bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Novel Method For The Diffusion Of Boron In 60-80 Micron Size Natural Diamond Type II/A Powder
Authors: Mendez Adrian E. , Prelas Mark A , Glascock Michael , Ghosh Tushar K 
Published: April 2011

ABSTRACTThe purpose of this paper is to report the experimental results of boron doping on 60-80 micron size diamond particles using Field Enhanced Diffusion with Optical activation (FEDOA) [1-5]. Diamond is a wide band gap material with unique combinations of optical, thermal, mechanical and electronic properties that can be useful for a number of applications including optoelectronic applications and micro sensor technology. The incorporation of boron into diamond has been proven to change its electrical properties and convert the diamond from insulator to a p-type semiconductor [3]. A promising technique for incorporation of impurities into diamond is FEDOA. FEDOA drives impurities into single crystalline diamond material and we have used this method in this study [5-7]. FEDOA uses a combination of thermal diffusion with bias plus thermal ionization and optical ionization I simultaneously. A modified version of FEDOA was implemented for the diffusion of boron in natural diamond type II/a powder of size 60-80 microns (Figure 1). The diamond powder was obtained from Microdiamant and has 99.9% purity. The boron powder used in the experiment was amorphous, 325 mesh 90 %(Assay), Mg (5%) nominal obtained from AESAR. A ratio of 3:1 Boron-Diamond mixture was used for the doping process. A heating element and a diamond-boron powder mixture holder were designed and incorporated in the FEDOA system. Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS) were used to study the diamond-doped morphology and identify impurities. Boron and hydrogen concentration results in the doped samples were studied using Prompt Gamma Neutron Activation Analysis (PGNAA) at the University of Missouri Research Reactor (MURR). Raman analysis of the treated samples was done as part of this work. The experimental results and analysis show that the samples were doped with boron. It was also found that samples with high boron concentration exhibited a high electrical conductivity. This work presents additional evidence that boron can be diffused into natural diamond powders. It also demonstrates that the FEDOA diffusion process is not only a powerful technique for the diffusion of impurities into wide band-gap materials in the form of single crystal plates, polycrystalline plate but also in a powder form with the modified FEDOA process.
Compression Testing and Microstructure of Heat-Treatable Aluminum Periodic Cellular Metal
Authors: Bouwhuis B. A. , Hibbard G. D. 
Published: April 2011

ABSTRACTPeriodic cellular metals (PCMs) can offer higher specific strengths and stiffnesses than conventional (i.e. stochastic) metallic foams. This study examines the effects of PCM microstructure and loading conditions on the mechanical performance.PCM cores with 95% open porosity were constructed from perforated 6061 aluminium alloy sheets using a perforation-stretching method. This method places planar, periodically-perforated sheet metal in an alternating-pin jig. The pins apply force out-of-plane, plastically deforming the sheet metal into a truss-like array of struts (i.e. metal supports) and nodal peaks (i.e. strut intersections). Micro-hardness profiles were taken in the PCM struts to investigate microstructural evolution during fabrication and after heat treatment.Truss cores were tested in two limiting uniaxial compression conditions. In the first, the PCM cores are placed between smooth compression platens where the nodes are laterally free and compressive forces are resisted through PCM node-bending (i.e. free compression). In the second, the PCM cores were placed between plates where the nodes are laterally confined and compressive forces are resisted through PCM beam-buckling (i.e. confined compression). Compression response was analyzed in terms of peak compressive strength, elastic modulus, and energy density absorbed upon densification; response values were used to illustrate the effect of compression test conditions. In addition, PCM cores were tested in the age-hardened state and annealed state to determine microstructural effects on compressive response.Analysis of PCM response in free- and confined-compression conditions indicates a greater force resistance in beam-buckling over node-bending resistance mechanisms. The compressive strength, elastic modulus, and energy density of heat-treatable AA6061 PCMs are be found to respond: 1) over a wide range of value, dependent on the microstructure; 2) over a wide range of value, dependent on the PCM compression conditions; and 3) equally, if not more repeatable and with higher compressive strength-to-weight ratio than conventional metal foams.
Effects of Extreme Radiation Environment on Composite Materials
Authors: Zhou J. , Moore Jerrel , Calvin Vernon , Wilkins Richard , Vilarino Sofia Martinez , Zhong Yang , Gersey Brad , Thibeault Sheila 
Published: April 2011

