bluuebunny/crossref_metadata_2025_split huggingface dataset:
Advanced Excimer-Laser Recrystallization Technology for Crystal-Si Thin-Film Devices
Authors: Matsumura Masakiyo 
Published: April 2011

AbstractThis paper reviews an excimer-laser annealing (ELA) method of Si thin-films on glass studied in the Tokyo Institute of Technology, aiming at position-controlled ultra-large grain growth with high packing density by a single shot irradiation of a laser-light pulse. Key concepts are (I) 2-D modulation of the laser light intensity on the sample surface, (II) reduction of the heat removal rate from the molten Si thin layer of high temperature, and (III) enlargement of the effective specific-heat while keeping the effective thermal-conductivity low for annealed layers. There were two possible solutions for the condition (I). The first solution is of an application of a cross-coupled phase-shifter formed on a transparent quartz plate. The second solution is of a half-tone phase-modulation method (PAMELA method) using semi-transparent thin films on quartz substrate with phase-shifter. The condition (II) is satisfied by changing the SiO2 underlayer to the porous or organic silica underlayer for reducing vertical heat flow flux to the cool underlayer, and by thinning the Si layer for reducing heat flow flux along the highly conductive Si layer. The condition (III) is satisfied, by the SiON capping layer for a KrF excimer laser, and by the SiOC capping layer for a XeCl excimer laser, since they have a reasonable light absorption coefficient, low thermal conductivity, large specific-heat and sufficient heat tolerance.
A New Poly-Si TFT Employing XeCl Excimer Laser Annealing with Pre-patterned Al Laser Beam Mask
Authors: Han Min-Koo , Jung Sang-Hoon , Jeon Jae-Hong 
Published: April 2011

AbstractWe report new lateral grain growth mechanism by XeCl excimer laser annealing on a-Si film with pre-patterned Al layer. 2000Å-thick Al pattern on 800Å-thick PECVD a-Si film successfully reflects the incident laser beam and results in temperature gradient during the recrystallization process. The TEM images show that grain growth near the boundary between the liquid and the solid region exhibits a different mechanism compared with the conventional ELA. About 1.5 m-long lateral grain has been successfully obtained by single laser irradiationA poly-Si TFT with single grain boundary in the channel has been fabricated by the proposed excimer laser annealing. An excellent device characteristics such as mobility more than 250cm2/Vsec, high On/Off current ratio of 6.3×106 and low threshold voltage less than 1 V has been obtained. The experimental results show that the mobility, threshold voltage and sub-threshold slope of proposed TFTs are superior to those of the conventional TFTs.
Polycrystalline Lead Iodide Films: Optical, Electrical and X-ray Counting Characterization
Authors: Fornaro L. , Saucedo E. , Mussio L. , Gancharov A. , Guimaraes F. , Hernandes A. 
Published: April 2011

AbstractLead iodide purified by zone refining and repeated sublimation was used for growing Polycrystalline films by physical vapor deposition. Palladium film was deposited as rear contact onto glass and alumina substrates 2.5 × 2.5 cm2 in size. Onto it, lead iodide polycrystalline films were grown by sublimation at 390 °C and 5 × 10−5 mm Hg, substrate temperatures of about 200 °C and deposition times of about 10 days. Film thickness was measured by X-ray transmission at 59.5 keV giving values from 35 to 50 μm (5%). Optical and atomic force microscopy were performed to the films giving an average grain size of (80±20) μm. Low temperature photoluminescence was performed and peak position and broadness confirmed the high purity of starting materials. Films were characterized by X-ray diffraction, giving an [ΣI (0 0 l)] / [ΣI (h k l)] relation of 0.8 that indicates a strong growth preferred orientation along c axis. Front palladium thermal deposition contacts and acrylic encapsulation were done and apparent resistivity (2 × 1014 Ω. cm) and current density (7 pA/cm2 (30 V)) were obtained. X-ray film response was checked by irradiating with 241Am and an X-ray beam. Finally, film and detector characterizations were correlated with starting material, deposition parameters and previous results for the same and alternative materials like mercuric iodide.
Properties of ZnO Thin Films Deposited by Spray Pyrolysis and Magnetron Sputtering
Authors: Nunes Patrícia , Fortunato Elvira , Martins Rodrigo 
Published: April 2011

