bluuebunny/crossref_metadata_2025_split huggingface dataset:
Indentation Response of Nanostructured Turfs
Authors: Zbib A. A. , Mesarovic S. Dj. , Bahr D. F. , Lilleodden E. T. , Jiao J. , McClain D. 
Published: April 2011

AbstractWhen grown via chemical vapor deposition carbon nanotubes (CNTs) may take on the form of a “turf”, consisting of many CNTs with a complex interconnectedness attached to an inflexible substrate. These turfs can be formed over large areas and with a range of heights (between 1 to 100 μm), and grown on photolithographically patterned catalysts to form different aspect ratios. This study focuses on the indentation and permanent deformation of CNT assemblages under applied contact loading. Nanoindentation was conducted on CNT turfs and the properties, nominally the turf's elastic modulus and hardness, were 14.9 MPa ± 5.7 MPa and 2 MPa respectively. The onset of permanent deformation during indentation occurred at applied stresses of 2.5 MPa. The turf's collective permanent deformation under applied compressive loading was also studied. A model predicting the buckling stress of CNT turfs is also described.
Microstructural Investigation of the Deformation Zone below Nano-Indents in Copper
Authors: Rester Martin , Motz Christian , Pippan Reinhard 
Published: April 2011

AbstractThe deformation zone below nanoindents in copper single crystals with an <110>{111} orientation is investigated. Using a focused ion beam (FIB) system, cross-sections through the center of the indents were fabricated and subsequently analyzed by means of electron backscatter diffraction (EBSD) technique. Additionally, cross-sectional TEM foils were prepared and examined. Due to changes in the crystal orientation around and beneath the indentations, the plastically deformed zone can be visualized and related to the measured hardness values. Furthermore, the hardness data were analyzed using the Nix-Gao model where a linear relationship was found for H2 vs. 1/hc, but with different slopes for large and shallow indentations. The measured orientation maps indicate that this behavior is presumably caused by a change in the deformation mechanism. On the basis of possible dislocation arrangements, two models are suggested and compared to the experimental findings. The model presented for large imprints is based on dislocation pile-ups similar to the Hall-Petch effect, while the model for shallow indentations uses far-reaching dislocation loops to accommodate the shape change of the imprint.
Measurement of Ultrathin Film Mechanical Properties by Integrated Nano-scratch/indentation Approach
Authors: Bastawros Ashraf , Che Wei , Chandra Abhijit 
Published: April 2011

AbstractThe thickness and property measurements of thin films on a substrate are crucial for a wide range of applications. Classical techniques have relied on various physical properties to identify film thickness, independent of its mechanical properties. Here, a new experimental technique is devised to evaluate the film thickness, its stiffness and its flow stress. The technique utilizes the variation of the measured apparent modulus of a ductile film on a substrate from a nano-indentation experiment, in conjunction with the measured normal and tangential forces and the scratch depth in a nano-scratch experiment. These combined measurements are calibrated through a simple statically admissible model to yield the unknown quantities. The measurements reasonably agree with the finite element predictions and are ascertained by XPS film thickness measurements. The technique is applied to study the formed oxide nano-layer during copper chemical mechanical planarization process.
Reverse Plasticity in Nanoindentation
Authors: Huang Yongjiang , Tjahyono Nursiani Indah , Shen Jun , Chiu Yu Lung 
Published: April 2011

AbstractThis paper summarises our recent cyclic nanoindentation experiment studies on a range of materials including single crystal and nanocrystalline copper, single crystal aluminium and bulk metallic glasses with different glass transition temperatures. The unloading and reloading processes of the nanoindentation curves have been analysed. The reverse plasticity will be discussed in the context of plastic deformation mechanisms involved. The effect of loading rates on the mechanical properties of materials upon cyclic loading will also be discussed.
Martensite Transition and Microscopic Magnetism of Epitaxial Ni2MnGa Films
Authors: Jakob Gerhard , Eichhorn Tobias , Kallmayer Michael , Elmers Hans-Joachim 
Published: April 2011

