bluuebunny/crossref_metadata_2025_split huggingface dataset:
Formation of transition-metal-based ohmic contacts to n-Mg2Si by Plasma Activated Sintering
Authors: Oguni Yohei , Iida Tsutomu , Matsumoto Atsunobu , Nemoto Takashi , Onosaka Junichi , Takaniwa Hironori , Sakamoto Tatsuya , Mori Daisuke , Akasaka Masayasu , Sato Junichi , Nakajima Tadao , Nishio Keishi , Takanashi Yoshifumi 
Published: April 2011

AbstractElectrode materials consisting of Cu, Ti and Ni were formed on Bi-doped n-type Mg2Si by means of a monobloc plasma-activated sintering (PAS) technique. Due to the difference in thermal expansion coefficients between Ti and Mg2Si, rather high residual thermal stresses gave rise to the introduction of cracks, which were mainly located in the Mg2Si layer, when Ti was used as the electrode material. In the case of the Cu electrodes, monobloc sintering could not be performed in a reproducible manner because Cu melts abruptly and effuses at around 973K, which is 100 K lower than the sintering temperature that is required for Mg2Si of good crystalline quality. When compared with the results for Cu and Ti, the monobloc PAS process for Ni was both stable and reproducible. The room-temperature I-V characteristics of Ni electrodes were considered to be adequate for practical applications, with durable Mg2Si-electrode junction properties being realized at a practical operating temperature of 600 K with ΔT = 500 K. The highest open circuit voltage (VOC) observed was 41 mV at ΔT = 500 K (between 873 K and 373 K) for Ni electrodes fabricated using the monobloc PAS process. The voltage (V) and current (I) values with a 10 Ohm load were ∼ 48 mV and ∼ 2 mA at ΔT = 500 K.
Study on the Fabrication and Characterization of LAST and LASTT Based Thermoelectric Generators
Authors: Wu Chun-I , Timm Edward J. , Ren Fei , Hall Bradley D. , Ni Jennifer , Downey Adam , D'Angelo Jonathan , Short Jarrod , Schock Harold , Case Eldon , Sootsman Joe , Han Mi-Kyoung , Kanatzidis Mercouri , Chung Duck-young , Hogan Timothy P. 
Published: April 2011

AbstractThermoelectric modules are of great interest for power generation applications where temperature gradients of approximately 500K exist, and hot side temperatures near 800K. The fabrication of such modules requires optimization of the material compositions, low contact resistivities, and low thermal loss.AgPbmSbTe2+m (LAST) and Ag(Pb1-xSnx)m SbTe2+m (LASTT) compounds are among the best known materials appropriate for this temperature range. Various measurement systems have been developed and used to characterize bulk samples in the LAST and LASTT systems within this operating temperature range. From the characterized data, modeling of modules based on these materials and segmented legs using LAST(T) with Bi2Te3 have been used to identify the optimal geometry for the individual legs, and the length of the Bi2Te3 segments. We have segmented LAST(T) with Bi2Te3 and achieved contact resistivities of less than 10 μΩ•cm2.Here we give a detailed presentation on the procedures used in the fabrication of thermoelectric generators based on LAST, LASTT, and segmented with Bi2Te3 materials. We also present the output data on these generators.
Volume and Enthalpy Relaxation in Bulk Metallic Glasses
Authors: Haruyama Osami 
Published: April 2011

AbstractVolume and enthalpy relaxation processes in a sub-Tg region were investigated by density and enthalpy experiments for bulk Pd-P based and Zr-based metallic glasses. Most of glasses except for a Pd40Ni40P20 glass exhibited a single relaxation process for both volume and enthalpy relaxations and the relaxation process was well described by a stretched exponential relaxation function, Φ(t)=exp{-(t/τ)β}, with a Kohlrausch index β less than 1. The as-quenched sample was pre-annealed in a supercooled liquid region to homogenize the density fluctuation quenched in an as-quenched state. Then the retardation of onset time of relaxation appeared in case of volume relaxation. The proportionality between enthalpy change ΔH and volume change Δv during relaxation was good for Pd42.5Cu30Ni7.5P20 glass within experimental error.
Microscale Thermoplastic Forming of Bulk Metallic Glasses: Numerical Simulation and Experiments
Authors: Henann David , Anand Lallit 
Published: April 2011

