Bio-inspired Fabrication of Complex Hierarchical Structure in Silicon.

PubMed

Gao, Yang; Peng, Zhengchun; Shi, Tielin; Tan, Xianhua; Zhang, Deqin; Huang, Qiang; Zou, Chuanping; Liao, Guanglan

2015-08-01

In this paper, we developed a top-down method to fabricate complex three dimensional silicon structure, which was inspired by the hierarchical micro/nanostructure of the Morpho butterfly scales. The fabrication procedure includes photolithography, metal masking, and both dry and wet etching techniques. First, microscale photoresist grating pattern was formed on the silicon (111) wafer. Trenches with controllable rippled structures on the sidewalls were etched by inductively coupled plasma reactive ion etching Bosch process. Then, Cr film was angled deposited on the bottom of the ripples by electron beam evaporation, followed by anisotropic wet etching of the silicon. The simple fabrication method results in large scale hierarchical structure on a silicon wafer. The fabricated Si structure has multiple layers with uniform thickness of hundreds nanometers. We conducted both light reflection and heat transfer experiments on this structure. They exhibited excellent antireflection performance for polarized ultraviolet, visible and near infrared wavelengths. And the heat flux of the structure was significantly enhanced. As such, we believe that these bio-inspired hierarchical silicon structure will have promising applications in photovoltaics, sensor technology and photonic crystal devices.

Single crystal functional oxides on silicon

PubMed Central

Bakaul, Saidur Rahman; Serrao, Claudy Rayan; Lee, Michelle; Yeung, Chun Wing; Sarker, Asis; Hsu, Shang-Lin; Yadav, Ajay Kumar; Dedon, Liv; You, Long; Khan, Asif Islam; Clarkson, James David; Hu, Chenming; Ramesh, Ramamoorthy; Salahuddin, Sayeef

2016-01-01

Single-crystalline thin films of complex oxides show a rich variety of functional properties such as ferroelectricity, piezoelectricity, ferro and antiferromagnetism and so on that have the potential for completely new electronic applications. Direct synthesis of such oxides on silicon remains challenging because of the fundamental crystal chemistry and mechanical incompatibility of dissimilar interfaces. Here we report integration of thin (down to one unit cell) single crystalline, complex oxide films onto silicon substrates, by epitaxial transfer at room temperature. In a field-effect transistor using a transferred lead zirconate titanate layer as the gate insulator, we demonstrate direct reversible control of the semiconductor channel charge with polarization state. These results represent the realization of long pursued but yet to be demonstrated single-crystal functional oxides on-demand on silicon. PMID:26853112

Photochemical Reactions of (n(5)-Pentamethylcyclpentadienyl)-Dicarbonyliron-Alkyl and -Silyl Complexes: Reversible Ethylene Insertion into an Iron-Silicon Bond and Implications for the Mechanism of Transition Metal-Catalyzed Hydrosilation of Alkenes.

DTIC Science & Technology

1985-12-11

RD-R162 462 PHOTOCHEMICAL REACTIONS OF(N(S)-P NTANETNYLCVCLPENTADIENYL)-DICARRONVLIR.. (U) MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY...34 Photochemical Reactions of (n5-Pentamethylcyclpentadienyl)- Dicarbonyliron-Alkyl and -Silyl Complexes: Reversible Ethylene Insertion into an Iron-Silicon Bond...Chemical Society) PHOTOCHEMICAL REACTIONS OF (n5-PENTAMETHYLCYCLOPENTADIENYL)- DICARBONYLIRON-ALKYL AND -SILYL COMPLEXES: REVERSIBLE ETHYLENE INSERTION INTO

Effects of surface nanostructuring and impurity doping on ultrafast carrier dynamics of silicon photovoltaic cells: a pump-probe study

NASA Astrophysics Data System (ADS)

Chen, Tianyu; Nam, Yoon-Ho; Wang, Xinke; Han, Peng; Sun, Wenfeng; Feng, Shengfei; Ye, Jiasheng; Song, Jae-Won; Lee, Jung-Ho; Zhang, Chao; Zhang, Yan

2018-01-01

We present femtosecond optical pump-terahertz probe studies on the ultrafast dynamical processes of photo-generated charge carriers in silicon photovoltaic cells with various nanostructured surfaces and doping densities. The pump-probe measurements provide direct insight on the lifetime of photo-generated carriers, frequency-dependent complex dielectric response along with photoconductivity of silicon photovoltaic cells excited by optical pump pulses. A lifetime of photo-generated carriers of tens of nanosecond is identified from the time-dependent pump-induced attenuation of the terahertz transmission. In addition, we find a large value of the imaginary part of the dielectric function and of the real part of the photoconductivity in silicon photovoltaic cells with micron length nanowires. We attribute these findings to the result of defect-enhanced electron-photon interactions. Moreover, doping densities of phosphorous impurities in silicon photovoltaic cells are also quantified using the Drude-Smith model with our measured frequency-dependent complex photoconductivities.

Hybrid Integration of Solid-State Quantum Emitters on a Silicon Photonic Chip.

PubMed

Kim, Je-Hyung; Aghaeimeibodi, Shahriar; Richardson, Christopher J K; Leavitt, Richard P; Englund, Dirk; Waks, Edo

2017-12-13

Scalable quantum photonic systems require efficient single photon sources coupled to integrated photonic devices. Solid-state quantum emitters can generate single photons with high efficiency, while silicon photonic circuits can manipulate them in an integrated device structure. Combining these two material platforms could, therefore, significantly increase the complexity of integrated quantum photonic devices. Here, we demonstrate hybrid integration of solid-state quantum emitters to a silicon photonic device. We develop a pick-and-place technique that can position epitaxially grown InAs/InP quantum dots emitting at telecom wavelengths on a silicon photonic chip deterministically with nanoscale precision. We employ an adiabatic tapering approach to transfer the emission from the quantum dots to the waveguide with high efficiency. We also incorporate an on-chip silicon-photonic beamsplitter to perform a Hanbury-Brown and Twiss measurement. Our approach could enable integration of precharacterized III-V quantum photonic devices into large-scale photonic structures to enable complex devices composed of many emitters and photons.

Silicon oxidation in fluoride solutions

NASA Technical Reports Server (NTRS)

Sancier, K. M.; Kapur, V.

1980-01-01

Silicon is produced in a NaF, Na2SiF6, and Na matrix when SiF4 is reduced by metallic sodium. Hydrogen is evolved during acid leaching to separate the silicon from the accompanying reaction products, NaF and Na2SiF6. The hydrogen evolution reaction was studied under conditions simulating leaching conditions by making suspensions of the dry silicon powder in aqueous fluoride solutions. The mechanism for the hydrogen evolution is discussed in terms of spontaneous oxidation of silicon resulting from the cooperative effects of (1) elemental sodium in the silicon that reacts with water to remove a protective silica layer, leaving clean reactive silicon, and (2) fluoride in solution that complexes with the oxidized silicon in solution and retards formation of a protective hydrous oxide gel.

Modeling the high-frequency complex modulus of silicone rubber using standing Lamb waves and an inverse finite element method.

PubMed

Jonsson, Ulf; Lindahl, Olof; Andersson, Britt

2014-12-01

To gain an understanding of the high-frequency elastic properties of silicone rubber, a finite element model of a cylindrical piezoelectric element, in contact with a silicone rubber disk, was constructed. The frequency-dependent elastic modulus of the silicone rubber was modeled by a fourparameter fractional derivative viscoelastic model in the 100 to 250 kHz frequency range. The calculations were carried out in the range of the first radial resonance frequency of the sensor. At the resonance, the hyperelastic effect of the silicone rubber was modeled by a hyperelastic compensating function. The calculated response was matched to the measured response by using the transitional peaks in the impedance spectrum that originates from the switching of standing Lamb wave modes in the silicone rubber. To validate the results, the impedance responses of three 5-mm-thick silicone rubber disks, with different radial lengths, were measured. The calculated and measured transitional frequencies have been compared in detail. The comparison showed very good agreement, with average relative differences of 0.7%, 0.6%, and 0.7% for the silicone rubber samples with radial lengths of 38.0, 21.4, and 11.0 mm, respectively. The average complex elastic moduli of the samples were (0.97 + 0.009i) GPa at 100 kHz and (0.97 + 0.005i) GPa at 250 kHz.

JAGUAR Procedures for Detonation Behavior of Silicon Containing Explosives

NASA Astrophysics Data System (ADS)

Stiel, Leonard; Baker, Ernest; Capellos, Christos; Poulos, William; Pincay, Jack

2007-06-01

Improved relationships for the thermodynamic properties of solid and liquid silicon and silicon oxide for use with JAGUAR thermo-chemical equation of state routines were developed in this study. Analyses of experimental melting temperature curves for silicon and silicon oxide indicated complex phase behavior and that improved coefficients were required for solid and liquid thermodynamic properties. Advanced optimization routines were utilized in conjunction with the experimental melting point data to establish volumetric coefficients for these substances. The new property libraries resulted in agreement with available experimental values, including Hugoniot data at elevated pressures. Detonation properties were calculated with JAGUAR using the revised property libraries for silicon containing explosives. Constants of the JWLB equation of state were established for varying extent of silicon reaction. Supporting thermal heat transfer analyses were conducted for varying silicon particle sizes to establish characteristic times for melting and silicon reaction.

Corrosion Characteristics of Silicon Carbide and Silicon Nitride

PubMed Central

Munro, R. G.; Dapkunas, S. J.

1993-01-01

The present work is a review of the substantial effort that has been made to measure and understand the effects of corrosion with respect to the properties, performance, and durability of various forms of silicon carbide and silicon nitride. The review encompasses corrosion in diverse environments, usually at temperatures of 1000 °C or higher. The environments include dry and moist oxygen, mixtures of hot gaseous vapors, molten salts, molten metals, and complex environments pertaining to coal ashes and slags. PMID:28053489

Three-dimensional crossbar arrays of self-rectifying Si/SiO 2/Si memristors

DOE PAGES

Li, Can; Han, Lili; Jiang, Hao; ...

2017-06-05

Memristors are promising building blocks for the next generation memory, unconventional computing systems and beyond. Currently common materials used to build memristors are not necessarily compatible with the silicon dominant complementary metal-oxide-semiconductor (CMOS) technology. Furthermore, external selector devices or circuits are usually required in order for large memristor arrays to function properly, resulting in increased circuit complexity. Here we demonstrate fully CMOS-compatible, all-silicon based and self-rectifying memristors that negate the need for external selectors in large arrays. It consists of p- and n-type doped single crystalline silicon electrodes and a thin chemically produced silicon oxide switching layer. The device exhibitsmore » repeatable resistance switching behavior with high rectifying ratio (10 5), high ON/OFF conductance ratio (10 4) and attractive retention at 300 °C. We further build a 5-layer 3-dimensional (3D) crossbar array of 100 nm memristors by stacking fluid supported silicon membranes. The CMOS compatibility and self-rectifying behavior open up opportunities for mass production of memristor arrays and 3D hybrid circuits on full-wafer scale silicon and flexible substrates without increasing circuit complexity.« less

Synthesis, characterization and functionalization of silicon nanoparticle based hybrid nanomaterials for photovoltaic and biological applications

NASA Astrophysics Data System (ADS)

Xu, Zejing

Silicon nanoparticles are attractive candidates for biological, photovoltaic and energy storage applications due to their size dependent optoelectronic properties. These include tunable light emission, high brightness, and stability against photo-bleaching relative to organic dyes (see Chapter 1). The preparation and characterization of silicon nanoparticle based hybrid nanomaterials and their relevance to photovoltaic and biological applications are described. The surface-passivated silicon nanoparticles were produced in one step from the reactive high-energy ball milling (RHEBM) of silicon wafers with various organic ligands. The surface structure and optical properties of the passivated silicon nanoparticles were systematically characterized. Fast approaches for purifying and at the same time size separating the silicon nanoparticles using a gravity GPC column were developed. The hydrodynamic diameter and size distribution of these size-separated silicon nanoparticles were determined using GPC and Diffusion Ordered NMR Spectroscopy (DOSY) as fast, reliable alternative approaches to TEM. Water soluble silicon nanoparticles were synthesized by grafting PEG polymers onto functionalized silicon nanoparticles with distal alkyne or azide moieties. The surface-functionalized silicon nanoparticles were produced from the reactive high-energy ball milling (RHEBM) of silicon wafers with a mixture of either 5-chloro-1-pentyne in 1-pentyne or 1,7 octadiyne in 1-hexyne to afford air and water stable chloroalkyl or alkynyl terminated nanoparticles, respectively. Nanoparticles with the ω-chloroalkyl substituents were easily converted to ω-azidoalkyl groups through the reaction of the silicon nanoparticles with sodium azide in DMF. The azido terminated nanoparticles were then grafted with monoalkynyl-PEG polymers using a copper catalyzed alkyne-azide cycloaddition (CuAAC) reaction to afford core-shell silicon nanoparticles with a covalently attached PEG shell. Covalently linked silicon nanoparticle clusters were synthesized via the CuAAC "click" reaction of functional silicon nanoparticles with α,ω-functional PEG polymers of various lengths. Dynamic light scattering studies show that the flexible globular nanoparticle arrays undergo a solvent dependent change in volume (ethanol> dichloromethane> toluene) similar in behavior to hydrogel nanocomposites. A novel light-harvesting complex and artificial photosynthetic material based on silicon nanoparticles was designed and synthesized. Silicon nanoparticles were used as nanoscaffolds for organizing the porphyrins to form light-harvesting complexes thereby enhancing the light absorption of the system. The energy transfer from silicon nanoparticles to porphyrin acceptors was investigated by both steady-state and time-resolved fluorescence spectroscopy. The energy transfer efficiency depended on the donor-acceptor ratio and the distance between the nanoparticle and the porphyrin ring. The addition of C60 resulted in the formation of silicon nanoparticle-porphyrin-fullerene nanoclusters which led to charge separation upon irradiation of the porphyrin ring. The electron-transfer process between the porphyrin and fullerene was investigated by femto-second transient absorption spectroscopy. Finally, the water soluble silicon nanoparticles were used as nanocarriers in photodynamic therapeutic application, in which can selectively deliver porphyrins into human embryonic kidney 293T (HEK293T) cells. In particular, the PEGylated alkynyl-porphyrins were conjugated onto the azido-terminated silicon nanoparticles via a CuAAC "click" reaction. The resultant PEGylated porphyrin grafted silicon nanoparticles have diameters around 13.5 +/- 3.8 nm. The cryo-TEM and conventional TEM analysis proved that the PEGylated porphyrin grafted silicon nanoparticle could form the micelle-like structures at higher concentration in water via self-assembly. The UV-Vis absorption analysis demonstrated that the silicon nanoparticle could reduce the porphyrin aggregation in water which can reduce the photophysical activity of porphyrin. In addition, the nanoparticle complex was capable of producing singlet oxygen when the porphyrin units were excited by light. The cell studies demonstrated that the silicon nanoparticle could deliver the porphyrin drugs into HEK293T cells and accumulate in the mitochondria where the porphyrin could serve as an efficient photosensitizer to kill the cells via mitochondrial apoptotic pathway.

Biomechanical validation of an artificial tooth–periodontal ligament–bone complex for in vitro orthodontic load measurement

PubMed Central

Xia, Zeyang; Chen, Jie

2014-01-01

Objectives To develop an artificial tooth–periodontal ligament (PDL)–bone complex (ATPBC) that simulates clinical crown displacement. Material and Methods An ATPBC was created. It had a socket hosting a tooth with a thin layer of silicon mixture in between for simulating the PDL. The complex was attached to a device that allows applying a controlled force to the crown and measuring the resulting crown displacement. Crown displacements were compared to previously published data for validation. Results The ATPBC that had a PDL made of two types of silicones, 50% gasket sealant No. 2 and 50% RTV 587 silicone, with a thickness of 0.3 mm, simulated the PDL well. The mechanical behaviors (1) force-displacement relationship, (2) stress relaxation, (3) creep, and (4) hysteresis were validated by the published results. Conclusion The ATPBC simulated the crown displacement behavior reported from biological studies well. PMID:22970752

A study of beryllium and beryllium-lithium complexes in single crystal silicon

NASA Technical Reports Server (NTRS)

Crouch, R. K.; Robertson, J. B.; Gilmer, T. E., Jr.

1972-01-01

When beryllium is thermally diffused into silicon, it gives rise to acceptor levels 191 MeV and 145 meV above the valence band. Quenching and annealing studies indicate that the 145-MeV level is due to a more complex beryllium configuration than the 191-MeV level. When lithium is thermally diffused into a beryllium-doped silicon sample, it produces two acceptor levels at 106 MeV and 81 MeV. Quenching and annealing studies indicate that these levels are due to lithium forming a complex with the defects responsible for the 191-MeV and 145-MeV beryllium levels, respectively. Electrical measurements imply that the lithium impurity ions are physically close to the beryllium impurity atoms. The ground state of the 106-MeV beryllium level is split into two levels, presumably by internal strains. Tentative models are proposed.

The Electrochemical Performance of Silicon Nanoparticles in Concentrated Electrolyte.

PubMed

Chang, Zeng-Hua; Wang, Jian-Tao; Wu, Zhao-Hui; Gao, Min; Wu, Shuai-Jin; Lu, Shi-Gang

2018-06-11

Silicon is a promising material for anodes in energy-storage devices. However, excessive growth of a solid-electrolyte interphase (SEI) caused by the severe volume change during the (de)lithiation processes leads to dramatic capacity fading. Here, we report a super-concentrated electrolyte composed of lithium bis(fluorosulfonyl)imide (LiFSI) and propylene carbonate (PC) with a molar ratio of 1:2 to improve the cycling performance of silicon nanoparticles (SiNPs). The SiNP electrode shows a remarkably improved cycling performance with an initial delithiation capacity of approximately 3000 mAh g -1 and a capacity of approximately 2000 mAh g -1 after 100 cycles, exhibiting about 6.8 times higher capacity than the cells with dilute electrolyte LiFSI-(PC) 8 . Raman spectra reveal that most of the PC solvent and FSI anions are complexed by Li + to form a specific solution structure like a fluid polymeric network. The reduction of FSI anions starts to play an important role owing to the increased concentration of contact ion pairs (CIPs) or aggregates (AGGs), which contribute to the formation of a more mechanically robust and chemically stable complex SEI layer. The complex SEI layer can effectively suppress the morphology evolution of silicon particles and self-limit the excessive growth, which mitigates the crack propagation of the silicon electrode and the deterioration of the kinetics. This study will provide a new direction for screening cycling-stable electrolytes for silicon-based electrodes. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Qualitative-Modeling-Based Silicon Neurons and Their Networks

PubMed Central

Kohno, Takashi; Sekikawa, Munehisa; Li, Jing; Nanami, Takuya; Aihara, Kazuyuki

2016-01-01

The ionic conductance models of neuronal cells can finely reproduce a wide variety of complex neuronal activities. However, the complexity of these models has prompted the development of qualitative neuron models. They are described by differential equations with a reduced number of variables and their low-dimensional polynomials, which retain the core mathematical structures. Such simple models form the foundation of a bottom-up approach in computational and theoretical neuroscience. We proposed a qualitative-modeling-based approach for designing silicon neuron circuits, in which the mathematical structures in the polynomial-based qualitative models are reproduced by differential equations with silicon-native expressions. This approach can realize low-power-consuming circuits that can be configured to realize various classes of neuronal cells. In this article, our qualitative-modeling-based silicon neuron circuits for analog and digital implementations are quickly reviewed. One of our CMOS analog silicon neuron circuits can realize a variety of neuronal activities with a power consumption less than 72 nW. The square-wave bursting mode of this circuit is explained. Another circuit can realize Class I and II neuronal activities with about 3 nW. Our digital silicon neuron circuit can also realize these classes. An auto-associative memory realized on an all-to-all connected network of these silicon neurons is also reviewed, in which the neuron class plays important roles in its performance. PMID:27378842

Silicone elastomers capable of large isotropic dimensional change

DOEpatents

Lewicki, James; Worsley, Marcus A.

2017-07-18

Described herein is a highly effective route towards the controlled and isotropic reduction in size-scale, of complex 3D structures using silicone network polymer chemistry. In particular, a class of silicone structures were developed that once patterned and cured can `shrink` micron scale additive manufactured and lithographically patterned structures by as much as 1 order of magnitude while preserving the dimensions and integrity of these parts. This class of silicone materials is compatible with existing additive manufacture and soft lithographic fabrication processes and will allow access to a hitherto unobtainable dimensionality of fabrication.

Silicon micro-mold and method for fabrication

DOEpatents

Morales, Alfredo M.

2005-01-11

The present invention describes a method for rapidly fabricating a robust 3-dimensional silicon micro-mold for use in preparing complex metal micro-components. The process begins by depositing a conductive metal layer onto one surface of a silicon wafer. A thin photoresist and a standard lithographic mask are then used to transfer a trace image pattern onto the opposite surface of the wafer by exposing and developing the resist. The exposed portion of the silicon substrate is anisotropically etched through the wafer thickness down to conductive metal layer to provide an etched pattern consisting of a series of rectilinear channels and recesses in the silicon which serve as the silicon micro-mold. Microcomponents are prepared with this mold by first filling the mold channels and recesses with a metal deposit, typically by electroplating, and then removing the silicon micro-mold by chemical etching.

Silicon micro-mold

DOEpatents

Morales, Alfredo M [Livermore, CA

2006-10-24

The present invention describes a method for rapidly fabricating a robust 3-dimensional silicon-mold for use in preparing complex metal micro-components. The process begins by depositing a conductive metal layer onto one surface of a silicon wafer. A thin photoresist and a standard lithographic mask are then used to transfer a trace image pattern onto the opposite surface of the wafer by exposing and developing the resist. The exposed portion of the silicon substrate is anisotropically etched through the wafer thickness down to conductive metal layer to provide an etched pattern consisting of a series of rectilinear channels and recesses in the silicon which serve as the silicon micro-mold. Microcomponents are prepared with this mold by first filling the mold channels and recesses with a metal deposit, typically by electroplating, and then removing the silicon micro-mold by chemical etching.

Graphitized silicon carbide microbeams: wafer-level, self-aligned graphene on silicon wafers

NASA Astrophysics Data System (ADS)

Cunning, Benjamin V.; Ahmed, Mohsin; Mishra, Neeraj; Ranjbar Kermany, Atieh; Wood, Barry; Iacopi, Francesca

2014-08-01

Currently proven methods that are used to obtain devices with high-quality graphene on silicon wafers involve the transfer of graphene flakes from a growth substrate, resulting in fundamental limitations for large-scale device fabrication. Moreover, the complex three-dimensional structures of interest for microelectromechanical and nanoelectromechanical systems are hardly compatible with such transfer processes. Here, we introduce a methodology for obtaining thousands of microbeams, made of graphitized silicon carbide on silicon, through a site-selective and wafer-scale approach. A Ni-Cu alloy catalyst mediates a self-aligned graphitization on prepatterned SiC microstructures at a temperature that is compatible with silicon technologies. The graphene nanocoating leads to a dramatically enhanced electrical conductivity, which elevates this approach to an ideal method for the replacement of conductive metal films in silicon carbide-based MEMS and NEMS devices.

On-chip integrated optofluidic complex refractive index sensing using silicon photonic crystal nanobeam cavities.

PubMed

Zhang, Xingwang; Zhou, Guangya; Shi, Peng; Du, Han; Lin, Tong; Teng, Jinghua; Chau, Fook Siong

2016-03-15

Complex refractive index sensing is proposed and experimentally demonstrated in optofluidic sensors based on silicon photonic crystal nanobeam cavities. The sensitivities are 58 and 139 nm/RIU, respectively, for the real part (n) and the imaginary part (κ) of the complex refractive index, and the corresponding detection limits are 1.8×10(-5) RIU for n and 4.1×10(-6) RIU for κ. Moreover, the capability of the complex refractive index sensing method to detect the concentration composition of the ternary mixture is demonstrated without the surface immobilization of functional groups, which is impossible to realize with the conventional refractive index sensing scheme.

Surface enhanced fluorescence of anti-tumoral drug emodin adsorbed on silver nanoparticles and loaded on porous silicon

NASA Astrophysics Data System (ADS)

Hernandez, Margarita; Recio, Gonzalo; Martin-Palma, Raul J.; Garcia-Ramos, Jose V.; Domingo, Concepcion; Sevilla, Paz

2012-07-01

Fluorescence spectra of anti-tumoral drug emodin loaded on nanostructured porous silicon have been recorded. The use of colloidal nanoparticles allowed embedding of the drug without previous porous silicon functionalization and leads to the observation of an enhancement of fluorescence of the drug. Mean pore size of porous silicon matrices was 60 nm, while silver nanoparticles mean diameter was 50 nm. Atmospheric and vacuum conditions at room temperature were used to infiltrate emodin-silver nanoparticles complexes into porous silicon matrices. The drug was loaded after adsorption on metal surface, alone, and bound to bovine serum albumin. Methanol and water were used as solvents. Spectra with 1 μm spatial resolution of cross-section of porous silicon layers were recorded to observe the penetration of the drug. A maximum fluorescence enhancement factor of 24 was obtained when protein was loaded bound to albumin, and atmospheric conditions of inclusion were used. A better penetration was obtained using methanol as solvent when comparing with water. Complexes of emodin remain loaded for 30 days after preparation without an apparent degradation of the drug, although a decrease in the enhancement factor is observed. The study reported here constitutes the basis for designing a new drug delivery system with future applications in medicine and pharmacy.

Ab initio EPR parameters for dangling-bond defect complexes in silicon: Effect of Jahn-Teller distortion

NASA Astrophysics Data System (ADS)

Pfanner, Gernot; Freysoldt, Christoph; Neugebauer, Jörg; Gerstmann, Uwe

2012-05-01

A dangling bond (db) is an important point defect in silicon. It is realized in crystalline silicon by defect complexes of the monovacancy V with impurities. In this work, we present spin-polarized density-functional theory calculations of EPR parameters (g and hyperfine tensors) within the GIPAW formalism for two kinds of db defect complexes. The first class characterizes chemically saturated db systems, where three of the four dangling bonds of the isolated vacancy are saturated by hydrogen (VH3) or hydrogen and oxygen (hydrogen-oxygen complex, VOH). The second kind of db consists of systems with a Jahn-Teller distortion, where the vacancy includes either a substitutional phosphorus atom (the E center, VP) or a single hydrogen atom (VH). For all systems we obtain excellent agreement with available experimental data, and we are therefore able to quantify the effect of the Jahn-Teller distortion on the EPR parameters. Furthermore we study the influence of strain to obtain further insights into the structural and electronic characteristics of the considered defects.

Free Energy Minimization Calculation of Complex Chemical Equilibria. Reduction of Silicon Dioxide with Carbon at High Temperature.

ERIC Educational Resources Information Center

Wai, C. M.; Hutchinson, S. G.

1989-01-01

Discusses the calculation of free energy in reactions between silicon dioxide and carbon. Describes several computer programs for calculating the free energy minimization and their uses in chemistry classrooms. Lists 16 references. (YP)

Solid state microdosimetry.

PubMed

Bradley, P D; Rosenfeld, A B; Zaider, M

2001-09-01

A review of solid state microdosimetry is presented with an emphasis on silicon-based devices. The historical foundations and basics of microdosimetry are briefly provided. Various methods of experimental regional microdosimetry are discussed to facilitate a comparison with the more recent development of silicon microdosimetry. In particular, the performance characteristics of a proportional gas counter and a silicon microdosimeter are compared. Recent improvements in silicon microdosimetry address the issues of requirement specification, non-spherical shape, tissue equivalence, sensitive volume definition (charge collection complexity) and low noise requirements which have previously impeded the implementation of silicon-based microdosimetry. A prototype based on silicon-on-insulator technology is described along with some example results from clinical high LET radiotherapy facilities. A brief summary of the applications of microdosimetry is included. c2001 Elsevier Science B.V. All rights reserved.

Silicon microfabricated beam expander

NASA Astrophysics Data System (ADS)

Othman, A.; Ibrahim, M. N.; Hamzah, I. H.; Sulaiman, A. A.; Ain, M. F.

2015-03-01

The feasibility design and development methods of silicon microfabricated beam expander are described. Silicon bulk micromachining fabrication technology is used in producing features of the structure. A high-precision complex 3-D shape of the expander can be formed by exploiting the predictable anisotropic wet etching characteristics of single-crystal silicon in aqueous Potassium-Hydroxide (KOH) solution. The beam-expander consist of two elements, a micromachined silicon reflector chamber and micro-Fresnel zone plate. The micro-Fresnel element is patterned using lithographic methods. The reflector chamber element has a depth of 40 µm, a diameter of 15 mm and gold-coated surfaces. The impact on the depth, diameter of the chamber and absorption for improved performance are discussed.

Article and method for making complex shaped preform and silicon carbide composite by melt infiltration

NASA Technical Reports Server (NTRS)

Corman, Gregory S. (Inventor); Steibel, James D. (Inventor); Schikner, Robert C. (Inventor); Szweda, Andrew (Inventor)

2001-01-01

Small diameter silicon carbide-containing fibers are provided in a bundle such as a fiber tow that can be formed into a structure where the radii of curvature is not limited to 10-20 inches. An aspect of this invention is directed to impregnating the bundles of fibers with the slurry composition to substantially coat the outside surface of an individual fiber within the bundle and to form a complex shaped preform with a mass of continuous fibers.

Article and method for making complex shaped preform and silicon carbide composite by melt infiltration

NASA Technical Reports Server (NTRS)

Szweda, Andrew (Inventor); Corman, Gregory S. (Inventor); Steibel, James D. (Inventor); Schikner, Robert C. (Inventor)

2000-01-01

Small diameter silicon carbide-containing fibers are provided in a bundle such as a fiber tow that can be formed into a structure where the radii of curvature is not limited to 10-20 inches. An aspect of this invention is directed to impregnating the bundles of fibers with the slurry composition to substantially coat the outside surface of an individual fiber within the bundle and to form a complex shaped preform with a mass of continuous fibers.

Morphology and FT IR spectra of porous silicon

NASA Astrophysics Data System (ADS)

Kopani, Martin; Mikula, Milan; Kosnac, Daniel; Gregus, Jan; Pincik, Emil

2017-12-01

The morphology and chemical bods of p-type and n-type porous Si was compared. The surface of n-type sample is smooth, homogenous without any features. The surface of p-type sample reveals micrometer-sized islands. FTIR investigation reveals various distribution of SiOxHy complexes in both p-and n-type samples. From the conditions leading to porous silicon layer formation (the presence of holes) we suggest both SiOxHy and SiFxHy complexes in the layer.

A new nanostructured Silicon biosensor for diagnostics of bovine leucosis

NASA Astrophysics Data System (ADS)

Luchenko, A. I.; Melnichenko, M. M.; Starodub, N. F.; Shmyryeva, O. M.

2010-08-01

In this report we propose a new instrumental method for the biochemical diagnostics of the bovine leucosis through the registration of the formation of the specific immune complex (antigen-antibody) with the help of biosensor based on the nano-structured silicon. The principle of the measurements is based on the determination of the photosensitivity of the surface. In spite of the existed traditional methods of the biochemical diagnostics of the bovine leucosis the proposed approach may provide the express control of the milk quality as direct on the farm and during the process raw materials. The proposed variant of the biosensor based on the nano-structured silicon may be applied for the determination of the concentration of different substances which may form the specific complex in the result of the bioaffine reactions. A new immune technique based on the nanostructured silicon and intended for the quantitative determination of some toxic substances is offered. The sensitivity of such biosensor allows determining T-2 mycotoxin at the concentration of 10 ng/ml during several minutes.

Review of corrosion behavior of ceramic heat exchanger materals: Corrosion characteristics of silicon carbide and silicon nitride. Final report, September 11, 1992--March 11, 1993

DOE Office of Scientific and Technical Information (OSTI.GOV)

Munro, R.G.; Dapkunas, S.J.

1993-09-01

The present work is a review of the substantial effort that has been made to measure and understand the effects of corrosion with respect to the properties, performance, and durability of various forms of silicon carbide and silicon nitride. The review encompasses corrosion in diverse environments, usually at temperatures of 1000C or higher. The environments include dry and moist oxygen, mixtures of hot gaseous vapors, molten salts, molten metals, and complex environments pertaining to coal ashes and slags.

Low Cost Fabrication of Silicon Carbide Based Ceramics and Fiber Reinforced Composites

NASA Technical Reports Server (NTRS)

Singh, M.; Levine, S. R.

1995-01-01

A low cost processing technique called reaction forming for the fabrication of near-net and complex shaped components of silicon carbide based ceramics and composites is presented. This process consists of the production of a microporous carbon preform and subsequent infiltration with liquid silicon or silicon-refractory metal alloys. The microporous preforms are made by the pyrolysis of a polymerized resin mixture with very good control of pore volume and pore size thereby yielding materials with tailorable microstructure and composition. Mechanical properties (elastic modulus, flexural strength, and fracture toughness) of reaction-formed silicon carbide ceramics are presented. This processing approach is suitable for various kinds of reinforcements such as whiskers, particulates, fibers (tows, weaves, and filaments), and 3-D architectures. This approach has also been used to fabricate continuous silicon carbide fiber reinforced ceramic composites (CFCC's) with silicon carbide based matrices. Strong and tough composites with tailorable matrix microstructure and composition have been obtained. Microstructure and thermomechanical properties of a silicon carbide (SCS-6) fiber reinforced reaction-formed silicon carbide matrix composites are discussed.

Spectrophotometric determination of traces of boron in high purity silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parashar, D.C.; Sarkar, A.K.; Singh, N.

1989-07-01

A reddish brown complex is formed between boron and curcumin in concentrated sulfuric acid and glacial acetic acid mixture (1:1). The colored complex is highly selective and stable for about 3 hours and has the maximum absorbance at 545 nm. The sensitivity of the method is extremely high and the detection limit is 3 parts per billion based on 0.004 absorbance value. The interference of some of the important cations and anions relevant to silicon were studied and it is found that 100 fold excess of most of these cations and anions do not interfere in the determination of boron.more » The method is successfully employed for the determination of boron in silicon used in semiconductor devices. The results have been verified by standard addition method.« less

Measurement of the Electron Density and the Attachment Rate Coefficient in Silane/Helium Discharges.

DTIC Science & Technology

1986-09-01

materials -- in this case hydrogenated amorphous silicon . One of the biggest problems in such a task is the fact that the discharge creates complex radicals...electron density is enhanced -- even on a time-averaged basis, and the silicon deposition rate is also increased. The physical process for the density...etching and deposition of semiconductor materials. Plasma etching (also known as dry etching) Of silicon using flourine bearing gases has made it possible

Extinguishing visible photoluminescence of porous silicon stimulated by antigen-antibody immunocomplex formation

NASA Astrophysics Data System (ADS)

Starodub, Nickolaj F.; Fedorenko, Leonid L.; Starodub, Valentyna M.; Dikiy, S. P.; Svechnikov, Sergey V.

1997-02-01

The photoluminescence of the porous silicon obtained by special procedure with the usage of the chemical and laser beam treatment of silicon crystal was investigated in water, buffer and solution containing sodium chloride. It was demonstrated that the intensity of the photoluminescence did not practically change at the above mentioned conditions as well as after antigen or antibody immobilization on the porous silicon surface. But this parameter of the photoluminescence dramatically decreased in case of specific immune complex formation on the silicon surface. The level of the photoluminescence extinguishing depended on duration and intensity of immune reaction. It is proposed to use discovered effect for creation of the immunosensors based on the direct registration of immunocomplex formation.

A density functional study of silicon fullerene endohedral X@Si20F20 and exohedral X-Si20F20 (X=O2-, S2-, Se2-) complexes

NASA Astrophysics Data System (ADS)

Behzadi, Hadi; Esrafili, Mehdi D.; Manzetti, Sergio; Roonasi, Payman

2014-02-01

This study reports the structure and electronic properties of three stable endohedral X@Si20F20 and exohedral X-Si20F20 (X=O2-, S2-, Se2-) complexes. The study revealed that the endohedral complexes with S2- and Se2- result as energy minimum structures, with the guest anion located in the cage center. In the case of endohedral O2--complexes, the pattern is quite different whereas the O2- complexes dramatically deviated from the architecture of S2- and Se2-, by having O2- located toward one of silicon atoms in the cage. With respect to the exohedral form, the energy minimized structure is obtained by positioning the anion between two silicon atoms and forming two Si-X bonds. For both cases, the strength of the interactions is calculated to increase accordingly to the pattern: Se2-@Si20F20 (Se2--Si20F20)

Density functional theory calculation of refractive indices of liquid-forming silicon oil compounds

NASA Astrophysics Data System (ADS)

Lee, Sanghun; Park, Sung Soo; Hagelberg, Frank

2012-02-01

A combination of quantum chemical calculation and molecular dynamics simulation is applied to compute refractive indices of liquid-forming silicon oils. The densities of these species are obtained from molecular dynamics simulations based on the NPT ensemble while the molecular polarizabilities are evaluated by density functional theory. This procedure is shown to yield results well compatible with available experimental data, suggesting that it represents a robust and economic route for determining the refractive indices of liquid-forming organic complexes containing silicon.

Silicon single mode waveguide modulator based upon switchable Bragg reflector

NASA Astrophysics Data System (ADS)

Azogui, Jonathan; Ramon, Yonathan; Businaro, Luca; Ciasca, Gabriele; Gerardino, Annamaria; Zalevsky, Zeev

2018-02-01

In this paper we present the development of an electro optical "Bragg" modulator for telecommunication, in both design and fabrication. The device consists from a regular single mode silicon waveguide (WG) in which an effective Bragg reflector is "turned on" within the WG by means of external bias, due to the plasma dispersion effect, in which the (complexed) refractive index is affected by carrier concentration within the Silicon. Three different strategies are presented for both design and fabrication.

Tunable complex-valued multi-tap microwave photonic filter based on single silicon-on-insulator microring resonator.

PubMed

Lloret, Juan; Sancho, Juan; Pu, Minhao; Gasulla, Ivana; Yvind, Kresten; Sales, Salvador; Capmany, José

2011-06-20

A complex-valued multi-tap tunable microwave photonic filter based on single silicon-on-insulator microring resonator is presented. The degree of tunability of the approach involving two, three and four taps is theoretical and experimentally characterized, respectively. The constraints of exploiting the optical phase transfer function of a microring resonator aiming at implementing complex-valued multi-tap filtering schemes are also reported. The trade-off between the degree of tunability without changing the free spectral range and the number of taps is studied in-depth. Different window based scenarios are evaluated for improving the filter performance in terms of the side-lobe level.

Arrested 1,2-hydrogen migration from silicon to nickel upon oxidation of a three-coordinate Ni(I) silyl complex.

PubMed

Iluc, Vlad M; Hillhouse, Gregory L

2010-09-01

Reaction of the dimeric Ni(I) chloride complex [(dtbpe)NiCl](2) (1) with dimesitylsilyl potassium affords the three-coordinate Ni(I) silyl complex (dtbpe)Ni(SiHMes(2)) (2). Alternatively, 2 can be prepared by an oxidative-addition reaction of Mes(2)Si(H)OTf (Tf = CF(3)SO(3)) with the nickel(0) complex [(dtbpe)Ni](2)(mu-C(6)H(6)) (3), with (dtbpe)Ni(OTf) (4) formed as an easily separable byproduct. The one-electron oxidation of 2 by ferrocenium affords diamagnetic [(dtbpe)Ni(mu-H)SiMes(2)][BAr(F)(4)] (5), a Ni(II) complex formed by partial 1,2-H migration from silicon to nickel and featuring an unusual 3-center, 2-electron bonding motif between Ni, Si, and the bridging H. Complex 5 was also obtained from Mes(2)SiH(2) activation by the neopentyl complex salt [(dtbpe)Ni(CH(2)CMe(3))][BAr(F)(4)] (6) with elimination of neopentane.

Novel axially disubstituted non-aggregated silicon phthalocyanines.

PubMed

Bıyıklıoğlu, Zekeriya; Cakır, Dilek

2012-12-01

This paper describes the synthesis, spectroscopic characterization of a range of new axially-disubstituted silicon phthalocyanines with 2-[2-(dimethylamino)ethoxy] or 2-[2-(1,4,7,10,13-pentaoxa-16-azacyclooctadecan-16-yl)ethoxy] groups as axial ligands. 2-[2-(Dimethylamino)ethoxy]ethanol 2, 2-[2-(1,4,7,10,13-pentaoxa-16-azacyclooctadecan-16-yl)ethoxy]ethanol 4 are reacted with silicon phthalocyanine 1, to give an axially-disubstituted silicon phthalocyanines 3 and 5. Axially-disubstituted silicon phthalocyanine complexes were synthesized at the first time. Newly synthesized silicon phthalocyanines were characterized by UV-Vis, IR, (1)H NMR, (13)C NMR spectroscopy, ESI mass spectrometry. These new silicon(IV) phthalocyanines 3 and 5 showed excellent solubility in organic solvents such as CHCl(3), CH(2)Cl(2), acetone, DMF, DMSO, THF, EtOAc. The aggregation behavior of these compounds were investigated in different concentrations of DMSO. The effect of solvents on absorption spectra were studied in various organic solvents. The thermal stabilities of the silicon(IV) phthalocyanines 3 and 5 were determined by thermogravimetric analysis. Copyright © 2012 Elsevier B.V. All rights reserved.

Role of an Oxidant Mixture as Surface Modifier of Porous Silicon Microstructures Evaluated by Spectroscopic Ellipsometry

PubMed Central

Montiel-González, Zeuz; Escobar, Salvador; Nava, Rocío; del Río, J. Antonio; Tagüeña-Martínez, Julia

2016-01-01

Current research on porous silicon includes the construction of complex structures with luminescent and/or photonic properties. However, their preparation with both characteristics is still challenging. Recently, our group reported a possible method to achieve that by adding an oxidant mixture to the electrolyte used to produce porous silicon. This mixture can chemically modify their microstructure by changing the thickness and surface passivation of the pore walls. In this work, we prepared a series of samples (with and without oxidant mixture) and we evaluated the structural differences through their scanning electron micrographs and their optical properties determined by spectroscopic ellipsometry. The results showed that ellipsometry is sensitive to slight variations in the porous silicon structure, caused by changes in their preparation. The fitting process, based on models constructed from the features observed in the micrographs, allowed us to see that the mayor effect of the oxidant mixture is on samples of high porosity, where the surface oxidation strongly contributes to the skeleton thinning during the electrochemical etching. This suggests the existence of a porosity threshold for the action of the oxidant mixture. These results could have a significant impact on the design of complex porous silicon structures for different optoelectronic applications. PMID:27097767

Role of an Oxidant Mixture as Surface Modifier of Porous Silicon Microstructures Evaluated by Spectroscopic Ellipsometry.

PubMed

Montiel-González, Zeuz; Escobar, Salvador; Nava, Rocío; del Río, J Antonio; Tagüeña-Martínez, Julia

2016-04-21

Current research on porous silicon includes the construction of complex structures with luminescent and/or photonic properties. However, their preparation with both characteristics is still challenging. Recently, our group reported a possible method to achieve that by adding an oxidant mixture to the electrolyte used to produce porous silicon. This mixture can chemically modify their microstructure by changing the thickness and surface passivation of the pore walls. In this work, we prepared a series of samples (with and without oxidant mixture) and we evaluated the structural differences through their scanning electron micrographs and their optical properties determined by spectroscopic ellipsometry. The results showed that ellipsometry is sensitive to slight variations in the porous silicon structure, caused by changes in their preparation. The fitting process, based on models constructed from the features observed in the micrographs, allowed us to see that the mayor effect of the oxidant mixture is on samples of high porosity, where the surface oxidation strongly contributes to the skeleton thinning during the electrochemical etching. This suggests the existence of a porosity threshold for the action of the oxidant mixture. These results could have a significant impact on the design of complex porous silicon structures for different optoelectronic applications.

Formation kinetics and mechanism of metastable vacancy-dioxygen complex in neutron irradiated Czochralski silicon

NASA Astrophysics Data System (ADS)

Dong, Peng; Wang, Rong; Yu, Xuegong; Chen, Lin; Ma, Xiangyang; Yang, Deren

2017-07-01

We have quantitatively investigated the formation kinetics of metastable vacancy-dioxygen (VO2) complex in a structure of [VO + Oi], where a VO complex is trapped in a next-neighbor position to an interstitial oxygen atom (Oi). It is found that the VO annihilation is accompanied by the generation of metastable [VO + Oi] complex during annealing in the temperature range of 220-250 °C. The activation energy for [VO + Oi] generation appears at around 0.48 eV, which is much lower than the counterpart of stable VO2 complex. This indicates that the formation of [VO + Oi] complex originates from the reaction between VO and Oi. The ab initio calculations show that the formation energy of [VO + Oi] complex is larger than that of VO2 complex, which means that [VO + Oi] complex is thermodynamically unfavorable as compared to VO2 complex. However, the binding energy of [VO + Oi] complex is positive, indicating that [VO + Oi] complex is stable against decomposition of VO and Oi in silicon. It is believed that [VO + Oi] complex serves as the intermediate for VO to VO2 conversion.

Final anatomic and visual outcomes appear independent of duration of silicone oil intraocular tamponade in complex retinal detachment surgery.

PubMed

Rhatigan, Maedbh; McElnea, Elizabeth; Murtagh, Patrick; Stephenson, Kirk; Harris, Elaine; Connell, Paul; Keegan, David

2018-01-01

To report anatomic and visual outcomes following silicone oil removal in a cohort of patients with complex retinal detachment, to determine association between duration of tamponade and outcomes and to compare patients with oil removed and those with oil in situ in terms of demographic, surgical and visual factors. We reported a four years retrospective case series of 143 patients with complex retinal detachments who underwent intraocular silicone oil tamponade. Analysis between anatomic and visual outcomes, baseline demographics, duration of tamponade and number of surgical procedures were carried out using Fisher's exact test and unpaired two-tailed t -test. One hundred and six patients (76.2%) had undergone silicone oil removal at the time of review with 96 patients (90.6%) showing retinal reattachment following oil removal. Duration of tamponade was not associated with final reattachment rate or with a deterioration in best corrected visual acuity (BCVA). Patients with oil removed had a significantly better baseline and final BCVA compared to those under oil tamponade ( P =0.0001, <0.0001 respectively). Anatomic and visual outcomes in this cohort are in keeping with those reported in the literature. Favorable outcomes were seen with oil removal but duration of oil tamponade does not affect final attachment rate with modern surgical techniques and should be managed on a case by case basis.

Radiation tolerance of boron doped dendritic web silicon solar cells

NASA Technical Reports Server (NTRS)

Rohatgi, A.

1980-01-01

The potential of dendritic web silicon for giving radiation hard solar cells is compared with the float zone silicon material. Solar cells with n(+)-p-P(+) structure and approximately 15% (AMl) efficiency were subjected to 1 MeV electron irradiation. Radiation tolerance of web cell efficiency was found to be at least as good as that of the float zone silicon cell. A study of the annealing behavior of radiation-induced defects via deep level transient spectroscopy revealed that E sub v + 0.31 eV defect, attributed to boron-oxygen-vacancy complex, is responsible for the reverse annealing of the irradiated cells in the temperature range of 150 to 350 C.

Characterization of Adhesives for Attaching Reusable Surface Insulation on Space Shuttle Vehicles

NASA Technical Reports Server (NTRS)

Owen, H. P.; Carroll, M. T.

1973-01-01

An extensive development and testing program on adhesive systems shows that: (1) A closed cell silicone rubber sponge bonded to substrates with thin bond lines of glass filled adhesive exhibits density and modulus values approximately one third that of solid silicone adhesives; (2) utilization of glass or phenolic microballoons as fillers in silicone adhesives reduces density but increases moduli of the vulcanized materials; (3) the silicone elastomer based adhesives appear to be complex systems rather than homogeneous, isotropic materials. Tensile, shear, and compression properties plotted versus temperature verify this conjecture; and (4) constant strain-stress relaxation tests on glass-filled adhesive show that stress relaxation is most pronounced near the glass transition temperature.

Low-temperature anneal of the divacancy in p-type silicon: A transformation from V2 to VxOy complexes?

NASA Astrophysics Data System (ADS)

Trauwaert, M.-A.; Vanhellemont, J.; Maes, H. E.; Van Bavel, A.-M.; Langouche, G.; Clauws, P.

1995-05-01

Deep level transient spectroscopy of electron irradiated p-type silicon reveals a defect level at Ev+0.19 eV, which during anneal treatments at 200 °C gradually transforms into a band with Ev+0.24 eV. Both energy levels however, are reported in literature to be the donor level of the divacancy. In the present study it is proposed that during the low-temperature anneal the divacancy interacts with oxygen, forming a V2O complex. During heat treatments at temperatures in the range between 250 and 450 °C a further shift of the deep level to higher energy positions is observed which might be related with other vacancy-oxygen complexes.

Complex radial folds versus subtle signs of intracapsular rupture of breast implants: MR findings with surgical correlation.

PubMed

Soo, M S; Kornguth, P J; Walsh, R; Elenberger, C D; Georgiade, G S

1996-06-01

Detection of intracapsular rupture of silicone breast prostheses using MR imaging is often performed by identifying the "linguine sign" [1]. The linguine sign is easily differentiated from simple radial folds that are seen in intact implants. However, more subtle signs of intracapsular rupture, including undulating subcapsular lines and the "teardrop sign," are less often recognized [2-5] and may prove difficult for the less experienced radiologist to differentiate from complex radial folds of intact implants. In this essay, we illustrate the MR imaging findings of complex radial folds in intact implants and compare them with findings of incomplete shell collapse in ruptured implants in a surgically confirmed series of explanted silicone breast prostheses.

Laser-induced phase separation of silicon carbide

PubMed Central

Choi, Insung; Jeong, Hu Young; Shin, Hyeyoung; Kang, Gyeongwon; Byun, Myunghwan; Kim, Hyungjun; Chitu, Adrian M.; Im, James S.; Ruoff, Rodney S.; Choi, Sung-Yool; Lee, Keon Jae

2016-01-01

Understanding the phase separation mechanism of solid-state binary compounds induced by laser–material interaction is a challenge because of the complexity of the compound materials and short processing times. Here we present xenon chloride excimer laser-induced melt-mediated phase separation and surface reconstruction of single-crystal silicon carbide and study this process by high-resolution transmission electron microscopy and a time-resolved reflectance method. A single-pulse laser irradiation triggers melting of the silicon carbide surface, resulting in a phase separation into a disordered carbon layer with partially graphitic domains (∼2.5 nm) and polycrystalline silicon (∼5 nm). Additional pulse irradiations cause sublimation of only the separated silicon element and subsequent transformation of the disordered carbon layer into multilayer graphene. The results demonstrate viability of synthesizing ultra-thin nanomaterials by the decomposition of a binary system. PMID:27901015

Preventing light-induced degradation in multicrystalline silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lindroos, J., E-mail: jeanette.lindroos@aalto.fi; Boulfrad, Y.; Yli-Koski, M.

2014-04-21

Multicrystalline silicon (mc-Si) is currently dominating the silicon solar cell market due to low ingot costs, but its efficiency is limited by transition metals, extended defects, and light-induced degradation (LID). LID is traditionally associated with a boron-oxygen complex, but the origin of the degradation in the top of the commercial mc-Si brick is revealed to be interstitial copper. We demonstrate that both a large negative corona charge and an aluminum oxide thin film with a built-in negative charge decrease the interstitial copper concentration in the bulk, preventing LID in mc-Si.

Preventing light-induced degradation in multicrystalline silicon

NASA Astrophysics Data System (ADS)

Lindroos, J.; Boulfrad, Y.; Yli-Koski, M.; Savin, H.

2014-04-01

Multicrystalline silicon (mc-Si) is currently dominating the silicon solar cell market due to low ingot costs, but its efficiency is limited by transition metals, extended defects, and light-induced degradation (LID). LID is traditionally associated with a boron-oxygen complex, but the origin of the degradation in the top of the commercial mc-Si brick is revealed to be interstitial copper. We demonstrate that both a large negative corona charge and an aluminum oxide thin film with a built-in negative charge decrease the interstitial copper concentration in the bulk, preventing LID in mc-Si.

A Novel Silicone-Magnetite Composite Material Used in the Fabrication of Biomimetic Cilia

NASA Astrophysics Data System (ADS)

Carstens, B. L.; Evans, B. A.; Shields, A. R.; Su, J.; Washburn, S.; Falvo, M. R.; Superfine, R.

2008-10-01

We have developed a novel polymer-magnetite composite that we use to fabricate arrays of magnetically actuable biomimetic cilia. Biomimetic cilia are flexible nanorods 750 nm in diameter and 25 microns tall. They generate fluid flows similar to those produced by biological cilia. Polymer-magnetic nanoparticle materials such as ours are becoming increasingly useful in biomedical applications and microelectromechanical systems (MEMS). Comprised of magnetite (Fe3O4), the nanoparticles have a diameter of 5-7 nm and are complexed with a silicone copolymer and crosslinked into a flexible, magnetic solid. Amine groups make up 6-7 percent of the silicone copolymer, providing a simple means of functionalization. We present a detailed mechanical and magnetic analysis of our bulk crosslinked material. The high-aspect ratio biomimetic cilia we create with this magnetite-copolymer complex may have applications in microfluidic mixing, biofouling, and MEMS.

A stable silicon(0) compound with a Si=Si double bond.

PubMed

Wang, Yuzhong; Xie, Yaoming; Wei, Pingrong; King, R Bruce; Schaefer, Henry F; von R Schleyer, Paul; Robinson, Gregory H

2008-08-22

Dative, or nonoxidative, ligand coordination is common in transition metal complexes; however, this bonding motif is rare in compounds of main group elements in the formal oxidation state of zero. Here, we report that the potassium graphite reduction of the neutral hypervalent silicon-carbene complex L:SiCl4 {where L: is:C[N(2,6-Pri2-C6H3)CH]2 and Pri is isopropyl} produces L:(Cl)Si-Si(Cl):L, a carbene-stabilized bis-silylene, and L:Si=Si:L, a carbene-stabilized diatomic silicon molecule with the Si atoms in the formal oxidation state of zero. The Si-Si bond distance of 2.2294 +/- 0.0011 (standard deviation) angstroms in L:Si=Si:L is consistent with a Si=Si double bond. Complementary computational studies confirm the nature of the bonding in L:(Cl)Si-Si(Cl):L and L:Si=Si:L.

Influence of oxygen-vacancy complex /A center/ on piezoresistance of n-type silicon.

NASA Technical Reports Server (NTRS)

Littlejohn, M. A.; Loggins, C. D., Jr.

1972-01-01

Changes in both magnitude and temperature dependence of the piezoresistance of electron-irradiated n-type silicon, induced by the latter's oxygen-vacancy complex (A center), are shown to be due to the fact that the presence of the A center causes the total conduction-band electron concentration to change with an applied stress. This change in electron concentration leads to an additional piezoresistance contribution that is expected to be important in certain many-valley semiconductors. This offers the possibility of tailoring the thermal variations of semiconductor mechanical sensors to more desirable values over limited temperature ranges.

Phosphine and diphosphine complexes of silicon(IV) halides.

PubMed

Levason, William; Pugh, David; Reid, Gillian

2013-05-06

The reaction of SiX4 (X = Cl or Br) with PMe3 in anhydrous CH2Cl2 forms trans-[SiX4(PMe3)2], while the diphosphines, Me2P(CH2)2PMe2, Et2P(CH2)2PEt2, and o-C6H4(PMe2)2 form cis-[SiX4(diphosphine)], all containing six-coordinate silicon centers. With Me2PCH2PMe2 the product was trans-[SiCl4(κ(1)-Me2PCH2PMe2)2]. The complexes have been characterized by X-ray crystallography, microanalysis, IR, and multinuclear ((1)H, (13)C{(1)H}, and (31)P{(1)H}) NMR spectroscopies. The complexes are stable solids and not significantly dissociated in nondonor solvents, although they are very moisture and oxygen sensitive. This stability conflicts with the predictions of recent density functional theory (DFT) calculations (Wilson et al. Inorg. Chem. 2012, 51, 7657-7668) which suggested six-coordinate silicon phosphines would be unstable, and also contrasts with the failure to isolate complexes with SiF4 (George et al. Dalton Trans. 2011, 40, 1584-1593). No reaction occurred between phosphines and SiI4, or with SiX4 and arsine ligands including AsMe3 and o-C6H4(AsMe2)2. Attempts to make five-coordinate [SiX4(PR3)] using the sterically bulky phosphines, P(t)Bu3, P(i)Pr3, or PCy3 failed, with no apparent reaction occurring, consistent with predictions (Wilson et al. Inorg. Chem. 2012, 51, 7657-7668) that such compounds would be very endothermic, while the large cone angles of the phosphines presumably preclude formation of six-coordination at the small silicon center. The reaction of Si2Cl6 with PMe3 or the diphosphines in CH2Cl2 results in instant disproportionation to the SiCl4 adducts and polychlorosilanes, but from hexane solution very unstable white [Si2Cl6(PMe3)2] and [Si2Cl6(diphosphine)] (diphosphine = Me2P(CH2)2PMe2 or o-C6H4(PMe2)2) precipitate. The reactions of SiHCl3 with PMe3 and Me2P(CH2)2PMe2 also produce the SiCl4 adducts, but using Et2P(CH2)2PEt2, colorless [SiHCl3{Et2P(CH2)2PEt2}] was isolated, which was characterized by an X-ray structure which showed a pseudo-octahedral complex with the Si-H trans to P. Attempts to reduce the silicon(IV) phosphine complexes to silicon(II) were unsuccessful, contrasting with the isolation of stable N-heterocyclic carbene adducts of Si(II).

Inkjet 3D printing of UV and thermal cure silicone elastomers for dielectric elastomer actuators

NASA Astrophysics Data System (ADS)

McCoul, David; Rosset, Samuel; Schlatter, Samuel; Shea, Herbert

2017-12-01

Dielectric elastomer actuators (DEAs) are an attractive form of electromechanical transducer, possessing high energy densities, an efficient design, mechanical compliance, high speed, and noiseless operation. They have been incorporated into a wide variety of devices, such as microfluidic systems, cell bioreactors, tunable optics, haptic displays, and actuators for soft robotics. Fabrication of DEA devices is complex, and the majority are inefficiently made by hand. 3D printing offers an automated and flexible manufacturing alternative that can fabricate complex, multi-material, integrated devices consistently and in high resolution. We present a novel additive manufacturing approach to DEA devices in which five commercially available, thermal and UV-cure DEA silicone rubber materials have been 3D printed with a drop-on-demand, piezoelectric inkjet system. Using this process, 3D structures and high-quality silicone dielectric elastomer membranes as thin as 2 μm have been printed that exhibit mechanical and actuation performance at least as good as conventionally blade-cast membranes. Printed silicone membranes exhibited maximum tensile strains of up to 727%, and DEAs with printed silicone dielectrics were actuated up to 6.1% area strain at a breakdown strength of 84 V μm-1 and also up to 130 V μm-1 at 2.4% strain. This approach holds great potential to manufacture reliable, high-performance DEA devices with high throughput.

About complex refractive index of black Si

NASA Astrophysics Data System (ADS)

Pinčík, Emil; Brunner, Robert; Kobayashi, Hikaru; Mikula, Milan

2017-12-01

The paper deals with the complex refractive index in the IR light region of two types of samples (i) as prepared black silicon, and (ii) thermally oxidized black silicon (BSi) nano-crystalline specimens produced both by the surface structure chemical transfer method using catalytic Ag evaporated spots (as prepared sample) and by the catalytic Pt catalytic mesh (thermally oxidized sample). We present, compare, and discuss the values of the IR complex refractive index obtained by calculation using the Kramers-Krönig transformation. Results indicate that small differences between optical properties of as prepared black Si and thermally oxidized BSi are given by: (i) - oxidation procedure, (ii) - thickness of the formed black Si layer, mainly, not by utilization of different catalytic metals, and by iii) the different thickness. Contamination of the surface by different catalytic metals contributes almost equally to the calculated values of the corresponding complex refractive index.

An innovative large scale integration of silicon nanowire-based field effect transistors

NASA Astrophysics Data System (ADS)

Legallais, M.; Nguyen, T. T. T.; Mouis, M.; Salem, B.; Robin, E.; Chenevier, P.; Ternon, C.

2018-05-01

Since the early 2000s, silicon nanowire field effect transistors are emerging as ultrasensitive biosensors while offering label-free, portable and rapid detection. Nevertheless, their large scale production remains an ongoing challenge due to time consuming, complex and costly technology. In order to bypass these issues, we report here on the first integration of silicon nanowire networks, called nanonet, into long channel field effect transistors using standard microelectronic process. A special attention is paid to the silicidation of the contacts which involved a large number of SiNWs. The electrical characteristics of these FETs constituted by randomly oriented silicon nanowires are also studied. Compatible integration on the back-end of CMOS readout and promising electrical performances open new opportunities for sensing applications.

Growth of the 889 per cm infrared band in annealed electron-irradiated silicon

NASA Technical Reports Server (NTRS)

Svensson, B. G.; Lindstrom, J. L.; Corbett, J. W.

1985-01-01

Isothermal annealing of electron-irradiated Czochralski silicon has been studied at four different temperatures ranging from 304 to 350 C using infrared spectroscopy. At annealing temperatures above 300 C the irradiation-induced band at 830 per cm, usually attributed to a vacancy-oxygen complex (the A center), disappears and a new band at 889 per cm grows up. Within the experimental accuracy, the activation energy for the growth of this band is found to be identical with the value given by Stavola et al. for 'anomalous' oxygen diffusion in silicon. Also the frequency factors for the two processes are in reasonable agreement. The results show that a vacancy-assisted process may provide an explanation for enhanced motion of oxygen in silicon.

Origin of dislocation luminescence centers and their reorganization in p-type silicon crystal subjected to plastic deformation and high temperature annealing.

PubMed

Pavlyk, Bohdan; Kushlyk, Markiyan; Slobodzyan, Dmytro

2017-12-01

Changes of the defect structure of silicon p-type crystal surface layer under the influence of plastic deformation and high temperature annealing in oxygen atmosphere were investigated by deep-level capacitance-modulation spectroscopy (DLCMS) and IR spectroscopy of molecules and atom vibrational levels. Special role of dislocations in the surface layer of silicon during the formation of its energy spectrum and rebuilding the defective structure was established. It is shown that the concentration of linear defects (N ≥ 10 4  cm -2 ) enriches surface layer with electrically active complexes (dislocation-oxygen, dislocation-vacancy, and dislocation-interstitial atoms of silicon) which are an effective radiative recombination centers.

Fatigue degradation and electric recovery in Silicon solar cells embedded in photovoltaic modules

PubMed Central

Paggi, Marco; Berardone, Irene; Infuso, Andrea; Corrado, Mauro

2014-01-01

Cracking in Silicon solar cells is an important factor for the electrical power-loss of photovoltaic modules. Simple geometrical criteria identifying the amount of inactive cell areas depending on the position of cracks with respect to the main electric conductors have been proposed in the literature to predict worst case scenarios. Here we present an experimental study based on the electroluminescence (EL) technique showing that crack propagation in monocrystalline Silicon cells embedded in photovoltaic (PV) modules is a much more complex phenomenon. In spite of the very brittle nature of Silicon, due to the action of the encapsulating polymer and residual thermo-elastic stresses, cracked regions can recover the electric conductivity during mechanical unloading due to crack closure. During cyclic bending, fatigue degradation is reported. This pinpoints the importance of reducing cyclic stresses caused by vibrations due to transportation and use, in order to limit the effect of cracking in Silicon cells. PMID:24675974

Effect of dose and size on defect engineering in carbon cluster implanted silicon wafers

NASA Astrophysics Data System (ADS)

Okuyama, Ryosuke; Masada, Ayumi; Shigematsu, Satoshi; Kadono, Takeshi; Hirose, Ryo; Koga, Yoshihiro; Okuda, Hidehiko; Kurita, Kazunari

2018-01-01

Carbon-cluster-ion-implanted defects were investigated by high-resolution cross-sectional transmission electron microscopy toward achieving high-performance CMOS image sensors. We revealed that implantation damage formation in the silicon wafer bulk significantly differs between carbon-cluster and monomer ions after implantation. After epitaxial growth, small and large defects were observed in the implanted region of carbon clusters. The electron diffraction pattern of both small and large defects exhibits that from bulk crystalline silicon in the implanted region. On the one hand, we assumed that the silicon carbide structure was not formed in the implanted region, and small defects formed because of the complex of carbon and interstitial silicon. On the other hand, large defects were hypothesized to originate from the recrystallization of the amorphous layer formed by high-dose carbon-cluster implantation. These defects are considered to contribute to the powerful gettering capability required for high-performance CMOS image sensors.

Alloy-assisted deposition of three-dimensional arrays of atomic gold catalyst for crystal growth studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fang, Yin; Jiang, Yuanwen; Cherukara, Mathew J.

Large-scale assembly of individual atoms over smooth surfaces is difficult to achieve. A configuration of an atom reservoir, in which individual atoms can be readily extracted, may successfully address this challenge. In this work, we demonstrate that a liquid gold-silicon alloy established in classical vapor-liquid-solid growth can deposit ordered and three-dimensional rings of isolated gold atoms over silicon nanowire sidewalls. Here, we perform ab initio molecular dynamics simulation and unveil a surprising single atomic gold-catalyzed chemical etching of silicon. Experimental verification of this catalytic process in silicon nanowires yields dopant-dependent, massive and ordered 3D grooves with spacing down to similarmore » to 5 nm. Finally, we use these grooves as self-labeled and ex situ markers to resolve several complex silicon growths, including the formation of nodes, kinks, scale-like interfaces, and curved backbones.« less

Colloidal characterization of silicon nitride and silicon carbide

NASA Technical Reports Server (NTRS)

Feke, Donald L.

1986-01-01

The colloidal behavior of aqueous ceramic slips strongly affects the forming and sintering behavior and the ultimate mechanical strength of the final ceramic product. The colloidal behavior of these materials, which is dominated by electrical interactions between the particles, is complex due to the strong interaction of the solids with the processing fluids. A surface titration methodology, modified to account for this interaction, was developed and used to provide fundamental insights into the interfacial chemistry of these systems. Various powder pretreatment strategies were explored to differentiate between true surface chemistry and artifacts due to exposure history. The colloidal behavior of both silicon nitride and carbide is dominated by silanol groups on the powder surfaces. However, the colloid chemistry of silicon nitride is apparently influenced by an additional amine group. With the proper powder treatments, silicon nitride and carbide powder can be made to appear colloidally equivalent. The impact of these results on processing control will be discussed.

Alloy-assisted deposition of three-dimensional arrays of atomic gold catalyst for crystal growth studies

DOE PAGES

Fang, Yin; Jiang, Yuanwen; Cherukara, Mathew J.; ...

2017-12-08

Large-scale assembly of individual atoms over smooth surfaces is difficult to achieve. A configuration of an atom reservoir, in which individual atoms can be readily extracted, may successfully address this challenge. In this work, we demonstrate that a liquid gold-silicon alloy established in classical vapor-liquid-solid growth can deposit ordered and three-dimensional rings of isolated gold atoms over silicon nanowire sidewalls. Here, we perform ab initio molecular dynamics simulation and unveil a surprising single atomic gold-catalyzed chemical etching of silicon. Experimental verification of this catalytic process in silicon nanowires yields dopant-dependent, massive and ordered 3D grooves with spacing down to similarmore » to 5 nm. Finally, we use these grooves as self-labeled and ex situ markers to resolve several complex silicon growths, including the formation of nodes, kinks, scale-like interfaces, and curved backbones.« less

Observation of enhanced infrared absorption in silicon supersaturated with gold by pulsed laser melting of nanometer-thick gold films

NASA Astrophysics Data System (ADS)

Chow, Philippe K.; Yang, Wenjie; Hudspeth, Quentin; Lim, Shao Qi; Williams, Jim S.; Warrender, Jeffrey M.

2018-04-01

We demonstrate that pulsed laser melting (PLM) of thin 1, 5, and 10 nm-thick vapor-deposited gold layers on silicon enhances its room-temperature sub-band gap infrared absorption, as in the case of ion-implanted and PLM-treated silicon. The former approach offers reduced fabrication complexity and avoids implantation-induced lattice damage compared to ion implantation and pulsed laser melting, while exhibiting comparable optical absorptance. We additionally observed strong broadband absorptance enhancement in PLM samples made using 5- and 10-nm-thick gold layers. Raman spectroscopy and Rutherford backscattering analysis indicate that such an enhancement could be explained by absorption by a metastable, disordered and gold-rich surface layer. The sheet resistance and the diode electrical characteristics further elucidate the role of gold-supersaturation in silicon, revealing the promise for future silicon-based infrared device applications.

p-type doping by platinum diffusion in low phosphorus doped silicon

NASA Astrophysics Data System (ADS)

Ventura, L.; Pichaud, B.; Vervisch, W.; Lanois, F.

2003-07-01

In this work we show that the cooling rate following a platinum diffusion strongly influences the electrical conductivity in weakly phosphorus doped silicon. Diffusions were performed at the temperature of 910 °C in the range of 8 32 hours in 0.6, 30, and 60 Ωrm cm phosphorus doped silicon samples. Spreading resistance profile analyses clearly show an n-type to p-type conversion under the surface when samples are cooled slowly. On the other hand, a compensation of the phosphorus donors can only be observed when samples are quenched. One Pt related acceptor deep level at 0.43 eV from the valence band is assumed to be at the origin of the type conversion mechanism. Its concentration increases by lowering the applied cooling rate. A complex formation with fast species such as interstitial Pt atoms or intrinsic point defects is expected. In 0.6 Ωrm cm phosphorus doped silicon, no acceptor deep level in the lower band gap is detected by DLTS measurement. This removes the opportunity of a pairing between phosphorus and platinum and suggests the possibility of a Fermi level controlled complex formation.

Weak interactions and cooperativity effects on disiloxane: a look at the building block of silicones

NASA Astrophysics Data System (ADS)

Martín-Fernández, Carlos; Montero-Campillo, M. Merced; Alkorta, Ibon; Elguero, José

2018-06-01

The behaviour of disiloxane 1 towards a set of Lewis acids (LA) and Lewis bases (LB) forming complexes through its oxygen and silicon atoms, respectively, was studied at the MP2/aug‧-cc-pVTZ level of theory, exploring a wide variety of non-covalent interactions. Disiloxane is a moderate electron acceptor and a good electron donor, exhibiting in the latter case binding energies up to almost -100 kJ/mol with BeCl2. Cooperativity effects were also analysed by looking at ternary 1:LA:LB complexes. Shorter intermolecular distances than in the corresponding binary complexes and a negative contribution of the three-body term to the binding energy indicate that the non-covalent interactions allowed by disiloxane through its acid and basic centres cooperate between them to reinforce both donor-acceptor pairs. These effects are particularly strong in complexes involving beryllium and triel bonds, but are also relevant for complexes containing hydrogen bonds.

Mechanically flexible optically transparent silicon fabric with high thermal budget devices from bulk silicon (100)

NASA Astrophysics Data System (ADS)

Hussain, Muhammad M.; Rojas, Jhonathan P.; Torres Sevilla, Galo A.

