bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ion Beam Assisted Square Spiral Photonic Crystal Fabrication
Authors: Sorge Jason , Summers Mark , Fleischauer Michael , Tabunshchyk Kyrylo , Kovalenko Andriy , Brett Michael 
Published: April 2011

AbstractPhotonic crystals currently hold exciting potential in waveguiding applications with the ability to greatly reduce waveguide bend radii, allowing for the realization of photonic networks with increased complexity and device density. Square spiral photonic crystals are comprised of periodic arrays of slanted cylindrical columns with periodic abrupt 90° changes in the column growth direction. The abrupt changes produce elbows which correspond to points in the three-dimensional diamond lattice, which are commonly referred to as diamond:n photonic crystal structures based on the nth nearest neighbor lattice point between column arms. The diamond:n structures are characterized by four parameters: column separation, spiral pitch, column diameter, and column growth angle. These structures have been shown theoretically to have a three-dimensional relative bandgap of approximately 15% for a direct silicon diamond:1 structure and approximately 24% for an inverse silicon diamond:5 structure with circular column cross sections. Silicon square spiral photonic crystals can be grown by a single-step thin film deposition process known as glancing angle deposition (GLAD), which utilizes rotation of lithographically patterned substrates and advanced control algorithms. While using GLAD to grow square spiral photonic crystals in a single-step process is desirable, it does have inherent limitations. Physical vapor deposited films deposited at oblique incidence angles form columns with angle ≤ 60° relative to the substrate normal. This deviates from the optimal diamond:1 and diamond:5 structures which require film growth angles of approximately 64° and 74°, respectively. Here we present SEM images of periodic silicon square spiral films grown with a vapor source incidence angle of 85° that indicate an average column tilt angle of 57˚ for films grown with the basic GLAD process and an average column tilt angle between 61˚ and 65˚ using an ion-assisted GLAD process. Photonic simulations indicating that square spiral films with complete three-dimensional photonic bandgaps are only achievable via ion-assisted GLAD are also presented.
Three-Dimensional Electromagnetic Metamaterials with Non-Maxwellian Effective Fields
Authors: Shin Jonghwa , Shen Jung-Tsung , Fan Shanhui 
Published: April 2011

AbstractIt is commonly assumed that the long-wavelength limit of a metamaterial can always be described in terms of effective permeability and permittivity tensors. Here we report that this assumption is not necessary–there exists a new class of metamaterial consisting of several interlocking disconnected metal networks, for which the effective long-wavelength theory is local, but the effective field is non-Maxwellian, and possesses much more internal degrees of freedom than effective Maxwellian fields in a local homogeneous medium.
Theory of Thermal Emissivity and Enhanced Absorption in Sub-wavelength Metallo-Dielectric Photonic Crystals
Authors: Biswas Rana , Puscasu Irina , Pralle Martin , McNeal Martin , Greenwald Anton , Daly James , Johnson Edward , Neginhal Srinivas , Ding Changgeng 
Published: April 2011

AbstractMetallo-dielectric photonic crystals are sharp thermal emitters at infrared wavelengths, and are being employed in sensors. We describe the theory of thermal emission and enhanced absorption in these photonic crystals using a scattering matrix approach, where Maxwell's equations are solved in Fourier space. A sub-wavelength hole array in a metal layer is coupled to a two-dimensional photonic crystal of the same periodicity in these metallo-dielectric photonic crystals. The sub-wavelength hole array has an enhanced transmission mode that couples to a weakly guided mode of the photonic crystal having similar modal character. The transmissive mode of the hole array is absorbed by the photonic crystal to create a sharp absorption and reflective minimum. The enhanced absorption is investigated in different lattice symmetries.
Picosecond Polarisation Detector for Infrared and Terahertz Radiation
Authors: Weber Wolfgang , Kiermaier Josef , Danilov Sergey N. , Schuh Dieter , Gerl Christian , Wegscheider Werner , Bougeard Dominique , Abstreiter Gerhard , Prettl Wilhelm , Ganichev Sergey D. 
Published: April 2011

AbstractWe report on a room temperature detector of infrared/terahertz laser radiation allowing to measure and characterized the radiation polarization state with picosecond time resolution.
Selection of Optimum Nonlinear Crystals for Efficient Parametric Generation and Sensitive Detection of Monochromatic ns THz Pulses
Authors: Ding Yujie J. 
Published: April 2011

