bluuebunny/crossref_metadata_2025_split huggingface dataset:
Micromachined Nanoparticulate Ceramic Gas Sensor Array on Mems Substrates
Authors: Heule Martin , Gauckler Ludwig J. 
Published: April 2011

AbstractIn most MEMS applications, dust and particles are avoided with considerable endeavor. However, for many applications such as gas sensors, powders of functional ceramics would often provide better performance than corresponding thin film layers. There are abundant ways to synthesize powders with well defined chemical composition, phase and size distribution, whereas the processing parameters for thin-film preparation often are limited. Specifically where the functionality is based on a chemical reaction on surfaces, nanoscaled powders with a high specific surface area have proven useful. This is the case for tin oxide gas sensors that exhibit a drop in electrical resistivity induced by the combustion of the analyte gas. Soft lithography was used for the fabrication of mesoscaled powder-based ceramic structures. In this paper, we present the integration of small tin oxide microstructures with an effective gas-sensing area of 10 by 30 νm2 on a micro-hotplate substrate. Such a substrate can heat the ceramic sensor to operating temperatures quickly with low power consumption. A whole array of sensors can be integrated on one micro-hotplate. Processing steps to prepare the sensor array on the micro hot plate are presented and discussed concerning processing sequence, sensitivity towards 1000 to 1500 ppm hydrogen and power consumption. Additionally, effects of grain growth due to on-chip annealing of the ceramic nanostructure were observed.
Charge Transport in Low Stress Si-rich Silicon Nitride Thin Films
Authors: Habermehl S. , Carmignani C. 
Published: April 2011

AbstractField dependent bulk charge transport in Si-rich, low stress silicon nitride thin films is studied in correlation to the local atomic Si-N bond strain. Across a range of film compositions varying from fully stoichiometric Si3N4 to Si-rich SiN0.54, Poole-Frenkel emission is determined to be the dominant charge transport mechanism with the Poole- Frenkel barrier height found to decrease concomitantly from 1.10 to 0.52 eV. Across the same composition range the local residual Si-N bond strain, as measured by FTIR spectroscopy, is observed to vary from 0.006 to –0.0026. Comparison of the barrier height to the residual strain reveals a direct correlation between the two quantities. It is concluded that reductions in the Poole-Frenkel barrier height are a manifestation of compositionally induced strain relief at the molecular level. Reductions in the barrier height result in increased Poole-Frenkel emission detrapping rates and consequently higher leakage currents in Si-rich films.
Mechanical Properties of Thin Film Silicon Carbide
Authors: Jackson Kamili M. , Edwards Richard L. , Dirras Guy F. , Sharpe William N. 
Published: April 2011

AbstractSilicon carbide is a very attractive material for a variety of applications. Originally considered for use in high power and high temperature electronics because of its large bandgap, designers of MEMS are now considering use of silicon carbide because of its stability at high temperatures, resistance to corrosives, high stiffness, and radiation resistance. However, as with any new structural material, its mechanical properties must be measured for design information. This research measures the elastic modulus, strength, and Poisson's ratio of two different silicon carbides using microtensile testing. One material is a 0.5-1νm thick film from Case Western Reserve University. Preliminary results give an average of 420 GPa for elastic modulus, a strength of 1.2 GPa, and a Poisson's ratio of 0.19. The second material is from Massachusetts Institute of Technology with an average thickness of 30 microns. Preliminary results show an elastic modulus of 430 GPa, a strength of 0.49 GPa, and a Poisson's ratio of 0.24. In addition to the most recent results, techniques used to obtain these results, microstructure investigations, and a comparison of the materials are detailed.
Add Ceramic “MEMS” to the Pallet of MicroSystems Technologies
Authors: Wilcox David L. , Burdon Jeremy W. , Changrani Rajnish , Chou Chia-Fu , Dai Steve , Koripella Ramesh , Oliver Manny , Sadler Daniel , Allmen Paul von , Zenhausern Frederic 
Published: April 2011