2013-05-01

Today's information age is driven by silicon based electronics. For nearly four decades semiconductor industry has perfected the fabrication process of continuingly scaled transistor - heart of modern day electronics. In future, silicon industry will be more pervasive, whose application will range from ultra-mobile computation to bio-integrated medical electronics. Emergence of flexible electronics opens up interesting opportunities to expand the horizon of electronics industry. However, silicon - industry's darling material is rigid and brittle. Therefore, we report a generic batch fabrication process to convert nearly any silicon electronics into a flexible one without compromising its (i) performance; (ii) ultra-large-scale-integration complexity to integrate billions of transistors within small areas; (iii) state-of-the-art process compatibility, (iv) advanced materials used in modern semiconductor technology; (v) the most widely used and well-studied low-cost substrate mono-crystalline bulk silicon (100). In our process, we make trenches using anisotropic reactive ion etching (RIE) in the inactive areas (in between the devices) of a silicon substrate (after the devices have been fabricated following the regular CMOS process), followed by a dielectric based spacer formation to protect the sidewall of the trench and then performing an isotropic etch to create caves in silicon. When these caves meet with each other the top portion of the silicon with the devices is ready to be peeled off from the bottom silicon substrate. Release process does not need to use any external support. Released silicon fabric (25 μm thick) is mechanically flexible (5 mm bending radius) and the trenches make it semi-transparent (transparency of 7%).

Fabrication of sinterable silicon nitride by injection molding

NASA Technical Reports Server (NTRS)

Quackenbush, C. L.; French, K.; Neil, J. T.

1982-01-01

Transformation of structural ceramics from the laboratory to production requires development of near net shape fabrication techniques which minimize finish grinding. One potential technique for producing large quantities of complex-shaped parts at a low cost, and microstructure of sintered silicon nitride fabricated by injection molding is discussed and compared to data generated from isostatically dry-pressed material. Binder selection methodology, compounding of ceramic and binder components, injection molding techniques, and problems in binder removal are discussed. Strength, oxidation resistance, and microstructure of sintered silicon nitride fabricated by injection molding is discussed and compared to data generated from isostatically dry-pressed material.

Modular fabrication and characterization of complex silicon carbide composite structures Advanced Reactor Technologies (ART) Research Final Report (Feb 2015 – May 2017)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khalifa, Hesham

Advanced ceramic materials exhibit properties that enable safety and fuel cycle efficiency improvements in advanced nuclear reactors. In order to fully exploit these desirable properties, new processing techniques are required to produce the complex geometries inherent to nuclear fuel assemblies and support structures. Through this project, the state of complex SiC-SiC composite fabrication for nuclear components has advanced significantly. New methods to produce complex SiC-SiC composite structures have been demonstrated in the form factors needed for in-core structural components in advanced high temperature nuclear reactors. Advanced characterization techniques have been employed to demonstrate that these complex SiC-SiC composite structures providemore » the strength, toughness and hermeticity required for service in harsh reactor conditions. The complex structures produced in this project represent a significant step forward in leveraging the excellent high temperature strength, resistance to neutron induced damage, and low neutron cross section of silicon carbide in nuclear applications.« less

Amphotericin B channels in phospholipid membrane-coated nanoporous silicon surfaces: implications for photovoltaic driving of ions across membranes.

PubMed

Yilma, Solomon; Liu, Nangou; Samoylov, Alexander; Lo, Ting; Brinker, C Jeffrey; Vodyanoy, Vitaly

2007-03-15

The antimycotic agent amphotericin B (AmB) functions by forming complexes with sterols to form ion channels that cause membrane leakage. When AmB and cholesterol mixed at 2:1 ratio were incorporated into phospholipid bilayer membranes formed on the tip of patch pipettes, ion channel current fluctuations with characteristic open and closed states were observed. These channels were also functional in phospholipid membranes formed on nanoporous silicon surfaces. Electrophysiological studies of AmB-cholesterol mixtures that were incorporated into phospholipid membranes formed on the surface of nanoporous (6.5 nm pore diameter) silicon plates revealed large conductance ion channels ( approximately 300 pS) with distinct open and closed states. Currents through the AmB-cholesterol channels on nanoporous silicon surfaces can be driven by voltage applied via conventional electrical circuits or by photovoltaic electrical potential entirely generated when the nanoporous silicon surface is illuminated with a narrow laser beam. Electrical recordings made during laser illumination of AmB-cholesterol containing membrane-coated nanoporous silicon surfaces revealed very large conductance ion channels with distinct open and closed states. Our findings indicate that nanoporous silicon surfaces can serve as mediums for ion-channel-based biosensors. The photovoltaic properties of nanoporous silicon surfaces show great promise for making such biosensors addressable via optical technologies.

A Cover of Glass: First Report of Biomineralized Silicon in a Ciliate, Maryna umbrellata (Ciliophora: Colpodea)

PubMed Central

FOISSNER, WILHELM; WEISSENBACHER, BIRGIT; KRAUTGARTNER, WOLF-DIETRICH; LÜTZ-MEINDL, URSULA

2010-01-01

Using hydrofluoric acid, scanning electron microscope-assisted X-ray microanalysis, and energy-filtered transmission electron microscopy, we present the first definite proof of biomineralized silicon [(SiO2)]n in a ciliophoran protist, Maryna umbrellata, a common inhabitant of ephemeral pools. In the trophic specimen, the amorphic silicon (glass) granules are accumulated in the anterior half of the body. When entering the dormant stage, most glass granules are excreted to form the surface cover of the globular resting cyst. Most likely, the silicon granules are synthesized in vesicles of the Golgi apparatus. First, nanospheres with a size of 20–40 nm are formed in a fibrous matrix; they grow to be spongious complexes, eventually becoming amorphous glass granules with an average size of 819 nm × 630 nm. In the transmission electron microscope, the silicon granules show the characteristic fracture pattern of glass known from many other silicon-bearing organisms. A literature survey suggests that silicon is very rare in ciliates. The fine structure and genesis of silicon granules in M. umbrellata are very similar to those of other organisms, including vascular plants and animals, indicating a common mechanism. Light perception and protection against mechanical stress and predators might be functions of the silicon granules in M. umbrellata. The palaeontological significance of glass cysts in ciliates is also discussed. PMID:19883440

A general classification of silicon utilizing organisms

NASA Astrophysics Data System (ADS)

Das, P.; Das, S.

2010-12-01

Silicon utilizing organisms may be defined as organisms with high silicon content (≥ 1% dry weight) and they can metabolize silicon with or without demonstrable silicon transporter genes (SIT) in them(Das,2010). Silicon is the second most abundant element in the lithosphere (27.70%) and it is as important as phosphorus and magnesium (0.03%) in the biota. Hydrated silica represents the second most abundant biogenic mineral after carbonate minerals. Silicon is accumulated and metabolized by some prokaryotes, and Si compounds can stimulate the growth of a range of fungi. It is well known that Si is essential for diatoms. In mammals, Si is considered an essential trace element, required in bone, cartilage and connective tissue formation, enzymatic activities and other metabolic processes. Silicon was suggested to act as a phosphoprotein effector in bone. In mammals, Si is also reported to positively influence the immune system and to be required for lymphocyte proliferation. The aqueous chemistry of Si is dominated by silicic acid at biological pH ranges. Monosilicic acid can form stable complexes with organic hydroxy-containing molecules . Biosilica also has been identified associated with various biomolecules including proteins and carbohydrates. There are main seven groups of silicon utilizing organisms belonging to Gram positive bacteria, algae, protozoa, sponges, fungi, lichens, and monocotyledon plants. In each group again all the members are not silicon utilizing organisms, thus selective members in each group are further classified depending their degree of silicon utilization. Important silicon utilizing bacteria are Mycobacteria, Nocardia, Streptomyces, Staphylococcus, Bacillus, Lactobacillus spp. etc., Important silicon utilizing algae are Centrobacillariophyceae, Pennatibacillariophyceae and Chrysophyceae. Many protozoa belonging to Heterokonta, Choanoflagellida, Actinopoda are well known silicon utilizing microorganisms. Hexactinellida ( glass sponges), Demospongiae and Sclerospongiae are important silicon utilizing sponges. Fungi like Aspergillus, Penicillium, Rhizopus etc. are also silicon utilizing. Candida spp. also belong to silicon utilizing organisms as they are also frequently found in sputum in silicotuberculosis cases. Many monocotyledon plants belonging to Pteridophyta, Magnoliophyta etc. are also well known silicon utilizing organisms. Almost all lichens belong to the group of silicon utilizing organisms.

An FPGA-Based Silicon Neuronal Network with Selectable Excitability Silicon Neurons

PubMed Central

Li, Jing; Katori, Yuichi; Kohno, Takashi

2012-01-01

This paper presents a digital silicon neuronal network which simulates the nerve system in creatures and has the ability to execute intelligent tasks, such as associative memory. Two essential elements, the mathematical-structure-based digital spiking silicon neuron (DSSN) and the transmitter release based silicon synapse, allow us to tune the excitability of silicon neurons and are computationally efficient for hardware implementation. We adopt mixed pipeline and parallel structure and shift operations to design a sufficient large and complex network without excessive hardware resource cost. The network with 256 full-connected neurons is built on a Digilent Atlys board equipped with a Xilinx Spartan-6 LX45 FPGA. Besides, a memory control block and USB control block are designed to accomplish the task of data communication between the network and the host PC. This paper also describes the mechanism of associative memory performed in the silicon neuronal network. The network is capable of retrieving stored patterns if the inputs contain enough information of them. The retrieving probability increases with the similarity between the input and the stored pattern increasing. Synchronization of neurons is observed when the successful stored pattern retrieval occurs. PMID:23269911

Magnetomechanical effect in silicon (Cz-Si) surface layers

NASA Astrophysics Data System (ADS)

Koplak, O. V.; Dmitriev, A. I.; Morgunov, R. B.

2012-07-01

The mechanical properties of near-surface layers of Czochralski-grown silicon crystals Cz- n-Si(111) have been found to undergo changes in response to an external constant magnetic field ( B ˜ 0.1 T). A magnetically induced variation in the microhardness, Young's modulus, and coefficient of plasticity of silicon crystals correlates with the change in the lattice parameter and internal stresses of the sample. The growth of an oxide film under exposure to a magnetic field plays the principal role in the magnetomechanical effect due to a decrease in the concentration of oxygen complexes in the near-surface layers of the sample. In microstructured silicon, where the surface is considerably more developed, the magnetic field induces more profound changes in the internal stresses as compared to single crystals.

Hybrid integration of carbon nanotubes in silicon photonic structures

NASA Astrophysics Data System (ADS)

Durán-Valdeiglesias, E.; Zhang, W.; Alonso-Ramos, C.; Le Roux, X.; Serna, S.; Hoang, H. C.; Marris-Morini, D.; Cassan, E.; Intonti, F.; Sarti, F.; Caselli, N.; La China, F.; Gurioli, M.; Balestrieri, M.; Vivien, L.; Filoramo, A.

2017-02-01

Silicon photonics, due to its compatibility with the CMOS platform and unprecedented integration capability, has become the preferred solution for the implementation of next generation optical interconnects to accomplish high efficiency, low energy consumption, low cost and device miniaturization in one single chip. However, it is restricted by silicon itself. Silicon does not have efficient light emission or detection in the telecommunication wavelength range (1.3 μm-1.5 μm) or any electro-optic effect (i.e. Pockels effect). Hence, silicon photonic needs to be complemented with other materials for the realization of optically-active devices, including III-V for lasing and Ge for detection. The very different requirement of these materials results in complex fabrication processes that offset the cost-effectiveness of the Si photonics approach. For this purpose, carbon nanotubes (CNTs) have recently been proposed as an attractive one-dimensional light emitting material. Interestingly, semiconducting single walled CNTs (SWNTs) exhibit room-temperature photo- and electro-luminescence in the near-IR that could be exploited for the implementation of integrated nano-sources. They can also be considered for the realization of photo-detectors and optical modulators, since they rely on intrinsically fast non-linear effects, such as Stark and Kerr effect. All these properties make SWNTs ideal candidates in order to fabricate a large variety of optoelectronic devices, including near-IR sources, modulators and photodetectors on Si photonic platforms. In addition, solution processed SWNTs can be integrated on Si using spin-coating or drop-casting techniques, obviating the need of complex epitaxial growth or chip bonding approaches. Here, we report on our recent progress in the coupling of SWNTs light emission into optical resonators implemented on the silicon-on-insulator (SOI) platform. .

Release of Si from Silicon, a Ferrosilicon (FeSi) Alloy and a Synthetic Silicate Mineral in Simulated Biological Media

PubMed Central

Herting, Gunilla; Jiang, Tao; Sjöstedt, Carin; Odnevall Wallinder, Inger

2014-01-01

Unique quantitative bioaccessibility data has been generated, and the influence of surface/material and test media characteristics on the elemental release process were assessed for silicon containing materials in specific synthetic body fluids at certain time periods at a fixed loading. The metal release test protocol, elaborated by the KTH team, has previously been used for classification, ranking, and screening of different alloys and metals. Time resolved elemental release of Si, Fe and Al from particles, sized less than 50 µm, of two grades of metallurgical silicon (high purity silicon, SiHG, low purity silicon, SiLG), an alloy (ferrosilicon, FeSi) and a mineral (aluminium silicate, AlSi) has been investigated in synthetic body fluids of varying pH, composition and complexation capacity, simple models of for example dermal contact and digestion scenarios. Individual methods for analysis of released Si (as silicic acid, Si(OH)4) in synthetic body fluids using GF-AAS were developed for each fluid including optimisation of solution pH and graphite furnace parameters. The release of Si from the two metallurgical silicon grades was strongly dependent on both pH and media composition with the highest release in pH neutral media. No similar effect was observed for the FeSi alloy or the aluminium silicate mineral. Surface adsorption of phosphate and lactic acid were believed to hinder the release of Si whereas the presence of citric acid enhanced the release as a result of surface complexation. An increased presence of Al and Fe in the material (low purity metalloid, alloy or mineral) resulted in a reduced release of Si in pH neutral media. The release of Si was enhanced for all materials with Al at their outermost surface in acetic media. PMID:25225879

Comparison of 1000-Centistoke versus 5000-Centistoke Silicone Oil in Complex Retinal Detachment Surgery.

PubMed

Zafar, Shakir; Shakir, Munira; Mahmood, Syed Asaad; Amin, Saima; Iqbal, Zafar

2016-01-01

To compare the efficacy and complications of using 1000-centistoke versus 5000-centistoke silicone oil for complex retinal detachment repair. Case series. LRBT Tertiary Eye Hospital, Karachi, from January 2007 to June 2013. Eighty-five eyes (85 patients) presenting with superior rhegmatogenous retinal detachments associated with PVR grades B and C (involving not more than 3 clock hours) were randomized to either 1000 centistokes (n=44) or 5000 centistokes (n=41) silicone oil group. All patients underwent 23-gauge pars plana vitrectomy surgery with silicone oil intraocular tamponade. Patient data was analysed at 18 months post-operatively. IBM SPSS 21 was used for data analysis. There were 52 male and 33 female patients aged between 22 and 70 years (45.2 ±16.2). After the first surgery, successful reattachment of the retina was achieved in 67 eyes (78.8%); of which 35 eyes were in 1000-centistoke and 32 eyes in 5000-centistoke groups. Mean pre-operative Best Corrected Visual Acuity (BCVA) was 1.63 ±0.54 which was improved to a mean post-operative BCVAof 1.46 ±0.78 (1.42 ±0.74 in 1000-centistoke group; 1.49 ±0.78 in 5000 centistoke group). The 1000-centistoke group had a significantly higher frequency of oil emulsification which necessitated early removal of silicone oil. There were 66 eyes (77%) with at least one complication (34 eyes in 1000-centistoke group; 32 eyes in 5000-centistoke group) including cataract, corneal abnormalities, raised IOP, hypotony, vitreous haemorrhage and retinal redetachment. Although visual and anatomical outcomes were comparable between the two groups, the 1000-centistoke silicone oil group developed early oil emulsification necessitating its early removal.

Complex dewetting scenarios of ultrathin silicon films for large-scale nanoarchitectures

PubMed Central

Naffouti, Meher; Backofen, Rainer; Salvalaglio, Marco; Bottein, Thomas; Lodari, Mario; Voigt, Axel; David, Thomas; Benkouider, Abdelmalek; Fraj, Ibtissem; Favre, Luc; Ronda, Antoine; Berbezier, Isabelle; Grosso, David; Abbarchi, Marco; Bollani, Monica

2017-01-01

Dewetting is a ubiquitous phenomenon in nature; many different thin films of organic and inorganic substances (such as liquids, polymers, metals, and semiconductors) share this shape instability driven by surface tension and mass transport. Via templated solid-state dewetting, we frame complex nanoarchitectures of monocrystalline silicon on insulator with unprecedented precision and reproducibility over large scales. Phase-field simulations reveal the dominant role of surface diffusion as a driving force for dewetting and provide a predictive tool to further engineer this hybrid top-down/bottom-up self-assembly method. Our results demonstrate that patches of thin monocrystalline films of metals and semiconductors share the same dewetting dynamics. We also prove the potential of our method by fabricating nanotransfer molding of metal oxide xerogels on silicon and glass substrates. This method allows the novel possibility of transferring these Si-based patterns on different materials, which do not usually undergo dewetting, offering great potential also for microfluidic or sensing applications. PMID:29296680

Complex dewetting scenarios of ultrathin silicon films for large-scale nanoarchitectures.

PubMed

Naffouti, Meher; Backofen, Rainer; Salvalaglio, Marco; Bottein, Thomas; Lodari, Mario; Voigt, Axel; David, Thomas; Benkouider, Abdelmalek; Fraj, Ibtissem; Favre, Luc; Ronda, Antoine; Berbezier, Isabelle; Grosso, David; Abbarchi, Marco; Bollani, Monica

2017-11-01

Dewetting is a ubiquitous phenomenon in nature; many different thin films of organic and inorganic substances (such as liquids, polymers, metals, and semiconductors) share this shape instability driven by surface tension and mass transport. Via templated solid-state dewetting, we frame complex nanoarchitectures of monocrystalline silicon on insulator with unprecedented precision and reproducibility over large scales. Phase-field simulations reveal the dominant role of surface diffusion as a driving force for dewetting and provide a predictive tool to further engineer this hybrid top-down/bottom-up self-assembly method. Our results demonstrate that patches of thin monocrystalline films of metals and semiconductors share the same dewetting dynamics. We also prove the potential of our method by fabricating nanotransfer molding of metal oxide xerogels on silicon and glass substrates. This method allows the novel possibility of transferring these Si-based patterns on different materials, which do not usually undergo dewetting, offering great potential also for microfluidic or sensing applications.

Acousto-defect interaction in irradiated and non-irradiated silicon n+-p structures

NASA Astrophysics Data System (ADS)

Olikh, O. Ya.; Gorb, A. M.; Chupryna, R. G.; Pristay-Fenenkov, O. V.

2018-04-01

The influence of ultrasound on current-voltage characteristics of non-irradiated silicon n+-p structures as well as silicon structures exposed to reactor neutrons or 60Co gamma radiation has been investigated experimentally. It has been found that the ultrasound loading of the n+-p structure leads to the reversible change of shunt resistance, carrier lifetime, and ideality factor. Specifically, considerable acoustically induced alteration of the ideality factor and the space charge region lifetime was observed in the irradiated samples. The experimental results were described by using the models of coupled defect level recombination, Shockley-Read-Hall recombination, and dislocation-induced impedance. The experimentally observed phenomena are associated with the increase in the distance between coupled defects as well as the extension of the carrier capture coefficient of complex point defects and dislocations. It has been shown that divacancies and vacancy-interstitial oxygen pairs are effectively modified by ultrasound in contrast to interstitial carbon-interstitial oxygen complexes.

Measurement of Quantum Interference in a Silicon Ring Resonator Photon Source.

PubMed

Steidle, Jeffrey A; Fanto, Michael L; Preble, Stefan F; Tison, Christopher C; Howland, Gregory A; Wang, Zihao; Alsing, Paul M

2017-04-04

Silicon photonic chips have the potential to realize complex integrated quantum information processing circuits, including photon sources, qubit manipulation, and integrated single-photon detectors. Here, we present the key aspects of preparing and testing a silicon photonic quantum chip with an integrated photon source and two-photon interferometer. The most important aspect of an integrated quantum circuit is minimizing loss so that all of the generated photons are detected with the highest possible fidelity. Here, we describe how to perform low-loss edge coupling by using an ultra-high numerical aperture fiber to closely match the mode of the silicon waveguides. By using an optimized fusion splicing recipe, the UHNA fiber is seamlessly interfaced with a standard single-mode fiber. This low-loss coupling allows the measurement of high-fidelity photon production in an integrated silicon ring resonator and the subsequent two-photon interference of the produced photons in a closely integrated Mach-Zehnder interferometer. This paper describes the essential procedures for the preparation and characterization of high-performance and scalable silicon quantum photonic circuits.

Energy Storage Materials from Nature through Nanotechnology: A Sustainable Route from Reed Plants to a Silicon Anode for Lithium-Ion Batteries.

PubMed

Liu, Jun; Kopold, Peter; van Aken, Peter A; Maier, Joachim; Yu, Yan

2015-08-10

Silicon is an attractive anode material in energy storage devices, as it has a ten times higher theoretical capacity than its state-of-art carbonaceous counterpart. However, the common process to synthesize silicon nanostructured electrodes is complex, costly, and energy-intensive. Three-dimensional (3D) porous silicon-based anode materials have been fabricated from natural reed leaves by calcination and magnesiothermic reduction. This sustainable and highly abundant silica source allows for facile production of 3D porous silicon with very good electrochemical performance. The obtained silicon anode retains the 3D hierarchical architecture of the reed leaf. Impurity leaching and gas release during the fabrication process leads to an interconnected porosity and the reductive treatment to an inside carbon coating. Such anodes show a remarkable Li-ion storage performance: even after 4000 cycles and at a rate of 10 C, a specific capacity of 420 mA h g(-1) is achieved. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Modelling of heating and photoexcitation of single-crystal silicon under multipulse irradiation by a nanosecond laser at 1.06 μm

NASA Astrophysics Data System (ADS)

Polyakov, D. S.; Yakovlev, E. B.

2018-03-01

We report a theoretical study of heating and photoexcitation of single-crystal silicon by nanosecond laser radiation at a wavelength of 1.06 μm. The proposed physicomathematical model of heating takes into account the complex nonlinear dynamics of the interband absorption coefficient of silicon and the contribution of the radial heat removal to the cooling of silicon between pulses under multipulse irradiation, which allows one to obtain a satisfactory agreement between theoretical predictions of silicon melting thresholds at different nanosecond pulse durations and experimental data (both under single-pulse and multipulse irradiation). It is found that under irradiation by nanosecond pulses at a wavelength of 1.06 μm, the dynamic Burshtein–Moss effect can play an important role in processes of photoexcitation and heating. It is shown that with the regimes typical for laser multipulse microprocessing of silicon (the laser spot diameter is less than 100 μm, and the repetition rate of pulses is about 100 kHz), the radial heat removal cannot be neglected in the analysis of heat accumulation processes.

2-Acylpyrroles as mono-anionic O,N-chelating ligands in silicon coordination chemistry.

PubMed

Kämpfe, Alexander; Brendler, Erica; Kroke, Edwin; Wagler, Jörg

2014-07-21

Kryptopyrrole (2,4-dimethyl-3-ethylpyrrole) was acylated with, for example, benzoyl chloride to afford 2-benzoyl-3,5-dimethyl-4-ethylpyrrole (L(1)H). With SiCl4 this ligand reacts under liberation of HCl and formation of the complex L(1)2SiCl2. In related reactions with HSiCl3 or H2SiCl2, the same chlorosilicon complex is formed under liberation of HCl and H2 or liberation of H2, respectively. The chlorine atoms of L(1)2SiCl2 can be replaced by fluoride and triflate using ZnF2 and Me3Si-OTf, respectively. The use of a supporting base (triethylamine) is required for the complexation of phenyltrichlorosilane and diphenyldichlorosilane. The complexes L(1)2SiCl2, L(1)2SiF2, L(1)2Si(OTf)2, L(1)2SiPhCl, and L(1)2SiPh2 exhibit various configurations of the octahedral silicon coordination spheres (i.e. cis or trans configuration of the monodentate substituents, different orientations of the bidentate chelating ligands relative to each other). Furthermore, cationic silicon complexes L(1)3Si(+) and L(1) SiPh(+) were synthesized by chloride abstraction with GaCl3. In contrast, reaction of L(1)2SiCl2 with a third equivalent of L(1)H in the presence of excess triethylamine produced a charge-neutral hexacoordinate Si complex with a new tetradentate chelating ligand which formed by Si-templated C-C coupling of two ligands L(1). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Three Dimensional Positron Annihilation Momentum Spectroscopy of Lithium Tetraborate Crystals

DTIC Science & Technology

2013-03-21

Technique Applied to Measure Oxygen-Atom Defects in 6H Silicon Carbide ." AFIT PhD Dissertation. AFIT/DS/ENP/10-M02, (Mar 2010) [4] Charlton, M., and...of Experimental Observables of Positron-Vacancy Complexes in Silicon Carbide .” Ph.D. dissertation, Air Force Institute of Technology, 2005. [18...Resonances ............................ 19 2.1.2 3D Positron Annihilation Momentum Measurements (3DPAMMs) of 6H SiC

Study of phenomena related to the sintering process of silicon nitride at atmospheric pressure

NASA Technical Reports Server (NTRS)

Bertani, A.

1982-01-01

A procedure was perfected for the production of components used in engineering applications of silicon nitride. Particles of complex geometry that combine remarkable mechanical properties with a high density are obtained. The process developed, in contrast to the "hot pressing" method, does not use external pressures, and in contrast to the reaction bonding method, final densities close to the theoretical value are obtained.

Development of drug delivery systems based on nanostructured porous silicon loaded with the anti-tumoral drug emodin adsorbed on silver nanoparticles

NASA Astrophysics Data System (ADS)

Hernández, Margarita; Recio, Gonzalo; Sevilla, Paz; Torres-Costa, Vicente; García-Ramos, José V.; Domingo, Concepción; Martín-Palma, Raúl J. J.

2012-10-01

A study of the fluorescence and Raman spectra of a new and complex drug delivery system formed by emodin adsorbed on silver nanoparticles embedded into a matrix of porous silicon is here reported. Several experimental methods of inclusion of the drug-silver set inside the pores, without previous functionalization of porous silicon, have been tested in order to optimize the conditions for the fluorescence detection of emodin. In this sense, we have also added bovine serum albumin to the system, finding that the presence of the protein enhances the fluores-cence signal from emodin.

Low temperature solution synthesis of silicon, germanium and Si-Ge axial heterostructures in nanorod and nanowire form.

PubMed

Flynn, G; Stokes, K; Ryan, K M

2018-05-31

Herein, we report the formation of silicon, germanium and more complex Si-SixGe1-x and Si-Ge axial 1D heterostructures, at low temperatures in solution. These nanorods/nanowires are grown using phenylated compounds of silicon and germanium as reagents, with precursor decomposition achieved at substantially reduced temperatures (200 °C for single crystal nanostructures and 300 °C for heterostructures), through the addition of a reducing agent. This low energy route for the production of these functional nanostructures as a wet chemical in high yield is attractive to meet the processing needs for next generation photovoltaics, batteries and electronics.

An anisotropic thermal-stress model for through-silicon via

NASA Astrophysics Data System (ADS)

Liu, Song; Shan, Guangbao

2018-02-01

A two-dimensional thermal-stress model of through-silicon via (TSV) is proposed considering the anisotropic elastic property of the silicon substrate. By using the complex variable approach, the distribution of thermal-stress in the substrate can be characterized more accurately. TCAD 3-D simulations are used to verify the model accuracy and well agree with analytical results (< ±5%). The proposed thermal-stress model can be integrated into stress-driven design flow for 3-D IC , leading to the more accurate timing analysis considering the thermal-stress effect. Project supported by the Aerospace Advanced Manufacturing Technology Research Joint Fund (No. U1537208).

The Electrochemical Fluorination of Organosilicon Compounds

NASA Technical Reports Server (NTRS)

Seaver, Robert E.

1961-01-01

The electrochemical fluorination of tetramethylsilane, hexamethyl-disiloxane, diethyldichlorosilane, amyltrichlorosilane, and phenyltri-chlorosilane was conducted in an Inconel cell equipped with nickel electrodes. A potential of approximately 5.0 volts and a current of approximately 1.0 ampere were used for the electrolysis reaction. In all cases the fluorinations resulted in considerable scission of the carbon-silicon bonds yielding hydrogen and the various fluorinated decomposition products; no fluoroorganosilicon compounds were identified. The main decomposition products were silicon tetrafluoride, the corresponding fluorinated carbon compounds, and the various organofluorosilanes. It is suggested that this is due to the nucleophilic attack of the fluoride ion (or complex fluoride ion) on the carbon-silicon bond.

Joining and Assembly of Silicon Carbide-based Advanced Ceramics and Composites for High Temperature Applications

NASA Technical Reports Server (NTRS)

Singh, M.

2004-01-01

Silicon carbide based advanced ceramics and fiber reinforced composites are under active consideration for use in wide variety of high temperature applications within the aeronautics, space transportation, energy, and nuclear industries. The engineering designs of ceramic and composite component require fabrication and manufacturing of large and complex shaped parts of various thicknesses. In many instances, it is more economical to build up complex shapes by joining simple geometrical shapes. In addition these components have to be joined or assembled with metallic sub-components. Thus, joining and attachment have been recognized as enabling technologies for successful utilization of ceramic components in various demanding applications. In this presentation, various challenges and opportunities in design, fabrication, and testing o high temperature joints in ceramic matrix composites will be presented. Silicon carbide based advanced ceramics (CVD and hot pressed), and C/SiC and SiC/SiC composites, in different shapes and sizes, have been joined using an affordable, robust ceramic joining technology (ARCJoinT). Microstructure and high temperature mechanical properties of joints in silicon carbide ceramics and CVI and melt infiltrated SiC matrix composites will,be reported. Various joint design philosophies and design issues in joining of ceramics and composites well be discussed.

Advanced Silicon-on-Insulator: Crystalline Silicon on Atomic Layer Deposited Beryllium Oxide.

PubMed

Min Lee, Seung; Hwan Yum, Jung; Larsen, Eric S; Chul Lee, Woo; Keun Kim, Seong; Bielawski, Christopher W; Oh, Jungwoo

2017-10-16

Silicon-on-insulator (SOI) technology improves the performance of devices by reducing parasitic capacitance. Devices based on SOI or silicon-on-sapphire technology are primarily used in high-performance radio frequency (RF) and radiation sensitive applications as well as for reducing the short channel effects in microelectronic devices. Despite their advantages, the high substrate cost and overheating problems associated with complexities in substrate fabrication as well as the low thermal conductivity of silicon oxide prevent broad applications of this technology. To overcome these challenges, we describe a new approach of using beryllium oxide (BeO). The use of atomic layer deposition (ALD) for producing this material results in lowering the SOI wafer production cost. Furthermore, the use of BeO exhibiting a high thermal conductivity might minimize the self-heating issues. We show that crystalline Si can be grown on ALD BeO and the resultant devices exhibit potential for use in advanced SOI technology applications.

Controlling the Nanoscale Patterning of AuNPs on Silicon Surfaces

PubMed Central

Williams, Sophie E.; Davies, Philip R.; Bowen, Jenna L.; Allender, Chris J.

2013-01-01

This study evaluates the effectiveness of vapour-phase deposition for creating sub-monolayer coverage of aminopropyl triethoxysilane (APTES) on silicon in order to exert control over subsequent gold nanoparticle deposition. Surface coverage was evaluated indirectly by observing the extent to which gold nanoparticles (AuNPs) deposited onto the modified silicon surface. By varying the distance of the silicon wafer from the APTES source and concentration of APTES in the evaporating media, control over subsequent gold nanoparticle deposition was achievable to an extent. Fine control over AuNP deposition (AuNPs/μm2) however, was best achieved by adjusting the ionic concentration of the AuNP-depositing solution. Furthermore it was demonstrated that although APTES was fully removed from the silicon surface following four hours incubation in water, the gold nanoparticle-amino surface complex was stable under the same conditions. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to study these affects. PMID:28348330

Surface Attachment of Gold Nanoparticles Guided by Block Copolymer Micellar Films and Its Application in Silicon Etching

PubMed Central

Wei, Mingjie; Wang, Yong

2015-01-01

Patterning metallic nanoparticles on substrate surfaces is important in a number of applications. However, it remains challenging to fabricate such patterned nanoparticles with easily controlled structural parameters, including particle sizes and densities, from simple methods. We report on a new route to directly pattern pre-formed gold nanoparticles with different diameters on block copolymer micellar monolayers coated on silicon substrates. Due to the synergetic effect of complexation and electrostatic interactions between the micellar cores and the gold particles, incubating the copolymer-coated silicon in a gold nanoparticles suspension leads to a monolayer of gold particles attached on the coated silicon. The intermediate micellar film was then removed using oxygen plasma treatment, allowing the direct contact of the gold particles with the Si substrate. We further demonstrate that the gold nanoparticles can serve as catalysts for the localized etching of the silicon substrate, resulting in nanoporous Si with a top layer of straight pores. PMID:28793407

Nanotribological effects of silicone type, silicone deposition level, and surfactant type on human hair using atomic force microscopy.

PubMed

La Torre, Carmen; Bhushan, Bharat

2006-01-01

The atomic/friction force microscope (AFM/FFM) has recently become an important tool for studying the micro/nanoscale structure and tribological properties of human hair. Of particular interest to hair and beauty care science is how common hair-care materials, such as conditioner, deposit onto and change hair's tribological properties, since these properties are closely tied to product performance. Since a conditioner is a complex network of many different ingredients (including silicones for lubrication and cationic surfactants for static control and gel network formulation), studying the effects of these individual components can give insight into the significance each has on hair properties. In this study, AFM/FFM is used to conduct nanotribological studies of surface roughness, friction force, and adhesive forces as a function of silicone type, silicone deposition level, and cationic surfactant type. Changes in the coefficient of friction as a result of soaking hair in de-ionized water are also discussed.

Simple processing of back-contacted silicon heterojunction solar cells using selective-area crystalline growth

NASA Astrophysics Data System (ADS)

Tomasi, Andrea; Paviet-Salomon, Bertrand; Jeangros, Quentin; Haschke, Jan; Christmann, Gabriel; Barraud, Loris; Descoeudres, Antoine; Seif, Johannes Peter; Nicolay, Sylvain; Despeisse, Matthieu; de Wolf, Stefaan; Ballif, Christophe

2017-04-01

For crystalline-silicon solar cells, voltages close to the theoretical limit are nowadays readily achievable when using passivating contacts. Conversely, maximal current generation requires the integration of the electron and hole contacts at the back of the solar cell to liberate its front from any shadowing loss. Recently, the world-record efficiency for crystalline-silicon single-junction solar cells was achieved by merging these two approaches in a single device; however, the complexity of fabricating this class of devices raises concerns about their commercial potential. Here we show a contacting method that substantially simplifies the architecture and fabrication of back-contacted silicon solar cells. We exploit the surface-dependent growth of silicon thin films, deposited by plasma processes, to eliminate the patterning of one of the doped carrier-collecting layers. Then, using only one alignment step for electrode definition, we fabricate a proof-of-concept 9-cm2 tunnel-interdigitated back-contact solar cell with a certified conversion efficiency >22.5%.

Challenges and solutions for high-volume testing of silicon photonics

NASA Astrophysics Data System (ADS)

Polster, Robert; Dai, Liang Yuan; Oikonomou, Michail; Cheng, Qixiang; Rumley, Sebastien; Bergman, Keren

2018-02-01

The first generation of silicon photonic products is now commercially available. While silicon photonics possesses key economic advantages over classical photonic platforms, it has yet to become a commercial success because these advantages can be fully realized only when high-volume testing of silicon photonic devices is made possible. We discuss the costs, challenges, and solutions of photonic chip testing as reported in the recent research literature. We define and propose three underlying paradigms that should be considered when creating photonic test structures: Design for Fast Coupling, Design for Minimal Taps, and Design for Parallel Testing. We underline that a coherent test methodology must be established prior to the design of test structures, and demonstrate how an optimized methodology dramatically reduces the burden when designing for test, by reducing the needed complexity of test structures.

Use of silicon oxynitride as a sacrificial material for microelectromechanical devices

DOEpatents

Habermehl, Scott D.; Sniegowski, Jeffry J.

2001-01-01

The use of silicon oxynitride (SiO.sub.x N.sub.y) as a sacrificial material for forming a microelectromechanical (MEM) device is disclosed. Whereas conventional sacrificial materials such as silicon dioxide and silicate glasses are compressively strained, the composition of silicon oxynitride can be selected to be either tensile-strained or substantially-stress-free. Thus, silicon oxynitride can be used in combination with conventional sacrificial materials to limit an accumulation of compressive stress in a MEM device; or alternately the MEM device can be formed entirely with silicon oxynitride. Advantages to be gained from the use of silicon oxynitride as a sacrificial material for a MEM device include the formation of polysilicon members that are substantially free from residual stress, thereby improving the reliability of the MEM device; an ability to form the MEM device with a higher degree of complexity and more layers of structural polysilicon than would be possible using conventional compressively-strained sacrificial materials; and improved manufacturability resulting from the elimination of wafer distortion that can arise from an excess of accumulated stress in conventional sacrificial materials. The present invention is useful for forming many different types of MEM devices including accelerometers, sensors, motors, switches, coded locks, and flow-control devices, with or without integrated electronic circuitry.

Low temperature plasma enhanced CVD epitaxial growth of silicon on GaAs: a new paradigm for III-V/Si integration

NASA Astrophysics Data System (ADS)

Cariou, Romain; Chen, Wanghua; Maurice, Jean-Luc; Yu, Jingwen; Patriarche, Gilles; Mauguin, Olivia; Largeau, Ludovic; Decobert, Jean; Roca I Cabarrocas, Pere

2016-05-01

The integration of III-V semiconductors with silicon is a key issue for photonics, microelectronics and photovoltaics. With the standard approach, namely the epitaxial growth of III-V on silicon, thick and complex buffer layers are required to limit the crystalline defects caused by the interface polarity issues, the thermal expansion, and lattice mismatches. To overcome these problems, we have developed a reverse and innovative approach to combine III-V and silicon: the straightforward epitaxial growth of silicon on GaAs at low temperature by plasma enhanced CVD (PECVD). Indeed we show that both GaAs surface cleaning by SiF4 plasma and subsequent epitaxial growth from SiH4/H2 precursors can be achieved at 175 °C. The GaAs native oxide etching is monitored with in-situ spectroscopic ellipsometry and Raman spectroscopy is used to assess the epitaxial silicon quality. We found that SiH4 dilution in hydrogen during deposition controls the layer structure: the epitaxial growth happens for deposition conditions at the transition between the microcrystalline and amorphous growth regimes. SIMS and STEM-HAADF bring evidences for the interface chemical sharpness. Together, TEM and XRD analysis demonstrate that PECVD enables the growth of high quality relaxed single crystal silicon on GaAs.

Effect of the order of He{sup +} and H{sup +} ion co-implantation on damage generation and thermal evolution of complexes, platelets, and blisters in silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Daghbouj, N.; Faculté des Sciences de Monastir, Université de Monastir, Monastir; Cherkashin, N., E-mail: nikolay.cherkashin@cemes.fr

2016-04-07

Hydrogen and helium co-implantation is nowadays used to efficiently transfer thin Si layers and fabricate silicon on insulator wafers for the microelectronic industry. The synergy between the two implants which is reflected through the dramatic reduction of the total fluence needed to fracture silicon has been reported to be strongly influenced by the implantation order. Contradictory conclusions on the mechanisms involved in the formation and thermal evolution of defects and complexes have been drawn. In this work, we have experimentally studied in detail the characteristics of Si samples co-implanted with He and H, comparing the defects which are formed followingmore » each implantation and after annealing. We show that the second implant always ballistically destroys the stable defects and complexes formed after the first implant and that the redistribution of these point defects among new complexes drives the final difference observed in the samples after annealing. When H is implanted first, He precipitates in the form of nano-bubbles and agglomerates within H-related platelets and nano-cracks. When He is implanted first, the whole He fluence is ultimately used to pressurize H-related platelets which quickly evolve into micro-cracks and surface blisters. We provide detailed scenarios describing the atomic mechanisms involved during and after co-implantation and annealing which well-explain our results and the reasons for the apparent contradictions reported at the state of the art.« less

Confined Li ion migration in the silicon-graphene complex system: An ab initio investigation

NASA Astrophysics Data System (ADS)

Wang, Guoqing; Xu, Bo; Shi, Jing; Lei, Xueling; Ouyang, Chuying

2018-04-01

Silicon-Carbon complex systems play an important role in enhancing the performance of Si-based anode materials for Li ion batteries. In this work, the Li migration property of the Silicon-Graphene (Si-Gr) complex systems are investigated by using first-principles calculations. Especially, the effects of graphene coating on the migration of Li ions are discussed in detail. The distance between Si surface and graphene in the Si-Gr system significantly affects the lateral migration of Li ions. With the decrease of the distance from 4.715 to 3.844 Å, the energy barrier of Li ion migration also decreases from 0.115 to 0.067 eV, which are all lower than that of the case without graphene d(0.135 eV). However, smaller distance (3.586 Å) brings the high energy barrier (0.237 eV). Through AIMD calculations, it is found that the graphene coating in the Si-Gr complex system would result in the larger intercalation depths, more uniform distributions, and higher migration coefficients of Li ions. Further calculations of migration coefficients of Li ions at different temperature are used to obtained the activation energy for Li ions migration in the Si-Gr system, which is as low as 0.028 eV. This low activation energy shows that it is easy for Li ions migrating in the Si-Gr system. Our study provided the basically information to understand the migration mechanism of Li ions in Si-C system.

A Thermodynamic Model to Estimate the Formation of Complex Nitrides of Al x Mg(1- x)N in Silicon Steel

NASA Astrophysics Data System (ADS)

Luo, Yan; Zhang, Lifeng; Li, Ming; Sridhar, Seetharaman

2018-06-01

A complex nitride of Al x Mg(1- x)N was observed in silicon steels. A thermodynamic model was developed to predict the ferrite/nitride equilibrium in the Fe-Al-Mg-N alloy system, using published binary solubility products for stoichiometric phases. The model was used to estimate the solubility product of nitride compound, equilibrium ferrite, and nitride compositions, and the amounts of each phase, as a function of steel composition and temperature. In the current model, the molar ratio Al/(Al + Mg) in the complex nitride was great due to the low dissolved magnesium in steel. For a steel containing 0.52 wt pct Als, 10 ppm T.Mg., and 20 ppm T.N. at 1100 K (827 °C), the complex nitride was expressed by Al0.99496Mg0.00504N and the solubility product of this complex nitride was 2.95 × 10-7. In addition, the solution temperature of the complex nitride increased with increasing the nitrogen and aluminum in steel. The good agreement between the prediction and the detected precipitate compositions validated the current model.

Conductance of kinked nanowires

NASA Astrophysics Data System (ADS)

Cook, B. G.; Varga, K.

2011-01-01

The conductance properties of kinked nanowires are studied by first-principles transport calculations within a recently developed complex potential framework. Using prototypical examples of monoatomic Au chains as well as small diameter single-crystalline silicon nanowires we show that transmission strongly depends on the kink geometry and one can tune the conductance properties by the kink angle and other geometrical factors. In the case of a silicon nanowire the presence of a kink drastically reduces the conductance.

High precision measurement of silicon in naphthas by ICP-OES using isooctane as diluent.

PubMed

Gazulla, M F; Rodrigo, M; Orduña, M; Ventura, M J; Andreu, C

2017-03-01

An analytical protocol for the accurate and precise determination of Si in naphthas is presented by using ICP-OES, optimizing from the sample preparation to the measurement conditions, in order to be able to analyze for the first time silicon contents below 100µgkg -1 in a relatively short time thus being used as a control method. In the petrochemical industry, silicon can be present as a contaminant in different petroleum products such as gasoline, ethanol, or naphthas, forming different silicon compounds during the treatment of these products that are irreversibly adsorbed onto catalyst surfaces decreasing its time life. The complex nature of the organic naphtha sample together with the low detection limits needed make the analysis of silicon quite difficult. The aim of this work is to optimize the measurement of silicon in naphthas by ICP-OES introducing as an improvement the use of isooctane as diluent. The set up was carried out by optimizing the measurement conditions (power, nebulizer flow, pump rate, read time, and viewing mode) and the sample preparation (type of diluent, cleaning process, blanks, and studying various dilution ratios depending on the sample characteristics). Copyright © 2016 Elsevier B.V. All rights reserved.

Inelastic response of silicon to shock compression.

PubMed

Higginbotham, A; Stubley, P G; Comley, A J; Eggert, J H; Foster, J M; Kalantar, D H; McGonegle, D; Patel, S; Peacock, L J; Rothman, S D; Smith, R F; Suggit, M J; Wark, J S

2016-04-13

The elastic and inelastic response of [001] oriented silicon to laser compression has been a topic of considerable discussion for well over a decade, yet there has been little progress in understanding the basic behaviour of this apparently simple material. We present experimental x-ray diffraction data showing complex elastic strain profiles in laser compressed samples on nanosecond timescales. We also present molecular dynamics and elasticity code modelling which suggests that a pressure induced phase transition is the cause of the previously reported 'anomalous' elastic waves. Moreover, this interpretation allows for measurement of the kinetic timescales for transition. This model is also discussed in the wider context of reported deformation of silicon to rapid compression in the literature.

Direct Human Contact with Siloxanes (Silicones) – Safety or Risk Part 1. Characteristics of Siloxanes (Silicones)

PubMed Central

Mojsiewicz-Pieńkowska, Krystyna; Jamrógiewicz, Marzena; Szymkowska, Katarzyna; Krenczkowska, Dominika

2016-01-01

Siloxanes are commonly known as silicones. They belong to the organosilicon compounds and are exclusively obtained by synthesis. Their chemical structure determines a range of physicochemical properties which were recognized as unique. Due to the susceptibility to chemical modifications, ability to create short, long or complex polymer particles, siloxanes found an application in many areas of human life. Siloxanes differ in particle size, molecular weight, shape and chemical groups. As a result, this determines the different physico-chemical properties, that directly affect the safety or the risk of their use. The areas that can be a source of danger to human health will be commented in this paper. PMID:27303296

Implementation Challenges for Sintered Silicon Carbide Fiber Bonded Ceramic Materials for High Temperature Applications

NASA Technical Reports Server (NTRS)

Singh, M.

2011-01-01

During the last decades, a number of fiber reinforced ceramic composites have been developed and tested for various aerospace and ground based applications. However, a number of challenges still remain slowing the wide scale implementation of these materials. In addition to continuous fiber reinforced composites, other innovative materials have been developed including the fibrous monoliths and sintered fiber bonded ceramics. The sintered silicon carbide fiber bonded ceramics have been fabricated by the hot pressing and sintering of silicon carbide fibers. However, in this system reliable property database as well as various issues related to thermomechanical performance, integration, and fabrication of large and complex shape components has yet to be addressed. In this presentation, thermomechanical properties of sintered silicon carbide fiber bonded ceramics (as fabricated and joined) will be presented. In addition, critical need for manufacturing and integration technologies in successful implementation of these materials will be discussed.

Quantum interference in heterogeneous superconducting-photonic circuits on a silicon chip.

PubMed

Schuck, C; Guo, X; Fan, L; Ma, X; Poot, M; Tang, H X

2016-01-21

Quantum information processing holds great promise for communicating and computing data efficiently. However, scaling current photonic implementation approaches to larger system size remains an outstanding challenge for realizing disruptive quantum technology. Two main ingredients of quantum information processors are quantum interference and single-photon detectors. Here we develop a hybrid superconducting-photonic circuit system to show how these elements can be combined in a scalable fashion on a silicon chip. We demonstrate the suitability of this approach for integrated quantum optics by interfering and detecting photon pairs directly on the chip with waveguide-coupled single-photon detectors. Using a directional coupler implemented with silicon nitride nanophotonic waveguides, we observe 97% interference visibility when measuring photon statistics with two monolithically integrated superconducting single-photon detectors. The photonic circuit and detector fabrication processes are compatible with standard semiconductor thin-film technology, making it possible to implement more complex and larger scale quantum photonic circuits on silicon chips.

Electron impact ionization of plasma important SiClX (X = 1-4) molecules: theoretical cross sections

NASA Astrophysics Data System (ADS)

Kothari, Harshit N.; Pandya, Siddharth H.; Joshipura, K. N.

2011-06-01

Electron impact ionization of SiClX (X = 1-4) molecules is less studied but an important process for understanding and modelling the interactions of silicon-chlorine plasmas with different materials. The SiCl3 radical is a major chloro-silicon species involved in the CVD (chemical vapour deposition) of silicon films from SiCl4/Ar microwave plasmas. We report in this paper the total ionization cross sections for electron collisions on these silicon compounds at incident energies from the ionization threshold to 2000 eV. We employ the 'complex scattering potential-ionization contribution' method and identify the relative importance of various channels, with ionization included in the cumulative inelastic scattering. New results are also presented on these exotic molecular targets. This work is significant in view of the paucity of theoretical studies on the radicals SiClX (X = 1-3) and on SiCl4.

Bidisperse silica nanoparticles close-packed monolayer on silicon substrate by three step spin method

NASA Astrophysics Data System (ADS)

Khanna, Sakshum; Marathey, Priyanka; Utsav, Chaliawala, Harsh; Mukhopadhyay, Indrajit

2018-05-01

We present the studies on the structural properties of monolayer Bidisperse silica (SiO2) nanoparticles (BDS) on Silicon (Si-100) substrate using spin coating technique. The Bidisperse silica nanoparticle was synthesised by the modified sol-gel process. Nanoparticles on the substrate are generally assembled in non-close/close-packed monolayer (CPM) form. The CPM form is obtained by depositing the colloidal suspension onto the silicon substrate using complex techniques. Here we report an effective method for forming a monolayer of bidisperse silica nanoparticle by three step spin coating technique. The samples were prepared by mixing the monodisperse solutions of different particles size 40 and 100 nm diameters. The bidisperse silica nanoparticles were self-assembled on the silicon substrate forming a close-packed monolayer film. The scanning electron microscope images of bidisperse films provided in-depth film structure of the film. The maximum surface coverage obtained was around 70-80%.

A review of molecular beam epitaxy of ferroelectric BaTiO3 films on Si, Ge and GaAs substrates and their applications

PubMed Central

Mazet, Lucie; Yang, Sang Mo; Kalinin, Sergei V; Schamm-Chardon, Sylvie; Dubourdieu, Catherine

2015-01-01

SrTiO3 epitaxial growth by molecular beam epitaxy (MBE) on silicon has opened up the route to the monolithic integration of various complex oxides on the complementary metal-oxide–semiconductor silicon platform. Among functional oxides, ferroelectric perovskite oxides offer promising perspectives to improve or add functionalities on-chip. We review the growth by MBE of the ferroelectric compound BaTiO3 on silicon (Si), germanium (Ge) and gallium arsenide (GaAs) and we discuss the film properties in terms of crystalline structure, microstructure and ferroelectricity. Finally, we review the last developments in two areas of interest for the applications of BaTiO3 films on silicon, namely integrated photonics, which benefits from the large Pockels effect of BaTiO3, and low power logic devices, which may benefit from the negative capacitance of the ferroelectric. PMID:27877816

High Temperature Joining and Characterization of Joint Properties in Silicon Carbide-Based Composite Materials

NASA Technical Reports Server (NTRS)

Halbig, Michael C.; Singh, Mrityunjay

2015-01-01

Advanced silicon carbide-based ceramics and composites are being developed for a wide variety of high temperature extreme environment applications. Robust high temperature joining and integration technologies are enabling for the fabrication and manufacturing of large and complex shaped components. The development of a new joining approach called SET (Single-step Elevated Temperature) joining will be described along with the overview of previously developed joining approaches including high temperature brazing, ARCJoinT (Affordable, Robust Ceramic Joining Technology), diffusion bonding, and REABOND (Refractory Eutectic Assisted Bonding). Unlike other approaches, SET joining does not have any lower temperature phases and will therefore have a use temperature above 1315C. Optimization of the composition for full conversion to silicon carbide will be discussed. The goal is to find a composition with no remaining carbon or free silicon. Green tape interlayers were developed for joining. Microstructural analysis and preliminary mechanical tests of the joints will be presented.

Multifunctional silicon surfaces: reaction of dichlorocarbene generated from Seyferth reagent with hydrogen-terminated silicon (111) surfaces.

PubMed

Liu, Wenjun; Sharp, Ian D; Tilley, T Don

2014-01-14

Insertion of dichlorocarbene (:CCl2), generated by decomposition of the Seyferth reagent PhHgCCl2Br, into the Si-H bond of a tertiary silane to form a Si-CCl2H group is an efficient homogeneous, molecular transformation. A heterogeneous version of this reaction, between PhHgCCl2Br and a silicon (111) surface terminated by tertiary Si-H bonds, was studied using a combination of surface-sensitive infrared and X-ray photoelectron spectroscopies. The insertion of dichlorocarbene into surface Si-H bonds parallels the corresponding reaction of silanes in solution, to produce surface-bound dichloromethyl groups (Si-CCl2H) covering ∼25% of the silicon surface sites. A significant fraction of the remaining Si-H bonds on the surface was converted to Si-Cl/Br groups during the same reaction, with PhHgCCl2Br serving as a halogen atom source. The presence of two distinct environments for the chlorine atoms (Si-CCl2H and Si-Cl) and one type of bromine atom (Si-Br) was confirmed by Cl 2p, Br 3d, and C 1s X-ray photoelectron spectroscopy. The formation of reactive, halogen-terminated atop silicon sites was also verified by reaction with sodium azide or the Grignard reagent (CH3MgBr), to produce Si-N3 or Si-Me functionalities, respectively. Thus, reaction of a hydrogen-terminated silicon (111) surface with PhHgCCl2Br provides a facile route to multifunctional surfaces possessing both stable silicon-carbon and labile silicon-halogen sites, in a single pot synthesis. The reactive silicon-halogen groups can be utilized for subsequent transformations and, potentially, the construction of more complex organic-silicon hybrid systems.

Silicon supported lipid-DNA thin film structures at varying temperature studied by energy dispersive X-ray diffraction and neutron reflectivity.

PubMed

Domenici, F; Castellano, C; Dell'Unto, F; Albinati, A; Congiu, A

2011-11-01

Non-viral gene transfection by means of lipid-based nanosystems, such as solid supported lipid assemblies, is often limited due to their lack of stability and the consequent loss of efficiency. Therefore not only a detailed thermo-lyotropic study of these DNA-lipid complexes is necessary to understand their interaction mechanisms, but it can also be considered as a first step in conceiving and developing new transfection biosystems. The aim of our study is a structural characterization of 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC)-dimethyl-dioctadecyl-ammonium bromide (DDAB)-DNA complex at varying temperature using the energy dispersive X-ray diffraction (EDXD) and neutron reflectivity (NR) techniques. We have shown the formation of a novel thermo-lyotropic structure of DOPC/DDAB thin film self-organized in multi-lamellar planes on (100)-oriented silicon support by spin coating, thus enlightening its ability to include DNA strands. Our NR measurements indicate that the DOPC/DDAB/DNA complex forms temperature-dependent structures. At 65°C and relative humidity of 100% DNA fragments are buried between single lamellar leaflets constituting the hydrocarbon core of the lipid bilayers. This finding supports the consistency of the hydrophobic interaction model, which implies that the coupling between lipid tails and hypo-hydrated DNA single strands could be the driving force of DNA-lipid complexation. Upon cooling to 25°C, EDXD analysis points out that full-hydrated DOPC-DDAB-DNA can switch in a different metastable complex supposed to be driven by lipid heads-DNA electrostatic interaction. Thermotropic response analysis also clarifies that DOPC has a pivotal role in promoting the formation of our observed thermophylic silicon supported lipids-DNA assembly. Copyright © 2011 Elsevier B.V. All rights reserved.

Towards Countering the Rise of the Silicon Trojan

DTIC Science & Technology

The Trojan Horse has a venerable if unwelcome history and it is still regarded by many as the primary component in Computer Network Attack. Trojans ... Trojans have in the vast majority taken the form of malicious software. However, more recent times have seen the emergence of what has been dubbed by some...as the ’Silicon Trojan ’ these trojans are embedded at the hardware level and can be designed directly into chips and devices. The complexity of the

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kozlovski, V. V.; Lebedev, A. A.; Bogdanova, E. V.

The model of conductivity compensation in SiC under irradiation with high-energy electrons is presented. The following processes are considered to cause a decrease in the free carrier concentration: (i) formation of deep traps by intrinsic point defects, Frenkel pairs produced by irradiation; (ii) 'deactivation' of the dopant via formation of neutral complexes including a dopant atom and a radiation-induced point defect; and (iii) formation of deep compensating traps via generation of charged complexes constituted by a dopant atom and a radiation-induced point defect. To determine the compensation mechanism, dose dependences of the deep compensation of moderately doped SiC (CVD) undermore » electron irradiation have been experimentally studied. It is demonstrated that, in contrast to n-FZ-Si, moderately doped SiC (CVD) exhibits linear dependences (with a strongly nonlinear dependence observed for Si). Therefore, the conductivity compensation in silicon carbide under electron irradiation occurs due to deep traps formed by primary radiation defects (vacancies and interstitial atoms) in the silicon and carbon sublattices. It is known that the compensation in silicon is due to the formation of secondary radiation defects that include a dopant atom. It is shown that, in contrast to n-SiC (CVD), primary defects in only the carbon sublattice of moderately doped p-SiC (CVD) cannot account for the compensation process. In p-SiC, either primary defects in the silicon sublattice or defects in both sublattices are responsible for the conductivity compensation.« less

Novel method for measurement of transistor gate length using energy-filtered transmission electron microscopy

NASA Astrophysics Data System (ADS)

Lee, Sungho; Kim, Tae-Hoon; Kang, Jonghyuk; Yang, Cheol-Woong

2016-12-01

As the feature size of devices continues to decrease, transmission electron microscopy (TEM) is becoming indispensable for measuring the critical dimension (CD) of structures. Semiconductors consist primarily of silicon-based materials such as silicon, silicon dioxide, and silicon nitride, and the electrons transmitted through a plan-view TEM sample provide diverse information about various overlapped silicon-based materials. This information is exceedingly complex, which makes it difficult to clarify the boundary to be measured. Therefore, we propose a simple measurement method using energy-filtered TEM (EF-TEM). A precise and effective measurement condition was obtained by determining the maximum value of the integrated area ratio of the electron energy loss spectrum at the boundary to be measured. This method employs an adjustable slit allowing only electrons with a certain energy range to pass. EF-TEM imaging showed a sharp transition at the boundary when the energy-filter’s passband centre was set at 90 eV, with a slit width of 40 eV. This was the optimum condition for the CD measurement of silicon-based materials involving silicon nitride. Electron energy loss spectroscopy (EELS) and EF-TEM images were used to verify this method, which makes it possible to measure the transistor gate length in a dynamic random access memory manufactured using 35 nm process technology. This method can be adapted to measure the CD of other non-silicon-based materials using the EELS area ratio of the boundary materials.

Reduced Moment-Based Models for Oxygen Precipitates and Dislocation Loops in Silicon

NASA Astrophysics Data System (ADS)

Trzynadlowski, Bart

The demand for ever smaller, higher-performance integrated circuits and more efficient, cost-effective solar cells continues to push the frontiers of process technology. Fabrication of silicon devices requires extremely precise control of impurities and crystallographic defects. Failure to do so not only reduces performance, efficiency, and yield, it threatens the very survival of commercial enterprises in today's fiercely competitive and price-sensitive global market. The presence of oxygen in silicon is an unavoidable consequence of the Czochralski process, which remains the most popular method for large-scale production of single-crystal silicon. Oxygen precipitates that form during thermal processing cause distortion of the surrounding silicon lattice and can lead to the formation of dislocation loops. Localized deformation caused by both of these defects introduces potential wells that trap diffusing impurities such as metal atoms, which is highly desirable if done far away from sensitive device regions. Unfortunately, dislocations also reduce the mechanical strength of silicon, which can cause wafer warpage and breakage. Engineers must negotiate this and other complex tradeoffs when designing fabrication processes. Accomplishing this in a complex, modern process involving a large number of thermal steps is impossible without the aid of computational models. In this dissertation, new models for oxygen precipitation and dislocation loop evolution are described. An oxygen model using kinetic rate equations to evolve the complete precipitate size distribution was developed first. This was then used to create a reduced model tracking only the moments of the size distribution. The moment-based model was found to run significantly faster than its full counterpart while accurately capturing the evolution of oxygen precipitates. The reduced model was fitted to experimental data and a sensitivity analysis was performed to assess the robustness of the results. Source code for both models is included. A moment-based model for dislocation loop formation from {311} defects in ion-implanted silicon was also developed and validated against experimental data. Ab initio density functional theory calculations of stacking faults and edge dislocations were performed to extract energies and elastic properties. This allowed the effect of applied stress on the evolution of {311} defects and dislocation loops to be investigated.

Alternative process for thin layer etching: Application to nitride spacer etching stopping on silicon germanium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Posseme, N., E-mail: nicolas.posseme@cea.fr; Pollet, O.; Barnola, S.

2014-08-04

Silicon nitride spacer etching realization is considered today as one of the most challenging of the etch process for the new devices realization. For this step, the atomic etch precision to stop on silicon or silicon germanium with a perfect anisotropy (no foot formation) is required. The situation is that none of the current plasma technologies can meet all these requirements. To overcome these issues and meet the highly complex requirements imposed by device fabrication processes, we recently proposed an alternative etching process to the current plasma etch chemistries. This process is based on thin film modification by light ionsmore » implantation followed by a selective removal of the modified layer with respect to the non-modified material. In this Letter, we demonstrate the benefit of this alternative etch method in term of film damage control (silicon germanium recess obtained is less than 6 A), anisotropy (no foot formation), and its compatibility with other integration steps like epitaxial. The etch mechanisms of this approach are also addressed.« less

Hydrogen passivation of polycrystalline silicon thin films

NASA Astrophysics Data System (ADS)

Scheller, L.-P.; Weizman, M.; Simon, P.; Fehr, M.; Nickel, N. H.

2012-09-01

The influence of post-hydrogenation on the electrical and optical properties of solid phase crystallized polycrystalline silicon (poly-Si) was examined. The passivation of grain-boundary defects was measured as a function of the passivation time. The silicon dangling-bond concentration decreases with increasing passivation time due to the formation of Si-H complexes. In addition, large H-stabilized platelet-like clusters are generated. The influence of H on the electrical properties was investigated using temperature dependent conductivity and Hall-effect measurements. For poly-Si on Corning glass, the dark conductivity decreases upon hydrogenation, while it increases when the samples are fabricated on silicon-nitride covered Borofloat glass. Hall-effect measurements reveal that for poly-Si on Corning glass the hole concentration and the mobility decrease upon post-hydrogenation, while a pronounced increase is observed for poly-Si on silicon-nitride covered Borofloat glass. This indicates the formation of localized states in the band gap, which is supported by sub band-gap absorption measurments. The results are discussed in terms of hydrogen-induced defect passivation and generation mechanisms.

FDTD modeling of anisotropic nonlinear optical phenomena in silicon waveguides.

PubMed

Dissanayake, Chethiya M; Premaratne, Malin; Rukhlenko, Ivan D; Agrawal, Govind P

2010-09-27

A deep insight into the inherent anisotropic optical properties of silicon is required to improve the performance of silicon-waveguide-based photonic devices. It may also lead to novel device concepts and substantially extend the capabilities of silicon photonics in the future. In this paper, for the first time to the best of our knowledge, we present a three-dimensional finite-difference time-domain (FDTD) method for modeling optical phenomena in silicon waveguides, which takes into account fully the anisotropy of the third-order electronic and Raman susceptibilities. We show that, under certain realistic conditions that prevent generation of the longitudinal optical field inside the waveguide, this model is considerably simplified and can be represented by a computationally efficient algorithm, suitable for numerical analysis of complex polarization effects. To demonstrate the versatility of our model, we study polarization dependence for several nonlinear effects, including self-phase modulation, cross-phase modulation, and stimulated Raman scattering. Our FDTD model provides a basis for a full-blown numerical simulator that is restricted neither by the single-mode assumption nor by the slowly varying envelope approximation.

Inelastic response of silicon to shock compression

DOE PAGES

Higginbotham, Andrew; Stubley, P. G.; Comley, A. J.; ...

2016-04-13

The elastic and inelastic response of [001] oriented silicon to laser compression has been a topic of considerable discussion for well over a decade, yet there has been little progress in understanding the basic behaviour of this apparently simple material. We present experimental x-ray diffraction data showing complex elastic strain profiles in laser compressed samples on nanosecond timescales. We also present molecular dynamics and elasticity code modelling which suggests that a pressure induced phase transition is the cause of the previously reported ‘anomalous’ elastic waves. Moreover, this interpretation allows for measurement of the kinetic timescales for transition. Lastly, this modelmore » is also discussed in the wider context of reported deformation of silicon to rapid compression in the literature.« less

Inelastic response of silicon to shock compression

PubMed Central

Higginbotham, A.; Stubley, P. G.; Comley, A. J.; Eggert, J. H.; Foster, J. M.; Kalantar, D. H.; McGonegle, D.; Patel, S.; Peacock, L. J.; Rothman, S. D.; Smith, R. F.; Suggit, M. J.; Wark, J. S.

2016-01-01

The elastic and inelastic response of [001] oriented silicon to laser compression has been a topic of considerable discussion for well over a decade, yet there has been little progress in understanding the basic behaviour of this apparently simple material. We present experimental x-ray diffraction data showing complex elastic strain profiles in laser compressed samples on nanosecond timescales. We also present molecular dynamics and elasticity code modelling which suggests that a pressure induced phase transition is the cause of the previously reported ‘anomalous’ elastic waves. Moreover, this interpretation allows for measurement of the kinetic timescales for transition. This model is also discussed in the wider context of reported deformation of silicon to rapid compression in the literature. PMID:27071341

Material limitations on the detection limit in refractometry.

PubMed

Skafte-Pedersen, Peder; Nunes, Pedro S; Xiao, Sanshui; Mortensen, Niels Asger

2009-01-01

We discuss the detection limit for refractometric sensors relying on high-Q optical cavities and show that the ultimate classical detection limit is given by min {Δn} ≳ η, with n + iη being the complex refractive index of the material under refractometric investigation. Taking finite Q factors and filling fractions into account, the detection limit declines. As an example we discuss the fundamental limits of silicon-based high-Q resonators, such as photonic crystal resonators, for sensing in a bio-liquid environment, such as a water buffer. In the transparency window (λ ≳ 1100 nm) of silicon the detection limit becomes almost independent on the filling fraction, while in the visible, the detection limit depends strongly on the filling fraction because the silicon absorbs strongly.

David Adler Lectureship Award Talk: III-V Semiconductor Nanowires on Silicon for Future Devices

NASA Astrophysics Data System (ADS)

Riel, Heike

Bottom-up grown nanowires are very attractive materials for direct integration of III-V semiconductors on silicon thus opening up new possibilities for the design and fabrication of nanoscale devices for electronic, optoelectronic as well as quantum information applications. Template-Assisted Selective Epitaxy (TASE) allows the well-defined and monolithic integration of complex III-V nanostructures and devices on silicon. Achieving atomically abrupt heterointerfaces, high crystal quality and control of dimension down to 1D nanowires enabled the demonstration of FETs and tunnel devices based on In(Ga)As and GaSb. Furthermore, the strong influence of strain on nanowires as well as results on quantum transport studies of InAs nanowires with well-defined geometry will be presented.

Curvilinear electronics formed using silicon membrane circuits and elastomeric transfer elements.

PubMed

Ko, Heung Cho; Shin, Gunchul; Wang, Shuodao; Stoykovich, Mark P; Lee, Jeong Won; Kim, Dong-Hun; Ha, Jeong Sook; Huang, Yonggang; Hwang, Keh-Chih; Rogers, John A

2009-12-01

Materials and methods to achieve electronics intimately integrated on the surfaces of substrates with complex, curvilinear shapes are described. The approach exploits silicon membranes in circuit mesh structures that can be deformed in controlled ways using thin, elastomeric films. Experimental and theoretical studies of the micromechanics of such curvilinear electronics demonstrate the underlying concepts. Electrical measurements illustrate the high yields that can be obtained. The results represent significant experimental and theoretical advances over recently reported concepts for creating hemispherical photodetectors in electronic eye cameras and for using printable silicon nanoribbons/membranes in flexible electronics. The results might provide practical routes to the integration of high performance electronics with biological tissues and other systems of interest for new applications.

Enhancement of the release of azelaic acid through the synthetic membranes by inclusion complex formation with hydroxypropyl-beta-cyclodextrin.

PubMed

Manosroi, Jiradej; Apriyani, Maria Goretti; Foe, Kuncoro; Manosroi, Aranya

2005-04-11

The aim of this study was to investigate the release rates of azelaic acid and azelaic acid-hydroxypropyl-beta-cyclodextrin (HPbetaCD) inclusion complex through three types of synthetic membranes, namely cellophane, silicone and elastomer membranes. Solid inclusion complexes of azelaic acid-HPbetaCD at the molar ratio of 1:1 were prepared by coevaporation and freeze-drying methods, subsequently characterized by differential scanning calorimetry, X-ray diffractometry and dissolution studies. Solid inclusion complex obtained by coevaporation method which exhibited the inclusion of azelaic acid in the HPbetaCD cavity and gave the highest dissolution rate of azelaic acid was selected for the release study. Release studies of azelaic acid and this complex through the synthetic membranes were conducted using vertical Franz diffusion cells at 30 degrees C for 6 days. The release rates of azelaic acid through the synthetic membranes were enhanced by the formation of inclusion complex with HPbetaCD at the molar ratio of 1:1, with the increasing fluxes of about 41, 81 and 28 times of the uncomplexed system in cellophane, silicone and elastomer membranes, respectively. The result from this study can be applied for the development of azelaic acid for topical use.