AbstractIn this work we present a study of the properties of ZnO thin films produced by spray pyrolysis and r.f. magnetron sputtering. Before the annealing treatment the properties of the films are very similar, which means that the films produced by both techniques could be used on optoelectronic devices. However spray pyrolysis is a more simple and cheap technique than sputtering, but with this last technique the thin films exhibit a higher uniformity.
Self-Assembly CoSi2-Nanostructures for Fabrication of Schottky Barrier MOSFETs on SOI
Authors: Kluth Patrick , Zhao Qing-Tai , Winnerl Stephan , Mantl Siegfried 
Published: April 2011

AbstractA new self-assembly patterning method for generation of epitaxial CoSi2 nanostructures was used to fabricate 70 nm gate-length Schottky barrier metal oxide semiconductor field effect transistors (SBMOSFETs) on silicon-on-insulator (SOI) substrates. This technique involves only conventional optical lithography and standard silicon processing steps. It is based on anisotropic diffusion of Co/Si atoms in a strain field during rapid thermal processing. The strain field is generated along the edges of a mask consisting of 20 nm SiO2 and 300 nm Si3N4. Single-crystalline CoSi2 layers grown by molecular beam allotaxy (MBA) on thin SOI substrates were patterned using this technique. During rapid thermal oxinitridation (RTON) of the masked silicide structure, a well defined separation of the silicide layer forms along the edge of the mask. These highly uniform gaps define the channel region of the fabricated device. The separated silicide layers act as metal source and drain. During the RTON-step a 6 nm thin SiO2 is formed on top of the gap which is used as a gate oxide. The SBMOSFETs can be driven as both p-channel and n-channel devices without complementary substrate doping and show good I-V characteristics.
Microsensors for Automotive Applications – Metrology and Test
Authors: Flik Gottfried , Eisenschmid Heinz , Raudzis Carsten , Schatz Frank , Schoenenborn Winfried , Trah Hans-Peter 
Published: April 2011

AbstractAccording to market surveys automotive microsensors will evolve into a multi-billion dollar business by 2005. Key roles are attributed to inertial sensors for passenger safety systems, and mass flow and pressure sensors for engine management systems. Thin film techniques together with silicon bulk or surface micromachining have been established as preferential processes to achieve reduction of sensor size, weight and cost along with improvements of sensor functionality and reliability. Enhanced sensor performance often pushes the limits of process technology and therefore the need arises very early in the MEMS design process to identify materials and geometry related parameters which are critical with respect to their tolerance band specifications. In order to control these critical parameters, automated wafer level test procedures need to be developed (based preferentially on electrical quantities) and additionally considered for in the sensor design phase (design for test). In analogy to microelectronics 2D wafer maps of critical parameters may give hints on how to improve process stability and how to adapt the sensor design in order to optimize yield. Examples of critical model parameter variations include thermal conductivity, thickness, and shear modulus of thin films.
Mechanisms of Fatigue in Polysilicon Mems Structures
Authors: Shrotriya P. , Allameh S. , Butterwick A. , Brown S. , Soboyejo W.O. 
Published: April 2011

AbstractFatigue crack initiation is shown to be associated with the stress-assisted evolution of a surface silica layer that forms during the normal exposure of unpassivated polysilicon surfaces to lab air In-situ atomic force microscopy (AFM) techniques are used to reveal the evolution of overall surface topology during incremental cyclic deformation to failure. Linear perturbation analysis of stress-assisted dissolution is then utilized to predict the evolution of the surface morphology. The predictions from the perturbation analysis are shown to be consistent with measured surface morphologies obtained using AFM techniques.
Characteristics of Thick Sol-Gel Lead Zirconate Titanate Films for Angular Rate Sensor Application
Authors: Lee S. H. , Iijima T. , Nakamura K. , Tanaka S. , Esashi M. 
Published: April 2011

