bluuebunny/crossref_metadata_2025 huggingface dataset:
In Situ Thin Film Stress Measurements – A Path to Understanding the Structure and Morphology of Electron Beam Evaporated ZnS
Authors: Barrioz Vincent , Irvine Stuart J. C. , Paul D.
Published: April 2011

ZnS is a material of choice in the optical coating industry for its optical properties and broad transparency range. One of the drawbacks of ZnS is that it develops high compressive intrinsic stress resulting in large residual stress in the deposited layer. This paper concentrates on the evolution of residual stress reduction in ZnS single layers, depending upon their deposition rate or the substrate temperature during deposition (i.e. 22 °C and 133 °C). The substrate preparation is addressed for consideration of layer adhesion. Residual stress of up to − 550 MPa has been observed in amorphous/poor polycrystalline ZnS layers, deposited on CMX and Float glass type substrates, by electron beam evaporation at 22 °C, with a surface roughness between 0.4 and 0.8 nm. At 133 °C, the layer had a surface roughness of 1 nm, the residual stress in the layer decreased to − 150 MPa, developing a wurtzite structure with a (002) preferred orientation. In situ stress measurements, using a novel optical approach with a laser-fibre system, were carried out to identify the various sources of stress. A description of this novel in situ stress monitor and its advantages are outlined. The residual stress values were supported by two ex situ stress techniques. The surface morphology analysis of the ZnS layers was carried out using an atomic force microscope (AFM), and showed that stress reduced layers actually gave rougher surfaces.
Preparation of Plate-Like Bulk Beta Iron-Disilicide Crystals Using Metal to Semiconductor Phase Transition by Heat Treatment
Authors: Osamura Masato , Ishihara Hidetaka , Liu Zhengxin , Tanoue Hisao , Sakuragi Shirou. , Hoshino Yasushi , Nakayama Yasuhiko , Makita Yunosuke
Published: April 2011

Plate-like β-FeSi2 bulk crystals with size of 10×10 mm2 and thickness of 1 mm were fabricated by annealing CVT (chemical vapor transport)-grown plate-like α-Fe2Si5 at 800°C in Ar atmosphere. Before annealing, α-Fe2Si5 crystals were characterized by x-ray diffraction (XRD) and scanning electron microscopy (SEM) to be single crystals with flat surfaces. XRD measurements of β-FeSi2 crystals subjected to annealing showed that they had a po lycrystalline structure. The mean Fe/Si co mposit ion rat io of β-FeSi2 crystal measured by energy dispersive x-ray spectroscopy (EDX) was 31/69 and it was the same as that of α-Fe2Si5 bulk crystal before annealing. SEM, Raman scattering and electron probe micro-analysis (EPMA) measurements identified that there existed small Si precipitates mixed in the matrix of β-FeSi2 crystals. At annealing temperature of 800°C, the plate-like β-FeSi2 bulk was obtained even the annealing duration time was as short as 5 hours.
Oxide Structures formed on Silver Single Crystals due to Hyperthermal Atomic Oxygen Exposure
Authors: Li Long , Yang Judith C.
Published: April 2011

Silver (100) and (111) single crystals were exposed to a unique laser detonation atomic oxygen source, which produces a high flux of 5 eV atomic oxygen, for seven hours at 220°C. The resultant oxide and oxide-metal interfaces were characterized by optical, scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HREM). The oxide scale was more than 10-micron thick and very weakly attached to the Ag substrate. The silver oxides were complex and surprising, differ in their thickness and the oxide phases due to the orientation of the Ag single crystals. The cross-section TEM studies revealed complex microstructures with many defects, such as micro-twins, porosity and irregular shaped grains.
Electrochemical Properties Of Copper Oxide Surfaces, Buried Interfaces, And Subsurface Zones And Their Use To Characterize These Entities
Authors: Cocke David L. , Hossain Mohammad A. , Mencer Donald E. , McWhinney Hylton , Parga Jose R. , Mollah Mohammad Y. A. , Naugle Donal , Kesmez Mehmet
Published: April 2011

Electrochemistry of oxides is an expanding area of oxide characterization. Although, interfacial characterization techniques including surface science methods have contributes substantially to our current understanding of the processes involved in the oxidation of metals and alloys. The characterization of subsurface zones and buried interfaces still remain a major challenge. Copper reactions with oxygen have been studied by high vacuum based techniques of AES, ELS, ISS, XPS. SIMS, LEED. STM, SEXAFS, HEIS and PFDMS and with optical methods, like UV-Vis-NIR, diffuse reflectance spectroscopy, FTIR and photoluminescence spectroscopes. However it has become evident that the processes that produce thermally and plasma grown oxide films on metals and alloys are electrochemical in nature and can be modeled by electrochemical concepts. Therefore, it is important that the oxide over layers, thin films and thick films be characterized by electrochemical means -with electrochemical methods, such as linear potential sweep voltammetry, cyclis voltammetry, galvanostatic reduction and coulometry which allow the identification of copper (I), copper (II) and copper (III) oxides. Interest in copper as a technologically important material needs to be met with greater understanding of the fundamental nature of copper oxide structures. In this study, the authors demonstrate the use of Linear Sweep Voltammetry (LSV) to study buried structures in the thermally grown oxide layers on copper. In particular, LSV can be used to detact reactions at buried interfaces. It also recognizes Cu3O2 and the decomposition of copper oxides at the metal-oxide layers on copper. In particular, LSV can be used to detect reactions at buried interface. The two key parameters that drive oxide growth and decomposition are demonstrated to be oxygen activity and the free energies of formation of the oxides. The complex nature of the oxidation of copper, as well as other metals and alloys, will be described qualitatively using the Modified Cabrera-Mott (C-M) Model. Surface studies of oxidation of metals and alloys need to be supported and complemented by other techniques such as electrochemical methods.
Electrochemical Removal of Oxygen in amorphous Zr55Cu30Al10Ni5
Authors: Castellero Alberto , Bossuyt Sven , Chen George Z. , Lindsay Greer A.
Published: April 2011