Review of the Potential of the Ni/Cu Plating Technique for Crystalline Silicon Solar Cells

PubMed Central

Rehman, Atteq ur; Lee, Soo Hong

2014-01-01

Developing a better method for the metallization of silicon solar cells is integral part of realizing superior efficiency. Currently, contact realization using screen printing is the leading technology in the silicon based photovoltaic industry, as it is simple and fast. However, the problem with metallization of this kind is that it has a lower aspect ratio and higher contact resistance, which limits solar cell efficiency. The mounting cost of silver pastes and decreasing silicon wafer thicknesses encourages silicon solar cell manufacturers to develop fresh metallization techniques involving a lower quantity of silver usage and not relying pressing process of screen printing. In recent times nickel/copper (Ni/Cu) based metal plating has emerged as a metallization method that may solve these issues. This paper offers a detailed review and understanding of a Ni/Cu based plating technique for silicon solar cells. The formation of a Ni seed layer by adopting various deposition techniques and a Cu conducting layer using a light induced plating (LIP) process are appraised. Unlike screen-printed metallization, a step involving patterning is crucial for opening the masking layer. Consequently, experimental procedures involving patterning methods are also explicated. Lastly, the issues of adhesion, back ground plating, process complexity and reliability for industrial applications are also addressed. PMID:28788516

Method for Forming Fiber Reinforced Composite Bodies with Graded Composition and Stress Zones

NASA Technical Reports Server (NTRS)

Singh, Mrityunjay (Inventor); Levine, Stanley R. (Inventor); Smialek, James A. (Inventor)

1999-01-01

A near-net, complex shaped ceramic fiber reinforced silicon carbide based composite bodies with graded compositions and stress zones is disclosed. To provide the composite a fiber preform is first fabricated and an interphase is applied by chemical vapor infiltration, sol-gel or polymer processes. This first body is further infiltrated with a polymer mixture containing carbon, and/or silicon carbide, and additional oxide, carbide, or nitride phases forming a second body. One side of the second body is spray coated or infiltrated with slurries containing high thermal expansion and oxidation resistant. crack sealant phases and the other side of this second body is coated with low expansion phase materials to form a third body. This third body consisting of porous carbonaceous matrix surrounding the previously applied interphase materials, is then infiltrated with molten silicon or molten silicon-refractory metal alloys to form a fourth body. The resulting fourth body comprises dense composites consisting of fibers with the desired interphase which are surrounded by silicon carbide and other second phases materials at the outer and inner surfaces comprising material of silicon, germanium, refractory metal suicides, borides, carbides, oxides, and combinations thereof The resulting composite fourth body has different compositional patterns from one side to the other.

Review of the Potential of the Ni/Cu Plating Technique for Crystalline Silicon Solar Cells.

PubMed

Rehman, Atteq Ur; Lee, Soo Hong

2014-02-18

Developing a better method for the metallization of silicon solar cells is integral part of realizing superior efficiency. Currently, contact realization using screen printing is the leading technology in the silicon based photovoltaic industry, as it is simple and fast. However, the problem with metallization of this kind is that it has a lower aspect ratio and higher contact resistance, which limits solar cell efficiency. The mounting cost of silver pastes and decreasing silicon wafer thicknesses encourages silicon solar cell manufacturers to develop fresh metallization techniques involving a lower quantity of silver usage and not relying pressing process of screen printing. In recent times nickel/copper (Ni/Cu) based metal plating has emerged as a metallization method that may solve these issues. This paper offers a detailed review and understanding of a Ni/Cu based plating technique for silicon solar cells. The formation of a Ni seed layer by adopting various deposition techniques and a Cu conducting layer using a light induced plating (LIP) process are appraised. Unlike screen-printed metallization, a step involving patterning is crucial for opening the masking layer. Consequently, experimental procedures involving patterning methods are also explicated. Lastly, the issues of adhesion, back ground plating, process complexity and reliability for industrial applications are also addressed.

Efficacy and tolerance of a new silicone stent for the treatment of benign tracheal stenosis: preliminary results.

PubMed

Vergnon, J M; Costes, F; Polio, J C

2000-08-01

In inoperable patients with tracheal stenosis who are treated using silicone stents, stent migration occurs in 18.6% of cases. To decrease the migration rate, we have designed a new silicone stent with narrow central and larger distal parts. This study analyzes the stability and tolerance of this new stent. Preliminary prospective study conducted in two French university hospitals. Thirteen inoperable patients with benign complex tracheal stenosis due to intubation or tracheotomy. Tracheal stent insertion was performed under general anesthesia with a rigid bronchoscope. The patients were followed up clinically up to stent removal, which was planned at 18 months. Stent insertion or removal was very simple and did not differ from other silicone stents. No migration occurred after a mean follow-up of 22.8 months. Minimal granuloma formation occurred in only one patient (7.7%). Sputum retention remained similar to that with other silicone stents and could be improved by a smoother internal wall. Stents have been removed in seven patients after a mean duration of 19.6 months, with a complete stenosis cure in four cases. This new stent combines the excellent stability of the metallic stents and the tolerance and easy removal of straight silicone stents. This allows a prolonged use in order to obtain curative action.

Effect of electron injection on defect reactions in irradiated silicon containing boron, carbon, and oxygen

NASA Astrophysics Data System (ADS)

Makarenko, L. F.; Lastovskii, S. B.; Yakushevich, H. S.; Moll, M.; Pintilie, I.

2018-04-01

Comparative studies employing Deep Level Transient Spectroscopy and C-V measurements have been performed on recombination-enhanced reactions between defects of interstitial type in boron doped silicon diodes irradiated with alpha-particles. It has been shown that self-interstitial related defects which are immobile even at room temperatures can be activated by very low forward currents at liquid nitrogen temperatures. Their activation is accompanied by the appearance of interstitial carbon atoms. It has been found that at rather high forward current densities which enhance BiOi complex disappearance, a retardation of Ci annealing takes place. Contrary to conventional thermal annealing of the interstitial boron-interstitial oxygen complex, the use of forward current injection helps to recover an essential part of charge carriers removed due to irradiation.

Rigid bronchoscopy and silicone stents in the management of central airway obstruction

PubMed Central

Yarmus, Lonny

2015-01-01

The field of interventional pulmonology has grown significantly over the past several decades now including the diagnosis and therapeutic treatment of complex airway disease. Rigid bronchoscopy is an invaluable tool in the diagnosis and management of several malignant and non-malignant causes of central airway obstruction (CAO) and has become integral after the inception of airway stenting. The management of CAO can be a complicated endeavor with significant risks making the understanding of basic rigid bronchoscopy techniques, ablative technologies, anesthetic care and stenting of utmost importance in the care of these complex patients. This review article will focus on the history of rigid bronchoscopy, the technical aspects of performing a rigid bronchoscopy as well as the use of silicone stents their indications, complications and placement techniques. PMID:26807283

Dielectric and transport properties of thin films precipitated from sols with silicon nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kononov, N. N., E-mail: nnk@kapella.gpi.ru; Dorofeev, S. G.; Ishchenko, A. A.

2011-08-15

Dielectric properties of thin films precipitated on solid substrates from colloidal solutions containing silicon nanoparticles (average diameter is 10 nm) are studied by optical ellipsometry and impedance-spectroscopy. In the optical region, the values of real {epsilon} Prime and imaginary {epsilon} Double-Prime components of the complex permittivity {epsilon} vary within 2.1-1.1 and 0.25-0.75, respectively. These values are significantly lower than those of crystalline silicon. Using numerical simulation within the Bruggeman effective medium approximation, we show that the experimental {epsilon} Prime and {epsilon} Double-Prime spectra can be explained with good accuracy, assuming that the silicon film is a porous medium consisting ofmore » silicon monoxide (SiO) and air voids at a void ratio of 0.5. Such behavior of films is mainly caused by the effect of outer shells of silicon nanoparticles interacting with atmospheric oxygen on their dielectric properties. In the frequency range of 10-10{sup 6} Hz, the experimentally measured {epsilon} Prime and {epsilon} Double-Prime spectra of thin nanoscale silicon films are well approximated by the semi-empirical Cole-Cole dielectric dispersion law with the term related to free electric charges. The experimentally determined power-law frequency dependence of the ac conductivity means that the electrical transport in films is controlled by electric charge hopping through localized states in the unordered medium of outer shells of silicon nanoparticles composing films. It is found that the film conductivity at frequencies of {<=}2 Multiplication-Sign 10{sup 2} Hz is controlled by proton transport through Si-OH groups on the silicon nanoparticle surface.« less

Simulations of defect spin qubits in piezoelectric semiconductors

NASA Astrophysics Data System (ADS)

Seo, Hosung

In recent years, remarkable advances have been reported in the development of defect spin qubits in semiconductors for solid-state quantum information science and quantum metrology. Promising spin qubits include the nitrogen-vacancy center in diamond, dopants in silicon, and the silicon vacancy and divacancy spins in silicon carbide. In this talk, I will highlight some of our recent efforts devoted to defect spin qubits in piezoelectric wide-gap semiconductors for potential applications in mechanical hybrid quantum systems. In particular, I will describe our recent combined theoretical and experimental study on remarkably robust quantum coherence found in the divancancy qubits in silicon carbide. We used a quantum bath model combined with a cluster expansion method to identify the microscopic mechanisms behind the unusually long coherence times of the divacancy spins in SiC. Our study indicates that developing spin qubits in complex crystals with multiple types of atom is a promising route to realize strongly coherent hybrid quantum systems. I will also discuss progress and challenges in computational design of new spin defects for use as qubits in piezoelectric crystals such as AlN and SiC, including a new defect design concept using large metal ion - vacancy complexes. Our first principles calculations include DFT computations using recently developed self-consistent hybrid density functional theory and large-scale many-body GW theory. This work was supported by the National Science Foundation (NSF) through the University of Chicago MRSEC under Award Number DMR-1420709.

Hardware-Software Complex for Measurement of Energy and Angular Distributions of Charged Particles Formed in Nuclear Reactions

NASA Astrophysics Data System (ADS)

Vikhlyantsev, O. P.; Generalov, L. N.; Kuryakin, A. V.; Karpov, I. A.; Gurin, N. E.; Tumkin, A. D.; Fil'chagin, S. V.

2017-12-01

A hardware-software complex for measurement of energy and angular distributions of charged particles formed in nuclear reactions is presented. Hardware and software structures of the complex, the basic set of the modular nuclear-physical apparatus of a multichannel detecting system on the basis of Δ E- E telescopes of silicon detectors, and the hardware of experimental data collection, storage, and processing are presented and described.

Novel silicon microchannels device for use in red blood cell deformability studies

NASA Astrophysics Data System (ADS)

Zheng, Xiao-Lin; Liao, Yan-Jian; Zhang, Wen-Xian

2001-10-01

Currently, a number of techniques are used to access cell deformability. We study a novel silicon microchannels device for use in red blood cell deformability. The channels are produced in silicon substrate using microengineering technology. The microgrooves formed in the surface of a single-crystal silicon substrate. They were converted to channels by tightly covering them with an optical flat glass plate. An array of flow channels (number 950 in parallel) have typical dimensions of 5 micrometers width X 5.5 Xm depth, and 30 micrometers length. There the RBC's are forced to pass through channels. Thus, the microchannels are used to simulate human blood capillaries. It provides a specific measurement of individual cell in terms of both flow velocity profile and an index of cell volume while the cell flow through the channels. It dominates the complex cellular flow behavior, such as, the viscosity of whole blood is a nonlinear function of shear rate, index of filtration, etc.

Silicon nitride ceramic development in Thales Alenia Space : qualification achievement and further developments for future applications

NASA Astrophysics Data System (ADS)

Cornillon, L.; Devilliers, C.; Behar-Lafenetre, S.; Ait-Zaid, S.; Berroth, K.; Bravo, A. C.

2017-11-01

Dealing with ceramic materials for more than two decades, Thales Alenia Space - France has identified Silicon Nitride Si3N4 as a high potential material for the manufacturing of stiff, stable and lightweight truss structure for future large telescopes. Indeed, for earth observation or astronomic observation, space mission requires more and more telescopes with high spatial resolution, which leads to the use of large primary mirrors, and a long distance between primary and secondary mirrors. Therefore current and future large space telescopes require a huge truss structure to hold and locate precisely the mirrors. Such large structure requires very strong materials with high specific stiffness and a low coefficient of thermal expansion (CTE). Based on the silicon nitride performances and on the know how of FCT Ingenieurkeramik to manufacture complex parts, Thales Alenia Space (TAS) has engaged, in cooperation with FCT, activities to develop and qualify silicon nitride parts for other applications for space projects.

Silicon nitride ceramic development in Thales Alenia Space: qualification achiement and further developments for future applications

NASA Astrophysics Data System (ADS)

Cornillon, L.; Devilliers, C.; Behar-Lafenetre, S.; Ait-Zaid, S.; Berroth, K.; Bravo, A. C.

2017-11-01

Dealing with ceramic materials for more than two decades, Thales Alenia Space - France has identified Silicon Nitride Si3N4 as a high potential material for the manufacturing of stiff, stable and lightweight truss structure for future large telescopes. Indeed, for earth observation or astronomic observation, space mission requires more and more telescopes with high spatial resolution, which leads to the use of large primary mirrors, and a long distance between primary and secondary mirrors. Therefore current and future large space telescopes require a huge truss structure to hold and locate precisely the mirrors. Such large structure requires very strong materials with high specific stiffness and a low coefficient of thermal expansion (CTE). Based on the silicon nitride performances and on the know how of FCT Ingenieurkeramik to manufacture complex parts, Thales Alenia Space (TAS) has engaged, in cooperation with FCT, activities to develop and qualify silicon nitride parts for other applications for space projects.

Quantum interference in heterogeneous superconducting-photonic circuits on a silicon chip

PubMed Central

Schuck, C.; Guo, X.; Fan, L.; Ma, X.; Poot, M.; Tang, H. X.

2016-01-01

Quantum information processing holds great promise for communicating and computing data efficiently. However, scaling current photonic implementation approaches to larger system size remains an outstanding challenge for realizing disruptive quantum technology. Two main ingredients of quantum information processors are quantum interference and single-photon detectors. Here we develop a hybrid superconducting-photonic circuit system to show how these elements can be combined in a scalable fashion on a silicon chip. We demonstrate the suitability of this approach for integrated quantum optics by interfering and detecting photon pairs directly on the chip with waveguide-coupled single-photon detectors. Using a directional coupler implemented with silicon nitride nanophotonic waveguides, we observe 97% interference visibility when measuring photon statistics with two monolithically integrated superconducting single-photon detectors. The photonic circuit and detector fabrication processes are compatible with standard semiconductor thin-film technology, making it possible to implement more complex and larger scale quantum photonic circuits on silicon chips. PMID:26792424

Facile synthesis and characterization of silver nanoparticle/bis(o-phenolpropyl)silicone composites using a gold catalyst.

PubMed

Roh, Sung-Hee; Cheong, Hyeonsook; Kim, Do-Heyoung; Woo, Hee-Gweon; Lee, Byeong-Gweon; Yang, Kap-Seung; Kim, Bo-Hye; Sohn, Honglae

2013-01-01

The generation of silver nanoparticle/bis(o-phenolpropyl)silicone composites have been facilitated by the addition of sodium tetrachloroaurate or gold(Ill) chloride (< 1 wt% of NaAuCl4 or AuCl3) to the reaction of silver nitrate (AgNO3) with bis(o-phenolpropyl)silicone [BPPS, (o-phenolpropyl)2(SiMe2O)n, n = 2,3,8,236]. TEM and FE-SEM data showed that the silver nanoparticles having the size of < 20 nm are well dispersed throughout the BPPS silicone matrix in the composites. XRD patterns are consistent with those for polycrystalline silver. The size of silver nanoparticles augmented with increasing the relative molar concentration of AgNO3 added with respect to BPPS. The addition of gold complexes (1-3 wt%) did not affect the size distribution of silver nanoparticles appreciably. In the absence of BPPS, the macroscopic precipitation of silver by agglomeration, indicating that BPPS is necessary to stabilize the silver nanoparticles surrounded by coordination.

A computational workflow for designing silicon donor qubits

DOE PAGES

Humble, Travis S.; Ericson, M. Nance; Jakowski, Jacek; ...

2016-09-19

Developing devices that can reliably and accurately demonstrate the principles of superposition and entanglement is an on-going challenge for the quantum computing community. Modeling and simulation offer attractive means of testing early device designs and establishing expectations for operational performance. However, the complex integrated material systems required by quantum device designs are not captured by any single existing computational modeling method. We examine the development and analysis of a multi-staged computational workflow that can be used to design and characterize silicon donor qubit systems with modeling and simulation. Our approach integrates quantum chemistry calculations with electrostatic field solvers to performmore » detailed simulations of a phosphorus dopant in silicon. We show how atomistic details can be synthesized into an operational model for the logical gates that define quantum computation in this particular technology. In conclusion, the resulting computational workflow realizes a design tool for silicon donor qubits that can help verify and validate current and near-term experimental devices.« less

A review of molecular beam epitaxy of ferroelectric BaTiO 3 films on Si, Ge and GaAs substrates and their applications

DOE PAGES

Mazet, Lucie; Yang, Sang Mo; Kalinin, Sergei V.; ...

2015-06-30

SrTiO 3 epitaxial growth by molecular beam epitaxy (MBE) on silicon has opened up the route to the monolithic integration of various complex oxides on the complementary metal-oxide-semiconductor silicon platform. Among functional oxides, ferroelectric perovskite oxides offer promising perspectives to improve or add functionalities on-chip. We review the growth by MBE of the ferroelectric compound BaTiO 3 on silicon (Si), germanium (Ge) and gallium arsenide (GaAs) and we discuss the film properties in terms of crystalline structure, microstructure and ferroelectricity. Lastly, we review the last developments in two areas of interest for the applications of BaTiO 3 films on silicon,more » namely integrated photonics, which benefits from the large Pockels effect of BaTiO 3, and low power logic devices, which may benefit from the negative capacitance of the ferroelectric.« less

Micromachined silicon acoustic delay line with 3D-printed micro linkers and tapered input for improved structural stability and acoustic directivity

NASA Astrophysics Data System (ADS)

Cho, Y.; Kumar, A.; Xu, S.; Zou, J.

2016-10-01

Recent studies have shown that micromachined silicon acoustic delay lines can provide a promising solution to achieve real-time photoacoustic tomography without the need for complex transducer arrays and data acquisition electronics. To achieve deeper imaging depth and wider field of view, a longer delay time and therefore delay length are required. However, as the length of the delay line increases, it becomes more vulnerable to structural instability due to reduced mechanical stiffness. In this paper, we report the design, fabrication, and testing of a new silicon acoustic delay line enhanced with 3D printed polymer micro linker structures. First, mechanical deformation of the silicon acoustic delay line (with and without linker structures) under gravity was simulated by using finite element method. Second, the acoustic crosstalk and acoustic attenuation caused by the polymer micro linker structures were evaluated with both numerical simulation and ultrasound transmission testing. The result shows that the use of the polymer micro linker structures significantly improves the structural stability of the silicon acoustic delay lines without creating additional acoustic attenuation and crosstalk. In addition, the improvement of the acoustic acceptance angle of the silicon acoustic delay lines was also investigated to better suppress the reception of unwanted ultrasound signals outside of the imaging plane. These two improvements are expected to provide an effective solution to eliminate current limitations on the achievable acoustic delay time and out-of-plane imaging resolution of micromachined silicon acoustic delay line arrays.

Optimization of operating parameters in polysilicon chemical vapor deposition reactor with response surface methodology

NASA Astrophysics Data System (ADS)

An, Li-sha; Liu, Chun-jiao; Liu, Ying-wen

2018-05-01

In the polysilicon chemical vapor deposition reactor, the operating parameters are complex to affect the polysilicon's output. Therefore, it is very important to address the coupling problem of multiple parameters and solve the optimization in a computationally efficient manner. Here, we adopted Response Surface Methodology (RSM) to analyze the complex coupling effects of different operating parameters on silicon deposition rate (R) and further achieve effective optimization of the silicon CVD system. Based on finite numerical experiments, an accurate RSM regression model is obtained and applied to predict the R with different operating parameters, including temperature (T), pressure (P), inlet velocity (V), and inlet mole fraction of H2 (M). The analysis of variance is conducted to describe the rationality of regression model and examine the statistical significance of each factor. Consequently, the optimum combination of operating parameters for the silicon CVD reactor is: T = 1400 K, P = 3.82 atm, V = 3.41 m/s, M = 0.91. The validation tests and optimum solution show that the results are in good agreement with those from CFD model and the deviations of the predicted values are less than 4.19%. This work provides a theoretical guidance to operate the polysilicon CVD process.

Are Nonadiabatic Reaction Dynamics the Key to Novel Organosilicon Molecules? The Silicon (Si(3P))-Dimethylacetylene (C4H6(X1A1g)) System as a Case Study.

PubMed

Thomas, Aaron M; Dangi, Beni B; Yang, Tao; Kaiser, Ralf I; Lin, Lin; Chou, Tzu-Jung; Chang, Agnes H H

2018-06-06

The bimolecular gas phase reaction of ground-state silicon (Si; 3 P) with dimethylacetylene (C 4 H 6 ; X 1 A 1g ) was investigated under single collision conditions in a crossed molecular beams machine. Merged with electronic structure calculations, the data propose nonadiabatic reaction dynamics leading to the formation of singlet SiC 4 H 4 isomer(s) and molecular hydrogen (H 2 ) via indirect scattering dynamics along with intersystem crossing (ISC) from the triplet to the singlet surface. The reaction may lead to distinct energetically accessible singlet SiC 4 H 4 isomers ( 1 p8- 1 p24) in overall exoergic reaction(s) (-107 -20 +12 kJ mol -1 ). All feasible reaction products are either cyclic, carry carbene analogous silylene moieties, or carry C-Si-H or C-Si-C bonds that would require extensive isomerization from the initial collision complex(es) to the fragmenting singlet intermediate(s). The present study demonstrates the first successful crossed beams study of an exoergic reaction channel arising from bimolecular collisions of silicon, Si( 3 P), with a hydrocarbon molecule.

Mathematical model of silicon smelting process basing on pelletized charge from technogenic raw materials

NASA Astrophysics Data System (ADS)

Nemchinova, N. V.; Tyutrin, A. A.; Salov, V. M.

2018-03-01

The silicon production process in the electric arc reduction furnaces (EAF) is studied using pelletized charge as an additive to the standard on the basis of the generated mathematical model. The results obtained due to the model will contribute to the analysis of the charge components behavior during melting with the achievement of optimum final parameters of the silicon production process. The authors proposed using technogenic waste as a raw material for the silicon production in a pelletized form using liquid glass and aluminum production dust from the electrostatic precipitators as a binder. The method of mathematical modeling with the help of the ‘Selector’ software package was used as a basis for the theoretical study. A model was simulated with the imitation of four furnace temperature zones and a crystalline silicon phase (25 °C). The main advantage of the created model is the ability to analyze the behavior of all burden materials (including pelletized charge) in the carbothermic process. The behavior analysis is based on the thermodynamic probability data of the burden materials interactions in the carbothermic process. The model accounts for 17 elements entering the furnace with raw materials, electrodes and air. The silicon melt, obtained by the modeling, contained 91.73 % wt. of the target product. The simulation results showed that in the use of the proposed combined charge, the recovery of silicon reached 69.248 %, which is in good agreement with practical data. The results of the crystalline silicon chemical composition modeling are compared with the real silicon samples of chemical analysis data, which showed the results of convergence. The efficiency of the mathematical modeling methods in the studying of the carbothermal silicon obtaining process with complex interphase transformations and the formation of numerous intermediate compounds using a pelletized charge as an additive to the traditional one is shown.

Stress and Strain in Silicon Electrode Models

DOE PAGES

Higa, Kenneth; Srinivasan, Venkat

2015-03-24

While the high capacity of silicon makes it an attractive negative electrode for Li-ion batteries, the associated large volume change results in fracture and capacity fade. Composite electrodes incorporating silicon have additional complexity, as active material is attached to surrounding material which must likewise experience significant volume change. In this paper, a finite-deformation model is used to explore, for the first time, mechanical interactions between a silicon particle undergoing lithium insertion, and attached binder material. Simulations employ an axisymmetric model system in which solutions vary in two spatial directions and shear stresses develop at interfaces between materials. The mechanical responsemore » of the amorphous active material is dependent on lithium concentration, and an equation of state incorporating reported volume expansion data is used. Simulations explore the influence of active material size and binder stiffness, and suggest delamination as an additional mode of material damage. Computed strain energies and von Mises equivalent stresses are in physically-relevant ranges, comparable to reported yield stresses and adhesion energies, and predicted trends are largely consistent with reported experimental results. It is hoped that insights from this work will support the design of more robust silicon composite electrodes.« less

Elasto-Capillary Folding Using Stop-Programmable Hinges Fabricated by 3D Micro-Machining

PubMed Central

Legrain, Antoine; Berenschot, Erwin J. W.; Tas, Niels R.; Abelmann, Leon

2015-01-01

We show elasto-capillary folding of silicon nitride objects with accurate folding angles between flaps of (70.6 ± 0.1)° and demonstrate the feasibility of such accurate micro-assembly with a final folding angle of 90°. The folding angle is defined by stop-programmable hinges that are fabricated starting from silicon molds employing accurate three-dimensional corner lithography. This nano-patterning method exploits the conformal deposition and the subsequent timed isotropic etching of a thin film in a 3D shaped silicon template. The technique leaves a residue of the thin film in sharp concave corners which can be used as an inversion mask in subsequent steps. Hinges designed to stop the folding at 70.6° were fabricated batchwise by machining the V-grooves obtained by KOH etching in (110) silicon wafers; 90° stop-programmable hinges were obtained starting from silicon molds obtained by dry etching on (100) wafers. The presented technique has potential to achieve any folding angle and opens a new route towards creating structures with increased complexity, which will ultimately lead to a novel method for device fabrication. PMID:25992886

Resonant silicon nanoparticles for enhancement of light absorption and photoluminescence from hybrid perovskite films and metasurfaces.

PubMed

Tiguntseva, E; Chebykin, A; Ishteev, A; Haroldson, R; Balachandran, B; Ushakova, E; Komissarenko, F; Wang, H; Milichko, V; Tsypkin, A; Zuev, D; Hu, W; Makarov, S; Zakhidov, A

2017-08-31

Recently, hybrid halide perovskites have emerged as one of the most promising types of materials for thin-film photovoltaic and light-emitting devices because of their low-cost and potential for high efficiency. Further boosting their performance without detrimentally increasing the complexity of the architecture is critically important for commercialization. Despite a number of plasmonic nanoparticle based designs having been proposed for solar cell improvement, inherent optical losses of the nanoparticles reduce photoluminescence from perovskites. Here we use low-loss high-refractive-index dielectric (silicon) nanoparticles for improving the optical properties of organo-metallic perovskite (MAPbI 3 ) films and metasurfaces to achieve strong enhancement of photoluminescence as well as useful light absorption. As a result, we observed experimentally a 50% enhancement of photoluminescence intensity from a perovskite layer with silicon nanoparticles and 200% enhancement for a nanoimprinted metasurface with silicon nanoparticles on top. Strong increase in light absorption is also demonstrated and described by theoretical calculations. Since both silicon nanoparticle fabrication/deposition and metasurface nanoimprinting techniques are low-cost, we believe that the developed all-dielectric approach paves the way to novel scalable and highly effective designs of perovskite based metadevices.

Affordable, Robust Ceramic Joining Technology (ARCJoinT) for High Temperature Applications

NASA Technical Reports Server (NTRS)

Singh, M.

1998-01-01

Ceramic joining is recognized as one of the enabling technologies for the successful utilization of silicon carbide-based monolithic ceramic and fiber reinforced composite components in a number of demanding and high temperature applications in aerospace and ground-based systems. An affordable, robust ceramic joining technology (ARCJoinT) for joining of silicon carbide-based ceramics and fiber reinforced composites has been developed. This technique is capable of producing joints with tailorable thickness and composition. A wide variety of silicon carbide-based ceramics and composites, in different shapes and sizes, have been joined using this technique. The room and high temperature mechanical properties and fractography of ceramic joints have been reported. In monolithic silicon carbide ceramics, these joints maintain their mechanical strength up to 1350 C in air. There is no change in the mechanical strength of joints in silicon carbide matrix composites up to 1200 C in air. In composites, simple butt joints yield only about 20% of the ultimate strength of the parent materials. This technology is suitable for the joining of large and complex shaped ceramic and composite components, and with certain modifications, can be applied to repair of ceramic components damaged in service.

Parameter Estimation of a Spiking Silicon Neuron

PubMed Central

Russell, Alexander; Mazurek, Kevin; Mihalaş, Stefan; Niebur, Ernst; Etienne-Cummings, Ralph

2012-01-01

Spiking neuron models are used in a multitude of tasks ranging from understanding neural behavior at its most basic level to neuroprosthetics. Parameter estimation of a single neuron model, such that the model’s output matches that of a biological neuron is an extremely important task. Hand tuning of parameters to obtain such behaviors is a difficult and time consuming process. This is further complicated when the neuron is instantiated in silicon (an attractive medium in which to implement these models) as fabrication imperfections make the task of parameter configuration more complex. In this paper we show two methods to automate the configuration of a silicon (hardware) neuron’s parameters. First, we show how a Maximum Likelihood method can be applied to a leaky integrate and fire silicon neuron with spike induced currents to fit the neuron’s output to desired spike times. We then show how a distance based method which approximates the negative log likelihood of the lognormal distribution can also be used to tune the neuron’s parameters. We conclude that the distance based method is better suited for parameter configuration of silicon neurons due to its superior optimization speed. PMID:23852978

Polymer taper bridge for silicon waveguide to single mode waveguide coupling

NASA Astrophysics Data System (ADS)

Kruse, Kevin; Middlebrook, Christopher T.

2016-03-01

Coupling of optical power from high-density silicon waveguides to silica optical fibers for signal routing can incur high losses and often requires complex end-face preparation/processing. Novel coupling device taper structures are proposed for low coupling loss between silicon photonic waveguides and single mode fibers are proposed and devices are fabricated and measured in terms of performance. Theoretical mode conversion models for waveguide tapers are derived for optimal device structure design and performance. Commercially viable vertical and multi-layer taper designs using polymer waveguide materials are proposed as innovative, cost-efficient, and mass-manufacturable optical coupling devices. The coupling efficiency for both designs is determined to evaluate optimal device dimensions and alignment tolerances with both silicon rib waveguides and silicon nanowire waveguides. Propagation loss as a function of waveguide roughness and metallic loss are determined and correlated to waveguide dimensions to obtain total insertion loss for the proposed taper designs. Multi-layer tapers on gold-sputtered substrates are fabricated through photolithography as proof-of-concept devices and evaluated for device loss optimization. Tapered waveguide coupling loss with Si WGs (2.74 dB) was experimentally measured with high correlation to theoretical results.

An evaluation of a silicone adhesive shaped heel dressing.

PubMed

Hampton, Sylvie

Tissue breakdown is complex and involves many factors. Pressure ulcer development in the heels is subject to extrinsic factors such as pressure, shear, friction and moisture. The heels are the most common sites for friction and shear damage, which can lead to blistering, skin erosion and tissue breakdown (Grey et al, 2006). To address the issues of wounds that are painful on dressing removal and friable skin, Smith & Nephew has introduced a soft silicone adhesive dressing to its Allevyn dressing range. Silicone does not adhere to wounded areas and can be removed gently without trauma to the periwound area. This paper discusses the findings of a 20-patient multi-site evaluation examining the performance and acceptability of Allevyn Gentle Border Heel dressing in the management of heel wounds.

Fabrication and single-electron-transfer operation of a triple-dot single-electron transistor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jo, Mingyu, E-mail: mingyujo@eis.hokudai.ac.jp; Uchida, Takafumi; Tsurumaki-Fukuchi, Atsushi

2015-12-07

A triple-dot single-electron transistor was fabricated on silicon-on-insulator wafer using pattern-dependent oxidation. A specially designed one-dimensional silicon wire having small constrictions at both ends was converted to a triple-dot single-electron transistor by means of pattern-dependent oxidation. The fabrication of the center dot involved quantum size effects and stress-induced band gap reduction, whereas that of the two side dots involved thickness modulation because of the complex edge structure of two-dimensional silicon. Single-electron turnstile operation was confirmed at 8 K when a 100-mV, 1-MHz square wave was applied. Monte Carlo simulations indicated that such a device with inhomogeneous tunnel and gate capacitances canmore » exhibit single-electron transfer.« less

Novel axially carborane-cage substituted silicon phthalocyanine photosensitizer; synthesis, characterization and photophysicochemical properties

NASA Astrophysics Data System (ADS)

Atmaca, Göknur Yaşa; Dizman, Cemil; Eren, Tarık; Erdoğmuş, Ali

2015-02-01

The novel axially dicarborane substituted silicon (IV) (SiPc-DC) phthalocyanine was synthesized by treating silicon phthalocyanine dichloride SiPc(Cl)2 (SiPc) with o-Carborane monool. The compound was characterized by mass spectrometry, UV-Vis, FT-IR, 1H and 11B Nuclear Magnetic Resonance Spectroscopy (NMR). Spectral, photophysical (fluorescence quantum yield) and photochemical (singlet oxygen (ΦΔ) and photodegradation quantum yield (Φd)) properties of the complex were reported in different solutions (Dimethyl sulfoxide (DMSO), Dimethylformamide (DMF) and Toluene). The results of spectral measurements showed that both SiPc and carborane cage can have potential to be used as sensitizers in photodynamic therapy (PDT) and boron neutron capture therapy (BNCT) by their singlet oxygen efficiencies (ΦΔ = 0.41, 0.39).

Material Limitations on the Detection Limit in Refractometry

PubMed Central

Skafte-Pedersen, Peder; Nunes, Pedro S.; Xiao, Sanshui; Mortensen, Niels Asger

2009-01-01

We discuss the detection limit for refractometric sensors relying on high-Q optical cavities and show that the ultimate classical detection limit is given by min {Δn} ≳ η, with n + iη being the complex refractive index of the material under refractometric investigation. Taking finite Q factors and filling fractions into account, the detection limit declines. As an example we discuss the fundamental limits of silicon-based high-Q resonators, such as photonic crystal resonators, for sensing in a bio-liquid environment, such as a water buffer. In the transparency window (λ ≳ 1100 nm) of silicon the detection limit becomes almost independent on the filling fraction, while in the visible, the detection limit depends strongly on the filling fraction because the silicon absorbs strongly. PMID:22291513

Electrical properties of binary mixtures of amino silicone oil and methyl iso butyl ketone

NASA Astrophysics Data System (ADS)

Shah, K. N.; Rana, V. A.; Vankar, H. P.

2018-05-01

The real and imaginary parts of the dielectric function of the binary mixtures of the methyl iso butyl ketone and amino silicone oil in the frequency range 100 Hz to 2 MHz were measured using precision LCR meter at 305.15 K. The electrical properties such as electrical modulus M*(ω), electrical conductivity σ*(ω) and complex impedance Z*(ω) were calculated using the dielectric function ɛ*(ω). The ionic polarization relaxation time (Τσ) and D.C. conductivity (σdc) were also calculated using electrical properties. The ionic behavior of methyl iso butyl ketone and non-ionic behavior of amino silicone oil are also explained. The electrical parameters are used to gain information about the effect of concentration variation of components of the mixtures on the electrical properties.

Affordable, Robust Ceramic Joining Technology (ARCJoinT) Given 1999 R and D 100 Award

NASA Technical Reports Server (NTRS)

Singh, Mrityunjay

2000-01-01

Advanced ceramics and fiber-reinforced ceramic matrix composites with high strength and toughness, good thermal conductivity, thermal shock resistance, and oxidation resistance are needed for high-temperature structural applications in advanced high-efficiency and high-performance engines, space propulsion components, and land-based systems. The engineering designs of these systems require the manufacturing of large parts with complex shapes, which are either quite expensive or impossible to fabricate. In many instances, it is more economical to build complex shapes by joining together simple geometrical shapes. Thus, joining has been recognized as an enabling technology for the successful utilization of advanced ceramics and fiber-reinforced composite components in high-temperature applications. However, such joints must retain their structural integrity at high temperatures and must have mechanical strength and environmental stability comparable to those of the bulk materials. In addition, the joining technique should be robust, practical, and reliable. ARCJoinT, which is based on the reaction-forming approach, is unique in terms of producing joints with tailorable microstructures. The formation of joints by this approach is attractive since the thermomechanical properties of the joint interlayer can be tailored to be very close to those of the base materials. In addition, high-temperature fixturing is not needed to hold the parts at the infiltration temperature. The joining process begins with the application of a carbonaceous mixture in the joint area, holding the items to be joined in a fixture, and curing at 110 to 120 C for 10 to 20 min. This step fastens the pieces together. Then, silicon or a silicon alloy in tape, paste, or slurry form is applied around the joint region and heated to 1250 to 1425 C (depending on the type of infiltrant) for 10 to 15 min. The molten silicon or silicon-refractory metal alloy reacts with carbon to form silicon carbide with controllable amounts of silicon and other phases as determined by the alloy composition. Joint thickness can be readily controlled through adjustments of the properties of the carbonaceous paste and the applied fixturing force. The photograph shows various shapes of silicon-carbide-based ceramics and fiberreinforced composites that have been joined using ARCJoinT. Thermomechanical and thermochemical characterization of joints is underway for a wide variety of silicon-carbidebased advanced ceramics and fiber-reinforced composites under the hostile environments that will be encountered in engine applications. ARCJoinT, which was developed by researchers at the NASA Glenn Research Center at Lewis Field, received R&D Magazine's prestigious R&D 100 Award in 1999.

Nanostructured gold and platinum electrodes on silicon structures for biosensing

NASA Astrophysics Data System (ADS)

Ogurtsov, V. I.; Sheehan, M. M.

2005-01-01

Gold and platinum metal electrodes on Si/SiO2 having undergone anisotropic potassium hydroxide (KOH) etch treatment are considered. This treatment etches at different rates and directions in the material resulting in creation of numerous pyramid shaped holes in the silicon substrate. This surface is used to make metal electrodes with increased electrode efficiency. The electrodes can serve as the sensors or as the sensor substrates (for surface polymer modification) and because both gold and platinum are inert they have applications for food safety biosensing. Wine, an economically significant food product, was chosen as a matrix, and impedance spectroscopy (EIS) was selected as a method of investigation of electrode behaviour. Based on results of EIS, different complexity equivalent circuits were determined by applying fitting mean square root optimisation of sensor complex impedance measurements.

Improved silicon carbide for advanced heat engines

NASA Technical Reports Server (NTRS)

Whalen, Thomas J.

1987-01-01

This is the second annual technical report entitled, Improved Silicon Carbide for Advanced Heat Engines, and includes work performed during the period February 16, 1986 to February 15, 1987. The program is conducted for NASA under contract NAS3-24384. The objective is the development of high strength, high reliability silicon carbide parts with complex shapes suitable for use in advanced heat engines. The fabrication methods used are to be adaptable for mass production of such parts on an economically sound basis. Injection molding is the forming method selected. This objective is to be accomplished in a two-phase program: (1) to achieve a 20 percent improvement in strength and a 100 percent increase in Weibull modulus of the baseline material; and (2) to produce a complex shaped part, a gas turbine rotor, for example, with the improved mechanical properties attained in the first phase. Eight tasks are included in the first phase covering the characterization of the properties of a baseline material, the improvement of those properties and the fabrication of complex shaped parts. Activities during the first contract year concentrated on two of these areas: fabrication and characterization of the baseline material (Task 1) and improvement of material and processes (Task 7). Activities during the second contract year included an MOR bar matrix study to improve mechanical properties (Task 2), materials and process improvements (Task 7), and a Ford-funded task to mold a turbocharger rotor with an improved material (Task 8).

Investigation of model-based physical design restrictions (Invited Paper)

NASA Astrophysics Data System (ADS)

Lucas, Kevin; Baron, Stanislas; Belledent, Jerome; Boone, Robert; Borjon, Amandine; Couderc, Christophe; Patterson, Kyle; Riviere-Cazaux, Lionel; Rody, Yves; Sundermann, Frank; Toublan, Olivier; Trouiller, Yorick; Urbani, Jean-Christophe; Wimmer, Karl

2005-05-01

As lithography and other patterning processes become more complex and more non-linear with each generation, the task of physical design rules necessarily increases in complexity also. The goal of the physical design rules is to define the boundary between the physical layout structures which will yield well from those which will not. This is essentially a rule-based pre-silicon guarantee of layout correctness. However the rapid increase in design rule requirement complexity has created logistical problems for both the design and process functions. Therefore, similar to the semiconductor industry's transition from rule-based to model-based optical proximity correction (OPC) due to increased patterning complexity, opportunities for improving physical design restrictions by implementing model-based physical design methods are evident. In this paper we analyze the possible need and applications for model-based physical design restrictions (MBPDR). We first analyze the traditional design rule evolution, development and usage methodologies for semiconductor manufacturers. Next we discuss examples of specific design rule challenges requiring new solution methods in the patterning regime of low K1 lithography and highly complex RET. We then evaluate possible working strategies for MBPDR in the process development and product design flows, including examples of recent model-based pre-silicon verification techniques. Finally we summarize with a proposed flow and key considerations for MBPDR implementation.

Lanthanide luminescence enhancements in porous silicon resonant microcavities.

PubMed

Jenie, S N Aisyiyah; Pace, Stephanie; Sciacca, Beniamino; Brooks, Robert D; Plush, Sally E; Voelcker, Nicolas H

2014-08-13

In this paper, the covalent immobilization and luminescence enhancement of a europium (Eu(III)) complex in a porous silicon (pSi) layer with a microcavity (pSiMC) structure are demonstrated. The alkyne-pendant arm of the Eu(III) complex was covalently immobilized on the azide-modified surface via ligand-assisted "click" chemistry. The design parameters of the microcavity were optimized to obtain an efficient luminescence-enhancing device. Luminescence enhancements by a factor of 9.5 and 3.0 were observed for Eu(III) complex bound inside the pSiMC as compared to a single layer and Bragg reflector of identical thickness, respectively, confirming the increased interaction between the immobilized molecules and the electric field in the spacer of the microcavity. When comparing pSiMCs with different resonance wavelength position, luminescence was enhanced when the resonance wavelength overlapped with the maximum emission wavelength of the Eu(III) complex at 614 nm, allowing for effective coupling between the confined light and the emitting molecules. The pSiMC also improved the spectral color purity of the Eu(III) complex luminescence. The ability of a pSiMC to act as an efficient Eu(III) luminescence enhancer, combined with the resulting sharp linelike emission, can be exploited for the development of ultrasensitive optical biosensors.

Origin of reverse annealing in radiation-damaged silicon solar cells

NASA Technical Reports Server (NTRS)

Weinberg, I.; Swartz, C. K.

1980-01-01

The paper employs relative defect concentrations, energy levels, capture cross sections, and minority carrier diffusion lengths in order to identify the defect responsible for the reverse annealing observed in a radiation damaged n(+)/p silicon solar cell. It is reported that the responsible defect, with the energy level at +0.30 eV, has been tentatively identified as boron-oxygen-vacancy complex. In conclusion, it is shown that removal of this defect could result in significant cell recovery when annealing at temperatures well below the currently required 400 C.

Radiation damage annealing mechanisms and possible low temperature annealing in silicon solar cells

NASA Technical Reports Server (NTRS)

Weinberg, I.; Swartz, C. K.

1980-01-01

Deep level transient spectroscopy and the Shockley-Read-Hall recombination theory are used to identify the defect responsible for reverse annealing in 2 ohm-cm n+/p silicon solar cells. This defect, with energy level at Ev + 0.30 eV, has been tentatively identified as a boron-oxygen-vacancy complex. It has been also determined by calculation that the removal of this defect could result in significant annealing at temperatures as low as 200 C for 2 ohm-cm and lower resistivity cells.

Back-junction back-contact n-type silicon solar cell with diffused boron emitter locally blocked by implanted phosphorus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Müller, Ralph, E-mail: ralph.mueller@ise.fraunhofer.de; Schrof, Julian; Reichel, Christian

2014-09-08

The highest energy conversion efficiencies in the field of silicon-based photovoltaics have been achieved with back-junction back-contact (BJBC) silicon solar cells by several companies and research groups. One of the most complex parts of this cell structure is the fabrication of the locally doped p- and n-type regions, both on the back side of the solar cell. In this work, we introduce a process sequence based on a synergistic use of ion implantation and furnace diffusion. This sequence enables the formation of all doped regions for a BJBC silicon solar cell in only three processing steps. We observed that implantedmore » phosphorus can block the diffusion of boron atoms into the silicon substrate by nearly three orders of magnitude. Thus, locally implanted phosphorus can be used as an in-situ mask for a subsequent boron diffusion which simultaneously anneals the implanted phosphorus and forms the boron emitter. BJBC silicon solar cells produced with such an easy-to-fabricate process achieved conversion efficiencies of up to 21.7%. An open-circuit voltage of 674 mV and a fill factor of 80.6% prove that there is no significant recombination at the sharp transition between the highly doped emitter and the highly doped back surface field at the device level.« less

Dynamics and diffusion mechanism of low-density liquid silicon

DOE PAGES

Shen, B.; Wang, Z. Y.; Dong, F.; ...

2015-11-05

A first-order phase transition from a high-density liquid to a low-density liquid has been proposed to explain the various thermodynamic anomies of water. It also has been proposed that such liquid–liquid phase transition would exist in supercooled silicon. Computer simulation studies show that, across the transition, the diffusivity drops roughly 2 orders of magnitude, and the structures exhibit considerable tetrahedral ordering. The resulting phase is a highly viscous, low-density liquid silicon. Investigations on the atomic diffusion of such a novel form of liquid silicon are of high interest. Here we report such diffusion results from molecular dynamics simulations using themore » classical Stillinger–Weber (SW) potential of silicon. We show that the atomic diffusion of the low-density liquid is highly correlated with local tetrahedral geometries. We also show that atoms diffuse through hopping processes within short ranges, which gradually accumulate to an overall random motion for long ranges as in normal liquids. There is a close relationship between dynamical heterogeneity and hopping process. We point out that the above diffusion mechanism is closely related to the strong directional bonding nature of the distorted tetrahedral network. Here, our work offers new insights into the complex behavior of the highly viscous low density liquid silicon, suggesting similar diffusion behaviors in other tetrahedral coordinated liquids that exhibit liquid–liquid phase transition such as carbon and germanium.« less

Pathways to exotic metastable silicon allotropes

DOE PAGES

Haberl, Bianca; Strobel, Timothy A.; Bradby, Jodie E.

2016-09-27

The Group 14 element silicon possesses a complex free-energy landscape with many (local) minima, allowing for the formation of a variety of unusual structures, some of which may be stabilized at ambient conditions. Such exotic silicon allotropes represent a significant opportunity to address the ever-increasing demand for novel materials with tailored functionality since these exotic forms are expected to exhibit superlative properties including optimized band gaps for solar power conversion. The application of pressure is a well-recognized and uniquely powerful method to access exotic states of silicon since it promotes large changes to atomic bonding. Conventional high-pressure syntheses, however, lackmore » the capability to access many of these local minima and only four forms of exotic silicon allotropes have been recovered over the last 50 years. However, more recently, signifi- cant advances in high pressure methodologies and the use of novel precursor materials have yielded at least three more recoverable exotic Si structures. This review aims to give an overview of these innovative methods of high-pressure application and precursor selection and the recent discoveries of new Si allotropes. The background context of the conventional pressure methods and multitude of predicted new phases are also provided. Furthermore, this review also offers a perspective for possible access to many further exotic functional allotropes not only of silicon but also of other materials, in a technologically feasible manner« less

Silicon nitride equation of state

NASA Astrophysics Data System (ADS)

Brown, Robert C.; Swaminathan, Pazhayannur K.

2017-01-01

This report presents the development of a global, multi-phase equation of state (EOS) for the ceramic silicon nitride (Si3N4).1 Structural forms include amorphous silicon nitride normally used as a thin film and three crystalline polymorphs. Crystalline phases include hexagonal α-Si3N4, hexagonal β-Si3N4, and the cubic spinel c-Si3N4. Decomposition at about 1900 °C results in a liquid silicon phase and gas phase products such as molecular nitrogen, atomic nitrogen, and atomic silicon. The silicon nitride EOS was developed using EOSPro which is a new and extended version of the PANDA II code. Both codes are valuable tools and have been used successfully for a variety of material classes. Both PANDA II and EOSPro can generate a tabular EOS that can be used in conjunction with hydrocodes. The paper describes the development efforts for the component solid phases and presents results obtained using the EOSPro phase transition model to investigate the solid-solid phase transitions in relation to the available shock data that have indicated a complex and slow time dependent phase change to the c-Si3N4 phase. Furthermore, the EOSPro mixture model is used to develop a model for the decomposition products; however, the need for a kinetic approach is suggested to combine with the single component solid models to simulate and further investigate the global phase coexistences.

Abnormal carbene-silicon halide complexes.

PubMed

Wang, Yuzhong; Xie, Yaoming; Wei, Pingrong; Schaefer, Henry F; Robinson, Gregory H

2016-04-14

Reaction of the anionic N-heterocyclic dicarbene (NHDC), [:C{[N(2,6-Pr(i)2C6H3)]2CHCLi}]n (1), with SiCl4 gives the trichlorosilyl-substituted (at the C4 carbon) N-heterocyclic carbene complex (7). Abnormal carbene-SiCl4 complex (8) may be conveniently synthesized by combining 7 with HCl·NEt3. In addition, 7 may react with CH2Cl2 in warm hexane, giving the abnormal carbene-complexed SiCl3(+) cation (9). The nature of the bonding in 9 was probed with complementary DFT computations.

Potassium conductance dynamics confer robust spike-time precision in a neuromorphic model of the auditory brain stem

PubMed Central

Boahen, Kwabena

2013-01-01

A fundamental question in neuroscience is how neurons perform precise operations despite inherent variability. This question also applies to neuromorphic engineering, where low-power microchips emulate the brain using large populations of diverse silicon neurons. Biological neurons in the auditory pathway display precise spike timing, critical for sound localization and interpretation of complex waveforms such as speech, even though they are a heterogeneous population. Silicon neurons are also heterogeneous, due to a key design constraint in neuromorphic engineering: smaller transistors offer lower power consumption and more neurons per unit area of silicon, but also more variability between transistors and thus between silicon neurons. Utilizing this variability in a neuromorphic model of the auditory brain stem with 1,080 silicon neurons, we found that a low-voltage-activated potassium conductance (gKL) enables precise spike timing via two mechanisms: statically reducing the resting membrane time constant and dynamically suppressing late synaptic inputs. The relative contribution of these two mechanisms is unknown because blocking gKL in vitro eliminates dynamic adaptation but also lengthens the membrane time constant. We replaced gKL with a static leak in silico to recover the short membrane time constant and found that silicon neurons could mimic the spike-time precision of their biological counterparts, but only over a narrow range of stimulus intensities and biophysical parameters. The dynamics of gKL were required for precise spike timing robust to stimulus variation across a heterogeneous population of silicon neurons, thus explaining how neural and neuromorphic systems may perform precise operations despite inherent variability. PMID:23554436

A micromachined silicon parallel acoustic delay line (PADL) array for real-time photoacoustic tomography (PAT)

NASA Astrophysics Data System (ADS)

Cho, Young Y.; Chang, Cheng-Chung; Wang, Lihong V.; Zou, Jun

2015-03-01

To achieve real-time photoacoustic tomography (PAT), massive transducer arrays and data acquisition (DAQ) electronics are needed to receive the PA signals simultaneously, which results in complex and high-cost ultrasound receiver systems. To address this issue, we have developed a new PA data acquisition approach using acoustic time delay. Optical fibers were used as parallel acoustic delay lines (PADLs) to create different time delays in multiple channels of PA signals. This makes the PA signals reach a single-element transducer at different times. As a result, they can be properly received by single-channel DAQ electronics. However, due to their small diameter and fragility, using optical fiber as acoustic delay lines poses a number of challenges in the design, construction and packaging of the PADLs, thereby limiting their performances and use in real imaging applications. In this paper, we report the development of new silicon PADLs, which are directly made from silicon wafers using advanced micromachining technologies. The silicon PADLs have very low acoustic attenuation and distortion. A linear array of 16 silicon PADLs were assembled into a handheld package with one common input port and one common output port. To demonstrate its real-time PAT capability, the silicon PADL array (with its output port interfaced with a single-element transducer) was used to receive 16 channels of PA signals simultaneously from a tissue-mimicking optical phantom sample. The reconstructed PA image matches well with the imaging target. Therefore, the silicon PADL array can provide a 16× reduction in the ultrasound DAQ channels for real-time PAT.

Silicon-Germanium Films Grown on Sapphire for Ka-Band Communications Applications

NASA Technical Reports Server (NTRS)

Alterovitz, Samuel A.; Mueller, Carl H.; Croke, Edward T.

2004-01-01

NASA's vision in the space communications area is to develop a broadband data network in which there is a high degree of interconnectivity among the various satellite systems, ground stations, and wired systems. To accomplish this goal, we will need complex electronic circuits integrating analog and digital data handling at the Ka-band (26 to 40 GHz). The purpose of this project is to show the feasibility of a new technology for Ka-band communications applications, namely silicon germanium (SiGe) on sapphire. This new technology will have several advantages in comparison to the existing silicon-substrate- based circuits. The main advantages are extremely low parasitic reactances that enable much higher quality active and passive components, better device isolation, higher radiation tolerance, and the integration of digital and analog circuitry on a single chip.

Synthesis and Characterization of Antireflective ZnO Nanoparticles Coatings Used for Energy Improving Efficiency of Silicone Solar Cells

NASA Astrophysics Data System (ADS)

Pîslaru-Dănescu, Lucian; Chitanu, Elena; El-Leathey, Lucia-Andreea; Marinescu, Virgil; Marin, Dorian; Sbârcea, Beatrice-Gabriela

2018-05-01

The paper proposes a new and complex process for the synthesis of ZnO nanoparticles for antireflective coating corresponding to silicone solar cells applications. The process consists of two major steps: preparation of seed layer and hydrothermal growth of ZnO nanoparticles. Due to the fact that the seed layer morphology influences the ZnO nanoparticles proprieties, the process optimization of the seed layer preparation is necessary. Following the hydrothermal growth of the ZnO nanoparticles, antireflective coating of silicone solar cells is achieved. After determining the functional parameters of the solar cells provided either with glass or with ZnO, it is concluded that all the parameters values are superior in the case of solar cells with ZnO antireflection coating and are increasing along with the solar irradiance.

Decoration of silicon nanostructures with copper particles for simultaneous selective capture and mass spectrometry detection of His-tagged model peptide.

PubMed

Coffinier, Yannick; Kurylo, Ievgen; Drobecq, Hervé; Szunerits, Sabine; Melnyk, Oleg; Zaitsev, Vladimir N; Boukherroub, Rabah

2014-10-21

We present in this work a simple and fast preparation method of a new affinity surface-assisted laser/desorption ionization mass spectrometry (SALDI-MS) substrate based on silicon nanostructures decorated with copper particles. The silicon nanostructures were fabricated by the metal-assisted chemical etching (MACE) method. Then, superhydrophilic areas surrounded by superhydrophobic regions were formed through hydrosilylation reaction of 1-octadecene, followed by local degradation of the octadecyl layer. After that, copper particles were deposited in the hydrophilic areas by using the electroless method. We have demonstrated that these surfaces were able to perform high selective capture of model His-tag peptide even in a complex mixture such as serum solution. Then, the captured peptide was detected by mass spectrometry at a femtomolar level without the need of organic matrix.

Porous silicon and diatoms micro-shells: an example of inverse biomimetic

NASA Astrophysics Data System (ADS)

De Tommasi, Edoardo; Rea, Ilaria; Rendina, Ivo; De Stefano, Luca

2011-05-01

Porous silicon (PSi) is by far a very useful technological platform for optical monitoring of chemical and biological substances and due to its peculiar physical and morphological properties it is worldwide used in sensing experiments. On the other hand, we have discovered a natural material, the micro-shells of marine diatoms, ubiquitous unicellular algae, which are made of hydrated amorphous silica, but, most of all, show geometrical structures made of complex patterns of pores which are surprisingly similar to those of porous silicon. Moreover, under laser irradiation, this material is photoluminescent and the photoluminescence is very sensitive to the surrounding atmosphere, which means that the material can act as a transducer. Starting from our experience on PSi devices, we explore the optical and photonic properties of marine diatoms micro-shells in a sort of inverse biomimicry.

Integration of Electrodeposited Ni-Fe in MEMS with Low-Temperature Deposition and Etch Processes

PubMed Central

Schiavone, Giuseppe; Murray, Jeremy; Perry, Richard; Mount, Andrew R.; Desmulliez, Marc P. Y.; Walton, Anthony J.

2017-01-01

This article presents a set of low-temperature deposition and etching processes for the integration of electrochemically deposited Ni-Fe alloys in complex magnetic microelectromechanical systems, as Ni-Fe is known to suffer from detrimental stress development when subjected to excessive thermal loads. A selective etch process is reported which enables the copper seed layer used for electrodeposition to be removed while preserving the integrity of Ni-Fe. In addition, a low temperature deposition and surface micromachining process is presented in which silicon dioxide and silicon nitride are used, respectively, as sacrificial material and structural dielectric. The sacrificial layer can be patterned and removed by wet buffered oxide etch or vapour HF etching. The reported methods limit the thermal budget and minimise the stress development in Ni-Fe. This combination of techniques represents an advance towards the reliable integration of Ni-Fe components in complex surface micromachined magnetic MEMS. PMID:28772683

Light Trapping with Silicon Light Funnel Arrays

PubMed Central

Nissan, Yuval; Gabay, Tamir; Shalev, Gil

2018-01-01

Silicon light funnels are three-dimensional subwavelength structures in the shape of inverted cones with respect to the incoming illumination. Light funnel (LF) arrays can serve as efficient absorbing layers on account of their light trapping capabilities, which are associated with the presence of high-density complex Mie modes. Specifically, light funnel arrays exhibit broadband absorption enhancement of the solar spectrum. In the current study, we numerically explore the optical coupling between surface light funnel arrays and the underlying substrates. We show that the absorption in the LF array-substrate complex is higher than the absorption in LF arrays of the same height (~10% increase). This, we suggest, implies that a LF array serves as an efficient surface element that imparts additional momentum components to the impinging illumination, and hence optically excites the substrate by near-field light concentration, excitation of traveling guided modes in the substrate, and mode hybridization. PMID:29562685

A multichip aVLSI system emulating orientation selectivity of primary visual cortical cells.

PubMed

Shimonomura, Kazuhiro; Yagi, Tetsuya

2005-07-01

In this paper, we designed and fabricated a multichip neuromorphic analog very large scale integrated (aVLSI) system, which emulates the orientation selective response of the simple cell in the primary visual cortex. The system consists of a silicon retina and an orientation chip. An image, which is filtered by a concentric center-surround (CS) antagonistic receptive field of the silicon retina, is transferred to the orientation chip. The image transfer from the silicon retina to the orientation chip is carried out with analog signals. The orientation chip selectively aggregates multiple pixels of the silicon retina, mimicking the feedforward model proposed by Hubel and Wiesel. The chip provides the orientation-selective (OS) outputs which are tuned to 0 degrees, 60 degrees, and 120 degrees. The feed-forward aggregation reduces the fixed pattern noise that is due to the mismatch of the transistors in the orientation chip. The spatial properties of the orientation selective response were examined in terms of the adjustable parameters of the chip, i.e., the number of aggregated pixels and size of the receptive field of the silicon retina. The multichip aVLSI architecture used in the present study can be applied to implement higher order cells such as the complex cell of the primary visual cortex.

In-chip microstructures and photonic devices fabricated by nonlinear laser lithography deep inside silicon

PubMed Central

Makey, Ghaith; Elahi, Parviz; Çolakoğlu, Tahir; Ergeçen, Emre; Yavuz, Özgün; Hübner, René; Borra, Mona Zolfaghari; Pavlov, Ihor; Bek, Alpan; Turan, Raşit; Kesim, Denizhan Koray; Tozburun, Serhat; Ilday, Serim; Ilday, F. Ömer

2017-01-01

Silicon is an excellent material for microelectronics and integrated photonics1–3 with untapped potential for mid-IR optics4. Despite broad recognition of the importance of the third dimension5,6, current lithography methods do not allow fabrication of photonic devices and functional microelements directly inside silicon chips. Even relatively simple curved geometries cannot be realised with techniques like reactive ion etching. Embedded optical elements, like in glass7, electronic devices, and better electronic-photonic integration are lacking8. Here, we demonstrate laser-based fabrication of complex 3D structures deep inside silicon using 1 µm-sized dots and rod-like structures of adjustable length as basic building blocks. The laser-modified Si has a different optical index than unmodified parts, which enables numerous photonic devices. Optionally, these parts are chemically etched to produce desired 3D shapes. We exemplify a plethora of subsurface, i.e., “in-chip” microstructures for microfluidic cooling of chips, vias, MEMS, photovoltaic applications and photonic devices that match or surpass the corresponding state-of-the-art device performances. PMID:28983323

Ab initio study of point defects near stacking faults in 3C-SiC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xi, Jianqi; Liu, Bin; Zhang, Yanwen

Interactions between point defects and stacking faults in 3C-SiC are studied using an ab initio method based on density functional theory. The results show that the discontinuity of the stacking sequence considerably affects the configurations and behavior of intrinsic defects, especially in the case of silicon interstitials. The existence of an intrinsic stacking fault (missing a C-Si bilayer) shortens the distance between the tetrahedral-center site and its second-nearest-neighboring silicon layer, making the tetrahedral silicon interstitial unstable. Instead of a tetrahedral configuration with four C neighbors, a pyramid-like interstitial structure with a defect state within the band gap becomes a stablemore » configuration. In addition, orientation rotation occurs in the split interstitials that has diverse effects on the energy landscape of silicon and carbon split interstitials in the stacking fault region. Moreover, our analyses of ionic relaxation and electronic structure of vacancies show that the built-in strain field, owing to the existence of the stacking fault, makes the local environment around vacancies more complex than that in the bulk.« less

Ab initio study of point defects near stacking faults in 3C-SiC

DOE PAGES

Xi, Jianqi; Liu, Bin; Zhang, Yanwen; ...

2016-07-02

Interactions between point defects and stacking faults in 3C-SiC are studied using an ab initio method based on density functional theory. The results show that the discontinuity of the stacking sequence considerably affects the configurations and behavior of intrinsic defects, especially in the case of silicon interstitials. The existence of an intrinsic stacking fault (missing a C-Si bilayer) shortens the distance between the tetrahedral-center site and its second-nearest-neighboring silicon layer, making the tetrahedral silicon interstitial unstable. Instead of a tetrahedral configuration with four C neighbors, a pyramid-like interstitial structure with a defect state within the band gap becomes a stablemore » configuration. In addition, orientation rotation occurs in the split interstitials that has diverse effects on the energy landscape of silicon and carbon split interstitials in the stacking fault region. Moreover, our analyses of ionic relaxation and electronic structure of vacancies show that the built-in strain field, owing to the existence of the stacking fault, makes the local environment around vacancies more complex than that in the bulk.« less

In-chip microstructures and photonic devices fabricated by nonlinear laser lithography deep inside silicon

NASA Astrophysics Data System (ADS)

Tokel, Onur; Turnalı, Ahmet; Makey, Ghaith; Elahi, Parviz; ćolakoǧlu, Tahir; Ergeçen, Emre; Yavuz, Ã.-zgün; Hübner, René; Zolfaghari Borra, Mona; Pavlov, Ihor; Bek, Alpan; Turan, Raşit; Kesim, Denizhan Koray; Tozburun, Serhat; Ilday, Serim; Ilday, F. Ã.-mer

2017-10-01

Silicon is an excellent material for microelectronics and integrated photonics1-3, with untapped potential for mid-infrared optics4. Despite broad recognition of the importance of the third dimension5,6, current lithography methods do not allow the fabrication of photonic devices and functional microelements directly inside silicon chips. Even relatively simple curved geometries cannot be realized with techniques like reactive ion etching. Embedded optical elements7, electronic devices and better electronic-photonic integration are lacking8. Here, we demonstrate laser-based fabrication of complex 3D structures deep inside silicon using 1-µm-sized dots and rod-like structures of adjustable length as basic building blocks. The laser-modified Si has an optical index different to that in unmodified parts, enabling the creation of numerous photonic devices. Optionally, these parts can be chemically etched to produce desired 3D shapes. We exemplify a plethora of subsurface—that is, `in-chip'—microstructures for microfluidic cooling of chips, vias, micro-electro-mechanical systems, photovoltaic applications and photonic devices that match or surpass corresponding state-of-the-art device performances.

Spreading of Emulsions on Glass Substrates

NASA Astrophysics Data System (ADS)

Mohammad Karim, Alireza; Kavehpour, Pirouz

2012-11-01

The wettability of emulsions is an important factor with explicit influence in an extensive variety of industrial applications ranging from the petroleum to food industries. Surprisingly, there is no comprehensive study of emulsion spreading to date; this is due to the complexity of the structure of the emulsions and non-homogeneity of the dispersed phase bubbles in size as well as distribution through the emulsion. The spreading of water/silicone oil emulsions on glass substrates was investigated. The emulsions were prepared with varying volume fractions of water dispersed in silicone oil, with addition of small amounts of surfactant to stabilize the emulsion structure. The time dependent variation of dynamic contact angle, base diameter, and the spreading rate of the droplets of an emulsion are different from a pure substance. The effect of water/silicone oil weight percentage as well as the droplet size and dispersed phase bubble size were also investigated. The weight percentage of water/silicone oil emulsion and droplet size did not have significant influence on the spreading dynamics; however the dispersed phase drop size affected the spreading dynamics substantially.

Investigation of isochronal annealing on the optical properties of HWCVD amorphous silicon nitride deposited at low temperatures and low gas flow rates

NASA Astrophysics Data System (ADS)

Muller, T. F. G.; Jacobs, S.; Cummings, F. R.; Oliphant, C. J.; Malgas, G. F.; Arendse, C. J.

2015-06-01

Hydrogenated amorphous silicon nitride (a-SiNx:H) is used as anti-reflection coatings in commercial solar cells. A final firing step in the production of micro-crystalline silicon solar cells allows hydrogen effusion from the a-SiNx:H into the solar cell, and contributes to bulk passivation of the grain boundaries. In this study a-SiNx:H deposited in a hot-wire chemical vapour deposition (HWCVD) chamber with reduced gas flow rates and filament temperature compared to traditional deposition regimes, were annealed isochronally. The UV-visible reflection spectra of the annealed material were subjected to the Bruggeman Effective Medium Approximation (BEMA) treatment, in which a theoretical amorphous semiconductor was combined with particle inclusions due to the structural complexities of the material. The extraction of the optical functions and ensuing Wemple-DeDomenici analysis of the wavelength-dependent refractive index allowed for the correlation of the macroscopic optical properties with the changes in the local atomic bonding configuration, involving silicon, nitrogen and hydrogen.

Extremely flexible nanoscale ultrathin body silicon integrated circuits on plastic.

PubMed

Shahrjerdi, Davood; Bedell, Stephen W

2013-01-09

In recent years, flexible devices based on nanoscale materials and structures have begun to emerge, exploiting semiconductor nanowires, graphene, and carbon nanotubes. This is primarily to circumvent the existing shortcomings of the conventional flexible electronics based on organic and amorphous semiconductors. The aim of this new class of flexible nanoelectronics is to attain high-performance devices with increased packing density. However, highly integrated flexible circuits with nanoscale transistors have not yet been demonstrated. Here, we show nanoscale flexible circuits on 60 Å thick silicon, including functional ring oscillators and memory cells. The 100-stage ring oscillators exhibit the stage delay of ~16 ps at a power supply voltage of 0.9 V, the best reported for any flexible circuits to date. The mechanical flexibility is achieved by employing the controlled spalling technology, enabling the large-area transfer of the ultrathin body silicon devices to a plastic substrate at room temperature. These results provide a simple and cost-effective pathway to enable ultralight flexible nanoelectronics with unprecedented level of system complexity based on mainstream silicon technology.

Silicon photonics for high-performance interconnection networks

NASA Astrophysics Data System (ADS)

Biberman, Aleksandr

2011-12-01

We assert in the course of this work that silicon photonics has the potential to be a key disruptive technology in computing and communication industries. The enduring pursuit of performance gains in computing, combined with stringent power constraints, has fostered the ever-growing computational parallelism associated with chip multiprocessors, memory systems, high-performance computing systems, and data centers. Sustaining these parallelism growths introduces unique challenges for on- and off-chip communications, shifting the focus toward novel and fundamentally different communication approaches. This work showcases that chip-scale photonic interconnection networks, enabled by high-performance silicon photonic devices, enable unprecedented bandwidth scalability with reduced power consumption. We demonstrate that the silicon photonic platforms have already produced all the high-performance photonic devices required to realize these types of networks. Through extensive empirical characterization in much of this work, we demonstrate such feasibility of waveguides, modulators, switches, and photodetectors. We also demonstrate systems that simultaneously combine many functionalities to achieve more complex building blocks. Furthermore, we leverage the unique properties of available silicon photonic materials to create novel silicon photonic devices, subsystems, network topologies, and architectures to enable unprecedented performance of these photonic interconnection networks and computing systems. We show that the advantages of photonic interconnection networks extend far beyond the chip, offering advanced communication environments for memory systems, high-performance computing systems, and data centers. Furthermore, we explore the immense potential of all-optical functionalities implemented using parametric processing in the silicon platform, demonstrating unique methods that have the ability to revolutionize computation and communication. Silicon photonics enables new sets of opportunities that we can leverage for performance gains, as well as new sets of challenges that we must solve. Leveraging its inherent compatibility with standard fabrication techniques of the semiconductor industry, combined with its capability of dense integration with advanced microelectronics, silicon photonics also offers a clear path toward commercialization through low-cost mass-volume production. Combining empirical validations of feasibility, demonstrations of massive performance gains in large-scale systems, and the potential for commercial penetration of silicon photonics, the impact of this work will become evident in the many decades that follow.

A deep etching mechanism for trench-bridging silicon nanowires

NASA Astrophysics Data System (ADS)

Tasdemir, Zuhal; Wollschläger, Nicole; Österle, Werner; Leblebici, Yusuf; Erdem Alaca, B.

2016-03-01

Introducing a single silicon nanowire with a known orientation and dimensions to a specific layout location constitutes a major challenge. The challenge becomes even more formidable, if one chooses to realize the task in a monolithic fashion with an extreme topography, a characteristic of microsystems. The need for such a monolithic integration is fueled by the recent surge in the use of silicon nanowires as functional building blocks in various electromechanical and optoelectronic applications. This challenge is addressed in this work by introducing a top-down, silicon-on-insulator technology. The technology provides a pathway for obtaining well-controlled silicon nanowires along with the surrounding microscale features up to a three-order-of-magnitude scale difference. A two-step etching process is developed, where the first shallow etch defines a nanoscale protrusion on the wafer surface. After applying a conformal protection on the protrusion, a deep etch step is carried out forming the surrounding microscale features. A minimum nanowire cross-section of 35 nm by 168 nm is demonstrated in the presence of an etch depth of 10 μm. Nanowire cross-sectional features are characterized via transmission electron microscopy and linked to specific process steps. The technology allows control on all dimensional aspects along with the exact location and orientation of the silicon nanowire. The adoption of the technology in the fabrication of micro and nanosystems can potentially lead to a significant reduction in process complexity by facilitating direct access to the nanowire during surface processes such as contact formation and doping.

