bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diffusion Mechanism for Self Assembly on Inhomogeneously Strained Surfaces
Authors: Larsson M.I. , Sabiryanov R.F. , Cho K. , Clemens B.M. 
Published: June 2019

AbstractGrowth of nanostructures with controlled shape, on inhomogeneously strained surfaces, is investigated by means of kinetic Monte Carlo (KMC) simulations. We propose a method to assemble self organized sub-lithographic nanostructures. The method is based on a strain-assisted mechanism for adatom surface diffusion and nucleation. For an inhomogeneous surface strain field there is normally a driving force toward the most tensile strained areas. It is shown by means of KMC simulations, that almost straight and continuous Ag nanowires can be produced on the Pt(111) surface if the growth is followed by high-temperature annealing. We suggest also how the method can be utilized as the first step of a process to reduce the circuit line width.
Controlling 2-Dimensional Growth of Silver Nanoplates
Authors: Chen Sihai , Carroll David L. 
Published: June 2019

AbstractAfter the successful synthesis of silver nanoplates with shapes of truncated triangle and disk applying a seed-mediated growth process using cetyltrimethylammonium bromide as a shape controller, we here further report the method for systematic control of the size of silver nanoplate in 2-dimensions. Two ways are found effective in size control: one is through the change of the silver seed amounts, which can produce the nanoplates with the size varying from 210 nm to 40 nm; another is through the mild aging of the as-prepared silver nanoplate solution at a proper temperature, which can fine-tune the shape of the nanoplates, such as from triangle to circle, or from plate to sphere. X-ray and electron diffraction analysis reveal that these nanoplates are single crystals and with their basal plane as (111) planes. The in-plane dipole plasmon band of these nanoplates can thus be manipulated within 900 nm to 400 nm, providing new possibilities for applications in the fields such as infrared absorption, nonlinear optical limiting, and Raman or biochemical diagnosis.
Production of Nanostructures Under Ultraturbulent Collision Reaction Conditions - Application to Catalysts, Superconductors, CMP Abrasives, Ceramics, and Other Nanoparticles
Authors: Gruverman Irwin J. , Thumm Jeffrey R. 
Published: June 2019

AbstractThe development, operation and applications of a novel continuous chemical reactor system are described. The system, known as a Multiple Stream Mixer/Reactor (or MMR), produces nanoparticles by direct precipitation from two or more reactant solution streams in an extreme energy density, ultraturbulent, collision reaction region. Sensors and a control system are employed to assure constant mixing conditions and desired stoichiometry in the reaction region. The interaction chamber is designed to allow macro-, meso- and micromixing during processing. This allows control of product purity, yield, size, size distribution, and phase purity. Typical nanoparticle diameters in the one to ten nanometer range are often achievable, with tight size distribution. The MMR can be scaled from development quantities to tons/hour for production applications.
Synthesis of CdO Nanoneedles for Photonic and Sensing Applications
Authors: Liu Xiaolei , Li Chao , Han Song , Zhou Chongwu 
Published: June 2019

AbstractSingle-crystalline needle-shaped CdO nanostructures were synthesized using a chemical vapor deposition method and characterized using a variety of techniques. Devices consisting of individual CdO nanoneedles were fabricated and high conductance as well as high carrier concentrations was observed. The temperature dependence of the conductance revealed thermal excitation as the dominating transport mechanism. Our devices exhibited good sensitivity to both infrared light and diluted NO2 gas, indicating potential applications as infrared photo-detectors and toxic gas sensors.
Controlled Growth and Electronic Properties of Gallium Nitride Nanowires
Authors: Han Song , Jin Wu , Tang Tao , Li Chao , Zhang Daihua , Liu Xiaolei , Zhou Chongwu 
Published: June 2019

AbstractHigh-quality single crystalline gallium nitride (GaN) nanowires are synthesized via a chemical vapor deposition (CVD) method using gold nanoparticles as the catalyst. This method enables control over several important aspects of the growth, including control of the nanowire diameter by using mono-dispersed gold clusters, control of the nanowire location via e-beam patterning of the catalyst sites, and control of the nanowire orientation via epitaxial growth on aplane sapphire substrates. Transport properties of these GaN nanowires are studied. Our work opens up new ways to use GaN nanowires as nano-building blocks.
The MrgA Multimeric Complex: a self-assembled nanostructure for inorganic synthesis
Authors: Kramer Ryan M. , Loganathan Amritraj G. , Naik Rajesh R. , Stone Morley 
Published: June 2019