Contamination with oxygen is known to reduce the processability and otherwise affect the properties of Zr-based bulk metallic glasses (BMGs). Due to their affinity for oxygen, however, it is difficult and/or expensive to reduce the oxygen level in these materials. As a result, the glass-forming ability (GFA) of commercial-grade BMGs is significantly lower than that of research-grade materials. We present the application of a novel electrochemical method to this problem. The general principle is to remove oxygen from the material by direct electrochemical reduction in a molten-salt electrolyte. A cathode consisting of a porous metallic phase containing dissolved oxygen is submerged in a molten mixture of chlorides. When a current is applied, oxygen is ionised at the cathode, dissolved in the molten salt and discharged at the anode. We investigate thermodynamic and kinetic limitations to the reduction in oxygen content and the resulting improvement in GFA that can be achieved when this method is applied to glass-forming alloys such as Zr55Cu30Al10Ni5.
Undercooling And X-Ray Structural Studies Of Ti-Zr-Ni Liquids
Authors: Lee G.W. , Gangopadhyay A.K. , Kelton K.F. , Hyers R.W. , Rathz T.J. , Robinson M.B. , Rogers J. R. , Hennet L. , Krishnan S.
Published: April 2011

Maximum undercooling results for the icosahedral phase (i-phase), polytetrahedral C14 Laves phase, and solid solution phases are presented as a function of composition in Ti-Zr-Ni liquids. Containerless processing was achieved using the electrostatic levitation facility located at NASA/Marshall Space Flight Center. The maximum reduced undercooling decreases with increasing icosahedral short-range order in the ordered phase. The first synchrotron x-ray diffraction data from aerodynamically levitated liquids of Ti-Zr-Ni alloys suggest an icosahedral short-range order in the liquids, supporting Frank's hypothesis, correlating icosahedral order in the liquid with the nucleation barrier to the crystal phase. The strong negative heats of mixing between Ti/Zr and Ni and their relative atomic sizes likely favor the formation of this local icosahedral order.
A Thermodynamic Model for Amorphization and Topological Criteria
Authors: Senkov O.N. , Miracle D.B. , Rao S.
Published: April 2011

A thermodynamic model for amorphization is developed which allows analysis of the effect of composition, atomic radii, and elastic constants of constitutive elements on amorphization. The model is based on comparison of the Gibbs free energy and entropy of a defective crystal and undercooled liquid. The glass transition temperatures for thermodynamically unstable amorphous phases are determined as a function of topological parameters of an alloy. It increases with an increase in the atomic size of the solvent element and it has a maximum at a specific alloy composition. Topological criteria for alloy compositions that can produce a thermodynamically stable amorphous state are outlined and discussed.
Transient Deformation and Flow in Bulk Metallic Glasses and Deeply Undercooled Glass Forming Liquids — A Self-Consistent Dynamic Free Volume Model
Authors: Bossuyt Sven , Demetriou Marios D. , Johnson William L. , Lindsay A.
Published: April 2011

Recently, a self-consistent dynamic free volume model was proposed to analyze the Newtonian and non-Newtonian uniform steady-state flow data for bulk glass forming liquids such as those of the Zr-Ti-Cu-Ni-Be Vitreloy family. The model is based on the traditional free volume model of the glass transition, the Vogel-Fulcher-Tammann (VFT) equation, and a simple treatment of free volume production and annihilation during flow. It was shown that the model results in a simple one-parameter fit to extend the VFT equation for Newtonian flow to non-Newtonian uniform steady-state flow. We further extend the model to include transient uniform flow, by considering the evolution of free volume with time.
Grimsel Test Site - The Next Decades
Authors: Vomvoris Stratis , Kickmaier Wolfgang , McKinley Ian G.
Published: April 2011

The Grimsel Test Site, which has been in operation since 1984, is known in the radioactive waste management community for the scope and quality of the experiments and projects performed over the last two decades. This paper will overview Nagra's commitments and the current plans for future activities in association with Grimsel, which are being developed considering time scales of the order of a decade or more.
Waste Form Release Calculations for Performance Assessment of the Hanford Immobilized Low-Activity Waste Disposal Facility Using a Parallel, Coupled Unsaturated Flow and Reactive Transport Simulator
Authors: Bacon Diana H. , Peter McGrail B.
Published: April 2011

A set of reactive chemical transport calculations was conducted with the Subsurface Transport Over Reactive Multi-phases (STORM) code to evaluate the long-term performance of a representative low-activity waste glass in a shallow subsurface disposal system located on the Hanford Site. Technetium, the main contributor to a drinking water dose, is assumed to be released congruently with the dissolution of the glass. Sodium is released at a higher rate via a kinetic ion-exchange reaction. Aqueous equilibrium reactions involving sodium and other dissolved glass constituents increase the pH, and hence the rate of glass dissolution. The precipitation of secondary minerals can also lower the amount of aqueous dissolved silica, which can increase the rate of glass dissolution. Predicted technetium release rates, however, remain several orders of magnitude lower than required by drinking water regulations.
Diffusion and Migration of Ions in Sedimentary Rock Matrix: Behaviour of Cesium and Iodide in Micropores of Sandstone
Authors: Sato Haruo , Muraoka Tamotsu
Published: April 2011