Optimizing photon-pair generation electronically using a p-i-n diode incorporated in a silicon microring resonator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Savanier, Marc, E-mail: msavanier@eng.ucsd.edu; Kumar, Ranjeet; Mookherjea, Shayan, E-mail: smookherjea@eng.ucsd.edu

Silicon photonic microchips may be useful for compact, inexpensive, room-temperature optically pumped photon-pair sources, which unlike conventional photon-pair generators based on crystals or optical fibers, can be manufactured using CMOS-compatible processes on silicon wafers. It has been shown that photon pairs can be created in simple structures such as microring resonators at a rate of a few hundred kilohertz using less than a milliwatt of optical pump power, based on the process of spontaneous four-wave mixing. To create a practical photon-pair source, however, also requires some way of monitoring the device and aligning the pump wavelength when the temperature varies,more » since silicon resonators are highly sensitive to temperature. In fact, monitoring photodiodes are standard components in classical laser diodes, but the incorporation of germanium or InGaAs photodiodes would raise the cost and fabrication complexity. Here, we present a simple and effective all-electronic technique for finding the optimum operating point for the microring used to generate photon pairs, based on measuring the reverse-biased current in a silicon p-i-n junction diode fabricated across the waveguide that constitutes the silicon microring. We show that by monitoring the current, and using it to tune the pump laser wavelength, the photon-pair generation properties of the microring can be preserved over a temperature range of more than 30 °C.« less

Silicon photonics: some remaining challenges

NASA Astrophysics Data System (ADS)

Reed, G. T.; Topley, R.; Khokhar, A. Z.; Thompson, D. J.; Stanković, S.; Reynolds, S.; Chen, X.; Soper, N.; Mitchell, C. J.; Hu, Y.; Shen, L.; Martinez-Jimenez, G.; Healy, N.; Mailis, S.; Peacock, A. C.; Nedeljkovic, M.; Gardes, F. Y.; Soler Penades, J.; Alonso-Ramos, C.; Ortega-Monux, A.; Wanguemert-Perez, G.; Molina-Fernandez, I.; Cheben, P.; Mashanovich, G. Z.

2016-03-01

This paper discusses some of the remaining challenges for silicon photonics, and how we at Southampton University have approached some of them. Despite phenomenal advances in the field of Silicon Photonics, there are a number of areas that still require development. For short to medium reach applications, there is a need to improve the power consumption of photonic circuits such that inter-chip, and perhaps intra-chip applications are viable. This means that yet smaller devices are required as well as thermally stable devices, and multiple wavelength channels. In turn this demands smaller, more efficient modulators, athermal circuits, and improved wavelength division multiplexers. The debate continues as to whether on-chip lasers are necessary for all applications, but an efficient low cost laser would benefit many applications. Multi-layer photonics offers the possibility of increasing the complexity and effectiveness of a given area of chip real estate, but it is a demanding challenge. Low cost packaging (in particular, passive alignment of fibre to waveguide), and effective wafer scale testing strategies, are also essential for mass market applications. Whilst solutions to these challenges would enhance most applications, a derivative technology is emerging, that of Mid Infra-Red (MIR) silicon photonics. This field will build on existing developments, but will require key enhancements to facilitate functionality at longer wavelengths. In common with mainstream silicon photonics, significant developments have been made, but there is still much left to do. Here we summarise some of our recent work towards wafer scale testing, passive alignment, multiplexing, and MIR silicon photonics technology.

A deep etching mechanism for trench-bridging silicon nanowires.

PubMed

Tasdemir, Zuhal; Wollschläger, Nicole; Österle, Werner; Leblebici, Yusuf; Alaca, B Erdem

2016-03-04

Introducing a single silicon nanowire with a known orientation and dimensions to a specific layout location constitutes a major challenge. The challenge becomes even more formidable, if one chooses to realize the task in a monolithic fashion with an extreme topography, a characteristic of microsystems. The need for such a monolithic integration is fueled by the recent surge in the use of silicon nanowires as functional building blocks in various electromechanical and optoelectronic applications. This challenge is addressed in this work by introducing a top-down, silicon-on-insulator technology. The technology provides a pathway for obtaining well-controlled silicon nanowires along with the surrounding microscale features up to a three-order-of-magnitude scale difference. A two-step etching process is developed, where the first shallow etch defines a nanoscale protrusion on the wafer surface. After applying a conformal protection on the protrusion, a deep etch step is carried out forming the surrounding microscale features. A minimum nanowire cross-section of 35 nm by 168 nm is demonstrated in the presence of an etch depth of 10 μm. Nanowire cross-sectional features are characterized via transmission electron microscopy and linked to specific process steps. The technology allows control on all dimensional aspects along with the exact location and orientation of the silicon nanowire. The adoption of the technology in the fabrication of micro and nanosystems can potentially lead to a significant reduction in process complexity by facilitating direct access to the nanowire during surface processes such as contact formation and doping.

Micromachined silicon acoustic delay line with improved structural stability and acoustic directivity for real-time photoacoustic tomography

NASA Astrophysics Data System (ADS)

Cho, Young; Kumar, Akhil; Xu, Song; Zou, Jun

2017-03-01

Recent studies have shown that micromachined silicon acoustic delay lines can provide a promising solution to achieve real-time photoacoustic tomography without the need for complex transducer arrays and data acquisition electronics. However, as its length increases to provide longer delay time, the delay line becomes more vulnerable to structural instability due to reduced mechanical stiffness. In addition, the small cross-section area of the delay line results in a large acoustic acceptance angle and therefore poor directivity. To address these two issues, this paper reports the design, fabrication, and testing of a new silicon acoustic delay line enhanced with 3D printed polymer micro linker structures. First, mechanical deformation of the silicon acoustic delay line (with and without linker structures) under gravity was simulated by using finite element method. Second, the acoustic crosstalk and acoustic attenuation caused by the polymer micro linker structures were evaluated with both numerical simulation and ultrasound transmission testing. The result shows that the use of the polymer micro linker structures significantly improves the structural stability of the silicon acoustic delay lines without creating additional acoustic attenuation and crosstalk. In addition, a new tapered design for the input terminal of the delay line was also investigate to improve its acoustic directivity by reducing the acoustic acceptance angle. These two improvements are expected to provide an effective solution to eliminate current limitations on the achievable acoustic delay time and out-of-plane imaging resolution of micromachined silicon acoustic delay line arrays.

Deployment Testing of Flexible Composite Hinges in Bi-Material Beams

NASA Technical Reports Server (NTRS)

Sauder, Jonathan F.; Trease, Brian

2016-01-01

Composites have excellent properties for strength, thermal stability, and weight. However, they are traditionally highly rigid, and when used in deployable structures require hinges bonded to the composite material, which increases complexity and opportunities for failure. Recent research in composites has found by adding an elastomeric soft matrix, often silicone instead of an epoxy, the composite becomes flexible. This work explores the deployment repeatability of silicone matrix composite hinges which join rigid composite beams. The hinges were found to have sub-millimeter deployment repeatability. Also, an interesting creep effect was discovered, that a hinges deployment error would decrease with time.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yanhong; Gao, Ping; Bi, Kaifeng

Conducting pathway of percolation network was identified in resistive switching devices (RSDs) with the structure of silver/amorphous silicon/p-type silicon (Ag/a-Si/p-Si) based on its gradual RESET-process and the stochastic complex impedance spectroscopy characteristics (CIS). The formation of the percolation network is attributed to amounts of nanocrystalline Si particles as well as defect sites embedded in a-Si layer, in which the defect sites supply positions for Ag ions to nucleate and grow. The similar percolation network has been only observed in Ag-Ge-Se based RSD before. This report provides a better understanding for electric properties of RSD based on the percolation network.

Analysis of silicon on insulator (SOI) optical microring add-drop filter based on waveguide intersections

NASA Astrophysics Data System (ADS)

Kaźmierczak, Andrzej; Bogaerts, Wim; Van Thourhout, Dries; Drouard, Emmanuel; Rojo-Romeo, Pedro; Giannone, Domenico; Gaffiot, Frederic

2008-04-01

We present a compact passive optical add-drop filter which incorporates two microring resonators and a waveguide intersection in silicon-on-insulator (SOI) technology. Such a filter is a key element for designing simple layouts of highly integrated complex optical networks-on-chip. The filter occupies an area smaller than 10μm×10μm and exhibits relatively high quality factors (up to 4000) and efficient signal dropping capabilities. In the present work, the influence of filter parameters such as the microring-resonators radii and the coupling section shape are analyzed theoretically and experimentally

Is there a shadow biosphere of silicon utilizing organisms on earth?

NASA Astrophysics Data System (ADS)

Das, P.; Das, S.

2012-12-01

The idea of shadow biosphere was first visualized by Carol Cleland and Shelley Copley of the University of Colorado in 2005. Since that time many scientists were interested in this subject and the basis of this paper is also correlated with this novel idea. A shadow biosphere essentially consists of self replicating bodies utilizing one or more chemicals which are not exploited to such extent by organisms of the real biosphere. Silicon-utilizing organisms mainly belong to the diatoms, some other algae, sponges, monocotyledon plants in this category are classified by us. They can survive in extremes of temperature, pressure, radiation, pH, salinity and nutrient conditions and this unusual tolerance to stress depends on their silicon biomineralization occurring either as a biologically controlled process or as a biologically induced process. In the control process silicate is sequestered and transferred to the intracellular silica deposition vesicle by energy driven pump mechanism in presence of specific transporter protein. In induced silicon mineralization, initial amorphous nucleation of silicon is gradually transformed to a crystalline phase. Besides these two methods, there are also other processes in which formation of silanol and siloxane can occur from oligomers of silica originating from monomers by Hydrogen bonding, cation bridging and direct electrostatic interactions. The structure of the silica biomineralised cell wall in silicon utilizing organisms is very complex, but this may explain their ability to stress tolerance and their possible coordinating role with other essential bioactive elements in nature. When electropositive elements are less, then polymerization of silicon-oxygen excess may occur easily, particularly in carbon and nitrogen paucity in the environment. Thus all these features indicate possibility of a shadow biosphere of these organisms on earth.

GaAs VLSI technology and circuit elements for DSP

NASA Astrophysics Data System (ADS)

Mikkelson, James M.

1990-10-01

Recent progress in digital GaAs circuit performance and complexity is presented to demonstrate the current capabilities of GaAs components. High density GaAs process technology and circuit design techniques are described and critical issues for achieving favorable complexity speed power and cost tradeoffs are reviewed. Some DSP building blocks are described to provide examples of what types of DSP systems could be implemented with present GaAs technology. DIGITAL GaAs CIRCUIT CAPABILITIES In the past few years the capabilities of digital GaAs circuits have dramatically increased to the VLSI level. Major gains in circuit complexity and power-delay products have been achieved by the use of silicon-like process technologies and simple circuit topologies. The very high speed and low power consumption of digital GaAs VLSI circuits have made GaAs a desirable alternative to high performance silicon in hardware intensive high speed system applications. An example of the performance and integration complexity available with GaAs VLSI circuits is the 64x64 crosspoint switch shown in figure 1. This switch which is the most complex GaAs circuit currently available is designed on a 30 gate GaAs gate array. It operates at 200 MHz and dissipates only 8 watts of power. The reasons for increasing the level of integration of GaAs circuits are similar to the reasons for the continued increase of silicon circuit complexity. The market factors driving GaAs VLSI are system design methodology system cost power and reliability. System designers are hesitant or unwilling to go backwards to previous design techniques and lower levels of integration. A more highly integrated system in a lower performance technology can often approach the performance of a system in a higher performance technology at a lower level of integration. Higher levels of integration also lower the system component count which reduces the system cost size and power consumption while improving the system reliability. For large gate count circuits the power per gate must be minimized to prevent reliability and cooling problems. The technical factors which favor increasing GaAs circuit complexity are primarily related to reducing the speed and power penalties incurred when crossing chip boundaries. Because the internal GaAs chip logic levels are not compatible with standard silicon I/O levels input receivers and output drivers are needed to convert levels. These I/O circuits add significant delay to logic paths consume large amounts of power and use an appreciable portion of the die area. The effects of these I/O penalties can be reduced by increasing the ratio of core logic to I/O on a chip. DSP operations which have a large number of logic stages between the input and the output are ideal candidates to take advantage of the performance of GaAs digital circuits. Figure 2 is a schematic representation of the I/O penalties encountered when converting from ECL levels to GaAs

Light localization and SERS in tip-shaped silicon metasurface.

PubMed

Lagarkov, Andrey; Boginskaya, Irina; Bykov, Igor; Budashov, Igor; Ivanov, Andrey; Kurochkin, Ilya; Ryzhikov, Ilya; Rodionov, Ilya; Sedova, Marina; Zverev, Alexander; Sarychev, Andrey K

2017-07-24

Optical properties of two dimensional periodic system of the silicon micro-cones are investigated. The metasurface, composed of the silicon tips, shows enhancement of the local optical field. Finite element computer simulations as well as real experiment reveal anomalous optical response of the dielectric metasurface due to excitation of the dielectric resonances. Various electromagnetic resonances are considered in the dielectric cone. The metal-dielectric resonances, which are excited between metal nanoparticles and dielectric cones, are also considered. The resonance local electric field can be much larger than the field in the usual surface plasmon resonances. To investigate local electric field the signal molecules are deposited on the metal nanoparticles. We demonstrate enhancement of the electromagnetic field and Raman signal from the complex of DTNB acid molecules and gold nanoparticles, which are distributed over the metasurface. The metasurfaces composed from the dielectric resonators can have quasi-continuous spectrum and serve as an efficient SERS substrates.

Model-based correction for local stress-induced overlay errors

NASA Astrophysics Data System (ADS)

Stobert, Ian; Krishnamurthy, Subramanian; Shi, Hongbo; Stiffler, Scott

2018-03-01

Manufacturing embedded DRAM deep trench capacitors can involve etching very deep holes into silicon wafers1. Due to various design constraints, these holes may not be uniformly distributed across the wafer surface. Some wafer processing steps for these trenches results in stress effects which can distort the silicon wafer in a manner that creates localized alignment issues between the trenches and the structures built above them on the wafer. In this paper, we describe a method to model these localized silicon distortions for complex layouts involving billions of deep trench structures. We describe wafer metrology techniques and data which have been used to verify the stress distortion model accuracy. We also provide a description of how this kind of model can be used to manipulate the polygons in the mask tape out flow to compensate for predicted localized misalignments between design shapes from a deep trench mask and subsequent masks.

Wafer scale formation of monocrystalline silicon-based Mie resonators via silicon-on-insulator dewetting.

PubMed

Abbarchi, Marco; Naffouti, Meher; Vial, Benjamin; Benkouider, Abdelmalek; Lermusiaux, Laurent; Favre, Luc; Ronda, Antoine; Bidault, Sébastien; Berbezier, Isabelle; Bonod, Nicolas

2014-11-25

Subwavelength-sized dielectric Mie resonators have recently emerged as a promising photonic platform, as they combine the advantages of dielectric microstructures and metallic nanoparticles supporting surface plasmon polaritons. Here, we report the capabilities of a dewetting-based process, independent of the sample size, to fabricate Si-based resonators over large scales starting from commercial silicon-on-insulator (SOI) substrates. Spontaneous dewetting is shown to allow the production of monocrystalline Mie-resonators that feature two resonant modes in the visible spectrum, as observed in confocal scattering spectroscopy. Homogeneous scattering responses and improved spatial ordering of the Si-based resonators are observed when dewetting is assisted by electron beam lithography. Finally, exploiting different thermal agglomeration regimes, we highlight the versatility of this technique, which, when assisted by focused ion beam nanopatterning, produces monocrystalline nanocrystals with ad hoc size, position, and organization in complex multimers.

Effect of dopants on annealing performance of silicon solar cells

NASA Technical Reports Server (NTRS)

Scott-Monck, J. A.; Anspaugh, B. E.

1979-01-01

The optimum annealing parameters of time and temperature for producing cell output recovery were established. Devices made from gallium doped and boron doped silicon were investigated. The cells ranged in resistivity from 0.1 to 20 ohm-cm and in thickness from 50 to 250 micrometers. The observations can be explained in a qualitative manner by postulating a pair of competing mechanisms to account for the low temperature reverse annealing seen in most boron and gallium doped silicon solar cells. Still another mechanism dominates at higher temperatures (350 C and greater) to complete this model. One of the mechanisms, defined as B, allows migrators to couple with radiation induced recombination sites thus increasing or enhancing their capture cross sections. This would tend to reduce minority carrier diffusion length. The new recombination complex is postulated to be thermally stable up to temperatures of approximately 350 C.

The Current State of Silicone-Based Dielectric Elastomer Transducers.

PubMed

Madsen, Frederikke B; Daugaard, Anders E; Hvilsted, Søren; Skov, Anne L

2016-03-01

Silicone elastomers are promising materials for dielectric elastomer transducers (DETs) due to their superior properties such as high efficiency, reliability and fast response times. DETs consist of thin elastomer films sandwiched between compliant electrodes, and they constitute an interesting class of transducer due to their inherent lightweight and potentially large strains. For the field to progress towards industrial implementation, a leap in material development is required, specifically targeting longer lifetime and higher energy densities to provide more efficient transduction at lower driving voltages. In this review, the current state of silicone elastomers for DETs is summarised and critically discussed, including commercial elastomers, composites, polymer blends, grafted elastomers and complex network structures. For future developments in the field it is essential that all aspects of the elastomer are taken into account, namely dielectric losses, lifetime and the very often ignored polymer network integrity and stability. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Diffusion Bonding of Silicon Carbide for a Micro-Electro-Mechanical Systems Lean Direct Injector

NASA Technical Reports Server (NTRS)

Halbig, Michael C.; Singh, Mrityunjay; Shpargel, Tarah P.; Kiser, James D.

2006-01-01

Robust approaches for joining silicon carbide (SiC) to silicon carbide sub-elements have been developed for a micro-electro-mechanical systems lean direct injector (MEMS LDI) application. The objective is to join SiC sub-elements to form a leak-free injector that has complex internal passages for the flow and mixing of fuel and air. Previous bonding technology relied upon silicate glass interlayers that were not uniform or leak free. In a newly developed joining approach, titanium foils and physically vapor deposited titanium coatings were used to form diffusion bonds between SiC materials during hot pressing. Microscopy results show the formation of well adhered diffusion bonds. Initial tests show that the bond strength is much higher than required for the component system. Benefits of the joining technology are fabrication of leak free joints with high temperature and mechanical capability.

Experimental demonstration of two-dimensional hybrid waveguide-integrated plasmonic crystals on silicon-on-insulator platform

NASA Astrophysics Data System (ADS)

Ren, Guanghui; Yudistira, Didit; Nguyen, Thach G.; Khodasevych, Iryna; Schoenhardt, Steffen; Berean, Kyle J.; Hamm, Joachim M.; Hess, Ortwin; Mitchell, Arnan

2017-07-01

Nanoscale plasmonic structures can offer unique functionality due to extreme sub-wavelength optical confinement, but the realization of complex plasmonic circuits is hampered by high propagation losses. Hybrid approaches can potentially overcome this limitation, but only few practical approaches based on either single or few element arrays of nanoantennas on dielectric nanowire have been experimentally demonstrated. In this paper, we demonstrate a two dimensional hybrid photonic plasmonic crystal interfaced with a standard silicon photonic platform. Off resonance, we observe low loss propagation through our structure, while on resonance we observe strong propagation suppression and intense concentration of light into a dense lattice of nanoscale hot-spots on the surface providing clear evidence of a hybrid photonic plasmonic crystal bandgap. This fully integrated approach is compatible with established silicon-on-insulator (SOI) fabrication techniques and constitutes a significant step toward harnessing plasmonic functionality within SOI photonic circuits.

Direct monolithic integration of vertical single crystalline octahedral molecular sieve nanowires on silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carretero-Genevrier, Adrian; Oro-Sole, Judith; Gazquez, Jaume

2013-12-13

We developed an original strategy to produce vertical epitaxial single crystalline manganese oxide octahedral molecular sieve (OMS) nanowires with tunable pore sizes and compositions on silicon substrates by using a chemical solution deposition approach. The nanowire growth mechanism involves the use of track-etched nanoporous polymer templates combined with the controlled growth of quartz thin films at the silicon surface, which allowed OMS nanowires to stabilize and crystallize. α-quartz thin films were obtained after thermal activated crystallization of the native amorphous silica surface layer assisted by Sr 2+- or Ba 2+-mediated heterogeneous catalysis in the air at 800 °C. These α-quartzmore » thin films work as a selective template for the epitaxial growth of randomly oriented vertical OMS nanowires. Furthermore, the combination of soft chemistry and epitaxial growth opens new opportunities for the effective integration of novel technological functional tunneled complex oxides nanomaterials on Si substrates.« less

Nonlinear Silicon Photonics: Extending Platforms, Control, and Applications

NASA Astrophysics Data System (ADS)

Miller, Steven Andrew

Silicon photonics is a revolutionary technology that enables the control of light inside a silicon chip and holds promise to impact many applications from data center optical interconnects to optical sensing and even quantum optics. The tight confinement of light inside these chips greatly enhances light-matter interactions, making this an ideal platform for nonlinear photonics. Recently, microresonator-based Kerr frequency comb generation has become a prevalent emerging field, enabling the generation of a broadband optical pulse train by inputting a low-power continuous-wave laser into a low-loss chip-scale micro-cavity. These chip-scale combs have a wide variety of applications, including optical clocks, optical spectroscopy, and data communications. Several important applications in biological, chemical and atmospheric areas require combs generated in the visible and mid-infrared wavelength ranges, where there has been far less research and development compared with the near-infrared. Additionally, most platforms widely for combs are passive, limiting the ability to control and optimize the frequency combs. In this dissertation, we set out to address these shortcomings and introduce new tunability as well as wavelength flexibility in order to enable new applications for microresonator frequency combs. The silicon nitride platform for near-infrared combs is generally a passive platform with limited tuning capabilities. We overcome dispersion limitations in the visible range by leveraging the second-order nonlinearity of silicon nitride and demonstrate visible comb lines. We then further investigate the second-order nonlinearity of silicon nitride by measuring the linear electro-optic effect, a potential tuning mechanism. Finally, we introduce thermal tuning onto the silicon nitride platform and demonstrate tuning of the resonance extinction and dispersion of a micro-cavity using a coupled cavity design. We also address the silicon mid-infrared frequency comb platform. The transparency range of the traditional silicon platform prohibits operation beyond 4 mum wavelength. Here we show that a silicon photonics platform can be leveraged for broadband mid-infrared operation without introducing complexity in fabrication. Both an air-clad and fully suspended silicon platform can enable broadband, low-loss propagation and comb generation as high as 6 mum. We demonstrate a high quality factor resonator near 4 mum wavelength, more than an order of magnitude higher than the traditional platform. Finally, we discuss future avenues of research building on the work presented here.

Impact of pre- and/or syn-tectonic salt layers in the hangingwall geometry of a kinked-planar extensional fault: insights from analogue modelling and comparison with the Parentis basin (bay of Biscay)

NASA Astrophysics Data System (ADS)

Ferrer, O.; Vendeville, B. C.; Roca, E.

2012-04-01

Using sandbox analogue modelling we determine the role played by a pre-kinematic or a syn-kinematic viscous salt layer during rollover folding of the hangingwall of a normal fault with a variable kinked-planar geometry, as well as understand the origin and the mechanisms that control the formation, kinematic evolution and geometry of salt structures developed in the hangingwall of this fault. The experiments we conducted consisted of nine models made of dry quartz-sand (35μm average grain size) simulating brittle rocks and a viscous silicone polymer (SMG 36 from Dow Corning) simulating salt in nature. The models were constructed between two end walls, one of which was fixed, whereas the other was moved by a motor-driven worm screw. The fixed wall was part of the rigid footwall of the model's master border fault. This fault was simulated using three different wood block configurations, which was overlain by a flexible (but not stretchable) sheet that was attached to the mobile endwall of the model. We applied three different infill hangingwall configurations to each fault geometry: (1) without silicone (sand only), (2) sand overlain by a pre-kinematic silicone layer deposited above the entire hanginwall, and (3) sand partly overlain by a syn-kinematic silicone layer that overlain only parts of the hangingwall. All models were subjected to a 14 cm of basement extension in a direction orthogonal to that of the border fault. Results show that the presence of a viscous layer (silicone) clearly controls the deformation pattern of the hangingwall. Thus, regardless of the silicone layer's geometry (either pre- or syn-extensional) or the geometry of the extensional fault, the silicone layer acts as a very efficient detachment level separating two different structural styles in each unit. In particular, the silicone layer acts as an extensional ductile shear zone inhibiting upward propagation of normal faults and/or shears bands from the sub-silicone layers. Whereas the basement is affected by antithetic normal faults that are more or less complex depending on the geometry of the master fault, the lateral flow of the silicone produces salt-cored anticlines, walls and diapirs in the overburden of the hangingwall. The mechanical behavior of the silicone layer as an extensional shear zone, combined with the lateral changes in pressure gradients due to overburden thickness changes, triggered the silicone migration from the half-graben depocenter towards the rollover shoulder. As a result, the accumulation of silicone produces gentle silicone-cored anticlines and local diapirs with minor extensional faults. Upwards fault propagation from the sub-silicone "basement" to the supra-silicone unit only occurs either when the supra- and sub-silicone materials are welded, or when the amount of slip along the master fault is large enough so that the tip of the silicone reaches the junction between the upper and lower panels of the master faults. Comparison between the results of these models with data from the western offshore Parentis Basin (Eastern Bay of Biscay) validates the structural interpretation of this region.

75 FR 9869 - Silicon Metal From the People's Republic of China: Extension of Time Limit for the Preliminary...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-03-04

... information pertaining to complex issues, including surrogate value information relating to certain raw material inputs. Therefore, in accordance with section 751(a)(3)(A) of the Act, the Department is extending...

A prospective study on silicone breast implants and the silicone-related symptom complex.

PubMed

Contant, C M E; Swaak, A J G; Obdeijn, A I M; van der Holt, B; Tjong Joe Wai, R; van Geel, A N; Eggermont, A M M

2002-06-01

This cohort study prospectively evaluated the prevalence of the silicone-related symptom complex (SRSC) in relation to antinuclear antibodies (ANA) and magnetic resonance imaging (MRI) of silicone breast implants (SBI) 1 year after implantation. A total of 57 women undergoing mastectomy followed by immediate breast reconstruction (IBR) and SBI between March 1995 and March 1997 at the University Hospital Rotterdam/Daniel den Hoed Cancer Centre, were prospectively evaluated. Just before and 1 year after IBR the sera of these women were tested for the presence of ANA and they were screened for the prevalence of SRSC-related symptoms by questionnaire. All prostheses were evaluated by MRI 1 month and 1 year after IBR. Just before operation 11% of the women had a Sjögren score of more than 2, whereas 30% had such a score 1 year after IBR ( P = 0.01). One year postoperatively women had significantly more RA/Raynaud-related complaints: 21% preoperatively versus 40% 1 year after IBR ( P = 0.03). Within the undefined complaints-related group 19% had a score of 2 or more preoperatively and 33% 1 year after IBR ( P = 0.09). There were no new cases of ANA positivity 1 year after IBR. The linguine sign was seen by MRI in three implants: one 1 month after IBR and two 1 year after IBR. There was no relation to changes in SRSC expression and these MRI findings. In conclusion, 1 year after SBI implantation women had more SRSC-related complaints, especially Sjögren's and RA/Raynaud's. Moreover there was no correlation between elevated SRSC expression and changes in the presence of ANA or changes in MRI of the SBI 1 year after IBR.

Utility of silicone esophageal bypass stents in the management of delayed complex esophageal disruptions.

PubMed

Kim, Anthony W; Liptay, Michael J; Snow, Norman; Donahue, Philip; Warren, William H

2008-06-01

The objective of this study was to review the clinical experience of temporarily placing an endoesophageal silicone salivary bypass stent and its value in managing patients with life-threatening esophageal disruptions. Clinical records of patients undergoing placement of silicone Montgomery salivary bypass stents from June 1998 to September 2007 were reviewed. Seventeen patients had a proven esophageal disruption in the absence of malignancy and with life-threatening sepsis refractory to conventional management. Underlying conditions were iatrogenic trauma from prior pulmonary surgery (4 patients), significant anastomotic leaks after an esophagogastrectomy (4 patients), delayed presentation (> 24 hours) of a perforated esophagus (4 patients), leak after esophageal surgery (3 patients), and esophagobronchial fistula secondary to inflammation and infection (2 patients). Stents were placed without securing, were sutured in place to the esophageal wall at the time of thoracotomy, or were secured by bringing holding sutures through the nostrils and tied over the bridge of the nose. In all cases, placement of the esophageal stent led to prompt improvement of the leak and, within a week, improvement of the sepsis. Supportive measures were continued after placement of the stent. Sixteen patients overcame the sepsis with ultimate healing of the esophageal disruption (13 patients) or maturation of the perforation into a chronic fistula (3 patients). Endoscopic stent removal was performed 2 to 16 weeks after placement. No patient had a stricture develop at the disruption site. One patient died of ruptured thoracic aorta. Silicone salivary bypass stents serve as an effective way of diverting and excluding the oral-alimentary stream, thereby providing optimal conditions for sepsis control. They are a useful adjunct in the management of complex esophageal conditions.

New technique for heterogeneous vapor-phase synthesis of nanostructured metal layers from low-dimensional volatile metal complexes

NASA Astrophysics Data System (ADS)

Badalyan, A. M.; Bakhturova, L. F.; Kaichev, V. V.; Polyakov, O. V.; Pchelyakov, O. P.; Smirnov, G. I.

2011-09-01

A new technique for depositing thin nanostructured layers on semiconductor and insulating substrates that is based on heterogeneous gas-phase synthesis from low-dimensional volatile metal complexes is suggested and tried out. Thin nanostructured copper layers are deposited on silicon and quartz substrates from low-dimensional formate complexes using a combined synthesis-mass transport process. It is found that copper in layers thus deposited is largely in a metal state (Cu0) and has the form of closely packed nanograins with a characteristic structure.

Review of CMOS Integrated Circuit Technologies for High-Speed Photo-Detection

PubMed Central

Jeong, Gyu-Seob

2017-01-01

The bandwidth requirement of wireline communications has increased exponentially because of the ever-increasing demand for data centers and high-performance computing systems. However, it becomes difficult to satisfy the requirement with legacy electrical links which suffer from frequency-dependent losses due to skin effects, dielectric losses, channel reflections, and crosstalk, resulting in a severe bandwidth limitation. In order to overcome this challenge, it is necessary to introduce optical communication technology, which has been mainly used for long-reach communications, such as long-haul networks and metropolitan area networks, to the medium- and short-reach communication systems. However, there still remain important issues to be resolved to facilitate the adoption of the optical technologies. The most critical challenges are the energy efficiency and the cost competitiveness as compared to the legacy copper-based electrical communications. One possible solution is silicon photonics which has long been investigated by a number of research groups. Despite inherent incompatibility of silicon with the photonic world, silicon photonics is promising and is the only solution that can leverage the mature complementary metal-oxide-semiconductor (CMOS) technologies. Silicon photonics can be utilized in not only wireline communications but also countless sensor applications. This paper introduces a brief review of silicon photonics first and subsequently describes the history, overview, and categorization of the CMOS IC technology for high-speed photo-detection without enumerating the complex circuital expressions and terminologies. PMID:28841154

Review of CMOS Integrated Circuit Technologies for High-Speed Photo-Detection.

PubMed

Jeong, Gyu-Seob; Bae, Woorham; Jeong, Deog-Kyoon

2017-08-25

The bandwidth requirement of wireline communications has increased exponentially because of the ever-increasing demand for data centers and high-performance computing systems. However, it becomes difficult to satisfy the requirement with legacy electrical links which suffer from frequency-dependent losses due to skin effects, dielectric losses, channel reflections, and crosstalk, resulting in a severe bandwidth limitation. In order to overcome this challenge, it is necessary to introduce optical communication technology, which has been mainly used for long-reach communications, such as long-haul networks and metropolitan area networks, to the medium- and short-reach communication systems. However, there still remain important issues to be resolved to facilitate the adoption of the optical technologies. The most critical challenges are the energy efficiency and the cost competitiveness as compared to the legacy copper-based electrical communications. One possible solution is silicon photonics which has long been investigated by a number of research groups. Despite inherent incompatibility of silicon with the photonic world, silicon photonics is promising and is the only solution that can leverage the mature complementary metal-oxide-semiconductor (CMOS) technologies. Silicon photonics can be utilized in not only wireline communications but also countless sensor applications. This paper introduces a brief review of silicon photonics first and subsequently describes the history, overview, and categorization of the CMOS IC technology for high-speed photo-detection without enumerating the complex circuital expressions and terminologies.

Customized silicone implant for the correction of acquired and congenital chest wall deformities: A valuable option with pectus excavatum.

PubMed

Soccorso, Giampiero; Parikh, Dakshesh H; Worrollo, Steve

2015-07-01

Surgical remodeling and correction of congenital and acquired chest wall deformities (CWD) is undertaken many times for cosmesis. Although reportedly minimally invasive, commonly used Nuss procedure for correction of pectus excavatum (PE) is not without complications. Nuss procedure is also not suitable for complex deformities and Poland syndrome cases. Insertion of custom-made silicone implants for the reconstruction of defects has been adopted from adult plastic reconstructive surgery as primary repair of CWD or rescue procedure for recurrence of PE after recurrence or residual deformity. We present our experience with CWD reconstruction in children with customized silicone prosthesis made from a surgically implantable liquid silicone rubber (NuSil MED-4805, Ca). Since 2006 we treated 26 patients with CWD: six were children (age <17years, median 14.6) with PE. Implants were custom made for each patient's chest. The implants were inserted under general anesthesia. Postoperatively all patients were fully satisfied with the cosmetic result and subjective patient satisfaction remained excellent at follow-up in all the children. Only one child developed postoperative complications (seroma). Customized silicone implant for PE in the pediatric age is an alternative therapeutic method, as primary or rescue treatment, with equally good cosmetic outcome, fewer significant complications, less postoperative pain and a faster recovery. Copyright © 2015 Elsevier Inc. All rights reserved.

Novel Approach for Positioning Sensor Lead Wires on SiC-Based Monolithic Ceramic and FRCMC Components/Subcomponents Having Flat and Curved Surfaces

NASA Technical Reports Server (NTRS)

Kiser, J. Douglas; Singh, Mrityunjay; Lei, Jin-Fen; Martin, Lisa C.

1999-01-01

A novel attachment approach for positioning sensor lead wires on silicon carbide-based monolithic ceramic and fiber reinforced ceramic matrix composite (FRCMC) components has been developed. This approach is based on an affordable, robust ceramic joining technology, named ARCJoinT, which was developed for the joining of silicon carbide-based ceramic and fiber reinforced composites. The ARCJoinT technique has previously been shown to produce joints with tailorable thickness and good high temperature strength. In this study, silicon carbide-based ceramic and FRCMC attachments of different shapes and sizes were joined onto silicon carbide fiber reinforced silicon carbide matrix (SiC/ SiC) composites having flat and curved surfaces. Based on results obtained in previous joining studies. the joined attachments should maintain their mechanical strength and integrity at temperatures up to 1350 C in air. Therefore they can be used to position and secure sensor lead wires on SiC/SiC components that are being tested in programs that are focused on developing FRCMCs for a number of demanding high temperature applications in aerospace and ground-based systems. This approach, which is suitable for installing attachments on large and complex shaped monolithic ceramic and composite components, should enhance the durability of minimally intrusive high temperature sensor systems. The technology could also be used to reinstall attachments on ceramic components that were damaged in service.

Fabrication of disposable topographic silicon oxide from sawtoothed patterns: control of arrays of gold nanoparticles.

PubMed

Cho, Heesook; Yoo, Hana; Park, Soojin

2010-05-18

Disposable topographic silicon oxide patterns were fabricated from polymeric replicas of sawtoothed glass surfaces, spin-coating of poly(dimethylsiloxane) (PDMS) thin films, and thermal annealing at certain temperature and followed by oxygen plasma treatment of the thin PDMS layer. A simple imprinting process was used to fabricate the replicated PDMS and PS patterns from sawtoothed glass surfaces. Next, thin layers of PDMS films having different thicknesses were spin-coated onto the sawtoothed PS surfaces and annealed at 60 degrees C to be drawn the PDMS into the valley of the sawtoothed PS surfaces, followed by oxygen plasma treatment to fabricate topographic silicon oxide patterns. By control of the thickness of PDMS layers, silicon oxide patterns having various line widths were fabricated. The silicon oxide topographic patterns were used to direct the self-assembly of polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) block copolymer thin films via solvent annealing process. A highly ordered PS-b-P2VP micellar structure was used to let gold precursor complex with P2VP chains, and followed by oxygen plasma treatment. When the PS-b-P2VP thin films containing gold salts were exposed to oxygen plasma environments, gold salts were reduced to pure gold nanoparticles without changing high degree of lateral order, while polymers were completely degraded. As the width of trough and crest in topographic patterns increases, the number of gold arrays and size of gold nanoparticles are tuned. In the final step, the silicon oxide topographic patterns were selectively removed by wet etching process without changing the arrays of gold nanoparticles.

Project analysis and integration economic analyses summary

NASA Technical Reports Server (NTRS)

Macomber, H. L.

1986-01-01

An economic-analysis summary was presented for the manufacture of crystalline-silicon modules involving silicon ingot/sheet, growth, slicing, cell manufacture, and module assembly. Economic analyses provided: useful quantitative aspects for complex decision-making to the Flat-plate Solar Array (FSA) Project; yardsticks for design and performance to industry; and demonstration of how to evaluate and understand the worth of research and development both to JPL and other government agencies and programs. It was concluded that future research and development funds for photovoltaics must be provided by the Federal Government because the solar industry today does not reap enough profits from its present-day sales of photovoltaic equipment.

Pentacoordinate silicon(IV): cationic, anionic and neutral complexes derived from the reaction of NHC→SiCl4 with highly Lewis acidic (C2F5)2SiH2.

PubMed

Böttcher, T; Steinhauer, S; Neumann, B; Stammler, H-G; Röschenthaler, G-V; Hoge, B

2014-06-14

Addition of NHC→SiCl4 to the highly Lewis acidic bis(pentafluoroethyl)silane ((C2F5)2SiH2) afforded the salt [(NHC)2SiCl2H][(C2F5)2SiCl3] with pentacoordinate silicon in the cation and the anion. The anion represents the first example of a chlorosilicate structurally characterized in the solid state. In this reaction, the long sought pentacoordinate NHC-adduct of silicochloroform was identified as an intermediate and its crystal structure is presented.

Deployment Testing of Flexible Composite Hinges in Bi-Material Beams

NASA Technical Reports Server (NTRS)

Sauder, Jonathan F.; Trease, Brian

2016-01-01

Composites have excellent properties for strength, thermal stability, and weight. However, they are traditionally highly rigid, and when used in deployable structures require hinges bonded to the composite material, which increases complexity and opportunities for failure. Recent research in composites has found by adding an elastomeric soft matrix, often silicone instead of an epoxy, the composite becomes flexible. This work explores the deployment repeatability of silicone matrix composite hinges which join rigid composite beams. The hinges were found to have sub-millimeter linear deployment repeatability, and sub-degree angular deployment repeatability. Also, an interesting relaxation effect was discovered, as a hinges deployment error would decrease with time.

Frequency comb generation in a silicon ring resonator modulator.

PubMed

Demirtzioglou, Iosif; Lacava, Cosimo; Bottrill, Kyle R H; Thomson, David J; Reed, Graham T; Richardson, David J; Petropoulos, Periklis

2018-01-22

We report on the generation of an optical comb of highly uniform in power frequency lines (variation less than 0.7 dB) using a silicon ring resonator modulator. A characterization involving the measurement of the complex transfer function of the ring is presented and five frequency tones with a 10-GHz spacing are produced using a dual-frequency electrical input at 10 and 20 GHz. A comb shape comparison is conducted for different modulator bias voltages, indicating optimum operation at a small forward-bias voltage. A time-domain measurement confirmed that the comb signal was highly coherent, forming 20.3-ps-long pulses.

Addressable Inverter Matrix Tests Integrated-Circuit Wafer

NASA Technical Reports Server (NTRS)

Buehler, Martin G.

1988-01-01

Addressing elements indirectly through shift register reduces number of test probes. With aid of new technique, complex test structure on silicon wafer tested with relatively small number of test probes. Conserves silicon area by reduction of area devoted to pads. Allows thorough evaluation of test structure characteristics and of manufacturing process parameters. Test structure consists of shift register and matrix of inverter/transmission-gate cells connected to two-by-ten array of probe pads. Entire pattern contained in square area having only 1.6-millimeter sides. Shift register is conventional static CMOS device using inverters and transmission gates in master/slave D flip-flop configuration.

Complexing agents and pH influence on chemical durability of type I moulded glass containers.

PubMed

Biavati, Alberto; Poncini, Michele; Ferrarini, Arianna; Favaro, Nicola; Scarpa, Martina; Vallotto, Marta

2017-06-16

Among the factors that affect the glass surface chemical durability, pH and complexing agents presence in aqueous solution have the main role (1). Glass surface attack can be also related to the delamination issue with glass particles appearance in the pharmaceutical preparation. A few methods to check for glass containers delamination propensity and some control guidelines have been proposed (2,3). The present study emphasizes the possible synergy between a few complexing agents with pH on the borosilicate glass chemical durability. Hydrolytic attack was performed in small volume 23 ml type I glass containers autoclaved according to EP or USP for 1 hour at 121°C, in order to enhance the chemical attack due to time, temperature and the unfavourable surface/volume ratio. 0,048 M or 0.024 M (moles/liter) solutions of the acids citric, glutaric, acetic, EDTA (ethylenediaminetetraacetic acid) and sodium phosphate with water for comparison, were used for the trials. The pH was adjusted ± 0,05 units at fixed values 5,5-6,6-7-7,4-8-9 by LiOH diluted solution. Since silicon is the main glass network former, silicon release into the attack solutions was chosen as the main index of the glass surface attack and analysed by ICPAES. The work was completed by the analysis of the silicon release in the worst attack conditions, of moulded glass, soda lime type II and tubing borosilicate glass vials to compare different glass compositions and forming technologies. Surface analysis by SEM was finally performed to check for the surface status after the worst chemical attack condition by citric acid. Copyright © 2017, Parenteral Drug Association.

Next-generation digital camera integration and software development issues

NASA Astrophysics Data System (ADS)

Venkataraman, Shyam; Peters, Ken; Hecht, Richard

1998-04-01

This paper investigates the complexities associated with the development of next generation digital cameras due to requirements in connectivity and interoperability. Each successive generation of digital camera improves drastically in cost, performance, resolution, image quality and interoperability features. This is being accomplished by advancements in a number of areas: research, silicon, standards, etc. As the capabilities of these cameras increase, so do the requirements for both hardware and software. Today, there are two single chip camera solutions in the market including the Motorola MPC 823 and LSI DCAM- 101. Real time constraints for a digital camera may be defined by the maximum time allowable between capture of images. Constraints in the design of an embedded digital camera include processor architecture, memory, processing speed and the real-time operating systems. This paper will present the LSI DCAM-101, a single-chip digital camera solution. It will present an overview of the architecture and the challenges in hardware and software for supporting streaming video in such a complex device. Issues presented include the development of the data flow software architecture, testing and integration on this complex silicon device. The strategy for optimizing performance on the architecture will also be presented.

Core-Shell Coating Silicon Anode Interfaces with Coordination Complex for Stable Lithium-Ion Batteries.

PubMed

Zhou, Jinqiu; Qian, Tao; Wang, Mengfan; Xu, Na; Zhang, Qi; Li, Qun; Yan, Chenglin

2016-03-02

In situ core-shell coating was used to improve the electrochemical performance of Si-based anodes with polypyrrole-Fe coordination complex. The vast functional groups in the organometallic coordination complex easily formed hydrogen bonds when in situ modifying commercial Si nanoparticles. The incorporation of polypyrrole-Fe resulted in the conformal conductive coating surrounding each Si nanoparticle, not only providing good electrical connection to the particles but also promoting the formation of a stable solid-electrolyte-interface layer on the Si electrode surface, enhancing the cycling properties. As an anode material for Li-ion batteries, modified silicon powders exhibited high reversible capacity (3567 mAh/g at 0.3 A/g), good rate property (549.12 mAh/g at 12 A/g), and excellent cycling performance (reversible capacity of 1500 mAh/g after 800 cycles at 1.2 A/g). The constructed novel concept of core-shell coating Si particles presented a promising route for facile and large-scale production of Si-based anodes for extremely durable Li-ion batteries, which provided a wide range of applications in the field of energy storage of the renewable energy derived from the solar energy, hydropower, tidal energy, and geothermal heat.

Nanoscale patterning of two metals on silicon surfaces using an ABC triblock copolymer template.

PubMed

Aizawa, Masato; Buriak, Jillian M

2006-05-03

Patterning technologically important semiconductor interfaces with nanoscale metal films is important for applications such as metallic interconnects and sensing applications. Self-assembling block copolymer templates are utilized to pattern an aqueous metal reduction reaction, galvanic displacement, on silicon surfaces. Utilization of a triblock copolymer monolayer film, polystyrene-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) (PS-b-P2VP-b-PEO), with two blocks capable of selective transport of different metal complexes to the surface (PEO and P2VP), allows for chemical discrimination and nanoscale patterning. Different regions of the self-assembled structure discriminate between metal complexes at the silicon surface, at which time they undergo the spontaneous reaction at the interface. Gold deposition from gold(III) compounds such as HAuCl4(aq) in the presence of hydrofluoric acid mirrors the parent block copolymer core structure, whereas silver deposition from Ag(I) salts such as AgNO3(aq) does the opposite, localizing exclusively under the corona. By carrying out gold deposition first and silver second, sub-100-nm gold features surrounded by silver films can be produced. The chemical selectivity was extended to other metals, including copper, palladium, and platinum. The interfaces were characterized by a variety of methods, including scanning electron microscopy, scanning Auger microscopy, X-ray photoelectron spectroscopy, and atomic force microscopy.

Characterization of iron in silicon by low-temperature photoluminescence and deep-level transient spectroscopy

NASA Astrophysics Data System (ADS)

Nakamura, Minoru; Murakami, Susumu; Udono, Haruhiko

2018-03-01

We investigate the relationship between the intensity of band-edge (BDE) photoluminescence (PL) from 10 to 70 K and the concentration of iron diffused in boron-doped p-type silicon. Because of the nonradiative recombination activity of the interstitial iron-boron complex (FeiB center), the BDE-PL intensity at each temperature varies distinctively and systematically with the iron concentration, which means that this method has the potential to make the accurate measurements of a wide range of interstitial iron concentrations in silicon. The iron precipitates formed in the bulk and/or at the surface are found to exert much weaker recombination activity for excess carriers than FeiB center by exploiting both PL and deep-level transient spectroscopy (DLTS) measurements. The unexpected enhancement in BDE-PL intensity from iron-diffused silicon between 20 and 50 K is attributed to the passivation of the Si-oxide/Si interface by iron. For the samples diffused with trace amounts of iron, the iron concentration within 20 μm of the surface is significantly greater than that in the bulk, as measured by DLTS. This result is tentatively attributed to the affinity of iron with the Si-oxide.

Self-assembled micro-organogels for 3D printing silicone structures.

PubMed

O'Bryan, Christopher S; Bhattacharjee, Tapomoy; Hart, Samuel; Kabb, Christopher P; Schulze, Kyle D; Chilakala, Indrasena; Sumerlin, Brent S; Sawyer, W Gregory; Angelini, Thomas E

2017-05-01

The widespread prevalence of commercial products made from microgels illustrates the immense practical value of harnessing the jamming transition; there are countless ways to use soft, solid materials that fluidize and become solid again with small variations in applied stress. The traditional routes of microgel synthesis produce materials that predominantly swell in aqueous solvents or, less often, in aggressive organic solvents, constraining ways that these exceptionally useful materials can be used. For example, aqueous microgels have been used as the foundation of three-dimensional (3D) bioprinting applications, yet the incompatibility of available microgels with nonpolar liquids, such as oils, limits their use in 3D printing with oil-based materials, such as silicone. We present a method to make micro-organogels swollen in mineral oil, using block copolymer self-assembly. The rheological properties of this micro-organogel material can be tuned, leveraging the jamming transition to facilitate its use in 3D printing of silicone structures. We find that the minimum printed feature size can be controlled by the yield stress of the micro-organogel medium, enabling the fabrication of numerous complex silicone structures, including branched perfusable networks and functional fluid pumps.

Self-assembled micro-organogels for 3D printing silicone structures

PubMed Central

O’Bryan, Christopher S.; Bhattacharjee, Tapomoy; Hart, Samuel; Kabb, Christopher P.; Schulze, Kyle D.; Chilakala, Indrasena; Sumerlin, Brent S.; Sawyer, W. Gregory; Angelini, Thomas E.

2017-01-01

The widespread prevalence of commercial products made from microgels illustrates the immense practical value of harnessing the jamming transition; there are countless ways to use soft, solid materials that fluidize and become solid again with small variations in applied stress. The traditional routes of microgel synthesis produce materials that predominantly swell in aqueous solvents or, less often, in aggressive organic solvents, constraining ways that these exceptionally useful materials can be used. For example, aqueous microgels have been used as the foundation of three-dimensional (3D) bioprinting applications, yet the incompatibility of available microgels with nonpolar liquids, such as oils, limits their use in 3D printing with oil-based materials, such as silicone. We present a method to make micro-organogels swollen in mineral oil, using block copolymer self-assembly. The rheological properties of this micro-organogel material can be tuned, leveraging the jamming transition to facilitate its use in 3D printing of silicone structures. We find that the minimum printed feature size can be controlled by the yield stress of the micro-organogel medium, enabling the fabrication of numerous complex silicone structures, including branched perfusable networks and functional fluid pumps. PMID:28508071

Optical interconnection networks for high-performance computing systems

NASA Astrophysics Data System (ADS)

Biberman, Aleksandr; Bergman, Keren

2012-04-01

Enabled by silicon photonic technology, optical interconnection networks have the potential to be a key disruptive technology in computing and communication industries. The enduring pursuit of performance gains in computing, combined with stringent power constraints, has fostered the ever-growing computational parallelism associated with chip multiprocessors, memory systems, high-performance computing systems and data centers. Sustaining these parallelism growths introduces unique challenges for on- and off-chip communications, shifting the focus toward novel and fundamentally different communication approaches. Chip-scale photonic interconnection networks, enabled by high-performance silicon photonic devices, offer unprecedented bandwidth scalability with reduced power consumption. We demonstrate that the silicon photonic platforms have already produced all the high-performance photonic devices required to realize these types of networks. Through extensive empirical characterization in much of our work, we demonstrate such feasibility of waveguides, modulators, switches and photodetectors. We also demonstrate systems that simultaneously combine many functionalities to achieve more complex building blocks. We propose novel silicon photonic devices, subsystems, network topologies and architectures to enable unprecedented performance of these photonic interconnection networks. Furthermore, the advantages of photonic interconnection networks extend far beyond the chip, offering advanced communication environments for memory systems, high-performance computing systems, and data centers.

Fabrication and Modification of Nanoporous Silicon Particles

NASA Technical Reports Server (NTRS)

Ferrari, Mauro; Liu, Xuewu

2010-01-01

Silicon-based nanoporous particles as biodegradable drug carriers are advantageous in permeation, controlled release, and targeting. The use of biodegradable nanoporous silicon and silicon dioxide, with proper surface treatments, allows sustained drug release within the target site over a period of days, or even weeks, due to selective surface coating. A variety of surface treatment protocols are available for silicon-based particles to be stabilized, functionalized, or modified as required. Coated polyethylene glycol (PEG) chains showed the effective depression of both plasma protein adsorption and cell attachment to the modified surfaces, as well as the advantage of long circulating. Porous silicon particles are micromachined by lithography. Compared to the synthesis route of the nanomaterials, the advantages include: (1) the capability to make different shapes, not only spherical particles but also square, rectangular, or ellipse cross sections, etc.; (2) the capability for very precise dimension control; (3) the capacity for porosity and pore profile control; and (4) allowance of complex surface modification. The particle patterns as small as 60 nm can be fabricated using the state-of-the-art photolithography. The pores in silicon can be fabricated by exposing the silicon in an HF/ethanol solution and then subjecting the pores to an electrical current. The size and shape of the pores inside silicon can be adjusted by the doping of the silicon, electrical current application, the composition of the electrolyte solution, and etching time. The surface of the silicon particles can be modified by many means to provide targeted delivery and on-site permanence for extended release. Multiple active agents can be co-loaded into the particles. Because the surface modification of particles can be done on wafers before the mechanical release, asymmetrical surface modification is feasible. Starting from silicon wafers, a treatment, such as KOH dipping or reactive ion etching (RIE), may be applied to make the surface rough. This helps remove the nucleation layer. A protective layer is then deposited on the wafer. The protective layer, such as silicon nitride film or photoresist film, protects the wafer from electrochemical etching in an HF-based solution. A lithography technique is applied to pattern the particles onto the protective film. The undesired area of the protective film is removed, and the protective film on the back side of the wafer is also removed. Then the pattern is exposed to HF/surfactant solution, and a larger DC electrical current is applied to the wafers for a selected time. This step removes the nucleation layer. Then a DC current is applied to generate the nanopores. Next, a large electrical current is applied to generate a release layer. The particles are mechanically suspended in the solvent and collected by filtration or centrifuge.

Identification of vacancy-oxygen complexes in oxygen-implanted silicon probed with slow positrons

NASA Astrophysics Data System (ADS)

Fujinami, M.; Miyagoe, T.; Sawada, T.; Suzuki, R.; Ohdaira, T.; Akahane, T.

2004-04-01

Defects and their annealing behavior for low (2×1015/cm2) and high (1.7×1018/cm2) doses of 180 keV oxygen-implanted silicon have been investigated by the coincidence Doppler broadening (CDB) and lifetime measurements in variable-energy positron annihilation spectroscopy. In the low-dose sample, divacancies are induced throughout the entire implantation region. In the vacancy-oxygen coexisting region (300-500 nm depths), by raising the annealing temperature to 600 °C, vacancy-oxygen VxOy complexes with one vacant site are formed and, simultaneously, the migration of oxygen begins to takes place. In the vacancy-rich region (-200 nm depths), the evolution of simple vacancy clusters to V4 is mainly observed below 600 °C. From CDB and lifetime measurements, it has been proven that after annealing at 800 °C, the VxOy complexes are formed throughout the implanted region and they contain four vacant sites and a high ratio of y to x. On the other hand, high-dose implantation at 550 °C produces the VxOy complexes with a lifetime of a 430 ps in the near-surface region (less than 200 nm deep) and annealing at 1100 °C leads to the highest ratio of y to x. These complexes cannot be annealed out even by annealing at 1350 °C, and their structure is found to be very similar to that for the electron-irradiated amorphous SiO2.

3D printing PLA and silicone elastomer structures with sugar solution support material

NASA Astrophysics Data System (ADS)

Hamidi, Armita; Jain, Shrenik; Tadesse, Yonas

2017-04-01

3D printing technology has been used for rapid prototyping since 1980's and is still developing in a way that can be used for customized products with complex design and miniature features. Among all the available 3D printing techniques, Fused Deposition Modeling (FDM) is one of the most widely used technologies because of its capability to build different structures by employing various materials. However, complexity of parts made by FDM is greatly limited by restriction of using support materials. Support materials are often used in FDM for several complex geometries such as fully suspended shapes, overhanging surfaces and hollow features. This paper describes an approach to 3D print a structure using silicone elastomer and polylactide fiber (PLA) by employing a novel support material that is soluble in water. This support material is melted sugar which can easily be prepared at a low cost. Sugar is a carbohydrate, which is found naturally in plants such as sugarcane and sugar beets; therefore, it is completely organic and eco-friendly. As another advantage, the time for removing this material from the part is considerably less than other commercially available support materials and it can be removed easily by warm water without leaving any trace. Experiments were done using an inexpensive desktop 3D printer to fabricate complex structures for use in soft robots. The results envision that further development of this system would contribute to a method of fabrication of complex parts with lower cost yet high quality.

Mesoscopic chaos mediated by Drude electron-hole plasma in silicon optomechanical oscillators

PubMed Central

Wu, Jiagui; Huang, Shu-Wei; Huang, Yongjun; Zhou, Hao; Yang, Jinghui; Liu, Jia-Ming; Yu, Mingbin; Lo, Guoqiang; Kwong, Dim-Lee; Duan, Shukai; Wei Wong, Chee

2017-01-01

Chaos has revolutionized the field of nonlinear science and stimulated foundational studies from neural networks, extreme event statistics, to physics of electron transport. Recent studies in cavity optomechanics provide a new platform to uncover quintessential architectures of chaos generation and the underlying physics. Here, we report the generation of dynamical chaos in silicon-based monolithic optomechanical oscillators, enabled by the strong and coupled nonlinearities of two-photon absorption induced Drude electron–hole plasma. Deterministic chaotic oscillation is achieved, and statistical and entropic characterization quantifies the chaos complexity at 60 fJ intracavity energies. The correlation dimension D2 is determined at 1.67 for the chaotic attractor, along with a maximal Lyapunov exponent rate of about 2.94 times the fundamental optomechanical oscillation for fast adjacent trajectory divergence. Nonlinear dynamical maps demonstrate the subharmonics, bifurcations and stable regimes, along with distinct transitional routes into chaos. This provides a CMOS-compatible and scalable architecture for understanding complex dynamics on the mesoscopic scale. PMID:28598426

Laser characterization of the depth profile of complex refractive index of PMMA implanted with 50 keV silicon ions

NASA Astrophysics Data System (ADS)

Stefanov, Ivan L.; Stoyanov, Hristiyan Y.; Petrova, Elitza; Russev, Stoyan C.; Tsutsumanova, Gichka G.; Hadjichristov, Georgi B.

2013-03-01

The depth profile of the complex refractive index of silicon ion (Si+) implanted polymethylmethacrylate (PMMA) is studied, in particular PMMA implanted with Si+ ions accelerated to a relatively low energy of 50 keV and at a fluence of 3.2 × 1015 cm-2. The ion-modified material with nano-clustered structure formed in the near(sub)surface layer of a thickness of about 100 nm is optically characterized by simulation based on reflection ellipsometry measurements at a wavelength of 632.8 nm (He-Ne laser). Being of importance for applications of ion-implanted PMMA in integrated optics, optoelectronics and optical communications, the effect of the index depth profile of Si+-implanted PMMA on the profile of the reflected laser beam due to laser-induced thermo-lensing in reflection is also analyzed upon illumination with a low power cw laser (wavelength 532 nm, optical power 10 - 50 mW).

Photolithography and Fluorescence Correlation Spectroscopy used to examine the rates of exchange in reverse micelle systems

NASA Astrophysics Data System (ADS)

Norris, Zach; Mawson, Cara; Johnson, Kyron; Kessler, Sarah; Rebecca, Anne; Wolf, Nathan; Lim, Michael; Nucci, Nathaniel

Reverse micelles are molecular complexes that encapsulate a nanoscale pool of water in a surfactant shell dissolved in non-polar solvent. These complexes have a wide range of applications, and in all cases, the degree to which reverse micelles (RM) exchange their contents is relevant for their use. Despite its importance, this aspect of RM behavior is poorly understood. Photolithography is employed here to create micro and nano scale fluidic systems in which mixing rates can be precisely measured using fluorescence correlation spectroscopy (FCS). Micro-channel patterns are etched using reactive ion etching process into a layer of silicon dioxide on crystalline silicon substrates. Solutions containing mixtures of reverse micelles, proteins, and fluorophores are placed into reservoirs in the patterns, while diffusion and exchange between RMs is monitored using a FCS system built from a modified confocal Raman spectrometer. Using this approach, the diffusion and exchange rates for RM systems are measured as a function of the components of the RM mixture. Funding provided by Rowan University.

Diffusion of point defects in crystalline silicon using the kinetic activation-relaxation technique method

DOE PAGES

Trochet, Mickaël; Béland, Laurent Karim; Joly, Jean -François; ...

2015-06-16

We study point-defect diffusion in crystalline silicon using the kinetic activation-relaxation technique (k-ART), an off-lattice kinetic Monte Carlo method with on-the-fly catalog building capabilities based on the activation-relaxation technique (ART nouveau), coupled to the standard Stillinger-Weber potential. We focus more particularly on the evolution of crystalline cells with one to four vacancies and one to four interstitials in order to provide a detailed picture of both the atomistic diffusion mechanisms and overall kinetics. We show formation energies, activation barriers for the ground state of all eight systems, and migration barriers for those systems that diffuse. Additionally, we characterize diffusion pathsmore » and special configurations such as dumbbell complex, di-interstitial (IV-pair+2I) superdiffuser, tetrahedral vacancy complex, and more. In conclusion, this study points to an unsuspected dynamical richness even for this apparently simple system that can only be uncovered by exhaustive and systematic approaches such as the kinetic activation-relaxation technique.« less

Integrating photonics with silicon nanoelectronics for the next generation of systems on a chip.

PubMed

Atabaki, Amir H; Moazeni, Sajjad; Pavanello, Fabio; Gevorgyan, Hayk; Notaros, Jelena; Alloatti, Luca; Wade, Mark T; Sun, Chen; Kruger, Seth A; Meng, Huaiyu; Al Qubaisi, Kenaish; Wang, Imbert; Zhang, Bohan; Khilo, Anatol; Baiocco, Christopher V; Popović, Miloš A; Stojanović, Vladimir M; Ram, Rajeev J

2018-04-01

Electronic and photonic technologies have transformed our lives-from computing and mobile devices, to information technology and the internet. Our future demands in these fields require innovation in each technology separately, but also depend on our ability to harness their complementary physics through integrated solutions 1,2 . This goal is hindered by the fact that most silicon nanotechnologies-which enable our processors, computer memory, communications chips and image sensors-rely on bulk silicon substrates, a cost-effective solution with an abundant supply chain, but with substantial limitations for the integration of photonic functions. Here we introduce photonics into bulk silicon complementary metal-oxide-semiconductor (CMOS) chips using a layer of polycrystalline silicon deposited on silicon oxide (glass) islands fabricated alongside transistors. We use this single deposited layer to realize optical waveguides and resonators, high-speed optical modulators and sensitive avalanche photodetectors. We integrated this photonic platform with a 65-nanometre-transistor bulk CMOS process technology inside a 300-millimetre-diameter-wafer microelectronics foundry. We then implemented integrated high-speed optical transceivers in this platform that operate at ten gigabits per second, composed of millions of transistors, and arrayed on a single optical bus for wavelength division multiplexing, to address the demand for high-bandwidth optical interconnects in data centres and high-performance computing 3,4 . By decoupling the formation of photonic devices from that of transistors, this integration approach can achieve many of the goals of multi-chip solutions 5 , but with the performance, complexity and scalability of 'systems on a chip' 1,6-8 . As transistors smaller than ten nanometres across become commercially available 9 , and as new nanotechnologies emerge 10,11 , this approach could provide a way to integrate photonics with state-of-the-art nanoelectronics.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Inglese, Alessandro, E-mail: alessandro.inglese@aalto.fi; Savin, Hele; Lindroos, Jeanette

Copper is a harmful metal impurity that significantly impacts the performance of silicon-based devices if present in active regions. In this contribution, we propose a fast method consisting of simultaneous illumination and annealing for the detection of copper contamination in p-type silicon. Our results show that, within minutes, such method is capable of producing a significant reduction of the minority carrier lifetime. A spatial distribution map of copper contamination can then be obtained through the lifetime values measured before and after degradation. In order to separate the effect of the light-activated copper defects from the other metastable complexes in lowmore » resistivity Cz-silicon, we carried out a dark anneal at 200 °C, which is known to fully recover the boron-oxygen defect. Similar to the boron-oxygen behavior, we show that the dark anneal also recovers the copper defects. However, the recovery is only partial and it can be used to identify the possible presence of copper contamination.« less

Broadband electromagnetic dipole scattering by coupled multiple nanospheres

NASA Astrophysics Data System (ADS)

Jing, Xufeng; Ye, Qiufeng; Hong, Zhi; Zhu, Dongshuo; Shi, Guohua

2017-11-01

With the development of nanotechnology, the ability to manipulate light at the nanoscale is critical to future optical functional devices. The use of high refractive index dielectric single silicon nanoparticle can achieve electromagnetic dipole resonant properties. Compared with single nanosphere, the use of dimer and trimer introduces an additional dimension (gap size) for improving the performance of dielectric optical devices through the coupling between closely connected silicon nanospheres. When changing the gap size between the nanospheres, the interaction between the particles can be from weak to strong. Compared with single nanospheres, dimerized or trimeric nanospheres exhibit more pronounced broadband scattering properties. In addition, by introducing more complex interaction, the trimericed silicon nanospheres exhibit a more significant increase in bandwidth than expected. In addition, the presence of the substrate will also contribute to the increase in the bandwidth of the nanospheres. The broadband response in dielectric nanostructures can be effectively applied to broadband applications such as dielectric nanoantennas or solar cells.

Multipurpose silicon photonics signal processor core.

PubMed

Pérez, Daniel; Gasulla, Ivana; Crudgington, Lee; Thomson, David J; Khokhar, Ali Z; Li, Ke; Cao, Wei; Mashanovich, Goran Z; Capmany, José

2017-09-21

Integrated photonics changes the scaling laws of information and communication systems offering architectural choices that combine photonics with electronics to optimize performance, power, footprint, and cost. Application-specific photonic integrated circuits, where particular circuits/chips are designed to optimally perform particular functionalities, require a considerable number of design and fabrication iterations leading to long development times. A different approach inspired by electronic Field Programmable Gate Arrays is the programmable photonic processor, where a common hardware implemented by a two-dimensional photonic waveguide mesh realizes different functionalities through programming. Here, we report the demonstration of such reconfigurable waveguide mesh in silicon. We demonstrate over 20 different functionalities with a simple seven hexagonal cell structure, which can be applied to different fields including communications, chemical and biomedical sensing, signal processing, multiprocessor networks, and quantum information systems. Our work is an important step toward this paradigm.Integrated optical circuits today are typically designed for a few special functionalities and require complex design and development procedures. Here, the authors demonstrate a reconfigurable but simple silicon waveguide mesh with different functionalities.

Rapid Prototyping Technology for Manufacturing GTE Turbine Blades

NASA Astrophysics Data System (ADS)

Balyakin, A. V.; Dobryshkina, E. M.; Vdovin, R. A.; Alekseev, V. P.

2018-03-01

The conventional approach to manufacturing turbine blades by investment casting is expensive and time-consuming, as it takes a lot of time to make geometrically precise and complex wax patterns. Turbine blade manufacturing in pilot production can be sped up by accelerating the casting process while keeping the geometric precision of the final product. This paper compares the rapid prototyping method (casting the wax pattern composition into elastic silicone molds) to the conventional technology. Analysis of the size precision of blade casts shows that silicon-mold casting features sufficient geometric precision. Thus, this method for making wax patterns can be a cost-efficient solution for small-batch or pilot production of turbine blades for gas-turbine units (GTU) and gas-turbine engines (GTE). The paper demonstrates how additive technology and thermographic analysis can speed up the cooling of wax patterns in silicone molds. This is possible at an optimal temperature and solidification time, which make the process more cost-efficient while keeping the geometric quality of the final product.

Method for preparing configured silicon carbide whisker-reinforced alumina ceramic articles

DOEpatents

Tiegs, Terry N.

1987-01-01

A ceramic article of alumina reinforced with silicon carbide whiskers suitable for the fabrication into articles of complex geometry are provided by pressureless sintering and hot isostatic pressing steps. In accordance with the method of the invention a mixture of 5 to 10 vol. % silicon carbide whiskers 0.5 to 5 wt. % of a sintering aid such as yttria and the balance alumina powders is ball-milled and pressureless sintered in the desired configuration in the desired configuration an inert atmosphere at a temperature of about 1800.degree. C. to provide a self-supporting configured composite of a density of at least about 94% theoretical density. The composite is then hot isostatically pressed at a temperature and pressure adequate to provide configured articles of at least about 98% of theoretical density which is sufficient to provide the article with sufficient strength and fracture toughness for use in most structural applications such as gas turbine blades, cylinders, and other components of advanced heat engines.

Boron deactivation in heavily boron-doped Czochralski silicon during rapid thermal anneal: Atomic level understanding

NASA Astrophysics Data System (ADS)

Gao, Chao; Lu, Yunhao; Dong, Peng; Yi, Jun; Ma, Xiangyang; Yang, Deren

2014-01-01

The changes in hole concentration of heavily boron (B)-doped Czochralski silicon subjected to high temperature rapid thermal anneal (RTA) and following conventional furnace anneal (CFA) have been investigated. It is found that decrease in hole concentration, namely, B deactivation, is observed starting from 1050 °C and increases with RTA temperature. The following CFA at 300-500 °C leads to further B deactivation, while that at 600-800 °C results in B reactivation. It is supposed that the interaction between B atoms and silicon interstitials (I) thus forming BI pairs leads to the B deactivation during the high temperature RTA, and, moreover, the formation of extended B2I complexes results in further B deactivation in the following CFA at 300-500 °C. On the contrary, the dissociation of BI pairs during the following CFA at 600-800 °C enables the B reactivation. Importantly, the first-principles calculation results can soundly account for the above-mentioned supposition.

Influence of Silicon-Containing Additives on Concrete Waterproofness Property

NASA Astrophysics Data System (ADS)

Butakova, M. D.; Saribekyan, S. S.; Mikhaylov, A. V.

2017-11-01

The article studies the influence of silicon-containing additives on the property of the water resistance of concrete samples. It provides a review of the literature on common approaches and technologies improving concrete waterproofness and reinforced concrete structures. Normal hardening samples were obtained on the basis of concretes containing microsilica, aerosil or ash, or the combinations thereof. This research is aimed at the study of the complex modifier effect r on the basis of metakaolin, superplasticizer and silicon containing additives on the property of concrete water resistance. The need to use a superplasticizer to reduce the water-cement ratio and metakaolin as a hardening accelerator along with the set of strength is substantiated. This article describes a part of the results of the experiment conducted to find alternative options for colmatizing expensive additives used in the concreting foundations of private house-building. The implementation of the scientific work will not only clarify this area but will also broaden the knowledge of such additive as aerosol.

Effect Of Chromium Underlayer On The Properties Of Nano-Crystalline Diamond Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garratt, Elias; AlFaify, Salem; Yoshitake, T.

2013-01-11

This paper investigated the effect of chromium underlayer on the structure, microstructure and composition of the nano-crystalline diamond films. Nano-crystalline diamond thin films were deposited at high temperature in microwave-induced plasma diluted with nitrogen, on silicon substrate with a thin film of chromium as an underlayer. The composition, structure and microstructure of the deposited layers were analyzed using non-Rutherford Backscattering Spectrometry, Raman Spectroscopy, Near-Edge X-Ray Absorption Fine Structure, X-ray Diffraction and Atomic Force Microscopy. Nanoindentation studies showed that the films deposited on chromium underlayer have higher hardness values compared to those deposited on silicon without an underlayer. Diamond and graphiticmore » phases of the films evaluated by x-ray and optical spectroscopic analysis determined consistency between sp2 and sp3 phases of carbon in chromium sample to that of diamond grown on silicon. Diffusion of chromium was observed using ion beam analysis which was correlated with the formation of chromium complexes by x-ray diffraction.« less

Graphene-silicon phase modulators with gigahertz bandwidth

NASA Astrophysics Data System (ADS)

Sorianello, V.; Midrio, M.; Contestabile, G.; Asselberghs, I.; Van Campenhout, J.; Huyghebaert, C.; Goykhman, I.; Ott, A. K.; Ferrari, A. C.; Romagnoli, M.

