bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bottom up Nano-particle Formation via Controlled Crystallization and Chemical Reactions
Authors: Panagiotou Thomai , Fisher Robert J. 
Published: September 2011

ABSTRACTMany manufacturing techniques to produce nano-materials via a “bottom-up” approach are currently being developed and evaluated. The PureNanoTMplatform technology developed by Microfluidics International Corporation (MFIC) has proven to be both an effective and energy efficient method to produce nano-scale entities including emulsions in addition to suspensions. This nano-manufacturing platform utilizes crystallization, precipitation and chemical reaction methods that produce nano-particles with specified size distributions and a desired morphology. The solids formed can be either amorphous or crystalline, which may exist in numerous polymorphs. In many cases the ability to obtain a specific composition (single species or mixture) is possible via careful selection and implementation of key processing conditions. The methods are based on controlling the local degree of super-saturation (SS) and/or stoichiometry during their formation and subsequent configuration and growth, when appropriate. To accomplish this, operational strategies and innovative processing techniques are coupled with qualitative insight into the basic mechanisms involved with these processes. Validation of the technology at the bench scale for crystallization, emulsions/cargo loading, and multi-phase reactions (interfacial and homogeneous) provided the justification to develop commercial scale systems. Examples are given here for crystallization of drugs for the pharmaceutical industry, a catalyst formed by deposition of metallic crystals on a carbon substrate, production of fine chemicals via emulsion formation for multi-phase reactions, and a homogeneous substitution reaction forming an insoluble product. Nano-materials with median particle size as low as 50 nm were produced. With respect to the drug particles, they were highly crystalline, of a single polymorph and pure. In all cases, results indicate both process performance enhancement and product quality/functionality improvements compared to materials produced with conventional methods, with at least 1-2 order of magnitude increases in surface/interfacial area and reduced energy needs. Furthermore, the technology is suitable for current Good Manufacturing Practices (cGMP) manufacturing.
Reversible Tuning of the Electronic Properties of Graphene via Controlled Exposure to Electron Beam Irradiation and Annealing
Authors: Teweldebrhan Desalegne , Liu Guanxiong , Balandin Alexander A. 
Published: September 2011

ABSTRACTGraphene reveals many extraordinary properties including extremely high room temperature carrier mobility and intrinsic thermal conductivity. Understanding how to controllably modify graphene’s properties is essential for its proposed applications. Here we report on a method for tuning the electrical properties of graphene via electron beam irradiation. It was observed that single-layer graphene is highly susceptible to the low-energy electron beams. We demonstrated that by controlling the irradiation dose one can change, by desired amount, the carrier mobility, shift the charge neutrality point, increase the resistance at the minimum conduction point, induce the “transport gap” and achieve current saturation in graphene. The change in graphene properties is due to defect formation on the graphene surface and in the graphene lattice. The changes are reversible by annealing until some critical irradiation dose is reached.
Data Transmission Performance of Few-Layer Graphene Ribbons
Authors: Guvenc Ali Bilge , Lin Jian , Penchev Miroslav , Ozkan Cengiz , Ozkan Mihrimah 
Published: September 2011

ABSTRACTWe investigated the electrical characteristics and digital data transmission performance few-layer graphene ribbons grown by chemical vapor deposition. Graphene ribbons having a mobility of 2,180 cm2V-1s-1 can sustain data rates up to 50 megabits per second at 1.5 μm length, thus the bandwidth is inversely proportional to resistance caused by defects in the graphene layers. Improving the graphene mobility to highest measured values (∼200,000 cm2V-1s-1) and using structures with multiple coplanar transmission lines in parallel could carry the bandwidth beyond the gigabits per second level.
Expression and Self Assembly of Cowpea Chlorotic Mottle Virus Capsid Proteins inPichia pastorisand Encapsulation of Fluorescent Myoglobin
Authors: Wu Yuanzheng , Yang Hetong , Shin Hyun-Jae 
Published: September 2011

