bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fabrication of Tungsten-Tellurite Glass Thin Films using Radio Frequency Magnetron Sputtering Method and Optical Property Characterization
Authors: Yoo Ki-Young , Shin Sanghoon , Kim Youngman , Moon Jong-Ha , Kim Jin Hyeok 
Published: April 2011

AbstractTungsten-tellurite glass thin films were fabricated by radio-frequency (rf) magnetron sputtering method at various processing parameters such as substrate temperatures, Ar/O2 processing gas flow ratio, processing pressure, and rf power from a 70TeO2-30WO3 target fabricated by solid–state sintering method. The effects of processing parameters on the growth rate, the surface morphologies, the crystallinity, and refractive indices of thin films were investigated using atomic force microscopy, X-ray diffractometer, scanning electron microscopy, and UV spectrometer. Amorphous glass thin films with a surface roughness of 4∼6 nm were obtained only at room temperature and crystalline phase were observed in all as-deposited thin films prepared at above the room temperature. The deposition rate strongly depends on the processing parameters. It increases as the rf power increases and the processing pressure decreases. Especially, it changes remarkably as varying the Ar/O2 gas flow ratio from 40sccm/0sccm to 0sccm/40sccm. When the films were formed in pure Ar atmosphere it shows a deposition rate of ∼0.2 μm /h, whereas ∼1.5 μm/h when the films was formed in pure O2 atmosphere.
Design and Fabrication of All-Polymer Photonic Devices
Authors: Callender Claire L. , Jiang Jia , Blanchetière Chantal , Noad Julian P. , Walker Robert B. , Mihailov Stephen J. , Ding Jianfu , Day Michael 
Published: April 2011

AbstractHigh quality optical waveguides have been fabricated from fluorinated poly(arylene ether ketone) materials using a standard photolithographic process. Fabrication of waveguide devices on a polymer substrate is described, including a method of end-facet preparation using excimer laser micromachining. Material issues affecting waveguide birefringence and device performance are discussed.
Dye-Doped, Polymer-Nanoparticle Gain Media for Tunable Solid-State Lasers
Authors: Duarte F. J. , James R. O. 
Published: April 2011

AbstractTunable laser action, in the visible spectrum, has been established using dye-doped, polymer-silica nanoparticle gain media. The silica nanoparticles, averaging about 12 nm in diameter, appear to be uniformly dispersed in the polymethyl methacrylate (PMMA) matrix, since the optical homogeneity of the gain medium is maintained. Using rhodamine 6G dye and 30% weight-by-weight (w/w) silica nanoparticles, laser action was established in the 567–603 nm range. At the peak wavelength (λ ∼ 580 nm) laser conversion efficiency is ∼63% at a beam divergence of 1.9 mrad (∼1.3 times the diffraction limit). The new solid-state nanocomposite gain media also exhibits a reduction in |∂n/∂T| because the thermo-optic coefficient of silica is opposite in sign to that of the PMMA polymer-host component.
Enhanced Faraday rotation in garnet films and multilayers
Authors: Kahl S. , Grishin A. M. 
Published: April 2011

AbstractFilms were prepared by pulsed laser deposition. We investigated or measured crystallinity, morphology, film-substrate interface, cracks, roughness, composition, magnetic coercivity, refractive index and extinction coefficient, and magneto-optical Faraday rotation (FR) and ellipticity. The investigations were partly performed on selected samples, and partly on two series of films on different substrates and of different thicknesses. BIG films were successfully tested for the application of magneto-optical visualization. The effect of annealing in oxygen atmosphere was also investigated - very careful annealing can increase FR by up to 20%.Periodical BIG-YIG multilayers with up to 25 single layers were designed and prepared with the purpose to enhance FR at a selected wavelength. A central BIG layer was introduced as defect layer into this one-dimensional magneto-optical photonic crystal (MOPC) and generated resonances in optical transmittance and FR at a chosen design wavelength. In a 17-layer structure, at the wavelength of 748 nm, FR was increased from–2.6 deg/μm to –6.3 deg/μm at a small reduction in transmittance from 69% to 58% as compared to a single-layer BIG film of equivalent thickness. In contrast to thick BIG films, the MOPCs did not crack. We were first to report preparation of all-garnet MOPCs and second to experimentally demonstrate the MOPC principle in magneto-optical garnets.
Frequency- and Temperature-Dependent Ferromagnetic Resonance of Co/CoO Core-Shell Nanoparticles
Authors: Wiedwald U. , Lindner J. , Spasova M. , Frait Z. , Hilgendorff M. , Giersig M. , Farle M. 
Published: April 2011

