bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Emission of Terahertz Radiation from Doped Silicon Devices
Authors: Pengcheng Lv , Kolodzey James , Thomas Troeger R. , Kim Sangcheol , Ray S.K. 
Published: April 2011

ABSTRACTRecent interest in biological imaging, remote sensing, and biochemical spectroscopy has made nanoscale Terahertz (THz) emitters based on semiconductors become extremely attractive. THz lasers with good performance (emitting over 1 milliWatt CW at 10 K) have been fabricated from the group III-V compounds by molecular beam epitaxy, but such devices are complex with over 500 quantum wells and barriers and are incompatible with low cost Si processing. Similar devices from the SiGe system have had difficulties because the strain limits the total number of active layers, and have produced relatively poor performance (peak powers near 5 nW), even using strain symmetric active regions on virtual substrates of relaxed SiGe buffers. We report here on the characteristics of a new type of THz emitting device with higher powers (above 0.1 milliWatt) based on radiative impurity transitions in doped silicon, which can be simply fabricated without Ge alloying.The THz emitters were fabricated from both p-type and n-type doped silicon wafers with typical resistivities of 5 Ω-cm, using conventional photolithography and metal contact lift off. Samples were electrically pulsed and the electroluminescence was measured by Fourier Transform Infrared spectrometry. At 4.2 K, the emission spectra showed several peaks centered around 8.1 THz for the boron doped device, 7 to 13 THz for the gallium doped device, and 6.6 THz for the phosphorus doped device. The electroluminescence was attributed to radiative transitions from excited p-like to s-like hydrogenic dopant states, with emission energies in remarkable agreement with the known dopant absorption levels. Current-voltage measurement suggested an excitation mechanism based on impact ionization of neutral dopants by hot carriers. The net quantum efficiency (emitted photons per injected electron) was estimated to be up to 2 × 10-3. The temperature dependence will be reported with operation above 30 K.
Complex Diameter Modulations in Silicon Carbide Nanowire Growth
Authors: Kohno Hideo , Yoshida Hideto 
Published: April 2011

ABSTRACTSilicon carbide nanowires were grown via a self-organized process. Some of the nanowires showed complex diameter fluctuations. The fluctuation was studied from the viewpoints of random walk and fractal. Power spectrum analysis of a fluctuation revealed that the fluctuation was not periodic and that the spectrum was colored. The distribution of increments had a fat tail which was not Gaussian but obeyed power law. Thus the diameter fluctuation was interpreted as a Lévy Flight. In addition, the fluctuation also showed multiaffine scaling.
Silicon Nanowires: Doping Dependent N- and P- Channel Fet Behavior
Authors: Byon Kumhyo , Fischer John E. , Adu Kofi W. , Eklund Peter. C. 
Published: April 2011

ABSTRACTThe electrical transport properties of field effect transistor (FET) devices made of silicon nanowires (SiNWs) synthesized by pulsed laser vaporization (PLV) were studied. From as-grown PLV-SiNW FET, we found p-channel FET behavior with low conductance. To improve conductance, spin on glass (SOG) and vapor doping were used to dope phosphorus and indium into SiNW, respectively. From doping after synthesis, we could successfully make both n- and p-channel FET devices.
X-Ray Studies of Near-Frictionless Carbon Films.
Authors: Mehta Nikhil J , Roy Sujoy , Johnson Jacqueline Anne , Woodford John , Zinovev Alexander , Islam Zahirul , Erdemir Ali , Sinha Sunil , Fenske George , Prorok Barton 
Published: April 2011

ABSTRACTCarbon-based coatings exhibit many attractive properties that make them good candidates for a wide range of engineering applications. Tribological studies of the films have revealed a close correlation between the chemistry of the hydrocarbon source gases and the coefficients of friction and wear rates of the diamond-like carbon films. Those films grown in source gases with higher hydrogen-to-carbon ratios had much lower coefficients of friction and wear rates than did films derived from source gases with lower hydrogen-to-carbon ratios. The mechanism for this low friction is as yet not properly understood. Ongoing structural characterization of the films at Argonne National Laboratory is gradually revealing this mechanism. Recent studies have included x-ray photoelectron spectroscopy (XPS), near edge x-ray absorption fine structure (NEXAFS) and x-ray reflectivity (XRR). XPS showed ∼10% oxygen at the surface, which was largely removed after a 1 minute sputter; NEXAFS showed a high sp2:sp3 ratio implying a highly graphitic material; and XRR has given a comprehensive depth profile, with three layers of increasing density as the substrate was approached. The paper discusses the results and correlation with previous friction measurements.
Structural, Mechanical and Tribological Properties of TiN and CrN Films Deposited by Reactive Pulsed Laser Deposition
Authors: Phani A. R. , Krzanowski J. E. 
Published: April 2011