AbstractUtilization of protein cages in biomimetic chemistry allows for the deposition of inorganic materials within an organic construct, controlling the size and amount of material deposited within a constrained reaction environment. Previously, protein cages such as viral capsids and ferritins have been used in the constrained synthesis of inorganic materials. The MrgA protein displays a high sequence homology to both bacterial DNA-protecting proteins (Dps) found in many bacterial genera and Ferritin-like proteins (Flp), which have been shown to functionally sequester and store iron in a biologically available form. Here we demonstrate recombinant production, purification and characterization of the MrgA protein and provide evidence that this protein self-assembles to form a multimeric complex. This complex demonstrates characteristics similar to that of ferritin-like proteins such as resistance to iron toxicity, iron incorporation, and resistance to thermal and chemical denaturation. The ability to deposit iron within the putative internal cavity of this protein cage will allow the MrgA complex to be utilized as a spatially constrained reaction vessel for nanomaterial synthesis of other inorganic materials. From a materials science perspective, it will be interesting to see if these organic/inorganic hybrid materials can be harnessed for catalysis, nanomagnetics, and other applications.
Luminescence and Microstructure of Microspheres Containing Silicon Nanocrystals
Authors: Ryan C.A. , Meldrum A. , White C.W. 
Published: June 2019

AbstractThe strong visible photoluminescence (PL) of silicon nanocrystals has recently been the focus of considerable research interest. Nanocrystal composites produced by silicon implantation of a fused silica wafer followed by high-temperature thermal processing are characterized by a strong, broad photoluminescence spectrum. This light emission, centered in the near infrared and extending well into the visible range, has potential applications for the development of photonic materials based on silicon nanostructures. Here, we report on our attempts to form luminescent silica microspheres containing embedded silicon nanocrystals. Arrays of luminescent microspheres were successfully fabricated, without significant coagulation or destruction of the silica spheres during the silicon ion implantation step. However, a substantial deformation on the surface of the spheres that occurred during the high-flux implantation prevented the development of resonant cavity modes in the luminescence spectra. Resonant modes could clearly be observed for pre-implanted and annealed SiO2wafers with a layer of pristine microspheres subsequently deposited on the implanted surface. These results suggest an alternative method for producing highly durable luminescent silica “microbeads”. At lower ion fluxes, the development of luminescent microsphere superlattices with novel optical properties due to coupling of the light emission from the silicon nanocrystals into the resonant cavity modes may be possible if the deformation effects can be reduced or eliminated.
Ion Implantation Synthesis and Characterization of Cobalt Nanodots
Authors: Jacobsohn L.G. , Hawley M.E. , Dickerson R.M. , Cooke D.W. , Nastasi M. 
Published: June 2019

AbstractA study of the synthesis of Co nanodots by ion implantation was carried out. Silica was implanted with 35 keV Co+ ion beams with doses of 8×1015, 3×1016 and 1×1017 at/cm2 and transmission electron microscopy revealed the presence of spherical nanodots in these samples. Annealing in vacuum at 900 oC was used to change the size distribution of the nanodots. The annealed samples presented an absorption band related to the plasmon collective excitation of the metallic nanodots that redshifted for higher Co contents. The magnetic character of the samples was revealed by magnetic force microscopy measurements that showed the presence of randomly distributed structures with defined magnetization in the case of annealed samples. This work shows the feasibility of synthesizing Co nanodots with controlled size distribution.
A Parametric Study of a Repository Tunnel for Decommissioning Waste
Authors: Pereira António C. , Sundström Benny , Broed Robert L. 
Published: June 2019

ABSTRACTThe development of a radionuclide transport model for a tunnel of a repository for short-lived low and intermediate level waste is presented in this work. The model is two-dimensional and uses the finite element method to describe a cross-section perpendicular to the tunnel's main axis. It is shown that the use of a realistic geometry of the system, albeit in 2D, results in a transparent model that can handle the equations in a flexible way. The geometry can easily be changed and also extended to a 3D representation without affecting the numerical code. The disadvantage is the computational requirement. It is expected however that radionuclide transport modelling will evolve to 2D or 3D representations that are more realistic and transparent than today's 1D analytical models which involve many simplifications whose impact on the output is difficult to evaluate.
Use of Computational Thermodynamics in Rapid Prototyping and Infiltrating Steel Parts
Authors: Kernan Brian D. , Sachs Emanuel M. , Allen Samuel 
Published: June 2019