In-diffusion experiments for Cs+ and I- in sandstone were performed as a function of ionic strength of porewater ([NaCl] =0.01, 0.51M) and tracer concentration ([Cs1] =7.5E-5, 1.5E-2M) together with the measurements of the fundamental properties of sandstone, and apparent diffusivities (Da) and rock capacity factors (α) for Cs+ were obtained. The obtained Da-values for Cs+ were scarcely dependent on [NaCl], but increased with increasing [Cs+]. This trend is consistent with that of α-values, indicating that although effective diffusivity and distribution coefficient scarcely depend on [NaCl], those depend on [Cs+]. The concentration profiles of I- were all in breakthrough. Although this indicates that I- diffusion is faster than that of Cs+, the concentration profiles of I- may have been lower than those for blank samples.
Thermogravimetric Thin Aqueous Film Corrosion Studies of Alloy 22; Calcium Chloride Solutions at 150°C and Atmospheric Pressure
Authors: Hailey Phillip , Gdowski Greg
Published: April 2011

The extent of reaction of alloy 22 with limited amounts of aqueous calcium chloride (CaCl2) was investigated. Alloy 22 is a highly corrosion-resistant nickel-chromium-molybdenum-tungsten alloy. Specimens were polished to a mirror finish prior to aerosol salt deposition. An aqueous film was formed on the specimen surface by deliquescence of deposited CaCl2 at 150°C and 22.5% relative humidity (RH). The reactant gas was a continuous flow of purified humidified laboratory air. The reaction progress as a function of time was continuously measured in-situ by a microbalance. An initial weight gain due to CaCl2 deliquescence was observed. A steady weight loss was observed over the next 24 hours, after which no further weight change was apparent. During the period of weight loss, white precipitates formed and the specimen surface became visibly dry. Post-test analyses indicated that the precipitates consisted of calcium, chloride, and oxygen.
Effect of Anions on the Fluoride Corrosion of Titanium-Grade 7
Authors: Pulvirenti A. L. , Needham K. M. , Adel-Hadadi M. A. , Wong D. S. , Barkatt A. , Marks C. R. , Gorman J. A.
Published: April 2011

The effects of chloride, sulfate, and nitrate on the fluoride ion local attack of Ti-Grade 7 (Ti-7: UNS R52400) were investigated. It was observed that a chloride: fluoride ratio of as high as 10 : 1 by mole was necessary to produce visible severe attack in immersion tests. Localized attack on Ti-7 was most severe at approximately 120°C, and at neutral pH. However, electrochemical studies detected that a narrowing of the passive region can occur at chloride: fluoride ratios as small as 1.1 : 1 by mole. The addition of sulfate did not significantly inhibit pitting or stress corrosion cracking of Ti-7 U-bends. However, the addition of nitrate is suspected to act as an effective inhibitor.
Effects of Fluoride and other Anions on the Corrosion of Alloy 22
Authors: Pulvirenti A. L. , Needham K. M. , Adel-Hadadi M. A. , Barkatt A. , Marks C. R. , Gorman J. A.
Published: April 2011

Samples of Alloy 22 were tested in solutions containing various anions in order to determine their effect on the corrosion of the alloy. It was found that Alloy 22 is relatively corrosion resistant in HCl and HNO3 at pH 1 and 160°C (general corrosion rates on the order of 10 μm/year), but more susceptible to phosphoric acid, especially under reducing conditions. The presence of fluoride raised the corrosion rate of Alloy 22 to the order 1 mm/year at pH 1, and fluoride is still active towards Alloy 22 at pH levels as high as 3.5. Samples tested in solutions of 1000xJ13 in which the pH was altered during testing showed an increase in corrosion rate over solutions of constant pH. Preliminary electrochemical tests suggest that nitrate may be an effective corrosion inhibitor in fluoride containing solutions, while sulfate is not.
Leaching of Spent Fuel under Anaerobic and Reducing Conditions
Authors: Albinsson Yngve , Ödegaard-Jensen Arvid , Oversby Virginia M. , Werme Lars O.
Published: April 2011

Sweden plans to dispose of spent nuclear fuel in a deep geologic repository in granitic rock. The disposal conditions allow water to contact the canisters by diffusion through the surrounding bentonite clay layer. Corrosion of the canister iron insert will consume oxygen and provide actively reducing conditions in the fluid phase. Experiments with spent fuel have been done to determine the dissolution behavior of the fuel matrix and associated fission products and actinides under conditions ranging from inert atmosphere to reducing conditions in solutions. Data for U, Pu, Np, Cs, Sr, Tc, Mo, and Ru have been obtained for dissolution in a dilute NaHCO3groundwater for 3 conditions: Ar atmosphere, H2atmosphere, and H2atmosphere with Fe(II) in solution. Solution concentrations forU, Pu, and Mo are all significantly lower for the conditions that include Fe(II) ions in the solutions together with H2atmosphere, while concentrations of the other elements seem to be unaffected by the change of atmospheres or presence of Fe(II). Most of the material that initially dissolved from the fuel has reprecipitated back onto the fuel surface. Very little material was recovered from rinsing and acid stripping of the reaction vessels.
Rapid Manufacturing with Direct Metal Laser Sintering
Authors: Lind J-E. , Hanninen J. , Kotila J. , Nyrhila O. , Syvanen T.
Published: April 2011