ABSTRACTNitride thin films have potential applications in different areas of silicon device technology, namely as diffusion barrier in metallization schemes, rectifying and ohmic contacts, and gate electrodes in field effect transistors. In the present investigation, TiN and CrN films have been deposited by reactive pulsed laser deposition technique using Ti and Cr targets at 10mTorr background pressure of N2. Si (100) and AISI 440C steel substrates were used for the present study. Films were deposited at different temperatures in the range of 200°C to 600°C. The deposited films exhibited densely packed grain, with smooth and uniform structures. X-ray Photoelectron Spectroscopy (XPS) analysis of the films showed and 50% Ti and 40% of N in TiN films, 45% of Cr and 45% of N in CrN films deposited on Si (111), with the balance mostly oxygen, indicating near stoichiometric composition of the deposited nitride thin films. Hardness of the films changed from 22 GPa at 200°C to 30 GPa at 600°C for TiN, whereas for CrN we obtained 26 GPa at 200°C to 31 GPa at 600°C. The residual stress in the films showed a change from compressive stress at 200°C to tensile stress at 600°C in both the cases. Friction coefficient of the films were measured by pin-on-disk technique for all films, up to the tested limit of 10, 000 cycles at 1 N load and found to be very high (≥ 1) in both cases.
Tribological Aspects of AlN-TiN Thin Composite Films
Authors: Waters C. , Young G. , Yarmolenko S. , Wang X. , Sankar J. 
Published: April 2011

AbstractPhysical properties, and the friction and wear are important issues in small-scale applications, it is therefore essential that the materials used have good micromechanical and tribological properties. The adhesion, fracture toughness and wear properties of AlN-TiN thin composite films is being investigated in this study. The multilayered structures are generated using Pulsed Laser Deposition (PLD). The durability and functionality of thin films is subject to the adhesion between the coating and the underlying substrate in addition to it's resistance to cracking. The magnitude of the critical load during a scratch test is related to the adhesion of the substrate to the coating. In this test a Berkovich indenter is used for measurements and is drawn across the surface of a coating under an increasing load. The magnitude of the critical load will be studied for various films from a monolayer TiN film to different AlN-TiN films and those relative results compared to their facture toughness and their wear properties. Despite the adhesion, the critical load depends on several other parameters including the friction coefficient. The critical characteristic load is shown to depend on the number of layers and the relative AlN-TiN thickness. The fracture toughness showed a weak dependence on the layer characteristics.
Synthesis and Characterization of Carbon Nitride Thin Film with Evidence of Nanodomes
Authors: Chowdhury S. , Laugier M. T. 
Published: April 2011

ABSTRACTWe have reported the synthesis of carbon nitride thin films with evidence of formation of carbon nanodomes over a range of substrate temperature from 50 °C to 550 °C. An RF magnetron sputtering system was used for depositing carbon nitride films. The size of the nanodomes can be controlled by deposition temperature and increases from 40–80 nm at room temperature to 200–400 nm at high temperature (550 °C). Microstructural characterization was performed by AFM. Electrical characterization shows that these films have conductive behaviour with a resistivity depending on the size of the nanodomes. Resistivity values of 20 mΩ-cm were found for nanodomes of size 40–80 nm falling to 6 m?-cm for nanodomes of size 200–400 nm. Nanoindentation results show that the hardness and Young's modulus of these films are in the range from 9–22 GPa and 100–168 GPa respectively and these values decrease as the size of the nanodomes increases. GXRD results confirm that a crystalline graphitic carbon nitride structure has formed.
Matrix Assisted Pulsed Laser Evaporation of Dexamethasone Thin Films
Authors: Patz Timothy M. , Doraiswamy Anand , Narayan Roger J. , Menegazzo Nicola , Kranz Christine , Mizakoff Boris , Zhong Yinghui , Bellamkonda Ravi , Modi Rohit , Chrisey Douglas B. 
Published: April 2011

