bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth of Carbon Nanofibers on Electroless Ni-P Alloy Catalyst
Authors: Tsai T.K. , Liu W.L. , Hsieh S.H. , Chen W.J. 
Published: April 2011

ABSTRATECarbon nanotubes (CNTs) were grown by electroless Ni-P plated on silicon substrate in a microwave heating chemical vapor deposition (CVD) system with methane gas at 700 °C. The CNTs grown on Ni–P catalyst showed random orientation and small diameter around 15–30 nm. Field emission test results indicated that the Ni–P catalyzed-CNTs exhibited excellent field emission properties. The turn-on field was about 0.56 V/μm with an emission current density 10 μA/cm2 and the threshold field was 4.4 V/μm with an emission current density 10 mA/cm2. These excellent field emission properties may be attributed to the random orientation and small diameter of CNTs.
Size Reduction of Clay Particles in Nanometer Dimensions
Authors: Mani Gopinath , Fan Qinguo , Ugbolue Samuel C. , Eiff Isabelle M. 
Published: April 2011

ABSTRACTThis research work focuses on combining ball milling and ultrasonication to produce nano-size clay particles. Our work also emphasizes on increasing the specific surface area of montmorillonite clay particles by reducing the particle size to nanometer dimensions. We have characterized the as-received clay particles by using particle size analysis based on laser diffraction and found that the size of the clay particles is not consistent and the particle size distribution is very broad. However, after the unique treatment and processing, the clay particles were obtained in nanometer dimensions with narrowed particle size distribution.
Effect of Solid-Solution W Addition on the Nanostructure of Electrodeposited Ni
Authors: Iwasaki Hajime , Higashi Kenji , Nieh T. G. 
Published: April 2011

ABSTRACTElectrodeposition method was employed to produce freestanding Ni-W alloy foils. The foils consist of nanograins. The structure of the foil, e.g. texture, grain morphology, size distribution, and the nature of grain boundaries, were characterized using X-ray diffraction and high-resolution electron microscopy. The deposited foils exhibit an equiaxed nanocrystalline structure having a grain size value of about 6 nm. Two types of grain boundary structure were observed. One type of grain boundary is essentially one atomic layer thin and another type consists of a structureless layer of about 0.5–1 nm in thickness. Angular dark field (Z-contrast) image of the deposited foils showed an inhomogeneous distribution of W solutes. In some local regions, the W content actually exceeds the equilibrium solid solution limit. Many grain boundaries with a structureless layer of about 0.5–1 nm are probably a result of local supersaturation of W.
Hydrogen Stabilization of {111} Nanodiamond
Authors: Barnard A.S. , Marks N.A. , Russo S.P. , Snook I.K. 
Published: April 2011

ABSTRACTPresented here are results of ab initio Density Functional Theory (DFT) structural relaxations performed on dehydrogenated and monohydrogenated nanocrystalline diamond structures of octahedral {111} and cuboctahedral morphologies, up to approximately 2nm in diameter. Our results in this size range show a transition of dehydrogenated nanodiamond clusters into carbon onion-like structures, with preferential exfoliation of the C(111) surfaces, in agreement with experimental observations. However, we have found that this transition may be prevented by hydrogenation of the surfaces. Bonding between atoms in the surface layers of the relaxed structures, and interlayer bonding has been investigated using Wannier functions.
Biodegradable Polyester / Layered Silicate Nanocomposites
Authors: Maiti Pralay , Batt Carl A. , Giannelis Emmanuel P. 
Published: April 2011

ABSTRACTNanocomposites of α-hydroxy polyester, polylactide (PLA) and β-hydroxy polyester, polyhydroxybutyrate (PHB) with layered silicates have been successfully prepared by melt extrusion of PLA and PHB with organically modified montmorillonite (MMT) and fluoromica. The mechanical properties of the nanocomposites are improved compared to the neat polymers. Storage modulus increase up to 40% compared with the pure polymers by adding only 2–3 wt% nanoclay. Biodegradation can be controlled by the choice of the nanoclay used.
Mechanical Behavior of Polymer Nanocomposites: a discrete simulation approach
Authors: Chabert E. , Gauthier C. , Dendievel R. , Chazeau L. , Cavaillé J.-Y. 
Published: April 2011