Abstract:Cowpea chlorotic mottle virus (CCMV) has been a model system for virus studies for over 40 years and now is considered to be a perfect candidate as nanoplatform for applications in materials science and medicine. The ability of CCMV to self assemblein vitrointo virus-like particles (VLPs) or capsids makes an ideal reaction vessel for nanomaterial synthesis and entrapment. Here we report expression of codon optimized CCMV coat protein inPichia pastorisand production of self assembled CCMV VLPs by large-scale fermentation. CCMV coat protein gene (573 bp) was synthesized according to codon preference ofP. pastorisand cloned into pPICZA vector. The recombinant plasmid pPICZA-CP was transformed intoP. pastorisGS115 by electroporation. The resulting yeast colonies were screened by PCR and analyzed for protein expression by SDS-PAGE. After large-scale fermentation CCMV coat protein yields reached 4.8 g L−1. The CCMV VLPs were purified by modified PEG precipitation followed by cesium chloride density gradient ultracentrifugation, and then analyzed by size exclusion fast performance liquid chromatography (FPLC), UV spectrometry and transmission electron microscopy. Myoglobin was used as a model protein to be encapsulated in CCMV VLPs. The fluorescence spectroscopy showed that inclusion of myoglobin had occurred. The results indicated the production of CCMV capsids byP. pastorisfermentation now available for utilization in pharmacology or nanotechnology fields.
Interplay Between the Crystal and Liquid Crystalline Ordering of iPP and Carbon Nanotube Composites under Melt-Shear
Authors: Georgiev Georgi , McIntyre Michael B. , Judith Robert , Gombos Erin A. , Cebe Peggy 
Published: September 2011

ABSTRACTCarbon nanotubes (CNTs) exhibit liquid crystalline order and their nematic director couples to the one of low molecular weight liquid crystals. Here we explore the interactions between CNTs and the smectic liquid crystal phase of a polymer and the possibility for a similar coupling in this system. Isotactic Polypropylene (iPP) and iPP/CNTs nanocomposites were made in solution with varying CNT concentrations and hot pressed into 50-100μm thick films. The pure iPP and iPP/CNT films were then sheared at one rotation per second in the melt state. Shearing continued as the temperature was decreased from 200°C to 145°C to induce a smectic liquid crystal phase. The sheared samples were analyzed using polarized optical microscopy, Two Dimensional Microscopic Transmission Ellipsometry (2D-MTE) and Two Dimensional Wide Angle X-Ray Scattering (2D-WAXS). During shearing we detected a sudden increase of birefringence at 151°C in the samples, higher than the iPP crystallization temperature, indicating liquid crystalline ordering. The samples were then crystallized at 135°C for 30 minutes. We measured anisotropic 2D-WAXS patterns of the samples that contained CNTs, indicating strong ordering of the crystals. Upon reheating, we measured birefringence at temperatures higher than the melting endotherm for the iPP crystals, using polarized microscopy, which indicates that some smectic order still persists in the samples, even after crystallization and complete melting of all crystals. Our results indicate that CNTs couple to the smectic phase of iPP, improve its order upon shearing and the crystals created after the formation of the oriented smectic phase are strongly aligned parallel to the direction of shearing.
Zeeman splittings of the 5D0–7F2 transitions of Eu3+ ions implanted into GaN
Authors: Kachkanov V. , O’Donnell K.P. , Rice C. , Wolverson D. , Martin R.W. , Lorenz K. , Alves E. , Bockowski M. 
Published: September 2011

ABSTRACTWe report the magnetic field splittings of emission lines assigned to the 5D0–7F2 transitions of Eu3+ centres in GaN. The application of a magnetic field in the c-axis direction (B‖c) leads to a splitting of the major lines at 621 nm, 622 nm and 622.8 nm into two components. The Zeeman splitting is linear with magnetic field up to 5 Tesla for each line. In contrast, a magnetic field applied in the growth plane (B┴c) does not influence the photoluminescence spectra. The estimated g-factors vary slightly from sample to sample with mean values of g‖ ~2.8, ~1.5 and ~2.0 for the emission lines at 621 nm, 622 nm and 622.8 nm respectively.
Experimental and Theoretical Study of the New Image Force Microscopy Principle (Invited Paper)
Authors: Wickramasinghe H. Kumar , Rajapaksa Indrajith 
Published: September 2011