AbstractAn extremely promising microscale processing method for bulk metallic glasses called thermoplastic forming has emerged in recent years. However, most of the recent experimental thermoplastic forming studies have been conducted by trial-and-error. In this paper, we use the large-deformation constitutive theory of Henann and Anand [1] as a numerical simulation tool for the design of a micro-hot-embossing process. This numerical simulation capability is used to determine appropriate processing parameters in order to carry out a successful micron-scale hot-embossing operation on the metallic glass Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vitreloy-1). By carrying out a corresponding physical experiment, we demonstrate that micron-scale features in Vitreloy-1 may be accurately replicated under the processing conditions determined by use of the numerical simulation capability.
Computational generation of disordered structures of Al-12%Si. An ab initio approach
Authors: Diaz-Celaya J. Andres , Valladares R.M. , Valladares Ariel A. 
Published: April 2011

AbstractMetallic glasses are in the forefront of metallurgical research and applications. For this reason it is important to realistically model amorphous metallic systems. Some computer simulation efforts have relied on the use of parameterized classical potentials of the Lennard-Jones type or geometric hard sphere simulations, but first principles approaches have been rarely used. In this work we apply our recently developed ab initio DFT approach (A. A. Valladares et al., Eur. Phys. J. 22 (2001) 443) for the generation of amorphous semiconducting materials, to amorphize an aluminum-silicon alloy, the eutectic Al-12%Si. We report specific atomic structures and radial distribution functions (RDFs), total and partial, of one amorphous and one liquid-amorphous periodic cubic supercell of 125 atoms (15 silicons and 110 aluminums), Al-12%Si, with a volume (12.8379 Å)3, generated using the Harris functional.
Strength Measurement in Brittle Thin Films
Authors: Borrero-Lopez Oscar , Hoffman Mark , Bendavid Avi , Martin Phil J 
Published: April 2011

AbstractIn this work we have investigated the strength variability of brittle thin films (thickness ≤ 1 μm) utilising a simple test methodology. Nanoindentation of as-deposited tetrahedral amorphous carbon (ta-C) and Ti-Si-N nanocomposite films on silicon substrates followed by cross-sectional examination of the damage with a Focused Ion Beam (FIB) Miller allows the occurrence of cracking to be assessed in comparison with discontinuities (pop-ins) in the load-displacement curves. Strength is determined from the critical loads at which cracking occurs using the theory of plates on a soft foundation. This is of great relevance, since the fracture strength of thin films ultimately controls their reliable use in a broad range of functional applications.
Study on the local damage mechanisms in WC-Co hard metals during scratch testing
Authors: Ndlovu Siphilisiwe , Durst Karsten , Hoeppel Heinz Werner , Goeken Mathias 
Published: April 2011

AbstractThe effect of the cobalt content and WC grain size on the deformation behaviour of WC-Co hard metals was investigated by studying materials with a varying WC grain size and cobalt content. The WC grain size ranged from 2.65 to 0.25 µm and the binder content ranged from 6 to 15 wt%. Single and multiple scratch tests were conducted using a Nano indenter with a Berkovich diamond tip and the load ranged from 5 to 500 mN with a tip sliding velocity of 10 µm/s. Several damage mechanisms were observed and these show a combination of ductile and brittle wear. The bulk properties i.e. composite properties of the hard metal determine the wear in the 6 wt% Co samples on the other hand the 15 wt% Co samples exhibited a localised response to the wear i.e. the wear is determined by the individual phases in the hard metal.
Interfacial Characterization of Multiple Layer Coatings on Thermoplastic Olefins (TPO)
Authors: Forster Aaron M , Michaels Chris A. , Lucas Justin , Sung Lipiin 
Published: April 2011

AbstractThermoplastic olefins (TPO) have made significant inroads as polymeric materials for interior and exterior automotive parts. Spray applied chlorinated polyolefins (CPO) are often used to improve paint adhesion to the low surface energy TPO substrates. The penetration of the CPO into the substrate is difficult to quantify, but is critical to achieving a good paint/TPO bond. The interphase between each layer in a coated TPO coupon was investigated using a combination of instrumented indentation and confocal Raman microscopy. The degree of CPO interpenetration was Thermoplastic olefins (TPO) have made significant inroads as polymeric materials for interior and exterior automotive parts. Spray applied chlorinated polyolefins (CPO) are often used to improve paint adhesion to the low surface energy TPO substrates. The penetration of the CPO into the substrate is difficult to quantify, but is critical to achieving a good paint/TPO bond. The interphase between each layer in a coated TPO coupon was investigated using a combination of instrumented indentation and confocal Raman microscopy. The degree of CPO interpenetration was altered by using three different CPOs exposed to two different manufacturing methods for the same TPO and base/clear coat system. It was found that the interfaces, CPO/base coat or CPO/TPO, were chemically and mechanically sharp at the 1 μm lateral resolution of both techniques. A gradient in the modulus through the thickness of the clear coat was observed using instrumented indentation.
Modeling magnetoelasticity and magnetoplasticity with disconnections and disclinations
Authors: Mullner Peter , Geleynse Alan Steward , Carpenter David Robert , Hagler Michael Scott , Chmielus Markus 
Published: April 2011