ABSTRACTFuture manned space travel will go beyond the Lower Earth Orbit into deep space exploration and providing protection from space radiation is a major challenge. It is essential to study the effects of the space environment on materials to ensure safe and successful missions.This paper summarized the studies of two materials, in-site regolith composites and LTM 45 composites, for potential applications in space radiation environments. The effects of radiation on the mechanical and thermal properties of the composites were investigated. The radiation shielding effectiveness of in-situ composites and low temperature molding materials was analyzed. The work was part of the efforts in study and development of the multifunctiaonal materials for long-term radiation exposures to ensure effective radiation shielding and maintaining integrity of materials' mechanical and thermal properties for future space missions.
Investigation of Spreading and Traction of Human Osteosarcoma Cells on Microgrooved Polydimethylsilaxone Surfaces
Authors: Cao Yifang , Chen Jianbo , Soboyejo Winston O. 
Published: April 2011

ABSTRACTThe paper presents the recent results of the spreading and traction of human osteosarcoma cells on soft polydimethylsiloxane (PDMS) microgrooved surfaces. The results show that the cell tractions resulted in significant deformation of the microgrooves. The tractions were calculated, and found to be in good agreement with the results from other studies. The results suggest that the cell spreading-induced soft substrate deformation needs to be considered in the design of implantable bioMEMS structures.
Biocompatible Silver-containing a-C:H and a-C coatings: A Comparative Study
Authors: Endrino Jose Luis , Allen Matthew , Galindo Ramon Escobar , Zhang Hanshen , Anders Andre , Albella Jose Maria 
Published: April 2011

ABSTRACTHydrogenated diamond-like-carbon (a-C:H) and hydrogen-free amorphous carbon (a-C) coatings are known to be biocompatible and have good chemical inertness. For this reason, both of these materials are strong candidates to be used as a matrix that embeds metallic elements with antimicrobial effect. In this comparative study, we have incorporated silver into standard diamond-like carbon (DLC) coatings by plasma ion implantation and deposition (PIII&D) using methane (CH4) plasma and simultaneously depositing Ag from a pulsed cathodic arc source. In addition, we have grown amorphous carbon – silver composite coatings using a dual-cathode pulsed filtered cathodic-arc (FCA) source. The silver atomic content of the deposited samples was analyzed using glow discharge optical spectroscopy (GDOES). In both cases, the arc pulse frequency of the silver cathode was adjusted in order to obtain samples with approximately 5 at.% of Ag. Surface hardness of the deposited films was analyzed using the nanoindentation technique. Cell viability for both a-C:H/Ag and a-C:/Ag samples deposited on 24-well tissue culture plates has been evaluated.
Ordering and shape tuning of Ge islands on metal-patterned Si
Authors: Robinson Jeremy T. , Cao Yifan , Walko Donald , Arms Dohn , Liddle J. Alexander , Dubon Oscar D. 
Published: April 2011

ABSTRACTIn semiconductor epitaxy, a central challenge for the formation of ordered arrays of nanostructures, such as quantum dot islands, is the realization of processing routes to control surface-mediated growth mechanisms with high spatial precision and reproducibility across macroscopic lengths. To this end we have recently demonstrated a simple route for the directed assembly of heteroepitaxial islands based on rudimentary metal patterning. Here we show that the same metal patterns on the silicon surface that lead to island ordering radically modify island morphology resulting in shapes such as nanorods and truncated pyramids that are set by the choices of metal species and substrate orientation. These effects reflect a remarkable combination of metal-mediated growth phenomena that may be exploited to tailor the functionality of island arrays.
Reliable Local Strain Characterization on Si/SiGe Structures in Biaxial Tension
Authors: Zhao Wenjun , Duscher Gerd , Zikry Mohammed A. , Rozgonyi George 
Published: April 2011

ABSTRACTThe strain in the strained Si layer on a blanket strained Si/SiGe structure could not be determined with only convergent beam electron diffraction to high order Laue zone (HOLZ) line splitting. Combined with CBED and finite element calculations, we quantified the deformation field from HOLZ line splitting and demonstrated a procedure to determine the initial strain in the strained Si layer. Our results also gave us insights in strain relaxation in a TEM sample. The CBED technique combined with FE modeling has the potential for initial strain measurements on new generation short channel CMOS technology nodes.
Optical Properties of Multiple, Delta-doped Si:B/Si Layers
Authors: Chang Han-Yun , Lee Eun-Kyu , Kamenev Boris V. , Baribeau Jean-Marc , Lockwood David J. , Tsybeskov Leonid 
Published: April 2011