ABSTRACTWe have demonstrated deposition of dexamethasone thin films via matrix assisted pulsed laser evaporation (MAPLE). Infrared analysis revealed that dexamethasone thin films deposited by MAPLE and by drop casting had a similar absorbance spectra. AFM imaging of the MAPLE-deposited dexamethasone thin film revealed 2–10 μm punctuate ring-like structures. Deposited dexamethasone was tested for positive bioactivity by treating primary microglia cells with lipopolysacchride and measuring nitric oxide (NO) production. The successful deposition of dexamethasone thin films can be used on neural implants to prevent tissue injury and inflammatory response.
Novel electroporation System for both Gram-negative and Gram-positive Bacteria Assisted by Multi-Walled Carbon Nanotubes
Authors: Giersig M. , Firkowska I. , Trosczcynska J. , Correa Duarte M. A. , Rojas-Chapana J. A 
Published: April 2011

ABSTRACTGram positive (Lactoccocus lactis) and Gram negative bacteria (Escherichia coli) were used to study the interaction of water-dispersible muti-walled carbon nanotubes (CNTs) with the bacterial cell envelope during microwave (MW) energy exposure. It was observed that the addition of a tiny amount of CNTs to a medium containing bacteria and subsequent exposure of the samples to MW, leads to an intimate contact between the CNT tips and the cell envelope. This phenomenon can be explained in terms of attractive forces between opposite charges of polar structures. Since CNTs under MW irradiation behave like electric dipoles, this would make it possible for the CNTs to target the cell surface without inducing changes in the cell shape and viability. Thus, the electrochemical properties of CNTs and their capillarity make them useful tools for cell manipulation, and therefore for the intracellular transport of drugs, dyes or biomolecules.
Labeling Cells with Silver/Dendrimer Nanocomposites
Authors: Lesniak Wojciech , Shi Xiangyang , Bielinska Anna , Janczak Katarzyna , Sun Kai , Baker James R. , Balogh Lajos P. 
Published: April 2011

ABSTRACTWe have developed water-soluble, biocompatible, fluorescent, and photostable silver/dendrimer nanocomposites that have a potential to be used for in vitro cell labeling. A PAMAM_E5.NH2 dendrimer was used as a template to prepare first a silver-dendrimer complex in an aqueous solution at biologic pH=7.4. Conversion into nanocomposite was achieved by irradiating the solution of the [(Ag+)25-PAMAM_E5.NH2] complex by UV light to reduce the bound Ag+ to zero-valent Ag0 atoms, which were simultaneously trapped in the dendrimer network. Results indicate that the {(Ag0)25-PAMAM_E5.NH2} silver/dendrimer nanocomposite forms positively charged single particles of 4–5 nm under the experimental conditions used. The dendrimer nanocomposite proved to be fluorescent. Toxicity testing of {(Ag0)25-PAMAM_E5.NH2} nanocomposite revealed a behavior similar to the template dendrimer. Intracellular internalization of the silver nanocomposite and cell labeling capabilities was confirmed by confocal microscopy.
MAPLE Direct Write (DW) patterning of Bio-active Ceramic Nanocomposites
Authors: Doraiswamy A. , Patz T. M. , Narayan R. J. , Harris L. , Auyeung R. , Modi R. , Chrisey D. B. 
Published: April 2011

ABSTRACTA laser-based approach, Matrix Assisted Pulsed Laser Direct Write (MAPLE) technique is used to demonstrate two-dimensional direct writing of ceramics such as hydroxyl-apatite and zirconia, for developing inorganic scaffolds. We also demonstrate the patterning of live MG63 osteoblast cells onto various substrates. Our results show successful direct writing of ceramics and live cells concurrently, with a growth profile similar to that of as-deposited cells. After several days of growth, a live/dead assay shows live cells suggesting the biocompatibility of the ceramic and the viability of the process. This investigation demonstrates a novel method of developing heterogeneous tissue scaffolds, such as a cell-ceramic composite by CAD/CAM patterns.
N-isopropylacrylamide-based Copolymers with Time-dependent LCST for a Bioresorbable Carrier
Authors: Lee Bae Hoon , Vernon Brent 
Published: April 2011

ABSTRACTTo develop a new class of in situ-forming, injectable, and biodegradable polymeric biomaterials based on time-dependent lower critical solution temperature (LCST) properties for localized delivery, copolymers of N-isopropylacrylamide (NIPAAm), 2-hydroxyethyl methacryl lactate (HEMA-lactate) and acrylic acid (AAc) were prepared with varying mole ratios of monomers. The copolymers showed LCST and gelation properties below body temperature in 0.1 N PBS solution of pH 7.4. The LCST and gelation temperature of the copolymers decreased as the HEMA-lactate content of the copolymers was increased. The copolymers also showed time-dependent LCST and gelation properties in 0.1 N PBS solution of pH 7.4 owing to hydrolysis of HEMA-lactate. Hydrolysis of HEMA-lactate caused the polymers to be more hydrophilic, resulting in an increase in LCST and gelation temperature. All the polymers with about 6 mol % AAc exhibited LCST and gelation temperature above body temperature after complete hydrolysis of HEMA-lactate.
Formation of Titania Submicron-Scale Rod Arrays on Titanium Substrate and In Vitro Biocompatibility
Authors: Hayakawa Satoshi , Liu Yongxing , Okamoto Kazuya , Tsuru Kanji , Osaka Akiyoshi 
Published: April 2011