ABSTRACTThe direct manufacture of metal parts by rapid prototyping often involves building a porous skeleton from a metal powder. In this work, a method termed Homogeneous Steel Infiltration has been developed for infiltrating steel skeletons to make conventional tool steel alloys. The method uses a gated infiltration route that uses as the infiltrant a steel alloy with a lower melting point than the base powder. The infiltrant liquid may use carbon and/or silicon as a melting point depressant. Premature freeze-off of the steel infiltrant is avoided by operating at a temperature where some liquid is stable at chemical equilibrium. The compositions of the skeleton and infiltrant and the infiltration temperature are selected by using computational thermodynamics. Examples of successful infiltrations using D2 and A3 tool steels as target compositions are shown. The thermodynamic design method enables suitable parameters to make other tool steels, some stainless steels and manganese steels.
N+/P and P+/N Junctions in Strained Si on Strain Relaxed SiGe Buffers: the Effect of Defect Density and Layer Structure
Authors: Eneman G. , Simoen E. , Delhougne R. , Verheyen P. , Ries M. , Loo R. , Caymax M. , Vandervorst W. , Meyer K. De 
Published: June 2019

AbstractThe electrical performance of junctions in SiGe Strain Relaxed Buffers (SRB's) with a strained Si top layer is investigated. Most of the SRB's grown in this experiment use a thin C-doped SiGe layer, which allows to fabricate thin (∼250nm) SRB's with a high relaxation degree. The effects of Threading Dislocation Density (TDD) and C-rich layer depth on the electrical behaviour of n+/p and p+/n junctions are studied. The C atoms in the junction's Space Charge Region (SCR) give rise to defects and induce a noticeable increase in the leakage. The effect of the TDD on the leakage in n+/p junctions is linear over the complete voltage range applied, while for p+/n junctions, only a small effect on leakage is measured at V=1V reverse for TDD's below 1×107cm-2. For low reverse voltages, the current varies more linearly with TDD.
Defect Characterization of CdTe Bulk Crystals Doped with Heavy Elements and Rare Earths
Authors: Neretina Svetlana , Sochinskii N.V. , Mascher Peter , Saucedo E. 
Published: June 2019

AbstractThe doping level in Cadmium Telluride (CdTe) is of the utmost importance for many applications. In this work, we have characterized CdTe crystals doped with Tl, Bi, or Yb as well as a crystal co-doped with Ge and Yb. The crystals were characterized using low-temperature Photoluminescence (PL), Positron Lifetime Spectroscopy (PLS), resistivity and a terahertz pump-probe technique that can determine carrier lifetimes. The properties of the crystals were also studied before and after a rapid thermal anneal (RTA) as well as after a longer conventional anneal. The results obtained using the various dopants vary widely. It will be shown, however, that the above mentioned dopants can form complexes with Cd vacancies (vacancy-impurity pairs). As a result, these Cd vacancies can play a key role in determining the resistivity and carrier lifetimes.
Device Parametric Shift Mechanism Caused by Boron Halo Redistribution Resulting from Dose Rate Dependence of SDE Implant
Authors: Jeong Ukyo , Liu Jinning , Guo Baonian , Shim Kyuha , Mehta Sandeep 
Published: June 2019

AbstractChange in dopant diffusion was observed for Arsenic source drain extension (SDE) implants when they were performed at various dose rates. The high dose SDE implant amorphizes the surface of the silicon substrate and the thickness of the amorphous layer is strongly influenced by the rate of dopant bombardment. It is well known that the ion implantation process introduces excess interstitials. While the amorphous region is completely re-grown into single crystal during subsequent anneal without leaving behind extended defects, interstitials that are injected beyond the amorphous layer lead to formation of {311} defects or dislocation loops in the end of range region. During thermal processing, these extended defects dissolve, release interstitials, which in turn lead to transient enhanced diffusion of underlying Boron halo dopant. Dopant depth profiles measured by SIMS revealed different amount of Boron pile-up in the near surface region, corresponding to different SDE implant dose rates. In CMOS devices, this surface pile-up would correlate with a Boron pile-up in the channel region that would lead to a shift in transistor characteristics. Through this investigation, we were able to explain the mechanism causing device characteristics shift resulted from SDE implant with the same dose and energy but different dose rates.
Direct Measurement of Ion Beam Induced, Nanoscale Roughening of GaN
Authors: Cui Bentao , Cohen P. I. , Dabiran A. M. 
Published: June 2019