AbstractA magnetically induced shape memory effect in Ni2MnGa results in huge magnetostrictive effects of several percent. Using x-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD) we investigated element specific magnetic moments and electronic structure of single crystalline, (110) oriented Ni2MnGa films on a-plane Al2O3 substrates in the austenite and martensite state. The structural phase transition of the samples is evident from temperature dependent x-ray diffraction and magnetization measurements. The Ni XAS differ significantly for temperatures above and below the martensite transition in agreement with published ab-initio calculations. Using XAS in transmission geometry on our thin film samples we observe the corresponding reduction of the absorption feature as predicted by theoretical calculations. The XMCD analysis shows the orbital contribution of the Ni electrons to be responsible for the magnetic anisotropy.
Effect of Surface Oxide Layer on Mechanical Properties of Single Crystalline Silicon
Authors: Miyamoto Kenji , Sugano Koji , Tsuchiya Toshiyuki , Tabata Osamu 
Published: April 2011

AbstractFatigue fracture under cyclic loading of single crystal silicon (SCS) is concerned and fatigue properties and mechanism are investigated widely. Surface oxide is considered to have an important role on fatigue fractures. In this paper, the tensile testing of SCS whose surface was intentionally oxidized and the effect of the oxide thickness on the mechanical properties were reported. After fabrication of SCS specimens, they were oxidized in dry oxidization at 1100 ºC. Quasi-static tensile testing of SCS specimens with no, 100-nm-oxide, and 200-nm-oxide thick oxide was performed. As the results, the deviation in fracture strain was decreased by oxidation, and the fracture origin was observed to be the inner silicon part. These results might be caused by the decrease of surface roughness and defects formation by oxygen precipitation during thermal oxidation.
C-Axis Oriented ZnO Film by RF Sputtering and its Integration with MEMS Processing
Authors: Chandra Sudhir , Singh Ravindra 
Published: April 2011

AbstractIn the present work, we report a new fabrication process to integrate the “c-axis oriented” ZnO films with bulk-micromachined silicon diaphragms. ZnO films are very sensitive to the chemicals used in the micro-electro-mechanical systems (MEMS) fabrication process which include acids, bases and etchants of different material layers (e.g. SiO2, chromium, gold etc.). A Si3N4 layer is incorporated to protect the ZnO film from the etchants of chromium and gold used for patterning the electrodes. A mechanical jig is used for protecting the front side (ZnO film side) of the wafer from ethylenediamine pyrocatechol water (EPW) during the anisotropic etching of silicon. The resistivity measurement performed on the ZnO film integrated with micro-diaphragm shows the reliability of the fabrication process proposed in this work.
Compressive Stress Accumulation in Composite Nanoporous Gold and Silicone Bilayer Membranes: Underlying Mechanisms and Remedies
Authors: Seker Erkin , Huang Ling , Begley Matthew R. , Bart-Smith Hilary , Kelly Robert G. , Zangari Giovanni , Reed Michael L. , Utz Marcel 
Published: April 2011

AbstractThis paper outlines a simple method to fabricate a bilayer membrane consisting of a thin nanoporous gold layer infused with uncured polydimethylsiloxane. The fabrication technique offers excellent adhesion due to mechanical interlocking between porous layer and elastomer, and excellent electrical conductivity up to 25% strain, despite a very low effective elastic modulus (∼1.35 MPa) due to cracks in the embedded gold layer. Initially freestanding circular membranes displayed significant out of plane buckling, and created difficulties in extraction of membrane mechanical properties. The underlying mechanisms of compressive stress accumulation that lead to membrane buckling and remedies to prevent it are discussed.
Micro-Topography Enhances Directional Myogenic Differentiation of Skeletal Precursor Cells
Authors: Zhao Yi 
Published: April 2011

AbstractSkeletal muscle tissues were constructed using an in vitro model, by differentiating skeletal myoblasts using an array of linear microstructures with the medium aspect ratios. The adaptation of skeletal myoblasts has been characterized with immunoflurescence microscopy during cell proliferation and differentiation. In particular, the dependence of the alignment efficiency on the dimensions of the microstructures was studied. The morphology difference of the myotubes in the three-dimensional tissues was reported. This paper holds the promise of efficient on-chip fabrication of skeletal muscle tissues and has an important implication in direct muscle repair and muscular mechanics.
Relative Resistance Chemical Sensors Built on Microhotplate Platforms
Authors: Hertz Joshua L. , Montgomery Christopher B. , Lahr David L. , Semancik Steve 
Published: April 2011