2018-01-01

The modulator is a key component in optical communications. Several graphene-based amplitude modulators have been reported based on electro-absorption. However, graphene phase modulators (GPMs) are necessary for functions such as applying complex modulation formats or making switches or phased arrays. Here, we present a 10 Gb s-1 GPM integrated in a Mach-Zehnder interferometer configuration. This is a compact device based on a graphene-insulator-silicon capacitor, with a phase-shifter length of 300 μm and extinction ratio of 35 dB. The GPM has a modulation efficiency of 0.28 V cm at 1,550 nm. It has 5 GHz electro-optical bandwidth and operates at 10 Gb s-1 with 2 V peak-to-peak driving voltage in a push-pull configuration for binary transmission of a non-return-to-zero data stream over 50 km of single-mode fibre. This device is the key building block for graphene-based integrated photonics, enabling compact and energy-efficient hybrid graphene-silicon modulators for telecom, datacom and other applications.

Ultrasonic Guided-Wave Scan System Used to Characterize Microstructure and Defects in Ceramic Composites

NASA Technical Reports Server (NTRS)

Roth, Don J.; Cosgriff, Laura M.; Martin, Richard E.; Verrilli, Michael J.; Bhatt, Ramakrishna T.

2004-01-01

Ceramic matrix composites (CMCs) are being developed for advanced aerospace propulsion applications to save weight, improve reuse capability, and increase performance. However, mechanical and environmental loads applied to CMCs can cause discrete flaws and distributed microdamage, significantly reducing desirable physical properties. Such microdamage includes fiber/matrix debonding (interface failure), matrix microcracking, fiber fracture and buckling, oxidation, and second phase formation. A recent study (ref. 1) of the durability of a C/SiC CMC discussed the requirement for improved nondestructive evaluation (NDE) methods for monitoring degradation in these materials. Distributed microdamage in CMCs has proven difficult to characterize nondestructively because of the complex microstructure and macrostructure of these materials. This year, an ultrasonic guided-wave scan system developed at the NASA Glenn Research Center was used to characterize various microstructural and flaw conditions in SiC/SiC (silicon carbide fiber in silicon carbide matrix) and C/SiC (carbon fiber in silicon carbide matrix) CMC samples.

Effect of chromium underlayer on the properties of nano-crystalline diamond films

NASA Astrophysics Data System (ADS)

Garratt, E.; AlFaify, S.; Yoshitake, T.; Katamune, Y.; Bowden, M.; Nandasiri, M.; Ghantasala, M.; Mancini, D. C.; Thevuthasan, S.; Kayani, A.

2013-01-01

This paper investigated the effect of chromium underlayer on the structure, microstructure, and composition of the nano-crystalline diamond films. Nano-crystalline diamond thin films were deposited at high temperature in microwave-induced plasma diluted with nitrogen, on single crystal silicon substrate with a thin film of chromium as an underlayer. Characterization of the film was implemented using non-Rutherford backscattering spectrometry, Raman spectroscopy, near-edge x-ray absorption fine structure, x-ray diffraction, and atomic force microscopy. Nanoindentation studies showed that the films deposited on chromium underlayer have higher hardness values compared to those deposited on silicon without an underlayer. Diamond and graphitic phases of the films evaluated by x-ray and optical spectroscopic analyses determined consistency between the sp2 and sp3 phases of carbon in chromium sample to that of diamond grown on silicon. Diffusion of chromium was observed using ion beam analysis which was correlated with the formation of chromium complexes by x-ray diffraction.

Oxidation/vaporization of silicide coated columbium base alloys

NASA Technical Reports Server (NTRS)

Kohl, F. J.; Stearns, C. A.

1971-01-01

Mass spectrometric and target collection experiments were made at 1600 K to elucidate the mode of oxidative vaporization of two columbium alloys, fused-slurry-coated with a complex silicide former (Si-20Cr-Fe). At oxygen pressures up to 0.0005 torr the major vapor component detected by mass spectrometry for oxidized samples was gaseous silicon monoxide. Analysis of condensates collected at oxygen pressures of 0.1, 1.0 and 10 torr revealed that chromium-, silicon-, iron- and tungsten- containing species were the major products of vaporization. Equilibrium thermochemical diagrams were constructed for the metal-oxygen system corresponding to each constituent metal in both the coating and base alloy. The major vaporizing species are expected to be the gaseous oxides of chromium, silicon, iron and tungsten. Plots of vapor phase composition and maximum vaporization rate versus oxygen pressure were calculated for each coating constituent. The major contribution to weight loss by vaporization at oxygen pressures above 1 torr was shown to be the chromium-containing species.

Attachment chemistry of aromatic compounds on a Silicon(100) surface

NASA Astrophysics Data System (ADS)

Henriksson, Anders; Nishiori, Daiki; Maeda, Hiroaki; Miyachi, Mariko; Yamanoi, Yoshinori; Nishihara, Hiroshi

2018-03-01

A mild method was developed for the chemical attachment of aromatic compounds directly onto a hydrogen-terminated Si(100) (H-Si(100)) surface. In the presence of palladium catalyst and base, 4-iodophenylferrocene and a π-conjugated iron complex were attached to H-Si(100) electrodes and hydrogen-terminated silicon nanowires (H-SiNWs), both of which have predominant dihydride species on their surfaces. The reactions were conducted in 1,4-dioxane at 100 °C and the immobilization of both 4-ferrocenylphenyl group and π-conjugated molecular wires were confirmed and quantified by XPS and electrochemical measurements. We reported densely packed monolayer whose surface coverage (Γ), estimated from the electrochemical measurements are in analogue to similar monolayers prepared via thermal or light induced hydrosilylation reactions with alkenes or alkynes. The increase in electrochemical response observed on nanostructured silicon surfaces corresponds well to the increase in surface area, those strongly indicating that this method may be applied for the functionalization of electrodes with a variety of surface topographies.

A single active nanoelectromechanical tuning fork front-end radio-frequency receiver

NASA Astrophysics Data System (ADS)

Bartsch, Sebastian T.; Rusu, A.; Ionescu, Adrian M.

2012-06-01

Nanoelectromechanical systems (NEMS) offer the potential to revolutionize fundamental methods employed for signal processing in today’s telecommunication systems, owing to their spectral purity and the prospect of integration with existing technology. In this work we present a novel, front-end receiver topology based on a single device silicon nanoelectromechanical mixer-filter. The operation is demonstrated by using the signal amplification in a field effect transistor (FET) merged into a tuning fork resonator. The combination of both a transistor and a mechanical element into a hybrid unit enables on-chip functionality and performance previously unachievable in silicon. Signal mixing, filtering and demodulation are experimentally demonstrated at very high frequencies ( > 100 MHz), maintaining a high quality factor of Q = 800 and stable operation at near ambient pressure (0.1 atm) and room temperature (T = 300 K). The results show that, ultimately miniaturized, silicon NEMS can be utilized to realize multi-band, single-chip receiver systems based on NEMS mixer-filter arrays with reduced system complexity and power consumption.

User's Manual for PCSMS (Parallel Complex Sparse Matrix Solver). Version 1.

NASA Technical Reports Server (NTRS)

Reddy, C. J.

2000-01-01

PCSMS (Parallel Complex Sparse Matrix Solver) is a computer code written to make use of the existing real sparse direct solvers to solve complex, sparse matrix linear equations. PCSMS converts complex matrices into real matrices and use real, sparse direct matrix solvers to factor and solve the real matrices. The solution vector is reconverted to complex numbers. Though, this utility is written for Silicon Graphics (SGI) real sparse matrix solution routines, it is general in nature and can be easily modified to work with any real sparse matrix solver. The User's Manual is written to make the user acquainted with the installation and operation of the code. Driver routines are given to aid the users to integrate PCSMS routines in their own codes.

Mechanical failure modes of chronically implanted planar silicon-based neural probes for laminar recording

PubMed Central

Kozai, Takashi D. Y.; Catt, Kasey; Li, Xia; Gugel, Zhannetta V.; Olafsson, Valur T.; Vazquez, Alberto L.; Cui, X. Tracy

2014-01-01

Penetrating intracortical electrode arrays that record brain activity longitudinally are powerful tools for basic neuroscience research and emerging clinical applications. However, regardless of the technology used, signals recorded by these electrodes degrade over time. The failure mechanisms of these electrodes are understood to be a complex combination of the biological reactive tissue response and material failure of the device over time. While mechanical mismatch between the brain tissue and implanted neural electrodes have been studied as a source of chronic inflammation and performance degradation, the electrode failure caused by mechanical mismatch between different material properties and different structural components within a device have remained poorly characterized. Using Finite Element Model (FEM) we simulate the mechanical strain on a planar silicon electrode. The results presented here demonstrate that mechanical mismatch between iridium and silicon leads to concentrated strain along the border of the two materials. This strain is further focused on small protrusions such as the electrical traces in planar silicon electrodes. These findings are confirmed with chronic in vivo data (133–189 days) in mice by correlating a combination of single-unit electrophysiology, evoked multi-unit recordings, electrochemical impedance spectroscopy, and scanning electron microscopy from traces and electrode sites with our modeling data. Several modes of mechanical failure of chronically implanted planar silicon electrodes are found that result in degradation and/or loss of recording. These findings highlight the importance of strains and material properties of various subcomponents within an electrode array. PMID:25453935

Exploration of maximum count rate capabilities for large-area photon counting arrays based on polycrystalline silicon thin-film transistors

NASA Astrophysics Data System (ADS)

Liang, Albert K.; Koniczek, Martin; Antonuk, Larry E.; El-Mohri, Youcef; Zhao, Qihua

2016-03-01

Pixelated photon counting detectors with energy discrimination capabilities are of increasing clinical interest for x-ray imaging. Such detectors, presently in clinical use for mammography and under development for breast tomosynthesis and spectral CT, usually employ in-pixel circuits based on crystalline silicon - a semiconductor material that is generally not well-suited for economic manufacture of large-area devices. One interesting alternative semiconductor is polycrystalline silicon (poly-Si), a thin-film technology capable of creating very large-area, monolithic devices. Similar to crystalline silicon, poly-Si allows implementation of the type of fast, complex, in-pixel circuitry required for photon counting - operating at processing speeds that are not possible with amorphous silicon (the material currently used for large-area, active matrix, flat-panel imagers). The pixel circuits of two-dimensional photon counting arrays are generally comprised of four stages: amplifier, comparator, clock generator and counter. The analog front-end (in particular, the amplifier) strongly influences performance and is therefore of interest to study. In this paper, the relationship between incident and output count rate of the analog front-end is explored under diagnostic imaging conditions for a promising poly-Si based design. The input to the amplifier is modeled in the time domain assuming a realistic input x-ray spectrum. Simulations of circuits based on poly-Si thin-film transistors are used to determine the resulting output count rate as a function of input count rate, energy discrimination threshold and operating conditions.

Polishing of silicon based advanced ceramics

NASA Astrophysics Data System (ADS)

Klocke, Fritz; Dambon, Olaf; Zunke, Richard; Waechter, D.

2009-05-01

Silicon based advanced ceramics show advantages in comparison to other materials due to their extreme hardness, wear and creep resistance, low density and low coefficient of thermal expansion. As a matter of course, machining requires high efforts. In order to reach demanded low roughness for optical or tribological applications a defect free surface is indispensable. In this paper, polishing of silicon nitride and silicon carbide is investigated. The objective is to elaborate scientific understanding of the process interactions. Based on this knowledge, the optimization of removal rate, surface quality and form accuracy can be realized. For this purpose, fundamental investigations of polishing silicon based ceramics are undertaken and evaluated. Former scientific publications discuss removal mechanisms and wear behavior, but the scientific insight is mainly based on investigations in grinding and lapping. The removal mechanisms in polishing are not fully understood due to complexity of interactions. The role of, e.g., process parameters, slurry and abrasives, and their influence on the output parameters is still uncertain. Extensive technological investigations demonstrate the influence of the polishing system and the machining parameters on the stability and the reproducibility. It is shown that the interactions between the advanced ceramics and the polishing systems is of great relevance. Depending on the kind of slurry and polishing agent the material removal mechanisms differ. The observed effects can be explained by dominating mechanical or chemo-mechanical removal mechanisms. Therefore, hypotheses to state adequate explanations are presented and validated by advanced metrology devices, such as SEM, AFM and TEM.

Effect of nanoscale surface roughness on the bonding energy of direct-bonded silicon wafers

NASA Astrophysics Data System (ADS)

Miki, N.; Spearing, S. M.

2003-11-01

Direct wafer bonding of silicon wafers is a promising technology for manufacturing three-dimensional complex microelectromechanical systems as well as silicon-on-insulator substrates. Previous work has reported that the bond quality declines with increasing surface roughness, however, this relationship has not been quantified. This article explicitly correlates the bond quality, which is quantified by the apparent bonding energy, and the surface morphology via the bearing ratio, which describes the area of surface lying above a given depth. The apparent bonding energy is considered to be proportional to the real area of contact. The effective area of contact is defined as the area sufficiently close to contribute to the attractive force between the two bonding wafers. Experiments were conducted with silicon wafers whose surfaces were roughened by a buffered oxide etch solution (BOE, HF:NH4F=1:7) and/or a potassium hydroxide solution. The surface roughness was measured by atomic force microscopy. The wafers were direct bonded to polished "monitor" wafers following a standard RCA cleaning and the resulting bonding energy was measured by the crack-opening method. The experimental results revealed a clear correlation between the bonding energy and the bearing ratio. A bearing depth of ˜1.4 nm was found to be appropriate for the characterization of direct-bonded silicon at room temperature, which is consistent with the thickness of the water layer at the interface responsible for the hydrogen bonds that link the mating wafers.

Bifurcation of synchronous oscillations into torus in a system of two reciprocally inhibitory silicon neurons: experimental observation and modeling.

PubMed

Bondarenko, Vladimir E; Cymbalyuk, Gennady S; Patel, Girish; Deweerth, Stephen P; Calabrese, Ronald L

2004-12-01

Oscillatory activity in the central nervous system is associated with various functions, like motor control, memory formation, binding, and attention. Quasiperiodic oscillations are rarely discussed in the neurophysiological literature yet they may play a role in the nervous system both during normal function and disease. Here we use a physical system and a model to explore scenarios for how quasiperiodic oscillations might arise in neuronal networks. An oscillatory system of two mutually inhibitory neuronal units is a ubiquitous network module found in nervous systems and is called a half-center oscillator. Previously we created a half-center oscillator of two identical oscillatory silicon (analog Very Large Scale Integration) neurons and developed a mathematical model describing its dynamics. In the mathematical model, we have shown that an in-phase limit cycle becomes unstable through a subcritical torus bifurcation. However, the existence of this torus bifurcation in experimental silicon two-neuron system was not rigorously demonstrated or investigated. Here we demonstrate the torus predicted by the model for the silicon implementation of a half-center oscillator using complex time series analysis, including bifurcation diagrams, mapping techniques, correlation functions, amplitude spectra, and correlation dimensions, and we investigate how the properties of the quasiperiodic oscillations depend on the strengths of coupling between the silicon neurons. The potential advantages and disadvantages of quasiperiodic oscillations (torus) for biological neural systems and artificial neural networks are discussed.

Thin film CdTe based neutron detectors with high thermal neutron efficiency and gamma rejection for security applications

NASA Astrophysics Data System (ADS)

Smith, L.; Murphy, J. W.; Kim, J.; Rozhdestvenskyy, S.; Mejia, I.; Park, H.; Allee, D. R.; Quevedo-Lopez, M.; Gnade, B.

2016-12-01

Solid-state neutron detectors offer an alternative to 3He based detectors, but suffer from limited neutron efficiencies that make their use in security applications impractical. Solid-state neutron detectors based on single crystal silicon also have relatively high gamma-ray efficiencies that lead to false positives. Thin film polycrystalline CdTe based detectors require less complex processing with significantly lower gamma-ray efficiencies. Advanced geometries can also be implemented to achieve high thermal neutron efficiencies competitive with silicon based technology. This study evaluates these strategies by simulation and experimentation and demonstrates an approach to achieve >10% intrinsic efficiency with <10-6 gamma-ray efficiency.

Two different carbon-hydrogen complexes in silicon with closely spaced energy levels

NASA Astrophysics Data System (ADS)

Stübner, R.; Kolkovsky, Vl.; Weber, J.

2015-08-01

An acceptor and a single donor state of carbon-hydrogen defects (CHA and CHB) are observed by Laplace deep level transient spectroscopy at 90 K. CHA appears directly after hydrogenation by wet chemical etching or hydrogen plasma treatment, whereas CHB can be observed only after a successive annealing under reverse bias at about 320 K. The activation enthalpies of these states are 0.16 eV for CHA and 0.14 eV for CHB. Our results reconcile previous controversial experimental results. We attribute CHA to the configuration where substitutional carbon binds a hydrogen atom on a bond centered position between carbon and the neighboring silicon and CHB to another carbon-hydrogen defect.

A fast-neutron detection detector based on fission material and large sensitive 4H silicon carbide Schottky diode detector

NASA Astrophysics Data System (ADS)

Liu, Linyue; Liu, Jinliang; Zhang, Jianfu; Chen, Liang; Zhang, Xianpeng; Zhang, Zhongbing; Ruan, Jinlu; Jin, Peng; Bai, Song; Ouyang, Xiaoping

2017-12-01

Silicon carbide radiation detectors are attractive in the measurement of the total numbers of pulsed fast neutrons emitted from nuclear fusion and fission devices because of high neutron-gamma discrimination and good radiation resistance. A fast-neutron detection system was developed based on a large-area 4H-SiC Schottky diode detector and a 235U fission target. Excellent pulse-height spectra of fission fragments induced by mono-energy deuterium-tritium (D-T) fusion neutrons and continuous energy fission neutrons were obtained. The detector is proven to be a good candidate for pulsed fast neutron detection in a complex radiation field.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ulin, V. P.; Ulin, N. V.; Soldatenkov, F. Yu., E-mail: f.soldatenkov@mail.ioffe.ru

The interaction of heavily doped p- and n-type Si crystals with hydrofluoric acid in the dark with and without contact with metals having greatly differing work functions (Ag and Pd) is studied. The dependences of the dissolution rates of Si crystals in HF solutions that contain oxidizing agents with different redox potentials (FeCl{sub 3}, V{sub 2}O{sub 5} and CrO{sub 3}) on the type and level of silicon doping are determined. Analysis of the experimental data suggests that valence-band holes in silicon are not directly involved in the anodic reactions of silicon oxidation and dissolution and their generation in crystals doesmore » not limit the rate of these processes. It is also shown that the character and rate of the chemical process leading to silicon dissolution in HF-containing electrolytes are determined by the interfacial potential attained at the semiconductor–electrolyte interface. The mechanism of electrochemical pore formation in silicon crystals is discussed in terms of selfconsistent cooperative reactions of nucleophilic substitution between chemisorbed fluorine anions and coordination- saturated silicon atoms in the crystal subsurface layer. A specific feature of these reactions for silicon crystals is that vacant nonbonding d{sup 2}sp{sup 3} orbitals of Si atoms, associated with sixfold degenerate states corresponding to the Δ valley of the conduction band, are involved in the formation of intermediate complexes. According to the suggested model, the pore-formation process spontaneously develops in local regions of the interface under the action of the interfacial potential in the adsorption layer and occurs as a result of the detachment of (SiF{sub 2}){sub n} polymer chains from the crystal. Just this process leads to the preferential propagation of pores along the <100> crystallographic directions. The thermodynamic aspects of pore nucleation and the effect of the potential drop across the interface, conduction type, and free-carrier concentration in the crystal on the pore size and structure are discussed. The concepts developed in the study can consistently account for experimental facts characterizing the etching of silicon crystals with various electrical parameters under various conditions providing the anodic polarization of crystals in HF-containing solutions.« less

Story Games: Marrying Silicon, Celluloid, and CD-ROM.

ERIC Educational Resources Information Center

Gussin, Lawrence

1994-01-01

Reports on themes emphasized at the April 1994 Computer Game Developers Conference held in Santa Clara (California), including the exploding CD-ROM marketplace and the potential and challenge of using CD-ROM's multimedia capacity to build cinema-quality stories and characters into computer games. Strategies for introducing more complex plots are…

Streaming Media

ERIC Educational Resources Information Center

Pulley, John

2009-01-01

At a time when the evolutionary pace of new media resembles the real-time mutation of certain microorganisms, the age-old question of how best to connect with constituents can seem impossibly complex--even for an elite institution plugged into the motherboard of Silicon Valley. Identifying the most effective vehicle for reaching a particular…

Photochemistry of Cobalt Carbonyl Complexes having a Cobalt-Silicon Bond and its Importance in Activation of Catalysis.

DTIC Science & Technology

1980-08-22

CLASS. (*I *Soi rapeoro 7_ UNCLASSIFIED / ...--J I.. ECk ASSI FICATION/ DOWNGRADING 16. DISTRIBUTION STATEMENT (of thnis Asport) Approved for public...Defense Technical Information Center Attn: Dr. S. Yamamoto, Marine Building 5, Cameron Station Sciences Division Alexandria, Virginia 22314 12 San Diego

Improved silicon carbide for advanced heat engines

NASA Technical Reports Server (NTRS)

Whalen, Thomas J.

1988-01-01

This is the third annual technical report for the program entitled, Improved Silicon Carbide for Advanced Heat Engines, for the period February 16, 1987 to February 15, 1988. The objective of the original program was the development of high strength, high reliability silicon carbide parts with complex shapes suitable for use in advanced heat engines. Injection molding is the forming method selected for the program because it is capable of forming complex parts adaptable for mass production on an economically sound basis. The goals of the revised program are to reach a Weibull characteristic strength of 550 MPa (80 ksi) and a Weibull modulus of 16 for bars tested in 4-point loading. Two tasks are discussed: Task 1 which involves materials and process improvements, and Task 2 which is a MOR bar matrix to improve strength and reliability. Many statistically designed experiments were completed under task 1 which improved the composition of the batches, the mixing of the powders, the sinter and anneal cycles. The best results were obtained by an attritor mixing process which yielded strengths in excess of 550 MPa (80 ksi) and an individual Weibull modulus of 16.8 for a 9-sample group. Strengths measured at 1200 and 1400 C were equal to the room temperature strength. Annealing of machined test bars significantly improved the strength. Molding yields were measured and flaw distributions were observed to follow a Poisson process. The second iteration of the Task 2 matrix experiment is described.

On-site customization of silicone stents: towards optimal palliation of complex airway conditions.

PubMed

Breen, David P; Dutau, Hervé

2009-01-01

Stents may be indicated as treatment of benign and malignant conditions of the central airways. Occasionally, aberrant and/or distorted airways secondary to therapy or surgery may preclude the use of commercially manufactured stents. The customization of stents is well described for nonpulmonary diseases, but to date there are only limited data in the literature on prosthesis customization for airway disease. To review all the different techniques and indications of on-site silicone stent customizations and their related complications. A retrospective study was undertaken to identify all patients who underwent treatment with a silicone stent which was customized on site by the physician. The study included subjects treated during an 8-year period. Forty-nine on-site customizations were performed in 43 patients (34 males, mean age 63 +/- 5.2 years). Stent customization was performed in 5.4% of the cases. Stent customization was performed for malignant and benign disease in 35 (81.3%) and 8 (18.7%) cases, respectively. In all cases, the stent deployed successfully and performed well while in situ. Stent manipulation did not increase complications. Customization of airway stents by the physician can lead to successful stenting of difficult airway lesions with a good short-term safety profile. Standard commercially available stents may have resulted in suboptimal management of complex airway pathologies. A prospective study is warranted to further investigate the safety profile and complications associated with stent customization. Copyright 2009 S. Karger AG, Basel.

Induction of anchorage-independent growth in primary human cells exposed to protons or HZE ions separately or in dual exposures.

PubMed

Sutherland, B M; Cuomo, N C; Bennett, P V

2005-10-01

Travelers on space missions will be exposed to a complex radiation environment that includes protons and heavy charged particles. Since protons are present at much higher levels than are heavy ions, the most likely scenario for cellular radiation exposure will be proton exposure followed by a hit by a heavy ion. Although the effects of individual ion species on human cells are being investigated extensively, little is known about the effects of exposure to both radiation types. One useful measure of mammalian cell damage is induction of the ability to grow in a semi-solid agar medium highly inhibitory to the growth of normal human cells, termed neoplastic transformation. Using primary human cells, we evaluated induction of soft-agar growth and survival of cells exposed to protons only or to heavy charged particles (600 MeV/nucleon silicon) only as well as of cells exposed to protons followed after a 4-day interval by silicon ions. Both ions alone efficiently transformed the human cells to anchorage-independent growth. Initial experiments indicate that the dose responses for neoplastic transformation of cells exposed to protons and then after 4 days to silicon ions appear similar to that of cells exposed to silicon ions alone.

Doping porous silicon with erbium: pores filling as a method to limit the Er-clustering effects and increasing its light emission.

PubMed

Mula, Guido; Printemps, Tony; Licitra, Christophe; Sogne, Elisa; D'Acapito, Francesco; Gambacorti, Narciso; Sestu, Nicola; Saba, Michele; Pinna, Elisa; Chiriu, Daniele; Ricci, Pier Carlo; Casu, Alberto; Quochi, Francesco; Mura, Andrea; Bongiovanni, Giovanni; Falqui, Andrea

2017-07-20

Er clustering plays a major role in hindering sufficient optical gain in Er-doped Si materials. For porous Si, the long-standing failure to govern the clustering has been attributed to insufficient knowledge of the several, concomitant and complex processes occurring during the electrochemical Er-doping. We propose here an alternative road to solve the issue: instead of looking for an equilibrium between Er content and light emission using 1-2% Er, we propose to significantly increase the electrochemical doping level to reach the filling the porous silicon pores with luminescent Er-rich material. To better understand the intricate and superposing phenomena of this process, we exploit an original approach based on needle electron tomography, EXAFS and photoluminescence. Needle electron tomography surprisingly shows a heterogeneous distribution of Er content in the silicon thin pores that until now couldn't be revealed by the sole use of scanning electron microscopy compositional mapping. Besides, while showing that pore filling leads to enhanced photoluminescence emission, we demonstrate that the latter is originated from both erbium oxide and silicate. These results give a much deeper understanding of the photoluminescence origin down to nanoscale and could lead to novel approaches focused on noteworthy enhancement of Er-related photoluminescence in porous silicon.

A mock heart engineered with helical aramid fibers for in vitro cardiovascular device testing.

PubMed

Jansen-Park, So-Hyun; Hsu, Po-Lin; Müller, Indra; Steinseifer, Ulrich; Abel, Dirk; Autschbach, Rüdiger; Rossaint, Rolf; Schmitz-Rode, Thomas

2017-04-01

Mock heart circulation loops (MHCLs) serve as in-vitro platforms to investigate the physiological interaction between circulatory systems and cardiovascular devices. A mock heart (MH) engineered with silicone walls and helical aramid fibers, to mimic the complex contraction of a natural heart, has been developed to advance the MHCL previously developed in our group. A mock aorta with an anatomical shape enables the evaluation of a cannulation method for ventricular assist devices (VADs) and investigation of the usage of clinical measurement systems like pressure-volume catheters. Ventricle and aorta molds were produced based on MRI data and cast with silicone. Aramid fibers were layered in the silicone ventricle to reproduce ventricle torsion. A rotating hollow shaft was connected to the apex enabling the rotation of the MH and the connection of a VAD. Silicone wall thickness, aramid fiber angle and fiber pitch were varied to generate different MH models. All MH models were placed in a tank filled with variable amounts of water and air simulating the compliance. In this work, physiological ventricular torsion angles (15°-26°) and physiological pressure-volume loops were achieved. This MHCL can serve as a comprehensive testing platform for cardiovascular devices, such as artificial heart valves and cannulation of VADs.

A Highly Tunable Silicone-Based Magnetic Elastomer with Nanoscale Homogeneity

PubMed Central

Evans, Benjamin A.; Fiser, Briana L.; Prins, Willem J.; Rapp, Daniel J.; Shields, Adam R.; Glass, Daniel R.; Superfine, R.

2011-01-01

Magnetic elastomers have been widely pursued for sensing and actuation applications. Silicone-based magnetic elastomers have a number of advantages over other materials such as hydrogels, but aggregation of magnetic nanoparticles within silicones is difficult to prevent. Aggregation inherently limits the minimum size of fabricated structures and leads to non-uniform response from structure to structure. We have developed a novel material which is a complex of a silicone polymer (polydimethylsiloxane-co-aminopropylmethylsiloxane) adsorbed onto the surface of magnetite (γ-Fe203) nanoparticles 7–10 nm in diameter. The material is homogenous at very small length scales (< 100 nm) and can be crosslinked to form a flexible, magnetic material which is ideally suited for the fabrication of micro- to nanoscale magnetic actuators. The loading fraction of magnetic nanoparticles in the composite can be varied smoothly from 0 – 50% wt. without loss of homogeneity, providing a simple mechanism for tuning actuator response. We evaluate the material properties of the composite across a range of nanoparticle loading, and demonstrate a magnetic-field-induced increase in compressive modulus as high as 300%. Furthermore, we implement a strategy for predicting the optimal nanoparticle loading for magnetic actuation applications, and show that our predictions correlate well with experimental findings. PMID:22184482

A Highly Tunable Silicone-Based Magnetic Elastomer with Nanoscale Homogeneity.

PubMed

Evans, Benjamin A; Fiser, Briana L; Prins, Willem J; Rapp, Daniel J; Shields, Adam R; Glass, Daniel R; Superfine, R

2012-02-01

Magnetic elastomers have been widely pursued for sensing and actuation applications. Silicone-based magnetic elastomers have a number of advantages over other materials such as hydrogels, but aggregation of magnetic nanoparticles within silicones is difficult to prevent. Aggregation inherently limits the minimum size of fabricated structures and leads to non-uniform response from structure to structure. We have developed a novel material which is a complex of a silicone polymer (polydimethylsiloxane-co-aminopropylmethylsiloxane) adsorbed onto the surface of magnetite (γ-Fe(2)0(3)) nanoparticles 7-10 nm in diameter. The material is homogenous at very small length scales (< 100 nm) and can be crosslinked to form a flexible, magnetic material which is ideally suited for the fabrication of micro- to nanoscale magnetic actuators. The loading fraction of magnetic nanoparticles in the composite can be varied smoothly from 0 - 50% wt. without loss of homogeneity, providing a simple mechanism for tuning actuator response. We evaluate the material properties of the composite across a range of nanoparticle loading, and demonstrate a magnetic-field-induced increase in compressive modulus as high as 300%. Furthermore, we implement a strategy for predicting the optimal nanoparticle loading for magnetic actuation applications, and show that our predictions correlate well with experimental findings.

Chemical Interaction-Guided, Metal-Free Growth of Large-Area Hexagonal Boron Nitride on Silicon-Based Substrates.

PubMed

Behura, Sanjay; Nguyen, Phong; Debbarma, Rousan; Che, Songwei; Seacrist, Michael R; Berry, Vikas

2017-05-23

Hexagonal boron nitride (h-BN) is an ideal platform for interfacing with two-dimensional (2D) nanomaterials to reduce carrier scattering for high-quality 2D electronics. However, scalable, transfer-free growth of hexagonal boron nitride (h-BN) remains a challenge. Currently, h-BN-based 2D heterostructures require exfoliation or chemical transfer of h-BN grown on metals resulting in small areas or significant interfacial impurities. Here, we demonstrate a surface-chemistry-influenced transfer-free growth of large-area, uniform, and smooth h-BN directly on silicon (Si)-based substrates, including Si, silicon nitride (Si 3 N 4 ), and silicon dioxide (SiO 2 ), via low-pressure chemical vapor deposition. The growth rates increase with substrate electronegativity, Si < Si 3 N 4 < SiO 2 , consistent with the adsorption rates calculated for the precursor molecules via atomistic molecular dynamics simulations. Under graphene with high grain density, this h-BN film acts as a polymer-free, planar-dielectric interface increasing carrier mobility by 3.5-fold attributed to reduced surface roughness and charged impurities. This single-step, chemical interaction guided, metal-free growth mechanism of h-BN for graphene heterostructures establishes a potential pathway for the design of complex and integrated 2D-heterostructured circuitry.

Characterization of Si (sub X)Ge (sub 1-x)/Si Heterostructures for Device Applications Using Spectroscopic Ellipsometry

NASA Technical Reports Server (NTRS)

Sieg, R. M.; Alterovitz, S. A.; Croke, E. T.; Harrell, M. J.; Tanner, M.; Wang, K. L.; Mena, R. A.; Young, P. G.

1993-01-01

Spectroscopic ellipsometry (SE) characterization of several complex Si (sub X)Ge (sub 1-x)/Si heterostructures prepared for device fabrication, including structures for heterojunction bipolar transistors (HBT), p-type and n-type heterostructure modulation doped field effect transistors, has been performed. We have shown that SE can simultaneously determine all active layer thicknesses, Si (sub X)Ge (sub 1-x) compositions, and the oxide overlayer thickness, with only a general knowledge of the structure topology needed a priori. The characterization of HBT material included the SE analysis of a Si (sub X)Ge (sub 1-x) layer deeply buried (600 nanometers) under the silicon emitter and cap layers. In the SE analysis of n-type heterostructures, we examined for the first time a silicon layer under tensile strain. We found that an excellent fit can be obtained using optical constants of unstrained silicon to represent the strained silicon conduction layer. We also used SE to measure lateral sample homogeneity, providing quantitative identification of the inhomogeneous layer. Surface overlayers resulting from prior sample processing were also detected and measured quantitatively. These results should allow SE to be used extensively as a non-destructive means of characterizing Si (sub X)Ge (sub 1-x)/Si heterostructures prior to device fabrication and testing.

3D printing for health & wealth: Fabrication of custom-made medical devices through additive manufacturing

NASA Astrophysics Data System (ADS)

Colpani, Alessandro; Fiorentino, Antonio; Ceretti, Elisabetta

2018-05-01

Additive Manufacturing (AM) differs from traditional manufacturing technologies by its ability to handle complex shapes with great design flexibility. These features make the technique suitable to fabricate customized components, particularly answering specific custom needs. Although AM mainly referred to prototyping, nowadays the interest in direct manufacturing of actual parts is growing. This article shows the application of AM within the project 3DP-4H&W (3D Printing for Health & Wealth) which involves engineers and physicians for developing pediatric custom-made medical devices to enhance the fulfilling of the patients specific needs. In the project, two types of devices made of a two-component biocompatible silicone are considered. The first application (dental field) consists in a device for cleft lip and palate. The second one (audiological field) consists in an acoustic prosthesis. The geometries of the devices are based on the anatomy of the patient that is obtained through a 3D body scan process. For both devices, two different approaches were planned, namely direct AM and indirect Rapid Tooling (RT). In particular, direct AM consists in the FDM processing of silicone, while RT consists in molds FDM fabrication followed by silicone casting. This paper presents the results of the RT method that is articulated in different phases: the acquisition of the geometry to be realized, the design of the molds taking into account the casting feasibility (as casting channel, vents, part extraction), the realization of molds produced through AM, molds surface chemical finishing, pouring and curing of the silicone. The fabricated devices were evaluated by the physicians team that confirmed the effectiveness of the proposed procedure in fabricating the desired devices. Moreover, the procedure can be used as a general method to extend the range of applications to any custom-made device for anatomic districts, especially where complex shapes are present (as tracheal or maxillary prostheses).

Polyether complexes of groups 13 and 14.

PubMed

Swidan, Ala'aeddeen; Macdonald, Charles L B

2016-07-21

Notable aspects of the chemistry of complexes of polyether ligands including crown ethers, cryptands, glycols, glymes, and related polyether ligands with heavier group 13 and 14 elements are reviewed with a focus on results from 2005 to the present. The majority of reported polyether complexes contain lead(ii) and thallium(i) but recent breakthroughs in regard to the preparation of low oxidation state reagents of the lighter congeners have allowed for the generation of complexes containing indium(i), gallium(i), germanium(ii), and even silicon(ii). The important roles of ligand size, donor types, and counter anions in regard to the chemical properties of the polyether complexes is highlighted. A particular focus on the structural aspects of the numerous coordination complexes provides a rationale for some of the spectacular contributions that such compounds have made to Modern Main Group Chemistry.

Neutral and cationic phosphoramide adducts of silicon tetrachloride: synthesis and characterization of their solution and solid-state structures.

PubMed

Denmark, Scott E; Eklov, Brian M

2008-01-01

The solution and solid-state structures of hexamethylphosphoramide (HMPA) adducts of tetrachlorosilane (SiCl4) are discussed. In solution, the meridional and facial isomers of the hexa-coordinate cationic complex 3 HMPASiCl3 + Cl(-) (2) predominate at all HMPA concentrations, and are in equilibrium with the hexa-coordinate neutral trans- and cis-2 HMPASiCl4 complexes (1), as well as the penta-coordinate cationic cis-2 HMPASiCl3 + Cl(-) (3). Single crystal X-ray analyses are reported for the ionized mer-3 HMPASiCl3 + HCl2 (-) and the neutral trans-2 HMPASiCl4 complexes.

The Culture of High Technology: Is It "Female Friendly?"

ERIC Educational Resources Information Center

Kelly, Jan Wallace

To better understand the complexity of organizational life as a cultural system whose members share particular values, attitudes, and ways of knowing, and to understand the role of women in this culture, a study was conducted using female managers at 12 high technology companies in California's "Silicon Valley." Informants were selected…

Nanoparticle Solutions for Printed Electronics

DTIC Science & Technology

2013-09-19

the printed semiconductor materials and their nanoparticle and colloidal precursors. Without this basic knowledge, further development and the...titania, silica ) were investigated in the production of complementary inks for complex devices. These were either obtained commercially in...layers were also deposited on borosilicate glass and silicon wafers. In the photovoltaic program, hybrid inorganic-organic semiconductor combinations

Molecular recognition of halogen-tagged aromatic VOCs at the air-silicon interface.

PubMed

Condorelli, Guglielmo G; Motta, Alessandro; Favazza, Maria; Gurrieri, Ettore; Betti, Paolo; Dalcanale, Enrico

2010-01-14

Selective and reversible complexation of halogen-tagged aromatic VOCs by a quinoxaline cavitand-decorated Si surface is demonstrated. The specific host-guest interactions of the Si-bonded receptors are proved to be responsible of the surface recognition properties, while extracavity non specific adsorptions are totally suppressed compared to the bulk material.

Complex apodized Bragg grating filters without circulators in silicon-on-insulator.

PubMed

Simard, Alexandre D; LaRochelle, Sophie

2015-06-29

Bragg gratings operating in reflection are versatile filters that are an important building block of photonic circuits but, so far, their use has been limited due to the absence of CMOS compatible integrated circulators. In this paper, we propose to introduce two identical Bragg gratings in the arms of a Mach-Zehnder interferometer built with multimode interference 2 x 2 couplers to provide a reflective filter without circulator. We show that this structure has unique properties that significantly reduce phase noise distortions, avoid the need for thermal phase tuning, and make it compatible with complex apodization functions implemented through superposition apodization. We experimentally demonstrate several Bragg grating filters with high quality reflection spectra. For example, we successfully fabricated a 4 nm dispersion-less square-shaped filter having a sidelobe suppression ratio better than 15 dB and an in-band phase response with a group delay standard deviation of 2.0 ps. This result will enable the fabrication of grating based narrowband reflective filters having sharp spectral responses, which represents a major improvement in the filtering capability of the silicon platform.

GaAs VLSI for aerospace electronics

NASA Technical Reports Server (NTRS)

Larue, G.; Chan, P.

1990-01-01

Advanced aerospace electronics systems require high-speed, low-power, radiation-hard, digital components for signal processing, control, and communication applications. GaAs VLSI devices provide a number of advantages over silicon devices including higher carrier velocities, ability to integrate with high performance optical devices, and high-resistivity substrates that provide very short gate delays, good isolation, and tolerance to many forms of radiation. However, III-V technologies also have disadvantages, such as lower yield compared to silicon MOS technology. Achieving very large scale integration (VLSI) is particularly important for fast complex systems. At very short gate delays (less than 100 ps), chip-to-chip interconnects severely degrade circuit clock rates. Complex systems, therefore, benefit greatly when as many gates as possible are placed on a single chip. To fully exploit the advantages of GaAs circuits, attention must be focused on achieving high integration levels by reducing power dissipation, reducing the number of devices per logic function, and providing circuit designs that are more tolerant to process and environmental variations. In addition, adequate noise margin must be maintained to ensure a practical yield.

Metal-metal bonds in f-element chemistry.

PubMed

Liddle, Stephen T; Mills, David P

2009-08-07

The molecular chemistry of the f-elements is traditionally dominated by the use of carbon-, nitrogen-, oxygen-, or halide-ligands. However, the use of metal-based fragments as ligands is underdeveloped, which contrasts to the fields of d- and p-block metal-metal complexes that have developed extensively over the last fifty years. This perspective outlines the development of compounds, which possess polarised covalent or donor-acceptor f-element-metal bonds. For this review, the f-element is defined as (i) a group 3 or lanthanide metal: scandium, yttrium, lanthanum to lutetium, or (ii) an actinide metal: thorium, or uranium, and the metal is defined as a d-block transition metal, or a group 13 (aluminium or gallium), a group 14 (silicon, germanium, or tin), or a group 15 (antimony, or bismuth) metal. Silicon, germanium, and antimony are traditionally classified as metalloids but they are included for completeness. This review focuses mainly on complexes that have been structurally authenticated by single-crystal X-ray diffraction studies and we highlight novel aspects of their syntheses, properties, and reactivities.

Vertical nanopillars for highly localized fluorescence imaging

PubMed Central

Xie, Chong; Hanson, Lindsey; Cui, Yi; Cui, Bianxiao

2011-01-01

Observing individual molecules in a complex environment by fluorescence microscopy is becoming increasingly important in biological and medical research, for which critical reduction of observation volume is required. Here, we demonstrate the use of vertically aligned silicon dioxide nanopillars to achieve below-the-diffraction-limit observation volume in vitro and inside live cells. With a diameter much smaller than the wavelength of visible light, a transparent silicon dioxide nanopillar embedded in a nontransparent substrate restricts the propagation of light and affords evanescence wave excitation along its vertical surface. This effect creates highly confined illumination volume that selectively excites fluorescence molecules in the vicinity of the nanopillar. We show that this nanopillar illumination can be used for in vitro single-molecule detection at high fluorophore concentrations. In addition, we demonstrate that vertical nanopillars interface tightly with live cells and function as highly localized light sources inside the cell. Furthermore, specific chemical modification of the nanopillar surface makes it possible to locally recruit proteins of interest and simultaneously observe their behavior within the complex, crowded environment of the cell. PMID:21368157

Interaction of cationic carbosilane dendrimers and their complexes with siRNA with erythrocytes and red blood cell ghosts.

PubMed

Wrobel, Dominika; Kolanowska, Katarzyna; Gajek, Arkadiusz; Gomez-Ramirez, Rafael; de la Mata, Javier; Pedziwiatr-Werbicka, Elżbieta; Klajnert, Barbara; Waczulikova, Iveta; Bryszewska, Maria

2014-03-01

We have investigated the interactions between cationic NN16 and BDBR0011 carbosilane dendrimers with red blood cells or their cell membranes. The carbosilane dendrimers used possess 16 cationic functional groups. Both the dendrimers are made of water-stable carbon-silicon bonds, but NN16 possesses some oxygen-silicon bonds that are unstable in water. The nucleic acid used in the experiments was targeted against GAG-1 gene from the human immunodeficiency virus, HIV-1. By binding to the outer leaflet of the membrane, carbosilane dendrimers decreased the fluidity of the hydrophilic part of the membrane but increased the fluidity of the hydrophobic interior. They induced hemolysis, but did not change the morphology of the cells. Increasing concentrations of dendrimers induced erythrocyte aggregation. Binding of short interfering ribonucleic acid (siRNA) to a dendrimer molecule decreased the availability of cationic groups and diminished their cytotoxicity. siRNA-dendrimer complexes changed neither the fluidity of biological membranes nor caused cell hemolysis. Addition of dendriplexes to red blood cell suspension induced echinocyte formation. Copyright © 2013 Elsevier B.V. All rights reserved.

System-level integration of active silicon photonic biosensors

NASA Astrophysics Data System (ADS)

Laplatine, L.; Al'Mrayat, O.; Luan, E.; Fang, C.; Rezaiezadeh, S.; Ratner, D. M.; Cheung, K.; Dattner, Y.; Chrostowski, L.

2017-02-01

Biosensors based on silicon photonic integrated circuits have attracted a growing interest in recent years. The use of sub-micron silicon waveguides to propagate near-infrared light allows for the drastic reduction of the optical system size, while increasing its complexity and sensitivity. Using silicon as the propagating medium also leverages the fabrication capabilities of CMOS foundries, which offer low-cost mass production. Researchers have deeply investigated photonic sensor devices, such as ring resonators, interferometers and photonic crystals, but the practical integration of silicon photonic biochips as part of a complete system has received less attention. Herein, we present a practical system-level architecture which can be employed to integrate the aforementioned photonic biosensors. We describe a system based on 1 mm2 dies that integrate germanium photodetectors and a single light coupling device. The die are embedded into a 16x16 mm2 epoxy package to enable microfluidic and electrical integration. First, we demonstrate a simple process to mimic Fan-Out Wafer-level-Packaging, which enables low-cost mass production. We then characterize the photodetectors in the photovoltaic mode, which exhibit high sensitivity at low optical power. Finally, we present a new grating coupler concept to relax the lateral alignment tolerance down to +/- 50 μm at 1-dB (80%) power penalty, which should permit non-experts to use the biochips in a"plug-and-play" style. The system-level integration demonstrated in this study paves the way towards the mass production of low-cost and highly sensitive biosensors, and can facilitate their wide adoption for biomedical and agro-environmental applications.

Stress induced phase transitions in silicon

NASA Astrophysics Data System (ADS)

Budnitzki, M.; Kuna, M.

2016-10-01

Silicon has a tremendous importance as an electronic, structural and optical material. Modeling the interaction of a silicon surface with a pointed asperity at room temperature is a major step towards the understanding of various phenomena related to brittle as well as ductile regime machining of this semiconductor. If subjected to pressure or contact loading, silicon undergoes a series of stress-driven phase transitions accompanied by large volume changes. In order to understand the material's response for complex non-hydrostatic loading situations, dedicated constitutive models are required. While a significant body of literature exists for the dislocation dominated high-temperature deformation regime, the constitutive laws used for the technologically relevant rapid low-temperature loading have severe limitations, as they do not account for the relevant phase transitions. We developed a novel finite deformation constitutive model set within the framework of thermodynamics with internal variables that captures the stress induced semiconductor-to-metal (cd-Si → β-Si), metal-to-amorphous (β-Si → a-Si) as well as amorphous-to-amorphous (a-Si → hda-Si, hda-Si → a-Si) transitions. The model parameters were identified in part directly from diamond anvil cell data and in part from instrumented indentation by the solution of an inverse problem. The constitutive model was verified by successfully predicting the transformation stress under uniaxial compression and load-displacement curves for different indenters for single loading-unloading cycles as well as repeated indentation. To the authors' knowledge this is the first constitutive model that is able to adequately describe cyclic indentation in silicon.

Making Ceramic Components For Advanced Aircraft Engines

NASA Technical Reports Server (NTRS)

Franklin, J. E.; Ezis, A.

1994-01-01

Lightweight, oxidation-resistant silicon nitride components containing intricate internal cooling and hydraulic passages and capable of withstanding high operating temperatures made by ceramic-platelet technology. Used to fabricate silicon nitride test articles of two types: components of methane-cooled regenerator for air turbo ramjet engine and components of bipropellant injector for rocket engine. Procedures for development of more complex and intricate components established. Technology has commercial utility in automotive, aircraft, and environmental industries for manufacture of high-temperature components for use in regeneration of fuels, treatment of emissions, high-temperature combustion devices, and application in which other high-temperature and/or lightweight components needed. Potential use in fabrication of combustors and high-temperature acoustic panels for suppression of noise in future high-speed aircraft.

All-optical nanoscale thermometry with silicon-vacancy centers in diamond

NASA Astrophysics Data System (ADS)

Nguyen, Christian T.; Evans, Ruffin E.; Sipahigil, Alp; Bhaskar, Mihir K.; Sukachev, Denis D.; Agafonov, Viatcheslav N.; Davydov, Valery A.; Kulikova, Liudmila F.; Jelezko, Fedor; Lukin, Mikhail D.

2018-05-01

We demonstrate an all-optical thermometer based on an ensemble of silicon-vacancy centers (SiVs) in diamond by utilizing the sensitivity of the zero-phonon line wavelength to temperature, Δλ/ΔT =0.0124 (2 ) nm K-1 [6.8(1) GHz K-1]. Using SiVs in bulk diamond, we achieve 70 mK precision at room temperature with a temperature uncertainty σT=360 mK/√{H z } . Finally, we use SiVs in 200 nm nanodiamonds as local temperature probes with 521 mK/ √{H z } uncertainty and achieve sub-Kelvin precision. These properties deviate by less than 1% between nanodiamonds, enabling calibration-free thermometry for sensing and control of complex nanoscale systems.

A digital front-end and readout microsystem for calorimetry at LHC

NASA Astrophysics Data System (ADS)

Alippi, C.; Appelquist, G.; Berglund, S.; Bohm, C.; Breveglieri, L.; Brigati, S.; Carlson, P.; Cattaneo, P.; Dadda, L.; David, J.; Del Buono, L.; Dell'Acqua, A.; Engström, M.; Fumagalli, G.; Gatti, U.; Genat, J. F.; Goggi, G.; Hansen, M.; Hentzell, H.; Höglund, I.; Inkinen, S.; Kerek, A.; Lebbolo, H.; LeDortz, O.; Lofstedt, B.; Maloberti, F.; Nayman, P.; Persson, S.-T.; Piuri, V.; Salice, F.; Sami, M.; Savoy-Navarro, A.; Stefanelli, R.; Sundblad, R.; Svensson, C.; Torelli, G.; Vanuxem, J. P.; Yamdagni, N.; Yuan, J.; Zitoun, R.

1994-04-01

A digital solution to the front-end electronics for calorimetric detectors at future supercolliders is presented. The solution is based on high speed {A}/{D} converters, a fully programmable pipeline/digital filter chain and local intelligence. Questions of error correction, fault-tolerance and system redundancy are also being considered. A system integration of a multichannel device in a multichip, Silicon-on-Silicon Microsystem hybrid, is used. This solution allows a new level of integration of complex analogue and digital functions, with an excellent flexibility in mixing technologies for the different functional blocks. It also allows a high degree of programmability at both the function and the system level, and offers the possibility of customising the microsystem with detector-specific functions.

Dielectric properties of binary mixtures of methyl iso butyl ketone and amino silicone oil

NASA Astrophysics Data System (ADS)

Shah, K. N.; Rana, V. A.; Trivedi, C. M.; Vankar, H. P.

2017-05-01

Dielectric permittivity ɛ*(ω) = ɛ' - jɛ″ of the binary mixtures of the methyl iso butyl ketone and amino silicone oil in the frequency range 100 Hz to 2 MHz were measured using precision LCR meter at 305.15 K. Relative complex permittivity spectra in the frequency range 100 Hz to 2 MHz, of the mixture solutions of varying concentrations is reported. Determined values of the permittivity at optical frequency of all the samples are also reported. The dielectric parameters are used to gain information about the effect of concentration variation of components of the mixtures on the dielectric properties. It also provides the information about electrode polarization phenomena taking place under the low frequency A.C. electric field.

Joining of Silicon Carbide-Based Ceramics by Reaction Forming Method

NASA Technical Reports Server (NTRS)

Singh, M.; Kiser, J. D.

1997-01-01

Recently, there has been a surge of interest in the development and testing of silicon-based ceramics and composite components for a number of aerospace and ground based systems. The designs often require fabrication of complex shaped parts which can be quite expensive. One attractive way of achieving this goal is to build up complex shapes by joining together geometrically simple shapes. However, the joints should have good mechanical strength and environmental stability comparable to the bulk materials. These joints should also be able to maintain their structural integrity at high temperatures. In addition, the joining technique should be practical, reliable, and affordable. Thus, joining has been recognized as one of the enabling technologies for the successful utilization of silicon carbide based ceramic components in high temperature applications. Overviews of various joining techniques, i.e., mechanical fastening, adhesive bonding, welding, brazing, and soldering have been provided in recent publications. The majority of the techniques used today are based on the joining of monolithic ceramics with metals either by diffusion bonding, metal brazing, brazing with oxides and oxynitrides, or diffusion welding. These techniques need either very high temperatures for processing or hot pressing (high pressures). The joints produced by these techniques have different thermal expansion coefficients than the ceramic materials, which creates a stress concentration in the joint area. The use temperatures for these joints are around 700 C. Ceramic joint interlayers have been developed as a means of obtaining high temperature joints. These joint interlayers have been produced via pre-ceramic polymers, in-situ displacement reactions, and reaction bonding techniques. Joints produced by the pre-ceramic polymer approach exhibit a large amounts of porosity and poor mechanical properties. On the other hand, hot pressing or high pressures are needed for in-situ displacement reactions and reaction bonding techniques. Due to the equipment required, these techniques are impractical for joining large or complex shaped components.

Boron deactivation in heavily boron-doped Czochralski silicon during rapid thermal anneal: Atomic level understanding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Chao; Dong, Peng; Yi, Jun

The changes in hole concentration of heavily boron (B)-doped Czochralski silicon subjected to high temperature rapid thermal anneal (RTA) and following conventional furnace anneal (CFA) have been investigated. It is found that decrease in hole concentration, namely, B deactivation, is observed starting from 1050 °C and increases with RTA temperature. The following CFA at 300–500 °C leads to further B deactivation, while that at 600–800 °C results in B reactivation. It is supposed that the interaction between B atoms and silicon interstitials (I) thus forming BI pairs leads to the B deactivation during the high temperature RTA, and, moreover, the formation of extendedmore » B{sub 2}I complexes results in further B deactivation in the following CFA at 300–500 °C. On the contrary, the dissociation of BI pairs during the following CFA at 600–800 °C enables the B reactivation. Importantly, the first-principles calculation results can soundly account for the above-mentioned supposition.« less

Optical surface analysis: a new technique for the inspection and metrology of optoelectronic films and wafers

NASA Astrophysics Data System (ADS)

Bechtler, Laurie; Velidandla, Vamsi

2003-04-01

In response to demand for higher volumes and greater product capability, integrated optoelectronic device processing is rapidly increasing in complexity, benefiting from techniques developed for conventional silicon integrated circuit processing. The needs for high product yield and low manufacturing cost are also similar to the silicon wafer processing industry. This paper discusses the design and use of an automated inspection instrument called the Optical Surface Analyzer (OSA) to evaluate two critical production issues in optoelectronic device manufacturing: (1) film thickness uniformity, and (2) defectivity at various process steps. The OSA measurement instrument is better suited to photonics process development than most equipment developed for conventional silicon wafer processing in two important ways: it can handle both transparent and opaque substrates (unlike most inspection and metrology tools), and it is a full-wafer inspection method that captures defects and film variations over the entire substrate surface (unlike most film thickness measurement tools). Measurement examples will be provided in the paper for a variety of films and substrates used for optoelectronics manufacturing.

Silicon photonic integrated circuit swept-source optical coherence tomography receiver with dual polarization, dual balanced, in-phase and quadrature detection.

PubMed

Wang, Zhao; Lee, Hsiang-Chieh; Vermeulen, Diedrik; Chen, Long; Nielsen, Torben; Park, Seo Yeon; Ghaemi, Allan; Swanson, Eric; Doerr, Chris; Fujimoto, James

2015-07-01

Optical coherence tomography (OCT) is a widely used three-dimensional (3D) optical imaging method with many biomedical and non-medical applications. Miniaturization, cost reduction, and increased functionality of OCT systems will be critical for future emerging clinical applications. We present a silicon photonic integrated circuit swept-source OCT (SS-OCT) coherent receiver with dual polarization, dual balanced, in-phase and quadrature (IQ) detection. We demonstrate multiple functional capabilities of IQ polarization resolved detection including: complex-conjugate suppressed full-range OCT, polarization diversity detection, and polarization-sensitive OCT. To our knowledge, this is the first demonstration of a silicon photonic integrated receiver for OCT. The integrated coherent receiver provides a miniaturized, low-cost solution for SS-OCT, and is also a key step towards a fully integrated high speed SS-OCT system with good performance and multi-functional capabilities. With further performance improvement and cost reduction, photonic integrated technology promises to greatly increase penetration of OCT systems in existing applications and enable new applications.

Annealing and anomalous high-energy electron irradiation effects in low-cost silicon N+P solar cells

NASA Technical Reports Server (NTRS)

Garlick, G. F. J.; Kachare, A. H.

1981-01-01

Silicon solar cells of N(+)P type were subjected to 1 MeV electron irradiation (up to 10 to the 16th electrons/sq cm) and then annealed at 450 C for 20 min or annealed with no electron irradiation. Electron irradiation resulted in a degradation of longer wavelength cell response, but produced a marked enhancement of response at shorter wavelengths with a peak change of 40% at 0.44 microns. Subsequent thermal anneal at 450 C reduced the long-wavelength degradation, but enhancement at shorter wavelengths persisted. Excitation at the shorter wavelengths was in the N(+)-diffused layer and in the junction region of the cell. Anneal of unirradiated cells produced shorter-wavelength enhancement with a similar peaking at 0.44 microns, but with a relative change of only 20%. More enhancement was produced in the longer wavelength region (up to 0.8 microns). These effects in the different cell regions are explained by a decrease in the interstitial oxygen-impurity complexes (deep recombination levels) and the formation of substantial oxygen-silicon vacancy centers (donors).

Influence of silicon defects on the adsorption of thiophene-like compounds on polycyclic aromatic hydrocarbons: a theoretical study using thiophene + coronene as the simplest model.

PubMed

Galano, Annia

2007-03-08

Physisorption and chemisorption processes of thiophene on coronene and 2Si-coronene have been studied using density functional theory and MP2 methods. These systems have been chosen as the simplest models to describe the adsorption of thiophene-like compounds on polycyclic aromatic hydrocarbons (PAHs). The calculated data suggest that the presence of silicon atoms in PAHs could favor their interaction with thiophene and similar compounds. Small stabilization energies have been found for several physisorbed complexes. The thiophene chemisorption on coronene seems very unlikely to occur, while that on 2Si-coronene leads to addition products which are very stable, with respect to the isolated reactants. These chemisorption processes were found to be exoergic (DeltaG < 0) in the gas phase and in the nonpolar liquid phase. The results reported in this work suggest that silicon defects on extended polycyclic aromatic hydrocarbons, such as graphite, soot, and large-diameter carbon nanotubes, could make them useful in the removal processes of aromatic sulfur compounds from oil hydrocarbons.

Luminescence of silicon dioxide different polymorph modification: Silica glass, α-quartz, stishovite, coesite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trukhin, A. N., E-mail: truhins@cfi.lu.lv

2014-10-21

Stishovite, coesite, oxygen deficient silica glass as well as irradiated α-quartz, exhibit two luminescence bands: a blue one and an UV one both excitable in the range within optical gap. There are similarities in spectral position and in luminescence decay kinetics among centers in these materials. The interpretation was done on the model of Oxygen Deficient Centers (ODC) [1]. The ODC(II) or twofold coordinated silicon and ODC(I) are distinguished. ODC(I) is object of controversial interpretation. The Si-Si oxygen vacancy [2] and complex defect including latent twofold coordinated silicon [3] are proposed. Remarkably, this luminescence center does not exist in asmore » grown crystalline α-quartz. However, destructive irradiation of α-quartz crystals with fast neutrons, γ rays, or dense electron beams [4–6] creates ODC(I) like defect. In tetrahedron structured coesite the self trapped exciton (STE) luminescence observed with high energetic yield (∼30%) like in α-quartz crystals. STE in coesite coexists with oxygen deficient-like center. In octahedron structured stishovite STE was not found and only ODC exists.« less

Improved silicon carbide for advanced heat engines

NASA Technical Reports Server (NTRS)

Whalen, Thomas J.; Mangels, J. A.

1986-01-01

The development of silicon carbide materials of high strength was initiated and components of complex shape and high reliability were formed. The approach was to adapt a beta-SiC powder and binder system to the injection molding process and to develop procedures and process parameters capable of providing a sintered silicon carbide material with improved properties. The initial effort was to characterize the baseline precursor materials, develop mixing and injection molding procedures for fabricating test bars, and characterize the properties of the sintered materials. Parallel studies of various mixing, dewaxing, and sintering procedures were performed in order to distinguish process routes for improving material properties. A total of 276 modulus-of-rupture (MOR) bars of the baseline material was molded, and 122 bars were fully processed to a sinter density of approximately 95 percent. Fluid mixing techniques were developed which significantly reduced flaw size and improved the strength of the material. Initial MOR tests indicated that strength of the fluid-mixed material exceeds the baseline property by more than 33 percent. the baseline property by more than 33 percent.

Silicon photonic integrated circuit swept-source optical coherence tomography receiver with dual polarization, dual balanced, in-phase and quadrature detection

PubMed Central

Wang, Zhao; Lee, Hsiang-Chieh; Vermeulen, Diedrik; Chen, Long; Nielsen, Torben; Park, Seo Yeon; Ghaemi, Allan; Swanson, Eric; Doerr, Chris; Fujimoto, James

2015-01-01

Optical coherence tomography (OCT) is a widely used three-dimensional (3D) optical imaging method with many biomedical and non-medical applications. Miniaturization, cost reduction, and increased functionality of OCT systems will be critical for future emerging clinical applications. We present a silicon photonic integrated circuit swept-source OCT (SS-OCT) coherent receiver with dual polarization, dual balanced, in-phase and quadrature (IQ) detection. We demonstrate multiple functional capabilities of IQ polarization resolved detection including: complex-conjugate suppressed full-range OCT, polarization diversity detection, and polarization-sensitive OCT. To our knowledge, this is the first demonstration of a silicon photonic integrated receiver for OCT. The integrated coherent receiver provides a miniaturized, low-cost solution for SS-OCT, and is also a key step towards a fully integrated high speed SS-OCT system with good performance and multi-functional capabilities. With further performance improvement and cost reduction, photonic integrated technology promises to greatly increase penetration of OCT systems in existing applications and enable new applications. PMID:26203382

L-shaped fiber-chip grating couplers with high directionality and low reflectivity fabricated with deep-UV lithography.

PubMed

Benedikovic, Daniel; Alonso-Ramos, Carlos; Pérez-Galacho, Diego; Guerber, Sylvain; Vakarin, Vladyslav; Marcaud, Guillaume; Le Roux, Xavier; Cassan, Eric; Marris-Morini, Delphine; Cheben, Pavel; Boeuf, Frédéric; Baudot, Charles; Vivien, Laurent

2017-09-01

Grating couplers enable position-friendly interfacing of silicon chips by optical fibers. The conventional coupler designs call upon comparatively complex architectures to afford efficient light coupling to sub-micron silicon-on-insulator (SOI) waveguides. Conversely, the blazing effect in double-etched gratings provides high coupling efficiency with reduced fabrication intricacy. In this Letter, we demonstrate for the first time, to the best of our knowledge, the realization of an ultra-directional L-shaped grating coupler, seamlessly fabricated by using 193 nm deep-ultraviolet (deep-UV) lithography. We also include a subwavelength index engineered waveguide-to-grating transition that provides an eight-fold reduction of the grating reflectivity, down to 1% (-20  dB). A measured coupling efficiency of -2.7  dB (54%) is achieved, with a bandwidth of 62 nm. These results open promising prospects for the implementation of efficient, robust, and cost-effective coupling interfaces for sub-micrometric SOI waveguides, as desired for large-volume applications in silicon photonics.

Fabrication of porous silicon nitride ceramics using binder jetting technology

NASA Astrophysics Data System (ADS)

Rabinskiy, L.; Ripetsky, A.; Sitnikov, S.; Solyaev, Y.; Kahramanov, R.

2016-07-01

This paper presents the results of the binder jetting technology application for the processing of the Si3N4-based ceramics. The difference of the developed technology from analogues used for additive manufacturing of silicon nitride ceramics is a method of the separate deposition of the mineral powder and binder without direct injection of suspensions/slurries. It is assumed that such approach allows reducing the technology complexity and simplifying the process of the feedstock preparation, including the simplification of the composite materials production. The binders based on methyl ester of acrylic acid with polyurethane and modified starch were studied. At this stage of the investigations, the technology of green body's fabrication is implemented using a standard HP cartridge mounted on the robotic arm. For the coordinated operation of the cartridge and robot the specially developed software was used. Obtained green bodies of silicon powder were used to produce the ceramic samples via reaction sintering. The results of study of ceramics samples microstructure and composition are presented. Sintered ceramics are characterized by fibrous α-Si3N4 structure and porosity up to 70%.

The Solid State Image Sensor's Contribution To The Development Of Silicon Technology

NASA Astrophysics Data System (ADS)

Weckler, Gene P.

1985-12-01

Until recently, a solid-state image sensor with full television resolution was a dream. However, the dream of a solid state image sensor has been a driving force in the development of silicon technology for more than twenty-five years. There are probably many in the main stream of semiconductor technology who would argue with this; however, the solid state image sensor was conceived years before the invention of the semi conductor RAM or the microprocessor (i.e., even before the invention of the integrated circuit). No other potential application envisioned at that time required such complexity. How could anyone have ever hoped in 1960 to make a semi conductor chip containing half-a-million picture elements, capable of resolving eight to twelve bits of infornation, and each capable of readout rates in the tens of mega-pixels per second? As early as 1960 arrays of p-n junctions were being investigated as the optical targets in vidicon tubes, replacing the photoconductive targets. It took silicon technology several years to catch up with these dreamers.

Equivalence of the equilibrium and the nonequilibrium molecular dynamics methods for thermal conductivity calculations: From bulk to nanowire silicon

NASA Astrophysics Data System (ADS)

Dong, Haikuan; Fan, Zheyong; Shi, Libin; Harju, Ari; Ala-Nissila, Tapio

2018-03-01

Molecular dynamics (MD) simulations play an important role in studying heat transport in complex materials. The lattice thermal conductivity can be computed either using the Green-Kubo formula in equilibrium MD (EMD) simulations or using Fourier's law in nonequilibrium MD (NEMD) simulations. These two methods have not been systematically compared for materials with different dimensions and inconsistencies between them have been occasionally reported in the literature. Here we give an in-depth comparison of them in terms of heat transport in three allotropes of Si: three-dimensional bulk silicon, two-dimensional silicene, and quasi-one-dimensional silicon nanowire. By multiplying the correlation time in the Green-Kubo formula with an appropriate effective group velocity, we can express the running thermal conductivity in the EMD method as a function of an effective length and directly compare it to the length-dependent thermal conductivity in the NEMD method. We find that the two methods quantitatively agree with each other for all the systems studied, firmly establishing their equivalence in computing thermal conductivity.

Narrow bandgap semiconducting silicides: Intrinsic infrared detectors on a silicon chip

NASA Technical Reports Server (NTRS)

Mahan, John E.

1989-01-01

Polycrystalline thin films of CrSi2, LaSi2, and ReSi2 were grown on silicon substrates. Normal incidence optical transmittance and reflectance measurements were made as a function of wavelength. It was demonstrated that LaSi2 is a metallic conductor, but that CrSi2 and ReSi2 are, in fact, narrow bandgap semiconductors. For CrSi2, the complex index of refraction was determined by computer analysis of the optical data. From the imaginary part, the optical absorption coefficient was determined as a function of photon energy. It was shown that CrSi2 possesses an indirect forbidden energy gap of slightly less than 0.31 eV, and yet it is a very strong absorber of light above the absorption edge. On the other hand, the ReSi2 films exhibit an absorption edge in the vicinity of 0.2 eV. Measurements of the thermal activation energy of resistivity for ReSi2 indicate a bandgap of 0.18 eV. It is concluded that the semiconducting silicides merit further investigation for development as new silicon-compatible infrared detector materials.

Processing-Induced Electrically Active Defects in Black Silicon Nanowire Devices.

PubMed

Carapezzi, Stefania; Castaldini, Antonio; Mancarella, Fulvio; Poggi, Antonella; Cavallini, Anna

2016-04-27

Silicon nanowires (Si NWs) are widely investigated nowadays for implementation in advanced energy conversion and storage devices, as well as many other possible applications. Black silicon (BSi)-NWs are dry etched NWs that merge the advantages related to low-dimensionality with the special industrial appeal connected to deep reactive ion etching (RIE). In fact, RIE is a well established technique in microelectronics manufacturing. However, RIE processing could affect the electrical properties of BSi-NWs by introducing deep states into their forbidden gap. This work applies deep level transient spectroscopy (DLTS) to identify electrically active deep levels and the associated defects in dry etched Si NW arrays. Besides, the successful fitting of DLTS spectra of BSi-NWs-based Schottky barrier diodes is an experimental confirmation that the same theoretical framework of dynamic electronic behavior of deep levels applies in bulk as well as in low dimensional structures like NWs, when quantum confinement conditions do not occur. This has been validated for deep levels associated with simple pointlike defects as well as for deep levels associated with defects with richer structures, whose dynamic electronic behavior implies a more complex picture.

The magnetorheological fluid of carbonyl iron suspension blended with grafted MWCNT or graphene

NASA Astrophysics Data System (ADS)

Rwei, Syang-Peng; Ranganathan, Palraj; Chiang, Whe-Yi; Wang, Tza-Yi

2017-12-01

In this work, the magnetorheological (MR) fluids containing MWCNT/CI (carbonyl iron) complex and graphene/CI complex were prepared and have the better dispersity in silicone oil than CI powders alone. 1, 4-Aminobenzoic acid (PABA) was used as a grafting agent to modify CI powders to have NH2-end-group so that such nanoparticles can adsorb to acid-treated MWCNT or graphene via attraction of NH2 and COOH groups. The MWCNT/CI complex and graphene/CI complex have a structure of carbonyl iron nanoparticles adsorbed to MWCNT and graphene by self assembly, respectively. Because the carbonyl iron particles possessing magnetic permeability in nanometer scale adsorb to MWCNT or graphene which usually has a nanometer-scaled diameter and a micrometer-scaled length in this work, the dispersity of MWCNT/CI or graphene/CI complex in silicone oil is superior than the previous report [15] that the micrometer-scaled carbonyl iron microspheres were coated with multiwalled carbon nanotubes. Among CI (unmodified), MWCNT/CI and graphene/CI, graphene/CI has the best dispersity while MWCNT/CI still has the better dispersity than unmodified CI. At the temperature T = 300 K, the saturation magnetizations of CI, MWCNT/CI, graphene/CI are 208, 211 emu/g, and 204 emu/g, respectively, indicating that MWCNT/CI complex and graphene/CI complex still maintain the saturation magnetization as high as CI without being interfered by the blended MWCNT or graphene. A wide dynamic range of the yield stress adjusted through varying the electric current can be achieved by the MR fluids containing 69 wt% MWCNT/CI and graphene/CI which is useful in a shock absorber or damper. The result of the yield stress indicates the suspended MWCNT/CI particles are oriented more easily toward the direction perpendicular to the flow direction to block the flow stream lines.