The term Rapid Manufacturing is today very often used as a substitute for Rapid Prototyping, because the manufacturing processes and materials have developed so much that the parts produced with the machines can even be used as functional production parts. For Direct Metal Laser Sintering (DMLS) this was enabled by the introduction of the powders for 20 micron layer thickness; steel-based powder in 2001 and bronze-based powder in 2002. Successful rapid manufacturing with DMLS does not only mean the reduction of layer thickness, but it is a sum of many factors that had to be optimized in order to make the process work with the 20 micron layer thickness: the metal powder behavior in very thin layers is not the same as with thicker layers, the demands for the support structures are higher and the possibility of using multiples of the layer thickness gives additional freedom. By optimizing the process parameters the UTS values for the steel-based powder increased up to 600 MPa and for the bronze-based powder up to 400 MPa. At the same time the surface roughness (Ra) values after shot peening were 3 microns and 2 microns, respectively. Although using thinner layers also increases the building time the advantage is gained in drastically reduced finishing times due to increased surface quality and detail resolution. Typical geometries produced by DMLS are difficult-to-manufacture components and components typically produced by P/M or even by die-casting. The paper covers the development aspects in both material and process development and also presents some realized case studies.
Computational Design, Freeform Fabrication and Testing of Nylon-6 Tissue Engineering Scaffolds
Authors: Das Suman , Hollister Scott J. , Flanagan Colleen , Adewunmi Adebisi , Bark Karlin , Chen Cindy , Ramaswamy Krishnan , Rose Daniel , Widjaja Erwin
Published: April 2011

Advanced and novel fabrication methods are needed to build complex three-dimensional scaffolds that incorporate multiple functionally graded biomaterials with a porous internal architecture that will enable the simultaneous growth of multiple tissues, tissue interfaces and blood vessels. The aim of this research is to develop, demonstrate and characterize techniques for fabricating such scaffolds by combining solid freeform fabrication and computational design methods. When fully developed, such techniques are expected to enable the fabrication of tissue engineering scaffolds endowed with functionally graded material composition and porosity exhibiting sharp or smooth gradients. As a first step towards realizing this goal, scaffolds with periodic cellular and biomimetic architectures were designed and fabricated using selective laser sintering in Nylon-6, a biocompatible polymer. Results of bio-compatibility and in vivo implantation studies conducted on these scaffolds are reported.
Evaluating the Mechanical Properties of MEMS by Combining the Resonance Frequency and Microtensile Methods
Authors: Son Dongil , Kim Jong-jin , Kim Dong Won , Lim Tae Won , Kwon Dongil
Published: April 2011

Tensile, fracture and fatigue properties of single- and polycrystalline silicon and LIGA-Ni were evaluated by the resonance frequency and microtensile methods. A new method for evaluating the fracture toughness that combines these two methods was proposed. A pre-crack was generated in an electrostatically driven test specimen and a load was applied by piezoelectrically driven microtensile equipment. Before the microtensile test, a new surface micromachining technique including a two-step sacrificial layer removal was used. The pre-cracked specimen was attached to microtensile equipment by a UV-adhesive glass grip. The fatigue pre-crack was successfully introduced and the fracture toughness could be derived on the basis of fracture mechanics. The fracture toughness of the pre-cracked specimen was relatively low compared with that of the notched specimen, so that we were able to determine the effect of the notch tip radius. The fatigue properties of LIGA-Ni film were also evaluated. A tensile-tensile fatigue load was applied by a piezoelectric actuator, and real-time load-displacement curves were displayed via computer. The dependence of S-N curves, crack propagation rates and fatigue-notch factor on the applied load for 10 μm Ni film was analyzed.
Semiconductor surface – molecule interactions: a case study in the wet etching of InP by α-hydroxy acids
Authors: Bandaru Prabhakar
Published: April 2011

The controllable etching of InP semiconductor surfaces is desired in removing damaged layers for facilitating regrowth and obtaining good electronic properties. We have observed that organic acids (α-hydroxy acids: tartaric, lactic, citric and malic) used in conjunction with HCl to etch (100) InP result in smoother and defect free surfaces, in comparison to etches based on inorganic acids alone. The chelating action of the organic acids aids in efficiently removing In from the surface. Based on these results, it is hypothesized that a consideration of the energy levels of the semiconductor and adsorbed molecules could help in devising new semiconductor etchants.
Thin-Film Electrostatic Actuators on Flexible Plastic Substrates
Authors: Gaspar J. , Chu V. , Conde J. P.
Published: April 2011

Thin-film silicon micromachined bridge actuators are fabricated at temperatures below 110°C on flexible polyethylene terephthalate plastic substrates. The micromechanical structures are electrostatically actuated both at the resonance frequency and at below-resonance frequencies, and the resulting deflection is optically monitored. Deflections up to 100 nm are measured below the resonance frequency with subnanometric precision. Resonance frequencies in the MHz range are observed in vacuum with quality factors of the order of 100. The movement is studied as a function of the geometrical dimensions of the actuators, of the actuation voltage and of the measurement pressure. The experimental data are analyzed using an electromechanical model. The performance of hydrogenated amorphous silicon based resonators on PET substrates is compared to that of similar microstructures on glass substrates.
Characterization of Mechanical Properties of Silicon Nitride Thin Films for Space Applications
Authors: Chuang Wen-Hsien , Luger Thomas , Fettig Rainer K. , Ghodssi Reza
Published: April 2011