ABSTRACTThis work reports the dynamic mechanical characterization of nanocomposites based on a poly(butyl acrylate) matrix filled with spherical particles of either polystyrene or silica both of diameter around 100 nm. A discrete numerical simulation, taking into account the microstructure and the nature of contact between reinforcing particles has been developed. This simulation enables to quantify the effect of interactions between filler particles on the elastic modulus, and in a more general sense, to clarify the concept of mechanical percolation. It gives results in very good agreement with experimental data.
Modeling mechanical properties of carbon molecular clusters and carbon nanostructural materials
Authors: Levin Vadim M. , Petronyuk Julia S. , Ponomareva Inna V. 
Published: April 2011

ABSTRACTThe concept of 2D elasticity of a graphene sheet together with the idea of stiffness of a single sp3 bond have been applied to theoretical evaluating elastic properties of diverse carbon states. 2D elastic moduli have been extracted from data on elastic moduli of crystalline graphite. Stiffness of the sp3 bond has been estimated from data on the elastic modulus of diamond. Efficiency of Van-der-Waals interaction has been taken from the elastic modulus C33 of crystalline graphite. Characteristics of single fullerene deformability have been computed by the molecular dynamics method. Theoretical estimations have been performed for single molecular clusters, pristine fullerite, HPHT phases of polymerized C60, etc. The estimations are in good agreement with experimental data on elastic properties and nanoscale structure of carbon states. The approach is effective for establishing interrelation between nanostructure and elastic properties, for prediction and classification of nanostructure in novel carbon materials.
Anomalous X-ray Scattering for Determination of Nanostructured Alloy Formation and Site-specific Chemistry of Bragg Peak
Authors: Chow G.M. 
Published: April 2011

ABSTRACTThe properties of nanostructured films can be tailored by many factors such as composition, structure, preferred orientation, microstructure, interphase interface and grain boundaries. Compositional control of magnetic properties of recording media depends on the miscibility of constituent elements. However, for nanostructured materials with a large surface-to-volume ratio of atoms, the miscibility at the nanoscale may not necessarily follow the prediction of conventional phase diagram that does not consider the effects of surface and interface. This limitation further complicates the prediction of phase separation at grain boundaries and interphase interface. Using anomalous x-ray scattering, the alloying and composition of a specific long range order of textured nanostructured films has been investigated. Such information may not be readily available from conventional characterization techniques.
Mesoscale Thin Film Actuator for Promoting Fluid Motion in Microfluidic and Nanofluidic Channels
Authors: Sadler Daniel J. , Singh Gaurav , Zenhausern Frederic , Saraf Ravi F. 
Published: April 2011

ABSTRACTMicrofluidic and nanofluidic devices often require actuators to induce fluid motion for applications such as pumping and mixing in small channels. Mixing, for instance, is important in systems where channel or chamber dimensions are on the order of 100 μm or larger as diffusive mixing can be prohibitively slow at these dimensions. In this work, a new mesoscale thin film polymer electromechanical actuator is introduced for use in the aforementioned applications. Unlike inorganic piezoelectric actuators, the devices based on these materials will be relatively easy to fabricate involving no high temperature processing, crystal growth, or microlithography. Fabrication of an array of actuators is simply achieved by spin casting the polymer over top of lithographically patterned gold electrodes at a thickness of less than 50 nm. This simple process enables a microfluidic device based on these actuators to be an integral part of a microfluidic channel rather than a separate unit operation. Depending on the application, the actuator array can be designed and controlled for random perturbations of the fluid flow field as required for mixing or for systematic actuation as required for pumping. These thin-film mesoscale actuators have been characterized and show extremely favorable properties such as a high electrostrictive response (compared to none in the bulk) and a frequency response of up to 50 kHz. In addition, finite element simulations show feasibility of these actuators for use in microfluidic mixing applications.
Vibrating RF MEMS for Low Power Communications
Authors: Nguyen Clark T.-C. 
Published: April 2011

ABSTRACTMicromechanical communication circuits fabricated via IC-compatible MEMS technologies and capable of low-loss filtering, mixing, switching, and frequency generation, are described with the intent to miniaturize wireless transceivers. Possible transceiver front-end architectures are then presented that use these micromechanical circuits in large quantities to substantially reduce power consumption. Technologies that integrate MEMS and transistor circuits into single-chip systems are then reviewed with an eye towards the possibility of single-chip communication transceivers.
Characterisation of the mechanical properties of MEMS devices using nanoscale techniques
Authors: Randall Nicholas X. , Soden Richard A. J. 
Published: April 2011