ABSTRACTReliable fabrication of high-speed, delta-doped transistors and better understanding of two-dimensional metal-insulator transitions can be achieved using silicon molecular beam epitaxy (MBE). However, this fabrication technique should be performed with care, avoiding dopant segregation on epitaxial Si surfaces and improving the doping efficiency. Here we report comprehensive structural and optical investigations of MBE-grown Si/delta-doped Si:B multilayer structures. Measurements of Auger electron spectroscopy, Raman scattering, optical reflection and photoluminescence are performed. Our results indicate nearly metallic conductivity at room temperature with metal-insulator phase transition near T ∼100 K. In contrast to recently reported data, no enhancement of photoluminescence at room temperature is found. Occasionally, a few samples in specific areas exhibit strong photoluminescence at 1.4-1.6 micron attributed to structural defects, most likely due to B segregation.
Characterization of Coherent Si1−xGex Island Superlattices on (100) Si
Authors: Baribeau Jean-Marc , Wu Xiaohua , Picard Marie-Josée , Lockwood David J. 
Published: April 2011

ABSTRACTWe examine the nanostructural properties of Si/Si1−xGex island superlattices with 0.37 < x < 0.56 grown at 620-640 °C by molecular beam epitaxy. Analytical transmission electron microscopy (TEM) shows that during growth Ge atoms migrate towards the center of the large islands to maintain epitaxial growth and that the most regular structures are obtained at higher Ge composition when the built-in strain is also higher. High-resolution x-ray reciprocal space mapping shows that these heterostructures remain pseudomorphic and that the undulations are aligned along [010] directions and exhibit a long-range coherence and vertical correlation as revealed by the presence of strong satellites in a wave vector direction parallel to the surface. Raman spectra of these samples exhibit the usual Ge-Ge, Si-Ge and Si-Si vibrational modes. When compared with planar Si/Si1−xGex superlattices the Ge-Ge and Si-Ge Raman peaks are shifted to lower frequencies indicating an average alloy composition that is approximately x = 0.1 less than the nominal values, which is in general agreement with analytical TEM.
Bright Contrast Imaging of Carbon Nanofiber-Substrate Interface using Scanning Electron Microscopy
Authors: Suzuki Makoto , Ominami Yusuke , Ngo Quoc , Yamada Toshishige , Roth Bill , Betts Mark , Cassell Alan M. , Li Jun , Yang Cary Y. 
Published: April 2011

ABSTRACTScanning electron microscopy (SEM) for imaging the interface between carbon nanofibers (CNFs) and the underlying substrate is presented. By irradiating the electron beam perpendicular to the substrate, bright contrast is observed at the region where a small gap exists between the CNF and substrate. The energy-diameter diagram for the observation of the bright contrast is derived, which can be understood by using the theory of electron penetration into solid. Monte Carlo simulation is performed to reproduce the experimental observation based on our model, and the contrast sensitivity to the gap height is discussed.
Carrier Doping of Silicon Nanowires Synthesized by Laser Ablation
Authors: Fukata Naoki , Okada Naoya , Matsushita Satoshi , Tsurui Takao , Ito Shun , Chen Jun , Sekiguchi Takashi , Uchida Noriyuki , Murakami Kouichi 
Published: April 2011

ABSTRACTBoron (B) doped silicon nanowires (SiNWs) were synthesized by laser ablation. Local vibrational modes of B in SiNWs were observed by micro-Raman scattering measurements at room temperature. Broadening due to a coupling between the discrete optical phonon and a continuum of interband hole excitations was also observed in the Si optical phonon peak. This is called Fano broadening. These results prove that B atoms were doped in substitutional sites of crystalline Si core of SiNWs during laser ablation.
Influence of Chemical Dopant Technique to Reduce Schottky Barriers of Pd-Contacted CNTFETs
Authors: Casterman Damien , De Souza Merlyne Maria 
Published: April 2011