ABSTRACTA new technique in microscopy is demonstrated in which the domain of Atomic Force Microscopy (AFM) is extended to optical spectroscopy at the nanometer scale. Molecular resonance of feature sizes down to the single molecular level were detected and imaged purely by mechanical detection of the force gradient between the interaction of the optically driven object molecular dipole and its mirror image in a Platinum coated scanning probe tip. We provide full experimental details including a basic theory for this new technique. The microscopy and spectroscopy technique is extendable to frequencies ranging from radio to infrared and the ultra violet.
Synthesis of Resorcinol Formaldehyde Aerogel Using UV Photo-Initiators for Inertial Confinement Fusion Experiments
Authors: Paguio R.R. , Saito K.M. , Hund J.F. , Jimenez R. M. 
Published: September 2011

ABSTRACTResorcinol formaldehyde (R/F) aerogels have been used in a variety of laser targets for Inertial Confinement Fusion (ICF) experiments in the form of thin films, cast shapes such as cylinders and cubes, and hollow and solid microspheres. Besides ICF experiments, R/F aerogel can be used for capacitors, batteries, thermal insulation, absorption/filtration media, and chromatographic packing applications. Traditionally, R/F aerogel is synthesized using a 2-step (base/acid catalysis) polycondensation reaction. We have developed a novel process to synthesize the R/F aerogel using free radical UV initiator at room temperature in 10 minutes using a UV light source. This paper will review this process, which was developed to synthesize R/F aerogels using UV-free radical initiators. Scanning electron microscopy results will also be discussed to show that the aerogel pore structure is similar to traditional R/F aerogels. Fabrication of solid and hollow microspheres for ICF experiments using this R/F aerogel synthesis technique and the technique’s limitations will also be discussed.
Enhanced Thermoelectric Properties of Strongly Degenerate Polycrystalline Silicon upon Second Phase Segregation
Authors: Narducci Dario , Selezneva Ekaterina , Arcari Andrea , Cerofolini Gianfranco , Romano Elisabetta , Tonini Rita , Ottaviani Gianpiero 
Published: September 2011

ABSTRACTWe report the study of the thermoelectric properties of degenerate, boron-doped polycrystalline silicon on insulator structures. The occurrence of a regime where both the Seebeck coefficient and the conductivity increase is confirmed. This results in a power factorPof 13 mW K-2m-1. We propose that such high values ofPmay be determined by adiabatic energy filtering occurring at grain boundaries decorated by segregated boron.
Crystal Lattice Controlled SiGe Thermoelectric Materials with High Figure of Merit
Authors: Kim Hyun Jung , Park Yeonjoon , King Glen C. , Lee Kunik , Choi Sang H. 
Published: September 2011

ABSTRACTDirect energy conversion between thermal and electrical energy, based on thermoelectric (TE) effect, has the potential to recover waste heat and convert it to provide clean electric power. The energy conversion efficiency is related to the thermoelectric figure of merit ZT expressed as ZT=S2σT/κ, T is temperature, S is the Seebeck coefficient, σ is conductance and κ is thermal conductivity. For a lower thermal conductivity κ and high power factor (S2σ), our current strategy is the development of rhombohedrally strained single crystalline SiGe materials that are highly [111]-oriented twinned. The development of a SiGe “twin lattice structure (TLS)” plays a key role in phonon scattering. The TLS increases the electrical conductivity and decreases thermal conductivity due to phonon scattering at stacking faults generated from the 60° rotated primary twin structure. To develop high performance materials, the substrate temperature, chamber working pressure, and DC sputtering power are controlled for the aligned growth production of SiGe layer and TLS on a c-plane sapphire. Additionally, a new elevated temperature thermoelectric characterization system, that measures the thermal diffusivity and Seebeck effect nondestructively, was developed. The material properties were characterized at various temperatures and optimized process conditions were experimentally determined. The present paper encompasses the technical discussions toward the development of thermoelectric materials and the measurement techniques.
Contact Resistivity of Laser Annealed SiGe for MEMS Structural Layers Deposited at 210°C
Authors: El-Rifai Joumana , Witvrouw Ann , Aziz Ahmed Abdel , Puers Robert , Van Hoof Chris , Sedky Sherif 
Published: September 2011