AbstractFerromagnetic Resonance experiments are used to investigate the magnetic properties of monodisperse Co/CoO core-shell nanoparticles with diameters of about 10nm. From frequency- dependent measurements at various frequencies of 9-80 GHz the g-value is determined to be 2.13 which suggests an fcc bulk-like environment of the Co atoms within the core of the particles. This result yields a direct measure of the ratio of orbital to spin magnetic moment νL/νS=0.065. Moreover, from temperature-dependent measurements of the resonance field the anisotropy energy is extracted and found much lower than the hcp bulk value.
Preparation of Silicon Carbide Nano-Particles Using a Pulsed Laser Deposition Method
Authors: Kawasaki H. , Suda Y. , Ohshima T. , Ueda T. , Nakashima S. 
Published: April 2011

AbstractWe have developed a new pulsed laser deposition technique using two Nd:YAG laser beams for the nucleation of silicon carbide (SiC) crystalline nano-particles and single crystalline SiC thin films. Transmission electron microscopy and atomic force microscopy observation suggest that several nanometer size SiC particles can be prepared by the new pulsed laser deposition (PLD) method using two Nd:YAG laser beams (1064nm and 532nm). X ray photoelectron spectroscopy measurements suggest that the silicon/carbon composition ratio of the prepared SiC thin films can be controlled by laser fluence and wavelength.
The Effects of Processing on the Morphology of Nanoparticles
Authors: Perrey Christopher R. , Deneen Julia M. , Carter C. Barry 
Published: April 2011

AbstractOne of the major challenges confronting the utilization of nanoparticles in industrial and social applications is that of producing the nanoscale materials. Of the methods of manufacturing nanoscale materials, processes involving plasmas have been shown to be cost-effective and versatile in the production of chemically diverse material. Using transmission electron microscopy, individual nanoparticles produced by a thermal plasma-based production method have been examined. The observations of these studies imply that the thermal history of the nanoparticles during formation is of great importance in the determination of the resulting nanoparticle morphology. Such results have the potential to enable the manufacturing of nanoparticles of a specific size and shape from plasmas.
Silicon Nanowire Growth at Relatively Low Processing Temperature
Authors: Kim Joondong , Ji Chunhai , Anderson Wayne A. 
Published: April 2011

AbstractThe Metal Induced Growth (MIG) of nanowires has the potential to alter the conventional lithographic techniques to provide an easier fabrication method in nanoelectronics. Our group has studied the MIG technique to synthesize poly-silicon and nano size structures. This work gave silicon nanowires of 20∼200 nm diameter, 3∼10νm length and single crystal structure. Until now, the growing of silicon nanowires has been understood by two models. One is an oxide- assisted mechanism and the other is a metal catalyst assisted mechanism. Both cases need higher growth temperatures above 900°C. We are now proposing the repeatable growth of silicon nanowires at a low processing temperature, 550∼600°C, which is the lowest silicon nanowire growth temperature without using a gas type silicon source (silane).This novel method to grow silicon nanowires has several advantages: (1) low processing temperature; (2) straight line growth; (3) single crystal structure and (4) repeatability. This Si nanowire growing mechanism is based on NiSi formation.
Effect of Carrier Gas on the Growth Rate, Growth Density, and Structure of Carbon Nanotubes
Authors: Yap Yoke Khin , Kayastha Vijaya , Hackney Steve , Dimovski Svetlana , Gogotsi Yury 
Published: April 2011