ABSTRACTThis paper focuses on recent developments in the localised characterisation of the mechanical properties of Microsystems and MEMS devices and structures. Conventional indentation techniques provide a highly powerful method for measuring the load and depth response of bulk and coated materials, but can also be used to measure the mechanical properties of very small micro-machined silicon structures. Beam structures, such as are used for accelerometers, need to be characterised in terms of the number of cycles to failure, the spring constant or the energy required to bend the beam by a required amount. Such localised testing needs to be adapted to work at various distances from the origin of the beam with a positioning accuracy of less than a micron. Initial studies have proved to be highly repeatable. A range of examples is presented which covers a range of application areas, including accelerometer beam structures, microswitches and printer head structures. The basic instrumental concepts are explained together with the modifications required for testing small structures in a localised way.
Development of Fatigue Pre-Cracking Method into Micro-Sized Specimens for Measuring Fracture Toughness
Authors: Takashima K. , Koyama S. , Nakai K. , Higo Y. 
Published: April 2011

ABSTRACTIn our previous investigations [1, 2], we have demonstrated that the introduction of fatigue pre-crack ahead of a notch is required to measure reliable fracture toughness values even for micro-sized specimens. However, it is rather difficult to introduce a fatigue pre-crack into a micro-sized specimen as once a fatigue crack starts to grow then the fatigue fracture occurs within one thousand cycles and this makes it extremely difficult to control fatigue crack length. Therefore, a new fatigue pre-cracking method is required for measuring fracture toughness. In this investigation, a new fatigue pre-cracking method has been proposed for micro-sized specimens and fracture toughness tests were carried out for the micro-sized specimens with fatigue pre-crack. Micro-cantilever beam type specimens with dimensions of 10 × 10 × 50 μm3 were prepared from an electroless deposited Ni-P amorphous alloy thin film and notches were introduced by focused ion beam machining. Fatigue pre-cracks were introduced ahead of the notches by far-field cyclic compression method using a mechanical testing machine for micro-sized specimens (MFT2000). Fracture tests were also carried out using the testing machine. Fatigue pre-cracks with length of 0.2 μm were confirmed on the fracture surfaces ahead of the notches in the far-field cyclically compressed specimens. This indicates that the fatigue pre-cracking method developed in this investigation is promising for measuring accurate fracture toughness for micro-sized specimens for MEMS applications.
Selective Titanium Oxide Formation Using Electron-beam Induced Carbon Deposition Technique
Authors: Djenizian Thierry , Macak Jan , Schmuki Patrik 
Published: April 2011

ABSTRACTThe present work describes the selective titanium oxide formation based on electron-beam (e-beam) induced carbon deposition used as a mask against chemical dissolution. Under ideal conditions the C-deposits act as a negative resist to hinder the titanium oxide dissolution at e-beam treated locations. Carbon patterns were written in a scanning electron microscope at different electron doses on titanium oxide electrochemically grown in 1 M NaOH by potentiostatic experiments. Subsequently, the untreated areas were chemically removed in 0.5 % HF leaving the C-protected TiO2 patterns at the Ti surface. The selectivity of the technique depends on several factors such as the electron dose during masking and the chemical parameters. Under ideal conditions, it is demonstrated that direct patterning of surfaces as well as the fabrication of microstructures can be achieved using such technique.
Hybrid Integration of III-V Optoelectronic Devices on Si Platform Using BCB
Authors: Katsnelson Alex , Tokranov Vadim , Yakimov Michael , Lamberti Matthew , Oktyabrsky Serge 
Published: April 2011

ABSTRACTIntegration of dense arrays of high frequency III-V photoemitters and photodetectors with Si platform is one of the challenging tasks for realization of novel chip-level optical interconnects. These interconnects require the resolution of numerous problems of compatibility of materials. Comparison of monolithic and hybrid integration technologies highlights the advantages of hybrid approaches for emitters highly sensitive to growth defects. A novel protocol for fabrication of III-V optoelectronic components on a Si platform is proposed. Reversed vertical cavity surface emitting laser (VCSEL) structures were grown homoepitaxialy by MBE on a GaAs substrate, and then bonded to a Si wafer using a benzocyclobutene (BCB) polymer. The GaAs substrate was subsequently removed by selective etching down to an AlAs etch stop layer. This reduces thermal stresses in order to enhance the optoelectronic device performance and increase lifetime. A 10 μm-thick high frequency VCSEL with coplanar metallization is processed on Si with PMGI reflow planarization. Electro-luminescence spectrum, I-V and P-T characteristics were measured and compared with a reference structure. It was found that measured thermal resistance is about five times higher than for devices on a host GaAs wafer.
Aluminum Nitride Chip Carrier for Micro-electro-mechanical Sensor Applications
Authors: Marinis T. F. , Soucy J. W. 
Published: April 2011