AbstractWe report our recent progress made on the development of widely-tunable monochromatic THz sources. They have been realized based on difference-frequency generation (DFG) in GaSe, ZnGeP2, and GaP crystals, respectively. Using a GaSe crystal, the output wavelength was tuned continuously in the range from 66.5 µm to 5664 µm (from 150 cm-1 to 1.77 cm-1) with the peak power reaching 389 W. Such a high peak power corresponds to a conversion efficiency of about 0.1% (a photon conversion efficiency of 19%). A further optimization on the THz beam parameter may result in an output peak power of a few kW. Within the range of 100-250 µm the output peak powers were higher than 100 W. We have also investigated THz frequency upconversion in GaSe, ZnGeP2, and GaP crystals. Such a parametric process has a potential for detecting THz pulses at room temperature or just using a thermoelectric cooler. The minimum detectable energy per pulse was measured to be 245 pJ, which corresponds to a noise equivalent energy of 77.5 . A further optimization of the process can reduce this value down to 1 .
Alternative Catalysts For Si-Technology Compatible Growth Of Si Nanowires
Authors: Iacopi Francesca , Vereecken Philippe M , Schaekers Marc , Caymax Matty , Moelans Nele , Blanpain Bart , Detavernier Christophe , D'Haen Jan , Griffiths Hefin 
Published: April 2011

AbstractThe use of Au nanoparticles as catalysts for growth of Si nanowires poses fundamental reliability concerns for applications in Si semiconductor technology. In this work we show that the choice of catalysts can be broadened when the need for catalytic precursor dissociation is eliminated. However, the requirements for selective deposition in a gas phase transport -limited regime become stringent. When competing deposition of amorphous Si can bury the particles faster than the incubation time for VLS growth, no nanowire growth will be initiated. We show that the use of a catalyst such as In, already in a liquid form at the growth temperature, is effective. Therefore, the choice of VLS catalysts among the low melting point metals from the III, IV and V groups is suggested.
Zero Valley Splitting at Zero Magnetic Field for Strained Si/SiGe Quantum Wells
Authors: Lee Seungwon , von Allmen Paul 
Published: April 2011

AbstractThe electronic structure for a strained silicon quantum well grown on a tilted SiGe substrate is calculated using an empirical tight-binding method. For a zero substrate tilt angle the two lowest minima of the conduction band define a non-zero valley splitting at the center of the Brillouin zone. A finite tilt angle for the substrate results in displacing the two lowest conduction band minima to finite k0 and -k0 in the Brillouin zone with equal energy. The vanishing of the valley splitting for quantum wells grown on tilted substrates is found to be a direct consequence of the periodicity of the steps at the interfaces between the quantum well and the buffer materials.
Phonon Spectra and Thermodynamic Properties Of Crystalline Nanowires
Authors: Ilic Dušan , Vucenovic Siniša , Jacimovski Stevo , Zoric Vojkan , Šetrajcic Jovan 
Published: April 2011

AbstractPhonon spectra and allowed phonon states, as well as thermodynamic characteristics of nanowires of simple cubic crystalline structure, are analyzed using the method of two-time dependent Green's functions, adjusted to bounded crystalline structures. Poles of Green's functions, defining phonon spectra, can be found by solving of the secular equation. For different boundary parameters, this problem is presented graphically. The presence of boundaries as well as the change of boundary parameters leads to appearance of new properties of low dimensional structures (thin film and nanowire). The most important feature is that beside allowed energy zones (which are continuous as in the bulk structure), zones of forbidden states appear. Different values of boundary parameters lead to appearance of lower and upper energy gaps, or dispersion branches spreading out of bulk energy zone. The correlation with spectra of phonons in corresponding unbounded structures is maintained in the work. Determination of phonon spectra and allowed phonon energies has great importance for kinetic and thermodynamic properties of semiconductive nanostructures and devices. The temperature behavior of nanowire thermal capacitance is compared to that of bulk structures. It is shown that at extremely low temperature nanowire thermal capacitance is considerably lower than the thermal capacitance of bulk sample. It was discussed what are the consequences of this fact to the thermal, conducting and superconducting properties of materials.
Platinum Nanostructure Growth Using Self-Assembled Fluorocarbon Structure
Authors: Lee Sang Hwui , Liu Zhengchun , McMahon J. Jay , Lu Jian-Qiang 
Published: April 2011

