 K decreases the band gap slowly to 1.7 eV due to the smaller contribution of the confinement effect. Below 573 K, Cu{sub 2}O is the most probable crystalline phase in the film, while Cu{sub 2}O and CuO crystalline phases may coexist at annealing temperatures above 573 K due to further oxidation of Cu{sub 2}O. A wider transmittance spectral window in the visible region was obtained by controlling the annealing conditions of the amorphous copper oxide film and its applicability to the window layer of solar cell was suggested.

  10. Determination of the optical band gap for amorphous and nanocrystalline copper oxide thin films prepared by SILAR technique

    International Nuclear Information System (INIS)

    Amorphous copper oxide films were deposited using the SILAR technique. Both Cu2O and CuO crystallographic phases exist in deposited and annealed films. Crystallization and growth processes by annealing at temperatures up to 823 K form grains with nano- and micro-spherical shapes. The calculated crystallite size from the XRD measurement was found to be in the range 14-21 nm while nano-spheres in the diameter range 50-100 nm were observed by SEM micrographs. The band gap for amorphous film was found to be 2.3 eV which increased slowly to 2.4 eV by annealing the film at 373 K. This was explained by defect redistribution in amorphous films. Annealing in the temperature range 373-673 K decreased the band gap gradually to 1.85 eV. The decrease of the band gap with annealing temperature in the range 373-673 K agrees well with the Brus model of the energy gap confinement effect in nanostructured semiconducting materials. Annealing in the temperature range 673-823 K decreases the band gap slowly to 1.7 eV due to the smaller contribution of the confinement effect. Below 573 K, Cu2O is the most probable crystalline phase in the film, while Cu2O and CuO crystalline phases may coexist at annealing temperatures above 573 K due to further oxidation of Cu2O. A wider transmittance spectral window in the visible region was obtained by controlling the annealing conditions of the amorphous copper oxide film and its applicability to the window layer of solar cell was suggested.

  11. Optical bandgap of ultra-thin amorphous silicon films deposited on crystalline silicon by PECVD

    Science.gov (United States)

    Abdulraheem, Yaser; Gordon, Ivan; Bearda, Twan; Meddeb, Hosny; Poortmans, Jozef

    2014-05-01

    An optical study based on spectroscopic ellipsometry, performed on ultrathin hydrogenated amorphous silicon (a-Si:H) layers, is presented in this work. Ultrathin layers of intrinsic amorphous silicon have been deposited on n-type mono-crystalline silicon (c-Si) wafers by plasma enhanced chemical vapor deposition (PECVD). The layer thicknesses along with their optical properties -including their refractive index and optical loss- were characterized by spectroscopic ellipsometry (SE) in a wavelength range from 250 nm to 850 nm. The data was fitted to a Tauc-Lorentz optical model and the fitting parameters were extracted and used to compute the refractive index, extinction coefficient and optical bandgap. Furthermore, the a-Si:H film grown on silicon was etched at a controlled rate using a TMAH solution prepared at room temperature. The optical properties along with the Tauc-Lorentz fitting parameters were extracted from the model as the film thickness was reduced. The etch rate for ultrathin a-Si:H layers in TMAH at room temperature was found to slow down drastically as the c-Si interface is approached. From the Tauc-Lorentz parameters obtained from SE, it was found that the a-Si film exhibited properties that evolved with thickness suggesting that the deposited film is non-homogeneous across its depth. It was also found that the degree of crystallinity and optical (Tauc) bandgap increased as the layers were reduced in thickness and coming closer to the c-Si substrate interface, suggesting the presence of nano-structured clusters mixed into the amorphous phase for the region close to the crystalline silicon substrate. Further results from Atomic Force Microscopy and Transmission Electron Microscopy confirmed the presence of an interfacial transitional layer between the amorphous film and the underlying substrate showing silicon nano-crystalline enclosures that can lead to quantum confinement effects. Quantum confinement is suggested to be the cause of the observed

  12. Optical bandgap of ultra-thin amorphous silicon films deposited on crystalline silicon by PECVD

    Directory of Open Access Journals (Sweden)