AbstractJust as the 40+ years of technology developments associated with the electronic application of semiconductor fabrication processes is “morphing” into a micro-electro- mechanical systems (MEMS) technology in the past dozen years or so, so it seems may the “mature” multilayer ceramic fabrication technology associated with capacitor components and interconnect substrates for the integrated circuit industry, be morphed into MEMS – microsystems technology applications. This paper highlights work underway in Motorola Labs aimed at exploring the potential to develop 3D multilayer ceramic structures to integrate (monolithic and hybrid) multiple functions to create microsystems for wireless, energy and life science applications. By multiple functions, we refer to the ability for a microsystem to perform electronic, fluidic, thermonic, photonic and mechatronic (or actuator) based functions. Current capabilities of the multilayer ceramic materials and processes to achieve integrated functionalities for wireless applications will be described including the development of a new dielectric enabling increased performance for wireless applications. Also to be highlighted will be exploratory microscale fuel cell prototypes exploiting advances in the multilayer ceramic lamination and feature forming technologies enabling the insertion of 3D microchannels for microfluidic functions. These prototypes also feature the ability of the technology to provide thermonic functionality for microreactor devices. Feasibility of a light source that can be integrated into the technology platform hinting at photonic applications will be described. Many materials science and engineering advancements are needed to achieve the potential of this “old” but newly “morphing” technology and some of these will be noted.
Heavy-Ion Damage to Magnesium Diboride Films: Electrical Transport-Current Characterization
Authors: Kerchner H. R. , Cantoni C. , Paranthaman M. , Christen D. K. , Christen H. M. , Thompson J. R. , Miller D. J. 
Published: April 2011

ABSTRACTThe use of magnesium diboride in superconducting magnets, transmission lines, or other large-scale applications depends on the transport-current characteristics of this material in magnetic field, and how they compare to the properties of conventional and high-temperature superconductors. Thin films of boron grown on sapphire substrates during electron-beam evaporation were exposed to Mg vapor to produce 0.5-μm thick layers of the metallic compound MgB2. Four-terminal measurements of their voltagecurrent relations, E(J), were carried out before and after exposure to Bφ =1-T and higher doses of 1-Gev U ions. These doses lowered critical temperatures Tc≈39 K less than 0.1 degree, raised the normal-state resistivity, and reduced the loss-free critical current density, Jc. Higher doses added little. The reduction of current densities was greater in the presence of applied magnetic field greater than 0.1 T.
Structure Characteristics of ISD Coated Conductors
Authors: Tang Y. L. , Miller D. J. , Ma B. , Koritala R. E. , Balachandran U. 
Published: April 2011

ABSTRACTThe inclined-substrate deposition (ISD) method for growth of biaxially textured MgO is of interest due to its applications in coated conductors based on high-temperature superconductor (HTS). The ISD method is especially attractive since it offers the potential to produce a high–quality biaxially textured layer in a simple and efficient process. In this work, Yba2Cu3O7-x (YBCO) coated conductors based on two-step deposited MgO buffer layers (ISD and homoepitaxial) on Hastelloy tapes were examined by high-resolution electron microscopy (HREM) to study both the structure of individual layers and, especially, the interfaces between them. Special attention was paid to the MgO buffer layer because of its importance to biaxial YBCO formation. TEM investigation shows the MgO [111] direction is not parallel to the substrate normal but tilted slightly toward the deposition direction. The second layer of MgO has a good epitaxial relationship with the first layer, while dislocations were found near the interface area of the MgO layers. Twin boundaries, which are in the (111) plane, were found between the ISD MgO columns. The multi-buffer layers gave better growth of epitaxial YBCO.
Spatial Distribution Analyses of Superconducting Transition Temperature in Epitaxial YBa2Cu3O7 Film Using Variable Temperature Scanning Laser Microscopy
Authors: Seo S. , Kwon C. , Park B. H. , Jia Q. X. 
Published: April 2011

ABSTRACTThe spatial distribution of superconducting properties using variable temperature scanning laser microscope (VTSLM) has been investigated. The superconducting thin film used in this study is an epitaxial YBa2Cu3O7 film photolithographically patterned to a 300 μm-wide bridge. Since the voltage response, δV(x,y) is proportional to dR/dT(x,y), the spatial distribution of superconducting transition can be obtained in VTSLM images. In the resistive transition region, there is a strong correlation between the VTSLM images and the resistance of the sample. With decreasing resistance, the area with large δV(x,y) shifts toward the ends of the bridge. This indicates that the resistive transition is not uniform and both ends of the bridge have lower transition temperature, Tc. Different currents or different output power of lasers do not affect the images. VTSLM technique is a powerful tool to image the local superconducting properties and to identify the weaker superconducting areas.
Thermodynamic Calculations in New Thermoelectric Materials. Application to Processes
Authors: Tedenac J.C. , Record M.C. , Izard V. 
Published: April 2011

