bluuebunny/crossref_metadata_2025_split huggingface dataset:
Channel Engineering of SiGe-Based Heterostructures for High Mobility MOSFETs
Authors: Leitz Christopher W. , Currie Matthew T. , Lee Minjoo L. , Cheng Zhi-Yuan , Antoniadis Dimitri. A. , Fitzgerald Eugene A. 
Published: April 2011

AbstractStrained Si- and SiGe-based heterostructure metal-oxide-semiconductor field-effect transistors (MOSFETs) grown on relaxed SiGe virtual substrates exhibit dramatic electron and hole mobility enhancements over bulk Si, making them promising candidates for next generation complementary MOSFET (CMOS) devices. The most heavily investigated heterostructures consist of single strained Si layers grown upon relaxed SiGe substrates. While this configuration offers significant performance gains for both n- and p-MOSFETs, the enhanced hole mobility remains much lower than the enhanced electron mobility. By contrast, a combination of buried compressively strained Si1−yGey layers and tensile strained Si surface layers grown on relaxed Si1−xGex (x < y), hereafter referred to as dual channel heterostructures, offers nearly symmetric electron and hole mobilities without compromising n-MOSFET device performance. To investigate these heterostructures, we study the effects of alloy scattering on channel mobility in long channel MOSFETs. By using the combination of a buried Si0.2Ge0.8 channel and a strained Si surface channel grown on a relaxed Si0.5Ge0.5 virtual substrate, we have achieved nearly symmetric electron and hole mobility in the same heterostructure. By employing different virtual substrate compositions, we can decouple the effects of strain and alloy scattering in both tensile strained surface channels and compressively strained buried channels. We show that significant hole mobility enhancements can be achieved in dual channel heterostructures, even for buried channel compositions where alloy scattering is expected to be most severe. Furthermore, we show that alloy scattering in tensile strained SiGe surface channels impacts electrons much more severely than holes. Taken together, these results demonstrate that dual channel heterostructures can offer symmetric carrier mobilities and provide excellent performance gains for CMOS applications.
Design and Modelling of a Fourier Spectrometer Based on Sampling a Standing Wave
Authors: Knipp D. , Stiebig H. , Büchner H.-J. , Jäger G. , Rosa M. , Street R.A. 
Published: April 2011

AbstractThe design of a novel spectrometer based on a thin film diode in combination with an electro statically tunable micro machined mirror will be presented. The semi transparent diode is introduced into a standing wave created in front of a reflector to sample the profile of the standing wave. Varying the position of the reflector results in a shift of the phase of the standing waves and thus in a change of the optical generation profile within the detector. The spectral information of the incoming light can be determined by the Fourier transformation of the transient response of the sensor. An analytical optical model will be presented which facilitates the evaluation of different detector concepts. The model will be applied to discuss different device designs regarding the resolution of the spectrometer, the spectral range and the linearity.
Silicon Microfabrication: Laser Ablation vs. Inductively Coupled Plasma (ICP) Etch
Authors: Owens Megan M. , Soucy Joseph W. , Marinis Thomas F. 
Published: April 2011

AbstractMechanical prototypes of a silicon interposer device, having high-aspect ratio straight walls, were required for experiments to qualify various packaging assembly options. The ideal solution would yield expendable, quickly made, and relatively inexpensive replica parts.This need led to the investigation of micromachining of silicon via laser ablation. We sought to optimize the results by varying several parameters, the most influential of which was shown to be laser wavelength. Silicon wafers of thickness 500 νm were machined using laser wavelengths of 10,600 nm, 1064 nm, and 355 nm. As was predicted according to the theoretical silicon absorption profile, the best results were obtained using 355 nm wavelength light from an ultraviolet laser source. Several post-machining cleaning routines, to remove melted silicon debris, were evaluated as well. Pictorial results of both laser processing and cleaning are shown and discussed.ICP was concurrently investigated as a viable alternative to laser machining. These cuts were markedly cleaner and straighter than those induced by laser; additionally, cut features were more well defined. Pictorial results are compared and contrasted with those of laser ablation.Cost and time are traded for quality when choosing between laser ablation and ICP etch. Therefore, process choice should be application-dependent. For wafers with moderately complex cutout features, laser micromachining is significantly lower in cost and manufacturing time. However, the laser process does produce residual thermal stress surrounding the cut region, machined edges are relatively rough, and fine features are more difficult to produce. Laser ablation is an attractive manufacturing option for quick-turnaround prototyping as well as high-volume production; ICP is better suited to producing high-definition parts without potential for thermal stress damage.
Metastable Superstructures in RuSr2Gd1.4Ce0.6Cu2O10-δ?Superconductor Based on TEM Observation at Room Temperature
Authors: Yang Li , Vieira J. M. , Tang Kaibin , Zhou Guien 
Published: April 2011