AbstractThe magneto-mechanical properties of magnetic shape-memory alloy single crystals depend strongly on the twin microstructure which is established during the martensitic transformation, and through thermo-magneto-mechanical training. For self-accommodated martensite, twin thickness and magnetic-field-induced strain are very small. For effectively trained crystals, a single twin may comprise the entire sample and magnetic-field-induced strain reaches the theoretical limit. Furthermore, the deformation of self-accommodated martensite is pseudo-elastic (magnetoelasticity) while the deformation of effectively trained crystals is plastic (magnetoplasticity). Twin microstructures of self-accommodated martensite were modeled using disclinations which are line defects such as dislocations, however with a rotational displacement field. The defect structure was approximated in a quadrupole solution where two quadrupoles represent an elementary twin double layer unit. The twin boundary was inclined to the twinning plane which required the introduction of twinning disconnections. The shear stress-shear strain properties of self-accommodated martensite were analyzed numerically for different initial configurations of the twin boundary (i.e. for different initial positions of the disconnections). The shear stress-shear strain curve is sensitive to the initial configuration indicating that disconnection nucleation is controlling the magneto-mechanical properties of self-accommodated martensite.
Reliability of MEMS Materials: Mechanical Characterization of Thin-Films using the Wafer Scale Bulge Test and Improved Microtensile Techniques
Authors: Gaspar Joao , Schmidt Marek , Held Jochen , Paul Oliver 
Published: April 2011

AbstractThis paper reports on recent improvements of the bulge and microtensile techniques for the reliable extraction of material parameters such as the Young's modulus E, Poisson's ratio ν, plane strain modulusEps=E/(1–ν2), prestress σ0, fracture strength μ, Weibull modulusmand strain hardening coefficientsn, and on the direct comparison between the two methods. The bulge technique is extended to full wafer measurements enabling throughputs of data with statistical relevance whereas key improvements of a previous fabrication process of microtensile specimens lead now to much higher yields, approaching 100%. Both techniques are applied to an extensive set of materials, brittle and ductile, typically used in MEMS applications. These include thin films of silicon nitride, silicon oxide, polycrystalline silicon and aluminum deposited by techniques such as thermal oxidation, LPCVD, PECVD and PVD.
Microstructural and Geometrical Factors Influencing the Mechanical Failure of Polysilicon for MEMS
Authors: Jonnalagadda Krishna , Chasiotis Ioannis 
Published: April 2011

AbstractThe failure strength of polycrystalline silicon is discussed in terms of activation of critical flaws, as well as the material microstructure and inhomogeneity. The Weibull probability density function parameters were obtained to deduce the scaling of material and component strength and to identify critical flaw populations, especially when two or more flaw sets are concurrently active. It was shown that scaling of strength changes for small feature sizes, which limits the applicability of strength data from large MEMS components to self-similar small MEMS components. On the other hand, the probability of failure of small components is described by a larger Weibull material stress parameter, which makes uniaxial strength data a conservative design approach. Furthermore, according to mode I and mixed mode I/II fracture studies for polysilicon, it is concluded that microstructural inhomogeneity alone accounts for 50% scatter in strength (with reference to the minimum recorded value). Thus, the conditions for applicability of the Weibull probability density function are rather weak in polycrystalline silicon, because flaws of the same length that are subjected to the same macroscopic stresses are not always critical.
Mechanical Stress Sensors for Copper Damascene Interconnects
Authors: Delamare Romain , Blayac Sylvain , Kasbari Moustafa , Inal Karim , Rivero Christian 
Published: April 2011

