bluuebunny/crossref_metadata_2025_split huggingface dataset:
X-Ray Techniques for Silicides
Authors: Tweet Douglas J. , Maa Jer-shen , Hsu Sheng Teng 
Published: April 2011

ABSTRACTPreviously we have found that the addition of a thin layer of Co between Ni and the Si substrate dramatically improves the thermal stability of the resulting silicide. Here we describe the use of four different x-ray techniques to obtain complementary information on film structure, providing a possible explanation for the observed thermal stability.
Stability Improvement of Nickel Silicide with Co Interlayer on Si, Polysilicon and SiGe
Authors: Maa Jer-shen , Tweet Douglas J. , Ono Yoshi , Stecker Lisa , Hsu Sheng Teng 
Published: April 2011

ABSTRACTThermal stability of nickel silicide is improved by adding a thin Co interlayer at Ni/Si interface. After high temperature anneal, the low sheet resistance of silicide and the low junction leakage of the ultra-shallow junction show the lack of film degradation. The transformation to disilicide phase occurred at a lower temperature. At 850°C, interface shows the truncated facet structure extended 100° to 200° below silicide/Si interface. With Co addition, nickel silicide formed on polysilicon and on SiGe films also show improved thermal stability and low sheet resistance. Formation temperature of disilicide phase occurred at lower temperature in all these cases.
An Experimental and Computational Study of the Elastic-Plastic Transition in Thin Films
Authors: Lilleodden Erica T. , Zimmerman Jonathan A. , Foiles Stephen M. , Nix William D. 
Published: April 2011

ABSTRACTNanoindentation studies of thin metal films have provided insight into the mechanisms of plasticity in small volumes, showing a strong dependence on the film thickness and grain size. It has been previously shown that an increased dislocation density can be manifested as an increase in the hardness or flow resistance of a material, as described by the Taylor relation [1]. However, when the indentation is confined to very small displacements, the observation can be quite the opposite; an elevated dislocation density can provide an easy mechanism for plasticity at relatively small loads, as contrasted with observations of near-theoretical shear stresses required to initiate dislocation activity in low-dislocation density materials. Experimental observations of the evolution of hardness with displacement show initially soft behavior in small-grained films and initially hard behavior in large-grained films. Furthermore, the small-grained films show immediate hardening, while the large grained films show the ‘softening’ indentation size effect (ISE) associated with strain gradient plasticity. Rationale for such behavior has been based on the availability of dislocation sources at the grain boundary for initiating plasticity. Embedded atom method (EAM) simulations of the initial stages of indentation substantiate this theory; the indentation response varies as expected when the proximity of the indenter to a Σ79 grain boundary is varied.
Deformation Microstructure of Cold Gas Sprayed Coatings
Authors: Borchers C. , Stoltenhoff T. , Gäartner F. , Kreye H. , Assadi H. 
Published: April 2011

ABSTRACTCold Gas Spraying is a new coating technique, in which the formation of dense, tightly bonded coatings occurs only due to the kinetic energy of high velocity particles of the spray powder. These particles are still in the solid state as they impinge on the substrate. Adiabatic heating after impingement can cause local shear instabilities and jet formation. The local microstructure is strongly dependant on local stress state and temperature rise. A variety of different microstructures is observed by TEM. The results are compared with modelling of the spray process.
SiC-Si Grooved Surface Bonding
Authors: Agrunova Tatiana S. , Grekhov Igor V. , Kostina Lioudmila S. , Tur'yanskii Alexander G. , Pirshin Igor V. , Prudnikov Ilya R. , Kostin Konstantin B. 
Published: April 2011

ABSTRACTSiC Lely platelets and SiC epilayers on large area SiC substrates were directly bonded to non-oxidized grooved surface silicon wafers in order to obtain structures prospective for the design of power bipolar devices with wide band-gap emitter junctions. The reported capabilities of grooved interfaces to reduce elastic strain and intrinsic sources of an interfacial potential barrier were utilized. The influence of surface morphology on the structural perfection of the bonded samples was studied in detail by X-ray and AFM techniques. As compared to traditional bonding technology, experimental data showed an easier smooth-to-grooved surface bonding accomplished in the formation of the boundary with better continuity and strength. For 2 in. diameter SiC wafers with root mean square height of roughness σ=16 Å and lateral coherence length L=1.8 μm bonding continuity not smaller than 90% was reached, while the crystals with σ=30 Å, L=5 μm failed to bond to Si even under an external force.
Monocrystalline Si Films from Transfer Processes for Thin Film Devices
Authors: Bergmann Ralf B. , Berge Christopher , Rinke Titus J. , Werner Jürgen H. 
Published: April 2011