AbstractWe report on a novel approach to grow platinum (Pt) nanostructure using a self-assembled fluorocarbon structure as a template. A ring-type structure of fluorocarbon residues forms during the reactive ion etching (RIE) of SiO2 using trifluoromethane (CHF3) and oxygen as etching gases. Typical dimensions of the ring-type fluorocarbon structure are found to be ∼50 nm in diameter, ∼10 nm in wall thickness, and ∼50 nm in height in this study. Platinum nanostructure up to 100 nm in height and 50 nm in diameter are grown on the template using a low-cost thin film sputter coater for 3 minutes. The morphology and growth mechanism of fluorocarbon structure and platinum nanostructure are discussed. This work provides a simple approach to platinum nanostructure growth for a fuel-cell application.
Modeling the Carrier Mobility in Nanowire Channel FET
Authors: Prost Werner , Blekker Kai , Do Quoc-Thai , Regolin Ingo , Müller Sven , Stichtenoth Daniel , Wegener Katharina , Ronning Carsten , Tegude Franz-Josef 
Published: April 2011

AbstractWe report on the extraction of carrier type, and mobility in semiconductor nanowires by adopting experimental nanowire field-effect transistor device data to a long channel MISFET device model. Numerous field-effect transistors were fabricated using n-InAs nanowires of a diameter of 50 nm as a channel. The I-V data of devices were analyzed at low to medium drain current in order to reduce the effect of extrinsic resistances. The gate capacitance is determined by an electro-static field simulation tool. The carrier mobility remains as the only parameter to fit experimental to modeled device data. The electron mobility in n-InAs nanowires is evaluated to µ = 13,000 cm2/Vs while for comparison n-ZnO nanowires exhibit a mobility of 800 cm2/Vs.
Carbon Nanotube Free-Standing Film of Pt/MWNTs as a Bifunctional Component in Hydrogen Proton Exchange Membrane Fuel Cells
Authors: Tang Jason M. , Jensen Kurt , Larsen Paul , Li Wenzhen , Itkis Mikhail E. , Yan Yushan , Haddon Robert C. 
Published: April 2011

AbstractConventional fuel cell architecture on one side of the membrane electrode assembly consists of a carbon backing layer, hydrophobic microporous layer (MPL), and a catalyst layer, which is in contact with the solid proton exchange membrane. Pt nanoparticles are deposited onto multi-walled carbon nanotubes (Pt/MWNTs) and a free-standing film of Pt/MWNTs is fabricated to act as the MPL and the catalyst layer in hydrogen fuel cells. The free-standing film of Pt/MWNTs condenses two functions into one bifunctional layer that simplifies the fuel cell fabrication procedure. Fuel cell polarization performance improves when using the free-standing film of Pt/MWNTs without the MPL resulting in a higher peak performance of 1.2 W/cm2 in comparison with 1.0 W/cm2 when in the presence of a MPL.
Carbon Nanotube Based Electrically Conductive and Optically Transparent Thin Films
Authors: Li Zhongrui , Dervishi Enkeleda , Saini Viney , Biris Alexandru R. , Lupu Dan , Xu Yang , Biris Alexandru Sorin 
Published: April 2011

AbstractHighly electrically conductive and optically transparent thin films were fabricated on conventional glass substrates using different purified carbon nanotubes, single-wall (SWNT), double-wall (DWNT), and multi-wall (MWNT) carbon nanotubes. The starting carbon nanotube materials were first made into homogenous solution with either sodium cholate or dimethylformamide. Two different fabrication approaches, airbrushing and membrane filtration methods, were used and compared. The chemical modification of thionyl chloride was employed to further improve the optical and electric performance of the SWNT films. Additionally, the temperature dependence of the resistance measured on carbon nanotube networks has been investigated.
Mechanical Properties of Carbon Nanotube Reinforced Polycarbonate at Cryogenic Temperature
Authors: Oliver Anita , Mbaruku Abdallah L. , Schwartz Justin 
Published: April 2011

AbstractCarbon nanotube (CNT) reinforced polymers are of high interest for various industries due to their unique mechanical and electrical properties. Most research has been done at room temperature (RT), but little is known about properties at cryogenic temperature. This paper presents results on CNT-polycarbonate (PC) composites with respect to mechanical properties at 77 K in comparison with RT. CNT-PC composites with 0wt% (neat), 0.1wt%, and 1.0wt% CNTs have been studied. Results imply that the CNT effects are more obvious at low temperature and are seen in the form of serrations in the stress-strain plot. No significant difference has been noticed between the neat and reinforced samples at either temperature. However, it was determined that the strength increases drastically while the elongation decreases at low temperature as compared to RT. SEM images confirm that the samples at low temperature exhibit brittle failure. Additionally, it can be seen that at low temperature the nanotubes align with the direction of tensile force while the nanotubes at RT align with the sample surface.
Gas Pressure Sensor Based on PECVD Grown Carbon Nanotubes
Authors: Ficek Richard , Elias Marek , Zajickova Lenka , Jasek Ondrej , Vrba Radimir 
Published: April 2011