    Yaser Abdulraheem

    2014-05-01

    Full Text Available An optical study based on spectroscopic ellipsometry, performed on ultrathin hydrogenated amorphous silicon (a-Si:H layers, is presented in this work. Ultrathin layers of intrinsic amorphous silicon have been deposited on n-type mono-crystalline silicon (c-Si wafers by plasma enhanced chemical vapor deposition (PECVD. The layer thicknesses along with their optical properties –including their refractive index and optical loss- were characterized by spectroscopic ellipsometry (SE in a wavelength range from 250 nm to 850 nm. The data was fitted to a Tauc-Lorentz optical model and the fitting parameters were extracted and used to compute the refractive index, extinction coefficient and optical bandgap. Furthermore, the a-Si:H film grown on silicon was etched at a controlled rate using a TMAH solution prepared at room temperature. The optical properties along with the Tauc-Lorentz fitting parameters were extracted from the model as the film thickness was reduced. The etch rate for ultrathin a-Si:H layers in TMAH at room temperature was found to slow down drastically as the c-Si interface is approached. From the Tauc-Lorentz parameters obtained from SE, it was found that the a-Si film exhibited properties that evolved with thickness suggesting that the deposited film is non-homogeneous across its depth. It was also found that the degree of crystallinity and optical (Tauc bandgap increased as the layers were reduced in thickness and coming closer to the c-Si substrate interface, suggesting the presence of nano-structured clusters mixed into the amorphous phase for the region close to the crystalline silicon substrate. Further results from Atomic Force Microscopy and Transmission Electron Microscopy confirmed the presence of an interfacial transitional layer between the amorphous film and the underlying substrate showing silicon nano-crystalline enclosures that can lead to quantum confinement effects. Quantum confinement is suggested to be the cause

  13. Optical bandgap of ultra-thin amorphous silicon films deposited on crystalline silicon by PECVD

    International Nuclear Information System (INIS)

    An optical study based on spectroscopic ellipsometry, performed on ultrathin hydrogenated amorphous silicon (a-Si:H) layers, is presented in this work. Ultrathin layers of intrinsic amorphous silicon have been deposited on n-type mono-crystalline silicon (c-Si) wafers by plasma enhanced chemical vapor deposition (PECVD). The layer thicknesses along with their optical properties –including their refractive index and optical loss- were characterized by spectroscopic ellipsometry (SE) in a wavelength range from 250 nm to 850 nm. The data was fitted to a Tauc-Lorentz optical model and the fitting parameters were extracted and used to compute the refractive index, extinction coefficient and optical bandgap. Furthermore, the a-Si:H film grown on silicon was etched at a controlled rate using a TMAH solution prepared at room temperature. The optical properties along with the Tauc-Lorentz fitting parameters were extracted from the model as the film thickness was reduced. The etch rate for ultrathin a-Si:H layers in TMAH at room temperature was found to slow down drastically as the c-Si interface is approached. From the Tauc-Lorentz parameters obtained from SE, it was found that the a-Si film exhibited properties that evolved with thickness suggesting that the deposited film is non-homogeneous across its depth. It was also found that the degree of crystallinity and optical (Tauc) bandgap increased as the layers were reduced in thickness and coming closer to the c-Si substrate interface, suggesting the presence of nano-structured clusters mixed into the amorphous phase for the region close to the crystalline silicon substrate. Further results from Atomic Force Microscopy and Transmission Electron Microscopy confirmed the presence of an interfacial transitional layer between the amorphous film and the underlying substrate showing silicon nano-crystalline enclosures that can lead to quantum confinement effects. Quantum confinement is suggested to be the cause of the observed

  14. Optical bandgap of ultra-thin amorphous silicon films deposited on crystalline silicon by PECVD

    Energy Technology Data Exchange (ETDEWEB)

    Abdulraheem, Yaser, E-mail: yaser.abdulraheem@kuniv.edu.kw [Electrical Engineering Department, College of Engineering and Petroleum, Kuwait University. P.O. Box 5969, 13060 Safat (Kuwait); Gordon, Ivan; Bearda, Twan; Meddeb, Hosny; Poortmans, Jozef [IMEC, Kapeldreef 75, 3001, Leuven (Belgium)