AbstractWe attempt to understand the fundamental factors that determine the growth rate of carbon nanotubes. In a series of experiments on growing multiwall carbon nanotubes (MWNTs) by thermal chemical vapor deposition, we found that the addition of carrier gas and the type of carrier gas can change the growth rate, growth density, and structures of MWNTs. We explain these results based on the dissociative adsorption of C2H2 on Fe nanoparticles and the vapor-liquid-solid (VLS) growth model. Finally, high-density, vertically aligned MWNTs were grown when decomposition and segregation rates of carbon were balanced.
A Production Method for Aligned Nanowires on Arbitrary Materials
Authors: Kunz Rainer , Adelung Rainer 
Published: April 2011

AbstractWe present a method that allows us to produce aligned metallic nanowires on almost any material. This method recently enabled us to produce interconnected platinum nanowire networks on polymeric Nafion® or gold nanowires on Teflon AF. We will explain the principle of this method by means of a reference material, the so called layered transition metal dichalcogenides (TMDC) crystals. The method is based on producing cracks in thin films as templates, using large sticking coefficient differences and long diffusion lengths. The underlying mechanism that forms the template cracks is mechanical stress. In the case of the TMDC crystals this stress is introduced in the substrate by an electronic interaction between the metal used for the nanowires and the TMDC-crystal. The large difference in the condensation coefficient is an immanent property of layered crystals for many different adsorbates. Obtained by cleavage along a so called “Van-der-Waals-gap”, surfaces of such crystals are atomically flat over hundreds of microns. As a consequence of their layered character the surfaces have no reconstruction and almost no step edges or other defects, which is the basis for the long diffusion length. In contrast, the rare defects have a very high sticking coefficient and act as excellent nucleation centers. Therefore, after metal evaporation on such surfaces in UHV, various structures can be formed in a self organized processes. We observed, e.g., clusters in fractal or geometric arrangements or large nanowire networks on the surfaces [1]. In order to understand, why the different structures form, a systematic study of the growth parameters, (nucleation, diffusion length, evaporated metal, influence of the substrate-crystal), is necessary. Therefore, we first carried out diffusion studies on these surfaces. We could show that in extreme cases (Cu on metallic TaS2) diffusion length of more than 50νm could be observed combined with a nucleation probability of almost zero. This is evident from a growth mode showing similarities with the DLA (Diffusion Limited Aggregation) growth process. In contrast, metal diffusion (Cu) on the geometrically similar surfaces on the semiconducting (WSe2) surface shows much a shorter diffusion length and no DLA growth. We suggest a model to explain the different diffusion behavior as a key to understand the different self organized structures. Learning from the TMDC crystals, we show the application on technological more important materials.
Direct Observation of Highly Polarized Non-Linear Absorption Dipole of Single Semiconductor Quantum Rods
Authors: Rothenberg Eli , Ebenstein Yuval , Kazes Miri , Banin Uri 
Published: April 2011

AbstractPolarization fluorescence microscopy was used to study the nature of the emission and nonlinear absorption dipole of single CdSe/ZnS quantum rods. Rods, with aspect ratios ranging from 2.75 to 15, showed strongly polarized emission consistent with previous one-photon studies. Non- linear excitation showed a sharp angular dependence fully consistent with the predicted two- photon absorption process. Two-photon absorption probes different transitions than linear absorption due to modified parity and angular momentum selection rules. The two-photon absorption dipole was found to be parallel to the emission polarization, and allows achieving highly orientation selective excitation of quantum rods. This is yet a further demonstration of single molecule measurements in unraveling basic principles of light-matter interaction that are otherwise masked by ensemble averaging.
Characterization of Shell Material on Colloidal CdSe/ZnS Quantum Dots
Authors: Yu Zhiheng , Guo Li , Du Hui , Krauss Todd , Silcox John 
Published: April 2011

AbstractScanning transmission electron microscopy (STEM) coupled with electron energy loss spectroscopy (EELS) was used to determine the distribution of ZnS shell material on colloidal core-shell CdSe/ZnS quantum dots (QDs). A sub-nm electron probe was placed at various locations on core-shell QDs to ascertain the chemical distribution of the shell material. While a definite shell of ZnS was detected surrounding the CdSe core, the integrated EELS signals from positions around the QD suggest the distribution of the shell material may not be uniform. A non-uniform shell implies a reduced quality of the QD surface passivation.
Optical Properties of Wurtzite GaN and ZnO Quantum Dots
Authors: Fonoberov Vladimir A. , Balandin Alexander A. 
Published: April 2011