Mechanical properties of micro-electro-mechanical systems (MEMS) materials at cryogenic temperatures are investigated to extend MEMS devices into space applications. A helium-cooled measurement setup mimicking the outer space environment is developed and installed inside a focused-ion-beam (FIB) system. T-shape, low-stress LPCVD silicon nitride cantilevers suspended on a silicon substrate are fabricated as the test structures using bulk micromachining technique. A lead-zirconate-titanate (PZT) translator and a silicon diode are utilized as an actuator and a temperature sensor in the measurement setup, respectively. The resonant frequencies of an identical cantilever with different “milling masses” are measured to obtain the thickness and the Young's modulus. Additionally, a bending test is performed to determine the fracture strength. From the experiments, the Young's modulus of LPCVD silicon nitride thin films varies from 260.5 GPa ± 5.4 GPa at room temperature (298 K) to 266.6 GPa ± 4.1 GPa at 30 K, while the fracture strength ranges from 6.9 GPa ± 0.6 GPa at room temperature to 7.9 GPa ± 0.7 GPa at 30 K.
Localized, In-Situ Vacuum Measurements For MEMS Packaging
Authors: Moelders Nicholas , Daly James T. , Greenwald Anton C. , Johnson Edward A. , McNeal Mark P.
Published: April 2011

MEMS devices have unique packaging considerations compared to conventional semiconductor devices. They tend to have relatively large die size and many architectures cannot tolerate elevated temperatures. Often these devices require a vacuum environment for efficient operation. While advances have been made in hermetic packaging of MEMS devices, vacuum packaging remains elusive. One significant problem in developing vacuum sealing has been the inability to determine, readily and non-destructively, the vacuum level inside the package. We have previously described the development of a silicon MEMS-based chip design, “SensorChip™,” with integrated photonic crystal and reflective optics, which uses narrow-band optical emission and absorption for selective identification of gas and chemical species. Because the power consumption required to maintain a specific temperature is directly related to the vacuum level, these devices effectively serve as microscopic Pirani gauges – local vacuum sensors in the moderate vacuum range (0.01 to 1.0 torr) of interest to MEMS devices. Using the membrane itself as a vacuum gauge during sealing has proven to be an invaluable tool in developing a robust vacuum seal in a leadless chip carrier package. It has enabled us to optimize choice of design, materials and processing.
Effect of Polymer Substrates on Nano Scale Hot Embossing
Authors: Lee Jin-Hyung , Lim Hyun-Woo , Park Jin-Goo , Lee Eun-Kyu , Kim Yangsun
Published: April 2011

Hot embossing has been widely accepted as an alternative to photolithography in generating patterns on polymer substrates. The optimization of embossing process should be accomplished based on polymer surface properties. Therefore, in this paper, polymers with different surface characteristic were selected and the surface properties of each polymers such as surface energy and adhesion force were investigated by contact angle and AFM. Based on these results, the imprinted nano patterns were compared. Silicon molds with nano size patterns were fabricated by e-beam direct writing. Molds were coated with self-assembled monolayer (SAM) of (1, 1, 2, 2H –perfluorooctyl)-trichlorosilane to reduce the stiction between molds and polymer substrates. For embossing, pressure of 500 psi, embossing time of 5 min and temperature of above transition temperature were applied. Mr-I 8010 polymer (Micro Resist Technology), Polymethylmethacrylate (PMMA 495k) and LOR (polyaliphatic imide copolymer) were used as substrate for hot embossing process development in nano size. These polymers were spun coated on the Si wafer with the thickness of 150 nm. The nano size patterns obtained by hot embossing were identified by atomic force microscopy without breaking the pattern and compared based on the polymer surface properties. The mr-I 8010 which has the lowest surface energy and adhesion force shows the best demolding property.
2D InP etching simulation under high density plasma of chlorine
Authors: Rhallabi A. , Liu B. , Marcos G. , Landesman J. P.
Published: April 2011

A gas phase kinetic model of chlorine in an ICP reactor (Inductive Coupled Plasma) combined with a surface model have been developed to study the etching profile evolution of InP material. A gas phase chemistry model is used to predict the main neutral and charged specie fluxes impinging upon etched InP surface. These particle fluxes are then injected as input parameters into both a Monte-Carlo sheath model and a 2D surface model to predict the etch profile topography. The coupling between the gas kinetic model, sheath and surface models allows a direct prediction of the InP etch profile evolution versus reactor parameters (pressure, source power, Cl2 flow rate, DC bias on the substrate‥). A parametric study is carried out to show the role of some plasma parameters on etch rate, anisotropy and adsorbed InP surface state by chlorine.
Evolution of Mesas on Si(111) Surface Under Sublimation: Nanofabrication through the Control of Atomic Steps
Authors: Chang Kee-Chul , Blakely Jack M.
Published: April 2011

How the surface morphology of a low index crystal surface evolves under annealing below the roughening temperature is still being investigated both theoretically and experimentally. This research is needed to understand the stability of nanostructures and for the control of step array on surfaces for various technological applications.