ABSTRACTThree types of metastable modulations in Ru-based superconductor RuSr2Gd1.4Ce0.6Cu2O10-δ are observed by electron diffraction at room temperature and reported in this paper. The modulations are sensitive to the irradiation of the electron beam and the sample storage time. Having the tetragonal symmetry (I4/mmm) with a=0.384nm, c=2.864nm, the structure of RuSr2Gd1.4Ce0.6Cu2O10-δ?resembles that of YBa2Cu3O7-δ by inserting a fluorite type Gd1.4Ce0.6O2 layer instead of the Y layer and Ru ions residing in the Cu(1) site. In this compound, superconductivity is confined to the CuO2 layer while magnetism stems from the RuO2 layer. The metastable modulations display the interaction between the two layers from the structural point of view. The results suggest that although, superconductivity and magnetism are decoupled from each other in the unconventional superconductor, the effect may be limited by metastable lattice modulation.
Orientation Control of HTS Thin Films
Authors: Endo K. , Ishikawa H. , Yoshizawa T. , Abe K. , Itoh J. , Kajimura K. 
Published: April 2011

ABSTRACTThe preparation of non c-axis oriented HTS films with longer coherence length is one of key technologies toward realisation of viable Josephson devices. We reports on the successful growth of (119)Bi-2223 films by MOCVD using a two-step growth temperature procedure and on AFM observation of the film surface. This temperature procedure was found to be effective for orientation control and phase control in comparison with a fixed growth temperature procedure. As a result, superconducting properties were much improved. The surface morphology observed by AFM showed a mountain-range-shaped one, which strongly reflects the epitaxial relationship between the (119)Bi-2223 film and (110) SrTiO3 substrate.
Preparation of [Ba2CuO2(CO3) ]m[ACuO2]n(A=Sr,Ca) Films by MBE Technique
Authors: Adachi Yutaka , Matsui Yoshio , Sakaguchi Isao , Haneda Hajime , Takahashi Koichiro 
Published: April 2011

ABSTRACT[Ba2CuO2(CO3)]m[ACuO2]n(A=Sr) superlattices containing oxycarbonate blocks as charge reservoir have been prepared on SrTiO3 using the molecular beam epitaxy technique. First, thin films of the oxycarbonate cuprate Ba2CuO2(CO3) have been prepared on SrTiO3(001) using NO2 gas as an oxidant and CO2 gas. The films have been grown at 500°C. At higher substrate temperature or at lower CO2 pressure Ba2CuO3 was formed instead of Ba2CuO2(CO3), and the films becomes amorphous at lower temperature. X-ray diffraction and reflection high-energy electron diffraction observations indicated that (BaxSr1−x)2CuO2(CO3) grew along the [001] crystal orientation on SrTiO3(001) with the following epitaxial relationship: Ba2CuO2(CO3)[100]//SrTiO3[110] and Ba2CuO2(CO3)[110]//SrTiO3 [100]. Depth profile of secondary ion mass spectrometry signals indicated the incorporation of carbon into the films. Secondly, the oxycarbonate cuprates and infinite layers have been alternately stacked. It was confirmed that Ba2CuO2(CO3)was inserted between several unit cells of SrCuO2. Electrical measurements show the as grown films to have a semiconducting behavior.
The Progress on Low-Cost, High-Quality, High-Temperature Superconducting Tapes Deposited by the Combustion Chemical Vapor Deposition Process
Authors: Shoup Shara S. , White Marvis K. , Krebs Steve L. , Darnell Natalie , King Adam C. , Mattox Dave S. , Campbell Ian H. , Marken Ken R. , Hong Seung , Czabaj Bolek , Paranthaman M. , Christen Hans M. , Zhai Hong-Ying , Specht Eliot 
Published: April 2011

ABSTRACTThe innovative Combustion Chemical Vapor Deposition (CCVD) process is a non-vacuum technique that is being investigated to enable next generation products in several application areas including high-temperature superconductors (HTS). In combination with the Rolling Assisted Biaxially Textured Substrate (RABiTS) technology, the CCVD process has significant promise to provide low-cost, high-quality lengths of YBCO coated conductor. The CCVD technology has been used to deposit both buffer layer coatings as well as YBCO superconducting layers. A buffer layer architecture of strontium titanate and ceria have been deposited by CCVD on textured nickel substrates and optimized to appropriate thicknesses and microstructures to provide templates for growing PLD YBCO with high critical current density values. The CCVD buffer layers have been scaled to meter plus lengths with good epitaxial uniformity along the length. A short sample cut from one of the lengths enabled high critical current density PLD YBCO. Films of CCVD YBCO superconductors have been grown on single crystal substrates with critical current densities over 1 MA/cm2. Work is currently in progress to combine both the buffer layer and superconductor technologies to produce high-quality coupons of HTS tape made entirely by the non-vacuum CCVD process.
Critical Currents at Grain Boundaries in High Temperature Superconductors
Authors: Agassi D. , Pennycook S. J. , Christenb D. K. , Duscher G. , Franceschetti A. , Pantelides S. T. 
Published: April 2011