AbstractWe have investigated exciton states in wurtzite GaN/AlN and ZnO quantum dots. A strong piezoelectric field in GaN/AlN quantum dots is found to tilt conduction and valence bands, thus pushing the electron to the top and the hole to the bottom of the GaN/AlN quantum dot. As a result, the exciton ground state energy in GaN/AlN quantum dots with heights larger than 3 nm exhibits a red shift with respect to bulk GaN energy gap. It is shown that the radiative decay time in GaN/AlN quantum dots is large and increases from 0.3 ns for quantum dots with height 1.5 nm to 1.1×103 ns for the quantum dots with height 4.5 nm. On the contrary, the electron and the hole are not separated in ZnO quantum dots. Moreover, a relatively thick “dead layer” is formed near the surface of ZnO quantum dots. As a result, the radiative decay time in ZnO quantum dots is small and decreases from 73 ps for quantum dots with diameter 1.5 nm to 29 ps for the quantum dots with diameter 6 nm.
The fabrication of self-assembling peptides into nanofiber scaffolds through molecular self-assembly
Authors: Zhao Xiaojun , Dai Jessica , Zhang Shuguang 
Published: April 2011

AbstractWe designed and fabricated a class of self-assembling peptides into nanofiber scaffolds. KLDL-12 has been shown to be a permissible nanofiber scaffold for chondrocytes in cartilage 3-D cell cultures. However, the biochemical, structural, and biophysical properties of KLDL- 12 remain unclear. We show that KLDL-12 peptides form stable β-sheet structures at different pH values and that KLDL-12 and RIDI-12 self-assemble into nanofibers. The nanofiber length, though, is sensitive to pH changes. These results not only suggest the importance of electrostatic attraction or repulsion affecting the fiber lengths but also provide us with useful information for rational design and fabrication of peptide scaffolds.
Optoelectronic detection of DNA molecules using an amorphous silicon photodetector
Authors: Fixe F. , Prazeres D.M.F. , Chu V. , Conde J.P. 
Published: April 2011

AbstractThis work demonstrates the use of an amorphous silicon (a-Si:H) photodetector to measure the density of covalently-bound DNA molecules tagged with a fluorescent molecule. This device is based on the photoconductivity of a-Si:H in a coplanar electrode configuration. Excitation of a fluorescently-tagged biomolecule with near UV/blue light results in the emission of visible light. The emitted light is then converted into an electrical signal in the photodetector, thus allowing the detection of the presence of the tagged DNA molecules. The design, fabrication and characterization of this integrated a-Si:H-based bio-detector is described. The detection limit of the present device is of the order of 20 pmol/cm2. A surface density of ≤ 30 pmol/cm2 for DNA covalently-bound to an active silica layer was measured with the a-Si:H-based bio-detector.
Development of Self-assembled Muscle-powered Microdevices
Authors: Xi Jianzhong , Schmidt Jacob J. , Montemagno Carlo D. 
Published: April 2011

AbstratAs microcomponents in engineered systems, biological muscles have unique advantages such as large force transduction, utilization of biochemical fuel, and self-assembly from single cells, over other inorganic actuators for biomedical engineering applications. Successful integration of muscles with inorganic fabricated structures and electronics promises the capability of precisely characterizing muscles' mechanical properties and fabricating self-assembled controllable autonomous structures powered by ubiquitous glucose. However, the use of extracted muscle tissue from animals on these devices is impractical and inefficient, as the tissues must be dissected and incorporated into each device by hand with crude interfaces between the biological tissue and inorganic materials. Integration of muscle with fabricated structures would be optimally achieved through self-assembling muscle cells on MEMS. The construction of self-assembled muscle-powered MEMS structures is complicated by the stringent requirements to spatially direct the cell growth, control the tight connection of these differentiated structures with MEMS structures, and enable the cells and the integrated hybrid freedom to move. Conventional and soft photolithography techniques have been extensively employed to pattern the growth of a variety of cell types and investigate their interaction with substrate in the micrometer level. However, all studies are only suitable for patterning static cells on an immobile surface, so a novel system of spatially patterning the contractible cells must be developed to enable the cells and the integrated hybrid devices to be free to move.We present a novel system of self-assembling myocytes on MEMS devices. This system has shown its capability of spatially and selectively directed growth and differentiation of myocytes into single muscle bundles, attachment of these functional bundles to MEMS structures, and the controlled partial release of the resultant hybrid devices. Two groups of self-assembled muscle-MEMS devices, force-measuring cantilevers and muscle-powered microrobots have been created. Here the further detailed studies of this system are discussed, especially the concept of the self-assembly and the material interfacial problems in this system.
Impedance-based Biosensors
Authors: Huang X. , Greve D.W. , Nausieda I. , Nguyen D. , Domach M.M. 
Published: April 2011