AbstractWe propose embedded microsensors to investigate the mechanical stress in copper damascene lines in a standard CMOS microelectronic technology. Those sensors are based on silicon piezoresistive effect where strain in the active silicon is induced by orientated copper lines. The challenge is to correlate the electrical sensors signal directly to stress variation in lines.We have performed electrical measurements of the structures as a function of temperature. A coupled analytical and Finite Element thermomechanical Model of the structure was developed and a good agreement with measurements was obtained.
Variation in Dislocation Pattern Observed in SCS Films Fractured by Tensile Test: Effects of Film Thickness and Testing Temperature
Authors: Nakao Shigeki , Ando Taeko , Arai Shigeo , Saito Noriyuki , Sato Kazuo 
Published: April 2011

AbstractThis paper reports a transition in the fracture behavior of micron-sized single-crystal-silicon (SCS) film in an MEMS structure for various film thicknesses and ambient temperatures. The mean fracture toughness of 4-µm-thick SCS films was 1.28 MPa at room temperature (RT), and the value increased as the film thickness decreased, reaching 2.91 MPa for submicron-thick films. The fracture toughness of 4-µm-thick film did not change for ambient temperatures ranging from RT to 60ºC. However, it drastically increased at 70ºC and reached 2.60 MPa at 150ºC. Enhanced dislocation activity in the SCS crystal near the fracture surface was observed on 1-µm-thick film at RT and 4-µm-thick film at 80ºC by high-voltage electron microscopy. This change in dislocation activity seemed to correlated with the transition in fracture behavior.
Novel Differential Surface Stress Sensor for Detection of Chemical and Biological Species
Authors: Kang Kyungho , Shrotriya Pranav 
Published: April 2011

AbstractA miniature sensor consisting of two adjacent micromachined cantilevers (a sensing/reference pair) is developed for detection of chemical and biological species. A novel interferometric technique is utilized to measure the differential bending of sensing cantilever with respect to reference. Presence of species is detected by measuring the differential surface stress associated with adsorption/absorption of chemical species on sensing cantilever. Surface stress associated with formation of alkanethiol self-assembled monolayers (SAMs) on the sensing cantilever is measured to characterize the sensor performance.
A Comparative Study of the Strength of Si, SiN and SiC used at Nanoscales
Authors: Alan Tuncay , Sarro Pasqualina M. 
Published: April 2011

AbstractMicroelectromechanical systems (MEMS) are being used in many critical applications that require very high stress levels. To properly design MEMS components, mechanical properties should be characterized testing relevant sized samples that are fabricated with the same procedures as the final structure. In this paper we use atomic force microscopy (AFM) experiments to study the fracture strength statistics of polycrystalline SiC and SiN nanobeams, and compare their mechanical performance with the performance of previously tested Si nanostructures. Using the same AFM method and similar sample shape and sizes, allows a direct comparison to be made, which will be useful in determining the best material for different mechanical applications and also to validate the theoretical limits.
Spectroscopy of Chromium Doped Garnets in a Wide Temperature Range
Authors: Orucu Humeyra , Ozen Gonul , Collins John , Di Bartolo Baldassare 
Published: April 2011

ABSTRACTChromium doped garnets are tunable solid state laser materials which emit in the red and near infrared. We have studied the emission spectra of Y3Al5O12:Cr3+ (YAG:Cr), Gd3Ga5O12:Cr3+ (GGG:Cr) and Gd3Sc2Ga3O12:Cr3+ (GSGG:Cr) in a wide range of temperatures 25-800 K and have related their spectroscopic properties to the interaction between the 2E and 4T2 energy levels of the chromium ion. The measurements included absorption, lifetime, luminescence under continuous and pulsed excitations, and thermal effects on sharp lines.
Performance and Modeling of a Nanostructured Relative Humidity Sensor
Authors: Taschuk Mike , Steele John , Brett Mike 
Published: April 2011

ABSTRACTCapacitive humidity sensors were fabricated using interdigitated electrodes coated with amorphous nanostructured TiO2 thin films grown by glancing angle deposition. The sensor exhibited a large change in capacitance, increasing exponentially from ∼ 1 nF to ∼ 1 μF for an increase in relative humidity from 2 % to 92 %. A simple model of the capacitive response and dielectric constant of the devices has been developed and compared to the experimental results. From this comparison, it is clear that the magnitude of the device response observed cannot be explained with bulk dielectric constants or literature values.
Implantation and Sputtering of Ge and Si Ions into SiO2 Substrates using Electric Fields for Acceleration and Optimisation of Laser-produced Ion Streams used for Modification of Semiconductor Materials
Authors: Rosinski Marcin , Wolowski Jerzy , Yerci Selcuk , Parys Piotr , Turan Rasit , Badziak Jan , Czarnecka Agata , Gasior Pawel , Pisarek Marcin 
Published: April 2011