AbstractThe selectivity, sensitivity, and speed of metal oxide conductometric chemical sensors can be improved by integrating them onto micromachined, thermally-controlled platforms (i.e., microhotplates). The improvements largely arise from the richness of signal inherent in arrays of multiple sensing materials and the ability to rapidly pulse and collect data at multiple temperatures. Unfortunately, like their macroscopic counterparts, these sensors can suffer from a lack of repeatability from sample-to-sample and even run-to-run. Here we report on a method to reduce signal drift and increase repeatability that is easily integrated with microhotplate chemical sensors. The method involves passivating one of a pair of identically-formed sensors by coating it with a highly electrically resistive and chemically impermeable film. Relative resistance measurements between the active and passive members of a pair then provide a signal that is reasonably constant over time despite electrical, thermal and gas flow rate fluctuations. Common modes of signal drift, such as microstructural changes within the sensing film, are also removed. The method is demonstrated using SnO2 and TiO2 microhotplate gas sensors, with a thin Al2O3 film forming the passivation layer. It is shown that methanol and acetone at concentrations of 1 µmol/mol, and possibly lower, are sensed with high reproducibility.
Fabrication of C54-TiSi2 Thin Films Using Cathodic Arc Deposition and Rapid Thermal Annealing
Authors: Xia Hui , Knudsen William R. , Bergstrom Paul L. 
Published: April 2011

AbstractDue to its low electrical resistivity and high thermal stability, C54-TiSi2 thin films can be used in some MEMS application, such as RF MEMS, to reduce RC delay and improve dynamic performance. In this paper, TiSi2 thin films have been prepared for the first time by using cathodic arc deposition to study the impact of energetic ion bombardment on the film microstructure and subsequent C49-C54 phase transformation during annealing. TiSi2 compound was used as the cathode and a substrate bias was varied to control kinetic energy of the ions during the film growth. Rutherford backscattering spectrometry and transmission electron microscopy were utilized to characterize the film composition and microstructure. The composition of the resultant TiSix thin films varies from x=2.4 to x=1.4 when the substrate bias was varied from floating to –200V. The as-deposited TiSix films are amorphous under no substrate heating and a phase separation at nano scale with inhomogeneous distribution of Ti and Si atoms was observed within the amorphous phase. Si atoms are seen to segregate on the boundary of Ti-rich domains and the domain size increased with the substrate bias. For a 90nm-thick TiSi2 film deposited on a SiO2/Si substrate, kinetics of the C49-C54 phase transformation was studied by measuring the change of film resistivity upon rapid thermal annealing. It was found that the C49-C54 phase transition temperature is higher (>900°C) for the arc-deposited TiSi2 thin films compared to evaporated and sputtered films and the activation energy for the transformation was calculated to be 6.1±0.2eV.
Compressive magnetostriction of FeSm alloy film
Authors: Nakano Ryo , Matsumura Yoshihito , Nishi Yoshitake 
Published: April 2011

AbstractThe compressive magnetostriction values of Fe2.4Sm alloy thin film prepared on silicon, copper and titanium substrates (300μm thickness) by direct current magnetron sputtering process were investigated. When the residual gas pressure before argon sputtering and the sputtering pressure of argon gas (5 N) were below 3.2×10−4 Pa and 2.0×10−1 Pa, respectively, the thickness of the Fe2.4Sm films deposited was about 3 μm. Compressive magnetostriction of Fe2.4Sm alloy film on titanium sheet generates the large bending motion, rather than those on silicon wafer and copper substrates. The high magnetostrictive susceptibility of the films was observed at low magnetic field.
Nature-Inspired Microfluidic Manipulation Using Magnetic Actuators
Authors: Khaderi S. N. , Ioan D. , den Toonder J. M. J. , Onck P. R. 
Published: April 2011

AbstractMagnetically actuated micro-actuators are proposed to propel and manipulate fluid in micro-channels. As the fluid flows at low Reynolds number in such systems, the actuator should move in an asymmetric manner. The proposed actuators are polymer films with embedded magnetic particles, which are actuated by an external magnetic field. Based on the nature of the particles, the films can be either ferromagnetic or super-paramagnetic. We have identified four configurations in which the actuator exhibits an asymmetric motion.
Phonon Interaction in InGaAs/GaAs Quantum Dots
Authors: Werner Stefan , Zimmer Patrick , Strittmatter André , Hoffmann Axel 
Published: April 2011