ABSTRACTTitania submicron-scale rod arrays were fabricated on metallic titanium (α-Ti) surfaces by coating a layer of sodium tetraborate on titanium substrates and subsequent thermal treatment. Thin-film X-ray diffraction analysis indicated that the sodium tetraborate gave rutile (TiO2: PDF# 21-1276) submicron-scale rod arrays. The rods in the arrays are parallel to each other in the grain of metallic titanium surface. The titania submicron-scale rod arrays deposited apatite within 7 days after being soaked in a simulated body fluid, indicating that the rod arrays exhibit in vitro bioactivity.
Nanofeaturing materials for specific cell responses
Authors: Curtis Adam 
Published: April 2011

ABSTRACTA review of the ways in which cells react to nanofeatured surfaces is given. One of the prime reactions is of adhesion or otherwise to such surfaces. Topography appears to be of considerable importance and a wide range of cell properties are affected by the type, scale and regularity of topography. Chemistry can be combined with topography to fine- tune effects. Mechanical forces are also of importance but in practice it is hard to control these.Examples will be given of methods of controlling adhesion, morphology, orientation, movement, phagocytic activity and activation and gene expression of cells, Effects vary according cell type and also the spacing and size of nanofeatures. A discussion of the application of these findings to the medical devices concludes this short review.
Effect of Nano-to Micro-Scale Surface Topography on the Orientation of Endothelial Cells
Authors: Uttayarat P. , Lelkes Peter I. , Composto Russell J. 
Published: April 2011

ABSTRACTThe effect of grating textures on the alignment of cell shape and intracellular actin cytoskeleton has been investigated in bovine aortic endothelial cells (BAECs) cultured on a model cross-linked poly(dimethylsiloxane) (PDMS). Grating-textured PDMS substrates, having a variation in channel depths of 200 nm, 500 nm, 1 μm and 5 μm, were coated with fibronectin (Fn) to promote endothelial cell adhesion and cell orientation. As cells adhered to the Fn-coated surface, the underlying grating texture has shown to direct the alignment of cell shape, F-actin and focal contacts parallel to the channels. Cell alignment was observed to increase with increasing channel depths, reaching the maximum orientation where most cells aligned parallel to channels on 1-μm textured surface. Immunofluorescence studies showed that F-actin stress fibers and vinculin at focal contacts also aligned parallel to the channels. Cell proliferation was found to be independent of grating textures and the alignment of cell shape was maintained at confluence.
Competitive adsorption of plasma proteins on polysaccharide-modified silicon surfaces
Authors: Ombelli Michela , Costello Lauren B. , Meng Qing Cheng , Composto Russell J. , Eckmann David M. 
Published: April 2011

ABSTRACTThe initial response of blood exposed to an artificial surface is the adsorption of blood proteins that triggers a number of biological reactions such as inflammation and blood coagulation. Competitive protein adsorption plays a key role in the hemocompatibility of the surface. The synthesis of nonfouling surfaces is therefore one of the major prerequisites for devices for biomedical applications. Polysaccharides are the main components of the endothelial cell glycocalyx and have the ability to reduce nonspecific protein adsorption and cell adhesion and, therefore, are generally coupled with a wide variety of surfaces to improve their biocompatibility. We have developed a procedure for covalently binding dextran and sodium hyaluronate (HA) on silicon wafers and we have been able to achieve a high level of control over the surface properties of the coatings. In the present research effort we focus on a detailed investigation of competitive bovine serum albumin (BSA) and bovine fibrinogen (Fg) adsorption on dextran- and HA-modified silicon surfaces. Polysaccharide based biomimetic layers preferentially adsorb BSA and, in general, strongly suppress protein adsorption with respect to bare silicon and APTES-activated silicon surfaces used as control.
Influence of Precursor Design on the Growth of Nanomaterials
Authors: Mathur Sanjay , Shen Hao , Hemmer Eva , Ruegamer Thomas , Holzapfel Christian 
Published: April 2011