AbstractImpedance measurements on arrays of microelectrodes can provide information about the growth, motility, and physiology of cells growing on the electrodes. In this talk, we report recent results obtained for the growth of 3T3 mouse fibroblasts and HCT116 human cancer cells on gold electrodes approximately 0.4 mm2 in area. Cells produce a characteristic peak in the impedance change plotted as a function of frequency. With the aid of electrical modeling of the cell-electrode system, the details of the changes in the measured impedance can be correlated to the cell size, fractional electrode coverage, and cell-electrode gap. In particular, comparison of impedance measurements of these two cell types show clear differences in the growth rate and the ratio of the cell-electrode gap to the cell size. In addition to presenting these experimental results illustrating the utility of electrode impedance measurements, we will outline the issues encountered when electrodes are scaled to cell size and incorporated into a matrix-addressed array.
Fabrication of two-dimensional photonic structure of titanium dioxide with sub-micrometer resolution by deep x-ray lithography
Authors: Awazu Koichi , Fujimaki Makoto , Wang Xiaomin , Sai Akihide , Ohki Yoshimichi 
Published: April 2011

AbstractTwo dimensional photonic crystals of titanium dioxide is expected to have many advantage compared with photonic crystals of semiconductors, e.g., silicon and GaAs. For example, low optical loss in the near infrared region used for optical communication, low thermal expansion, and its refractive index which is close to that for optical fiber are attractive advantages. However, it is difficult to create micro-nano structure in titanium dioxide because micro-fabrication technique for semiconductor is not available for titanium dioxide. As the first step we calculated photonic band gap of titanium dioxide rod-slab on SiO2. Also, band gap percent against thickness of the rod-slab was examined. Finally, we confirmed the most suitable structure of 2D photonic crystals. Deep x-ray lithography technique was employed for create a very deep and precise template of PMMA. Then, liquid-phase deposition was used to faithfully deposit a tightly packed layer of titanium oxide onto the template. Finally, the template is selectively removed to obtain a photonic nano-structure. We also calculate photonic band gap on the 3D-structure of TiO2. A template for the most appropriate structure was fabricated by the method proposed by Yablonovitch. By using of the same method, it was successful to obtain 3D structure of TiO2. Refractive index of obtained TiO2 followed by heating at 700°C was determined to 2.5 which is close to that for anatase phase.
Fabricate Photonic Crystals Based on ZnS/opal System via Solvothermal Method
Authors: Cao Jieming , Chang Xin , Pan Lijia , Ji Hongmei , Liu Jinsong , Feng Jie , Zhang Fang , Wang Haiyan , Tao Jie , Xu Guoyue 
Published: April 2011

AbstractWe made photonic crystals composed of artificial opals infiltrated with ZnS semiconductor nanocrystals by using self-assembly and solvothermal methods. Scanning electron microscopy images show that the silica spheres exhibit a well-ordered arrangement and the ZnS nanocrystals grow homogenously inside the opal matrix and the as-synthesized ZnS nanocrystals reveal a cubic phase from X-ray diffraction pattern. Furthermore, the optical properties of the infiltrated opals with different ZnS filling ratio are also studied by transmission spectroscopy respectively. It is proposed that the position of the stop band can be easily designed by controlling the infiltration ratio of ZnS. These results demonstrate an effective and practical route to obtain high-performance photonic crystal structures.