ABSTRACTA commercially fabricated aluminum nitride chip carrier was evaluated for packaging various types of MEMS inertial sensors. They were successfully assembled and vacuum-sealed within AlN chip carriers and their pressures have remained stable for over one year. Aging tests were conducted under electrical bias at 85°C and 85 %RH. The leakage currents were not as stable as those measured in alumina chip carriers and post test inspection of the AlN parts revealed etching of the ceramic between conductors.
Process Development and Integration of Piezoelectric Aluminum Nitride Thin-Film for RF MEMS Applications
Authors: Sharma Rajnish K. , Ning Jiang , Hanhua Feng , Gopalakrishnan R. 
Published: April 2011

ABSTRACTThe aluminum nitride (AlN) process was successfully developed for as high frequency thin-film for bulk acoustic resonator applications. Columnar AlN was deposited on p-type (100) silicon substrate at 300–500°C using pulse direct current (DC) sputtering technique. Argon to nitrogen ratio was optimized to achieve stoichiometry at higher deposition rates of about 1000 Å/min at 1–4 kW DC power. The XRD of as-deposited and annealed AlN film shows preferred (002) orientations. The dry etching process was developed and etching rate about 3200 Å/min was achieved using Cl based chemistry. Film composition analysis was done using AES technique and stoichiometry was achieved.
Fabrication of Micromachined Piezoelectric Diaphragm Pumps Actuated by Interdigitated Transducer Electrodes
Authors: Hong Eunki , Krishnaswamy S.V. , Braggins T. T. , Freidhoff C.B. , Trolier-McKinstry S. 
Published: April 2011

ABSTRACTMicromachined pump structures were fabricated using surface micromachining. The structures consisted of three or five connected chambers. Sequential actuation of the diaphragms on these chambers will yield peristaltic pumping. As the actuation material, lead zirconate titanate (PZT [53/47] ) thin films were employed and actuated by interdigitated transducer (IDT) electrodes. First, chambers and channels on the 4″ (100) silicon wafers were defined by reactive ion etching (RIE) and thermally oxidized. The etched structures were then filled with amorphous silicon. Low temperature (silicon) oxide (LTO) and PZT films were then deposited. The LTO and PZT layers act as passive and active layers in a piezoelectric unimorph, respectively. A ZrO2 layer was employed to prevent reaction between SiO2 and PZT layers. A Cr/Au electrode was evaporated on top of the PZT layer and patterned into ring-shaped IDT electrodes. Finally, a porthole at each end of the pump structures was defined by ion milling and the whole micropump structure was released by removing the sacrificial amorphous silicon using XeF2. Completely released 500 μm diameter pump structures were fabricated. The remanent polarizations of the PZT films on released diaphragms were ∼20 μC/cm2 and their coercive fields were ∼50 kV/cm. 500 μm diameter diaphragms were deflected as much as 2 μm with 120 V applied. The shape and behavior of the diaphragm deflection can be explained by considering both d31 and d33 piezoelectric coefficients of the PZT films.
Mechanical Properties of Ultrananocrystalline Diamond Thin Films for MEMS Applications
Authors: Espinosa H.D. , Peng B. , Kim K.-H. , Prorok B.C. , Moldovan N. , Xiao X.C. , Gerbi J.E. , Birrell J. , Auciello O. , Carlisle J.A. , Gruen D.M. , Mancini D.C. 
Published: April 2011