AbatractThe formation of ion induced nanoscale patterns such as ripple, dots or pores can be described by a linear continuum equation consisting of a surface roughening term due to curvature-dependent sputtering or asymmetric attachment of vacancies, and a surface smoothing term due to thermal or ion-induced diffusion. By studying ion-induced dimple volume change using atomic force microscopy, we show a method to measure the ion-roughening coefficient. Using this method, we found the roughening coefficient í was 45 nm2/sec at 730K for initial ion etchings with 300 eV Argon ions. Cathodoluminescence measurements indicated Ga-vacancy formation during ion bombardment. The activation energy for surface relaxation after ion etching was about 0.12 eV as measured by reflection high energy electron diffraction.
Structural Characterization of GaN Epilayers Grown on Patterned Sapphire Substrates
Authors: Kim Chang-Soo , Moon Ji-Hyun , Lee Sang-Jun , Noh Sam-Kyu , Kim Je Won , Lee Kyuhan , Choi Yong Dae , Song Jay P. 
Published: June 2019

AbstractThe structural properties of GaN epitaxial layers grown on patterned sapphire substrates by MOCVD have been investigated using HRXRD(high-resolution X-ray diffraction), GIXRD(grazing incidence X-ray diffraction) and PL(photoluminescence). For X-ray characterizations rocking curves for GaN (10·5), (00·2), (11·4) and (11·0) reflections for which incidence angles of X-rays are 32.0°, 17.3°, 11.0° and 0.34°, respectively, were measured. For (10·5), (00·2) and (11·4) reflections FWHMs of the rocking curves for a patterned substrate were broader than those for a unpatterned substrate, for (11·0) reflection, however, FWHM for a patterned substrate was much narrower than that for a unpatterned substrate. The normalized FWHM for all reflections decreases as the incidence angle of X-ray decreases. The results indicate that the crystalline quality in the surface region of the epilayer on a patterned substrate was especially improved because the penetration depth of X-ray depends on the incidence angle. The intensity of PL peak of the epilayer for a patterned substrate increased compared to that for a unpatterned substrate, and the increase in PL intensity is attributed to the reduction in dislocation density at the surface region revealed the by X-ray results.
Effect of Ohmic Contacts on Polysilicon Memory Effect
Authors: Herner S.B. , Jahn C. , Kidwell D. 
Published: June 2019

AbstractPolysilicon memory switching is demonstrated in vertical n-i-p diodes with TiN contacts and feature size 150 nm. An increase of more than three orders of magnitude forward current at +2 V is achieved after the application of a +8 V programming pulse. The programming pulse electro thermally melts the polysilicon through Joule heating, and the quenched diodes have higher forward current. By changing one of the contacts from TiN to TiSi2, polysilicon memory switching is eliminated, with high forward current in the diode before and after a programming pulse. The TiSi2 contact seeds the crystallization of polysilicon with fewer defects during fabrication, compared to crystallization with TiN-only contacts, as shown by transmission electron microscopy. The mechanisms for increased forward current induced by either programming the TiN-only contacted diodes or making one contact TiSi2 are discussed.
Contact Free Defect Investigation in as grown Fe-doped SI-InP
Authors: Hahn Sabrina , Dornich Kay , Hahn Torsten , Gründig-Wendrock Bianca , Niklas Jürgen R. , Schwesig Peter , Müller Georg 
Published: June 2019

AbstractThe methods of microwave-detected photo-induced current transient spectroscopy (MD-PICTS) and microwave-detected photoconductivity (MDP), which proved themselves as very successful for defect investigations in GaAs wafers, were applied to Fe-doped SI-InP samples. It was possible to observe characteristic defect levels. One important defect center showed a similar behavior as the well known EL2 defect in GaAs. This defect exhibits positive and negative PICTS signals depending on the Fe concentration. The associated activation energies show that these signals can be interpreted as an interaction of the Fe2+/3+ level in InP with both, the valence and the conduction band.Beside this major defect we discovered a wide range of shallow defects which may be important for material properties.This result and successful microwave detected photoconductivity mappings of InP wafers show that the new non-destructive investigation methods provide valuable information on defect distribution and characteristics.
Thermal Growth of He-cavities in Si Studied by Cascade Implantation
Authors: Ntsoenzok E. , Bouayadi R. El , Regula G. , Pichaud B. , Ashok S. 
Published: June 2019