AbstractIn this study, thick sol-gel PZT(Pb(Zr1−xTix)O3) films were fabricated and their characteristics were investigated for angular rate sensor applications. The crack-free thick sol-gel PZT films were successfully deposited on silicon substrates by multiple spin-coating technique combined with rapid thermal annealing(RTA). The thickness of the PZT films is 1.5 νm, which is required by a vibration angular rate sensor for a good actuation and sensing. The remnant polarization of the PZT films is 12.0νC/cm2. The PZT films were applied to the vibration angular rate sensor structure, and the vibration of 1.78νm in amplitude at the resonant frequency of 35.8kHz was obtained. In this case, the driving voltage of 5Vp-p by bulk piezoelectric materials was applied to the driving electrode with out of phase signal through voltage and inverting amplifier.The oscillating output voltage obtained by external actuation using a stacked piezo-actuator showed the values of 0.76V and 0.87V in outer/inner driving electrode at driving voltage of 5Vp-p.
A Constitutive Model for the Mechanical Behavior of Single Crystal Silicon at Elevated Temperature
Authors: Moon H.-S. , Anand L. , Spearing S. M. 
Published: April 2011

AbstractSilicon in single crystal form has been the material of choice for the first demonstration of the MIT microengine project. However, because it has a relatively low melting temperature, silicon is not an ideal material for the intended operational environment of high temperature and stress. In addition, preliminary work indicates that single crystal silicon has a tendency to undergo localized deformation by slip band formation. Thus it is critical to obtain a better understanding of the mechanical behavior of this material at elevated temperatures in order to properly exploit its capabilities as a structural material. Creep tests in simple compression with n-type single crystal silicon, with low initial dislocation density, were conducted over a temperature range of 900 K to 1200 K and a stress range of 10 MPa to 120 MPa. The compression specimens were machined such that the multi-slip <100> or <111> orientations were coincident with the compression axis. The creep tests reveal that response can be delineated into two broad regimes: (a) in the first regime rapid dislocation multiplication is responsible for accelerating creep rates, and (b) in the second regime an increasing resistance to dislocation motion is responsible for the decelerating creep rates, as is typically observed for creep in metals. An isotropic elasto-viscoplastic constitutive model that accounts for these two mechanisms has been developed in support of the design of the high temperature turbine structure of the MIT microengine.
Superconducting Properties of High-Jc MgB2 Coatings
Authors: Christen D. K. , Cantoni C. , Thompson J. R. , Paranthaman M. , Chisholm M. F. , Kerchner H. R. , Christen H. M. 
Published: April 2011

ABSTRACTWe report the fabrication and superconducting properties of ∼0.5 μm thick, fine-grained polycrystalline coatings of MgB2 on single-crystal substrate surfaces. The films exhibit large critical current densities, implying little effect from the grain boundaries. Analyses for thermal activation effects are inconclusive, and evidence is presented that the irreversibility line is dominated by the combined influences of Hc2 anisotropy and polycrystallinity. Comparative studies of the magnetic persistent currents and electrical transport properties reveal excellent agreement over a wide range of temperature and magnetic field. This result is contrary to similar comparisons on high-temperature cuprates, where disparities arise from the effects of large flux creep and the diverse electric field regimes probed by the two techniques. The MgB2 films exhibit extremely sharp voltage-current relations away from the irreversibility line, in qualitative agreement with observed large Jc values and low rates of magnetic flux creep.
The Synthesis and Performance of MgB2
Authors: Meng R. L. , Lorenz B. , Xue Y. Y. , Pham D. , Cmaidalka J. , Meen J. K. , Sun Y. Y. , Chu C. W. 
Published: April 2011

ABSTRACTWe have studied the kinetics of the chemical reaction between Mg and B by differential thermal analysis. There are two exothermal peaks observed at 500 and 650 °C. We speculate that the first exothermal peak is mainly related to the chemical reaction between Mg and oxygen, forming MgO. The second exothermal peak, which coincides with the melting point of Mg, clearly indicates the chemical reaction between Mg and B. The effect of synthesis conditions and defects on the transport property of MgB2 has been investigated. A correlation between the microstrain, the lattice parameters, and the Mg concentration were observed and are discussed.
Bond-Length Fluctuations in the Copper-Oxide Superconductors
Authors: Goodenough John B. 
Published: April 2011

ABSTRACTThe phase diagram of La2-xSrxCuO4 is interpreted. From the virial theorem, it is argued that the cross-over from localized to itinerant electronic behavior in the range 0 < x < 0.3 is characterized by fluctuations between two equilibrium Cu-O bond lengths. Cooperative local fluctuations give rise to one-hole correlation bags of 5 to 6 copper centers on the underdoped side, to strong-correlation fluctuations in an itinerant-electron matrix on the overdoped side. Spinodal phase segregation between an antiferromagnetic, insulating parent phase and the superconductive phase occurs in the underdoped compositions, between the superconductive phase and the metallic overdoped phase on the other side of the phase diagram. Ordering of the fluctuations into a travelling bipolaronic charge-density/spin-density wave of composition x ≈?1/6 yields heavy fermions of symmetry (x2− y2) coexisting with light electrons; the high-temperature superconductive pairs are condensed out from the heavy fermions.
Real-time Degradation Study of HgBa2CaCu2O6+δ?Thin Film Using Near-field Scanning Microwave and Optical Dual Probe
Authors: Aga Roberto S. , Xie Yi-Yuan , Wu Judy Z. 
Published: April 2011