ABSTRACTThe role of the p-type chemical dopant, SbCl6, on Palladium (Pd)-contacted carbon nanotube field effect transistors (CNTFETs) is investigated using ab initio calculations. The interaction of SbCl6 with Pd leads to the chemisorption of one chlorine atom (Cl) which separates off from the rest of the molecule leaving behind a rehybridized SbCl5 molecule. This interaction increases the local workfunction by 0.08 eV. The interaction of the molecule with the carbon nanotube (CNT) itself results in the physisorption of SbCl6 onto CNT. The SbCl6 is found to degenerately dope CNT p-type and shifts the local potential by 0.29 eV. These barriers are useful for modelling of transport of Schottky barrier CNTFETs.
SiC Nanowires by Silicon Carburization
Authors: Tsakalakos Loucas , Fronheiser Jody , Rowland Larry , Rahmane Mohamed , Larsen Michael , Gao Yan 
Published: April 2011

ABSTRACTPolycrystalline SiC nanowires and composite Si nanowire-SiC nanograin structures have been synthesized using a combined catalytic chemical vapor deposition and carburization method. Si nanowires are grown at low temperature (550-650 C) and subsequently carburized at 1100-1200 C in a methane/hydrogen or propane/hydrogen environment. Thermochemical calculations showed that the Si carburization is thermodynamically favorable over a wide tempareture range, whereas our studies showed that the Si nanowire carburization is kinetically limited below ∼1100 °C. Partially carburized nanowires contained distinct SiC nanosized grains on the Si nanowire surface, whereas fully carburized nanowires were polycrystalline 3C SiC with grain sizes of ∼ 50-100 nm.
Nonaqueous Viscous Electrolytes for Growth of Anodic Titania Nanotubes
Authors: Macak Jan M. , Albu Sergiu P. , Schmuki Patrik 
Published: April 2011

ABSTRACTThe present work compares two different organic electrolytes (glycerol and ethylene glycol) for the growth of self-organized TiO2 nanotubes by anodic oxidation of Ti. In both electrolytes these self-organized layers of TiO2 nanotubes can be grown to considerable thickness (several 10 μm). It is found that except for the detailed electrochemical conditions also the water content has a dramatic influence on the tube dimensions, mainly length and tube morphology. The best result in terms of length is achieved in “water-free” electrolytes.
Effects of Metal Nanocrystals and Traps in Tunneling Rate Measurements in Metal Nanocrystal Based Carbon Nanotube Memory
Authors: Ganguly Udayan , Hou Tuo-Hung , Kan Edwin 
Published: April 2011

ABSTRACTThe metal nanocrystal (NC) based carbon nanotube (CNT) memory device has been probed with tunneling rate measurements. Firstly, tunneling behavior at two temperatures (300K and 10K) is reported here to demonstrate the distinct charge tunneling behavior for traps versus NCs and understand their relative contributions to program operations. Low temperature measurements show clear differentiation for two regimes of quantum transport. The FN tunneling regime exhibits strong bias dependence and dominates at high electric fields producing larger tunneling rates than the direct tunneling regime. In comparison to traps, the metal NCs repel potential contours and hence produce higher electric fields that enhance tunneling. The FN tunneling diminishes when the charging of the nanocrystal or traps decreases (relaxes) the electric field in the tunnel dielectric (TD) enough for the low field direct tunneling to dominate. The direct tunneling occurs at low fields, and is less sensitive to electric fields. The NCs demonstrate faster tunneling which can be ascribed to their large tunneling cross-section compared to traps. This is despite the relative proximity of traps to the channel in our structure. Secondly, the tunneling rates for two different TDs of similar EOT (under linear approximation) have been characterized and compared. They are a homogenous evaporated SiO2 and layered dielectric consisting of an evaporated SiO2 and ALD Al2O3 stack. While the evaporated SiO2 based TD demonstrates the distinct NC versus trap tunnel rate performance, the layered TD demonstrates stronger resistance to tunneling to the NCs. This result is consistent with the low tunneling rates demonstrated in Al2O3 elsewhere. Finally, the program performance of the NC-CNT memory device is evaluated as 0.5 V threshold voltage (VT) shift for a charging pulse of 9V and 100 μs. Combining with previous results, this indicates that NC-CNT memory is a promising candidate for low voltage, fast, multi-level cell (MLC) operation with sub-lithographic (self-assembled) features for sub 30 nm FLASH memory node. From the device physics perspective, these measurements may serve as the calibration and validation for advanced tunneling calculations and device modeling for promising nanoscale charge-based non-volatile memories.
Self-Assembled Conductive Network of Carbon Nanotubes in Polyaniline Forming Potential Nanocomposites
Authors: Gupta Sanju , Kandagor V , Hauge R. , Ding Y , Patel R. J. 
Published: April 2011