ABSTRACTThe processing of electronic materials and devices is an important field of application of thermodynamics. Many growth processes of semi-conductors involve vapour-solid or liquid-solid interfaces which can be considered close to the thermodynamic equilibrium. Performance enhancement of thermoelectric modules can be obtained by a good knowledge of the constitution of the materials involved in their fabrication. Its requires a relevant thermodynamic analysis of the material.Making these optimized thermoelectric materials require at least three elements being thermoelectric materials typically multicomponent systems which are usually studied by a CALPHAD analysis of the relevant systems. All these problems are related to the thermodynamic quantities of species involved in the materials such as activities and free energy functions of electrons, holes and components.In this paper we present a contribution to a better understanding of antimony based thermoelectric materials by a CALPHAD approach.
Thermoelectric Properties of Eu-doped CoSb3
Authors: Lamberton G. A. , Tedstrom R. H. , Tritt Terry M. , Nolas G. S. 
Published: April 2011

ABSTRACTResistivity and thermopower data is presented on Eu-doped CoSb3 skutterudites over the temperature range of 10 K to 700 K. Thermal conductivity is also presented from 10 K to 300 K in order to determine the figure of merit. Eu0.43Co4Sb11.59Ge0.31 and Eu0.42Co4Sb11.37Ge0.50 exhibit an enhanced figure of merit as compared to CoSb3 and Eu0.2CoSb3. Data on a series of Yb-filled CoSb3 is underway and preliminary data is presented.
Synthesis and Thermoelectric Properties of CoP3
Authors: Shields Virgil B. , Caillat Thierry 
Published: April 2011

ABSTRACTIn an effort to expand the range of operation for highly efficient, segmented thermoelectric unicouples currently being developed at the Jet Propulsion Laboratory (JPL), skutterudite phosphides are being investigated as potential high temperature segments to supplement antimonide segments that limit the use of these unicouples at a hot-side temperature of about 873-973 K. We report here on the synthesis and transport properties of one of these phosphide skutterudite materials, CoP3. Large amounts of cobalt triphosphide have been prepared by direct reaction from stochiometric powders at synthesis temperatures ranging from 873 to 1223 K. The synthesized powders were analyzed by x-ray diffractometry and hot pressed at 1273 K. The samples were analyzed by microprobe analysis and electrical conductivity, Seebeck voltage and thermal conductivity measurements were performed. The thermoelectric properties are presented and discussed as a function of temperature up to 1000 K. Initial thermal stability results are presented to assess the potential of this material for high temperature operation.
Reductions in the Lattice Thermal Conductivity of Ball-milled and Shock compacted TiNiSn1−XSbXHalf-Heusler alloys
Authors: Bhattacharya S. , Xia Y. , Ponnambalam V. , Poon S.J. , Thadani N. , Tritt T.M. 
Published: April 2011

ABSTRACTHalf-Heusler alloys are currently being investigated for their potential as thermoelectric materials [1], [2]. They exhibit high negative thermopower (40-250μV/K) and favorable electrical resistivity (0.1-8mW•cm) at room temperature. Attractive power factors (α2σT) of about (0.2-1.0W/m•K) at room temperature and about 4W/m•K at 600K [3] have been reported in these materials. But in order to achieve a high figure-of-merit in the half-Heusler alloys, the relatively high thermal conductivity in these materials (∼ 10 W/m•K) must be reduced. The thermal conductivity in these materials is composed of mainly a lattice contribution, compared to a very small electronic component. The challenge is to reduce the relatively high lattice thermal conductivity in these materials. Reported in this paper is a significant reduction of lattice thermal conductivity (∼1.5 - 3.5W/m•K) in some Ti-based half-Heusler alloys. Samples have been prepared by ball milling and followed by shock-compaction that has resulted into reduced grain sizes in these materials. The effects of the microstructure on the thermal transport properties of the Half-Heusler alloys have been investigated and are presented and discussed herein.
Temperature and Thickness Dependences of Thermoelectric Properties of PbS/EuS Bilayers
Authors: Rogacheva Elena I. , Grigorov Sergey N. , Tavrina Tatyana V. , Nashchekina Olga N. , Vekhov Yegor O. , Sipatov Alexander Yu. , Volobuev Valentine V. , Dresselhaus Mildred S. 
Published: April 2011