    2014-05-15

    An optical study based on spectroscopic ellipsometry, performed on ultrathin hydrogenated amorphous silicon (a-Si:H) layers, is presented in this work. Ultrathin layers of intrinsic amorphous silicon have been deposited on n-type mono-crystalline silicon (c-Si) wafers by plasma enhanced chemical vapor deposition (PECVD). The layer thicknesses along with their optical properties –including their refractive index and optical loss- were characterized by spectroscopic ellipsometry (SE) in a wavelength range from 250 nm to 850 nm. The data was fitted to a Tauc-Lorentz optical model and the fitting parameters were extracted and used to compute the refractive index, extinction coefficient and optical bandgap. Furthermore, the a-Si:H film grown on silicon was etched at a controlled rate using a TMAH solution prepared at room temperature. The optical properties along with the Tauc-Lorentz fitting parameters were extracted from the model as the film thickness was reduced. The etch rate for ultrathin a-Si:H layers in TMAH at room temperature was found to slow down drastically as the c-Si interface is approached. From the Tauc-Lorentz parameters obtained from SE, it was found that the a-Si film exhibited properties that evolved with thickness suggesting that the deposited film is non-homogeneous across its depth. It was also found that the degree of crystallinity and optical (Tauc) bandgap increased as the layers were reduced in thickness and coming closer to the c-Si substrate interface, suggesting the presence of nano-structured clusters mixed into the amorphous phase for the region close to the crystalline silicon substrate. Further results from Atomic Force Microscopy and Transmission Electron Microscopy confirmed the presence of an interfacial transitional layer between the amorphous film and the underlying substrate showing silicon nano-crystalline enclosures that can lead to quantum confinement effects. Quantum confinement is suggested to be the cause of the observed

  15. Atomic-scale disproportionation in amorphous silicon monoxide

    OpenAIRE

    Hirata, Akihiko; Kohara, Shinji; Asada, Toshihiro; Arao, Masazumi; Yogi, Chihiro; Imai, Hideto; Tan, Yongwen; Fujita, Takeshi; Chen, Mingwei

    2016-01-01

    Solid silicon monoxide is an amorphous material which has been commercialized for many functional applications. However, the amorphous structure of silicon monoxide is a long-standing question because of the uncommon valence state of silicon in the oxide. It has been deduced that amorphous silicon monoxide undergoes an unusual disproportionation by forming silicon- and silicon-dioxide-like regions. Nevertheless, the direct experimental observation is still missing. Here we report the amorphou...

  16. Amorphous Dielectric Thin Films with Extremely Low Mechanical Loss

    OpenAIRE

    Liu X; Queen D.R.; Metcalf T.H.; Karel J.E.; Hellman F.

    2015-01-01

    The ubiquitous low-energy excitations are one of the universal phenomena of amorphous solids. These excitations dominate the acoustic, dielectric, and thermal properties of structurally disordered solids. One exception has been a type of hydrogenated amorphous silicon (a-Si:H) with 1 at.% H. Using low temperature elastic and thermal measurements of electron-beam evap-orated amorphous silicon (a-Si), we show that TLS can be eliminated in this system as the films become denser and more structur...

  17. First Principles Prediction of Amorphous Phases Using Evolutionary Algorithms

    OpenAIRE

    Nahas, Suhas; Gaur, Anshu; Bhowmick, Somnath

    2016-01-01

    We discuss the efficacy of evolutionary method for the purpose of structural analysis of amorphous solids. At present ab initio molecular dynamics (MD) based melt-quench technique is used and this deterministic approach has proven to be successful to study amorphous materials. We show that a stochastic approach motivated by Darwinian evolution can also be used to simulate amorphous structures. Applying this method, in conjunction with density functional theory (DFT) based electronic, ionic an...

  18. Modelling the light induced metastable effects in amorphous silicon

    OpenAIRE

    Munyeme, G.; Chinyama, G.K.; Zeman, M.; R. E. I. Schropp; Weg, W

    2008-01-01

    We present results of computer simulations of the light induced degradation of amorphous silicon solar cells. It is now well established that when amorphous silicon is illuminated the density of dangling bond states increases. Dangling bond states produce amphoteric electronic mid-gap states which act as efficient charge trapping and recombination centres. The increase in dangling bond states causes a decrease in the performance of amorphous silicon solar cells. To show this effect, a modelli...