We have approached this problem from an experimental point of view by looking at the step morphology on the top of mesas patterned on Si(111) after flashing at 1200°C and annealing between 1000–1100°C. We find that after annealing, nanometer height ridges develop on the edges of the mesas except for one edge which becomes a source for steps advancing into the mesa top. The edge that does not develop a ridge is mainly determined by the initial miscut of the surface.

We attempt to explain our results through step dynamics and present some applications of this phenomena in creating novel arrays of steps.
Advanced Anodic Bonding Processes For MEMS Applications
Authors: Dragoi V. , Lindner P. , Glinsner T. , Wimplinger M. , Farrens S.
Published: April 2011

Anodic bonding is a powerful technique used in MEMS manufacturing. This process is applied mainly for building three-dimensional structures for microfluidic applications or for wafer level packaging. Process conditions will be evaluated in present paper. An experimental solution for bonding three wafers in one single process step (“triple-stack bonding”) will be introduced.
Formation of Nanosized Metallic Ag Grains by Oxidation of Ag Single Crystals with Hyperthermal Atomic Oxygen
Authors: Li Long , Yang Judith C.
Published: April 2011

Silver single crystals (Ag(100), Ag(111)) were exposed to 5eV hyperthermal atomic oxygen, created by a laser detonation of molecular oxygen at a substrate temperature of 220°C for 7 hours. Oxide scales of more than ten microns formed on both Ag (100) and Ag (111) substrates. The microstructural investigation of the oxide layers by high resolution transmission electron microscopy (HRTEM) revealed that the “oxide” scales are predominately composed of nanosized polycrystalline silver grains (5–100nm) as well as a small amount of nanosized silver oxides. The results were remarkably different than the O2 oxidation. The HRTEM investigation suggested that the grains of polycrystalline silver were first carved off from the substrate into “oxide” scale by lattice expansion and decohesion, which are driven by atomic oxygen diffusion in Ag lattice, occupation of oxygen atoms at the interstitial sites of Ag lattice, and partially internal oxidation. The grains in the scale were also subject to continuing oxidations with the atomic oxygen--secondary poly-crystallization, and changed to smaller grains. The preferred oxidation fronts in silver lattice is along the {111} planes.
UV Curable Polymers with Organically Modified Clay as the Nanoreinforcements
Authors: Uhl Fawn M. , Hinderliter Brian R. , Davuluri Siva Prashanth , Croll Stuart G. , Wong Shing-Chung , Webster Dean C.
Published: April 2011

UV curable polymers are prevalent in microelectronic applications. Several advantages are associated with UV curing such as rapid cure, solvent free systems, application versatility, low energy requirements, and low temperature operation. To be used in electronics the films must posses the following attributes: high glass transition, barrier properties, low shrinkage, flexibility, and enhanced mechanical properties. The area of polymer-clay nanocomposites have been widely investigated by researchers and improved mechanical, thermal, and barrier properties were reported. Most researchers have attempted nanocomposite formation by melt mixing or in situ polymerization. Little is understood on UV curable nanocomposites. This paper seeks to examine nanoclay-containing polymers using organomodified montmorillonites in UV curable systems and the effects of such clay inclusions on the properties of UV cured films. By x-ray diffraction it appeared that intercalated structures were formed. In the case of an epoxy acrylate formulation an increase in glass transition temperature was observed for formulations containing clay.
Synthesis of mesoporous complex framework zirconium phosphates via organicinorganic nanocomposites: genesis of structure, adsorption and catalytic properties
Authors: Frolova Yulia V. , Sadykov Vladislav A. , Pavlova S. N. , Veniaminov S. A. , Bunina R. V. , Burgina E. B. , Kolomiichuk V. N. , Larina T. V. , Mezentseva N. V. , Fedotov M. A. , Volodin A. M. , Paukshtis E. A. , Fenelonov V. B. , Roy R. , Agrawal D.
Published: April 2011

This work presents the first results of synthesis of framework binary phosphates of zirconium and transition metal cations (Co, Cu, Ce) via nanocomposites of starting inorganic salts with citric acid and studies of their structure genesis. Nanoparticles of layered Zr phosphates with typical sizes in the range of 18–24 Å are formedat the mixing stage. Less basic Cu and Co cations are mainly octa-coordinated with both phosphate groups of those nanoparticles and citric acid molecules. At subsequent thermal treatment, Cu and Co cations are incorporated within Zr phosphate nanoparticles acquiring a low coordination approaching a tetrahedral one while rearranging the nuclei structure into that of a framework type. Removal of citric acid by heating under air at 200–300°C preserves the size of nanoparticles while their ordered stacking forms mesoporous structure with a narrow pore size distribution ∼ 50 Å and specific surface area up to 200 m2/g after calcination at 600°C. The binary phosphates promoted by a small amount of Pt were found to be effective catalysts of NOx selective reduction by decane in the oxygen excess not subjected to coking with a high and stable performance at high space velocities in the presence of steam.
In-situ synthesis and magnetic properties of polystyrene/polypyrrole nanocomposite materials with uniformly dispersed iron nanoparticles
Authors: Srikanth H. , Poddar P. , Wilson J. L. , Mohomed K. , Harmon J. P.
Published: April 2011