ABSTRACTAll high- Tc superconductors are susceptible to humid environment. The mechanism behind this degradation process is not yet well known or even described. In an attempt to understand the mechanism, we studied the real-time degradation process of HgBa2CaCu2O6+δ (Hg-1212) thin film using scanning probe microscopy (SPM) techniques. A newly developed near-field scanning microwave and optical dual probe was employed to map simultaneously the spatial variation of microwave sheet resistance and optical transmittance of a sample. Mapping was performed at a regular time interval while the sample was exposed to a very high level of humidity (85%-90%). In a separate experiment, atomic force microscope (AFM) was used to monitor the surface roughness of a sample subjected to the same level of humidity. Results indicate that the degradation process of Hg-1212 involves the gradual transformation of the material into a colorless insulator accompanied by continuous surface deformations.
Preparation of Bi-2212/Ag Tapes by Electrodeposition
Authors: Chen Jun , Bhattachary Raghu , Padmanabhanl Ramakrishnan , Blaugher Richard 
Published: April 2011

ABSTRACTBi-2212 precursor films were deposited on both sides of polycrystalline Ag tapes by electrodeposition. After a melt-solidification process in flowing oxygen atmosphere, c-axis textured Bi-2212 films with Jc( 0T, 4.2K) up to 820,000 A/ cm2 were obtained. A post annealing in flowing nitrogen at 475°C for 25 minutes increased Tc from 72 K to 92 K, and Jc(H=0T) > 17, 000A/ cm2 was observed at 60 K. No scaling behavior of the pinning force was observed, indicating more than one pinning mechanism in thus obtained Bi-2212/Ag tapes.
Preparation and Electronic Device Properties of Single Crystalline La2−xSrxCuO4Superconducting Film
Authors: Islam A. T. M. Nazmul , Ashizawa K. , Watauchi S. , Tanaka I. 
Published: April 2011

ABSTRACTWe have grown La2−xSrxCuO4 single-crystalline films on atetra-axis oriented Zn doped La2CuO4 single crystals by IR-LPE technique. The films show thickness dependence of Tc,onset, but films of thickness below 80μm doesn't show zero resistance down to 4.2K. The I-V characteristics showed reduced voltage jump than usual and small hysteresis. This phenomenon resembles with the characteristics of resistively and capacitively shunted intrinsic Josephson junctions (RCSJ)
Thermoelectric Potential of Bi and Bi1−x Sbx Nanowire Arrays
Authors: Dresselhaus M. S. , Lina Y.-M. , Rabin O. , Cronin S. B. , Black M. R. , Ying J. Y. 
Published: April 2011

ABSTRACTThe potential of Bi and Bi1−x Sbx nanowire arrays for thermoelectric applications is discussed. The advantages of bismuth as a low dimensional thermoelectric material are enumerated and the role of modeling is emphasized. The advantages of using the Sb concentration as well as the wire diameter as materials parameters for optimizing the thermoelectric performance of these nanowires are discussed, with particular emphasis given to the development of a high performance p-type nanowire thermoelectric material.
Molecular-dynamics studies on solid phase epitaxy of guest-free silicon clathrates
Authors: Munetoh Shinji , Moriguchi Koji , Motooka Teruaki , Kamei Kazuhito 
Published: April 2011

ABSTRACTDynamical phenomena during the solid phase epitaxy (SPE) of guest-free Si clathrates (Si34 and Si46) via molecular-dynamics (MD) simulations using the Tersoff potential have been reported. The activation energy of SPE for Si34 has been found to correspond with the experimental value for the cubic diamond phase (c-Si; approximately 2.7eV), while the SPE rates of Si46 are much lower than that of c-Si. The structural transition from Si46 (type-I) to Si34 (type-II) can be also observed during the Si46 [001] SPE. The present results suggest that it is worthwhile to intensify experimental studies concerning crystal growth techniques of clathrate materials and these interesting Si forms may open up a new field in “silicon technologies”.
Electrical Transport Properties of Rare Earth Doped Pentatellurides
Authors: Lowhorn Nathan D. , Tritt Terry M. , Littleton R. T. , Abbott Edward E. , Kolis J. W. 
Published: April 2011