AbstractIn present paper we describe development and manufacturing of the pressure sensor based on electron field emission from carbon nanotubes (CNTs). The sensor consisted of two parts, silicon membrane as an anode and multiwalled CNTs on a silicon cathode, creating a vacuum micro-chamber. Both electrodes were fabricated from the silicon single crystal (Si) wafer of the orientation (<100>) doped by phosphorus. The CNTs were grown by plasma enhanced CVD using iron catalyst in atmospheric pressure microwave torch. The catalyst was patterned into the area corresponding to the membrane dimensions. The thin CNTs with the diameter about 80 nm were straight standing perpendicularly to the substrate due to a crowding effect. In order to find the threshold current the emission characteristics of prepared sensors were measured.
Carbon Felt/Carbon Nanotubes/Pani as pH Sensor
Authors: Silva Glaucio Ribeiro , Matsubara Elaine Yoshiko , Corio Paola , Rosolen Jose Mauricio , Mulato Marcelo 
Published: April 2011

AbstractThis work proposes the use of the composite carbon felt/carbon nanotube/Polyaniline as an alternative for applications as a pH sensor device. The carbon felt/carbon nanotube is an electronic conductivity material that was obtained from polymer felt (poliacrilonitrile felt) using oxidation and carbonization processes. The cup-stacked and bamboo-like tubes were grown on the fibers of carbon felt by chemical vapor decomposition method. The sensor was obtained by incorporating polyaniline (Pani) on the nanotubes present on the fibers of carbon felt/carbon nanotubes composite. The measuring process uses an EGFET (Extended Gate Field Effect Transistors) configuration, which is a derivation of the ISFET (Ion Sensitive Field Effect Transistor) - that is basically a chemical semiconductor sensor. The drain-current versus source-drain voltage is presented for varying pH concentrations from 2 up to 12.
High-Aspect-Ratio Micromachining of Fluoropolymers Using Focused Ion Beam
Authors: Matsui Yoshinori , Miyoshi Nozomi , Oshima Akihiro , Seki Shu , Washio Masakazu , Tagawa Seiichi 
Published: April 2011

AbstractPoly(tetrafluoroethylene) (PTFE) microstructure with high aspect ratio (> 200) and without solid debris along the edge was fabricated with high etch rate by using FIB. Gasification of PTFE by FIB is responsible for the high aspect ratio, the high etch rate, and the no solid debris. Roughness of etched surface of the PTFE increases with fluence, although edge of the etched area has good profiles. The etch mechanism seems to be complicated.
Ion Beam-induced Quantum Dot Synthesis in Glass
Authors: Bernas Harry , Espiau de Lamaëstre Roch 
Published: April 2011

AbstractIrradiation-induced processes are often considered only in their nonequilibrium aspects. The purpose of this brief review is to show that chemistry, and particularly redox properties, play a major role in the thermal evolution of such systems and generally cannot, therefore, be neglected. This is exemplified by the synthesis of Ag nanoclusters in glasses and silica, under both low (gamma-ray) and high (MeV ion) deposited energy density irradiation conditions. The nanocluster formation mechanism is shown to be similar to the latent image formation process in photography. The corresponding information was used to control nucleation and growth of PbS clusters in glasses, leading to promising optical properties. In the course of these studies, we also showed that lognormal size distributions characterize the absence of information on the nanocluster formation process.
Ion Bombardment Improvement on Thermoelectric Properties of Multilayered Bi2Te3/Sb2Te3 Deposited by Magnetron Sputtering
Authors: Zheng Bangke , Budak S. , Chhay B. , Zimmerman R. L. , ILA D. 
Published: April 2011