ABSTRACTLowering the silicon germanium (SiGe) deposition temperature from the current 450°C to below 250°C will enable processing Micro Electro-Mechanical Systems (MEMS) on flexible polymer instead of on rigid silicon substrates or glass carriers. A major disadvantage of such a low temperature deposition is that the films are amorphous, with high hydrogen content and yield poor electrical and mechanical properties. To ensure films suitable for MEMS applications, a post-deposition laser annealing (LA) treatment is used. It is essential that the contact resistance between the SiGe MEMS structural layer and any lower electrode is minimized. In this work we investigate what beneficial effect a LA treatment can have on the contact resistivity of an initially amorphous SiGe MEMS structural layer with a bottom TiN electrode. We report a minimum contact resistivity of 2.14×10−3Ωcm2.
Film Conductivity Controlled Variation of the Amplitude Distribution of High-temperature Resonators
Authors: Schmidtchen Silja , Richter Denny , Xia Han , Fritze Holger 
Published: September 2011

ABSTRACTHigh-temperature measurements of the spatial distribution of the displacement characteristics of a thickness shear mode langasite (La3Ga5SiO14) resonator are obtained using a laser Doppler interferometer. Thereby, the resonator is excited in the fundamental mode and the third overtone. Further, the resonator is coated with a gas sensitive CeO2-x film which exceeds the metal electrode. In reducing atmospheres the conductivity of the film increases and induces an increase of the effective electrode area. This effect leads to a broadening of the mechanical displacement distribution. The latter depends strongly on the size of the excited part of the resonator which is determined by the effective size of the electrodes. The direct determination of the mechanical displacement at different oxygen partial pressures confirms a model as derived from the electrical impedance of resonator devices [1]. Further, information about the mass sensitivity distribution of resonators is obtained since the property is directly proportional to the amplitude.
Low-Temperature Growth of Epitaxial Semiconductor Nanostructures and Films
Authors: Findikoglu Alp T. , Perea Daniel E. , Picraux S. T. 
Published: September 2011

ABSTRACTThe growth of epitaxial semiconductor nanostructures and films at low temperatures is important for semiconductor technology because it allows the possibility of monolithically integrating different high-performance single-crystalline semiconductor structures directly onto low cost technologically important substrates. At sufficiently low temperatures this can enable, for example, Si or Ge device fabrication on flexible substrates such as plastics. We have studied the reduced-temperature liquid-mediated growth of Ge nanostructures and films on crystalline template layers on non-single-crystalline substrates in a low-pressure chemical vapor deposition (LPCVD) system. The heteroepitaxial process is implemented by the Au seeded vapor-liquidsolid (VLS) catalytic growth technique with germane below 400 ºC. Crystalline template layers were prepared with ion-beam-assisted-deposition (IBAD) texturing and electron-beam evaporation on glass substrates. A thin layer of e-beam evaporated Au forms the catalyst layer, upon which we grew Ge films at 386 ºC. Scanning electron microscopy and x-ray diffraction results indicated that both Ge islands and nanowires grew heteroepitaxially on the crystalline template layers on glass substrates with good alignment over large areas.
Fostering a Conceptual Understanding in Undergraduate Materials Education: A Multivariable Animated Spreadsheet Approach
Authors: Sinex Scott A. , Halpern Joshua B. 
Published: September 2011

ABSTRACTWe describe how students explore materials science concepts using animated interactive spreadsheets. An engaging pedagogy is created in the classroom using spreadsheets in a way that initially camouflages mathematical complexity, which can later be revealed and taught. Use of off-the-shelf spreadsheet software, including freeware makes these spreadsheets universally available.
Novel fabrication method of ZnO films utilizing solid-phase crystallized seed layers
Authors: Itagaki Naho , Kuwahara Kazunari 
Published: September 2011

ABSTRACTA novel fabrication method of ZnO films utilizing solid-phase crystallized seed layers has been developed. In this method, solid phase crystallization (SPC) is performed by annealing amorphous ZnON films, which are prepared by sputtering of ZnO targets in Ar/N2 mixed gases, in an oxidization atmosphere. The grain size of ZnO films deposited on the seed layers is significant larger than that of ZnO films directly deposited on glass substrates, which is considered to be due to the low grain density of seed layers. By utilizing this technique, the resistivity of ZnO:Al (AZO) films is decreased from 20 × 10-4 Ωcm to 5 × 10-4 Ωcm at the film thickness of 30nm. Furthermore, we observed that SPC seed layers are in-plane aligned when Al2O3 substrates are used, which suggests that the fabrication method proposed here is also promising for synthesizing epitaxial ZnO films.
Modeling of Polycrystalline Organic Thin-Film Transistor and Schottky Diode for the Design of Simple Functional Blocks
Authors: Raja M. , Donaghy D. , Myers R. , Eccleston W. 
Published: September 2011