AbstractThe transfer of thin monocrystalline silicon films to foreign substrates is of great interest for a number of applications such as silicon on insulator devices, active matrix displays and thin film solar cells. We present a transfer approach for the fabrication of monocrystalline Si films on foreign substrates based on the formation ofquasi-monocrystallineSi-films. Our transfer approach is compatible with high temperature processing such as epitaxial growth at 1100°C, thermal oxidation and phosphorous diffusion. Reuse of Si host wafers is demonstrated by the subsequent epitaxial growth of three monocrystalline Si films on a single host wafer. Monocrystalline Si films with a thickness of 15 µm and a diameter of 3” are transferred to glass and flexible plastic substrates. The typical light point defect density in films transferred from virgin wafers ranges between 10 to 100 cm−2, while stacking fault and dislocation densities are ≤ 100 cm−2. The minority carrier diffusion length in the epitaxial Si films is around 50 µm.
A New Double Laser Recrystallization Technique to Induce Ultra-Large Poly-Si Grains
Authors: Lee Minghong , Moon Seungjae , Hatano Mutsuko , Grigoropoulos Costas P. 
Published: April 2011

AbstractA new double laser recrystallization technique that can produce lateral grains of tens of micrometers is presented. A nanosecond laser (excimer or Nd:YLF laser) and a pulse modulated Ar+ laser are used in the experiment. The effect of different parameters on lateral grain growth is investigated. These parameters include the time delay between the two lasers, the excimer laser fluence, the Ar+ laser power and the pulse duration. This process has wide process window and is insensitive to both the excimer laser fluence and the Ar+ laser power fluctuations. Preheating and melting of the a-Si film with the Ar+ laser before firing the excimer laser is found to be necessary for inducting lateral grain growth. The transient excimer laser irradiation is believed to generate nucleation sites for initiating the subsequent lateral grain growth. The solidification dynamics of the process is probed by high spatial and temporal resolution laser flash photography. A lateral solidification velocity of about 10 m/s is observed.
Structure and Characteristics of Strained-Si-On-Insulator (Strained-SOI) MOSFETs
Authors: Takagi Shin-ichi , Tezuka Tsutomu , Sugiyama Naoharu , Mizuno Tomohisa , Kurobe Atsushi 
Published: April 2011

Abstrct:Strained-Si MOSFET is an attractive device structure to be able to relax several fundamental limitations of CMOS scaling, because of high electron and hole mobility and compatibility with Si CMOS standard processing. In this paper, we present a new device structure including strained-Si channel, strained-SOI MOSFET, applicable to CMOS under sub-100 nm technology nodes. The main feature of this device is that thin strained-Si channel/relaxed SiGe hetero-structures are formed on buried oxides. The principle and the advantages are described in detail. The strained-SOI MOSFETs, whose electron and hole mobility is 1.6 and 1.3 times, respectively, higher than in conventional MOSFETs, have successfully been fabricated by combining the SIMOX technology with re-growth of strained Si films. We also present novel fabrication techniques to realize ultra-thin SiGe-on-Insulator (SGOI) virtual substrates with high Ge content, including Ge condensation due to oxidation of SGOI with lower Ge content. Strained-Si/SGOI structures with total thickness of 21 nm and Ge content of 56 % have been fabricated by oxidizing SiGe films on conventional SOI substrates and re-growing strained-Si films.
Integration Challenges for Double-Gate MOSFET Technologies
Authors: Maszara W.P. 
Published: April 2011

AbstractDevice modeling data and some early experiments suggests that fully depleted MOSFET devices where channel is controlled by two opposing gates or one gate that surrounds most or the entire channel, will provide better scaling than the classic devices with one gate on one side of the channel. However, formation of such devices requires complex, non-conventional and sometimes exotic geometry and processing, ranging from wafer bonding to selective lateral ‘tunnel’ epitaxy, to selectively wet-etched channels with triangular cross-section. Classic single-gate transistors have been recently demonstrated with reasonable performance at 20-15 nm of physical gate length. Double-gate transistors with their process integration complexity will likely become a viable alternative for smaller geometries. This paper will discuss various approaches to realization of those multi-gate fully depleted devices and their process integration challenges for sub-15 nm gates.
LPCVD Deposition Techniques for Nanograin sub-10nm Polysilicon Ultra-thin Films
Authors: Ecoffey Serge , Bouvet Didier , Ionescu Adrian M. , Fazan Pierre 
Published: April 2011