Analytical Micromechanics Modeling Technique Developed for Ceramic Matrix Composites Analysis

NASA Technical Reports Server (NTRS)

Min, James B.

2005-01-01

Ceramic matrix composites (CMCs) promise many advantages for next-generation aerospace propulsion systems. Specifically, carbon-reinforced silicon carbide (C/SiC) CMCs enable higher operational temperatures and provide potential component weight savings by virtue of their high specific strength. These attributes may provide systemwide benefits. Higher operating temperatures lessen or eliminate the need for cooling, thereby reducing both fuel consumption and the complex hardware and plumbing required for heat management. This, in turn, lowers system weight, size, and complexity, while improving efficiency, reliability, and service life, resulting in overall lower operating costs.

High-throughput preparation of complex multi-scale patterns from block copolymer/homopolymer blend films.

PubMed

Park, Hyungmin; Kim, Jae-Up; Park, Soojin

2012-02-21

A simple, straightforward process for fabricating multi-scale micro- and nanostructured patterns from polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP)/poly(methyl methacrylate) (PMMA) homopolymer in a preferential solvent for PS and PMMA is demonstrated. When the PS-b-P2VP/PMMA blend films were spin-coated onto a silicon wafer, PS-b-P2VP micellar arrays consisting of a PS corona and a P2VP core were formed, while the PMMA macrodomains were isolated, due to the macrophase separation caused by the incompatibility between block copolymer micelles and PMMA homopolymer during the spin-coating process. With an increase of PMMA composition, the size of PMMA macrodomains increased. Moreover, the P2VP blocks have a strong interaction with a native oxide of the surface of the silicon wafer, so that the P2VP wetting layer was first formed during spin-coating, and PS nanoclusters were observed on the PMMA macrodomains beneath. Whereas when a silicon surface was modified with a PS brush layer, the PS nanoclusters underlying PMMA domains were not formed. The multi-scale patterns prepared from copolymer micelle/homopolymer blend films are used as templates for the fabrication of gold nanoparticle arrays by incorporating the gold precursor into the P2VP chains. The combination of nanostructures prepared from block copolymer micellar arrays and macrostructures induced by incompatibility between the copolymer and the homopolymer leads to the formation of complex, multi-scale surface patterns by a simple casting process. This journal is © The Royal Society of Chemistry 2012

Scaling up the Single Transducer Thickness-Independent Ultrasonic Imaging Method for Accurate Characterization of Microstructural Gradients in Monolithic and Composite Tubular Structures

NASA Technical Reports Server (NTRS)

Roth, Don J.; Carney, Dorothy V.; Baaklini, George Y.; Bodis, James R.; Rauser, Richard W.

1998-01-01

Ultrasonic velocity/time-of-flight imaging that uses back surface reflections to gauge volumetric material quality is highly suited for quantitative characterization of microstructural gradients including those due to pore fraction, density, fiber fraction, and chemical composition variations. However, a weakness of conventional pulse-echo ultrasonic velocity/time-of-flight imaging is that the image shows the effects of thickness as well as microstructural variations unless the part is uniformly thick. This limits this imaging method's usefulness in practical applications. Prior studies have described a pulse-echo time-of-flight-based ultrasonic imaging method that requires using a single transducer in combination with a reflector plate placed behind samples that eliminates the effect of thickness variation in the image. In those studies, this method was successful at isolating ultrasonic variations due to material microstructure in plate-like samples of silicon nitride, metal matrix composite, and polymer matrix composite. In this study, the method is engineered for inspection of more complex-shaped structures-those having (hollow) tubular/curved geometry. The experimental inspection technique and results are described as applied to (1) monolithic mullite ceramic and polymer matrix composite 'proof-of-concept' tubular structures that contain machined patches of various depths and (2) as-manufactured monolithic silicon nitride ceramic and silicon carbide/silicon carbide composite tubular structures that might be used in 'real world' applications.

A surface code quantum computer in silicon

PubMed Central

Hill, Charles D.; Peretz, Eldad; Hile, Samuel J.; House, Matthew G.; Fuechsle, Martin; Rogge, Sven; Simmons, Michelle Y.; Hollenberg, Lloyd C. L.

2015-01-01

The exceptionally long quantum coherence times of phosphorus donor nuclear spin qubits in silicon, coupled with the proven scalability of silicon-based nano-electronics, make them attractive candidates for large-scale quantum computing. However, the high threshold of topological quantum error correction can only be captured in a two-dimensional array of qubits operating synchronously and in parallel—posing formidable fabrication and control challenges. We present an architecture that addresses these problems through a novel shared-control paradigm that is particularly suited to the natural uniformity of the phosphorus donor nuclear spin qubit states and electronic confinement. The architecture comprises a two-dimensional lattice of donor qubits sandwiched between two vertically separated control layers forming a mutually perpendicular crisscross gate array. Shared-control lines facilitate loading/unloading of single electrons to specific donors, thereby activating multiple qubits in parallel across the array on which the required operations for surface code quantum error correction are carried out by global spin control. The complexities of independent qubit control, wave function engineering, and ad hoc quantum interconnects are explicitly avoided. With many of the basic elements of fabrication and control based on demonstrated techniques and with simulated quantum operation below the surface code error threshold, the architecture represents a new pathway for large-scale quantum information processing in silicon and potentially in other qubit systems where uniformity can be exploited. PMID:26601310

A surface code quantum computer in silicon.

PubMed

Hill, Charles D; Peretz, Eldad; Hile, Samuel J; House, Matthew G; Fuechsle, Martin; Rogge, Sven; Simmons, Michelle Y; Hollenberg, Lloyd C L

2015-10-01

The exceptionally long quantum coherence times of phosphorus donor nuclear spin qubits in silicon, coupled with the proven scalability of silicon-based nano-electronics, make them attractive candidates for large-scale quantum computing. However, the high threshold of topological quantum error correction can only be captured in a two-dimensional array of qubits operating synchronously and in parallel-posing formidable fabrication and control challenges. We present an architecture that addresses these problems through a novel shared-control paradigm that is particularly suited to the natural uniformity of the phosphorus donor nuclear spin qubit states and electronic confinement. The architecture comprises a two-dimensional lattice of donor qubits sandwiched between two vertically separated control layers forming a mutually perpendicular crisscross gate array. Shared-control lines facilitate loading/unloading of single electrons to specific donors, thereby activating multiple qubits in parallel across the array on which the required operations for surface code quantum error correction are carried out by global spin control. The complexities of independent qubit control, wave function engineering, and ad hoc quantum interconnects are explicitly avoided. With many of the basic elements of fabrication and control based on demonstrated techniques and with simulated quantum operation below the surface code error threshold, the architecture represents a new pathway for large-scale quantum information processing in silicon and potentially in other qubit systems where uniformity can be exploited.

Synthesis, Spectral, and In Vitro Antibacterial Studies of Organosilicon(IV) Complexes with Schiff Bases Derived from Amino Acids.

PubMed

Singh, Har Lal; Singh, Jangbhadur; Mukherjee, A

2013-01-01

The present work stems from our interest in the synthesis, characterization, and antibacterial evaluation of organosilicon(IV) complexes of a class of amino-acid-based Schiff base which have been prepared by the interaction of ethoxytrimethylsilane with the Schiff bases (N OH) in 1 : 1 molar ratio. These complexes have been characterized by elemental analysis, molar conductance, and spectroscopic studies including electronic IR and NMR ((1)H, (13)C, and (29)Si) spectroscopy. The analytical and spectral data suggest trigonal bipyramidal geometry around the silicon atom in the resulting complexes. The ligands and their organosilicon complexes have also been evaluated for in vitro antimicrobial activity against bacteria (Bacillus cereus, Nocardia spp., E. aerogenes, Escherichia coli, Klebsiella spp., and Staphylococcus spp.). The complexes were found to be more potent as compared to the ligands.

Lifetime degradation of n-type Czochralski silicon after hydrogenation

NASA Astrophysics Data System (ADS)

Vaqueiro-Contreras, M.; Markevich, V. P.; Mullins, J.; Halsall, M. P.; Murin, L. I.; Falster, R.; Binns, J.; Coutinho, J.; Peaker, A. R.

2018-04-01

Hydrogen plays an important role in the passivation of interface states in silicon-based metal-oxide semiconductor technologies and passivation of surface and interface states in solar silicon. We have shown recently [Vaqueiro-Contreras et al., Phys. Status Solidi RRL 11, 1700133 (2017)] that hydrogenation of n-type silicon slices containing relatively large concentrations of carbon and oxygen impurity atoms {[Cs] ≥ 1 × 1016 cm-3 and [Oi] ≥ 1017 cm-3} can produce a family of C-O-H defects, which act as powerful recombination centres reducing the minority carrier lifetime. In this work, evidence of the silicon's lifetime deterioration after hydrogen injection from SiNx coating, which is widely used in solar cell manufacturing, has been obtained from microwave photoconductance decay measurements. We have characterised the hydrogenation induced deep level defects in n-type Czochralski-grown Si samples through a series of deep level transient spectroscopy (DLTS), minority carrier transient spectroscopy (MCTS), and high-resolution Laplace DLTS/MCTS measurements. It has been found that along with the hydrogen-related hole traps, H1 and H2, in the lower half of the gap reported by us previously, hydrogenation gives rise to two electron traps, E1 and E2, in the upper half of the gap. The activation energies for electron emission from the E1 and E2 trap levels have been determined as 0.12, and 0.14 eV, respectively. We argue that the E1/H1 and E2/H2 pairs of electron/hole traps are related to two energy levels of two complexes, each incorporating carbon, oxygen, and hydrogen atoms. Our results show that the detrimental effect of the C-O-H defects on the minority carrier lifetime in n-type Si:O + C materials can be very significant, and the carbon concentration in Czochralski-grown silicon is a key parameter in the formation of the recombination centers.

REVIEW ARTICLE: How will physics be involved in silicon microelectronics

NASA Astrophysics Data System (ADS)

Kamarinos, Georges; Felix, Pierre

1996-03-01

By the year 2000 electronics will probably be the basis of the largest industry in the world. Silicon microelectronics will continue to keep a dominant place covering 99% of the `semiconductor market'. The aim of this review article is to indicate for the next decade the domains in which research work in `physics' is needed for a technological advance towards increasing speed, complexity and density of silicon ultra large scale integration (ULSI) integrated circuits (ICs). By `physics' we mean here not only condensed matter physics but also the basic physical chemistry and thermodynamics. The review begins with a brief and general introduction in which we elucidate the current state of the art and the trends in silicon microelectronics. Afterwards we examine the involvement of physics in silicon microelectronics in the two main sections. The first section concerns the processes of fabrication of ICs: lithography, oxidation, diffusion, chemical and physical vapour deposition, rapid thermal processing, etching, interconnections, ultra-clean processing and microcontamination. The second section concerns the electrical operation of the ULSI devices. It defines the integration scales and points out the importance of the intermediate scale of integration which is the scale of the next generation of ICs. The emergence of cryomicroelectronics is also reviewed and an extended paragraph is dedicated to the problem of reliability and ageing of devices and ICs: hot carrier degradation, interdevice coupling and noise are considered. It is shown, during our analysis, that the next generation of silicon ICs needs mainly: (i) `scientific' fabrication and (ii) microscopic modelling and simulation of the electrical characteristics of the scaled down devices. To attain the above objectives a return to the `first principles' of physics as well as a recourse to nonlinear and non-equilibrium thermodynamics are mandatory. In the references we list numerous review papers and references of specialized colloquia proceedings so that a more detailed survey of the subject is possible for the reader.

K- and L-edge X-ray absorption spectrum calculations of closed-shell carbon, silicon, germanium, and sulfur compounds using damped four-component density functional response theory.

PubMed

Fransson, Thomas; Burdakova, Daria; Norman, Patrick

2016-05-21

X-ray absorption spectra of carbon, silicon, germanium, and sulfur compounds have been investigated by means of damped four-component density functional response theory. It is demonstrated that a reliable description of relativistic effects is obtained at both K- and L-edges. Notably, an excellent agreement with experimental results is obtained for L2,3-spectra-with spin-orbit effects well accounted for-also in cases when the experimental intensity ratio deviates from the statistical one of 2 : 1. The theoretical results are consistent with calculations using standard response theory as well as recently reported real-time propagation methods in time-dependent density functional theory, and the virtues of different approaches are discussed. As compared to silane and silicon tetrachloride, an anomalous error in the absolute energy is reported for the L2,3-spectrum of silicon tetrafluoride, amounting to an additional spectral shift of ∼1 eV. This anomaly is also observed for other exchange-correlation functionals, but it is seen neither at other silicon edges nor at the carbon K-edge of fluorine derivatives of ethene. Considering the series of molecules SiH4-XFX with X = 1, 2, 3, 4, a gradual divergence from interpolated experimental ionization potentials is observed at the level of Kohn-Sham density functional theory (DFT), and to a smaller extent with the use of Hartree-Fock. This anomalous error is thus attributed partly to difficulties in correctly emulating the electronic structure effects imposed by the very electronegative fluorines, and partly due to inconsistencies in the spurious electron self-repulsion in DFT. Substitution with one, or possibly two, fluorine atoms is estimated to yield small enough errors to allow for reliable interpretations and predictions of L2,3-spectra of more complex and extended silicon-based systems.

Characterization and Analysis of Indium-Doped Silicon Extrinsic Detector Material

DTIC Science & Technology

1980-06-01

lines are likely to be due to donor- acceptor complexes of some type. The observation of these lines marks the first time that anyone has observed such...York, 1972. 18. R.S.C. Cobbold , Theory and Applications of Field Effect Transistors, John Wiley and Sons, New York, 1970. 19. W.N. Carr, and J.P. Mize

Noise-margin limitations on gallium-arsenide VLSI

NASA Technical Reports Server (NTRS)

Long, Stephen I.; Sundaram, Mani

1988-01-01

Two factors which limit the complexity of GaAs MESFET VLSI circuits are considered. Power dissipation sets an upper complexity limit for a given logic circuit implementation and thermal design. Uniformity of device characteristics and the circuit configuration determines the electrical functional yield. Projection of VLSI complexity based on these factors indicates that logic chips of 15,000 gates are feasible with the most promising static circuits if a maximum power dissipation of 5 W per chip is assumed. While lower power per gate and therefore more gates per chip can be obtained by using a popular E/D FET circuit, yields are shown to be small when practical device parameter tolerances are applied. Further improvements in materials, devices, and circuits wil be needed to extend circuit complexity to the range currently dominated by silicon.

Interactions between Silicon Oxide Nanoparticles (SONPs) and U(VI) Contaminations: Effects of pH, Temperature and Natural Organic Matters

PubMed Central

Wu, Hanyu; Li, Ping; Pan, Duoqiang; Yin, Zhuoxin; Fan, Qiaohui; Wu, Wangsuo

2016-01-01

The interactions between contaminations of U(VI) and silicon oxide nanoparticles (SONPs), both of which have been widely used in modern industry and induced serious environmental challenge due to their high mobility, bioavailability, and toxicity, were studied under different environmental conditions such as pH, temperature, and natural organic matters (NOMs) by using both batch and spectroscopic approaches. The results showed that the accumulation process, i.e., sorption, of U(VI) on SONPs was strongly dependent on pH and ionic strength, demonstrating that possible outer- and/or inner-sphere complexes were controlling the sorption process of U(VI) on SONPs in the observed pH range. Humic acid (HA), one dominated component of NOMs, bounded SONPs can enhance U(VI) sorption below pH~4.5, whereas restrain at high pH range. The reversible sorption of U(VI) on SONPs possibly indicated that the outer-sphere complexes were prevalent at pH 5. However, an irreversible interaction of U(VI) was observed in the presence of HA (Fig 1). It was mainly due to the ternary SONPs-HA-U(VI) complexes (Type A Complexes). After SONPs adsorbed U(VI), the particle size in suspension was apparently increased from ~240 nm to ~350 nm. These results showed that toxicity of both SONPs and U(VI) will decrease to some extent after the interaction in the environment. These findings are key for providing useful information on the possible mutual interactions among different contaminants in the environment. PMID:26930197

Comparison of disposable sutureless silicone ring and traditional metal ring in 23-gauge vitrectomy combined with cataract surgery

PubMed Central

Wu, Jian-Guo; Wei, Rui-Hua; Liu, Ai-Hua; Zhou, Xiao-Xu; Sun, Guo-Ling; Li, Xiao-Rong

2011-01-01

Background: The purpose of this prospective, interventional, comparative case series was to evaluate the efficiency and feasibility of a disposable sutureless silicone lens ring for corneal contact lens stabilization during combined 23-gauge vitrectomy and cataract surgery. Methods: We developed a ring consisting of a single silicone component with three footplates along the ring margin to fit cannulae for holding conventional contact lenses. Thirty eyes from 30 patients with cataract and vitreoretinal disease were included, and divided into two matched groups according to disease type and ring used. In Group A, we used a 23-gauge transconjunctival vitrectomy system and a disposable sutureless silicone lens ring (n = 15). In Group B, we used a 23-gauge transconjunctival vitrectomy system and a conventional metal lens ring (n = 15). The main outcome measures were: time required for vitrectomy preparation, rate of intraoperative corneal limbus bleeding, and limbus scar rate at the final follow-up visit. Results: Thirty cases were successfully completed. The average vitrectomy preparation time was less in Group A than in Group B (P < 0.01), and the average preparation time saved was 3.94 minutes. None of the Group A patients had intraoperative bleeding or postoperative scarring, whereas all 15 Group B cases had bleeding and five had scarring. There was a statistically significant difference between Group A and Group B for these complications (P ≤ 0.05). Conclusion: This report demonstrates the advantages of using a sutureless silicone ring during combined 23-gauge vitrectomy and cataract surgery. Using this method could allow extra time for the surgeon to pay more attention to complex vitreoretinal procedures. PMID:21760720

Comparison of disposable sutureless silicone ring and traditional metal ring in 23-gauge vitrectomy combined with cataract surgery.

PubMed

Wu, Jian-Guo; Wei, Rui-Hua; Liu, Ai-Hua; Zhou, Xiao-Xu; Sun, Guo-Ling; Li, Xiao-Rong

2011-01-01

The purpose of this prospective, interventional, comparative case series was to evaluate the efficiency and feasibility of a disposable sutureless silicone lens ring for corneal contact lens stabilization during combined 23-gauge vitrectomy and cataract surgery. We developed a ring consisting of a single silicone component with three footplates along the ring margin to fit cannulae for holding conventional contact lenses. Thirty eyes from 30 patients with cataract and vitreoretinal disease were included, and divided into two matched groups according to disease type and ring used. In Group A, we used a 23-gauge transconjunctival vitrectomy system and a disposable sutureless silicone lens ring (n = 15). In Group B, we used a 23-gauge transconjunctival vitrectomy system and a conventional metal lens ring (n = 15). The main outcome measures were: time required for vitrectomy preparation, rate of intraoperative corneal limbus bleeding, and limbus scar rate at the final follow-up visit. Thirty cases were successfully completed. The average vitrectomy preparation time was less in Group A than in Group B (P < 0.01), and the average preparation time saved was 3.94 minutes. None of the Group A patients had intraoperative bleeding or postoperative scarring, whereas all 15 Group B cases had bleeding and five had scarring. There was a statistically significant difference between Group A and Group B for these complications (P ≤ 0.05). This report demonstrates the advantages of using a sutureless silicone ring during combined 23-gauge vitrectomy and cataract surgery. Using this method could allow extra time for the surgeon to pay more attention to complex vitreoretinal procedures.

Electronic transport in mixed-phase hydrogenated amorphous/nanocrystalline silicon thin films

NASA Astrophysics Data System (ADS)

Wienkes, Lee Raymond

Interest in mixed-phase silicon thin film materials, composed of an amorphous semiconductor matrix in which nanocrystalline inclusions are embedded, stems in part from potential technological applications, including photovoltaic and thin film transistor technologies. Conventional mixed-phase silicon films are produced in a single plasma reactor, where the conditions of the plasma must be precisely tuned, limiting the ability to adjust the film and nanoparticle parameters independently. The films presented in this thesis are deposited using a novel dual-plasma co-deposition approach in which the nanoparticles are produced separately in an upstream reactor and then injected into a secondary reactor where an amorphous silicon film is being grown. The degree of crystallinity and grain sizes of the films are evaluated using Raman spectroscopy and X-ray diffraction respectively. I describe detailed electronic measurements which reveal three distinct conduction mechanisms in n-type doped mixed-phase amorphous/nanocrystalline silicon thin films over a range of nanocrystallite concentrations and temperatures, covering the transition from fully amorphous to ~30% nanocrystalline. As the temperature is varied from 470 to 10 K, we observe activated conduction, multiphonon hopping (MPH) and Mott variable range hopping (VRH) as the nanocrystal content is increased. The transition from MPH to Mott-VRH hopping around 100K is ascribed to the freeze out of the phonon modes. A conduction model involving the parallel contributions of these three distinct conduction mechanisms is shown to describe both the conductivity and the reduced activation energy data to a high accuracy. Additional support is provided by measurements of thermal equilibration effects and noise spectroscopy, both done above room temperature (>300 K). This thesis provides a clear link between measurement and theory in these complex materials.

Influence of N-type μc-SiOx:H intermediate reflector and top cell material properties on the electrical performance of "micromorph" tandem solar cells

NASA Astrophysics Data System (ADS)

Chatterjee, P.; Roca i Cabarrocas, P.

2018-01-01

Amorphous silicon (a-Si:H) / micro-crystalline silicon (μc-Si:H), "micromorph" tandem solar cells have been investigated using a detailed electrical - optical model. Although such a tandem has good light absorption over the entire visible spectrum, the a-Si:H top cell suffers from strong light-induced degradation (LID). To improve matters, we have replaced a-Si:H by hydrogenated polymorphous silicon (pm-Si:H), a nano-structured silicon thin film with lower LID than a-Si:H. But the latter's low current carrying capacity necessitates a thicker top cell for current-matching, again leading to LID problems. The solution is to introduce a suitable intermediate reflector (IR) at the junction between the sub-cells, to concentrate light of the shorter visible wavelengths into the top cell. Here we assess the suitability of N-type micro-crystalline silicon oxide (μc-SiOx:H) as an IR. The sensitivity of the solar cell performance to the complex refractive index, thickness and texture of such a reflector is studied. We conclude that N-μc-SiOx:H does concentrate light into the top sub-cell, thus reducing its required thickness for current-matching. However the IR also reflects light right out of the device; so that the initial efficiency suffers. The advantage of such an IR is ultimately seen in the stabilized state since the LID of a thin top cell is low. We also find that for high stabilized efficiencies, the IR should be flat (having no texture of its own). Our study indicates that we may expect to reach 15% stable tandem micromorph efficiency.

Determination of excitation profile and dielectric function spatial nonuniformity in porous silicon by using WKB approach.

PubMed

He, Wei; Yurkevich, Igor V; Canham, Leigh T; Loni, Armando; Kaplan, Andrey

2014-11-03

We develop an analytical model based on the WKB approach to evaluate the experimental results of the femtosecond pump-probe measurements of the transmittance and reflectance obtained on thin membranes of porous silicon. The model allows us to retrieve a pump-induced nonuniform complex dielectric function change along the membrane depth. We show that the model fitting to the experimental data requires a minimal number of fitting parameters while still complying with the restriction imposed by the Kramers-Kronig relation. The developed model has a broad range of applications for experimental data analysis and practical implementation in the design of devices involving a spatially nonuniform dielectric function, such as in biosensing, wave-guiding, solar energy harvesting, photonics and electro-optical devices.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kirby, Brent W.

The crucibles used currently for microwave melting of U-Mo alloy at the Y-12 Complex contain silicon carbide (SiC) in a mullite (3Al 2O 3-2SiO 2) matrix with an erbia coating in contact with the melt. Due to observed silicon contamination, Pacific Northwest National Laboratory has investigated alternative crucible materials that are susceptible to microwave radiation and are chemically compatible with molten U-Mo at 1400 1500C. Recommended crucibles for further testing are: 1) high-purity alumina (Al 2O 3); 2) yttria-stabilized zirconia (ZrO 2); 3) a composite of alumina and yttria-stabilized zirconia; 4) aluminum nitride (AlN). Only AlN does not require anmore » erbia coating. The recommended secondary susceptor, for heating at low temperature, is SiC in a “picket fence” arrangement.« less

Cleaning of nanopillar templates for nanoparticle collection using PDMS

NASA Astrophysics Data System (ADS)

Merzsch, S.; Wasisto, H. S.; Waag, A.; Kirsch, I.; Uhde, E.; Salthammer, T.; Peiner, E.

2011-05-01

Nanoparticles are easily attracted by surfaces. This sticking behavior makes it difficult to clean contaminated samples. Some complex approaches have already shown efficiencies in the range of 90%. However, a simple and cost efficient method was still missing. A commonly used silicone for soft lithography, PDMS, is able to mold a given surface. This property was used to cover surface-bonded particles from all other sides. After hardening the PDMS, particles are still embedded. A separation of silicone and sample disjoins also the particles from the surface. After this procedure, samples are clean again. This method was first tested with carbon particles on Si surfaces and Si pillar samples with aspect ratios up to 10. Experiments were done using 2 inch wafers, which, however, is not a size limitation for this method.

High-throughput preparation of complex multi-scale patterns from block copolymer/homopolymer blend films

NASA Astrophysics Data System (ADS)

Park, Hyungmin; Kim, Jae-Up; Park, Soojin

2012-02-01

A simple, straightforward process for fabricating multi-scale micro- and nanostructured patterns from polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP)/poly(methyl methacrylate) (PMMA) homopolymer in a preferential solvent for PS and PMMA is demonstrated. When the PS-b-P2VP/PMMA blend films were spin-coated onto a silicon wafer, PS-b-P2VP micellar arrays consisting of a PS corona and a P2VP core were formed, while the PMMA macrodomains were isolated, due to the macrophase separation caused by the incompatibility between block copolymer micelles and PMMA homopolymer during the spin-coating process. With an increase of PMMA composition, the size of PMMA macrodomains increased. Moreover, the P2VP blocks have a strong interaction with a native oxide of the surface of the silicon wafer, so that the P2VP wetting layer was first formed during spin-coating, and PS nanoclusters were observed on the PMMA macrodomains beneath. Whereas when a silicon surface was modified with a PS brush layer, the PS nanoclusters underlying PMMA domains were not formed. The multi-scale patterns prepared from copolymer micelle/homopolymer blend films are used as templates for the fabrication of gold nanoparticle arrays by incorporating the gold precursor into the P2VP chains. The combination of nanostructures prepared from block copolymer micellar arrays and macrostructures induced by incompatibility between the copolymer and the homopolymer leads to the formation of complex, multi-scale surface patterns by a simple casting process.A simple, straightforward process for fabricating multi-scale micro- and nanostructured patterns from polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP)/poly(methyl methacrylate) (PMMA) homopolymer in a preferential solvent for PS and PMMA is demonstrated. When the PS-b-P2VP/PMMA blend films were spin-coated onto a silicon wafer, PS-b-P2VP micellar arrays consisting of a PS corona and a P2VP core were formed, while the PMMA macrodomains were isolated, due to the macrophase separation caused by the incompatibility between block copolymer micelles and PMMA homopolymer during the spin-coating process. With an increase of PMMA composition, the size of PMMA macrodomains increased. Moreover, the P2VP blocks have a strong interaction with a native oxide of the surface of the silicon wafer, so that the P2VP wetting layer was first formed during spin-coating, and PS nanoclusters were observed on the PMMA macrodomains beneath. Whereas when a silicon surface was modified with a PS brush layer, the PS nanoclusters underlying PMMA domains were not formed. The multi-scale patterns prepared from copolymer micelle/homopolymer blend films are used as templates for the fabrication of gold nanoparticle arrays by incorporating the gold precursor into the P2VP chains. The combination of nanostructures prepared from block copolymer micellar arrays and macrostructures induced by incompatibility between the copolymer and the homopolymer leads to the formation of complex, multi-scale surface patterns by a simple casting process. Electronic supplementary information (ESI) available: AFM images of PS-b-P2VP/PMMA blend films and cross-sectional line scans. See DOI: 10.1039/c2nr11792d

Coupling molecular catalysts with nanostructured surfaces for efficient solar fuel production

NASA Astrophysics Data System (ADS)

Jin, Tong

Solar fuel generation via carbon dioxide (CO2) reduction is a promising approach to meet the increasing global demand for energy and to minimize the impact of energy consumption on climate change. However, CO2 is thermodynamically stable; its activation often requires the use of appropriate catalysts. In particular, molecular catalysts with well-defined structures and tunability have shown excellent activity in photochemical CO2 reduction. These homogenous catalysts, however, suffer from poor stability under photochemical conditions and difficulty in recycling from the reaction media. Heterogenized molecular catalysts, particularly those prepared by coupling molecular catalysts with solid-state surfaces, have attracted more attention in recent years as potential solutions to address the issues associated with molecular catalysts. In this work, solar CO2 reduction is investigated using systems coupling molecular catalysts with robust nanostructured surfaces. In Chapter 2, heterogenization of macrocyclic cobalt(III) and nickel (II) complexes on mesoporous silica surface was achieved by different methods. Direct ligand derivatization significantly lowered the catalytic activity of Co(III) complex, while grafting the Co(III) complex onto silica surface through Si-O-Co linkage resulted in hybrid catalysts with excellent activity in CO2 reduction in the presence of p-terphenyl as a molecular photosensitizer. An interesting loading effect was observed, in which the optimal activity was achieved at a medium Co(III) surface density. Heterogenization of the Ni(II) complex on silica surface has also been implemented, the poor photocatalytic activity of the hybrid catalyst can be attributed to the intrinsic nature of the homogeneous analogue. This study highlighted the importance of appropriate linking strategies in preparing functional heterogenized molecular catalysts. Coupling molecular complexes with light-harvesting surfaces could avoid the use of expensive molecular photosensitizers. In Chapter 3, effective coupling of the macrocyclic Co(III) complex with titanium dioxide (TiO¬2) nanoparticles was achieved by two deposition methods. The synthesized hybrid photocatalysts were thoroughly characterized with a variety of techniques. Upon UV light irradiation, photoexcited electrons in TiO2 nanoparticles were transferred to the surface Co(III) catalyst for CO2 reduction. Production of carbon monoxide (CO) from CO2 was confirmed by isotope labeling combined with infrared spectroscopy. Deposition of the Co(III) catalyst through Ti-O-Co linkages was essential for the photo-induced electron transfer and CO2-reduction activity using the hybrid photocatalysts. In Chapter 4, molecular Re(I) and Co(II) catalysts were coupled with silicon-based photoelectrodes, including a silicon nanowire (SiNW) photoelectrode, to achieve photoelectrochemical CO2 reduction. Photovoltages between 300-600 mV were obtained using the molecular catalysts on the silicon photoelectrodes. SiNWs exhibited enhanced properties, including significantly higher photovoltages than a planar silicon photoelectrode, the ability to protect one of the molecular catalysts from photo-induced decomposition, and excellent selectivity towards CO production in CO2 reduction. Recent theoretical and experimental work have demonstrated low-energy, binuclear pathways for CO2-to-CO conversion using several molecular catalysts. In such binuclear pathways, two metal centers work cooperatively to achieve two-electron CO2 reduction. Chapter 5 describes our effort to promote the binuclear pathway by grafting the molecular Co(III) catalyst onto silica surfaces. Different linking strategies were attempted to achieve this goal by planting the surface Co(III) sites in close proximity.

Silicon Compilation: A Solution to the Complexity of VLSI (Very Large-Scale Integrated) Circuit Design.

DTIC Science & Technology

1985-09-01

Design Language Xi." International Conference on Computer Design, pp. 652-655. 1983. [GAJ 84] D. D. Gajski and J. J. Bozek. "ARSENIC: Methodology and...Report R-1015 UIUL-ENG 84-2209. August 1984. [LUR 84] C. Lursinsap and D. Gajski , "Cell Compilation with Constraints." Proceedings of the 21st Design

Robust Joining and Integration of Advanced Ceramics and Composites: Challenges, Opportunities, and Realities

NASA Technical Reports Server (NTRS)

Singh, Mrityunjay

2006-01-01

Advanced ceramics and fiber reinforced composites are under active consideration for use in a wide variety of high temperature applications within the aeronautics, space transportation, energy, and nuclear industries. The engineering designs of ceramic and composite components require fabrication and manufacturing of large and complex shaped parts of various thicknesses. In many instances, it is more economical to build up complex shapes by joining simple geometrical shapes. In addition, these components have to be joined or assembled with metallic sub-components. Thus, joining and attachment have been recognized as enabling technologies for successful utilization of ceramic components in various demanding applications. In this presentation, various challenges and opportunities in design, fabrication, and testing of high temperature joints in advanced ceramics and ceramic matrix composites will be presented. Silicon carbide based advanced ceramics and fiber reinforced composites in different shapes and sizes, have been joined using an affordable, robust ceramic joining technology. In addition, some examples of metal-ceramic brazing will also be presented. Microstructure and high temperature mechanical properties of joints in silicon carbide ceramics and composites will be reported. Various joint design philosophies and design issues in joining of ceramics and composites will be discussed.

Er 3+ Doping conditions of planar porous silicon waveguides

NASA Astrophysics Data System (ADS)

Najar, A.; Lorrain, N.; Ajlani, H.; Charrier, J.; Oueslati, M.; Haji, L.

2009-11-01

EDX and infrared photoluminescence (IR PL) analyses performed on erbium-doped porous silicon waveguides (PSWG) were studied using different doping conditions. Both parameters of the cathodisation electrochemical method used for Er incorporation and parameters of thermal treatments required for Er optical activation were taken into consideration. Firstly, by varying the current density and the time of cathodisation, we have shown that a current density of 0.1 mA/cm 2 for 10 min allows homogeneous Er doping to be achieved throughout the depth of the guiding layer. Then, the PL intensity at 1.53 μm was studied as a function of the oxidation time at 900 °C and Er diffusion temperature for 60 min. Increasing the oxidation time up to 1 h allows PL to be enhanced due to active Si-O-Er complex formation whereas an oxidation time of 2 h induces a decrease in PL because of Er segregation. Moreover, an increase in the diffusion temperature induces an optimal distribution of optically active Si-Er-O complexes inside the crystallites. When the temperature is too high, a PSWG densification and Er segregation occurs inducing a decrease in PL due to energy transfer phenomena.

Atomic scale origins of sub-band gap optical absorption in gold-hyperdoped silicon

NASA Astrophysics Data System (ADS)

Ferdous, Naheed; Ertekin, Elif

2018-05-01

Gold hyperdoped silicon exhibits room temperature sub band gap optical absorption, with potential applications as infrared absorbers/detectors and impurity band photovoltaics. We use first-principles density functional theory to establish the origins of the sub band gap response. Substitutional gold AuSi and substitutional dimers AuSi - AuSi are found to be the energetically preferred defect configurations, and AuSi gives rise to partially filled mid-gap defect bands well offset from the band edges. AuSi is predicted to offer substantial sub-band gap absorption, exceeding that measured in prior experiments by two orders of magnitude for similar Au concentration. This suggests that in experimentally realized systems, in addition to AuSi, the implanted gold is accommodated by the lattice in other ways, including other defect complexes and gold precipitates. We further identify that it is energetically favorable for isolated AuSi to form AuSi - AuSi, which by contrast do not exhibit mid-gap states. The formation of dimers and other complexes could serve as nuclei in the earliest stages of Au precipitation, which may be responsible for the observed rapid deactivation of sub-band gap response upon annealing.

The birth of a quasiparticle in silicon observed in time-frequency space.

PubMed

Hase, Muneaki; Kitajima, Masahiro; Constantinescu, Anca Monia; Petek, Hrvoje

2003-11-06

The concept of quasiparticles in solid-state physics is an extremely powerful tool for describing complex many-body phenomena in terms of single-particle excitations. Introducing a simple particle, such as an electron, hole or phonon, deforms a many-body system through its interactions with other particles. In this way, the added particle is 'dressed' or 'renormalized' by a self-energy cloud that describes the response of the many-body system, so forming a new entity--the quasiparticle. Using ultrafast laser techniques, it is possible to impulsively generate bare particles and observe their subsequent dressing by the many-body interactions (that is, quasiparticle formation) on the time and energy scales governed by the Heisenberg uncertainty principle. Here we describe the coherent response of silicon to excitation with a 10-femtosecond (10(-14) s) laser pulse. The optical pulse interacts with the sample by way of the complex second-order nonlinear susceptibility to generate a force on the lattice driving coherent phonon excitation. Transforming the transient reflectivity signal into frequency-time space reveals interference effects leading to the coherent phonon generation and subsequent dressing of the phonon by electron-hole pair excitations.

Comparison of different substrates for laser-induced electron transfer desorption/ionization of metal complexes

NASA Astrophysics Data System (ADS)

Grechnikov, A. A.; Georgieva, V. B.; Donkov, N.; Borodkov, A. S.; Pento, A. V.; Raicheva, Z. G.; Yordanov, Tc A.

2016-03-01

Four different substrates, namely, graphite, tungsten, amorphous silicon (α-Si) and titanium dioxide (TiO2) films, were compared in view of the laser-induced electron transfer desorption/ionization (LETDI) of metal coordination complexes. A rhenium complex with 8-mercaptoquinoline, a copper complex with diphenylthiocarbazone and chlorophyll A were studied as the test analytes. The dependencies of the ion yield and the surface temperature on the incident radiation fluence were investigated experimentally and theoretically. The temperature was estimated using the numerical solution of a one-dimensional heat conduction problem with a heat source distributed in time and space. It was found that at the same temperature, the ion yield from the different substrates varies in the range of three orders of magnitude. The direct comparison of all studied substrates revealed that LETDI from the TiO2 and α-Si films offer a better choice for producing molecular ions of metal coordination complexes.

Infrared Imaging of Carbon and Ceramic Composites: Data Reproducibility

NASA Astrophysics Data System (ADS)

Knight, B.; Howard, D. R.; Ringermacher, H. I.; Hudson, L. D.

2010-02-01

Infrared NDE techniques have proven to be superior for imaging of flaws in ceramic matrix composites (CMC) and carbon silicon carbide composites (C/SiC). Not only can one obtain accurate depth gauging of flaws such as delaminations and layered porosity in complex-shaped components such as airfoils and other aeronautical components, but also excellent reproducibility of image data is obtainable using the STTOF (Synthetic Thermal Time-of-Flight) methodology. The imaging of large complex shapes is fast and reliable. This methodology as applied to large C/SiC flight components at the NASA Dryden Flight Research Center will be described.

Neuromorphic VLSI vision system for real-time texture segregation.

PubMed

Shimonomura, Kazuhiro; Yagi, Tetsuya

2008-10-01

The visual system of the brain can perceive an external scene in real-time with extremely low power dissipation, although the response speed of an individual neuron is considerably lower than that of semiconductor devices. The neurons in the visual pathway generate their receptive fields using a parallel and hierarchical architecture. This architecture of the visual cortex is interesting and important for designing a novel perception system from an engineering perspective. The aim of this study is to develop a vision system hardware, which is designed inspired by a hierarchical visual processing in V1, for real time texture segregation. The system consists of a silicon retina, orientation chip, and field programmable gate array (FPGA) circuit. The silicon retina emulates the neural circuits of the vertebrate retina and exhibits a Laplacian-Gaussian-like receptive field. The orientation chip selectively aggregates multiple pixels of the silicon retina in order to produce Gabor-like receptive fields that are tuned to various orientations by mimicking the feed-forward model proposed by Hubel and Wiesel. The FPGA circuit receives the output of the orientation chip and computes the responses of the complex cells. Using this system, the neural images of simple cells were computed in real-time for various orientations and spatial frequencies. Using the orientation-selective outputs obtained from the multi-chip system, a real-time texture segregation was conducted based on a computational model inspired by psychophysics and neurophysiology. The texture image was filtered by the two orthogonally oriented receptive fields of the multi-chip system and the filtered images were combined to segregate the area of different texture orientation with the aid of FPGA. The present system is also useful for the investigation of the functions of the higher-order cells that can be obtained by combining the simple and complex cells.

Deep-level transient spectroscopy of Pd-H complexes in silicon

NASA Astrophysics Data System (ADS)

Sachse, J.-U.; Weber, J.; Lemke, H.

2000-01-01

The interaction of atomic hydrogen with substitutional palladium impurities is studied in n- and p-type Si by deep-level transient spectroscopy. After wet-chemical etching, we determine seven different electrically active and at least one passive palladium hydrogen complex. The levels belong to Pd complexes with different number of hydrogen atoms. The PdH1 complex exhibits one level E(200) at EC-0.43 eV. PdH2 has two levels E(60) at EC-0.10 eV and H(280) at EV+0.55 eV. Four levels are assigned to the PdH3 complex E(160) at EC-0.29 eV, H(140) at EV+0.23 eV, H(55) at EV+0.08 eV, and H(45) at EV+0.07 eV. An electrically passive complex is associated with a PdH4 complex. There is great similarity with the correspondent complexes in Pt-doped Si. Annealing above 650 K destroys all hydrogen related complexes and restores the original substitutional Pd concentration.

A Infrared Absorption Study of Dopant-Hydrogen Complexes in Semiconductors

NASA Astrophysics Data System (ADS)

Kozuch, David Michael

1992-01-01

Hydrogen passivation of shallow electrical dopants in semiconductors has been investigated. In particular, the passivation of the shallow dopants tin, carbon, and silicon in gallium arsenide has been studied via Fourier transform infrared spectroscopy, thermal annealing, Hall effect, secondary ion mass spectroscopy, and uniaxial stress. The bond-stretching and bond-wagging vibrational modes of the rm Sn_{Ga} - H complex in GaAs have been identified at 1327.8 cm^{-1} and 967.7 cm ^{-1}, respectively. The presence of hydrogen in the defect pair is confirmed by the deuterium -shifted bond-stretching signal at 746.6 cm^ {-1}. Infrared and Hall data correlated the passivation of Sn_{rm Ga } donors with the formation of the rm Sn_{Ga} - H complexes. A series of isochronal anneals probed the thermal stability of the complex. Arguments supporting an antibonding configuration for the rm Sn_{Ga} - H complex are presented. Infrared measurements on highly carbon doped epi -layers reveal new absorption signals at 2643, 2651, and 2688 cm^{-1} in addition to the previously identified rm C_ {As} - H stretching vibration at 2636 cm^{-1}. These new signals are related to a family of carbon-hydrogen complexes: rm C_{x} - H. Deuterium -shifted counterparts for all these signals have been observed for the first time. Sources of hydrogen have been traced to the metalorganic precursors and carrier gas used during epi-layer growth. Hydrogen-containing annealing ambients were surprisingly effective for introducing hydrogen into the epi-layers. Several atomic arrangements for the new rm C_{x} - H complexes have been considered with the most likely candidate being a rm C_{As} - H complex perturbed by another C_{rm As} acceptor in a second nearest neighbor position. The first uniaxial stress measurements have been performed on the rm Si_{As} - H complex in GaAs. The stress-induced frequency shifts and the intensity ratios of the stress-split components of the 2094.45 cm^{-1} stretching frequency reveal that the complex has trigonal symmetry. Reorientation of the stress-aligned complexes occurred by thermally activated jumps of the hydrogen atom with an activation energy of E_{rm A} = 0.26 eV. The piezospectroscopic tensor of the rm Si_{As} - H complex has been determined. The similarities between the stress data for the rm Si_{As } - H complex and the well-studied B - H complex in silicon suggest a bond-centered configuration for the rm Si_{As} - H defect pair.

Wear forms of heterogeneous electro-rheological fluids working in a hydraulic clutch system

NASA Astrophysics Data System (ADS)

Ziabska, E.; Duchowski, J.; Olszak, A.; Osowski, K.; Kesy, A.; Kesy, Z.; Choi, S. B.

2017-09-01

The paper presents experimental results concerning the wear of heterogeneous electro-rheological (ER) fluids operating as working fluids in a complex clutch system consisting of a hydrodynamic clutch and a cylinder viscous clutch. The change of electric field intensity in the clutches results in change of sheer stress values in working fluids what causes the change of transmitted torque. This work shows that the most important factors affecting the wear of the ER fluid are the electric field of high intensity, the accompanying electrical breakdown, and the high temperature of the silicone oil. In addition, the water from the humid air absorbed mainly by hygroscopic particles influences a significant impact on the wear of the working fluid. Various forms of wear particles of the fluid depending on the prevailing conditions such as working mode are observed from the microscopic aspects. It is observed that the particles are flattened, rolled out or smashed into smaller fragments, partially melted, wrinkled and glued or caked. In addition, it is identified that the partial destruction of silicone oil is occurred due to the damage of the hydrocarbon chains, as evidenced by the decrease in its viscosity and the presence of the particle matter newly containing silicon.

Vertical silicon nanowires as a universal platform for delivering biomolecules into living cells

PubMed Central

Shalek, Alex K.; Robinson, Jacob T.; Karp, Ethan S.; Lee, Jin Seok; Ahn, Dae-Ro; Yoon, Myung-Han; Sutton, Amy; Jorgolli, Marsela; Gertner, Rona S.; Gujral, Taranjit S.; MacBeath, Gavin; Yang, Eun Gyeong; Park, Hongkun

2010-01-01

A generalized platform for introducing a diverse range of biomolecules into living cells in high-throughput could transform how complex cellular processes are probed and analyzed. Here, we demonstrate spatially localized, efficient, and universal delivery of biomolecules into immortalized and primary mammalian cells using surface-modified vertical silicon nanowires. The method relies on the ability of the silicon nanowires to penetrate a cell’s membrane and subsequently release surface-bound molecules directly into the cell’s cytosol, thus allowing highly efficient delivery of biomolecules without chemical modification or viral packaging. This modality enables one to assess the phenotypic consequences of introducing a broad range of biological effectors (DNAs, RNAs, peptides, proteins, and small molecules) into almost any cell type. We show that this platform can be used to guide neuronal progenitor growth with small molecules, knock down transcript levels by delivering siRNAs, inhibit apoptosis using peptides, and introduce targeted proteins to specific organelles. We further demonstrate codelivery of siRNAs and proteins on a single substrate in a microarray format, highlighting this technology’s potential as a robust, monolithic platform for high-throughput, miniaturized bioassays. PMID:20080678

Thermo-mechanical performance of precision C/SiC mounts

NASA Astrophysics Data System (ADS)

Goodman, William A.; Mueller, Claus E.; Jacoby, Marc T.; Wells, Jim D.

2001-12-01

For complex shaped, lightweight, high precision opto- mechanical structures that must operate in adverse environments and over wide ranges of temperature, we consider IABG's optical grade silicon carbide composite ceramic (C/SiC) as the material of choice. C/SiC employs conventional NC machining/milling equipment to rapidly fabricate near-net shape parts, providing substantial schedule, cost, and risk savings for high precision components. Unlike powder based SiC ceramics, C/SiC does not experience significant shrinkage during processing, nor does it suffer from incomplete densification. If required, e.g. for large-size components, a fully-monolithic ceramic joining technique can be applied. Generally, the thermal and mechanical properties of C/SiC are tunable in certain ranges by modifying certain process steps. This paper focuses on the thermo-mechanical performance of new, high precision mounts designed by Schafer Corporation and manufactured by IABG. The mounts were manufactured using standard optical grade C/SiC (formulation internally called A-3). The A-3 formulation has a near-perfect CTE match with silicon, making it the ideal material to athermally support Schafer produced Silicon Lightweight Mirrors (SLMs) that will operate in a cryogenic environment. Corresponding thermo- mechanical testing and analysis is presented in this manuscript.

Polycation-Functionalized Nanoporous Silicon Particles for Gene Silencing on Breast Cancer Cells

PubMed Central

Zhang, Mingzhen; Xu, Rong; Xia, Xiaojun; Yang, Yong; Gu, Jianhua; Qin, Guoting; Liu, Xuewu; Ferrari, Mauro; Shen, Haifa

2013-01-01

Nanoporous silicon particles (pSi), with a pore size in the range of 20~60 nm, were modified with polyethyleimine (PEI) to yield pSi-PEI particles, which were subsequently complexed with siRNA. Thus, pSi-PEI/siRNA particles were fabricated, with the PEI/siRNA nanocomplexes mainly anchored inside the nanopore of the pSi particles. These hybrid particles were used as carriers to deliver siRNA to human breast cancer cells. Due to the gradual degradation of the pSi matrix under physiological conditions, the PEI/siRNA nanocomplexes were released from the pore interior in a sustained manner. Physicochemical characterization revealed that the released PEI/siRNA nanocomplexes exhibited well-defined spherical shape and narrow particle size distribution between 15 and 30 nm. Gene knockdown against the ataxia telangiectasia mutated (ATM) cancer gene showed dramatic gene silencing efficacy. Moreover, comprehensive biocompatibility studies were performed for the pSi-PEI/siRNA particles both in vitro and in vivo and demonstrated that the pSi-PEI particles exhibited significantly enhanced biocompatibility. As a consequence, PEI-modified porous silicon particles may have substantial potential as safe and effective siRNA delivery systems. PMID:24103653

Oxygen-related vacancy-type defects in ion-implanted silicon

NASA Astrophysics Data System (ADS)

Pi, X. D.; Burrows, C. P.; Coleman, P. G.; Gwilliam, R. M.; Sealy, B. J.

2003-10-01

Czochralski silicon samples implanted to a dose of 5 × 1015 cm-2 with 0.5 MeV O and to a dose of 1016 cm-2 with 1 MeV Si, respectively, have been studied by positron annihilation spectroscopy. The evolution of divacancies to vacancy (V)-O complexes is out-competed by V-interstitial (I) recombination at 400 and 500 °C in the Si- and O-implanted samples; the higher oxygen concentration makes the latter temperature higher. The defective region shrinks as the annealing temperature increases as interstitials are injected from the end of the implantation range (Rp). VmOn (m> n) are formed in the shallow region most effectively at 700 °C for both Si and O implantation. VxOy (x< y) are produced near Rp by the annealing. At 800 °C, implanted Si ions diffuse and reduce m and implanted O ions diffuse and increase n in VmOn. All oxygen-related vacancy-type defects appear to begin to dissociate at 950 °C, with the probable formation of oxygen clusters. At 1100 °C, oxygen precipitates appear to form just before Rp in O-implanted silicon.

Output factor determination for dose measurements in axial and perpendicular planes using a silicon strip detector

NASA Astrophysics Data System (ADS)

Abou-Haïdar, Z.; Bocci, A.; Alvarez, M. A. G.; Espino, J. M.; Gallardo, M. I.; Cortés-Giraldo, M. A.; Ovejero, M. C.; Quesada, J. M.; Arráns, R.; Prieto, M. Ruiz; Vega-Leal, A. Pérez; Nieto, F. J. Pérez

2012-04-01

In this work we present the output factor measurements of a clinical linear accelerator using a silicon strip detector coupled to a new system for complex radiation therapy treatment verification. The objective of these measurements is to validate the system we built for treatment verification. The measurements were performed at the Virgin Macarena University Hospital in Seville. Irradiations were carried out with a Siemens ONCOR™ linac used to deliver radiotherapy treatment for cancer patients. The linac was operating in 6 MV photon mode; the different sizes of the fields were defined with the collimation system provided within the accelerator head. The output factor was measured with the silicon strip detector in two different layouts using two phantoms. In the first, the active area of the detector was placed perpendicular to the beam axis. In the second, the innovation consisted of a cylindrical phantom where the detector was placed in an axial plane with respect to the beam. The measured data were compared with data given by a commercial treatment planning system. Results were shown to be in a very good agreement between the compared set of data.

Silicon with an increased content of monoatomic sulfur centers: Sample fabrication and optical spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Astrov, Yu. A., E-mail: yuri.astrov@mail.ioffe.ru; Lynch, S. A.; Shuman, V. B.

2013-02-15

The effect of the high-temperature heating (at 1340 Degree-Sign C) of sulfur-doped silicon samples and their subsequent quenching is studied. The results of such a treatment are analyzed on the basis of Hall-effect data obtained in the temperature range T = 78-500 K. It is shown that the heating duration strongly affects the relative concentrations of different types of deep sulfur-related centers. At comparatively short heating durations of t = 2-10 min, the concentration of quasi-molecular S{sub 2} centers and S{sub X} complexes substantially decreases, whereas the density of monoatomic S{sub 1} centers grows. At the same time, the heatingmore » of a sample is accompanied by a monotonic decrease in the total concentration of electrically active sulfur over time. The results obtained make it possible to give recommendations concerning the optimal conditions for the fabrication of samples with a high concentration of S{sub 1} centers. The absorption spectra of the samples show that the method is promising for the observation of a number of quantum-optical effects involving deep S{sub 1} donors in silicon.« less

Anisotropy of Single-Crystal Silicon in Nanometric Cutting.

PubMed

Wang, Zhiguo; Chen, Jiaxuan; Wang, Guilian; Bai, Qingshun; Liang, Yingchun

2017-12-01

The anisotropy exhibited by single-crystal silicon in nanometric cutting is very significant. In order to profoundly understand the effect of crystal anisotropy on cutting behaviors, a large-scale molecular dynamics model was conducted to simulate the nanometric cutting of single-crystal silicon in the (100)[0-10], (100)[0-1-1], (110)[-110], (110)[00-1], (111)[-101], and (111)[-12-1] crystal directions in this study. The simulation results show the variations of different degrees in chip, subsurface damage, cutting force, and friction coefficient with changes in crystal plane and crystal direction. Shear deformation is the formation mechanism of subsurface damage, and the direction and complexity it forms are the primary causes that result in the anisotropy of subsurface damage. Structurally, chips could be classified into completely amorphous ones and incompletely amorphous ones containing a few crystallites. The formation mechanism of the former is high-pressure phase transformation, while the latter is obtained under the combined action of high-pressure phase transformation and cleavage. Based on an analysis of the material removal mode, it can be found that compared with the other crystal direction on the same crystal plane, the (100)[0-10], (110)[-110], and (111)[-101] directions are more suitable for ductile cutting.

Impurity and phonon scattering in silicon nanowires

NASA Astrophysics Data System (ADS)

Zhang, W.; Persson, M. P.; Mera, H.; Delerue, C.; Niquet, Y. M.; Allan, G.; Wang, E.

2011-03-01

We model the scattering of electrons by phonons and dopant impurities in ultimate [110]-oriented gate-all-around silicon nanowires with an atomistic valence force field and tight-binding approach. All electron-phonons interactions are included. We show that impurity scattering can reduce with decreasing nanowire diameter due to the enhanced screening by the gate. Donors and acceptors however perform very differently : acceptors behave as tunnel barriers for the electrons, while donors behave as quantum wells which introduce Fano resonances in the conductance. As a consequence the acceptors are much more limiting the mobility than the donors. The resistances of single acceptors are also very dependent on their radial position in the nanowire, which might be a significant source of variability in ultimate silicon nanowire devices. Concerning phonons, we show that, as a result of strong confinement, i) electrons couple to a wide and complex distribution of phonons modes, and ii) the mobility has a non-monotonic variation with wire diameter and is strongly reduced with respect to bulk. French National Research Agency ANR project QUANTAMONDE Contract No. ANR-07-NANO-023-02 and by the Délégation Générale pour l'Armement, French Ministry of Defense under Grant No. 2008.34.0031.

Realization of a Hole-Doped Mott Insulator on a Triangular Silicon Lattice

NASA Astrophysics Data System (ADS)

Ming, Fangfei; Johnston, Steve; Mulugeta, Daniel; Smith, Tyler S.; Vilmercati, Paolo; Lee, Geunseop; Maier, Thomas A.; Snijders, Paul C.; Weitering, Hanno H.

2017-12-01

The physics of doped Mott insulators is at the heart of some of the most exotic physical phenomena in materials research including insulator-metal transitions, colossal magnetoresistance, and high-temperature superconductivity in layered perovskite compounds. Advances in this field would greatly benefit from the availability of new material systems with a similar richness of physical phenomena but with fewer chemical and structural complications in comparison to oxides. Using scanning tunneling microscopy and spectroscopy, we show that such a system can be realized on a silicon platform. The adsorption of one-third monolayer of Sn atoms on a Si(111) surface produces a triangular surface lattice with half filled dangling bond orbitals. Modulation hole doping of these dangling bonds unveils clear hallmarks of Mott physics, such as spectral weight transfer and the formation of quasiparticle states at the Fermi level, well-defined Fermi contour segments, and a sharp singularity in the density of states. These observations are remarkably similar to those made in complex oxide materials, including high-temperature superconductors, but highly extraordinary within the realm of conventional s p -bonded semiconductor materials. It suggests that exotic quantum matter phases can be realized and engineered on silicon-based materials platforms.

Laser-induced Greenish-Blue Photoluminescence of Mesoporous Silicon Nanowires

PubMed Central

Choi, Yan-Ru; Zheng, Minrui; Bai, Fan; Liu, Junjun; Tok, Eng-Soon; Huang, Zhifeng; Sow, Chorng-Haur

2014-01-01

Solid silicon nanowires and their luminescent properties have been widely studied, but lesser is known about the optical properties of mesoporous silicon nanowires (mp-SiNWs). In this work, we present a facile method to generate greenish-blue photoluminescence (GB-PL) by fast scanning a focused green laser beam (wavelength of 532 nm) on a close-packed array of mp-SiNWs to carry out photo-induced chemical modification. The threshold of laser power is 5 mW to excite the GB-PL, whose intensity increases with laser power in the range of 5–105 mW. The quenching of GB-PL comes to occur beyond 105 mW. The in-vacuum annealing effectively excites the GB-PL in the pristine mp-SiNWs and enhances the GB-PL of the laser-modified mp-SiNWs. A complex model of the laser-induced surface modification is proposed to account for the laser-power and post-annealing effect. Moreover, the fast scanning of focused laser beam enables us to locally tailor mp-SiNWs en route to a wide variety of micropatterns with different optical functionality, and we demonstrate the feasibility in the application of creating hidden images. PMID:24820533

Nucleophilic substitution at silicon (SN2@Si) via a central reaction barrier.

PubMed

Bento, A Patrícia; Bickelhaupt, F Matthias

2007-03-16

It is textbook knowledge that nucleophilic substitution at carbon (SN2@C) proceeds via a central reaction barrier which disappears in the corresponding nucleophilic substitution reaction at silicon (SN2@Si). Here, we address the question why the central barrier disappears from SN2@C to SN2@Si despite the fact that these processes are isostructural and isoelectronic. To this end, we have explored and analyzed the potential energy surfaces (PES) of various Cl-+CR3Cl (R=H, CH3) and Cl-+SiR3Cl model reactions (R=H, CH3, C2H5, and OCH3). Our results show that the nature of the SN2 reaction barrier is in essence steric, but that it can be modulated by electronic factors. Thus, simply by increasing the steric demand of the substituents R around the silicon atom, the SN2@Si mechanism changes from its regular single-well PES (with a stable intermediate transition complex, TC), via a triple-well PES (with a pre- and a post-TS before and after the central TC), to a double-well PES (with a TS; R=OCH3), which is normally encountered for SN2@C reactions.

Investigation of a combined platinum and electron lifetime control treatment for silicon

NASA Astrophysics Data System (ADS)

Jia, Yunpeng; Cui, Zhihang; Yang, Fei; Zhao, Bao; Zou, Shikai; Liang, Yongsheng

2017-02-01

In silicon, the effect of Combined Lifetime Treatment (CLT) involving platinum diffusion and subsequent electron irradiation is different from the separate treatments of platinum diffusion and electron irradiation, even the treatment of electron irradiation followed by platinum diffusion. In this paper, we investigated the experimental behavior of different kinds of lifetime treated samples. We found that the reverse leakage current (Irr) increases with the increasing platinum diffusion temperature or electron irradiation dose in the separate treatments. Conversely, Irr of the CLT samples decreased with rising platinum diffusion temperature at the same dose of subsequent electron irradiation. By deep-level transient spectroscopy (DLTS), a new energy level E7 (Ec -0.376 eV) was found in our CLT samples. The new level E7 suppresses the dominance of the deeper level E8 (Ec -0.476 eV), which is caused by electron irradiation directly and results in Irr's increase. The formation of the level E7 comes from the complex defect-combined effect between platinum atoms and silicon vacancies, and it affects device's characteristics finally. These research will be helpful to the development of platinum-diffused devices used in intense electron irradiation environments.

How the new optoelectronic design automation industry is taking advantage of preexisting EDA standards

NASA Astrophysics Data System (ADS)

Nesmith, Kevin A.; Carver, Susan

2014-05-01

With the advancements in design processes down to the sub 7nm levels, the Electronic Design Automation industry appears to be coming to an end of advancements, as the size of the silicon atom becomes the limiting factor. Or is it? The commercial viability of mass-producing silicon photonics is bringing about the Optoelectronic Design Automation (OEDA) industry. With the science of photonics in its infancy, adding these circuits to ever-increasing complex electronic designs, will allow for new generations of advancements. Learning from the past 50 years of the EDA industry's mistakes and missed opportunities, the photonics industry is starting with electronic standards and extending them to become photonically aware. Adapting the use of pre-existing standards into this relatively new industry will allow for easier integration into the present infrastructure and faster time to market.

Investigation of the hydrochlorination of SiCl4

NASA Technical Reports Server (NTRS)

Mui, J. Y. P.

1983-01-01

A basic, experimental study on the hydrochlorination of silicon tetrachloride and metallurgical grade silicon with hydrogen gas to form trichlorosilane was carried out to greatly expand the range of reaction conditions. The equilibrium constant, K sub p, for the hydrochlorination reaction was measured as a function of temperature, pressure and concentration. The variation of the equilibrium constant as a function of temperature provided the measurement on the heat of reaction, delta H, by the Second Law Method. The value of delta H was measured to give 10.6 Kcal/mole. The equilibrium constant was also studied as a function of concentration. In agreement with the theory, the equilibrium constant remained constant with respect to the varying H2/SiCl4 feed ratios. On the other hand, the effect of pressure on the equilibrium constant was found to be more complex.

Two different carbon-hydrogen complexes in silicon with closely spaced energy levels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stübner, R., E-mail: ronald.stuebner@physik.tu-dresden.de, E-mail: kolkov@ifpan.edu.pl; Kolkovsky, Vl., E-mail: ronald.stuebner@physik.tu-dresden.de, E-mail: kolkov@ifpan.edu.pl; Weber, J.

An acceptor and a single donor state of carbon-hydrogen defects (CH{sub A} and CH{sub B}) are observed by Laplace deep level transient spectroscopy at 90 K. CH{sub A} appears directly after hydrogenation by wet chemical etching or hydrogen plasma treatment, whereas CH{sub B} can be observed only after a successive annealing under reverse bias at about 320 K. The activation enthalpies of these states are 0.16 eV for CH{sub A} and 0.14 eV for CH{sub B}. Our results reconcile previous controversial experimental results. We attribute CH{sub A} to the configuration where substitutional carbon binds a hydrogen atom on a bond centered position between carbonmore » and the neighboring silicon and CH{sub B} to another carbon-hydrogen defect.« less

Lightwave Circuits in Lithium Niobate through Hybrid Waveguides with Silicon Photonics

PubMed Central

Weigel, Peter O.; Savanier, Marc; DeRose, Christopher T.; Pomerene, Andrew T.; Starbuck, Andrew L.; Lentine, Anthony L.; Stenger, Vincent; Mookherjea, Shayan

2016-01-01

We demonstrate a photonic waveguide technology based on a two-material core, in which light is controllably and repeatedly transferred back and forth between sub-micron thickness crystalline layers of Si and LN bonded to one another, where the former is patterned and the latter is not. In this way, the foundry-based wafer-scale fabrication technology for silicon photonics can be leveraged to form lithium-niobate based integrated optical devices. Using two different guided modes and an adiabatic mode transition between them, we demonstrate a set of building blocks such as waveguides, bends, and couplers which can be used to route light underneath an unpatterned slab of LN, as well as outside the LN-bonded region, thus enabling complex and compact lightwave circuits in LN alongside Si photonics with fabrication ease and low cost. PMID:26927022

Lightwave Circuits in Lithium Niobate through Hybrid Waveguides with Silicon Photonics.

PubMed

Weigel, Peter O; Savanier, Marc; DeRose, Christopher T; Pomerene, Andrew T; Starbuck, Andrew L; Lentine, Anthony L; Stenger, Vincent; Mookherjea, Shayan

2016-03-01

We demonstrate a photonic waveguide technology based on a two-material core, in which light is controllably and repeatedly transferred back and forth between sub-micron thickness crystalline layers of Si and LN bonded to one another, where the former is patterned and the latter is not. In this way, the foundry-based wafer-scale fabrication technology for silicon photonics can be leveraged to form lithium-niobate based integrated optical devices. Using two different guided modes and an adiabatic mode transition between them, we demonstrate a set of building blocks such as waveguides, bends, and couplers which can be used to route light underneath an unpatterned slab of LN, as well as outside the LN-bonded region, thus enabling complex and compact lightwave circuits in LN alongside Si photonics with fabrication ease and low cost.

Broadband enhancement of single photon emission and polarization dependent coupling in silicon nitride waveguides.

PubMed

Bisschop, Suzanne; Guille, Antoine; Van Thourhout, Dries; Hens, Zeger; Brainis, Edouard

2015-06-01

Single-photon (SP) sources are important for a number of optical quantum information processing applications. We study the possibility to integrate triggered solid-state SP emitters directly on a photonic chip. A major challenge consists in efficiently extracting their emission into a single guided mode. Using 3D finite-difference time-domain simulations, we investigate the SP emission from dipole-like nanometer-sized inclusions embedded into different silicon nitride (SiNx) photonic nanowire waveguide designs. We elucidate the effect of the geometry on the emission lifetime and the polarization of the emitted SP. The results show that highly efficient and polarized SP sources can be realized using suspended SiNx slot-waveguides. Combining this with the well-established CMOS-compatible processing technology, fully integrated and complex optical circuits for quantum optics experiments can be developed.

Synthesis of ZnS films on Si(100) wafers by using chemical bath deposition assisted by the complexing agent ethylenediamine

NASA Astrophysics Data System (ADS)

Zhu, He-Jie; Wang, Xue-Mei; Gao, Xiao-Yong

2015-07-01

Low-cost synthesis of high-quality ZnS films on silicon wafers is of much importance to the ZnSbased heterojunction blue light-emitting device integrated with silicon. Thus, a series of ZnS films were chemically synthesized at low cost on Si(100) wafers at 353 K under a mixed acidic solution with a pH of 4 with zinc acetate and thioacetamide as precursors and with ethylenediamine and hydrochloric acid as the complexing agent and the pH value modifier, respectively. The effects of the ethylenediamine concentration on the crystallization, surface morphology, and optical properties of the ZnS films were investigated by using X-ray diffractometry, scanning electron microscopy, spectrophotometry, and fluorescence spectroscopy. A mechanism for the formation of ZnS film under an acidic condition was also proposed. All of the ZnS films were polycrystalline in nature, with a dominant cubic phase and a small amounts of hexagonal phases. The crystallization and the surface pattern of the films were clearly improved with increasing ethylenediamine concentration due to its enhanced complexing role. The absorption edge of the films almost underwent a blue shift with increasing ethylenediamine concentration, which was largely attributed to the quantum confinement effects caused by the small particle size of the polycrystalline ZnS films. Defect species and the corresponding strengths of the ZnS films were strongly affected by the ethylenediamine concentration.

Molecular recognition on a cavitand-functionalized silicon surface.

PubMed

Biavardi, Elisa; Favazza, Maria; Motta, Alessandro; Fragalà, Ignazio L; Massera, Chiara; Prodi, Luca; Montalti, Marco; Melegari, Monica; Condorelli, Guglielmo G; Dalcanale, Enrico

2009-06-03

A Si(100) surface featuring molecular recognition properties was obtained by covalent functionalization with a tetraphosphonate cavitand (Tiiii), able to complex positively charged species. Tiiii cavitand was grafted onto the Si by photochemical hydrosilylation together with 1-octene as a spatial spectator. The recognition properties of the Si-Tiiii surface were demonstrated through two independent analytical techniques, namely XPS and fluorescence spectroscopy, during the course of reversible complexation-guest exchange-decomplexation cycles with specifically designed ammonium and pyridinium salts. Control experiments employing a Si(100) surface functionalized with a structurally similar, but complexation inactive, tetrathiophosphonate cavitand (TSiiii) demonstrated no recognition events. This provides evidence for the complexation properties of the Si-Tiiii surface, ruling out the possibility of nonspecific interactions between the substrate and the guests. The residual Si-O(-) terminations on the surface replace the guests' original counterions, thus stabilizing the complex ion pairs. These results represent a further step toward the control of self-assembly of complex supramolecular architectures on surfaces.

A unified approach to VLSI layout automation and algorithm mapping on processor arrays

NASA Technical Reports Server (NTRS)

Venkateswaran, N.; Pattabiraman, S.; Srinivasan, Vinoo N.

1993-01-01

Development of software tools for designing supercomputing systems is highly complex and cost ineffective. To tackle this a special purpose PAcube silicon compiler which integrates different design levels from cell to processor arrays has been proposed. As a part of this, we present in this paper a novel methodology which unifies the problems of Layout Automation and Algorithm Mapping.

Resin infiltration transfer technique

DOEpatents

Miller, David V [Pittsburgh, PA; Baranwal, Rita [Glenshaw, PA

2009-12-08

A process has been developed for fabricating composite structures using either reaction forming or polymer infiltration and pyrolysis techniques to densify the composite matrix. The matrix and reinforcement materials of choice can include, but are not limited to, silicon carbide (SiC) and zirconium carbide (ZrC). The novel process can be used to fabricate complex, net-shape or near-net shape, high-quality ceramic composites with a crack-free matrix.

Effects of zeolites on cultures of marine micro-algae: A brief review.