  19. Memory effect under pressure in low density amorphous silicon

    OpenAIRE

    Garg, Nandini; Pandey, K. K.; K. V. Shanavas; Betty, C. A.; Sharma, Surinder M

    2010-01-01

    Our investigations on porous Si show that on increase of pressure it undergoes crystalline phase transitions instead of pressure induced amorphization - claimed earlier, and the amorphous phase appears only on release of pressure. This amorphous phase, when subjected to higher pressures, transforms reversibly to a higher coordinated primitive hexagonal phase showing a kind of memory effect which may be the only example of its kind in the elemental solids. First principles calculations and the...

  20. Moringa Coagulant as a Stabilizer for Amorphous Solids: Part I

    OpenAIRE

    Bhende, Santosh; Jadhav, Namdeo

    2012-01-01

    Stabilization of amorphous state is a focal area for formulators to reap benefits related with solubility and consequently bioavailability of poorly soluble drugs. In the present work, an attempt has been made to explore the potential of moringa coagulant as an amorphous state stabilizer by investigating its role in stabilization of spray-dried (amorphous) ibuprofen, meloxicam and felodipine. Thermal studies like glass forming ability, glass transition temperature, hot stage microscopy and DS...

  1. Amorphization kinetics of Zr3Fe under electron irradiation

    International Nuclear Information System (INIS)

    Previous investigations using 40Ar ion bombardments have revealed that Zr3 Fe, which has an orthorhombic crystal structure, undergoes an irradiation-induced transformation from the crystalline to the amorphous state. In the present investigation, 0.9 MeV electron irradiations were performed at 28 - 220 K in a high-voltage electron microscope (HVEM). By measuring the onset, spread and final size of the amorphous region, factoring in the Gaussian distribution of the beam, a kinetic description of the amorphization in terms of dose, dose rate and temperature was obtained. The critical temperature for amorphization by electron irradiation was found to be ∼ 220 K, compared with 570 - 625 K for 40Ar ion irradiation. Also, the dose-to-amorphization increased exponentially with temperature. Results indicated that the rate of growth of the amorphous region under the electron beam decreased with increasing temperature and the dose-to-amorphization decreased with increasing dose rate. The size of the amorphous region saturated after a given dose, the final size decreasing with increasing temperature, and it is argued that this is related to the existence of a critical dose rate, which increases with temperature, and below which no amorphization occurs. (author). 26 refs., 6 figs

  2. Excessively High Vapor Pressure of Al-based Amorphous Alloys

    Directory of Open Access Journals (Sweden)

    Jae Im Jeong

    2015-10-01

    Full Text Available Aluminum-based amorphous alloys exhibited an abnormally high vapor pressure at their approximate glass transition temperatures. The vapor pressure was confirmed by the formation of Al nanocrystallites from condensation, which was attributed to weight loss of the amorphous alloys. The amount of weight loss varied with the amorphous alloy compositions and was inversely proportional to their glass-forming ability. The vapor pressure of the amorphous alloys around 573 K was close to the vapor pressure of crystalline Al near its melting temperature, 873 K. Our results strongly suggest the possibility of fabricating nanocrystallites or thin films by evaporation at low temperatures.

  3. Three-Terminal Amorphous Silicon Solar Cells

    OpenAIRE

    Cheng-Hung Tai; Chu-Hsuan Lin; Chih-Ming Wang; Chun-Chieh Lin

    2011-01-01

    Many defects exist within amorphous silicon since it is not crystalline. This provides recombination centers, thus reducing the efficiency of a typical a-Si solar cell. A new structure is presented in this paper: a three-terminal a-Si solar cell. The new back-to-back p-i-n/n-i-p structure increased the average electric field in a solar cell. A typical a-Si p-i-n solar cell was also simulated for comparison using the same thickness and material parameters. The 0.28 μm-thick three-terminal a-Si...