ABSTRACTA non-monotonic character of the dependences of the thermoelectric properties of PbS/EuS/(001)KCl heterostructures on the PbS layer thickness d (d = 2 – 200 nm) was detected. Pronounced extrema at d ∼ 15 nm and less distinct extrema at d ∼ 30 nm and d ∼ 100 nm were observed. It is suggested that the complex character of the dependences is caused by the competition between percolation phenomena and size quantization. The critical exponent for the electrical conductivity (t = 1.6 ± 0.15) is determined.
The Performance of a Segmented Thermoelectric Convertor Using Yb-Based Filled Skutterudites and Bi2Te3-Based Materials
Authors: Matsubara Kakuei 
Published: April 2011

ABSTRACTThis paper reports an overview of the current state in our research program started in 1995 in collaboration with industries. This program has been aimed at making sure of the feasibility of a thermoelectric convertor for waste heat recovery of gasoline engine vehicle. Major results obtained include: (1) updated ZT-values for Pd,Pt-doped CoSb3 and partially Yb-filled skutterudite antimonides YbyM4Sb12 (M=Co, Fe, Ni; 0<y<1), (2) the performance of thermoelectric convertor using a segmented module of the skutterudites and Bi2Te3-based alloys, (3) a preliminary test of a thermoelectric stack which is the united device of thermoelectric modules and heat exchanger, when properly installed in a 2000cc class automobile.
Precise control of CVD-ZrO2 film properties based on kinetic information.
Authors: Kawamoto Takashi , Shimogaki Yukihiro 
Published: April 2011

AbstractZrO2 films were investigated as high-k gate insulators for possible gate dielectric applications. These thin films were deposited by chemical vapor deposition (CVD). We had investigated kinetics of ZrO2-CVD reaction system and thermal stability of ZrO2 film deposited from zirconium-tetra-tertiary-butoxide (ZTB) and tetrakis-diethylamio-zirconium (TDEAZ) as Zr source. In the case of ZTB, ZTB decomposed into two active intermediate precursors by gas phase reaction. These intermediate precursors also contributed to the film growth. The step coverage, the contents of carbon and oxygen, and film structures depended on the growth precursor contributed to the film growth. Film structures also depended on the deposition temperature. As the films subjected to the rapid thermal oxidation annealing, the film structure changed amorphous into cubic and then into monoclinic. However, in the case of the films deposited at 300°C, the film structure kept amorphous state after 900°C annealing. On the other hand, in the case of TDEAZ, TDEAZ directly deposited on the growing surface and the decomposition of TDEAZ by gas phase reaction did not exist. The films deposited by TDEAZ contained more carbon than by ZTB. The film structure kept amorphous state independent of the deposition temperature. As the films subjected to the rapid thermal oxidation annealing, the film structure changed amorphous into monoclinic and then into amorphous again. This structural change resulted from the decrease of the impurity contents of the residual nitrogen and the residual carbon and the increase of the content of silicon diffused from the substrate in the ZrO2 films.
Nanostructured Ultrathin Films of Silicate Clay and Polyelectrolytes: Deposition Parameters and Mechanical Properties by Nanoindentation
Authors: Fan Xiaowu , Advincula Rigoberto C. 
Published: April 2011

AbstractRecently, we have investigated the electrostatic layer-by-layer (ELBL) deposition of polycation and clay platelet ultrathin films. We have investigated the properties of these films using techniques such as ellipsometry, X-ray diffraction and atomic force microscopy (AFM). In this work, we report our results regarding the formation of this type of hybrid ultrathin films focusing on their mechanical properties as probed by nanoindentation experiments. Structural information such as film thickness, platelet coverage, surface morphology, roughness, etc., is important parameters for their potential use as coatings. We have investigated the relationship of several of these parameters with their mechanical hardness and modulus properties as a function of indentor probe depth in nanoindentation experiments. The ultrathin films have remarkable mechanical properties very different from most polymer ultrathin films.
Cross-sectional phase analysis of single crystalline silicon indented by Rockwell indenter
Authors: Kim Sung-Soon , Oh Han-Seog , Jeong Seong-Min , Lee Hong-Lim 
Published: April 2011