ABSTRACTWe present atomic resolution Z-contrast images, electron energy loss spectroscopy (EELS) and theoretical calculations in support of a band-bending model for the effect of grain boundaries on critical currents. In the high angle regime, dislocation cores are closely spaced and the boundary is modeled as a continuous junction, with a width determined by the dislocation density per unit boundary length. This quantitatively explains the approximately exponential reduction in critical current. In the low angle regime, where dislocations are separated by substantial good passages, explicit calculations of flux pinning are presented. Significant differences are found between a strain and band-bending mechanism. Recent data fit the band-bending model and suggest substantial improvement is possible through doping to a flat band condition.
Continuous YBCO – Tape Coating by Thermal Evaporation
Authors: Nemetschek Ralf , Prusseit Werner , Holzapfel B. , Eickemeyer J. , deBoer B. , Miller U. , Maher E. 
Published: April 2011

ABSTRACTCurrently, due to simultaneous large area coating thermal evaporation (TE) allows the highest YBa2Cu3O7 (YBCO) volume deposition rates among various coating techniques. The simultaneous large area deposition translates into long length when the deposition area is closely filled up with metal tape. On short RABiTS samples thermal evaporation has already established critical current densities in excess of 1 MA/cm2 at 77K. Recently, the deposition technique has been scaled up using a multi-turn tape winder for a simultaneously coatable length of 4 meters of 1 cm wide tape. The reel to reel tape deposition system is designed for long term operation based on a vapor composition control by atomic absorption spectroscopy and in situ refillable evaporation sources. In the initial setup phase the system has been able to reproduce the above results on small samples. The first results on continuously moving tape substrate coating up to a length of several meters will be reported.
Effect of Sulfur Surface Structure on Nucleation of Oxide Seed Layers on Textured Metals for Coated Conductor Applications
Authors: Cantoni C. , Christen D. K. , Goyal A. , Heatherly L. , Ownby G. W. , Zehner D. M. , Norton D. P. , Rouleau C. M. , Christen H. M. 
Published: April 2011

ABSTRACTWe present a study of the {100}<100> biaxially textured Ni (001) surface and oxide seed layer nucleation by in situ reflection high-energy electron diffraction and Auger electron spectroscopy. Our observations revealed the existence of a c(2×2) superstructure on the textured Ni surface due to segregation of sulfur contained in the bulk metal. The sulfur superstructure promotes the epitaxial (002) nucleation of seed layers such as Y2O3-stabilized ZrO2 (YSZ) and CeO2 on the metal and optimizes the biaxial texture necessary for high Jc superconductors on RABiTS.
Pattern Shape-Controlled Self-Assembly of Bi0.90Si0.10 Nanocrystallites
Authors: Fang Jiye , Stokes Kevin L. , He Jibao , Zhou Weilie L. , O'Connor Charles J. 
Published: April 2011

ABSTRACTNanometer-sized Bi0.90Sb0.10 has been, for the first time, prepared using a hightemperature organic solution reducing method. With the presence of proper capping and stabilizing agents, we were able to produce Bi0.90Sb0.10 nanoparticles as small as ∼12 nm. Nearly monodisperse distributions were obtained through a size-selective post treatment. Transmission electron microscope characterization reveals that the as-prepared particles have a highly crystalline single rhombohedral phase. Self-assembled patterns of Bi0.90Sb0.10 were successfully achieved upon evaporation of the solvent from the nanoparticle colloids. As a step toward possible applications of these particles in thermoelectric device structures, we have also demonstrated that we are able to control the pattern of Bi0.90Sb0.10 self-assembly from 2D to 1D by employing different solvent systems with varying ratios of polar and non-polar components.
Annealing Studies of Re Doped AlPdMn Quasicrystals
Authors: Winkler Donny W. , Tritt Terry M. , Gagnon Robert , Strom-Olsen J. 
Published: April 2011

ABSTRACTQuasicrystals have properties associated with both crystalline and amorphous materials. These properties appear to be sensitive to both composition and annealing conditions. Therefore, it is important to investigate the influence of the microstructure on the electrical and thermal transport properties of quasicrystals. AlPdMn quasicrystal samples were prepared with various levels of Re substituted for the Mn (Al70Pd20Mn10−XReX) and then subjected to different annealing conditions. Electrical resistivity, thermopower and thermal conductivity were measured on each as grown and annealed sample over a broad range of temperature, 10 K < T < 300 K. The relationship between the electrical and thermal transport properties and microstructure will be presented and discussed.
Enhancement of Thermal to Electrical Energy Conversion with Thermal Diodes
Authors: Hagelstein P. L. , Kucherov Y. 
Published: April 2011