  4. Magnetoimpedance response in current annealed amorphous wires

    International Nuclear Information System (INIS)

    In this work, the magnetoimpedance (MI) effect in amorphous wires submitted to current annealing treatment in vacuum is presented. The influence of circular anisotropy and stress relaxation induced during the annealing on the impedance dependence on external magnetic field is shown. An increase in the MI ratio for the annealed wires is observed up to a maximum value which is approximately three times higher than the maximum value obtained for the as-cast wire. For high enough times of current annealing treatment a decrease in the MI ratio is observed due to the formation of crystalline phase

  5. Magnetoimpedance response in current annealed amorphous wires

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, D. [Dpto. Fisica Aplicada, Universidad de Salamanca, Plaza de la Merced s/n, 37008 Salamanca (Spain)]. E-mail: danielgg@usal.es; Raposo, V. [Dpto. Fisica Aplicada, Universidad de Salamanca, Plaza de la Merced s/n, 37008 Salamanca (Spain); Borza, F. [Wolfson Centre for Magnetics Technology, Cardiff University, New Port Road, P.O. Box 925, CF24 0YF Cardiff (United Kingdom); Montero, O. [Dpto. Fisica Aplicada, Universidad de Salamanca, Plaza de la Merced s/n, 37008 Salamanca (Spain); Iniguez, J. [Dpto. Fisica Aplicada, Universidad de Salamanca, Plaza de la Merced s/n, 37008 Salamanca (Spain)

    2006-09-15

    In this work, the magnetoimpedance (MI) effect in amorphous wires submitted to current annealing treatment in vacuum is presented. The influence of circular anisotropy and stress relaxation induced during the annealing on the impedance dependence on external magnetic field is shown. An increase in the MI ratio for the annealed wires is observed up to a maximum value which is approximately three times higher than the maximum value obtained for the as-cast wire. For high enough times of current annealing treatment a decrease in the MI ratio is observed due to the formation of crystalline phase.

  6. Inconspicuous Appeal of Amorphous Computing Systems

    Czech Academy of Sciences Publication Activity Database

    Wiedermann, Jiří

    Opava: Institute of Computer Science, Silesian University, 2014 - (Gheorghe, M.; Sosík, P.; Vavrečková, Š.), s. 15-18 ISBN 978-80-7510-036-8. [CMC15. International Conference on Membrane Computing /15./. Prague (CZ), 20.08.2014-22.08.2014] R&D Projects: GA ČR GAP202/10/1333 Institutional support: RVO:67985807 Keywords : amorphous computing * computational universality * computational complexity Subject RIV: IN - Informatics, Computer Science http://www.cs.us.es/~marper/investigacion/cmc15_proceedings.pdf#page=27

  7. Rapid Annealing Of Amorphous Hydrogenated Carbon

    Science.gov (United States)

    Alterovitz, Samuel A.; Pouch, John J.; Warner, Joseph D.

    1989-01-01

    Report describes experiments to determine effects of rapid annealing on films of amorphous hydrogenated carbon. Study represents first efforts to provide information for applications of a-C:H films where rapid thermal processing required. Major finding, annealing causes abrupt increase in absorption and concomitant decrease in optical band gap. Most of change occurs during first 20 s, continues during longer annealing times. Extend of change increases with annealing temperature. Researchers hypothesize abrupt initial change caused by loss of hydrogen, while gradual subsequent change due to polymerization of remaining carbon into crystallites or sheets of graphite. Optical band gaps of unannealed specimens on silicon substrates lower than those of specimens on quartz substrates.

  8. Amorphous computing: examples, mathematics and theory.

    Science.gov (United States)

    Stark, W Richard

    2013-01-01

    The cellular automata model was described by John von Neumann and his friends in the 1950s as a representation of information processing in multicellular tissue. With crystalline arrays of cells and synchronous activity, it missed the mark (Stark and Hughes, BioSystems 55:107-117, 2000). Recently, amorphous computing, a valid model for morphogenesis in multicellular information processing, has begun to fill the void. Through simple examples and elementary mathematics, this paper begins a computation theory for this important new direction. PMID:23946719

  9. Radiation resistance studies of amorphous silicon films

    Science.gov (United States)

    Woodyard, James R.; Payson, J. Scott

    1989-01-01

    Hydrogenated amorphous silicon thin films were irradiated with 2.00 MeV helium ions using fluences ranging from 1E11 to 1E15 cm(-2). The films were characterized using photothermal deflection spectroscopy and photoconductivity measurements. The investigations show that the radiation introduces sub-band-gap states 1.35 eV below the conduction band and the states increase supralinearly with fluence. Photoconductivity measurements suggest the density of states above the Fermi energy is not changing drastically with fluence.