Magnetic nanoparticles embedded in polymer matrices have excellent potential for electromagnetic device applications like EMI noise reduction. We have synthesized polystyrene (PS) and polypyrrole (PPy) composites by controllably dispersing bare and PS-coated Fe nanoparticles. These nanocomposites were processed as spin-coated thin films as well as in bulk form. The processing conditions were optimized to achieve good uniform dispersion of the nanoparticles in the polymer matrix. SEM scans revealed clustering of nanoparticles which was particularly evident at the surface in the conducting polymer nanocomposites. Magnetic hysteresis loop measurements indicate large coercivities associated with the clusters and surface oxidation of the Fe particles. Overall, the excellent dispersion coupled with reasonable control over magnetic properties achieved in our experiments is promising for electromagnetic applications of these materials.
Single-Walled Carbon Nanotube Rope for Gas Sensor Application
Authors: Lee J. W. , Choi Y. M. , Kong K. J. , Chang H. J. , Ryu B. H.
Published: April 2011

A chemical gas sensor with a novel pad pattern applicable to NH3, NO2, and H2 gas was developed based on single-walled carbon nanotube ropes. In this pattern named BCE (Barricade confronting electrode), several electrodes were located at the circumference of a sample and each pair of electrode tips was designed to confront to each other with a narrow interval. Several single-walled carbon nanotubes were shifted to the interval by the centrifugal force generated through the rapid rotation of a sample equipped on the spinner. Our device showed improved performance for NO2, NH3, and H2 gases compared with others in references.
Thermal and Electrical Transport Measurements of Single-Walled Carbon Nanotube Strands
Authors: Borca-Tasciuc Diana-Andra , LeBon Yann , Nanot Claire , Chen Gang , Borca-Tasciuc Theodorian , Cao Anyuan , Vajtai Robert , Ajayan Pulikel M.
Published: April 2011

This work reports temperature dependent thermal and electrical properties characterization of long (mm size) single-walled carbon nanotube strands. Electrical properties are measured using a 4-probe method. Thermal conductivity and specific heat capacity are determined using an AC driven, self-heating method. Normalized values of resistivity, thermal conductivity, specific heat, thermal diffusivity, and the temperature coefficient of resistance are reported. The trends observed in the temperature dependent properties are comparable with previously published data on multi-walled carbon nanotube strands measured with a similar technique.
Macroporous Silica and Alkylene-Bridged Polysilsesquioxane Gels with Templated Nanopores
Authors: Nakanishi Kazuki
Published: April 2011

Gels with hierarchical well-defined macropores and supramolecularly templated mesopores have been synthesized in the systems of pure silica as well as organic-inorganic hybrids. Cationic surfactants such as alkyltrimethylammonium salts and nonionic surfactants such as poly(ethyleneglycol)-poly(propyleneglycol)- poly(ethyleneglycol) triblock copolymers, EOPOEO, were found to be effective for pure silica system both in inducing the phase separation to give macroporous morphology and in templating the mesopores within a narrow distribution width. The partial introduction of methyl-modified alkoxide into the pure silica system lead to increased phase separation tendency accompanied by the disturbance of the supramolecular templating of mesopores. By contrast, in the 1,2-bis(trimethoxysilyl)ethane systems, poly(ethylene glycol) and EOPOEO were much better additive to induce phase separation in spite of the presence of internal hydrocarbon chain. Combination of well-defined macropores and supramolecularly templated mesopores has been achieved by selecting an appropriate molecular weight and concentration of EOPOEO in the starting composition.
Micromechanics of PS/PB/PS Triblock-Copolymer Films with Lamellar Morphology
Authors: Tzianetopoulou Theodora , Boyce Mary C.
Published: April 2011

Highly oriented, near single-crystal lamellar triblock copolymer films with alternating rubbery-glassy layer morphology possess an interesting anisotropy in their mechanical behavior, which can prove to be attractive for various applications. Here, the deformation micromechanics of highly oriented styrene-butadiene-styrene (SBS) lamellar triblock copolymers are investigated. The competing roles of the glassy (PS) and rubbery (PB) phases in the layered configuration are studied with micromechanical finite element based representative volume element (RVE) models subjected to tensile loading at different directions to the lamellar plane. The calculated material response is compared to x-ray and microscopy data from the literature, and proves to be successful in linking the macroscopic material response to the underlying physics of the microstructural evolution. Moreover, the RVE simulations are successful in reproducing the mechanical behavior of highly oriented nano-clay block copolymer nanocomposites. The response of layered-silicate models having 2wt% clay content is compared to the behavior of the respective neat block copolymer (BCP) and to existing experimental data. The ultimate objective is to facilitate these micromechanical models to design hierarchically ordered materials with properties, which will be optimally tailored for different classes of applications.
Anomalous behavior of confined-supercooled water near the bulk water hypothetical 2nd Critical Temperature
Authors: Mansour F. , Dimeo R. M. , Peemoeller H.
Published: April 2011

High resolution inelastic neutron scattering measurements of the molecular dynamics of deeply supercooled water confined to a porous host, MCM-41 are reported. Results obtained near the critical temperature of water are discussed. Anomalous behavior near and below the glass transition temperature is also presented and discussed. Results are compared to those from earlier studies on supercooled water.
Vibrational Dynamics of the OH Stretching Mode of Water in Reverse Micelles Studied by Infrared Nonlinear Spectroscopy
Authors: Maekawa Hiroaki , Ohta Kaoru , Tominaga Keisuke
Published: April 2011