AbstractThis study of the indentation behavior of Si has revealed a complex process of mechanical deformation. As loading time increased, Si-XII and Si-III disappeared and only a-Si appeared in (111) samples. As loading time increased, crack was generated and residual stress was removed. At fast loading rate, the deformation behavior appears predominantly elastic. On the contrary, at slow loading rate, catastrophic plastic deformation occurred during loading stage.We have observed crack behavior which occurred under spherical indentation in crystalline silicon. Method which was used in our research for cross-sectional observation exaggerated generation and propagation of cracks. Our method prepares to observe crack behavior. But it is not profit to observe to phase transformation
Assessment of Microscale Test Methods of Peeling and Splitting along Surface of Thin-Film/Substrates
Authors: Wei Y. 
Published: April 2011

AbstractPeel test methods are assessed through being applied to a peeling analysis of the ductile film/ceramic substrate system. Through computing the fracture work of the system using the either beam bend model (BB model) or the general plane analysis model (GPA model), surprisingly, a big difference between both model results is found. Although the BB model can capture the plastic dissipation phenomenon for the ductile film case as the GPA model can, it is much sensitive to the choice of the peeling criterion parameters, and it overestimates the plastic bending effect unable to capture crack tip constraint plasticity. In view of the difficulty of measuring interfacial toughness using peel test method when film is the ductile material, a new test method, split test, is recommended and analyzed using the GPA model. The prediction is applied to a wedge-loaded experiment for Al-alloy double-cantilever beam in literature.
Superlubricity and Wearless Sliding in Diamondlike Carbon Films
Authors: Erdemir Ali 
Published: April 2011

AbstractDiamondlike carbon (DLC) films have attracted great interest in recent years mainly because of their unusual optical, electrical, mechanical, and tribological properties. Such properties are currently being exploited for a wide range of engineering applications including magnetic hard disks, gears, sliding and roller bearings, scratch resistant glasses, biomedical implants, etc. Systematic studies on carbon-based materials in our laboratory have led to the development of a new class of amorphous DLC films that provide extremely low friction and wear coefficients of 0.001 to 0.005 and 10-11 to 10-10 mm3/N.m, respectively, when tested in inert-gas or high-vacuum environments. These films were produced in highly hydrogenated gas discharge plasmas by a plasma enhanced chemical vapor deposition process at room temperature. The carbon source gases used in the deposition of these films included methane, acetylene, and ethylene. Tribological studies in our laboratory have established a very close correlation between the composition of the plasmas and the friction and wear coefficients of the resultant DLC films. Specifically, the friction and wear coefficients of DLC films grown in plasmas with higher hydrogen-to-carbon ratios were much lower than films derived from source gases with lower hydrogen-to-carbon ratios. Fundamental tribological and surface analytical studies have led us to conclude that hydrogen (within the film, as well as on the sliding surfaces) is extremely important for the superlubricity and wearless sliding behavior of these films. Based on these studies, a mechanistic model is proposed to explain the superlow friction and wear properties of the new DLC films.
Preferential Adhesion of Gold Nanoparticles Using Lithographically Patterned Substrates
Authors: Pihl Johan , Kabir Mohammad S. , Magnus S.H. 
Published: April 2011

AbstractA method of aligning small amounts of colloidal particles between narrowly spaced electrodes using a combination of conventional nanofabrication and self-assembled monolayers has been developed. Transport measurements were performed on several devices
Magnetic Interactions in Fe Nanoparticle Arrays
Authors: Farrell D. , Yamamuro S. , Ijiri Yumi , Majetich S. A. 
Published: April 2011

AbstractThe preparation of monodisperse Fe nanoparticles and self-assembly into hcp and fcc or fcc-like arrays is described. Here dipolar interactions dominate for the interparticle spacings studied (1.4-3.4 nm). Comparison of the low temperature magnetic properties of multilayer arrays with those of dilute suspensions of the same particles show increased coercivity and slower magnetic relaxation in the arrays. Mean field calculations of magnetic interaction fields suggest the type of ordered structures formed.