AbstractThis paper investigates the limits of a low pressure chemical vapour deposition (LPCVD) technique for the deposition of a nanometre scale ultra-thin polysilicon (poly-Si) film with sub-10nm grain sizes. Three different processes using pure silane (SiH4) in a standard horizontal hot-wall reactor are presented: (i) a direct poly-Si deposition, (ii) a Hemispherical Silicon Grain (HSG) deposition and (iii) an amorphous silicon (a-Si) deposition followed by a thermal crystallization anneal. The direct poly-Si deposition gives a minimum film thickness achievable around 20 nm with grain sizes ranging from 20 to 30 nm. The HSG deposition process leads to the formation of grains with diameters varying from 5 to 50 nm and heights ranging from 5 to 20 nm. The best results are obtained with the third process (a-Si / crystallization), which allows the formation of 6 nm poly-Si thick films with grain sizes ranging from 10 to 20 nm.
Fabrication of Piezoelectric Diaphragm Using Lead Zirconate Titanate (PZT) Films
Authors: Hong E. , Krishnaswamy S.V. , Freidhoff C.B. , Trolier-McKinstry S. 
Published: April 2011

AbstractPiezoelectric diaphragms were fabricated using bulk micromachining. The diaphragms had a unimorph structure, where Pb(Zr0.52Ti0.48)O3 (PZT) and thermally grown silicon oxide (SiO2) films were used as the active and passive layers, respectively. To actuate the diaphragms, two modes were designed: d31 and d33-mode. For d31-mode diaphragms, a Si wafer with Pt/Ti/SiO2 (0.5 νm) was coated with ∼1.2 νm PZT. A Cr/Au top electrode was then evaporated. Each layer including the bottom electrode was patterned into a circular shape. To fabricate d33-mode diaphragms, a Si wafer with thermal SiO2 (0.5 νm) was coated with ∼0.3 νm ZrO2 and ∼1.6 νm of PZT. On top of these layers, a Cr/Au top electrode was deposited and patterned into a ring- shaped interdigitated transducer. Finally, both d31 and d33-mode diaphragms were released using deep reactive ion etching. Diameters of the fabricated diaphragms were in the range of 600 νm and 1000 νm. For d31-mode diaphragms, the dielectric constant and loss of the released piezoelectric layer at 1 kHz were > 800 and < 2%, respectively. The remanent polarization was ∼20 νC/cm2and the coercive field was ∼61 kV/cm. Ferroelectric measurements showed well- developed hysteresis loops for the d33-mode diaphragms. Both d31 and d33-mode diaphragms behave as membranes rather than plates. Their measured resonance frequencies were consistent with calculations from an analytic model for circular membranes and ANSYS finite element analysis.
Palladium Based Micro-Membrane Hydrogen Gas Separator-Reactor in a Miniature Fuel Processor for Micro Fuel Cells
Authors: Karnik Sooraj V. , Hatalis Miltiadis K. , Kothare Mayuresh V. 
Published: April 2011

AbstractA novel palladium-based micromembrane has been fabricated and tested which has the potential to be used for carbon monoxide shift reaction and hydrogen gas separation in a miniature fuel processor for micro fuel cells. The micromembrane structure is built in silicon substrate, using standard MEMS microfabrication processes. The four layers, viz., copper, aluminum, spin-on-glass (SOG) and palladium form the composite micromembrane. Copper, aluminum and SOG serve as a structural support for the palladium film. Copper also acts as a catalyst in the shift reaction that converts unwanted carbon monoxide gas into hydrogen, which in turn is separated by the palladium micro-membrane. For a particular combination of thicknesses for various layers, the composite micro-membrane withstands a pressure gradient up to 1 atm. The micromembrane separates hydrogen from a 20% hydrogen balance nitrogen gas mixture at room temperature.
The Materials Science of “Permeable Polysilicon” Thin Films
Authors: Dougherty George M , Sands Timothy , Pisano Albert P. 
Published: April 2011