ABSTRACTWe present analytical models for organic thin film transistors (OTFTs) and Schottky diodes based on polycrystalline semiconductors. The OTFT model is developed using a well-established approach previously developed for polysilicon, with slight modification for organics. The model predicts voltage and temperature dependencies on the various device and circuit parameters. A good agreement is obtained with experimental data of TIPS-based OTFTs. Essential parameters such as the characteristic temperature and Meyer-Neldel Energy extracted using the model with TIPS OTFTs data were in agreement with those obtained from Schottky diode measurements.
High thermally stable hybrid materials for optical interconnects
Authors: Sato Tetsuo 
Published: September 2011

ABSTRACTOptical materials in the optical circuit board are required to overcome soldering process. In detail, the material should not have absorption and shape changes after several tens of seconds heating at around 250 °C. For such application field, we have developed a novel organic-inorganic hybrid material having a high thermal stability and low absorption at telecom wavelength.The hybrid material was designed to solvent less resin, which is free radical curable with heating at 150 °C or UV exposure at room temperature, for the sake of device fabrication activity. We demonstrated the waveguides fabrication by photolithography, and obtained high uniformity cured materials. Transparency of the waveguide sample at telecom wavelength was 0.10 dB/cm at 850 nm, 0.12 dB/cm at 1060 nm, 0.29 dB/cm at 1310 nm, and 0.45 dB/cm at 1550 nm. These values are good low attenuation for the Near-IR optical communication in optical interconnects. Without any further treatment such as post bake, the cured materials showed a high thermal stability. The temperature of 5 % weight loss was over 400 °C, and the transparency hardly changed after 1 min heating at 300 °C.In addition, the cured material showed a high refractive index of n=1.60 at 633 nm and a low curing shrinkage about 4.7 %. From these properties, the developed organic-inorganic material is expected to be beneficial for the optical interconnection such as micro lenses and optical packages.
First Principles Predictions of Intrinsic Defects in Aluminum Arsenide, AlAs
Authors: Schultz Peter A. 
Published: September 2011

ABSTRACTThe structures, energies, and energy levels of a comprehensive set of simple intrinsic point defects in aluminum arsenide are predicted using density functional theory (DFT). The calculations incorporate explicit and rigorous treatment of charged supercell boundary conditions. The predicted defect energy levels, computed as total energy differences, do not suffer from the DFT band gap problem, spanning the experimental gap despite the Kohn-Sham eigenvalue gap being much smaller than experiment. Defects in AlAs exhibit a surprising complexity—with a greater range of charge states, bistabilities, and multiple negative-U systems—that would be impossible to resolve with experiment alone. The simulation results can be used to populate defect physics models in III-V semiconductor device simulations with reliable quantities in those cases where experimental data is lacking, as in AlAs.
Non-melt Laser Thermal Annealing of Shallow Boron Implantation for Back Surface Passivation of Backside-Illuminated CMOS Image Sensors
Authors: AIT FQIR ALI-GUERRY Zahra , HUET Karim , DUTARTRE Didier , BENEYTON Rémi , BENSAHEL Daniel , NORMANDON Philippe , LU Guo-Neng 
Published: September 2011

ABSTRACTBack surface passivation is one of the major challenges in the backside illuminated sensor technology. Ion implantation followed by non-melt pulsed Laser Thermal Annealing (LTA) has been identified as a promising candidate to address this issue. In this work, a shallow B-doped layer is implanted at the backside, further activated using LTA in the non-melt regime. LTA process effectiveness in terms of crystal damage recovery as well as dopant diffusion and activation is studied through room-temperature photoluminescence, Secondary Ion Mass Spectroscopy and four-point probe sheet resistance. These studies demonstrate that non-melt LTA with multiple pulses induces high activation without visible diffusion with an effective curing of the implantation-induced crystalline defects. This is made possible thanks to a submicrosecond process timescale coupled to a reasonable number of shots as shown by thermal simulations and simple diffusion estimations.