ABSTRACTThe carrier-phonon interaction in self-organized In(Ga)As/GaAs quantum dots is investigated under resonant excitation of the ground-state transition. Different phonon-coupled processes are observed. The distinction between Raman scattering and hot-luminescence process has been resolved by time-dependent photoluminescence measurements. The quantum dot LO (33.8 meV) as well as an interface (36.5 meV) phonon mode is observed by resonant Raman scattering. For the QD LO phonon mode, a very short radiative lifetime of 10 ps was found.
Fabrication of SERS Active Substrates by Nanoimprint Lithography
Authors: Li Kebin , Cui Bo , Clime Liviu , Veres Teodor 
Published: April 2011

ABSTRACTA method for low-cost fabrication of SERS substrates in rapid and reproducible way based on nanoimprint lithography (NIL) method has been developed. The SERS enhancement for detection of Rhodamine 6G molecules is demonstrated on two model nanostructures comprising either Au nano-crescents or Ag nano-wells fabricated by this method. Numerical simulations based on discrete dipole approximation (DDA) method show that the observed enhancement of the SERS signal for the given geometries originates in hot-spots localized at the tips of the nanocrescent. For the nanowell, the hotspots are mainly localized inside the cavity, on the side of the nanodonut, or at the edge of the bottom nanodisc when it is excited by a laser at the wavelength of 785 nm.
VUV-photon Induced Formation of Hydrophilic and Hydrophobic Micro Domains Structure on Intraocular Lens Surface for Blocking after Cataract
Authors: Sato Yuji , Kawai Kenji , Sasoh Mikio , Ozaki Hiroaki , Ohki Takeo , Shiota Hiroshi , Murahara Masataka 
Published: April 2011

ABSTRACTA micro domain structure, which hydrophilic and hydrophobic groups were arrayed alternately, was formed on the surface of an intraocular lens [IOL] by using ultra violet rays [VUV]. With this technique, the IOL that is free from fibrin has been developed. In order to substitute the hydrophilic groups in matrix-form on the surface, an ArF laser light was then irradiated on the hydrophobic surface in the presence of water for the −OH groups, through the 50-micrometer dot-patterned reticle. With this selective photochemical surface modification, the hydrophilic and hydrophobic groups were arrayed alternately on the sample surface. The modified IOL was soaked in 0.1-wt % fibrin solutions, and the fibrin-sticking rate was measured by using an infrared spectroscopy [FT-IR]. It results that the absorption coefficient of amide band reached to 0.0006, decreasing to one-six of non-treatment sample's.
Self-Organization and Nanocluster Formation Processes in Nonlinear Molecular Chains
Authors: Tereshko I. , Abidzina V. , Elkin I. , Kalinowskaya N. , Melnikau I. 
Published: April 2011

ABSTRACTThe goal of this work is to investigate self-organization processes in molecular chains. Computer simulation has been performed by means of a molecular dynamics method. Morse potential was chosen as the potential of atomic interaction. Molecular chains were exposed to low-energy ion impact by two means: mono beam and plasma treatment. The amount of the energy transferred to molecules of the chain was varied in wide range but it must be less than the energy needed to break the chain. Chains with water molecules that were cut from microcrystal of ice (homogeneous chains) as well as net of hydrogen bonds (heterogeneous chains) were under our investigations. In last case areas with periodical structure symbolize embedded crystal nanoclusters in the whole disordered medium.We showed that nonlinear oscillations become excited in the chains after low-energy ion impact and as a result of them molecules become stabilized in new positions, which results in the formation and development of new metastable molecular groups (nanoclusters). In homogenous chains formed nanoclusters correspond to elements of “molecular memory”. We showed that in homogeneous molecular chains critical energy needed for self-organization processes development is less than for nonlinear molecular chains with already embedded clusters. In this case nanocluster becomes an active zone which determines further self-organization processes. It is clusters that provide new complexes of physical and chemical properties. This computer model can be also used for simulation of low-energy ion impact on polymers and biological objects.
Carbon Nanospheres: “Green” Synthesis, Characterization, and Growth Kinetics
Authors: Doorley Mathilda , Mishra Sanjay R , Laradji Mohamad , Gupta Ram K , Ghosh Kartik 
Published: April 2011