  10. PHYSICAL PROPERTIES OF AMORPHOUS CVD SILICON

    OpenAIRE

    Hirose, M.

    1981-01-01

    Amorphous silicon produced from the chemical vapor decomposition of silane at ~600 °C offers a pure silicon network containing no bonded-hydrogen and involving native defects of the order of 1 x 1019 cm-3. Doped phosphorus or boron atoms in the CVD a-Si interact with the defects to reduce the gap states and the spin density as well. The mechanism of the defect compensation has been interpreted in terms of complex-defect formation through the reaction between three-fold dopant atoms and divaca...

  11. Electrochromism of amorphous ruthenium oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Se-Hee; Liu, Ping; Tracy, C. Edwin; Deb, Satyen K. [National Renewable Energy Laboratory, Center for Basic Sciences, 1617 Cole Boulevard, Golden, CO 80401 (United States); Cheong, Hyeonsik M. [Sogang University, Shinsoo-Dong, Seoul 121-742 (Korea, Republic of)

    2003-12-01

    We report on the electrochromic behavior of amorphous ruthenium oxide thin films and their electrochemical characteristics for use as counterelectrodes for electrochromic devices. Hydrous ruthenium oxide thin films were prepared by cyclic voltammetry on ITO coated glass substrates from an aqueous ruthenium chloride solution. The cyclic voltammograms of this material show the capacitive behavior including two redox reaction peaks in each cathodic and anodic scan. The ruthenium oxide thin film electrode exhibits a 50% modulation of optical transmittance at 670 nm wavelength with capacitor charge/discharge.

  12. The properties of amorphous GaN

    OpenAIRE

    Cai, Bin; Drabold, David A.

    2011-01-01

    In this paper, we present three amorphous GaN models obtained from the first principles simulation. We find that a chemically ordered continuous random network is the ideal structure for a-GaN. If we exclude the tail states, we predict a 3.0eV optical gap for 64-atom model and 2.3eV for 250-atom models. We observe a highly localized valence tail and a remarkably delocalized exponential conduction tail which we associate with different hybridization in the two tails. Based upon these results, ...

  13. Amorphous silicon crystalline silicon heterojunction solar cells

    CERN Document Server

    Fahrner, Wolfgang Rainer

    2013-01-01

    Amorphous Silicon/Crystalline Silicon Solar Cells deals with some typical properties of heterojunction solar cells, such as their history, the properties and the challenges of the cells, some important measurement tools, some simulation programs and a brief survey of the state of the art, aiming to provide an initial framework in this field and serve as a ready reference for all those interested in the subject. This book helps to ""fill in the blanks"" on heterojunction solar cells. Readers will receive a comprehensive overview of the principles, structures, processing techniques and the curre

  14. Self-Diffusion in Amorphous Silicon

    Science.gov (United States)

    Strauß, Florian; Dörrer, Lars; Geue, Thomas; Stahn, Jochen; Koutsioubas, Alexandros; Mattauch, Stefan; Schmidt, Harald

    2016-01-01

    The present Letter reports on self-diffusion in amorphous silicon. Experiments were done on 29Si/natSi heterostructures using neutron reflectometry and secondary ion mass spectrometry. The diffusivities follow the Arrhenius law in the temperature range between 550 and 700 °C with an activation energy of (4.4 ±0.3 ) eV . In comparison with single crystalline silicon the diffusivities are tremendously higher by 5 orders of magnitude at about 700 °C , which can be interpreted as the consequence of a high diffusion entropy.

  15. Solar Cells Having a Nanostructured Antireflection Layer

    DEFF Research Database (Denmark)

    2013-01-01

    An solar cell having a surface in a first material is provided, the optical device having a non-periodic nanostructure formed in the surface, the nanostructure comprising a plurality of cone -haped structures wherein the cones are distributed non-periodically on the surface and have a random height...... distribution, at least a part of the cone-shaped structures having a height of at least 100 nm. The first material may be SiC or GaN. A method of manufacturing a non-periodic nanostructured surface on a solar cell, is furthermore provided, the method comprising the steps of providing a surface comprising Si...