PubMed

Fachini, Adriano; Vasconcelos, Maria Teresa S D

2006-10-01

The cation-exchange capacity of zeolites is well known and has been increasingly explored in different fields with both economic and environmental successes. In aquatic medium with low salinity, zeolites have found multiple applications. However, a review of the literature on the applications of zeolites in salt waters found relatively few articles, including some recently published papers. The purpose of this review is to present the state-of-the-art on applications of using zeolites for amending the trace elemental contents of salt water as well as the implications of this property for promoting marine micro-algal growth. This paper deals with the following features: Sorption capacity of zeolites including 1. application of zeolites in saltwater, 2. the role of silicon and zeolites on cultures of micro-algae, and 3. the role of organically chelated trace metals. The following competing factors have been identified as effects of zeolites on algal growth in salt water: (i) ammonia decrease: growth inhibition reduced; (ii) macro-nutrients increase, mainly silicon: stimulation of silicon-dependent algae; (iii) trace metals increase (desorption from zeolites) or decrease (adsorption): inhibition or stimulation, depending on the nature of the element and its concentration; and, (iv) changes in the chelating organics exudation: inhibition or stimulation of growth, depending on the (a) nature of the complexed element; (b) bioavailability of the complex; and (c) concentration of the elements simultaneously present in inorganic forms. Zeolites have been capable of stimulating the growth of the silicon-demanding marine micro-algae, like diatoms, mainly because they can act as a silicon buffer in seawater. Zeolites can also influence the yield of non-silicon-demanding algae, because the changes they can cause (liberation and adsorption of trace elements) in the composition of the medium. Zeolites have been capable of stimulating the growth of the marine micro-algae. However, the extent of ion exchange between zeolite and seawater, which conditions the effects, will depend on several factors: (1) initial metal concentration in seawater; (2) levels of trace metals in the zeolites (contaminants); (3) characteristics of the zeolites in terms of both ion-exchange capacity and specific affinities for the different cations; (4) quantity of zeolite per litre of solution; (5) pH and (6) response of the organism in terms of liberation of organic ligands. Therefore, a previous investigation in each particular case is recommended, in order to select the zeolitic characteristics and concentrations that will maximize the algal yield. Stimulation of phytoplankton growth can be economically relevant since phytoplankton constitutes the basis of the marine food webs and is required in fish farming nurseries in the marine aquaculture industry. Zeolites are cheap, only small amounts (few milligrams per liter of culture) are required and the addition of some micro-nutrients may be omitted. Therefore, the inclusion of zeolites in algal cultures in aquaculture may have economic advantages.

Micromachined Silicon Stimulating Probes with CMOS Circuitry for Use in the Central Nervous System

NASA Astrophysics Data System (ADS)

Tanghe, Steven John

1992-01-01

Electrical stimulation in the central nervous system is a valuable technique for studying neural systems and is a key element in the development of prostheses for deafness and other disorders. This thesis presents a family of multielectrode probe structures, fulfilling the need for chronic multipoint stimulation tools essential for interfacing to the highly complex neural networks in the brain. These probes are batch-fabricated on silicon wafers, employing photoengraving techniques to precisely control the electrode site and array geometries and to allow the integration of on-chip CMOS circuitry for signal multiplexing and stimulus current generation. Silicon micromachining is used to define the probe shapes, which have typical shank dimensions of 3 mm in length by 100 mu m in width by 15 μm in thickness. Each shank supports up to eight planar iridium oxide electrode sites capable of delivering charge densities in excess of 3 mC/cm^2 during current pulse stimulation. Three active probe circuits have been designed with varied complexity and capability. All three can deliver biphasic stimulus currents through 16 sites using only 5 external leads, and they are all compatible with the same external control system. The most complex design interprets site addresses and stimulus current amplitudes from 16-bit words shifted into the probe at 4 MHz. Sixteen on-chip, biphasic, 8-bit digital-to-analog converters deliver analog stimulus currents in the range of +/- 254 muA to any combination of electrode sites. These DACs exhibit full-scale internal linearity to better than +/-1/2 LSB and can be calibrated by varying the positive power supply voltage. The entire probe circuit dissipates only 80 muW from +/-5 V supplies when not delivering stimulus currents, it includes several safety features, and is testable from the input pads. Test results from the fabricated circuits indicate that they all function properly at clocking frequencies as high as 10 MHz, meeting or exceeding all design specifications. Probe structures without circuitry have been used for stimulation experiments in guinea pigs yielding excellent results.

Red/near-infrared luminescence tuning of group-14 element complexes of dipyrrins based on a central atom.

PubMed

Yamamura, Masaki; Albrecht, Marcel; Albrecht, Markus; Nishimura, Yoshinobu; Arai, Tatsuo; Nabeshima, Tatsuya

2014-02-03

A dipyrrin complex has been one of the most utilized fluorescent dyes, and a variety of dipyrrin complexes show intriguing functions based on the various coordination structures of the central element. We now report the synthesis, structure, and photophysical properties of germanium and stannane complexes of the N2O2-type tetradentate dipyrrin, L·Ge and L·Sn, which are heavier analogues of the previously reported dipyrrin silicon complex, L·Si. The central group-14 atoms of the monomeric complexes have geometries close to trigonal bipyramidal (TBP), in which the contribution of the square-pyramidal (SP) character becomes higher as the central atom is heavier. Interestingly, L·Sn formed a dimeric structure in the crystal. All complexes L·Si, L·Ge, and L·Sn showed a fluorescence in the red/NIR region. Fluorescence quantum yields of L·Ge and L·Sn are higher than that of L·Si. These results indicated that the central atom on the dipyrrin complexes contributes not only to the geometry difference but also to tuning the fluorescence properties.

Reducing the Cost of Solar Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scanlon, B.

2012-04-01

Solar-powered electricity prices could soon approach those of power from coal or natural gas thanks to collaborative research with solar startup Ampulse Corporation at the National Renewable Energy Laboratory. Silicon wafers account for almost half the cost of today's solar photovoltaic panels, so reducing or eliminating wafer costs is essential to bringing prices down. Current crystalline silicon technology converts energy in a highly efficient manner; however, that technology is manufactured with processes that could stand some improvement. The industry needs a method that is less complex, creates less waste and uses less energy. First, half the refined silicon is lostmore » as dust in the wafer-sawing process, driving module costs higher. Wafers are sawn off of large cylindrical ingots, or boules, of silicon. A typical 2-meter boule loses as many as 6,000 potential wafers during sawing. Second, the wafers produced are much thicker than necessary. To efficiently convert sunlight into electricity, the wafers need be only one-tenth the typical thickness. NREL, the Oak Ridge National Laboratory and Ampulse have partnered on an approach to eliminate this waste and dramatically lower the cost of the finished solar panels. By using a chemical vapor deposition process to grow the silicon on inexpensive foil, Ampulse is able to make the solar cells just thick enough to convert most of the solar energy into electricity. No more sawdust - and no more wasting refined silicon materials. NREL developed the technology to grow high-quality silicon and ORNL developed the metal foil that has the correct crystal structure to support that growth. Ampulse is installing a pilot manufacturing line in NREL's Process Development Integration Laboratory, where solar companies can work closely with lab scientists on integrated equipment to answer pressing questions related to their technology development, as well as rapidly overcoming R and D challenges and risk. NREL's program is focused on transformative innovation in the domestic PV industry. With knowledge and expertise acquired from the PDIL pilot production line tools, Ampulse plans to design a full-scale production line to accommodate long rolls of metal foil. The Ampulse process 'goes straight from pure silicon-containing gas to high-quality crystal silicon film,' said Brent Nelson, the operational manager for the Process Development Integration Laboratory. 'The advantage is you can make the wafer just as thin as you need it - 10 microns or less.' Most of today's solar cells are made out of wafer crystalline silicon, though thin-film cells made of more exotic elements such as copper, indium, gallium, arsenic, cadmium, tellurium and others are making a strong push into the market. The advantage of silicon is its abundance, because it is derived from sand. Silicon's disadvantage is that purifying it into wafers suitable for solar cells can be expensive and energy intensive. Manufacturers add carbon and heat to sand to produce metallurgical-grade silicon, which is useful in other industries, but not yet suitable for making solar cells. So this metallurgical-grade silicon is then converted to pure trichlorosilane (SiCl3) or silane (SiH4) gas. Typically, the purified gas is then converted to create a silicon feedstock at 1,000 degrees Celsius. This feedstock is melted at 1,414 C and recrystallized into crystal ingots that are finally sawed into wafers. The Ampulse method differs in that it eliminates the last two steps in the traditional process and works directly with the silane gas growing only the needed silicon right onto a foil substrate. A team of NREL scientists had developed a way to use a process called hot-wire chemical vapor deposition to thicken silicon wafers with near perfect crystal structure. Using a hot tungsten filament much like the one found in an incandescent light bulb, the silane gas molecules are broken apart and deposited onto the wafer using the chemical vapor deposition technique at about 700 C - a much lower temperature than needed to make the wafer. The hot filament decomposes the gas, allowing silicon layers to deposit directly onto the substrate. Armed with this new technique, Branz and Teplin searched for ways to grow the silicon on cheaper materials and still use it for solar cells. They found the ideal synergy when visiting venture capitalists from Battelle Ventures asked them whether they could do anything useful with a breakthrough from Oak Ridge's superconducting wire development group. The new development, called the rolling assisted biaxially textured substrate (RABiTS), was just the opportunity the two scientists had been seeking. If metal foil is to work as a substrate, it must be able to act as a seed crystal so the silicon can grow on it with the correct structure. The RABiTS process forms crystals in the foil that are correctly oriented to receive the silicon atoms and lock them into just the right positions.« less

Carbon nanotube-copper exhibiting metal-like thermal conductivity and silicon-like thermal expansion for efficient cooling of electronics.

PubMed

Subramaniam, Chandramouli; Yasuda, Yuzuri; Takeya, Satoshi; Ata, Seisuke; Nishizawa, Ayumi; Futaba, Don; Yamada, Takeo; Hata, Kenji

2014-03-07

Increasing functional complexity and dimensional compactness of electronic devices have led to progressively higher power dissipation, mainly in the form of heat. Overheating of semiconductor-based electronics has been the primary reason for their failure. Such failures originate at the interface of the heat sink (commonly Cu and Al) and the substrate (silicon) due to the large mismatch in thermal expansion coefficients (∼300%) of metals and silicon. Therefore, the effective cooling of such electronics demands a material with both high thermal conductivity and a similar coefficient of thermal expansion (CTE) to silicon. Addressing this demand, we have developed a carbon nanotube-copper (CNT-Cu) composite with high metallic thermal conductivity (395 W m(-1) K(-1)) and a low, silicon-like CTE (5.0 ppm K(-1)). The thermal conductivity was identical to that of Cu (400 W m(-1) K(-1)) and higher than those of most metals (Ti, Al, Au). Importantly, the CTE mismatch between CNT-Cu and silicon was only ∼10%, meaning an excellent compatibility. The seamless integration of CNTs and Cu was achieved through a unique two-stage electrodeposition approach to create an extensive and continuous interface between the Cu and CNTs. This allowed for thermal contributions from both Cu and CNTs, resulting in high thermal conductivity. Simultaneously, the high volume fraction of CNTs balanced the thermal expansion of Cu, accounting for the low CTE of the CNT-Cu composite. The experimental observations were in good quantitative concurrence with the theoretically described 'matrix-bubble' model. Further, we demonstrated identical in-situ thermal strain behaviour of the CNT-Cu composite to Si-based dielectrics, thereby generating the least interfacial thermal strain. This unique combination of properties places CNT-Cu as an isolated spot in an Ashby map of thermal conductivity and CTE. Finally, the CNT-Cu composite exhibited the greatest stability to temperature as indicated by its low thermal distortion parameter (TDP). Thus, this material presents a viable and efficient alternative to existing materials for thermal management in electronics.

Biodegradable Porous Silicon Nanomaterials for Imaging and Treatment of Cancer

NASA Astrophysics Data System (ADS)

Gu, Luo

Cancer is the second leading cause of death, claiming ˜0.56 million lives in the U.S. every year following heart diseases (˜0.62 million). From 1991 to 2007, mortality associated with heart diseases decreased 39%; by contrast, the death rate of cancer only decreased by 17% in spite of intensive research and improved therapeutics. The stagnation of conventional medicine and the complexity of cancer demand new therapeutic strategies. As an emerging approach, the use of nanomaterials as cancer diagnostic and therapeutic agents has shown promising results due to their unique physical and chemical properties. To date, more than two dozen nanoparticle-based products have been approved for clinical use and they show advantages over conventional therapeutics. However, translation of many other nanomaterials has been impeded due to concerns over toxicity and biodegradability. This dissertation presents the development of biodegradable luminescent porous silicon nanomaterials and their potential applications for imaging and treatment of cancer. After a brief introduction to nanomedicine and the biomedical applications of porous silicon, Chapter 2 presents a method of making silicon nanoparticles with porous structure and intrinsic luminescence (LPSiNPs). The low toxicity and biodegradability of LPSiNPs are demonstrated in vitro with human cancer cells and in vivo with mouse model. The in vivo clearance of intravenously injected LPSiNPs is studied by tracking the emission of the nanoparticles with fluorescence imaging. Chapter 3 presents a diagnostic application of LPSiNPs. Time-gated fluorescence imaging of tumors using LPSiNPs with long emission lifetime is developed. This technique can effectively eliminate interference from short-lived tissue autofluorescence and improve the detection sensitivity. Chapter 4--6 demonstrate the therapeutic applications of porous silicon nanomaterials. In Chapter 4, magnetically-guided delivery of anticancer drug to cancer cells in vitro is achieved using magnetic, luminescent porous Si microparticles. Chapter 5 demonstrates that porous silicon nanoparticles can be used as photosensitizer and generate cytotoxic singlet oxygen when irradiated by light. The phototoxicity of the nanoparticles against cancer cells is also studied. Finally, the use of LPSiNPs for immune activation is investigated in Chapter 6.

Ultrafast carrier thermalization and trapping in silicon-germanium alloy probed by extreme ultraviolet transient absorption spectroscopy

PubMed Central

Zürch, Michael; Chang, Hung-Tzu; Kraus, Peter M.; Cushing, Scott K.; Borja, Lauren J.; Gandman, Andrey; Kaplan, Christopher J.; Oh, Myoung Hwan; Prell, James S.; Prendergast, David; Pemmaraju, Chaitanya D.; Neumark, Daniel M.; Leone, Stephen R.

2017-01-01

Semiconductor alloys containing silicon and germanium are of growing importance for compact and highly efficient photonic devices due to their favorable properties for direct integration into silicon platforms and wide tunability of optical parameters. Here, we report the simultaneous direct and energy-resolved probing of ultrafast electron and hole dynamics in a silicon-germanium alloy with the stoichiometry Si0.25Ge0.75 by extreme ultraviolet transient absorption spectroscopy. Probing the photoinduced dynamics of charge carriers at the germanium M4,5-edge (∼30 eV) allows the germanium atoms to be used as reporter atoms for carrier dynamics in the alloy. The photoexcitation of electrons across the direct and indirect band gap into conduction band (CB) valleys and their subsequent hot carrier relaxation are observed and compared to pure germanium, where the Ge direct (ΔEgap,Ge,direct=0.8 eV) and Si0.25Ge0.75 indirect gaps (ΔEgap,Si0.25Ge0.75,indirect=0.95 eV) are comparable in energy. In the alloy, comparable carrier lifetimes are observed for the X, L, and Γ valleys in the conduction band. A midgap feature associated with electrons accumulating in trap states near the CB edge following intraband thermalization is observed in the Si0.25Ge0.75 alloy. The successful implementation of the reporter atom concept for capturing the dynamics of the electronic bands by site-specific probing in solids opens a route to study carrier dynamics in more complex materials with femtosecond and sub-femtosecond temporal resolution. PMID:28653020

Nanoporous Silicon Combustion: Observation of Shock Wave and Flame Synthesis of Nanoparticle Silica.

PubMed

Becker, Collin R; Gillen, Greg J; Staymates, Matthew E; Stoldt, Conrad R

2015-11-18

The persistent hydrogen termination present in nanoporous silicon (nPS) is unique compared to other forms of nanoscale silicon (Si) which typically readily form a silicon dioxide passivation layer. The hydrogen terminated surface combined with the extremely high surface area of nPS yields a material capable of powerful exothermic reactions when combined with strong oxidizers. Here, a galvanic etching mechanism is used to produce nPS both in bulk Si wafers as well as in patterned regions of Si wafers with microfabricated ignition wires. An explosive composite is generated by filling the pores with sodium perchlorate (NaClO4). Using high-speed video including Schlieren photography, a shock wave is observed to propagate through air at 1127 ± 116 m/s. Additionally, a fireball is observed above the region of nPS combustion which persists for nearly 3× as long when reacted in air compared to N2, indicating that highly reactive species are generated that can further combust with excess oxygen. Finally, reaction products from either nPS-NaClO4 composites or nPS alone combusted with only high pressure O2 (400 psig) gas as an oxidizer are captured in a calorimeter bomb. The products in both cases are similar and verified by transmission electron microscopy (TEM) to include nano- to micrometer scale SiOx particles. This work highlights the complex oxidation mechanism of nPS composites and demonstrates the ability to use a solid state reaction to create a secondary gas phase combustion.

International space station wire program

NASA Technical Reports Server (NTRS)

May, Todd

1995-01-01

Hardware provider wire systems and current wire insulation issues for the International Space Station (ISS) program are discussed in this viewgraph presentation. Wire insulation issues include silicone wire contamination, Tefzel cold temperature flexibility, and Russian polyimide wire insulation. ISS is a complex program with hardware developed and managed by many countries and hundreds of contractors. Most of the obvious wire insulation issues are known by contractors and have been precluded by proper selection.

All-Printed Flexible and Stretchable Electronics.

PubMed

Mohammed, Mohammed G; Kramer, Rebecca

2017-05-01

A fully automated additive manufacturing process that produces all-printed flexible and stretchable electronics is demonstrated. The printing process combines soft silicone elastomer printing and liquid metal processing on a single high-precision 3D stage. The platform is capable of fabricating extremely complex conductive circuits, strain and pressure sensors, stretchable wires, and wearable circuits with high yield and repeatability. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

New ways to develop biosensors towards addressing practical problems

NASA Astrophysics Data System (ADS)

Starodub, N. F.

2013-11-01

The main modern approaches which were realized at the development of new generation of biosensors intended for application in field of diagnostics, food quality control and environmental monitoring are presented. The main attention was paid to creation of the multi-parametrical and multi-functional enzymatic and immune biosensors which were realized for the complex diagnostics of diabetes, autoimmune state and for the control of process of sugar production. The label-free bioaffine devices based on the nano-porouse silicon (NPS) with the registration of specific formed signal by chemiluminescence (ChL) and photoresistivity and intended for the determination mycotoxins and diagnostics of retroviral bovine leukemia (RBL) are analyzed too. Improving of ion sensitive field effect transistors (ISFETs) through changing silicon nitride on the cerium oxide is discussed as perspective approach in case of micotoxins and Salmonella control. In the conclusion the possibility to replace biological sensitive elements by artificial ones is considered.

Acoustically driven degradation in single crystalline silicon solar cell

NASA Astrophysics Data System (ADS)

Olikh, O. Ya.

2018-05-01

The influence of ultrasound on current-voltage characteristics of crystalline silicon solar sell was investigated experimentally. The transverse and longitudinal acoustic waves were used over a temperature range of 290-340 K. It was found that the ultrasound loading leads to the reversible decrease in the photogenerated current, open-circuit voltage, fill factor, carrier lifetime, and shunt resistance as well as the increase in the ideality factor. The experimental results were described by using the models of coupled defect level recombination, Shockley-Read-Hall recombination, and dislocation-induced impedance. The contribution of the boron-oxygen related defects, iron-boron pairs, and oxide precipitates to both the carrier recombination and acousto-defect interaction was discussed. The experimentally observed phenomena are associated with the increase in the distance between coupled defects as well as the extension of the carrier capture coefficient of complex point defects and dislocations.

Innovative and water based stripping approach for thick and bulk photoresists

NASA Astrophysics Data System (ADS)

Rudolph, Matthias; Schumann, Dirk; Thrun, Xaver; Esche, Silvio; Hohle, Christoph

2014-10-01

The usage of phase fluid based stripping agents to remove photoresists from silicon substrates was studied. Photoresists are required for many silicon based technologies such as MEMS patterning, 3D-Integration or frontend and backend of line semiconductor applications [1]. Although the use of resists is very common, their successful integration often depends on the ability to remove the resist after certain processing steps. On the one hand the resist is changing during subsequent process steps that can cause a thermally activated cross-linking which increases the stripping complexity. Resist removal is also challenging after the formation of a hard polymer surface layer during plasma or implant processes which is called skin or crust [2]. On the other hand the choice of stripping chemistry is often limited due to the presence of functional materials such as metals which can be damaged by aggressive stripping chemistries [3].

Joining and Integration of Silicon Carbide for Turbine Engine Applications

NASA Technical Reports Server (NTRS)

Halbig, Michael C.; Singh, Mrityunjay; Coddington, Bryan; Asthana, Rajiv

2010-01-01

The critical need for ceramic joining and integration technologies is becoming better appreciated as the maturity level increases for turbine engine components fabricated from ceramic and ceramic matrix composite materials. Ceramic components offer higher operating temperatures and reduced cooling requirements. This translates into higher efficiencies and lower emissions. For fabricating complex shapes, diffusion bonding of silicon carbide (SiC) to SiC is being developed. For the integration of ceramic parts to the surrounding metallic engine system, brazing of SiC to metals is being developed. Overcoming the chemical, thermal, and mechanical incompatibilities between dissimilar materials is very challenging. This presentation will discuss the types of ceramic components being developed by researchers and industry and the benefits of using ceramic components. Also, the development of strong, crack-free, stable bonds will be discussed. The challenges and progress in developing joining and integration approaches for a specific application, i.e. a SiC injector, will be presented.

Graphene radio frequency receiver integrated circuit.

PubMed

Han, Shu-Jen; Garcia, Alberto Valdes; Oida, Satoshi; Jenkins, Keith A; Haensch, Wilfried

2014-01-01

Graphene has attracted much interest as a future channel material in radio frequency electronics because of its superior electrical properties. Fabrication of a graphene integrated circuit without significantly degrading transistor performance has proven to be challenging, posing one of the major bottlenecks to compete with existing technologies. Here we present a fabrication method fully preserving graphene transistor quality, demonstrated with the implementation of a high-performance three-stage graphene integrated circuit. The circuit operates as a radio frequency receiver performing signal amplification, filtering and downconversion mixing. All circuit components are integrated into 0.6 mm(2) area and fabricated on 200 mm silicon wafers, showing the unprecedented graphene circuit complexity and silicon complementary metal-oxide-semiconductor process compatibility. The demonstrated circuit performance allow us to use graphene integrated circuit to perform practical wireless communication functions, receiving and restoring digital text transmitted on a 4.3-GHz carrier signal.

Radiation damage annealing mechanisms and possible low temperature annealing in silicon solar cells

NASA Technical Reports Server (NTRS)

Weinberg, I.; Swartz, C. K.

1980-01-01

The defect responsible for reverse annealing in 2 ohm/cm n(+)/p silicon solar cells was identified. This defect, with energy level at e sub v + 0.30 eV was tentatively identified as a boron oxygen-vacancy complex. Results indicate that its removal could result in significant annealing for 2 ohm/cm and lower resistivity cells at temperatures as low as 200 C. These results were obtained by use of an expression derived from the Shockley-Read-Hall recombination theory which relates measured diffusion length ratios to relative defect concentrations and electron capture cross sections. The relative defect concentrations and one of the required capture cross sections are obtained from Deep Level Transient Spectroscopy. Four additional capture cross sections are obtained using diffusion length data and data from temperature dependent lifetime studied. These calculated results are in reasonable agreement with experimental data.

The euglobulin clot lysis time to assess the impact of nanoparticles on fibrinolysis

NASA Astrophysics Data System (ADS)

Minet, Valentine; Alpan, Lutfiye; Mullier, François; Toussaint, Olivier; Lucas, Stéphane; Dogné, Jean-Michel; Laloy, Julie

2015-07-01

Nanoparticles (NPs) are developed for many applications in various fields, including nanomedicine. The NPs used in nanomedicine may disturb homeostasis in blood. Secondary hemostasis (blood coagulation) and fibrinolysis are complex physiological processes regulated by activators and inhibitors. An imbalance of this system can either lead to the development of hemorrhages or thrombosis. No data are currently available on the impact of NPs on fibrinolysis. The objectives of this study are (1) to select a screening test to study ex vivo the impact of NPs on fibrinolysis and (2) to test NPs with different physicochemical properties. Euglobulin clot lysis time test was selected to screen the impact of some NPs on fibrinolysis using normal pooled plasma. A dose-dependent decrease in the lysis time was observed with silicon dioxide and silver NPs without disturbing the fibrin network. Carbon black, silicon carbide, and copper oxide did not affect the lysis time at the tested concentrations.

Hall effect analysis in irradiated silicon samples with different resistivities

NASA Astrophysics Data System (ADS)

Borchi, E.; Bruzzi, M.; Dezillie, B.; Lazanu, S.; Li, Z.; Pirollo, S.

1999-08-01

The changes induced by neutron irradiation in n- and p-type silicon samples with starting resistivities from 10 /spl Omega/-cm up to 30 k/spl Omega/-cm, grown using different techniques, as float-zone (FZ), Czochralski (CZ) and epitaxial, have been analyzed by Van der Pauw and Hall effect measurements. Increasing the fluence, each set of samples evolves toward a quasi-intrinsic p-type material. This behavior has been explained in the frame of a two-level model, that considers the introduction during irradiation of mainly two defects. A deep acceptor and a deep donor, probably related to the divacancy and to the C/sub i/O/sub i/ complex, are placed in the upper and lower half of the forbidden gap, respectively. This simple model explains quantitatively the data on resistivity and Hall coefficient of each set of samples up to the fluence of /spl ap/10/sup 14/ n/cm/sup 2/.

Lightwave Circuits in Lithium Niobate through Hybrid Waveguides with Silicon Photonics

DOE PAGES

Weigel, Peter O.; Savanier, Marc; DeRose, Christopher T.; ...

2016-03-01

Here, we demonstrate a photonic waveguide technology based on a two-material core, in which light is controllably and repeatedly transferred back and forth between sub-micron thickness crystalline layers of Si and LN bonded to one another, where the former is patterned and the latter is not. In this way, the foundry-based wafer-scale fabrication technology for silicon photonics can be leveraged to form lithium-niobate based integrated optical devices. Using two different guided modes and an adiabatic mode transition between them, we demonstrate a set of building blocks such as waveguides, bends, and couplers which can be used to route light underneathmore » an unpatterned slab of LN, as well as outside the LN-bonded region, thus enabling complex and compact lightwave circuits in LN alongside Si photonics with fabrication ease and low cost.« less

Solution-Based Fabrication of Polycrystalline Si Thin-Film Transistors from Recycled Polysilanes.

PubMed

Sberna, Paolo M; Trifunovic, Miki; Ishihara, Ryoichi

2017-07-03

Currently, research has been focusing on printing and laser crystallization of cyclosilanes, bringing to life polycrystalline silicon (poly-Si) thin-film transistors (TFTs) with outstanding properties. However, the synthesis of these Si-based inks is generally complex and expensive. Here, we prove that a polysilane ink, obtained as a byproduct of silicon gases and derivatives, can be used successfully for the synthesis of poly-Si by laser annealing, at room temperature, and for n- and p-channel TFTs. The devices, fabricated according to CMOS compatible processes at 350 °C, showed field effect mobilities up to 8 and 2 cm 2 /(V s) for n- and p-type TFTs, respectively. The presented method combines a low-cost coating technique with the usage of recycled material, opening a route to a convenient and sustainable production of large-area, flexible, and even disposable/single-use electronics.

Nanophotonic integrated circuits from nanoresonators grown on silicon.

PubMed

Chen, Roger; Ng, Kar Wei; Ko, Wai Son; Parekh, Devang; Lu, Fanglu; Tran, Thai-Truong D; Li, Kun; Chang-Hasnain, Connie

2014-07-07

Harnessing light with photonic circuits promises to catalyse powerful new technologies much like electronic circuits have in the past. Analogous to Moore's law, complexity and functionality of photonic integrated circuits depend on device size and performance scale. Semiconductor nanostructures offer an attractive approach to miniaturize photonics. However, shrinking photonics has come at great cost to performance, and assembling such devices into functional photonic circuits has remained an unfulfilled feat. Here we demonstrate an on-chip optical link constructed from InGaAs nanoresonators grown directly on a silicon substrate. Using nanoresonators, we show a complete toolkit of circuit elements including light emitters, photodetectors and a photovoltaic power supply. Devices operate with gigahertz bandwidths while consuming subpicojoule energy per bit, vastly eclipsing performance of prior nanostructure-based optoelectronics. Additionally, electrically driven stimulated emission from an as-grown nanostructure is presented for the first time. These results reveal a roadmap towards future ultradense nanophotonic integrated circuits.

The Effect of Fiber Architecture on Matrix Cracking in Sic/sic Cmc's

NASA Technical Reports Server (NTRS)

Morscher, Gregory N.

2005-01-01

Applications incorporating silicon carbide fiber reinforced silicon carbide matrix composites (CMC's) will require a wide range of fiber architectures in order to fabricate complex shape. The stress-strain response of a given SiC/SiC system for different architectures and orientations will be required in order to design and effectively life-model future components. The mechanism for non-linear stress-strain behavior in CMC's is the formation and propagation of bridged-matrix cracks throughout the composite. A considerable amount of understanding has been achieved for the stress-dependent matrix cracking behavior of SiC fiber reinforced SiC matrix systems containing melt-infiltrated Si. This presentation will outline the effect of 2D and 3D architectures and orientation on stress-dependent matrix-cracking and how this information can be used to model material behavior and serve as the starting point foe mechanistic-based life-models.

Eddy current imaging for electrical characterization of silicon solar cells and TCO layers

NASA Astrophysics Data System (ADS)

Hwang, Byungguk; Hillmann, Susanne; Schulze, Martin; Klein, Marcus; Heuer, Henning

2015-03-01

Eddy Current Testing has been mainly used to determine defects of conductive materials and wall thicknesses in heavy industries such as construction or aerospace. Recently, high frequency Eddy Current imaging technology was developed. This enables the acquirement of information of different depth level in conductive thin-film structures by realizing proper standard penetration depth. In this paper, we summarize the state of the art applications focusing on PV industry and extend the analysis implementing achievements by applying spatially resolved Eddy Current Testing. The specific state of frequency and complex phase angle rotation demonstrates diverse defects from front to back side of silicon solar cells and characterizes homogeneity of sheet resistance in Transparent Conductive Oxide (TCO) layers. In order to verify technical feasibility, measurement results from the Multi Parameter Eddy Current Scanner, MPECS are compared to the results from Electroluminescence.

Joining of Silicon Carbide Through the Diffusion Bonding Approach

NASA Technical Reports Server (NTRS)

Halbig, Michael .; Singh, Mrityunjay

2009-01-01

In order for ceramics to be fully utilized as components for high-temperature and structural applications, joining and integration methods are needed. Such methods will allow for the fabrication the complex shapes and also allow for insertion of the ceramic component into a system that may have different adjacent materials. Monolithic silicon carbide (SiC) is a ceramic material of focus due to its high temperature strength and stability. Titanium foils were used as an interlayer to form diffusion bonds between chemical vapor deposited (CVD) SiC ceramics with the aid of hot pressing. The influence of such variables as interlayer thickness and processing time were investigated to see which conditions contributed to bonds that were well adhered and crack free. Optical microscopy, scanning electron microscopy, and electron microprobe analysis were used to characterize the bonds and to identify the reaction formed phases.

Single-chip source-free terahertz spectroscope across 0.04-0.99 THz: combining sub-wavelength near-field sensing and regression analysis.

PubMed

Wu, Xue; Sengupta, Kaushik

2018-03-19

This paper demonstrates a methodology to miniaturize THz spectroscopes into a single silicon chip by eliminating traditional solid-state architectural components such as complex tunable THz and optical sources, nonlinear mixing and amplifiers. The proposed method achieves this by extracting incident THz spectral signatures from the surface of an on-chip antenna itself. The information is sensed through the spectrally-sensitive 2D distribution of the impressed current surface under the THz incident field. By converting the antenna from a single-port to a massively multi-port architecture with integrated electronics and deep subwavelength sensing, THz spectral estimation is converted into a linear estimation problem. We employ rigorous regression techniques and analysis to demonstrate a single silicon chip system operating at room temperature across 0.04-0.99 THz with 10 MHz accuracy in spectrum estimation of THz tones across the entire spectrum.

A silicone rubber mould of the heart.

PubMed

Torrent-Guasp, F F; Whimster, W F; Redmann, K

1997-04-01

The macroscopical structure of the ventricular myocardium has been an unsolved problem since the XVIth century, when Anatomy started as an authentic science. Since then the spatial organization of the myocardial fibres has represented, as Pettigrew says, "an arrangement so unusual and perplexing, that it has long been considered as forming a kind of Gordian knot in Anatomy. Of the complexity of the arrangement I need not speak further than to say that Vesalius, Albinus, Haller and De Blainville, all confessed their-inability to unravel it". What is shown in the present paper is the result of an anatomical work, developed over 43 years, by means of which it has been shown that the ventricular myocardial mass consists of a band, curled in a helical way, which extends from the pulmonary artery to the aorta. This is illustrated by a silicone rubber model cast from an actual unrolled myocardial band.

A novel multi-level IC-compatible surface microfabrication technology for MEMS with independently controlled lateral and vertical submicron transduction gaps

NASA Astrophysics Data System (ADS)

Cicek, Paul-Vahe; Elsayed, Mohannad; Nabki, Frederic; El-Gamal, Mourad

2017-11-01

An above-IC compatible multi-level MEMS surface microfabrication technology based on a silicon carbide structural layer is presented. The fabrication process flow provides optimal electrostatic transduction by allowing the creation of independently controlled submicron vertical and lateral gaps without the need for high resolution lithography. Adopting silicon carbide as the structural material, the technology ensures material, chemical and thermal compatibility with modern semiconductor nodes, reporting the lowest peak processing temperature (i.e. 200 °C) of all comparable works. This makes this process ideally suited for integrating capacitive-based MEMS directly above standard CMOS substrates. Process flow design and optimization are presented in the context of bulk-mode disk resonators, devices that are shown to exhibit improved performance with respect to previous generation flexural beam resonators, and that represent relatively complex MEMS structures. The impact of impending improvements to the fabrication technology is discussed.

Modification of surface properties of solids by femtosecond LIPSS writing: comparative studies on silicon and stainless steel

NASA Astrophysics Data System (ADS)

Varlamova, Olga; Hoefner, Kevin; Ratzke, Markus; Reif, Juergen; Sarker, Debasish

2017-12-01

We investigate the implication of modified surface morphology on wettability of stainless steel (AISI 304) and silicon (100) targets covered by laser-induced periodic surface structures (LIPSS) on extended areas (10 × 10 mm2). Using multiple pulses from a Ti: Sapphire laser (790 nm/100 fs/1 kHz) at a fluence in the range of 0.35-2.1 J/cm2 on a spot of 1.13 × 10- 4 cm2, we scanned the target under the spot to cover a large area. A systematical variation of the irradiation dose by changing the scanning speed and thus dwelling time per spot results in the formation of surface patterns ranging from very regular linear structures with a lateral period of about 500-600 nm to complex patterns of 3D microstructures with several-µm feature size, hierarchically covered by nano-ripples.

The CiCs(SiI)n Defect in Silicon from a Density Functional Theory Perspective.

PubMed

Christopoulos, Stavros-Richard G; Sgourou, Efstratia N; Vovk, Ruslan V; Chroneos, Alexander; Londos, Charalampos A

2018-04-16

Carbon constitutes a significant defect in silicon (Si) as it can interact with intrinsic point defects and affect the operation of devices. In heavily irradiated Si containing carbon the initially produced carbon interstitial-carbon substitutional (C i C s ) defect can associate with self-interstitials (Si I 's) to form, in the course of irradiation, the C i C s (Si I ) defect and further form larger complexes namely, C i C s (Si I ) n defects, by the sequential trapping of self-interstitials defects. In the present study, we use density functional theory to clarify the structure and energetics of the C i C s (Si I ) n defects. We report that the lowest energy C i C s (Si I ) and C i C s (Si I )₂ defects are strongly bound with -2.77 and -5.30 eV, respectively.

Experimental realization of Bloch oscillations in a parity-time synthetic silicon photonic lattice

PubMed Central

Xu, Ye-Long; Fegadolli, William S.; Gan, Lin; Lu, Ming-Hui; Liu, Xiao-Ping; Li, Zhi-Yuan; Scherer, Axel; Chen, Yan-Feng

2016-01-01

As an important electron transportation phenomenon, Bloch oscillations have been extensively studied in condensed matter. Due to the similarity in wave properties between electrons and other quantum particles, Bloch oscillations have been observed in atom lattices, photonic lattices, and so on. One of the many distinct advantages for choosing these systems over the regular electronic systems is the versatility in engineering artificial potentials. Here by utilizing dissipative elements in a CMOS-compatible photonic platform to create a periodic complex potential and by exploiting the emerging concept of parity-time synthetic photonics, we experimentally realize spatial Bloch oscillations in a non-Hermitian photonic system on a chip level. Our demonstration may have significant impact in the field of quantum simulation by following the recent trend of moving complicated table-top quantum optics experiments onto the fully integrated CMOS-compatible silicon platform. PMID:27095533

Graphene radio frequency receiver integrated circuit

NASA Astrophysics Data System (ADS)

Han, Shu-Jen; Garcia, Alberto Valdes; Oida, Satoshi; Jenkins, Keith A.; Haensch, Wilfried

2014-01-01

Graphene has attracted much interest as a future channel material in radio frequency electronics because of its superior electrical properties. Fabrication of a graphene integrated circuit without significantly degrading transistor performance has proven to be challenging, posing one of the major bottlenecks to compete with existing technologies. Here we present a fabrication method fully preserving graphene transistor quality, demonstrated with the implementation of a high-performance three-stage graphene integrated circuit. The circuit operates as a radio frequency receiver performing signal amplification, filtering and downconversion mixing. All circuit components are integrated into 0.6 mm2 area and fabricated on 200 mm silicon wafers, showing the unprecedented graphene circuit complexity and silicon complementary metal-oxide-semiconductor process compatibility. The demonstrated circuit performance allow us to use graphene integrated circuit to perform practical wireless communication functions, receiving and restoring digital text transmitted on a 4.3-GHz carrier signal.

Silicon Promotes Exodermal Casparian Band Formation in Si-Accumulating and Si-Excluding Species by Forming Phenol Complexes

PubMed Central

Hinrichs, Martin; Specht, André; Waßmann, Friedrich; Schreiber, Lukas; Schenk, Manfred K.

2015-01-01

We studied the effect of Silicon (Si) on Casparian band (CB) development, chemical composition of the exodermal CB and Si deposition across the root in the Si accumulators rice and maize and the Si non-accumulator onion. Plants were cultivated in nutrient solution with and without Si supply. The CB development was determined in stained root cross-sections. The outer part of the roots containing the exodermis was isolated after enzymatic treatment. The exodermal suberin was transesterified with MeOH/BF3 and the chemical composition was measured using gas chromatography-mass spectroscopy (GC-MS) and flame ionization detector (GC-FID). Laser ablation-inductively coupled plasma-mass spectroscopy (LA-ICP-MS) was used to determine the Si deposition across root cross sections. Si promoted CB formation in the roots of Si-accumulator and Si non-accumulator species. The exodermal suberin was decreased in rice and maize due to decreased amounts of aromatic suberin fractions. Si did not affect the concentration of lignin and lignin-like polymers in the outer part of rice, maize and onion roots. The highest Si depositions were found in the tissues containing CB. These data along with literature were used to suggest a mechanism how Si promotes the CB development by forming complexes with phenols. PMID:26383862

Porous Silicon-Based Biosensors: Towards Real-Time Optical Detection of Target Bacteria in the Food Industry

PubMed Central

Massad-Ivanir, Naama; Shtenberg, Giorgi; Raz, Nitzan; Gazenbeek, Christel; Budding, Dries; Bos, Martine P.; Segal, Ester

2016-01-01

Rapid detection of target bacteria is crucial to provide a safe food supply and to prevent foodborne diseases. Herein, we present an optical biosensor for identification and quantification of Escherichia coli (E. coli, used as a model indicator bacteria species) in complex food industry process water. The biosensor is based on a nanostructured, oxidized porous silicon (PSi) thin film which is functionalized with specific antibodies against E. coli. The biosensors were exposed to water samples collected directly from process lines of fresh-cut produce and their reflectivity spectra were collected in real time. Process water were characterized by complex natural micro-flora (microbial load of >107 cell/mL), in addition to soil particles and plant cell debris. We show that process water spiked with culture-grown E. coli, induces robust and predictable changes in the thin-film optical interference spectrum of the biosensor. The latter is ascribed to highly specific capture of the target cells onto the biosensor surface, as confirmed by real-time polymerase chain reaction (PCR). The biosensors were capable of selectively identifying and quantifying the target cells, while the target cell concentration is orders of magnitude lower than that of other bacterial species, without any pre-enrichment or prior processing steps. PMID:27901131

Refractory Materials for Flame Deflector Protection System Corrosion Control: Similar Industries and/or Launch Facilities Survey

NASA Technical Reports Server (NTRS)

Calle, Luz Marina; Hintze, Paul E.; Parlier, Christopher R.; Coffman, Brekke E.; Sampson, Jeffrey W.; Kolody, Mark R.; Curran, Jerome P.; Perusich, Stephen A.; Trejo, David; Whitten, Mary C.;

Porous Silicon-Based Biosensors: Towards Real-Time Optical Detection of Target Bacteria in the Food Industry.

PubMed

Massad-Ivanir, Naama; Shtenberg, Giorgi; Raz, Nitzan; Gazenbeek, Christel; Budding, Dries; Bos, Martine P; Segal, Ester

2016-11-30

Rapid detection of target bacteria is crucial to provide a safe food supply and to prevent foodborne diseases. Herein, we present an optical biosensor for identification and quantification of Escherichia coli (E. coli, used as a model indicator bacteria species) in complex food industry process water. The biosensor is based on a nanostructured, oxidized porous silicon (PSi) thin film which is functionalized with specific antibodies against E. coli. The biosensors were exposed to water samples collected directly from process lines of fresh-cut produce and their reflectivity spectra were collected in real time. Process water were characterized by complex natural micro-flora (microbial load of >10 7  cell/mL), in addition to soil particles and plant cell debris. We show that process water spiked with culture-grown E. coli, induces robust and predictable changes in the thin-film optical interference spectrum of the biosensor. The latter is ascribed to highly specific capture of the target cells onto the biosensor surface, as confirmed by real-time polymerase chain reaction (PCR). The biosensors were capable of selectively identifying and quantifying the target cells, while the target cell concentration is orders of magnitude lower than that of other bacterial species, without any pre-enrichment or prior processing steps.

Porous Silicon-Based Biosensors: Towards Real-Time Optical Detection of Target Bacteria in the Food Industry

NASA Astrophysics Data System (ADS)

Massad-Ivanir, Naama; Shtenberg, Giorgi; Raz, Nitzan; Gazenbeek, Christel; Budding, Dries; Bos, Martine P.; Segal, Ester

2016-11-01

Rapid detection of target bacteria is crucial to provide a safe food supply and to prevent foodborne diseases. Herein, we present an optical biosensor for identification and quantification of Escherichia coli (E. coli, used as a model indicator bacteria species) in complex food industry process water. The biosensor is based on a nanostructured, oxidized porous silicon (PSi) thin film which is functionalized with specific antibodies against E. coli. The biosensors were exposed to water samples collected directly from process lines of fresh-cut produce and their reflectivity spectra were collected in real time. Process water were characterized by complex natural micro-flora (microbial load of >107 cell/mL), in addition to soil particles and plant cell debris. We show that process water spiked with culture-grown E. coli, induces robust and predictable changes in the thin-film optical interference spectrum of the biosensor. The latter is ascribed to highly specific capture of the target cells onto the biosensor surface, as confirmed by real-time polymerase chain reaction (PCR). The biosensors were capable of selectively identifying and quantifying the target cells, while the target cell concentration is orders of magnitude lower than that of other bacterial species, without any pre-enrichment or prior processing steps.

Polycrystalline silicon carbide dopant profiles obtained through a scanning nano-Schottky contact

DOE Office of Scientific and Technical Information (OSTI.GOV)

Golt, M. C.; Strawhecker, K. E.; Bratcher, M. S.

2016-07-14

The unique thermo-electro-mechanical properties of polycrystalline silicon carbide (poly-SiC) make it a desirable candidate for structural and electronic materials for operation in extreme environments. Necessitated by the need to understand how processing additives influence poly-SiC structure and electrical properties, the distribution of lattice defects and impurities across a specimen of hot-pressed 6H poly-SiC processed with p-type additives was visualized with high spatial resolution using a conductive atomic force microscopy approach in which a contact forming a nano-Schottky interface is scanned across the sample. The results reveal very intricate structures within poly-SiC, with each grain having a complex core-rim structure. Thismore » complexity results from the influence the additives have on the evolution of the microstructure during processing. It was found that the highest conductivities localized at rims as well as at the interface between the rim and the core. The conductivity of the cores is less than the conductivity of the rims due to a lower concentration of dopant. Analysis of the observed conductivities and current-voltage curves is presented in the context of nano-Schottky contact regimes where the conventional understanding of charge transport to diode operation is no longer valid.« less

Polycrystalline silicon carbide dopant profiles obtained through a scanning nano-Schottky contact

NASA Astrophysics Data System (ADS)

Golt, M. C.; Strawhecker, K. E.; Bratcher, M. S.; Shanholtz, E. R.

2016-07-01

The unique thermo-electro-mechanical properties of polycrystalline silicon carbide (poly-SiC) make it a desirable candidate for structural and electronic materials for operation in extreme environments. Necessitated by the need to understand how processing additives influence poly-SiC structure and electrical properties, the distribution of lattice defects and impurities across a specimen of hot-pressed 6H poly-SiC processed with p-type additives was visualized with high spatial resolution using a conductive atomic force microscopy approach in which a contact forming a nano-Schottky interface is scanned across the sample. The results reveal very intricate structures within poly-SiC, with each grain having a complex core-rim structure. This complexity results from the influence the additives have on the evolution of the microstructure during processing. It was found that the highest conductivities localized at rims as well as at the interface between the rim and the core. The conductivity of the cores is less than the conductivity of the rims due to a lower concentration of dopant. Analysis of the observed conductivities and current-voltage curves is presented in the context of nano-Schottky contact regimes where the conventional understanding of charge transport to diode operation is no longer valid.

Management of complex benign post-tracheostomy tracheal stenosis with bronchoscopic insertion of silicon tracheal stents, in patients with failed or contraindicated surgical reconstruction of trachea.

PubMed

Tsakiridis, Kosmas; Darwiche, Kaid; Visouli, Aikaterini N; Zarogoulidis, Paul; Machairiotis, Nikolaos; Christofis, Christos; Stylianaki, Aikaterini; Katsikogiannis, Nikolaos; Mpakas, Andreas; Courcoutsakis, Nicolaos; Zarogoulidis, Konstantinos

2012-11-01

Tracheal stenosis is a potentially life-threatening condition. Tracheostomy and endotracheal intubation remain the commonest causes of benign stenosis, despite improvements in design and management of tubes. Post-tracheostomy stenosis is more frequently encountered due to earlier performance of tracheostomy in the intensive care units, while the incidence of post-intubation stenosis has decreased with application of high-volume, low-pressure cuffs. In symptomatic benign tracheal stenosis the gold standard is surgical reconstruction (often after interventional bronchoscopy). Stenting is reserved for symptomatic tracheal narrowing deemed inoperable, due to local or general reasons: long strictures, inflammation, poor respiratory, cardiac or neurological status. When stenting is decided, silicone stent insertion is considered the treatment of choice in the presence of inflammation and/or when removal is desirable. We inserted tracheal silicone stents (Dumon) under general anaesthesia through rigid bronchoscopy in two patients with benign post-tracheostomy stenosis: a 39-year old woman with failed initial operation, and continuous relapses with proliferation after multiple bronchscopic interventions, and a 20-year old man in a poor neurological status, with a long tracheal stricture involving the subglottic larynx (lower posterior part), and inflamed tracheostomy site tissues (positive for methicillin resistant staphylococcus aureus). The airway was immediately re-establish, without complications. At 15- and 10-month follow-up (respectively) there was no stent migration, luminal patency was maintained without: adjacent structure erosion, secretion adherence inside the stents, granulation at the ends. Tracheostomy tissue inflammation was resolved (2(nd) patient), new infection was not noted. The patients maintain good respiratory function and will be evaluated for scheduled stent removal. Silicone stents are removable, resistant to microbial colonization and are associated with minimal granulation. In benign post-tracheostomy stenosis silicone stenting appeared safe and effective in re-stenosis after surgery and multiple bronchoscopic interventions, and in long stenosis, involving the lower posterior subglottic larynx in the presence on inflammation and poor neurological status.

Design and fabrication of non silicon substrate based MEMS energy harvester for arbitrary surface applications

NASA Astrophysics Data System (ADS)

Balpande, Suresh S.; Pande, Rajesh S.

2016-04-01

Internet of Things (IoT) uses MEMS sensor nodes and actuators to sense and control objects through Internet. IOT deploys millions of chemical battery driven sensors at different locations which are not reliable many times because of frequent requirement of charging & battery replacement in case of underground laying, placement at harsh environmental conditions, huge count and difference between demand (24 % per year) and availability (energy density growing rate 8% per year). Energy harvester fabricated on silicon wafers have been widely used in manufacturing MEMS structures. These devices require complex fabrication processes, costly chemicals & clean room. In addition to this silicon wafer based devices are not suitable for curved surfaces like pipes, human bodies, organisms, or other arbitrary surface like clothes, structure surfaces which does not have flat and smooth surface always. Therefore, devices based on rigid silicon wafers are not suitable for these applications. Flexible structures are the key solution for this problems. Energy transduction mechanism generates power from free surrounding vibrations or impact. Sensor nodes application has been purposefully selected due to discrete power requirement at low duty cycle. Such nodes require an average power budget in the range of about 0.1 microwatt to 1 mW over a period of 3-5 seconds. Energy harvester is the best alternate source in contrast with battery for sensor node application. Novel design of Energy Harvester based on cheapest flexible non silicon substrate i.e. cellulose acetate substrate have been modeled, simulated and analyzed on COMSOL multiphysics and fabricated using sol-gel spin coating setup. Single cantilever based harvester generates 60-75 mV peak electric potential at 22Hz frequency and approximately 22 µW power at 1K-Ohm load. Cantilever array can be employed for generating higher voltage by replicating this structure. This work covers design, optimization, fabrication of harvester and schottky diodes based voltage multiplier.

3D Integration for Wireless Multimedia

NASA Astrophysics Data System (ADS)

Kimmich, Georg

The convergence of mobile phone, internet, mapping, gaming and office automation tools with high quality video and still imaging capture capability is becoming a strong market trend for portable devices. High-density video encode and decode, 3D graphics for gaming, increased application-software complexity and ultra-high-bandwidth 4G modem technologies are driving the CPU performance and memory bandwidth requirements close to the PC segment. These portable multimedia devices are battery operated, which requires the deployment of new low-power-optimized silicon process technologies and ultra-low-power design techniques at system, architecture and device level. Mobile devices also need to comply with stringent silicon-area and package-volume constraints. As for all consumer devices, low production cost and fast time-to-volume production is key for success. This chapter shows how 3D architectures can bring a possible breakthrough to meet the conflicting power, performance and area constraints. Multiple 3D die-stacking partitioning strategies are described and analyzed on their potential to improve the overall system power, performance and cost for specific application scenarios. Requirements and maturity of the basic process-technology bricks including through-silicon via (TSV) and die-to-die attachment techniques are reviewed. Finally, we highlight new challenges which will arise with 3D stacking and an outlook on how they may be addressed: Higher power density will require thermal design considerations, new EDA tools will need to be developed to cope with the integration of heterogeneous technologies and to guarantee signal and power integrity across the die stack. The silicon/wafer test strategies have to be adapted to handle high-density IO arrays, ultra-thin wafers and provide built-in self-test of attached memories. New standards and business models have to be developed to allow cost-efficient assembly and testing of devices from different silicon and technology providers.

Design and fabrication of non silicon substrate based MEMS energy harvester for arbitrary surface applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balpande, Suresh S., E-mail: balpandes@rknec.edu; Pande, Rajesh S.

Internet of Things (IoT) uses MEMS sensor nodes and actuators to sense and control objects through Internet. IOT deploys millions of chemical battery driven sensors at different locations which are not reliable many times because of frequent requirement of charging & battery replacement in case of underground laying, placement at harsh environmental conditions, huge count and difference between demand (24 % per year) and availability (energy density growing rate 8% per year). Energy harvester fabricated on silicon wafers have been widely used in manufacturing MEMS structures. These devices require complex fabrication processes, costly chemicals & clean room. In addition tomore » this silicon wafer based devices are not suitable for curved surfaces like pipes, human bodies, organisms, or other arbitrary surface like clothes, structure surfaces which does not have flat and smooth surface always. Therefore, devices based on rigid silicon wafers are not suitable for these applications. Flexible structures are the key solution for this problems. Energy transduction mechanism generates power from free surrounding vibrations or impact. Sensor nodes application has been purposefully selected due to discrete power requirement at low duty cycle. Such nodes require an average power budget in the range of about 0.1 microwatt to 1 mW over a period of 3-5 seconds. Energy harvester is the best alternate source in contrast with battery for sensor node application. Novel design of Energy Harvester based on cheapest flexible non silicon substrate i.e. cellulose acetate substrate have been modeled, simulated and analyzed on COMSOL multiphysics and fabricated using sol-gel spin coating setup. Single cantilever based harvester generates 60-75 mV peak electric potential at 22Hz frequency and approximately 22 µW power at 1K-Ohm load. Cantilever array can be employed for generating higher voltage by replicating this structure. This work covers design, optimization, fabrication of harvester and schottky diodes based voltage multiplier.« less

Management of complex benign post-tracheostomy tracheal stenosis with bronchoscopic insertion of silicon tracheal stents, in patients with failed or contraindicated surgical reconstruction of trachea

PubMed Central

Tsakiridis, Kosmas; Darwiche, Kaid; Visouli, Aikaterini N.; Machairiotis, Nikolaos; Christofis, Christos; Stylianaki, Aikaterini; Katsikogiannis, Nikolaos; Mpakas, Andreas; Courcoutsakis, Nicolaos; Zarogoulidis, Konstantinos

2012-01-01

Tracheal stenosis is a potentially life-threatening condition. Tracheostomy and endotracheal intubation remain the commonest causes of benign stenosis, despite improvements in design and management of tubes. Post-tracheostomy stenosis is more frequently encountered due to earlier performance of tracheostomy in the intensive care units, while the incidence of post-intubation stenosis has decreased with application of high-volume, low-pressure cuffs. In symptomatic benign tracheal stenosis the gold standard is surgical reconstruction (often after interventional bronchoscopy). Stenting is reserved for symptomatic tracheal narrowing deemed inoperable, due to local or general reasons: long strictures, inflammation, poor respiratory, cardiac or neurological status. When stenting is decided, silicone stent insertion is considered the treatment of choice in the presence of inflammation and/or when removal is desirable. We inserted tracheal silicone stents (Dumon) under general anaesthesia through rigid bronchoscopy in two patients with benign post-tracheostomy stenosis: a 39-year old woman with failed initial operation, and continuous relapses with proliferation after multiple bronchscopic interventions, and a 20-year old man in a poor neurological status, with a long tracheal stricture involving the subglottic larynx (lower posterior part), and inflamed tracheostomy site tissues (positive for methicillin resistant staphylococcus aureus). The airway was immediately re-establish, without complications. At 15- and 10-month follow-up (respectively) there was no stent migration, luminal patency was maintained without: adjacent structure erosion, secretion adherence inside the stents, granulation at the ends. Tracheostomy tissue inflammation was resolved (2nd patient), new infection was not noted. The patients maintain good respiratory function and will be evaluated for scheduled stent removal. Silicone stents are removable, resistant to microbial colonization and are associated with minimal granulation. In benign post-tracheostomy stenosis silicone stenting appeared safe and effective in re-stenosis after surgery and multiple bronchoscopic interventions, and in long stenosis, involving the lower posterior subglottic larynx in the presence on inflammation and poor neurological status. PMID:23304439

Optical and Scanning Electron Microscopy of the Materials International Space Station Experiment (MISSE) Spacecraft Silicone Experiment

NASA Technical Reports Server (NTRS)

Hung, Ching-cheh; de Groh, Kim K.; Banks, Bruce A.

2012-01-01

Under a microscope, atomic oxygen (AO) exposed silicone surfaces are crazed and seen as "islands" separated by numerous crack lines, much analogous to mud-tile cracks. This research characterized and compared the degree of AO degradation of silicones by analyzing optical microscope images of samples exposed to low Earth orbit (LEO) AO as part of the Spacecraft Silicone Experiment. The Spacecraft Silicone Experiment consisted of eight DC 93-500 silicone samples exposed to eight different AO fluence levels (ranged from 1.46 to 8.43 10(exp 21) atoms/sq cm) during two different Materials International Space Station Experiment (MISSE) missions. Image analysis software was used to analyze images taken using a digital camera. To describe the morphological degradation of each AO exposed flight sample, three different parameters were selected and estimated: (1) average area of islands was determined and found to be in the 1000 to 3100 sq mm range; (2) total length of crack lines per unit area of the sample surface were determined and found to be in the range of 27 to 59 mm of crack length per sq mm of sample surface; and (3) the fraction of sample surface area that is occupied by crack lines was determined and found to be in the 25 to 56 percent range. In addition, average crack width can be estimated from crack length and crack area measurements and was calculated to be about 10 mm. Among the parameters studied, the fraction of sample surface area that is occupied by crack lines is believed to be most useful in characterizing the degree of silicone conversion to silicates by AO because its value steadily increases with increasing fluence over the entire fluence range. A series of SEM images from the eight samples exposed to different AO fluences suggest a complex sequence of surface stress due to surface shrinkage and crack formation, followed by re-distribution of stress and shrinking rate on the sample surface. Energy dispersive spectra (EDS) indicated that upon AO exposure, carbon content on the surface decreased relatively quickly at the beginning, to 32 percent of the pristine value for the least exposed sample in this set of experiments (1.46 10(exp 21) atoms/sq cm), but then decreased slowly, to 22 percent of the pristine value for the most exposed sample in this set of experiment (8.43 10(exp 21) atoms/sq cm). The oxygen content appears to increase at a slower rate. The least and most AO exposed samples were, respectively, 52 and 150 percent above the pristine values. The silicone samples with the greater AO exposure (7.75 10(exp 21) atoms/sq cm and higher) appear to have a surface layer which contains SiO2 with perhaps small amounts of unreacted silicone, CO and CO2 sealed inside.

Chemical vapor deposition and characterization of polysilanes polymer based thin films and their applications in compound semiconductors and silicon devices

NASA Astrophysics Data System (ADS)

Oulachgar, El Hassane

As the semiconductors industry is moving toward nanodevices, there is growing need to develop new materials and thin films deposition processes which could enable strict control of the atomic composition and structure of thin film materials in order to achieve precise control on their electrical and optical properties. The accurate control of thin film characteristics will become increasingly important as the miniaturization of semiconductor devices continue. There is no doubt that chemical synthesis of new materials and their self assembly will play a major role in the design and fabrication of next generation semiconductor devices. The objective of this work is to investigate the chemical vapor deposition (CVD) process of thin film using a polymeric precursor as a source material. This process offers many advantages including low deposition cost, hazard free working environment, and most importantly the ability to customize the polymer source material through polymer synthesis and polymer functionalization. The combination between polymer synthesis and CVD process will enable the design of new generation of complex thin film materials with a wide range of improved chemical, mechanical, electrical and optical properties which cannot be easily achieved through conventional CVD processes based on gases and small molecule precursors. In this thesis we mainly focused on polysilanes polymers and more specifically poly(dimethylsilanes). The interest in these polymers is motivated by their distinctive electronic and photonic properties which are attributed to the delocalization of the sigma-electron along the Si-Si backbone chain. These characteristics make polysilane polymers very promising in a broad range of applications as a dielectric, a semiconductor and a conductor. The polymer-based CVD process could be eventually extended to other polymer source materials such as polygermanes, as well as and a variety of other inorganic and hybrid organic-inorganic polymers. This work has demonstrated that a polysilane polymeric source can be used to deposit a wide range of thin film materials exhibiting similar properties with conventional ceramic materials such as silicon carbide (SiC), silicon oxynitride (SiON), silicon oxycarbide (SiOC) silicon dioxide (SiO2) and silicon nitride (Si3N4). The strict control of the deposition process allows precise control of the electrical, optical and chemical properties of polymer-based thin films within a broad range. This work has also demonstrated for the first time that poly(dimethylsilmaes) polymers deposited by CVD can be used to effectively passivate both silicon and gallium arsenide MOS devices. This finding makes polymer-based thin films obtained by CVD very promising for the development of high-kappa dielectric materials for next generation high-mobility CMOS technology. Keywords. Thin films, Polymers, Vapor Phase Deposition, CVD, Nanodielectrics, Organosilanes, Polysilanes, GaAs Passivation, MOSFET, Silicon Oxynitride, Integrated Waveguide, Silicon Carbide, Compound Semiconductors.

Buried oxide layer in silicon

DOEpatents

Sadana, Devendra Kumar; Holland, Orin Wayne

2001-01-01

A process for forming Silicon-On-Insulator is described incorporating the steps of ion implantation of oxygen into a silicon substrate at elevated temperature, ion implanting oxygen at a temperature below 200.degree. C. at a lower dose to form an amorphous silicon layer, and annealing steps to form a mixture of defective single crystal silicon and polycrystalline silicon or polycrystalline silicon alone and then silicon oxide from the amorphous silicon layer to form a continuous silicon oxide layer below the surface of the silicon substrate to provide an isolated superficial layer of silicon. The invention overcomes the problem of buried isolated islands of silicon oxide forming a discontinuous buried oxide layer.

Formation of porous silicon oxide from substrate-bound silicon rich silicon oxide layers by continuous-wave laser irradiation

NASA Astrophysics Data System (ADS)

Wang, Nan; Fricke-Begemann, Th.; Peretzki, P.; Ihlemann, J.; Seibt, M.

2018-03-01

Silicon nanocrystals embedded in silicon oxide that show room temperature photoluminescence (PL) have great potential in silicon light emission applications. Nanocrystalline silicon particle formation by laser irradiation has the unique advantage of spatially controlled heating, which is compatible with modern silicon micro-fabrication technology. In this paper, we employ continuous wave laser irradiation to decompose substrate-bound silicon-rich silicon oxide films into crystalline silicon particles and silicon dioxide. The resulting microstructure is studied using transmission electron microscopy techniques with considerable emphasis on the formation and properties of laser damaged regions which typically quench room temperature PL from the nanoparticles. It is shown that such regions consist of an amorphous matrix with a composition similar to silicon dioxide which contains some nanometric silicon particles in addition to pores. A mechanism referred to as "selective silicon ablation" is proposed which consistently explains the experimental observations. Implications for the damage-free laser decomposition of silicon-rich silicon oxides and also for controlled production of porous silicon dioxide films are discussed.

Two dimensional thermo-optic beam steering using a silicon photonic optical phased array

NASA Astrophysics Data System (ADS)

Mahon, Rita; Preussner, Marcel W.; Rabinovich, William S.; Goetz, Peter G.; Kozak, Dmitry A.; Ferraro, Mike S.; Murphy, James L.

2016-03-01

Components for free space optical communication terminals such as lasers, amplifiers, and receivers have all seen substantial reduction in both size and power consumption over the past several decades. However, pointing systems, such as fast steering mirrors and gimbals, have remained large, slow and power-hungry. Optical phased arrays provide a possible solution for non-mechanical beam steering devices that can be compact and lower in power. Silicon photonics is a promising technology for phased arrays because it has the potential to scale to many elements and may be compatible with CMOS technology thereby enabling batch fabrication. For most free space optical communication applications, two-dimensional beam steering is needed. To date, silicon photonic phased arrays have achieved two-dimensional steering by combining thermo-optic steering, in-plane, with wavelength tuning by means of an output grating to give angular tuning, out-of-plane. While this architecture might work for certain static communication links, it would be difficult to implement for moving platforms. Other approaches have required N2 controls for an NxN element phased array, which leads to complexity. Hence, in this work we demonstrate steering using the thermo-optic effect for both dimensions with a simplified steering mechanism requiring only two control signals, one for each steering dimension.

A low-cost, high-yield fabrication method for producing optimized biomimetic dry adhesives

NASA Astrophysics Data System (ADS)

Sameoto, D.; Menon, C.

2009-11-01

We present a low-cost, large-scale method of fabricating biomimetic dry adhesives. This process is useful because it uses all photosensitive polymers with minimum fabrication costs or complexity to produce molds for silicone-based dry adhesives. A thick-film lift-off process is used to define molds using AZ 9260 photoresist, with a slow acting, deep UV sensitive material, PMGI, used as both an adhesion promoter for the AZ 9260 photoresist and as an undercutting material to produce mushroom-shaped fibers. The benefits to this process are ease of fabrication, wide range of potential layer thicknesses, no special surface treatment requirements to demold silicone adhesives and easy stripping of the full mold if process failure does occur. Sylgard® 184 silicone is used to cast full sheets of biomimetic dry adhesives off 4" diameter wafers, and different fiber geometries are tested for normal adhesion properties. Additionally, failure modes of the adhesive during fabrication are noted and strategies for avoiding these failures are discussed. We use this fabrication method to produce different fiber geometries with varying cap diameters and test them for normal adhesion strengths. The results indicate that the cap diameters relative to post diameters for mushroom-shaped fibers dominate the adhesion properties.

Structure and Reactivity of Alucone-Coated Films on Si and Li(x)Si(y) Surfaces.

PubMed

Ma, Yuguang; Martinez de la Hoz, Julibeth M; Angarita, Ivette; Berrio-Sanchez, Jose M; Benitez, Laura; Seminario, Jorge M; Son, Seoung-Bum; Lee, Se-Hee; George, Steven M; Ban, Chunmei; Balbuena, Perla B

2015-06-10

Coating silicon particles with a suitable thin film has appeared as a possible solution to accommodate the swelling of silicon upon lithiation and its posterior cracking and pulverization during cycling of Li-ion batteries. In particular, aluminum alkoxide (alucone) films have been recently deposited over Si anodes, and the lithiation and electrochemical behavior of the system have been characterized. However, some questions remain regarding the lithium molecular migration mechanisms through the film and the electronic properties of the alucone film. Here we use density functional theory, ab initio molecular dynamics simulations, and Green's function theory to examine the film formation, lithiation, and reactivity in contact with an electrolyte solution. It is found that the film is composed of Al-O complexes with 3-O or 4-O coordination. During lithiation, Li atoms bind very strongly to the O atoms in the most energetically favorable sites. After the film is irreversibly saturated with Li atoms, it becomes electronically conductive. The ethylene carbonate molecules in liquid phase are found to be reduced at the surface of the Li-saturated alucone film following similar electron transfer mechanisms as found previously for lithiated silicon anodes. The theoretical results are in agreement with those from morphology and electrochemical analyses.

Development of the anode bipolar plate/membrane assembly unit for air breathing PEMFC stack using silicone adhesive bonding

NASA Astrophysics Data System (ADS)

Kim, Minkook; Lee, Dai Gil

2016-05-01

Polymer electrolyte membrane fuel cells (PEMFC) exhibit a wide power range, low operating temperature, high energy density and long life time. These advantages favor PEMFC for applications such as vehicle power sources, portable power, and backup power applications. With the push towards the commercialization of PEMFC, especially for portable power applications, the overall balance of plants (BOPs) of the systems should be minimized. To reduce the mass and complexity of the systems, air-breathing PEMFC stack design with open cathode channel configuration is being developed. However, the open cathode channel configuration incurs hydrogen leakage problem. In this study, the bonding strength of a silicon adhesive between the Nafion membrane and the carbon fiber/epoxy composite bipolar plate was measured. Then, an anode bipolar plate/membrane assembly unit which was bonded with the silicone adhesive was developed to solve the hydrogen leakage problem. The reliability of the anode bipolar plate/membrane assembly unit was estimated under the internal pressure of hydrogen by the FE analysis. Additionally, the gas sealability of the developed air breathing PEMFC unit cell was experimentally measured. Finally, unit cell performance of the developed anode bipolar plate/membrane assembly unit was tested and verified under operating conditions without humidity and temperature control.

All-optical control of light on a graphene-on-silicon nitride chip using thermo-optic effect.

PubMed

Qiu, Ciyuan; Yang, Yuxing; Li, Chao; Wang, Yifang; Wu, Kan; Chen, Jianping

2017-12-06

All-optical signal processing avoids the conversion between optical signals and electronic signals and thus has the potential to achieve a power efficient photonic system. Micro-scale all-optical devices for light manipulation are the key components in the all-optical signal processing and have been built on the semiconductor platforms (e.g., silicon and III-V semiconductors). However, the two-photon absorption (TPA) effect and the free-carrier absorption (FCA) effect in these platforms deteriorate the power handling and limit the capability to realize complex functions. Instead, silicon nitride (Si 3 N 4 ) provides a possibility to realize all-optical large-scale integrated circuits due to its insulator nature without TPA and FCA. In this work, we investigate the physical dynamics of all-optical control on a graphene-on-Si 3 N 4 chip based on thermo-optic effect. In the experimental demonstration, a switching response time constant of 253.0 ns at a switching energy of ~50 nJ is obtained with a device dimension of 60 μm × 60 μm, corresponding to a figure of merit (FOM) of 3.0 nJ mm. Detailed coupled-mode theory based analysis on the thermo-optic effect of the device has been performed.

Label-free virus detection using silicon photonic microring resonators

PubMed Central

McClellan, Melinda S.; Domier, Leslie L; Bailey, Ryan C.

2013-01-01

Viruses represent a continual threat to humans through a number of mechanisms, which include disease, bioterrorism, and destruction of both plant and animal food resources. Many contemporary techniques used for the detection of viruses and viral infections suffer from limitations such as the need for extensive sample preparation or the lengthy window between infection and measurable immune response, for serological methods. In order to develop a method that is fast, cost-effective, and features reduced sample preparation compared to many other virus detection methods, we report the application of silicon photonic microring resonators for the direct, label-free detection of intact viruses in both purified samples as well as in a complex, real-world analytical matrix. As a model system, we demonstrate the quantitative detection of Bean pod mottle virus, a pathogen of great agricultural importance, with a limit of detection of 10 ng/mL. By simply grinding a small amount of leaf sample in buffer with a mortar and pestle, infected leaves can be identified over a healthy control with a total analysis time of less than 45 min. Given the inherent scalability and multiplexing capability of the semiconductor-based technology, we feel that silicon photonic microring resonators are well-positioned as a promising analytical tool for a number of viral detection applications. PMID:22138465

Method of forming buried oxide layers in silicon

DOEpatents

Sadana, Devendra Kumar; Holland, Orin Wayne

2000-01-01

A process for forming Silicon-On-Insulator is described incorporating the steps of ion implantation of oxygen into a silicon substrate at elevated temperature, ion implanting oxygen at a temperature below 200.degree. C. at a lower dose to form an amorphous silicon layer, and annealing steps to form a mixture of defective single crystal silicon and polycrystalline silicon or polycrystalline silicon alone and then silicon oxide from the amorphous silicon layer to form a continuous silicon oxide layer below the surface of the silicon substrate to provide an isolated superficial layer of silicon. The invention overcomes the problem of buried isolated islands of silicon oxide forming a discontinuous buried oxide layer.