ABSTRACTAn attempt is made to understand the growth kinetics of carbon nanospheres (CNS) synthesized using a “green” technique. An aqueous solution of glucose, the precursor, was hydrothermally treated to produce porous CNS with homogeneous size distribution and smooth surfaces. The growth of CNS was studied by evaluating transmission electron microscope images as a function of hydrothermal reaction time and temperatures. Raman spectra revealed the presence of short-ordered graphitic nanostructures in an amorphous carbon matrix. FTIR spectroscopy confirms the carbonization of glucose and shows the presence of surface hydroxyl groups on CNSs. Based on various experimental observations it is proposed that the growth of CNSs is dictated by a reaction-controlled mechanism where long chain glucose-based oligomers bond to the CNS surface. The narrow size distribution and highly hydrophilic surface of these amorphous CNS makes them potential candidates for biomedical applications.
Enlarging the Bandwidth of Nano-scale Propagating Plasmonic Modes in Deep-subwavelength Cylindrical Holes
Authors: Catrysse Peter B. , Fan Shanhui 
Published: April 2011

ABSTRACTSubwavelength cylindrical holes in optically thick metallic films always support a propagating HE11 mode near the surface plasmon frequency, regardless of how small the holes are. For holes filled with a uniform dielectric material, the bandwidth of the HE11 mode asymptotically approaches zero as the hole size is reduced to deep-subwavelength scales. We show that it is possible to create nano-scale propagating plasmonic modes with very large bandwidth in holes that are concentrically filled with two different dielectric materials, even when the hole radius goes to zero.
Surface Plasmon Structures for Surface-Enhanced Raman Scattering
Authors: Khan Muhammad Ajmal , Huang He , Shanker B. , Hogan Timothy P. 
Published: April 2011

ABSTRACTSurface-enhanced Raman scattering (SERS) can enhance the intensity of Raman radiation by many orders of magnitude for molecules bound to metallic nanostructures. SERS is generally thought to have been a result of excitation of surface plasmons in nanostructured metal, which greatly enhances local electric field experienced by the molecule. Common SERS substrates fabricated using noble metal colloidal or electrochemically roughened thin films suffer from lack of homogeneity where only few hot spots yield high enhancement. We explore semiconducting nanowires and metallic nanorods as an economical, stable, and uniform SERS substrate for the detection of trace amount of chemicals and bio-species. We utilize bulk synthesized semiconducting nanowires as nano-scale structures that can be coated with noble metals or their colloidal forms to allow for excitation of surface plasmons over broad frequency range. The use of nanowires as SERS substrates has several advantages. The surface properties of these nanowires are highly reproducible and well defined as compared to other systems like colloidal aggregates, electrochemical roughening etc. The synthesized nanowires offer many unique features (sharp vertices, noncircular cross-sections, inter-wire coupling) that may lead to larger field enhancement factors. High density of nanowires means close interaction between adjacent nanowires, which enables SERS to manifest for a broad selection of excitation sources. We have synthesized germanium dioxide and zinc oxide nanowires using the vapor-liquid-solid growth mechanism utilizing a simple quartz tube furnace set up. The nanowires are grown either using thin gold film (5-15 nm) or colloidal gold (20 nm or 60 nm) as catalyst on substrates of silicon, quartz, and alumina. The resulting nanowires are dense (100-300 nm diameter, 10-40 μm long) and randomly distributed on the substrate. The nanowires are subsequently coated with thin films (10-15 nm) of gold that provide plasmons active surface. We have also investigated silver nanorods on glass formed by grazing angle deposition using e-beam evaporation. These nanorods have a diameter of ∼ 50-70 nm with lengths averaging 300-400 nm. These well aligned high aspect ratio and dense structures are ideal for excitation of surface plasmons. The synthesized structures have been characterized using SEM, TEM, and EDS. The SERS studies were conducted using EzRaman-L system from Enwave Optronics, Inc. Silver nanorods and gold-coated nanowires have been found to exhibit significant Raman enhancement for micro-molar concentrations of Rhodamine 6G and Nile blue, and are promising candidates for SERS applications.
Geometrical Study on Change of Pore Volume of MCM-41 Functionalized with Aminopropyl Groups
Authors: Murakami Kenji , Fuda Kiyoshi , Sugai Mikio 
Published: April 2011

ABSTRACTMesoporous silicas functionalized with aminopropyl groups were synthesized by co-condensation of tetraethoxysilane (TEOS) and 3-aminopropyl triethoxysilane (APTES) and characterized by nitrogen adsorption-desorption measurements. The pore volume drastically decreased from about 900 mm3/g for the unfunctionalized mesoporous silica to about 300 mm3/g for the aminopropyl-functionalized mesoporous silica (1.65 mmol-NH2/g). This result was explained in terms of the surface density of the aminopropyl groups in the pore.