AbstractPolycrystalline silicon thin films that are permeable to fluids, known as permeable polysilicon, have been reported by several researchers. Such films have great potential for the fabrication of difficult to make MEMS structures, but their use has been hampered by poor process repeatability and a lack of physical understanding of the origin of film permeability and how to control it. We have completed a methodical study of the relationship between process, microstructure, and properties for permeable polysilicon thin films. As a result, we have determined that the film permeability is caused by the presence of nanoscale pores, ranging from 10-50 nm in size, that form spontaneously during LPCVD deposition within a narrow process window. The unusual microstructure within this process window corresponds to the transition between a semicrystalline growth regime, exhibiting tensile residual stress, and a columnar growth regime exhibiting compressive residual stress. A simple kinetic model is proposed to explain the unusual morphology within this transition regime. It is determined that measurements of the film residual stress can be used to tune the deposition parameters to repeatably produce permeable films for applications. The result is a convenient, single-step process that enables the elegant fabrication of many previously challenging structures.
Synthesis, Characterization and Ageing of MgB2
Authors: Serquis A. , Schulze R. , Zhu Y. T. , Coulter J. Y. , Peterson D. E. , Moreno N. O. , Pagliuso P. G. , Indrakanti S. S. , Nesterenko V. F. , Mueller F. M. 
Published: April 2011

ABSTRACTWe studied the influence of sample preparation and defects in the superconducting properties samples using atomic ratios of Mg:B=1:1 and Mg:B=1:2. Samples were characterized by SEM, and XRD, and the magnetization properties were examined in a SQUID magnetometer. The presence of Mg vacancies was determined by Rietveld analysis. Most of the samples exhibited sharp superconducting transitions with Tcs between 37–39 K.We found a strong correlation between the crystal strain and the Tc. This strain was related to the presence of Mg vacancies. In addition, results showed that some samples degraded with time when exposed to ambient conditions. In these samples the Tc did not change with time, but the superconducting transition became broader and the Meissner fraction decreased. This effect was only present in samples with poor connectivity between grains and smaller grain sizes. The degradation was related to a surface decomposition as observed by X-ray Photoelectron Spectroscopy. No correlation was found between this effect and the presence of Mg vacancies.
Effect of secondary phases in the precursor powders on the transformation to the (Bi,Pb)-2223 phase
Authors: Gundakaram R. , Chang S. C. , Liu R. S. , Woodall L. , Gerards M. 
Published: April 2011

ABSTRACTThe (Bi,Pb)2Sr2Ca2Cu3O2 system [also know as (Bi,Pb)-2223] has shown promise for use in superconducting tapes and wires due to its high transition temperature and high critical current density. The tapes and wires are usually fabricated by the powder-in-tube method, after which they are subjected to thermal and mechanical treatments. Depending on the nature of the heat treatment, phase transformations occur in the powder and it is of paramount importance to understand the response of the powders to different processing conditions. In this study, we have synthesized a precursor powder of the nominal composition Bi1.8Pb0.33Sr1.87Ca2Cu3Oyby spray pyrolysis. The powder was then calcined under controlled conditions between 760 and 800°C in an atmosphere between 0 and 21% O2for 2 to 24 hours with controlled heating and cooling, such that different amounts of Pb are incorporated into the majority phase. The resultant powders were then converted to the (Bi,Pb)-2223 phase with suitable heat treatments. Using powder Xray diffraction and magnetization measurements, the volume fractions of the secondary phases in the precursors were estimated and the effect of the phases on the conversion to the (Bi,Pb)-2223 phase was studied. We show that the ratio of the intensity of the (020) and (115) reflections of the (Bi,Pb)-2212 phase can be used to tune the precursor powders for optimal conversion. While a lower fraction of the secondary phases such as CaO and CuO is desirable in the precursor powders, a higher volume fraction of Ca2PbO4 seems to help in the rapid conversion to the (Bi,Pb)-2223 phase.
High Pressure Synthesis of New Filled Skutterudites
Authors: Takizawa Hirotsugu , Okazaki Ken-ichi , Uheda Kyota , Endo Tadashi , Nolas George S. 
Published: April 2011