Vibrational dynamics of the OH stretching mode of water in the water pool of reverse micelles (H2O/Aerosol OT (AOT)/isooctane) are studied by nonlinear infrared spectroscopy such as transient grating method and three-pulse photon echo peak shift measurements. The W0 value (W0 =[H2O]/[AOT]) is changed from 2 to 40, which corresponds to a water pool diameter of a few nm to about 20 nm. Polarization dependent transient grating experiments show rapid anisotropy decay of the OH stretching mode, which could be due to resonant intra and intermolecular energy transfer. From the three-pulse photon echo peak shift experiments, the spectral diffusion is found to be dependent on W0.
Dynamics of Buried Polymer -polymer Interfaces in Thin Films
Authors: Lurio L. B. , Hu Xuesong , Narayanan Suresh , Jiao Xuesong , Lal Jyotsana
Published: April 2011

We have performed x-ray photon correlation spectroscopy (XPCS) measurements on a polymer-bilayer system comprised of 100 nm polystyrene film on top of an 80 nm polybromostyrene film, supported on a Si substrate. In order to distinguish the dynamics at the top interface from that at the polymer-polymer interface we have performed the measurement at grazing incidence. In this geometry, a standing wave is set up in the film. We derive a relation for the intensity of the standing wave and the resulting diffuse scattering. This model is compared with the measured diffuse scattering from which we extract a value of 0.7±0.4 dyne/cm for the surface tension between PS and PBrS at 180C. XPCS was then measured in each of two standing wave conditions, first where diffuse scattering only occurs at the polymer-vacuum interface and then where it only occurs at the interior polymer-polymer interface. The measured time correlation functions for each of the two interfaces show clear differences, with the polymer-polymer interface exhibiting much slower dynamics.
Mechanical Properties Of Polyaniline / Multi-walled Carbon Nanotube Composite Films
Authors: Ramamurthy P. C. , Harrell W. R. , Gregory R. V. , Sadanadan B. , Rao A. M.
Published: April 2011

High molecular weight polyaniline / multi-walled carbon nanotube composite films were fabricated using solution processing. Composite films with various weight percentages of multiwalled carbon nanotubes were fabricated. Physical properties of these composites were analyzed by thermogravimetric analysis, tensile testing, and scanning electron microscopy. These results indicate that the addition of multiwalled nanotubes to polyaniline significantly enhances the mechanical properties of the films. In addition, metal–semiconductor (composite) (MS) contact devices were fabricated, and it was observed that the current level in the films increased with increasing multiwalled nanotube content. Furthermore, it was observed that polyaniline containing one weight percent of carbon nanotubes appears to be the most promising composition for applications in organic electronic devices.
Testing Techniques for Mechanical Characterization of Nanostructured Materials
Authors: Koch Carl C. , Scattergood Ronald O. , Linga Murty K. , Guduru Ramesh K. , Trichy Gopinath , Rajulapati Koteswararao V.
Published: April 2011

Testing methods are reviewed that can be applied to the small sample sizes which result from many of the processing routes for preparation of nanocrystalline materials. These include the measurement of elastic properties on small samples; hardness, with emphasis on nanoindentation methods; the miniaturized disk bend test (MDBT); the automated ball indentation test (ABI); the shear punch test; and the use of subsize compression and tensile samples.
Solid State Property - Bonding Electron Density – Volume Plasmon Energy Scaling Relationships: Novel AEM Technique for In Situ Diagnostics of Material Properties at the Nanoscale
Authors: Oleshko Vladimir P. , Howe James M.
Published: April 2011

Quantized high-frequency (∼1016 Hz) correlated longitudinal electron excitations (plasmons) generated in the energy-loss range 0–50 eV by fast electrons passing through any solid enable one to probe various states of matter. Their energy, Ep, is directly related to the density of valence electrons, thus allowing determination of solid-state properties that are governed by ground-state densities. Universal features and scaling in relations between Ep and the cohesive energy per atomic volume, bonding electron density and elastic constants have been established. The resulting correlations follow the universal binding energy relationship, thus providing new insights into the fundamental nature of structure-property relationships. They allow direct in situ determination of local material properties in an analytical electron microscope, as illustrated by examples utilizing Al- and Ti-based structural alloys.
Xe Precipitates in Aluminum
Authors: Birtcher Robert C. , Donnelly Stephen E. , Morrison Ian , Allen Charles W. , Furuya Kazuo , Song Minghui , Mitsuishi Kazutaka , Dahmen Ulrich
Published: April 2011

Real space, high-resolution transmission electron microscopy observations of Xe confined in nanometer size faceted cavities in Al yield information on both the inert gas and the matrix in which it is confined. At room temperature, Xe in such cavities can be liquid or an fcc solid. In larger cavities, Xe within can undergo melting and recrystallization. The Al surface energy can be deduced from the largest Xe nanocrystal at 300 K by setting the corresponding calculated Laplace pressure equal to the equilibrium pressure for melting of Xe, obtained from empirical bulk compression data. These surface energy values are 1.05 J m-2 for {111} facets and 1.10 Jm-2 for {200} facets. Because of the weak interactions, these values correspond to the surface tensions for Al at 300 K.

At room temperature, fluid Xe confined in small faceted cavities in aluminum has up to three ordered layers of Xe atoms at the Al interface. Conceptually in a three-dimensionally confined system of sufficiently small size, complete three-dimensional ordering of the fluid may occur. Molecular dynamics simulations have revealed that such ordering would result in fluid Xe confined to a small tetragonal volume solidifying as a body-centered cubic phase on compression.