ABSTRACTThe transition metal pentatellurides HfTe5 and ZrTe5 exhibit a broad resistive anomaly as a function of temperature. This behavior is also reflected in the thermopower as it changes from a large positive value below room temperature to a large negative value at lower temperatures with the zero crossing corresponding well with the peak temperature of the resistive anomaly. The large values of the thermopower at low temperatures (T ≈ 150 K) have made these materials attractive for investigation for potential low temperature thermoelectric applications. The magnitude of the resistive peak and the peak temperature are highly sensitive to doping as well as external influences such as magnetic field and pressure. In this study we examine the effect of doping with various rare earth elements (RE = Ce, Sm and Dy) and the subsequent effects on the electrical resistivity and the thermopower. These results will be discussed in relation to the thermoelectric performance of these materials.
Mechanical Characterization of Functionally Graded Materials with a Yield Strength Gradient
Authors: Nayebi A. , Mauvoisin G. , Bartier O. , Abdi R. El 
Published: April 2011

AbstractAn elasto-plastic spherical indentation study on materials with a yield strength gradient, like steels which have undergone thermal hardening such as nitriding, is carried out using both experimental and finite element methods. A theory based on the evolution of hardness, is proposed to determine the yield stress and hardness profiles for materials with a decreasing yield stress with depth.Results for carbo-nitriding steels obtained by the standard Vickers micro hardness technique are compared with those obtained by the proposed method.
Characterization of the Degraded Microstructures of a Platinum Aluminide Coating
Authors: Kim Hyungjun , Walter Mark E. 
Published: April 2011

AbstractTo investigate phase evolution of β-(Ni,Pt)Al/γ-(Ni3Al) in thermal barrier coating bond coat systems, specimens were subjected to 1200°C cyclic and isothermal heating. By removing the thermally grown oxide (TGO) after every 10 hours of heating, aluminum (Al) depletion from the bond coat was accelerated. Non-accelerated and accelerated Al-depletion samples were examined with scanning electron microscopy after every 10 hours of cyclic and isothermal heating. Observations from after the first 10 hours of thermal exposure show distinct microstructural differences. After 50 hours of heating, cyclic accelerated Al-depletion samples show more distinct grain boundaries and a higher proportion of-(Ni3Al) phase than isothermalaccelerated Al-depletion samples. Through instrumented micro-indentation, trends in elastic modulus were determined for isothermal and cyclic accelerated Al-depletion specimens.
Functionally Graded Materials produced with High Power Lasers
Authors: Hosson Jeff Th. De , Pei Yutao 
Published: April 2011

AbstractWith a well-controlled laser melt injection (LMI) process, for the first time the feasibility is demonstrated to produce SiC particles (SiCp) reinforced Ti6Al4V functionally graded materials (FGMs). SiCp are injected just behind the laser beam into the extended part of the laser melt pool that is formed at relatively high beam scanning velocities. The process allows for the minimization of the decomposition reaction between SiCp and Ti6Al4V melt, and also leads to FGMs of SiCp/Ti6Al4V instead of a homogeneous composite layer on Ti6Al4V substrates. An injection model is designed based on the temperature/viscosity field of the laser pool for a deeper understanding the mechanism of formation of the FGMs with LMI. The model is based on finite element calculations of the temperature field in the melt pool, physical considerations of the LMI process and it is supported by experimental observations. Three types of reaction layers are observed around SiCp, namely a thin monocrystalline TiC layer, a cellular polycrystalline TiC layer and a thick mixed layer of TiC with Ti5Si3. Among them, only the monocrystalline TiC layer exhibits particular orientation relationships to the SiCp lattice, i.e. (111)TiC//(0001)SiC and <110>TiC//<1100>SiC or (111)TiC // (1012)SiC and <110>TiC//<1210>SiC. These two kinds of TiC reaction layers act as a barrier against the interfacial reaction and its swift formation during rapid cooling hinders the dissolution of SiCp in the Ti-melt.