ABSTRACTChemical processing of inorganic materials demands an understanding of the precursor chemistry at the molecular level. Although chemical compounds imitating atomic composition or bonding features of solid phases are efficient templates for a controlled evolution of nano-matter, the intrinsic advantages of this approach, such as atomic level mixing of the constituents and phase-selective synthesis, rely on the chemistry involved in the transformation of molecules to materials. Therefore, a better understanding of principles underlying chemical processing is necessary to enable a rational synthesis of materials. We have deposited MgAl2O4 thin films by the chemical vapor deposition of two Mg-Al alkoxide precursors, [MgAl2(OPri)8] and [MgAl2(OBut)8], which reveal that precursor attributes such as vapor pressure and ligand elimination mechanisms influence the microstructure and material properties of the spinel films. Under similar growth conditions, [MgAl2(OPri)8] produces rough and poorly crystalline spinel films, whereas crystalline deposits and dense microstructure were obtained in the case of [MgAl2(OBut)8]. The films were characterized by XRD, SEM, TEM, XPS and nano-indentation studies.
Crystal Chemistry of Some Organically Templated Metal Fluorides: The Crystal Structure of [C2N2H10]0.5[Y2F7]
Authors: Lightfoot Philip , Stephens Nicholas F. 
Published: April 2011

ABSTRACTAs part of an ongoing program exploring the solvothermal synthesis and crystal chemistry of organically templated metal fluorides, a novel compound [C2N2H10]0.5[Y2F7] has been isolated. The structure consists of a continuous 3-D array of YF8 and YF9 polyhedra linked through corners, edges and faces to enclose small channels in which the template cations sit. The structure is stable up to 400°C, at which point template loss causes structural collapse. This structure represents the first yttrium or rare-earth fluoride templated by organic cations, and suggests a wide variety of novel structure types will be amenable via such routes, possibly leading to novel families of luminescent materials.
Charge and coordination states of iron cations in La1-xMexFeO3-y (Me=Ca, Sr, Ba) prepared by mechanochemical route as related to oxygen reactivity
Authors: Isupova Lyubov A. , Pavlyukhin Yurii T. , Rogov Vladimir A. , Alikina Galina M. , Tsybulya Sergei V. , Yakovleva Irina S. , Sadykov Vladislav A. 
Published: April 2011

ABSTRACTThis work presents results of investigation of the charge and coordination state of Fe cations in La1-xMexFeO3-y perovskites prepared by mechanochemical route by using MÖssbauer spectroscopy as related to bulk oxygen reactivity in H2 or in CH4 temperature-programmed reduction (TPR).
The Synthesis of III-V Semiconductor InSb Nanoparticles by Solvothermal Reduction Reactions
Authors: Lezaeta Monica De , Lam Margaret , Black Shira , Chang Baohe , Gersten Bonnie 
Published: April 2011

ABSTRACTInSb has a large carrier mobility and a high sensitivity in the infrared wavelength range (3–5 μm), which makes it a good quantum dot material for infrared (IR) detectors. In this study, the synthesis of the nanocrystalline III-V semiconductor indium antimonide (InSb) by solvothermal reduction methods was investigated. InSb was synthesized by using indium (III) chloride and antimony (III) chloride as the starting materials and sodium borohydride as the reducing agent. Pure-phase InSb was successfully produced with diethylenetriamine and tetraethylenepentamine as the solvents and a Schlenk line apparatus as the reaction vessel. X-ray diffraction (XRD) was used to verify the successful production of InSb and transmission electron microscopy (TEM) was used to determine the particle size and shape of the product. In the future, growth kinetics of the particles will be investigated as they relate to their spectroscopic quantum confinement effects.
Preparation of (Pb, Ca)(Fe0.5Nb0.5)1-yTiyO3 Perovskite Ceramics by a Reaction-Sintering Process
Authors: Liou Yi-Cheng , Chen Jen-Hsien , Lu Hsueh-Yung 
Published: April 2011

ABSTRACTSynthesis of (Pb0.45Ca0.55)(Fe0.5Nb0.5)1-yTiyO3 (y=0 and 0.1; PCFN and PCFNT) ceramics by a reaction-sintering process was investigated. The mixture of raw materials was pressed and sintered into ceramics without any calcination stage involved. The density 5.88g/cm3 (91.6% of the theoretical value) is reached at 1270°C for 2 h soak time in PCFN. Densification increased as B-site was substituted by 10% Ti and a density value 6.21g/cm3 (98.1% of theoretical value) was obtained after 2 h sintering at 1270°C. Grains are of 4.6–19.3μm in PCFN and 2.5–16.5μm in PCFNT at 1150–1270°C. Grain growth was retarded as the B-site was substituted by 10% Ti in PCFN ceramics.