AbstractIn order to keep the stoichemistry of Bi2Te3 and Sb2Te3 so as to keep the electrical and thermal conductivity advantage of the layered structure of bulk Bi2Te3 and Sb2Te3 in each period of the superlattice, magnetron sputtering, which is operated at relatively low temperature, was used to deposit multiplayer Bi2Te3/Sb2Te3 thermoelectric superlattice device. The two guns in our magnetron sputtering device is oriented at a certain angle to get off-axis plasma plume, which will form lattice with preferential orientation for electrical conductivity in each layer. The super lattice was then bombarded by MeV Si ions with different fluence in order to form nanoscale cluster quantum dot-like structures. In addition to the effect of quantum well confinement of the phonon transmission, the nanoscale clusters produced by the bombardment of ion beam further adversely affect the thermal conductivity. The defect and disorder in the lattice caused by bombardment and the grain boundary of these nanoscale clusters increase the scattering of phonon and increase the chance of the inelastic interaction of phonon and the annihilation of phonon, this limits phonon mean free path. Phonons are chiefly absorbed and dissipated along the lattice, therefore reduces the cross plane thermal conductivity, The increases of the electron density of state in the miniband of nanoscale cluster quantum dot-like structure formed by bombardment also increases Seebeck coefficient, and the electrical conductivity. Eventually, the thermo-electric figure of merit of superlattice films increases.
Nanoscale Surface Modification of UltraHigh Molecular Weight Polyethylene (UHMWPE) Samples with the W + C Ion Implantation
Authors: Urkac E. Sokullu , Oztarhan A. , Tihminlioglu F. , Kaya N. , Budak S. , Chhay B. , Muntele C. , OKs E. , Nikolaev A. , ILA D. 
Published: April 2011

AbstractIn this work, Ultra High Molecular Weight Poly Ethylene (UHMWPE) samples were implanted with W + C ion by using Metal-Vapour Vacuum Arc (MEVVA) ion implantation technique. Samples were implanted with W and C atoms with a fluence of 1017ion/cm2 and extraction voltage of 30 kV. Mechanism underlies this modification characterized with ATR-FTIR, UV-VIS-NIR Spectrum and Rutherford Backscattering Spectrometry (RBS). Surface morphology of implanted and unimplanted samples were examined in nanoscale with AFM.
MeV Ion-Beam Bombardment Effects on The Thermoelectric Figures of Merit of Zn4Sb3 and ZrNiSn-Based half-heusler compounds
Authors: Budak S. , Guner S. , Muntele C. , Smith C. C. , Zheng B. , Zimmerman R. L. , ILA D. 
Published: April 2011

AbstractSemiconducting â-Zn4Sb3and ZrNiSn-based half-heusler compound thin films were prepared by co-evaporation for the application of thermoelectric (TE) materials. High-purity solid zinc and antimony were evaporated by electron beam to grow the â-Zn4Sb3thin film while high-purity zirconium powder and nickel tin powders were evaporated by electron beam to grow the ZrNiSn-based half-heusler compound thin film. Rutherford backscattering spectrometry (RBS) was used to analyze the composition of the thin films. The grown thin films were subjected to 5 MeV Si ions bombardments for generation of nanostructures in the films. We measured the thermal conductivity, Seebeck coefficient, and electrical conductivity of these two systems before and after 5 MeV Si ions beam bombardments. The two material systems have been identified as promising TE materials for the application of thermal-to-electrical energy conversion, but the efficiency still limits their applications. The electronic energy deposited due to ionization in the track of MeV ion beam can cause localized crystallization. The nanostructures produced by MeV ion beam can cause significant change in both the electrical and the thermal conductivity of thin films, thereby improving the efficiency. We used the 3ù-method measurement system to measure the cross-plane thermal conductivity ,the Van der Pauw measurement system to measure the cross-plane electrical conductivity, and the Seebeck-coefficient measurement system to measure the cross-plane Seebeck coefficient. The thermoelectric figures of merit of the two material systems were then derived by calculations using the measurement results. The MeV ion-beam bombardment was found to decrease the thermal conductivity of thin films and increase the efficiency of thermal-to-electrical energy conversion.
High Resolution Thermal Imaging of Integrated Circuits
Authors: Tessier Gilles , Bardoux Mathieu , Filloy Céline , Fournier Danièle 
Published: April 2011

AbstractThermoreflectance is an non contact optical method using the local reflectivity variations induced by heating to infer temperature mappings, and can be conducted at virtually any wavelength. In the visible, the technique is now well established. It can probe temperatures through several micrometers of transparent encapsulation layers, with sub-micron spatial resolution and 100 mK thermal resolution. In the ultraviolet range, dielectric encapsulation layers are opaque and thermoreflectance gives access to the surface temperature. In the near infrared, thermoreflectance is an interesting solution to examine chips turned upside down, since these wavelengths can penetrate through silicon substrates and give access to the temperature of the active layers themselves. Here, we explore the possibilities of each wavelength range and detail the CCD-based thermal imaging tools dedicated to the high resolution inspection of integrated circuits.