AbstractLaser plasma has been proved to be a potential source of multiply charged ions which could support the growing demands for high-current ion beams. To optimize efficiency of the ion implantation technology selection of proper laser beam characteristics is very important and should be investigated. With LIS, several variables can and must be controlled. The properties of ions (current densities, the ion charge state, angular and energy distributions) depend on target material and the laser energy, pulse duration and intensity on the target surface. So, the characteristics of laser-produced ion streams should be determined with the use of precise ion diagnostic methods.Based on the preliminary results for acceleration of ions produced with the use of a repetitive laser system at IPPLM the special electrostatic-acceleration system has been designed and prepared. This device permits to accelerate ions having charge states of 1+ to energies up to ∼40 keV. The movable target holder was located inside the cylindrical box connected with a high-voltage source (up to 50 kV at 50 mA). The accelerated Ge and Si ions was implanted to SiO2/Si substrates and analyzed.This contribution is concerned mainly on the analysis and optimization of laser-produced Ge and Si ion streams as well as on investigation of the direct implantation of these ions into SiO2 substrates. Targets were irradiated with the use of repetitive (up to 10 Hz) laser with energy up to 700 mJ in one pulse, at radiation intensities of ∼1011 W/cm2. The ion stream parameters were measured using the time-of-fight method. The depth of ion implantation was determined by X-Ray Photoelectron Spectroscope (XPS). After the implantation the samples were annealed in different temperatures in range of to create nanocrystal structures and then analyzed by means of Raman Spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The work has been performed within SEMINANO project supported by EC (within 6FP).
Interface Stability between Ni-P film plated by Supercritical Electroless Plating and the Polymer Substrate
Authors: Woo Byung-Hoon , Sone Masato , Shibata Akinobu , Ishiyama Chiemi , Yamagata Masahiro , Masuda Kaoru , Higo Yakichi 
Published: April 2011

ABSTRACTWe propose a novel technique for electroless plating on polymer substrates using a dense CO2 beyond the critical point. Ni-P thin films were fabricated by a novel, hybrid technique consisting of two processes: catalyzation in supercritical CO2 with Pd bis-acetylacetonate and electroless plating in emulsion with dense carbon dioxide. Catalyzation in supercritical CO2 enabled the nucleation of a large number of Pd nuclei on a polyimide substrate without chemical pretreatment, and the deposition of a uniform Ni-P metal film. The electroless plating in emulsion with dense carbon dioxide produced a uniformly plated film without peeling or nodules. The improved uniformity was attained by the solubility and diffusivity of the dense CO2 beyond the critical point in the emulsion.
UV Resistant Poly(3,4-ethylenedioxythiophene) Thin Films: Layer-by-Layer Assembly with Absorbing Nanoparticles
Authors: Dawidczyk Thomas , Grunlan Jaime 
Published: April 2011

ABSTRACTLayer-by-layer (LbL) assembly is used to create thin films by alternately exposing a substrate to positively- and negatively-charged molecules or particles in water. In recent years, LbL assemblies containing poly(3,4-ethylenedioxythiophene) (PEDOT) have been heavily studied, but little work has focused on improving the environmental stability of these thin films. Most intrinsically conductive polymers suffer from increasing resistance with exposure to ultraviolet light. In the present work, photolytic stability is improved by adding UV-absorbing nanoparticles to PEDOT assemblies. Films made by alternately depositing PEDOT-PSS and polyethylenimine (PEI) show an order of magnitude increase in sheet resistance after just 28 hours of exposure to 365 nm light. This degradation is cut in half by incorporating UV-absorbing nanoparticles, carbon black or titanium dioxide, into these assemblies. After more than 200 hours of exposure, films containing TiO2 nanoparticles have sheet resistance that is one fifth that of the unprotected PEDOT. In addition to adding UV-absorbing particles, the influence of doping and type of polycation on bulk resistivity and film growth were evaluated. These films are able to achieve bulk resistivity values below 1 Ohm cm with a thickness below 100 nm. When combined with transparency greater than 90%, these films may be useful for electrostatic dissipation layers or low conductivity electrodes in film or flexible display applications.