  16. Nanostructured transparent conducting oxide electrochromic device

    Energy Technology Data Exchange (ETDEWEB)

    Milliron, Delia; Tangirala, Ravisubhash; Llordes, Anna; Buonsanti, Raffaella; Garcia, Guillermo

    2016-05-17

    The embodiments described herein provide an electrochromic device. In an exemplary embodiment, the electrochromic device includes (1) a substrate and (2) a film supported by the substrate, where the film includes transparent conducting oxide (TCO) nanostructures. In a further embodiment, the electrochromic device further includes (a) an electrolyte, where the nanostructures are embedded in the electrolyte, resulting in an electrolyte, nanostructure mixture positioned above the substrate and (b) a counter electrode positioned above the mixture. In a further embodiment, the electrochromic device further includes a conductive coating deposited on the substrate between the substrate and the mixture. In a further embodiment, the electrochromic device further includes a second substrate positioned above the mixture.

  17. Nanostructured thin films and coatings functional properties

    CERN Document Server

    Zhang, Sam

    2010-01-01

    The second volume in ""The Handbook of Nanostructured Thin Films and Coatings"" set, this book focuses on functional properties, including optical, electronic, and electrical properties, as well as related devices and applications. It explores the large-scale fabrication of functional thin films with nanoarchitecture via chemical routes, the fabrication and characterization of SiC nanostructured/nanocomposite films, and low-dimensional nanocomposite fabrication and applications. The book also presents the properties of sol-gel-derived nanostructured thin films as well as silicon nanocrystals e

  18. Low-temperature crystallization of amorphous silicon and amorphous germanium by soft X-ray irradiation

    International Nuclear Information System (INIS)

    The low-temperature-crystallization effects of soft X-ray irradiation on the structural properties of amorphous Si and amorphous Ge films were investigated. From the differences in crystallization between Si and Ge, it was found that the effects of soft X-ray irradiation on the crystallization strongly depended on the energy band gap and energy level. The crystallization temperatures of the amorphous Si and amorphous Ge films decreased from 953 K to 853 K and 773 K to 663 K, respectively. The decrease in crystallization temperature was also related to atoms transitioning into a quasi-nucleic phase in the films. The ratio of electron excitation and migration effects to thermal effects was controlled using the storage-ring current (photon flux density). Therefore, we believe that low-temperature crystallization can be realized by controlling atomic migration through electron excitation. - Highlights: • This work investigates the crystallization mechanism for soft X-ray irradiation. • The soft X-ray crystallization depended on the energy band gap and energy level. • The decrease in the crystallization temperature for Si and Ge films was 100 K. • This decrement was related to atoms transitioning into a quasi-nucleic phase

  19. Solvent-mediated amorphous-to-crystalline transformation of nitrendipine in amorphous particle suspensions containing polymers

    DEFF Research Database (Denmark)

    Xia, Dengning; Wu, Jian-Xiong; Cui, Fude;

    2012-01-01

    The amorphous-to-crystalline transformation of nitrendipine was investigated using Raman spectroscopy and X-ray powder diffraction (XRPD). The nucleation and growth rate of crystalline nitrendipine in a medium containing poly (vinyl alcohol) (PVA) and polyethylene glycol (PEG 200) were quantitati...

  20. Biological nanostructures and applications of nanostructures in biology electrical, mechanical, and optical properties

    CERN Document Server

    Stroscio, Michael A

    2004-01-01

    Biological Nanostructures and Applications of Nanostructures in Biology: Electrical, Mechanical, and Optical Properties contains reviews and discussions of contemporary and relevant topics dealing with the interface between the science and technology of nanostructures and the science of biology. Moreover, this book supplements these past groundbreaking discoveries with discussions of promising new avenues of research that reveal the enormous potential of emerging approaches in nanobiotechnology. The topics include: This state-of-the-art survey of key developments in nanotechnology - as they ap