ABSTRACTCarbon nanotubes (CNTs) are of great interest because of several unsurpassable physical (mechanical, electrical, thermal, and chemical) properties. Especially their large elastic modulus and breaking strength make them highly attractive for their use as reinforced agents in forming a new class of multifunctional advanced materials - onanocomposites, in addition to high conductivity (either in semiconducting or metallic regimes) achieved through lower percolation thresholds for several electronic applications. Among the known conducting polymers, polyaniline (PANI) has a high potential due to its ease of synthesis, excellent environmental, and thermal stability and reversible control of its electrical/electronic properties. In this work, PANI-single-/multiwalled NTs composites films containing different nanotube content of both kinds were synthesized by spin-cast preceded by ultrasonic mixing of the constituents. They were characterized using complementary techniques including scanning electron microscopy, X-ray diffraction, infrared and Raman spectroscopy, and conductivity revealing their microscopic structure and physical properties thus helping in establishing process-structure-property correlations. The present work will discuss some of these findings in terms of a) self-alignment of nanotubes in conducting polymer b) their optical and electrical properties, and c) their design with a view to electronic and sensor applications, all ascribed due to long range π-π interaction between the constituents.
Study on the Synthesis of CNTs and the Fabrication of CNTs-Based MEA for DMFC Application
Authors: Su Chun-Hsi , Lin Chii-Ruey , Hung Hsin-Chin 
Published: April 2011

ABSTRACTA fuel cell (FC) generates electricity by chemical reactions. The catalyst dispersion in membrane electrode assembly (MEA) of FC is a crucial factor to affect the performance of the cell. A novel grafting method is adopted in this study to grow secondary carbon nano-tubes (CNTs) on a substrate comprised of primary CNTs, in order to form branchy CNTs with higher specific surface area (SSA). The as-obtained branchy CNTs are then used as catalyst, Pt, carriers in the MEA of direct methanol fuel cell (DMFC). A self-assembled DMFC of air-breathing type with active MEA area of 2 × 2 cm2 is used in this study as the standard FC for the electrical performance test. The peak power of DMFC comprised of an MEA with sole primary CNTs is 0.002 watts at 0.15 V. Such peak power can be increased up to 0.01 watts at 0.4 V for the replaced MEA with new branchy CNTs. The open circuit voltages (OCVs) are 0.4 V and 0.6 V for DMFCs with MEAs of sole primary CNTs and branchy CNTs, respectively. Furthermore, the patterns of CNTs was designed to provide micro-channels of fuel. The pattern growth of CNTs have been fabricated by selective area growth method in this research.
Carbon Nanotube-Based Fluid Flow/Shear Sensors
Authors: Ni Chi-Nung , Deck Christian P. , Vecchio Kenneth S , Bandaru Prabhakar R 
Published: April 2011

ABSTRACTThe response of vertically oriented multi-walled nanotubes (MWNTs) to fluid flows forms a basis for monitoring shear forces at the nanoscale. We report on the modulation of polarized light transmission through a MWNT mat, as a function of the nanotube axis relative to the laser polarization. Nanotubes are deflected under fluid flow, with fluid pressures corresponding to pico-Newton range forces. This deflection is measured as a function of transmitted laser light intensity. While the response of the CNTs to the flows could be modeled through standard elastic beam deflection theory, their recovery, after the force removal, invokes viscoelastic behavior due to CNT disentanglement. The fluid flow direction, as well as its pressure, can also be determined by monitoring the change in transmitted laser polarization.
O2 Plasma Treatment of Al Layer on Metal Anode to Improve the Performance of Organic Light-Emitting Devices
Authors: Lee Su Hwan , Shin Dong-Won , Kim Sung-Jun , Kang Yoon Ho , Lee Gon-Sub , Park Jea-gun 
Published: April 2011

ABSTRACTA gold and aluminum layer was investigated as an anode for organic light-emitting devices (OLEDs). By pretreating the ultrathin aluminum layer in an oxygen (O2) plasma, the hole injection from the metal anode to the organic layer was greatly enhanced. The fabricated OLEDs demonstrated improved current density and luminance characteristics as compared with other devices using a gold anode and an aluminum layer not treated with an oxygen plasma.