Method and apparatus for stable silicon dioxide layers on silicon grown in silicon nitride ambient

NASA Technical Reports Server (NTRS)

Cohen, R. A.; Wheeler, R. K. (Inventor)

1974-01-01

A method and apparatus for thermally growing stable silicon dioxide layers on silicon is disclosed. A previously etched and baked silicon nitride tube placed in a furnace is used to grow the silicon dioxide. First, pure oxygen is allowed to flow through the tube to initially coat the inside surface of the tube with a thin layer of silicon dioxide. After the tube is coated with the thin layer of silicon dioxide, the silicon is oxidized thermally in a normal fashion. If the tube becomes contaminated, the silicon dioxide is etched off thereby exposing clean silicon nitride and then the inside of the tube is recoated with silicon dioxide. As is disclosed, the silicon nitride tube can also be used as the ambient for the pyrolytic decomposition of silane and ammonia to form thin layers of clean silicon nitride.

RF performances of inductors integrated on localized p+-type porous silicon regions

PubMed Central

2012-01-01

To study the influence of localized porous silicon regions on radiofrequency performances of passive devices, inductors were integrated on localized porous silicon regions, full porous silicon sheet, bulk silicon and glass substrates. In this work, a novel strong, resistant fluoropolymer mask is introduced to localize the porous silicon on the silicon wafer. Then, the quality factors and resonant frequencies obtained with the different substrates are presented. A first comparison is done between the performances of inductors integrated on same-thickness localized and full porous silicon sheet layers. The effect of the silicon regions in the decrease of performances of localized porous silicon is discussed. Then, the study shows that the localized porous silicon substrate significantly reduces losses in comparison with high-resistivity silicon or highly doped silicon bulks. These results are promising for the integration of both passive and active devices on the same silicon/porous silicon hybrid substrate. PMID:23009746

Experimental validation of numerical simulations on a cerebral aneurysm phantom model

PubMed Central

Seshadhri, Santhosh; Janiga, Gábor; Skalej, Martin; Thévenin, Dominique

2012-01-01

The treatment of cerebral aneurysms, found in roughly 5% of the population and associated in case of rupture to a high mortality rate, is a major challenge for neurosurgery and neuroradiology due to the complexity of the intervention and to the resulting, high hazard ratio. Improvements are possible but require a better understanding of the associated, unsteady blood flow patterns in complex 3D geometries. It would be very useful to carry out such studies using suitable numerical models, if it is proven that they reproduce accurately enough the real conditions. This validation step is classically based on comparisons with measured data. Since in vivo measurements are extremely difficult and therefore of limited accuracy, complementary model-based investigations considering realistic configurations are essential. In the present study, simulations based on computational fluid dynamics (CFD) have been compared with in situ, laser-Doppler velocimetry (LDV) measurements in the phantom model of a cerebral aneurysm. The employed 1:1 model is made from transparent silicone. A liquid mixture composed of water, glycerin, xanthan gum and sodium chloride has been specifically adapted for the present investigation. It shows physical flow properties similar to real blood and leads to a refraction index perfectly matched to that of the silicone model, allowing accurate optical measurements of the flow velocity. For both experiments and simulations, complex pulsatile flow waveforms and flow rates were accounted for. This finally allows a direct, quantitative comparison between measurements and simulations. In this manner, the accuracy of the employed computational model can be checked. PMID:24265876

[Study of purity tests for silicone resins].

PubMed

Sato, Kyoko; Otsuki, Noriko; Ohori, Akio; Chinda, Mitsuru; Furusho, Noriko; Osako, Tsutomu; Akiyama, Hiroshi; Kawamura, Yoko

2012-01-01

In the 8th edition of Japan's Specifications and Standards for Food Additives, the purity test for silicone resins requires the determination of the refractive index and kinetic viscosity of the extracted silicone oil, and allows for only a limited amount of silicon dioxide. In the purity test, carbon tetrachloride is used to separate the silicone oil and silicon dioxide. To exclude carbon tetrachloride, methods were developed for separating the silicone oil and silicon dioxide from silicone resin, which use hexane and 10% n-dodecylbenzenesulfonic acid in hexane. For silicone oil, the measured refractive index and kinetic viscosity of the silicone oil obtained from the hexane extract were shown to be equivalent to those of the intact silicone oil. In regard to silicon dioxide, it was confirmed that, following the separation with 10% n-dodecylbenzenesulfonic acid in hexane, the level of silicon dioxide in silicone resin can be accurately determined. Therefore, in this study, we developed a method for testing the purity of silicone resins without the use of carbon tetrachloride, which is a harmful reagent.

High temperature latent heat thermal energy storage to augment solar thermal propulsion for microsatellites

NASA Astrophysics Data System (ADS)

Gilpin, Matthew R.

Solar thermal propulsion (STP) offers an unique combination of thrust and efficiency, providing greater total DeltaV capability than chemical propulsion systems without the order of magnitude increase in total mission duration associated with electric propulsion. Despite an over 50 year development history, no STP spacecraft has flown to-date as both perceived and actual complexity have overshadowed the potential performance benefit in relation to conventional technologies. The trend in solar thermal research over the past two decades has been towards simplification and miniaturization to overcome this complexity barrier in an effort finally mount an in-flight test. A review of micro-propulsion technologies recently conducted by the Air Force Research Laboratory (AFRL) has identified solar thermal propulsion as a promising configuration for microsatellite missions requiring a substantial Delta V and recommended further study. A STP system provides performance which cannot be matched by conventional propulsion technologies in the context of the proposed microsatellite ''inspector" requiring rapid delivery of greater than 1500 m/s DeltaV. With this mission profile as the target, the development of an effective STP architecture goes beyond incremental improvements and enables a new class of microsatellite missions. Here, it is proposed that a bi-modal solar thermal propulsion system on a microsatellite platform can provide a greater than 50% increase in Delta V vs. chemical systems while maintaining delivery times measured in days. The realization of a microsatellite scale bi-modal STP system requires the integration of multiple new technologies, and with the exception of high performance thermal energy storage, the long history of STP development has provided "ready" solutions. For the target bi-modal STP microsatellite, sensible heat thermal energy storage is insufficient and the development of high temperature latent heat thermal energy storage is an enabling technology for the platform. The use of silicon and boron as high temperature latent heat thermal energy storage materials has been in the background of solar thermal research for decades without a substantial investigation. This is despite a broad agreement in the literature about the performance benefits obtainable from a latent heat mechanisms which provides a high energy storage density and quasi-isothermal heat release at high temperature. In this work, an experimental approach was taken to uncover the practical concerns associated specifically with applying silicon as an energy storage material. A new solar furnace was built and characterized enabling the creation of molten silicon in the laboratory. These tests have demonstrated the basic feasibility of a molten silicon based thermal energy storage system and have highlighted asymmetric heat transfer as well as silicon expansion damage to be the primary engineering concerns for the technology. For cylindrical geometries, it has been shown that reduced fill factors can prevent damage to graphite walled silicon containers at the expense of decreased energy storage density. Concurrent with experimental testing, a cooling model was written using the "enthalpy method" to calculate the phase change process and predict test section performance. Despite a simplistic phase change model, and experimentally demonstrated complexities of the freezing process, results coincided with experimental data. It is thus possible to capture essential system behaviors of a latent heat thermal energy storage system even with low fidelity freezing kinetics modeling allowing the use of standard tools to obtain reasonable results. Finally, a technological road map is provided listing extant technological concerns and potential solutions. Improvements in container design and an increased understanding of convective coupling efficiency will ultimately enable both high temperature latent heat thermal energy storage and a new class of high performance bi-modal solar thermal spacecraft.

Pressure Studies of Protein Dynamics

DTIC Science & Technology

1990-02-28

a frozen and metastable complex system In the present section was generated by a flashlamp-pumped dye laser (Phase-R DL- treat the equilibrium region...determination of the relative thermodynamic parameters of the and the temperature was monitored with a Si diode on the pressure We assume that the A substates...temperature controller (Model proteins is essentially linear from 200 to 320 K. 2" The entropy 93C). A silicon diode mounted on the sample cell

Structures and Techniques For Implementing and Packaging Complex, Large Scale Microelectromechanical Systems Using Foundry Fabrication Processes.

DTIC Science & Technology

1996-06-01

switches 5-43 Figure 5-27. Mechanical interference between ’Pull Spring’ devices 5-45 Figure 5-28. Array of LIGA mechanical relay switches 5-49...like coating DM Direct metal interconnect technique DMD ™ Digital Micromirror Device EDP Ethylene, diamine, pyrocatechol and water; silicon anisotropic...mechanical systems MOSIS MOS Implementation Service PGA Pin grid array, an electronic die package PZT Lead-zirconate-titanate LIGA Lithographie

Fabrication of injection molded sintered alpha SiC turbine components

NASA Technical Reports Server (NTRS)

Storm, R. S.; Ohnsorg, R. W.; Frechette, F. J.

1981-01-01

Fabrication of a sintered alpha silicon carbide turbine blade by injection molding is described. An extensive process variation matrix was carried out to define the optimum fabrication conditions. Variation of molding parameters had a significant impact on yield. Turbine blades were produced in a reasonable yield which met a rigid quality and dimensional specification. Application of injection molding technology to more complex components such as integral rotors is also described.

Artificial-life researchers try to create social reality.

PubMed

Flam, F

1994-08-12

Some scientists, among them cosmologist Stephen Hawking, argue that computer viruses are alive. A better case might be made for many of the self-replicating silicon-based creatures featured at the fourth Conference on Artificial Life, held on 5 to 8 July in Boston. Researchers from computer science, biology, and other disciplines presented computer programs that, among other things, evolved cooperative strategies in a selfish world and recreated themselves in ever more complex forms.

The SiO Masers of TX Camelopardalis

NASA Astrophysics Data System (ADS)

Marvel, Kevin B.; Diamond, P.; Kemball, A.

2001-06-01

Observations of evolved stars with the Very Long Baseline Array have shown that silicon monoxide masers are found just above the photospheres of these interesting objects. By observing many times over a few pulsation periods, researchers are now discovering complex motions in the extended photospheres of these bloated, old stars. We will present several dramatic "movies" of these sources and speculate on wat such observations can tell us about the physical conditions near the star.

Aluminum acceptor four particle bound exciton complex in 4H, 6H, and 3C SiC

NASA Technical Reports Server (NTRS)

Clemen, L. L.; Devaty, R. P.; Macmillan, M. F.; Yoganathan, M.; Choyke, W. J.; Larkin, D. J.; Powell, J. A.; Edmond, J. A.; Kong, H. S.

1993-01-01

Evidence is presented for a four particle acceptor complex in 3C, 6H, and 4H SiC, obtained in low-temperature photoluminescence and cathodoluminescence experiments. The new lines were observed in p-type films lightly doped with aluminum, of 6H, 4H, and 3C SiC grown on the silicon (0001) face of 6H SiC under special conditions. The lines increase in intensity as more aluminum is added during growth. The multiplicity of observed lines is consistent with symmetry-based models similar to those which have been proposed to describe 4A centers in p-type zincblende semiconductors.

Silicone Liner-Free Pressure Sensitive Adhesive Labels

NASA Astrophysics Data System (ADS)

Empereur, Johanne; Chaussy, Didier; Belgacem, Mohamed Naceur

2008-08-01

Pressure sensitive adhesives (PSA) were microencapsulated using simple and complex coacervation and aminoplaste. The microcapsules thus prepared were characterized by FTIR spectroscopy, particle size distribution, rheological behavior and peeling tests. The microcapsules were isolated and found to be out of sticky indicating that the PSAs were indeed encapsulated. The prepared suspensions were deposited at the surface of a paper sheets and the dried labels were then pressed against each other. The ensuing complex was then characterized in terms of peeling forces and showed that the encapsulation using aminoplaste technique of a commercial PSA yielded peel energy of 170 J/m2, which constitutes the recovering of about 68% of the adhesive power of the original non encapsulated PSA.

MDTS: automatic complex materials design using Monte Carlo tree search.

PubMed

M Dieb, Thaer; Ju, Shenghong; Yoshizoe, Kazuki; Hou, Zhufeng; Shiomi, Junichiro; Tsuda, Koji

2017-01-01

Complex materials design is often represented as a black-box combinatorial optimization problem. In this paper, we present a novel python library called MDTS (Materials Design using Tree Search). Our algorithm employs a Monte Carlo tree search approach, which has shown exceptional performance in computer Go game. Unlike evolutionary algorithms that require user intervention to set parameters appropriately, MDTS has no tuning parameters and works autonomously in various problems. In comparison to a Bayesian optimization package, our algorithm showed competitive search efficiency and superior scalability. We succeeded in designing large Silicon-Germanium (Si-Ge) alloy structures that Bayesian optimization could not deal with due to excessive computational cost. MDTS is available at https://github.com/tsudalab/MDTS.

Complex optimization for big computational and experimental neutron datasets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bao, Feng; Oak Ridge National Lab.; Archibald, Richard

Here, we present a framework to use high performance computing to determine accurate solutions to the inverse optimization problem of big experimental data against computational models. We demonstrate how image processing, mathematical regularization, and hierarchical modeling can be used to solve complex optimization problems on big data. We also demonstrate how both model and data information can be used to further increase solution accuracy of optimization by providing confidence regions for the processing and regularization algorithms. Finally, we use the framework in conjunction with the software package SIMPHONIES to analyze results from neutron scattering experiments on silicon single crystals, andmore » refine first principles calculations to better describe the experimental data.« less

System on a Chip (SoC) Overview

NASA Technical Reports Server (NTRS)

LaBel, Kenneth A.

2010-01-01

System-on-a-chip or system on chip (SoC or SOC) refers to integrating all components of a computer or other electronic system into a single integrated circuit (chip). It may contain digital, analog, mixed-signal, and often radio-frequency functions all on a single chip substrate. Complexity drives it all: Radiation tolerance and testability are challenges for fault isolation, propagation, and validation. Bigger single silicon die than flown before and technology is scaling below 90nm (new qual methods). Packages have changed and are bigger and more difficult to inspect, test, and understand. Add in embedded passives. Material interfaces are more complex (underfills, processing). New rules for board layouts. Mechanical and thermal designs, etc.

MDTS: automatic complex materials design using Monte Carlo tree search

NASA Astrophysics Data System (ADS)

Dieb, Thaer M.; Ju, Shenghong; Yoshizoe, Kazuki; Hou, Zhufeng; Shiomi, Junichiro; Tsuda, Koji

2017-12-01

Complex materials design is often represented as a black-box combinatorial optimization problem. In this paper, we present a novel python library called MDTS (Materials Design using Tree Search). Our algorithm employs a Monte Carlo tree search approach, which has shown exceptional performance in computer Go game. Unlike evolutionary algorithms that require user intervention to set parameters appropriately, MDTS has no tuning parameters and works autonomously in various problems. In comparison to a Bayesian optimization package, our algorithm showed competitive search efficiency and superior scalability. We succeeded in designing large Silicon-Germanium (Si-Ge) alloy structures that Bayesian optimization could not deal with due to excessive computational cost. MDTS is available at https://github.com/tsudalab/MDTS.

Complex optimization for big computational and experimental neutron datasets

DOE PAGES

Bao, Feng; Oak Ridge National Lab.; Archibald, Richard; ...

2016-11-07

Here, we present a framework to use high performance computing to determine accurate solutions to the inverse optimization problem of big experimental data against computational models. We demonstrate how image processing, mathematical regularization, and hierarchical modeling can be used to solve complex optimization problems on big data. We also demonstrate how both model and data information can be used to further increase solution accuracy of optimization by providing confidence regions for the processing and regularization algorithms. Finally, we use the framework in conjunction with the software package SIMPHONIES to analyze results from neutron scattering experiments on silicon single crystals, andmore » refine first principles calculations to better describe the experimental data.« less

Asynchronous oscillations of rigid rods drive viscous fluid to swirl

NASA Astrophysics Data System (ADS)

Hayashi, Rintaro; Takagi, Daisuke

2017-12-01

We present a minimal system for generating flow at low Reynolds number by oscillating a pair of rigid rods in silicone oil. Experiments show that oscillating them in phase produces no net flow, but a phase difference alone can generate rich flow fields. Tracer particles follow complex trajectory patterns consisting of small orbital movements every cycle and then drifting or swirling in larger regions after many cycles. Observations are consistent with simulations performed using the method of regularized Stokeslets, which reveal complex three-dimensional flow structures emerging from simple oscillatory actuation. Our findings reveal the basic underlying flow structure around oscillatory protrusions such as hairs and legs as commonly featured on living and nonliving bodies.

Investigation of polymer derived ceramics cantilevers for application of high speed atomic force microscopy

NASA Astrophysics Data System (ADS)

Wu, Chia-Yun

High speed Atomic Force Microscopy (AFM) has a wide variety of applications ranging from nanomanufacturing to biophysics. In order to have higher scanning speed of certain AFM modes, high resonant frequency cantilevers are needed; therefore, the goal of this research is to investigate using polymer derived ceramics for possible applications in making high resonant frequency AFM cantilevers using complex cross sections. The polymer derived ceramic that will be studied, is silicon carbide. Polymer derived ceramics offer a potentially more economic fabrication approach for MEMS due to their relatively low processing temperatures and ease of complex shape design. Photolithography was used to make the desired cantilever shapes with micron scale size followed by a wet etching process to release the cantilevers from the substrates. The whole manufacturing process we use borrow well-developed techniques from the semiconducting industry, and as such this project also could offer the opportunity to reduce the fabrication cost of AFM cantilevers and MEMS in general. The characteristics of silicon carbide made from the precursor polymer, SMP-10 (Starfire Systems), were studied. In order to produce high qualities of silicon carbide cantilevers, where the major concern is defects, proper process parameters needed to be determined. Films of polymer derived ceramics often have defects due to shrinkage during the conversion process. Thus control of defects was a central issue in this study. A second, related concern was preventing oxidation; the polymer derived ceramics we chose is easily oxidized during processing. Establishing an environment without oxygen in the whole process was a significant challenge in the project. The optimization of the parameters for using photolithography and wet etching process was the final and central goal of the project; well established techniques used in microfabrication were modified for use in making the cantilever in the project. The techniques developed here open a path to the fabrication of cantilevers with unconventional cross sections.

New 3D structuring process for non-integrated circuit related technologies (Conference Presentation)

NASA Astrophysics Data System (ADS)

Nouri, Lamia; Possémé, Nicolas; Landis, Stéfan; Milesi, Frédéric; Gaillard, Frédéric-Xavier

2017-04-01

Fabrication processes that microelectronic developed for Integrated circuit (IC) technologies for decades, do not meet the new emerging structuration's requirements, in particular non-IC related technologies one, such as MEMS/NEMS, Micro-Fluidics, photovoltaics, lenses. Actually complex 3D structuration requires complex lithography patterning approaches such as gray-scale electron beam lithography, laser ablation, focused ion beam lithography, two photon polymerization. It is now challenging to find cheaper and easiest technique to achieve 3D structures. In this work, we propose a straightforward process to realize 3D structuration, intended for silicon based materials (Si, SiN, SiOCH). This structuration technique is based on nano-imprint lithography (NIL), ion implantation and selective wet etching. In a first step a pattern is performed by lithography on a substrate, then ion implantation is realized through a resist mask in order to create localized modifications in the material, thus the pattern is transferred into the subjacent layer. Finally, after the resist stripping, a selective wet etching is carried out to remove selectively the modified material regarding the non-modified one. In this paper, we will first present results achieved with simple 2D line array pattern processed either on Silicon or SiOCH samples. This step have been carried out to demonstrate the feasibility of this new structuration process. SEM pictures reveals that "infinite" selectivity between the implanted areas versus the non-implanted one could be achieved. We will show that a key combination between the type of implanted ion species and wet etching chemistries is required to obtain such results. The mechanisms understanding involved during both implantation and wet etching processes will also be presented through fine characterizations with Photoluminescence, Raman and Secondary Ion Mass Spectrometry (SIMS) for silicon samples, and ellipso-porosimetry and Fourier Transform InfraRed spectroscopy (FTIR) for SiOCH samples. Finally the benefit of this new patterning approach will be presented on 3D patterns structures.

Ultrafast carrier thermalization and trapping in silicon-germanium alloy probed by extreme ultraviolet transient absorption spectroscopy

DOE PAGES

Zürch, Michael; Chang, Hung-Tzu; Kraus, Peter M.; ...

2017-06-06

Semiconductor alloys containing silicon and germanium are of growing importance for compact and highly efficient photonic devices due to their favorable properties for direct integration into silicon platforms and wide tunability of optical parameters. Here, we report the simultaneous direct and energy-resolved probing of ultrafast electron and hole dynamics in a silicon-germanium alloy with the stoichiometry Si 0.25Ge 0.75 by extreme ultraviolet transient absorption spectroscopy. Probing the photoinduced dynamics of charge carriers at the germanium M 4,5-edge (~30 eV) allows the germanium atoms to be used as reporter atoms for carrier dynamics in the alloy. The photoexcitation of electrons acrossmore » the direct and indirect band gap into conduction band (CB) valleys and their subsequent hot carrier relaxation are observed and compared to pure germanium, where the Ge direct (ΔE gap,Ge,direct = 0.8 eV) and Si 0.25Ge 0.75 indirect gaps (ΔE gap,Si0.25Ge0.75,indirect = 0.95 eV) are comparable in energy. In the alloy, comparable carrier lifetimes are observed for the X, L, and Γ valleys in the conduction band. A midgap feature associated with electrons accumulating in trap states near the CB edge following intraband thermalization is observed in the Si 0.25Ge 0.75 alloy. The successful implementation of the reporter atom concept for capturing the dynamics of the electronic bands by site-specific probing in solids opens a route to study carrier dynamics in more complex materials with femtosecond and sub-femtosecond temporal resolution.« less

[Glaucoma and retinal surgery].

PubMed

Müller, M; Geerling, G; Zierhut, M; Klink, T

2010-05-01

In the therapeutic approach to complex glaucomas different initial situations were considered: pre-existing glaucoma, induction of glaucoma after vitreoretinal surgery and antiglaucomatous procedures. In pre-existing glaucoma and after filtering surgery maintenance of the filtering bleb requires a vitreoretinal approach for conjunctiva preservation with techniques such as pneumatic retinopexy or small gauge vitrectomy. After vitreoretinal surgery an increase in intraocular pressure (IOP) is common. Secondary glaucoma may occur after scleral buckling and after vitrectomy with or without gas or silicone oil tamponade as well as after application of steroids. Angle closure glaucoma after scleral buckling develops because of congestion and anterior rotation of the ciliary body. Vitreous tamponades with expansive or saturated gases may cause angle-closure glaucoma with or without pupillary blockage and may critically shorten ocular perfusion. Postoperative checks, immediate action and a ban on boarding aircraft over the period of intraocular gas tamponade prevent permanent damage to the eye. The majority of secondary glaucomas can effectively be controlled by topical medication and adequate postoperative posture of the patient. Besides the temporary use of systemic antiglaucomatous medication or laser therapy, very rarely in cases of massive swelling or overfill, a direct intervention, such as partial gas or silicone oil removal is required. A prophylactic inferior peripheral iridectomy prevents pupillary blockage in aphakic eyes with intraocular tamponade. In cases of heavy silicone oil use, the peripheral iridectomy is placed in the superior position. Nd:YAG laser application will regulate IOP in cases of occlusion. Secondary glaucoma due to silicone oil emulsification overload is treated by trabecular meshwork aspiration and lavage. In refractory glaucoma repetitive cyclophotocoagulation and drainage implants represent an approved method for long-term IOP regulation. The underlying cause of secondary glaucoma after vitreoretinal surgery is often multifactorial in nature and may benefit from an exact analysis for an adequate and successful treatment regimen.

Laser Doppler imaging of cutaneous blood flow through transparent face masks: a necessary preamble to computer-controlled rapid prototyping fabrication with submillimeter precision.

PubMed

Allely, Rebekah R; Van-Buendia, Lan B; Jeng, James C; White, Patricia; Wu, Jingshu; Niszczak, Jonathan; Jordan, Marion H

2008-01-01

A paradigm shift in management of postburn facial scarring is lurking "just beneath the waves" with the widespread availability of two recent technologies: precise three-dimensional scanning/digitizing of complex surfaces and computer-controlled rapid prototyping three-dimensional "printers". Laser Doppler imaging may be the sensible method to track the scar hyperemia that should form the basis of assessing progress and directing incremental changes in the digitized topographical face mask "prescription". The purpose of this study was to establish feasibility of detecting perfusion through transparent face masks using the Laser Doppler Imaging scanner. Laser Doppler images of perfusion were obtained at multiple facial regions on five uninjured staff members. Images were obtained without a mask, followed by images with a loose fitting mask with and without a silicone liner, and then with a tight fitting mask with and without a silicone liner. Right and left oblique images, in addition to the frontal images, were used to overcome unobtainable measurements at the extremes of face mask curvature. General linear model, mixed model, and t tests were used for data analysis. Three hundred seventy-five measurements were used for analysis, with a mean perfusion unit of 299 and pixel validity of 97%. The effect of face mask pressure with and without the silicone liner was readily quantified with significant changes in mean cutaneous blood flow (P < .5). High valid pixel rate laser Doppler imager flow data can be obtained through transparent face masks. Perfusion decreases with the application of pressure and with silicone. Every participant measured differently in perfusion units; however, consistent perfusion patterns in the face were observed.

Novel detectors for silicon based microdosimetry, their concepts and applications

NASA Astrophysics Data System (ADS)

Rosenfeld, Anatoly B.

2016-02-01

This paper presents an overview of the development of semiconductor microdosimetry and the most current (state-of-the-art) Silicon on Insulator (SOI) detectors for microdosimetry based mainly on research and development carried out at the Centre for Medical Radiation Physics (CMRP) at the University of Wollongong with collaborators over the last 18 years. In this paper every generation of CMRP SOI microdosimeters, including their fabrication, design, and electrical and charge collection characterisation are presented. A study of SOI microdosimeters in various radiation fields has demonstrated that under appropriate geometrical scaling, the response of SOI detectors with the well-known geometry of microscopically sensitive volumes will record the energy deposition spectra representative of tissue cells of an equivalent shape. This development of SOI detectors for microdosimetry with increased complexity has improved the definition of microscopic sensitive volume (SV), which is modelling the deposition of ionising energy in a biological cell, that are led from planar to 3D SOI detectors with an array of segmented microscopic 3D SVs. The monolithic ΔE-E silicon telescope, which is an alternative to the SOI silicon microdosimeter, is presented, and as an example, applications of SOI detectors and ΔE-E monolithic telescope for microdosimetery in proton therapy field and equivalent neutron dose measurements out of field are also presented. An SOI microdosimeter "bridge" with 3D SVs can derive the relative biological effectiveness (RBE) in 12C ion radiation therapy that matches the tissue equivalent proportional counter (TEPC) quite well, but with outstanding spatial resolution. The use of SOI technology in experimental microdosimetry offers simplicity (no gas system or HV supply), high spatial resolution, low cost, high count rates, and the possibility of integrating the system onto a single device with other types of detectors.

Improved silicon carbide for advanced heat engines

NASA Technical Reports Server (NTRS)

Whalen, T. J.; Winterbottom, W. L.

1986-01-01

Work performed to develop silicon carbide materials of high strength and to form components of complex shape and high reliability is described. A beta-SiC powder and binder system was adapted to the injection molding process and procedures and process parameters developed capable of providing a sintered silicon carbide material with improved properties. The initial effort has been to characterize the baseline precursor materials (beta silicon carbide powder and boron and carbon sintering aids), develop mixing and injection molding procedures for fabricating test bars, and characterize the properties of the sintered materials. Parallel studies of various mixing, dewaxing, and sintering procedures have been carried out in order to distinguish process routes for improving material properties. A total of 276 MOR bars of the baseline material have been molded, and 122 bars have been fully processed to a sinter density of approximately 95 percent. The material has a mean MOR room temperature strength of 43.31 ksi (299 MPa), a Weibull characteristic strength of 45.8 ksi (315 MPa), and a Weibull modulus of 8.0. Mean values of the MOR strengths at 1000, 1200, and 14000 C are 41.4, 43.2, and 47.2 ksi, respectively. Strength controlling flaws in this material were found to consist of regions of high porosity and were attributed to agglomerates originating in the initial mixing procedures. The mean stress rupture lift at 1400 C of five samples tested at 172 MPa (25 ksi) stress was 62 hours and at 207 MPa (30 ksi) stress was 14 hours. New fluid mixing techniques have been developed which significantly reduce flaw size and improve the strength of the material. Initial MOR tests indicate the strength of the fluid-mixed material exceeds the baseline property by more than 33 percent.

Portable and Reliable Surface-Enhanced Raman Scattering Silicon Chip for Signal-On Detection of Trace Trinitrotoluene Explosive in Real Systems.

PubMed

Chen, Na; Ding, Pan; Shi, Yu; Jin, Tengyu; Su, Yuanyuan; Wang, Houyu; He, Yao

2017-05-02

There is an increasing interest in the development of surface-enhanced Raman scattering (SERS) sensors for rapid and accurate on-site detection of hidden explosives. However, portable SERS methods for trace explosive detection in real systems remain scarce, mainly due to their relatively poor reliability and portability. Herein, we present the first demonstration of a portable silicon-based SERS analytical platform for signal-on detection of trace trinitrotoluene (TNT) explosives, which is made of silver nanoparticle (AgNP)-decorated silicon wafer chip (0.5 cm × 0.5 cm). In principle, under 514 nm excitation, the Raman signals of p-aminobenzenethiol (PABT) modified on the AgNP surface could be largely lit up due to the formation of electronic resonance-active TNT-PABT complex. In addition, the surface of AgNPs and silicon substrate-induced plasmon resonances also contribute the total SERS enhancement. For quantitative evaluation, the as-prepared chip features ultrahigh sensitivity [limit of detection is down to ∼1 pM (∼45.4 fg/cm 2 )] and adaptable reproducibility (relative standard deviation is less than 15%) in the detection of TNT standard solutions. More importantly, the developed chip can couple well with a hand-held Raman spectroscopic device using 785 nm excitation, suitable for qualitative analysis of trace TNT even at ∼10 -8 M level from environmental samples including lake water, soil, envelope, and liquor with a short data acquisition time (∼1 min). Furthermore, TNT vapors diffusing from TNT residues (∼10 -6 M) can be detected by using such a portable device, indicating its feasibility in determination of hidden samples.

Integration of carbon nanotubes in slot waveguides (Conference Presentation)

NASA Astrophysics Data System (ADS)

Durán-Valdeiglesias, Elena; Zhang, Weiwei; Hoang, Thi Hong Cam; Alonso-Ramos, Carlos; Serna, Samuel; Le Roux, Xavier; Cassan, Eric; Balestrieri, Matteo; Keita, Al-Saleh; Sarti, Francesco; Biccari, Francesco; Torrini, Ughetta; Vinattieri, Anna; Yang, Hongliu; Bezugly, Viktor; Cuniberti, Gianaurelio; Filoramo, Arianna; Gurioli, Massimo; Vivien, Laurent

2016-05-01

Demanding applications such as video streaming, social networking, or web search relay on a large network of data centres, interconnected through optical links. The ever-growing data rates and power consumption inside these data centres are pushing copper links close to their fundamental limits. Optical interconnects are being extensively studied with the purpose of solving these limitations. Among the different possible technology platforms, silicon photonics, due to its compatibility with the CMOS platform, has become one of the preferred solutions for the development of the future generation photonic interconnects. However, the on-chip integration of all photonic and optoelectronic building blocks (sources, modulators and detectors…) is very complex and is not cost-effective due to the various materials involved (Ge for detection, doped Si for modulators and III-V for lasing). Carbon nanotubes (CNTs) are nanomaterials of great interest in photonics thanks to their fundamental optical properties, including near-IR room-temperature foto- and electro- luminescence, Stark effect, Kerr effect and absorption. In consequence, CNTs have the ability to emit, modulate and detect light in the telecommunications wavelength range. Furthermore, they are being extensively developed for new nano-electronics applications. In this work, we propose to use CNTs as active material integrated into silicon photonics for the development of all optoelectronic devices. Here, we report on the development of new integration schemes to couple the light emission from CNTs into optical resonators implemented on the silicon-on-insulator and silicon-nitride-on-insulator platforms. A theoretical and experimental analysis of the light interaction of CNTs with micro-ring resonators based on strip and slot waveguides and slot photonic crystal heterostructure cavities were carried out.

Ultrafast carrier thermalization and trapping in silicon-germanium alloy probed by extreme ultraviolet transient absorption spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zürch, Michael; Chang, Hung-Tzu; Kraus, Peter M.

Semiconductor alloys containing silicon and germanium are of growing importance for compact and highly efficient photonic devices due to their favorable properties for direct integration into silicon platforms and wide tunability of optical parameters. Here, we report the simultaneous direct and energy-resolved probing of ultrafast electron and hole dynamics in a silicon-germanium alloy with the stoichiometry Si 0.25Ge 0.75 by extreme ultraviolet transient absorption spectroscopy. Probing the photoinduced dynamics of charge carriers at the germanium M 4,5-edge (~30 eV) allows the germanium atoms to be used as reporter atoms for carrier dynamics in the alloy. The photoexcitation of electrons acrossmore » the direct and indirect band gap into conduction band (CB) valleys and their subsequent hot carrier relaxation are observed and compared to pure germanium, where the Ge direct (ΔE gap,Ge,direct = 0.8 eV) and Si 0.25Ge 0.75 indirect gaps (ΔE gap,Si0.25Ge0.75,indirect = 0.95 eV) are comparable in energy. In the alloy, comparable carrier lifetimes are observed for the X, L, and Γ valleys in the conduction band. A midgap feature associated with electrons accumulating in trap states near the CB edge following intraband thermalization is observed in the Si 0.25Ge 0.75 alloy. The successful implementation of the reporter atom concept for capturing the dynamics of the electronic bands by site-specific probing in solids opens a route to study carrier dynamics in more complex materials with femtosecond and sub-femtosecond temporal resolution.« less

Fluidized bed silicon deposition from silane

NASA Technical Reports Server (NTRS)

Hsu, George C. (Inventor); Levin, Harry (Inventor); Hogle, Richard A. (Inventor); Praturi, Ananda (Inventor); Lutwack, Ralph (Inventor)

1982-01-01

A process and apparatus for thermally decomposing silicon containing gas for deposition on fluidized nucleating silicon seed particles is disclosed. Silicon seed particles are produced in a secondary fluidized reactor by thermal decomposition of a silicon containing gas. The thermally produced silicon seed particles are then introduced into a primary fluidized bed reactor to form a fluidized bed. Silicon containing gas is introduced into the primary reactor where it is thermally decomposed and deposited on the fluidized silicon seed particles. Silicon seed particles having the desired amount of thermally decomposed silicon product thereon are removed from the primary fluidized reactor as ultra pure silicon product. An apparatus for carrying out this process is also disclosed.

Fluidized bed silicon deposition from silane

NASA Technical Reports Server (NTRS)

Hsu, George (Inventor); Levin, Harry (Inventor); Hogle, Richard A. (Inventor); Praturi, Ananda (Inventor); Lutwack, Ralph (Inventor)

1984-01-01

A process and apparatus for thermally decomposing silicon containing gas for deposition on fluidized nucleating silicon seed particles is disclosed. Silicon seed particles are produced in a secondary fluidized reactor by thermal decomposition of a silicon containing gas. The thermally produced silicon seed particles are then introduced into a primary fluidized bed reactor to form a fludized bed. Silicon containing gas is introduced into the primary reactor where it is thermally decomposed and deposited on the fluidized silicon seed particles. Silicon seed particles having the desired amount of thermally decomposed silicon product thereon are removed from the primary fluidized reactor as ultra pure silicon product. An apparatus for carrying out this process is also disclosed.

Method of making silicon carbide-silicon composite having improved oxidation resistance

NASA Technical Reports Server (NTRS)

Wang, Hongyu (Inventor); Luthra, Krishan Lal (Inventor)

2002-01-01

A Silicon carbide-silicon matrix composite having improved oxidation resistance at high temperatures in dry or water-containing environments is provided. A method is given for sealing matrix cracks in situ in melt infiltrated silicon carbide-silicon matrix composites. The composite cracks are sealed by the addition of various additives, such as boron compounds, into the melt infiltrated silicon carbide-silicon matrix.

Silicon carbide-silicon composite having improved oxidation resistance and method of making

NASA Technical Reports Server (NTRS)

Wang, Hongyu (Inventor); Luthra, Krishan Lal (Inventor)

1999-01-01

A Silicon carbide-silicon matrix composite having improved oxidation resistance at high temperatures in dry or water-containing environments is provided. A method is given for sealing matrix cracks in situ in melt infiltrated silicon carbide-silicon matrix composites. The composite cracks are sealed by the addition of various additives, such as boron compounds, into the melt infiltrated silicon carbide-silicon matrix.

Silicon isotope fractionation in rice and cucumber plants over a life cycle: Laboratory studies at different external silicon concentrations

NASA Astrophysics Data System (ADS)

Sun, Yan; Wu, Lianghuan; Li, Xiaoyan; Sun, Li; Gao, Jianfei; Ding, Tiping

2016-11-01

Understanding the variations of silicon isotopes in terrestrial higher plants can be helpful toward elucidating the global biogeochemical silicon cycle. We studied silicon isotope fractionation in rice and cucumber plants over their entire life cycles. These two different silicon-absorbing plants were grown hydroponically at different external silicon concentrations. The ranges of δ30Si values in rice were -1.89‰ to 1.69‰, -1.81‰ to 1.96‰, and -2.08‰ to 2.02‰ at 0.17 mM, 1.70 mM, and 8.50 mM silicon concentrations, respectively. The ranges of δ30Si values in cucumber were -1.38‰ to 1.21‰, -1.33‰ to 1.26‰, and -1.62‰ to 1.40‰ at 0.085 mM, 0.17 mM, and 1.70 mM external silicon concentrations, respectively. A general increasing trend in δ30Si values from lower to upper plant parts reflected the preferential incorporation of lighter silicon isotopes from transpired water to biogenic opal. Furthermore, the active uptake mechanism regulated by several transporters might have also played an important role in the preferential transport of heavy silicon isotopes into aboveground plant parts. This suggested that silicon isotope fractionation in both rice and cucumber was a Rayleigh-like process. The data on δ30Si values for the whole plants and nutrient solutions indicated that biologically mediated silicon isotope fractionation occurred during silicon uptake by roots. At lower external silicon concentrations, heavy silicon isotopes entered plants more readily than light silicon isotopes. Conversely, at higher external silicon concentrations, light silicon isotopes entered plants more readily than heavy silicon isotopes.

Production of electronic grade lunar silicon by disproportionation of silicon difluoride

NASA Technical Reports Server (NTRS)

Agosto, William N.

1993-01-01

Waldron has proposed to extract lunar silicon by sodium reduction of sodium fluorosilicate derived from reacting sodium fluoride with lunar silicon tetrafluoride. Silicon tetrafluoride is obtained by the action of hydrofluoric acid on lunar silicates. While these reactions are well understood, the resulting lunar silicon is not likely to meet electronic specifications of 5 nines purity. Dale and Margrave have shown that silicon difluoride can be obtained by the action of silicon tetrafluoride on elemental silicon at elevated temperatures (1100-1200 C) and low pressures (1-2 torr). The resulting silicon difluoride will then spontaneously disproportionate into hyperpure silicon and silicon tetrafluoride in vacuum at approximately 400 C. On its own merits, silicon difluoride polymerizes into a tough waxy solid in the temperature range from liquid nitrogen to about 100 C. It is the silicon analog of teflon. Silicon difluoride ignites in moist air but is stable under lunar surface conditions and may prove to be a valuable industrial material that is largely lunar derived for lunar surface applications. The most effective driver for lunar industrialization may be the prospects for industrial space solar power systems in orbit or on the moon that are built with lunar materials. Such systems would require large quantities of electronic grade silicon or compound semiconductors for photovoltaics and electronic controls. Since silicon is the most abundant semimetal in the silicate portion of any solar system rock (approximately 20 wt percent), lunar silicon production is bound to be an important process in such a solar power project. The lunar silicon extraction process is discussed.

Theoretical considerations for Reaction-Formed Silicon Carbide (RFSC) formation by molten silicon infiltration into slurry-derived preforms

NASA Technical Reports Server (NTRS)

Behrendt, D. R.; Singh, M.

1993-01-01

For reaction-formed silicon carbide (RFSC) ceramics produced by silicon melt infiltration of porous carbon preforms, equations are developed to relate the amount of residual silicon to the initial carbon density. Also, for a slurry derived preform containing both carbon and silicon powder, equations are derived which relate the amount of residual silicon in the RFSC to the relative density of the carbon in the preform and to the amount of silicon powder added to the slurry. For a porous carbon preform that does not have enough porosity to prevent choking-off of the silicon infiltration, these results show that complete silicon infiltration can occur by adding silicon powder to the slurry mixture used to produce these preforms.

Tribological properties of sintered polycrystalline and single crystal silicon carbide

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.; Srinivasan, M.

1982-01-01

Tribological studies and X-ray photoelectron spectroscopy analyses were conducted with sintered polycrystalline and single crystal silicon carbide surfaces in sliding contact with iron at various temperatures to 1500 C in a vacuum of 30 nPa. The results indicate that there is a significant temperature influence on both the friction properties and the surface chemistry of silicon carbide. The main contaminants on the as received sintered polycrystalline silicon carbide surfaces are adsorbed carbon, oxygen, graphite, and silicon dioxide. The surface revealed a low coefficient of friction. This is due to the presence of the graphite on the surface. At temperatures of 400 to 600 C graphite and copious amount of silicon dioxide were observed on the polycrystalline silicon carbide surface in addition to silicon carbide. At 800 C, the amount of the silicon dioxide decreased rapidly and the silicon carbide type silicon and carbon peaks were at a maximum intensity in the XPS spectra. The coefficients of friction were high in the temperature range 400 to 800 C. Small amounts of carbon and oxygen contaminants were observed on the as received single crystal silicon carbide surface below 250 C. Silicon carbide type silicon and carbon peaks were seen on the silicon carbide in addition to very small amount of graphite and silicon dioxide at temperatures of 450 to 800 C.

Silicon-doped boron nitride coated fibers in silicon melt infiltrated composites

DOEpatents

Corman, Gregory Scot; Luthra, Krishan Lal

2002-01-01

A fiber-reinforced silicon-silicon carbide matrix composite having improved oxidation resistance at high temperatures in dry or water-containing environments is produced. The invention also provides a method for protecting the reinforcing fibers in the silicon-silicon carbide matrix composites by coating the fibers with a silicon-doped boron nitride coating.

Silicon-doped boron nitride coated fibers in silicon melt infiltrated composites

DOEpatents

Corman, Gregory Scot; Luthra, Krishan Lal

1999-01-01

A fiber-reinforced silicon--silicon carbide matrix composite having improved oxidation resistance at high temperatures in dry or water-containing environments is produced. The invention also provides a method for protecting the reinforcing fibers in the silicon--silicon carbide matrix composites by coating the fibers with a silicon-doped boron nitride coating.

Vertical integration of high-Q silicon nitride microresonators into silicon-on-insulator platform.

PubMed

Li, Qing; Eftekhar, Ali A; Sodagar, Majid; Xia, Zhixuan; Atabaki, Amir H; Adibi, Ali

2013-07-29

We demonstrate a vertical integration of high-Q silicon nitride microresonators into the silicon-on-insulator platform for applications at the telecommunication wavelengths. Low-loss silicon nitride films with a thickness of 400 nm are successfully grown, enabling compact silicon nitride microresonators with ultra-high intrinsic Qs (~ 6 × 10(6) for 60 μm radius and ~ 2 × 10(7) for 240 μm radius). The coupling between the silicon nitride microresonator and the underneath silicon waveguide is based on evanescent coupling with silicon dioxide as buffer. Selective coupling to a desired radial mode of the silicon nitride microresonator is also achievable using a pulley coupling scheme. In this work, a 60-μm-radius silicon nitride microresonator has been successfully integrated into the silicon-on-insulator platform, showing a single-mode operation with an intrinsic Q of 2 × 10(6).

Wide-Band Monolithic Acoustoelectric Memory Correlators.

DTIC Science & Technology

1982-11-01

piezoelectric and non- earlier analysis of thin- oxide varactors . The new analysis ex- conducting. Tapped structures which satisfy this criterion are plains...for tapped LiNbO3/metal- oxide - important realization. The logical consequence is that only silicon [26] structures is, in fact, not applicable here. It...Clarke, "The GaAs SAW depletion layer of’ the diode array. A more complex structure, diode storage correlalor," in 1980 Ultrasonics Synp. Proc., pp a GaAs

Workshop on Cometary Dust in Astrophysics

NASA Technical Reports Server (NTRS)

2003-01-01

The paper include contribution of each Lunar and Planetary Institute. Contents include the following: Mass flux in the ancient Earth-Moon system and benign implications for the origin of life on Earth. In-situ analysis of complex organic matter in cometary dust by ion microprobe. Pristine presolar silicon carbide. Infrared spectra of melilite solid solution. Comet observations with SIRTF. Ice and carbon chemistry in comets. The nature in interstellar dust. Modeling the infrared emission from protoplanetary dust disks.

Target Track and Stabilization for Manportable Direct Fire Missiles.

DTIC Science & Technology

1981-11-01

appeared to achieve resonable results, since there is always the possibility that summing weighted scores can be misleading, as was the case with the 1-3...coelostat and variable prism compensation approaches (Appendix, Reference 6) but both suffered from even greater size and complexity problems than approach...8 mm Thick 2 an. Al., Glass, etc. ( ( )Rotating Prisms (Rilley) -30 mm diam x 6 mm Thick 2 ea Germanium. Silicon. Zu On Searn motion ± max requires

Reconstruction of facial deformities with alloplastic material.

PubMed

Schultz, R C

1981-12-01

The two most ideal and versatile foreign materials for reconstruction of facial bone deformities are silicone rubber and methyl methacrylate. Their biomechanical characteristics are uniquely suited to facial implantation for reconstruction of complex, irregular bony defects. The advantages and disadvantages of each are discussed, along with specific indications for their use. Surgical approaches and various methods of fabrication and fixation are presented and illustrated. The hazards and potential disappointments in the use of these and other alloplastic implants are reviewed.

Crystal structure refinement of reedmergnerite, the boron analog of albite

USGS Publications Warehouse

Clark, J.R.; Appleman, D.E.

1960-01-01

Ordering of boron in a feldspar crystallographic site T1(0) has been found in reedmergnerite, which has silicon-oxygen and sodium-oxygen distances comparable to those in isostructural low albite. If a simple ionic model is assumed, calculated bond strengths yield a considerable charge imbalance in reedmergnerite, an indication of the inadequacy of the model with respect to these complex structures and of the speculative nature of conclusions based on such a model.

In vitro investigation of intestinal transport mechanism of silicon, supplied as orthosilicic acid-vanillin complex.

PubMed

Sergent, Thérèse; Croizet, Karine; Schneider, Yves-Jacques

2017-02-01

Silicon (Si) is one of the most abundant trace elements in the body. Although pharmacokinetics data described its absorption from the diet and its body excretion, the mechanisms involved in the uptake and transport of Si across the gut wall have not been established. Caco-2 cells were used as a well-accepted in vitro model of the human intestinal epithelium to investigate the transport, across the intestinal barrier in both the absorption and excretion directions, of Si supplied as orthosilicic acid stabilized by vanillin complex (OSA-VC). The transport of this species was found proportional to the initial concentration and to the duration of incubation, with absorption and excretion mean rates similar to those of Lucifer yellow, a marker of paracellular diffusion, and increasing in the presence of EGTA, a chelator of divalents cations including calcium. A cellular accumulation of Si, polarized from the apical side of cells, was furthermore detected. These results provide evidence that Si, ingested as a food supplement containing OSA-VC, crosses the intestinal mucosa by passive diffusion via the paracellular pathway through the intercellular tight junctions and accumulates intracellularly, probably by an uptake mechanism of facilitated diffusion. This study can help to further understand the kinetic of absorption of Si. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Drosophila as an unconventional substrate for microfabrication

NASA Astrophysics Data System (ADS)

Shum, Angela J.; Parviz, Babak A.

2007-02-01

We present the application of Drosophila fruit flies as an unconventional substrate for microfabrication. Drosophila by itself represents a complex system capable of many functions not attainable with current microfabrication technology. By using Drosophila as a substrate, we are able to capitalize on these natural functions while incorporating additional functionality into a superior hybrid system. In the following, development of microfabrication processes for Drosophila substrates is discussed. In particular, results of a study on Drosophila tolerance to vacuum pressure during multiple stages of development are given. A remarkable finding that adult Drosophila may withstand up to 3 hours of exposure to vacuum with measurable survival is noted. This finding opens a number of new opportunities for performing fabrication processes, similar to the ones performed on a silicon wafer, on a fruit fly as a live substrate. As a model microfabrication process, it is shown how a collection of Drosophila can be made to self-assemble into an array of microfabricated recesses on a silicon wafer and how a shadow mask can be used to thermally evaporate 100 nm of indium on flies. The procedure resulted in the production of a number of live flies with a pre-designed metal micropattern on their wings. This demonstration of vacuum microfabrication on a live organism provides the first step towards the development of a hybrid biological/solid-state manufacturing process for complex microsystems.

Adsorption of bovine serum albumin on silicon dioxide nanoparticles: Impact of pH on nanoparticle-protein interactions.

PubMed

Givens, Brittany E; Diklich, Nina D; Fiegel, Jennifer; Grassian, Vicki H

2017-05-03

Bovine serum albumin (BSA) adsorbed on amorphous silicon dioxide (SiO 2 ) nanoparticles was studied as a function of pH across the range of 2 to 8. Aggregation, surface charge, surface coverage, and protein structure were investigated over this entire pH range. SiO 2 nanoparticle aggregation is found to depend upon pH and differs in the presence of adsorbed BSA. For SiO 2 nanoparticles truncated with hydroxyl groups, the largest aggregates were observed at pH 3, close to the isoelectric point of SiO 2 nanoparticles, whereas for SiO 2 nanoparticles with adsorbed BSA, the aggregate size was the greatest at pH 3.7, close to the isoelectric point of the BSA-SiO 2 complex. Surface coverage of BSA was also the greatest at the isoelectric point of the BSA-SiO 2 complex with a value of ca. 3 ±   1 × 10 11 molecules cm -2 . Furthermore, the secondary protein structure was modified when compared to the solution phase at all pH values, but the most significant differences were seen at pH 7.4 and below. It is concluded that protein-nanoparticle interactions vary with solution pH, which may have implications for nanoparticles in different biological fluids (e.g., blood, stomach, and lungs).

Effect of nanodimensional polyethylenimine layer on surface potential barriers of hybrid structures based on silicon single crystal

NASA Astrophysics Data System (ADS)

Malyar, Ivan V.; Gorin, Dmitry A.; Stetsyura, Svetlana V.

2013-01-01

In this report we present the analysis of I-V curves for MIS-structures like silicon substrate / nanodimensional polyelectrolyte layer / metal probe (contact) which is promising for biosensors, microfluidic chips, different devices of molecular electronics, such as OLEDs, solar cells, where polyelectrolyte layers can be used to modify semiconductor surface. The research is directed to investigate the contact phenomena which influence the resulting signal of devices mentioned above. The comparison of I-V characteristics of such structures measured by scanning tunnel microscopy (contactless technique) and using contact areas deposited by thermal evaporation onto the organic layer (the contact one) was carried out. The photoassisted I-V measurements and complex analysis based on Simmons and Schottky models allow one to extract the potential barriers and to observe the changes of charge transport in MIS-structures under illumination and after polyelectrolyte adsorption. The direct correlation between the thickness of the deposited polyelectrolyte layer and both equilibrium tunnel barrier and Schottky barrier height was observed for hybrid structures with polyethylenimine. The possibility of control over the I-V curves of hybrid structure and the height of the potential barriers (for different charge transports) by illumination was confirmed. Based on experimental data and complex analysis the band diagrams were plotted which illustrate the changes of potential barriers for MIS-structures due to the polyelectrolyte adsorption and under the illumination.

Growth of silicon nanoclusters in thermal silicon dioxide under annealing in an atmosphere of nitrogen

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ivanova, E. V., E-mail: Ivanova@mail.ioffe.ru; Sitnikova, A. A.; Aleksandrov, O. V.

2016-06-15

It is found for the first time that silicon nanoclusters are formed in the surface layer of thermal silicon dioxide under high-temperature annealing (T = 1150°C) in dried nitrogen. Analysis of the cathodoluminescence spectra shows that an imperfect surface layer appears upon such annealing of silicon dioxide, with silicon nanoclusters formed in this layer upon prolonged annealing. Transmission electron microscopy demonstrated that the silicon clusters are 3–5.5 nm in size and lie at a depth of about 10 nm from the surface. Silicon from the thermal film of silicon dioxide serves as the material from which the silicon nanoclusters aremore » formed. This method of silicon-nanocluster formation is suggested for the first time.« less

Brownian dynamics of a protein-polymer chain complex in a solid-state nanopore

NASA Astrophysics Data System (ADS)

Wells, Craig C.; Melnikov, Dmitriy V.; Gracheva, Maria E.

2017-08-01

We study the movement of a polymer attached to a large protein inside a nanopore in a thin silicon dioxide membrane submerged in an electrolyte solution. We use Brownian dynamics to describe the motion of a negatively charged polymer chain of varying lengths attached to a neutral protein modeled as a spherical bead with a radius larger than that of the nanopore, allowing the chain to thread the nanopore but preventing it from translocating. The motion of the protein-polymer complex within the pore is also compared to that of a freely translocating polymer. Our results show that the free polymer's standard deviations in the direction normal to the pore axis is greater than that of the protein-polymer complex. We find that restrictions imposed by the protein, bias, and neighboring chain segments aid in controlling the position of the chain in the pore. Understanding the behavior of the protein-polymer chain complex may lead to methods that improve molecule identification by increasing the resolution of ionic current measurements.

Brownian dynamics of a protein-polymer chain complex in a solid-state nanopore.

PubMed

Wells, Craig C; Melnikov, Dmitriy V; Gracheva, Maria E

2017-08-07

We study the movement of a polymer attached to a large protein inside a nanopore in a thin silicon dioxide membrane submerged in an electrolyte solution. We use Brownian dynamics to describe the motion of a negatively charged polymer chain of varying lengths attached to a neutral protein modeled as a spherical bead with a radius larger than that of the nanopore, allowing the chain to thread the nanopore but preventing it from translocating. The motion of the protein-polymer complex within the pore is also compared to that of a freely translocating polymer. Our results show that the free polymer's standard deviations in the direction normal to the pore axis is greater than that of the protein-polymer complex. We find that restrictions imposed by the protein, bias, and neighboring chain segments aid in controlling the position of the chain in the pore. Understanding the behavior of the protein-polymer chain complex may lead to methods that improve molecule identification by increasing the resolution of ionic current measurements.

Silicon-on-Insulator Pin Diodes.

DTIC Science & Technology

1987-12-01

Thin (0.5 Micron) Silicon-on-Oxidized Silicon Fig. 2.8 SEM Photographs of CVD Silicon Dioxide on Aluminum 28 After 1500 0 C Anneal in Oxygen...silicon nitride over the silicon dioxide encapsu- -9- lation layer and by depositing the silicon dioxide with a plasma CVD process which uses N20 as...relief via thermal expansion matching varies lin- -27- A B Figure 2.8: SEM Photographs of CVD Silicon Dioxide on Aluminum after 15000 C Anneal in Oxygen

Silicon nitride/silicon carbide composite powders

DOEpatents

Dunmead, Stephen D.; Weimer, Alan W.; Carroll, Daniel F.; Eisman, Glenn A.; Cochran, Gene A.; Susnitzky, David W.; Beaman, Donald R.; Nilsen, Kevin J.

1996-06-11

Prepare silicon nitride-silicon carbide composite powders by carbothermal reduction of crystalline silica powder, carbon powder and, optionally, crystalline silicon nitride powder. The crystalline silicon carbide portion of the composite powders has a mean number diameter less than about 700 nanometers and contains nitrogen. The composite powders may be used to prepare sintered ceramic bodies and self-reinforced silicon nitride ceramic bodies.

Converting a carbon preform object to a silicon carbide object

NASA Technical Reports Server (NTRS)

Levin, Harry (Inventor)

1990-01-01

A process for converting in depth a carbon or graphite preform object to a silicon carbide object, silicon carbide/silicon object, silicon carbide/carbon-core object, or a silicon carbide/silicon/carbon-core object, by contacting it with silicon liquid and vapor over various lengths of contact time in a reaction chamber. In the process, a stream comprised of a silicon-containing precursor material in gaseous phase below the decomposition temperature of said gas and a coreactant, carrier or diluent gas such as hydrogen is passed through a hole within a high emissivity, thin, insulating septum into the reaction chamber above the melting point of silicon. The thin septum has one face below the decomposition temperature of the gas and an opposite face exposed to the reaction chamber. Thus, the precursor gas is decomposed directly to silicon in the reaction chamber. Any stream of decomposition gas and any unreacted precursor gas from the reaction chamber is removed. A carbon or graphite preform object placed in the reaction chamber is contacted with the silicon. The carbon or graphite preform object is recovered from the reactor chamber after it has been converted to a desired silicon carbide, silicon and carbon composition.

Mode-converting coupler for silicon-on-sapphire devices

NASA Astrophysics Data System (ADS)

Zlatanovic, S.; Offord, B. W.; Owen, M.; Shimabukuro, R.; Jacobs, E. W.

2015-02-01

Silicon-on-sapphire devices are attractive for the mid-infrared optical applications up to 5 microns due to the low loss of both silicon and sapphire in this wavelength band. Designing efficient couplers for silicon-on-sapphire devices presents a challenge due to a highly confined mode in silicon and large values of refractive index of both silicon and sapphire. Here, we present design, fabrication, and measurements of a mode-converting coupler for silicon-on-sapphire waveguides. We utilize a mode converter layout that consists of a large waveguide that is overlays a silicon inverse tapered waveguide. While this geometry was previously utilized for silicon-on-oxide devices, the novelty is in using materials that are compatible with the silicon-on-sapphire platform. In the current coupler the overlaying waveguide is made of silicon nitride. Silicon nitride is the material of choice because of the large index of refraction and low absorption from near-infrared to mid-infrared. The couplers were fabricated using a 0.25 micron silicon-on-sapphire process. The measured coupling loss from tapered lensed silica fibers to the silicon was 4.8dB/coupler. We will describe some challenges in fabrication process and discuss ways to overcome them.

Numerical modelling of transdermal delivery from matrix systems: parametric study and experimental validation with silicone matrices.

PubMed

Snorradóttir, Bergthóra S; Jónsdóttir, Fjóla; Sigurdsson, Sven Th; Másson, Már

2014-08-01

A model is presented for transdermal drug delivery from single-layered silicone matrix systems. The work is based on our previous results that, in particular, extend the well-known Higuchi model. Recently, we have introduced a numerical transient model describing matrix systems where the drug dissolution can be non-instantaneous. Furthermore, our model can describe complex interactions within a multi-layered matrix and the matrix to skin boundary. The power of the modelling approach presented here is further illustrated by allowing the possibility of a donor solution. The model is validated by a comparison with experimental data, as well as validating the parameter values against each other, using various configurations with donor solution, silicone matrix and skin. Our results show that the model is a good approximation to real multi-layered delivery systems. The model offers the ability of comparing drug release for ibuprofen and diclofenac, which cannot be analysed by the Higuchi model because the dissolution in the latter case turns out to be limited. The experiments and numerical model outlined in this study could also be adjusted to more general formulations, which enhances the utility of the numerical model as a design tool for the development of drug-loaded matrices for trans-membrane and transdermal delivery. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

Affordable, Robust Ceramic Joining Technology (ARCJoint) Developed

NASA Technical Reports Server (NTRS)

Steele, Gynelle C.

2001-01-01

Affordable, Robust Ceramic Joining Technology (ARCJoint) is a method for joining high temperature- resistant ceramic pieces together, establishing joints that are strong, and allowing joining to be done in the field. This new way of joining allows complex shapes to be formed by joining together geometrically simple shapes. The joining technology at NASA is one of the enabling technologies for the application of silicon-carbide-based ceramic and composite components in demanding and high-temperature applications. The technology is being developed and tested for high-temperature propulsion parts for aerospace use. Commercially, it can be used for joining ceramic pieces used for high temperature applications in the power-generating and chemical industries, as well as in the microelectronics industry. This innovation could yield big payoffs for not only the power-generating industry but also the Silicon Valley chipmakers. This technology, which was developed at the NASA Glenn Research Center by Dr. Mrityunjay Singh, is a two-step process involving first using a paste to join together ceramic pieces and bonding them by heating the joint to 110 to 120 C for between 10 and 20 min. This makes the joint strong enough to be handled for the final joining. Then, a silicon-based substance is applied to the joint and heated to 1400 C for 10 to 15 min. The resulting joint is as strong as the original ceramic material and can withstand the same high temperatures.

Label-free virus detection using silicon photonic microring resonators.

PubMed

McClellan, Melinda S; Domier, Leslie L; Bailey, Ryan C

2012-01-15

Viruses represent a continual threat to humans through a number of mechanisms, which include disease, bioterrorism, and destruction of both plant and animal food resources. Many contemporary techniques used for the detection of viruses and viral infections suffer from limitations such as the need for extensive sample preparation or the lengthy window between infection and measurable immune response, for serological methods. In order to develop a method that is fast, cost-effective, and features reduced sample preparation compared to many other virus detection methods, we report the application of silicon photonic microring resonators for the direct, label-free detection of intact viruses in both purified samples as well as in a complex, real-world analytical matrix. As a model system, we demonstrate the quantitative detection of Bean pod mottle virus, a pathogen of great agricultural importance, with a limit of detection of 10 ng/mL. By simply grinding a small amount of leaf sample in buffer with a mortar and pestle, infected leaves can be identified over a healthy control with a total analysis time of less than 45 min. Given the inherent scalability and multiplexing capability of the semiconductor-based technology, we feel that silicon photonic microring resonators are well-positioned as a promising analytical tool for a number of viral detection applications. Copyright © 2011 Elsevier B.V. All rights reserved.

Analysis of a dielectric EAP as smart component for a neonatal respiratory simulator.

PubMed

Tognarelli, S; Deri, L; Cecchi, F; Scaramuzzo, R; Cuttano, A; Laschi, C; Menciassi, A; Dario, P

2013-01-01

Nowadays, respiratory syndrome represents the most common neonatal pathology. Nevertheless, being respiratory assistance in newborns a great challenge for neonatologists and nurses, use of simulation-based training is quickly becoming a valid meaning of clinical education for an optimal therapy outcome. Commercially available simulators, are, however, not able to represent complex breathing patterns and to evaluate specific alterations. The purpose of this work has been to develop a smart, lightweight, compliant system with variable rigidity able to replicate the anatomical behavior of the neonatal lung, with the final aim to integrate such system into an innovative mechatronic simulator device. A smart material based-system has been proposed and validated: Dielectric Electro Active Polymers (DEAP), coupled to a purposely shaped silicone camera, has been investigated as active element for a compliance change simulator able to replicate both physiological and pathological lung properties. Two different tests have been performed by using a bi-components camera (silicone shape coupled to PolyPower film) both as an isolated system and connected to an infant ventilator. By means of a pressure sensor held on the silicon structure, pressure values have been collected and compared for active and passive PolyPower working configuration. The obtained results confirm a slight pressure decrease in active configuration, that is in agreement with the film stiffness reduction under activation and demonstrates the real potentiality of DEAP for active volume changing of the proposed system.

Electron-excited energy dispersive X-ray spectrometry at high speed and at high resolution: silicon drift detectors and microcalorimeters.

PubMed

Newbury, Dale E

2006-12-01

Two recent developments in X-ray spectrometer technology provide dramatic improvements in analytical capabilities that impact the frontiers of electron microscopy. Silicon drift detectors (SDD) use the same physics as silicon (lithium) energy dispersive spectrometers [Si(Li) EDS] but differ in design: only 10% of the thickness of the Si(Li) EDS with an anode area below 0.1 mm2 and a complex rear surface electrode pattern that creates a lateral internal charge collection field. The SDD equals or betters the Si(Li) EDS in most measures of performance. For output versus input count rate, the SDD exceeds the Si(Li) EDS by a factor of 5 to 10 for the same resolution. This high throughput can benefit analytical measurements that are count limited, such as X-ray mapping and trace measurements. The microcalorimeter EDS determines the X-ray energy by measuring the temperature rise in a metal absorber. Operating at 100 mK, the microcalorimeter EDS achieves resolution of 2-5 eV over a photon energy range of 200 eV to 10 keV in energy dispersive operation, eliminating most peak interference situations and providing high peak-to-background to detect low fluorescence yield peaks. Chemical bonding effects on low energy (< 2 keV) peak shapes can be measured.

Mechanistic Selection and Growth of Twinned Bicrystalline Primary Si in Near Eutectic Al-Si Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jung, Choonho

2006-01-01

Morphological evolution and selection of angular primary silicon is investigated in near-eutectic Al-Si alloys. Angular silicon arrays are grown directionally in a Bridgman furnace at velocities in the regime of 10 -3 m/sec and with a temperature gradient of 7.5 x 10 3 K/m. Under these conditions, the primary Si phase grows as an array of twinned bicrystalline dendrites, where the twinning gives rise to a characteristic 8-pointed star-shaped primary morphology. While this primary Si remains largely faceted at the growth front, a complex structure of coherent symmetric twin boundaries enables various adjustment mechanisms which operate to optimize the characteristicmore » spacings within the primary array. In the work presented here, this primary silicon growth morphology is examined in detail. In particular, this thesis describes the investigation of: (1) morphological selection of the twinned bicrystalline primary starshape morphology; (2) primary array behavior, including the lateral propagation of the starshape grains and the associated evolution of a strong <100> texture; (3) the detailed structure of the 8-pointed star-shaped primary morphology, including the twin boundary configuration within the central core; (4) the mechanisms of lateral propagation and spacing adjustment during array evolution; and (5) the thermosolutal conditions (i.e. operating state) at the primary growth front, including composition and phase fraction in the vicinity of the primary tip.« less

Effect of Silicone on the Collagen Fibrillogenesis and Stability

PubMed Central

Kadziński, Leszek; Prokopowicz, Magdalena; Jakóbkiewicz-Banecka, Joanna; Gabig-Cimińska, Magdalena; Łukasiak, Jerzy; Banecki, Bogdan

2015-01-01

Collagen, the most abundant protein in mammals, is able to form fibrils, which have central role in tissue repair, fibrosis, and tumor invasion. As a component of skin, tendons, and cartilages, this protein contacts with any implanted materials. An inherent problem associated with implanted prostheses is their propensity to be coated with host proteins shortly after implantation. Also, silicone implants undergoing relatively long periods of contact with blood can lead to formation of thrombi and emboli. In this paper, we demonstrate the existence of interactions between siloxanes and collagen. Low-molecular-weight cyclic siloxane (hexamethylcyclotrisiloxane—D3) and polydimethylsiloxanes (PDMS) forming linear chains, ranging in viscosity from 20 to 12,000 cSt, were analyzed. We show that D3 as well as short-chain PDMS interact with collagen, resulting in a decrease in fibrillogenesis. However, loss of collagen native structure does not occur because of these interactions. Rather, collagen seems to be sequestered in its native form in an interlayer formed by collagen–siloxane complexes. On the other hand, silicone molecules with longer chains (i.e., PDMS with viscosity of 1000 and 12,000 cSt, the highest viscosity analyzed here) demonstrate little interaction with this protein and do not seem to affect collagen activity. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 104:1275–1281, 2015 PMID:25589402

Investigating dye-sensitised solar cells

NASA Astrophysics Data System (ADS)

Tobin, Laura L.; O'Reilly, Thomas; Zerulla, Dominic; Sheridan, John T.

2010-05-01

At present there is considerable global concern in relation to environmental issues and future energy supplies, for instance climate change (global warming) and the rapid depletion of fossil fuel resources. This trepidation has initiated a more critical investigation into alternative and renewable sources of power such as geothermal, biomass, hydropower, wind and solar energy. The immense dependence on electrical power in today's society has prompted the manufacturing of devices such as photovoltaic (PV) cells to help alleviate and replace current electrical demands of the power grid. The most popular and commercially available PV cells are silicon solar cells which have to date the greatest efficiencies for PV cells. The drawback however is that the manufacturing of these cells is complex and costly due to the expense and difficulty of producing and processing pure silicon. One relatively inexpensive alternative to silicon PV cells that we are currently studying are dye-sensitised solar cells (DSSC or Grätzel Cells). DSSC are biomimetic solar cells which are based on the process of photosynthesis. The SFI Strategic Research Centre for Solar Energy Conversion is a research cluster based in Ireland formed with the express intention of bringing together industry and academia to produce renewable energy solutions. Our specific research area is in DSSC and their electrical properties. We are currently developing testing equipment for arrays of DSSC and developing optoelectronic models which todescribe the performance and behaviour of DSSCs.

Combined Subchronic Toxicity of Aluminum (III), Titanium (IV) and Silicon (IV) Oxide Nanoparticles and Its Alleviation with a Complex of Bioprotectors.

PubMed

Minigalieva, Ilzira A; Katsnelson, Boris A; Privalova, Larisa I; Sutunkova, Marina P; Gurvich, Vladimir B; Shur, Vladimir Y; Shishkina, Ekaterina V; Valamina, Irene E; Makeyev, Oleg H; Panov, Vladimir G; Varaksin, Anatoly N; Bushueva, Tatiana V; Sakhautdinova, Renata R; Klinova, Svetlana V; Solovyeva, Svetlana N; Meshtcheryakova, Ekaterina Y

2018-03-13

Stable suspensions of metal/metalloid oxide nanoparticles (MeO-NPs) obtained by laser ablation of 99.99% pure elemental aluminum, titanium or silicon under a layer of deionized water were used separately, or in three binary combinations, or in a ternary combination to induce subchronic intoxications in rats. To this end, the MeO-NPs were repeatedly injected intraperitoneally (i.p.) 18 times during 6 weeks before measuring a large number of functional, biochemical, morphological and cytological indices for the organism's status. In many respects, the Al₂O₃-NP was found to be the most toxic species alone and the most dangerous component of the combinations studied. Mathematical modeling with the help of the Response Surface Methodology showed that, as well as in the case of any other binary toxic combinations previously investigated by us, the organism's response to a simultaneous exposure to any two of the MeO-NP species under study was characterized by a complex interaction between all possible types of combined toxicity (additivity, subadditivity or superadditivity of unidirectional action and different variants of opposite effects) depending on which outcome this type was estimated for and on effect and dose levels. With any third MeO-NP species acting in the background, the type of combined toxicity displayed by the other two remained virtually the same or changed significantly, becoming either more or less unfavorable. Various harmful effects produced by the (Al₂O₃-NP + TiO₂-NP + SiO₂-NP)-combination, including its genotoxicity, were substantially attenuated by giving the rats per os during the entire exposure period a complex of innocuous bioactive substances expected to increase the organism's antitoxic resistance.