ABSTRACTFilled skutterudites exhibit properties that comply with the concept of a “phonon-glass electron-crystal”, as proposed by Slack. The optimal filled skutterudite would have filler atoms that exhibit large thermal vibration amplitudes in the voids of the crystal structure. It is desirable that these loosely bound atoms give rise to strong phonon scattering without greatly affecting the essential part of the band structure of the skutterudites. This criterion is difficult to meet. Most attempts have employed charge compensation for filling fractions above 50 %. In this report we present the use of a high-pressure technique for the synthesis of new filled skutterudites. By using our high-pressure synthesis technique CoSb3-based skutterudites filled with group-14 elements (Ge, Sn, and Pb) have been synthesized with up to 100 % filling without charge compensation of the host lattice. The structural analysis reveals that the Sn atoms exhibit very large thermal vibration amplitude, indicative of a large “rattling” motion. The Sn-filled specimens exhibit a low thermal conductivity, lower than that of any previously reported filled skutterudite, while the favorable semiconducting nature of the host lattice is not substantially changed by Sn filling. Tin atoms may therefore be better “rattlers” in the CoSb3 host lattice than lanthanide or actinide atoms.
Electronic Structure and Thermoelectric Properties of Ytterbium-Filled Skutterudites
Authors: Anno Hiroaki , Ashida Kazuhiro , Matsubara Kakuei , Nolas George S. , Akai Koji , Matsuura Mitsuru , Nagao Jiro 
Published: April 2011

ABSTRACTThe electronic structure and thermoelectric properties of Yb partially filled CoSb3 skutterudite compounds have been investigated by x-ray photoelectron spectroscopy and band calculation in terms of an itinerant f electron model. In these materials, the significant effect of Yb filling is the large reduction of lattice thermal conductivity, remaining relatively high electron mobility and Seebeck coefficient, resulting in high thermoelectric figure of merit. We discuss the effects of the valence fluctuation between Yb2+ and Yb3+ and the strong hybridization of Yb 4f states with the valence band states on the electronic properties and their relation to thermoelectric properties for Yb partially filled CoSb3 compounds.
Microstructural evolution of La-doped SiB6 high-temperature thermoelectric material during a Spark Plasma Sintering
Authors: Lee D.W. , Won J.H. , Kim K.H. , Matsushita J. , Shim K.B. 
Published: April 2011

ABSTRACTSiB6 has proved to a potentially useful material because of its excellent thermoelectrical properties above 700°C, low specific gravity, high degree of hardness, and moderate melting point. SiB6, which has poor sinterability with a conventional sintering technique due to the covalent characteristic, has been successfully densified fully using a spark plasma sintering(SPS) method. The SPS-processed specimens consisted of SiB6, SiB4 and SixBy phases. Pure SiB6 powder were densified fully at the sintering temperature of 1600°C. In particular, it was found that the rare earth element was very effective in evolving the microstructure of SiB6 phase, resulting in reducing the sintering temperature and controlling grain growth. These effects were discussed in details in terms of microstructure evolution during the SPS process.
Thermoelectric Properties of PbSe Epitaxial Thin Films and PbSe/EuS Heterostructures
Authors: Dresselhaus Mildred S. , Dresselhaus Gene , Rogacheva Elena I. , Tavrina Tatyana V. , Grigorov Sergey N. , Nasedkin Konstantin A. , Volobuev Valentine V. , Sipatov Alexander Yu. 
Published: April 2011

ABSTRACTSystematic investigations were performed of the thickness dependences of the thermoelectric properties of PbSe thin films, freshly prepared and exposed to air at room temperature. It is shown that oxidation leads to a sharp change in the thermoelectric properties of the PbSe films including a change in the sign of the dominant carrier type from n-type to p- type at d ≤ 80 nm. Using a two carrier model for thin films (d < 50 nm) and a two-layer model for thick films (d > 50 nm) allows us to give a satisfactory qualitative interpretation of the observed experimental dependences of the thermoelectric properties on the film thickness.
Geometric Effects on the Transient Cooling of Thermoelectric Coolers
Authors: Yang Ronggui , Chen Gang , Snyder G. Jeffrey , Fleuriel Jean-Pierre 
Published: April 2011

ABSTRACTTransient thermoelectric cooling effect has been known since 1960s. Most of the previous studies focus on the minimum temperature achievable for free standing thermoelectric elements. Practical thermoelectric coolers have a passive mass load, which affect the minimum temperature achievable. This is particularly true for thermoelectric micro coolers because the object to be cooled is comparable to the micro coolers in size. In this paper, we present the performance analysis of the integrated system made of the cooling object and thermoelectric element, and establish the criterion for the utilization of transient cooling effect based on the analysis of the time constants. Effects of thermoelectric element shape on the transient thermoelectric cooling effect are also studied.