ABSTRACTMicrocantilever deflection and the membrane deflection experiment (MDE) were used to examine the elastic and fracture properties of ultrananocrystalline diamond (UNCD) thin films in relation to their application to microelectromechanical systems (MEMS). Freestanding microcantilevers and membranes were fabricated using standard MEMS fabrication techniques adapted to our UNCD film technology. Elastic moduli measured by both methods described above are in agreement, with the values being in the range 930 and 970 GPa with both techniques showing good reproducibility. The MDE test showed fracture strength to vary from 3.95 to 5.03 GPa when seeding was performed with ultrasonic agitation of nanosized particles.
Epitaxial silicon carbide simulations vs. experiments: etching, growth rates and aluminum/nitrogen doping
Authors: Mézière Jérôme , Blanquet Elisabeth , Pons Michel , Dedulle Jean-Marc , Ferret Pierre , Cioccio Léa Di , Billon Thierry 
Published: April 2011

ABSTRACTThis paper summarizes recent experimental and simulation results on etching, growth rates and aluminum/nitrogen incorporation in SiC epitaxial layers grown in a horizontal LPCVD hotwall reactor commercialized by the Epigress company. The combined use of modeling and experiments allows to identify and to quantify the main growth phenomena. In this paper, a chemistry model including surface deposition and hydrogen etching is first described. It is found that the contribution of the etching of the susceptor to the SiC growth is not negligible. A simple model is used to describe nitrogen incorporation.
Reconstruction and Epitaxial Adlayers on SiC Surfaces: Structural Significance for Technological Applications
Authors: Starke U. 
Published: April 2011

ABSTRACTStructure and composition are reviewed for different surface phases of SiC(0001) and SiC(0001). The chemistry of well ordered phases spans from Si rich to graphitic composition with the excess elements arranged in adlayers and/or large scale reconstruction patterns. On SiC(0001) the Si rich (3×3) surface allows for step flow growth of monocrystalline homoepitaxial layers due to an extremely efficient dangling bond saturation. Si rich preparation or oxidative treatment are used for a controlled evolution of different stacking sequences on the adatom phase on SiC(0001) and could be utilized for the development of polytype heterostructures. On SiC(0001) a (2×2) phase shows three-fold coordinated adatoms with a different surface stacking reflecting the different growth behaviour of this surface. An epitaxially well matching silicon oxide monolayer can be prepared on both surface orientations by using a hydrogen etching or plasma treatment promising to facilitate low defect oxide films for MOS devices.
Growth of Columnar SiC on Patterned Si Substrates by CVD
Authors: Nishino Shigehiro , Okui Yoichi , Tai Yuehai , Jacob Chacko 
Published: April 2011

ABSTRACTSingle crystalline 3C-SiC films have been grown on Si(111) substrate at 1200°C by conventional CVD process using HMDS (Hexamethyldisilane). Before columnar growth of SiC, columnar Si was made by depositing Au on Si(111) substrate as a solvent of VLS mechanism. Si growth was carried out by disproportional reaction in halide transport method. The columnar Si was produced on the patterned substrates. The columnar Si was covered by SiC. Needle like columns of SiC can be used for MEMS application such as micro-heat exchanger.
Characterization of Porous SiC Substrates and of the Epilayer Structures Grown on Them
Authors: Raghothamachar Balaji , Bai Jie , Vetter William M. , Gouma Perena , Dudley Michael , Mynbaeva Marina , Smith Matthew T. , Saddow Stephen E. 
Published: April 2011

ABSTRACTPorous 6H-SiC and 4H-SiC wafers formed by anodization have been characterized in this study prior to and following the CVD deposition of SiC epitaxial layers, using a combination of synchrotron white beam x-ray topography (SWBXT), SEM, TEM and optical microscopy. Under the high temperatures employed during epitaxial growth, a significant change in pore morphology occurs. While no evidence of reduced screw dislocation density in the epilayers is obtained, a small tilt of the epilayers with respect to the porous substrate observed on x-ray topographs could play a role in limiting penetration of defects from the substrate.
Spectroscopic Properties of Cubic SiC on Si
Authors: Feng Z. C. , Talwar D. N. , Ferguson I. 
Published: April 2011

ABSTRACTSpectroscopic studies are reported for cubic SiC grown on Si by chemical vapour deposition (CVD) manufacture technique. The UV excitation room temperature photoluminescence (PL)-Raman spectra exhibited 2.3 eV luminescence line due to RT recombination over the SiC indirect band gap. In addition to the optical phonons from cubic SiC we observed new Raman modes near 620 and 833 cm-1. A comprehensive analysis of the dynamical properties of defects using Green's function theory has suggested isolated impurity vibrations to be the possible origin for the additional phonons observed by Raman spectroscopy.