AbstractFloat Zone (FZ) silicon samples have been cascade-implanted with helium ions at energies decreasing from 1.9 MeV to 0.8 MeV in steps of 0.1 MeV, with flux maintained between 5 × 1012 and 1 × 1013 He cm-2-1s. The dose was 5×1016 He cm-2 for all the energies except 0.8 MeV where a lower dose of 3×1016 He cm-2 was used. After thermal annealing, the sample was studied by cross section transmission electron microscopy (XTEM) using a Field Emission Gun Microscope (Jeol 2010F). Our results clearly demonstrate that these cavities mainly grow by the Ostwald ripening mechanism. This means a growth by exchange of He and vacancies from smaller to bigger cavities. Further this study provides essential data for resolving the controversy on the growth mechanism governing He-cavities.
Multistep Resonant Excitation of Erbium Ions in Thin Silicon Oxide Layers
Authors: Fleischman Z. , Sandmann Chr. , Dierolf V. , White M. , Zhao Y. , Michel J. , Stolfi M.A. , Negro L. Dal 
Published: June 2019

AbstractUsing the site-selective technique of combined excitation emission spectroscopy, we have studied a variety of Er doped silicon oxide layers with and without silicon nanocrystals. This technique allows clear distinction of cluster defect sites that are created during thermal annealing and become dominant for higher Er ion concentration and are suppressed by the presence of nanocrystals. In several samples, we were able to observe fluorescence line narrowing under resonant excitation allowing defect-selective excitation.
The Adhesion of Pad Particles on Wafer Surfaces during Cu CMP
Authors: Song Jae-Hoon , Han Ja-Hyung , Hong Yi-Koan , Kang Young-Jae , Park Jin-Goo , Maeng Ju-Ho , Won Young-Man 
Published: June 2019

AbstractThe adhesion force of pad and alumina were experimentally and theoretically investigated in slurry solutions of different pHs. The isoelectric point (IEP) of pad particles was measured to be around pH 3. The wafer surfaces showed negative zeta potentials in the investigated pH ranges with exception of FSG and Ta. Cu and Ta showed higher interaction forces than dielectric materials. The lowest adhesion force was measured between pad particle and wafer surfaces in a slurry solution of pH 11. The magnitude of adhesion force of pad particles was lower than alumina particles.
Development of Multi-plume and Multi-turn (MPT) PLD for YBCO Coated Conductor
Authors: Watanabe Tomonori , Kuriki Reiji , Muroga Takemi , Miyata Seiki , Ibi Akira , Yamada Yutaka , Shiohara Yuh , Kato Takeharu , Hirayama Tsukasa 
Published: June 2019

AbstractOur multi-plume and multi-turn (MPT) pulsed-laser deposition (PLD) has been improved to accelerate reliable and fast deposition technique of high Ic (critical current) YBCO (YBa2Cu3O7-x) layer for a long coated conductor fabrication, for we increased the number of multi-turn, from three to four, in our multi-plume and multi-turn (MPT) PLD system. This increase of the number of depositing turns achieved high deposition rate corresponded to 75 mm3/h (=1 μm-thick × 10 mm-wide × 7.5 m/h, throughout all 4 turns) for YBCO layer. This four turn (4t)-MPT-PLD also indicated a capability to combine high deposition rate and high Ic. We attained the highest Ic's of 321 A at the tape speed of 3 m/h and 340 A at tape speed of 2 m/h by 4t-MPT-PLD in 10 mm-wide and 10 cm-long samples.Based on these results, we successfully deposited a 100 m long YBCO layer by 4t-MPT-PLD. This coated conductor had high Ic as high as 159 A, therefore, the multiplication of Ic and length exhibited high value of 15.9 kA·m.
Chemical synthesis of nanoparticles for artificial pinning centers in YBCO coated conductors
Authors: Sathyamurthy Srivatsan , Leonard Keith J. , Paranthaman M. Parans 
Published: June 2019

AbstractCeria nanoparticles were prepared using a solution based approach using cerium (III) acetate as a starting material and cetyltrimethylammonium hydroxide (CTAOH) as a precipitating agent and surfactant. The presence of the surfactant CTAOH helps prevent agglomeration of the nanoparticles. Using X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM), the particle size was determined to be 3.5 – 4 nm. The structure and properties of these CeO2 nanoparticles have been analyzed.