ABSTRACTExperiments demonstrating thermal to electrical energy conversion using thermal diodes have shown an enhancement of the open circuit voltage over the thermoelectric open circuit voltage. Two different physical mechanisms are proposed to be responsible for the effects seen: (1) Thermionic injection from the emitter can occur when a temperature gradient is present, which induces an increased ohmic return current under zero-current conditions. (2) Blockage of the ohmic return current leads to a voltage increase for both thermoelectric and thermionic forward currents. Both effects increase the efficiency of energy conversion. Experiments show enhancements of the figure of merit in the range of 5-8 over the thermoelectric values. The best results are consistent with a single-side conversion efficiency in excess of 30% of the Carnot limit.
Electronic Structure and Thermoelectric Property of Skutterudite CoSb3
Authors: Koga Kenji , Akai Koji , Oshiro Kazunori , Matsuura Mitsuru 
Published: April 2011

ABSTRACTElectronic structure of CoSb3 is calculated by means of full-potential linearlized augmented plane wave (FLAPW) method with the generalized gradient approximation (GGA). The calculated band gap of CoSb3 with the consideration of spin-orbit (SO) interaction is 110meV, which is about a half of that without SO interaction. It is found that simple four bands model with the Kane's nonparabolic valence and conduction bands, two parabolic conduction bands describe calculated electronic structure near band edge very well. Using the simple four bands model, thermoelectric properties are calculated and are discussed. Larger band gap, e.g., Eg=200meV with the microscopic mechanism such as phonon scattering yields a fair agreement with the experiment in a wide range of temperature.
Kinetic Monte Carlo Simulations of Dislocation Etch-Pits
Authors: Bentz Daniel N. , Jackson Kenneth A. 
Published: April 2011

AbstractChemical mechanical polishing and stress corrosion cracking result from chemical attack at stressed regions. To better understand the combined effects of chemical attack and stress, a kinetic Monte Carlo (kMC) study of the formation of dislocation etch pits is being pursued. In the simulations, atoms from a diamond cubic lattice are irreversibly removed with a probability which depends on an atom's number of nearrest neighbors as well the local stress developed from its physical location with respect to a dislocation in the lattice. In accordance with experimental observations, both faceted and non-faceted dislocation etch-pits have been observed. Simulations have been performed for various values of the strength to the etchant attack and the magnitude of the stress produced by the dislocation.
Novel Preparation Method of Thin Films by Ablation Plasma produced by Intense Pulsed Ion Beam Evaporation
Authors: Yatsui Kiyoshi , Suematsu Hisayuki , Jiang Weihua , Suzuki Tsuneo , Yang Sung-Chae , Kinemuchi Yoshiaki , Hirai Makoto , Kato Keizo 
Published: April 2011

AbstractA novel preparation method of thin films has been successfully developed by high-density ablation plasma produced by pulsed ion-beam evaporation method. The preparation is available with extremely high deposition rate (with cm/s), without heating the substrate, in a vacuum, with good stoichiometry. As an example, the preparation of phosphoresecent SrAl2O4:Eu, Dy thin films will be shown. Furthermore, a new method has been developed of the synthesis of ultrafine nanosize powders by use of microexplosion of pulsed wire discharge. As an example, the synthesis of NiFe2O4 powders will be shown, where two wires of nickel and iron were exploded by pulsed current. In addition, we have succeeded in the preparation of tungsten thin films within via holes in LSI by use of pulsed ion beam-evaporation method. In addition to the huge power per shot, a new machine has been developed of highly repetitive, pulsed power machine for the industrial applications.
Fabrication of CaO Insulator Coatings by MOCVD for Application in Fusion Reactor Blankets
Authors: Zeng Z. , Natesan K. 
Published: April 2011

AbstractThe liquid lithium blanket for fusion reactors requires an electrically insulating coating on the duct to minimize the magnetohydrodynamic pressure drop that occurs during the flow of liquid metal in a magnetic field. Calcium oxide (CaO) is a good candidate for the coating material because it is an excellent electrical insulator and it is stable in a liquid lithium environment. In this paper, details are presented on metalorganic chemical-vapor deposition method that was used to fabricate the CaO coating. Composition and phase analyses of the coating were performed by energy dispersive X-ray analysis and X-ray diffraction. Scanning electron microscopy images show that the coating did not crack after several thermal cycles from room temperature to 715°C. The resistance of the coating is high enough for an insulating coating on the liquid lithium blanket of fusion reactors.
Formation and Conductive Properties of Miniaturized Fullerite Sensors
Authors: Berdinsky Alexander S. , Fink Dietmar , Petrov Alexander V. , Müller Manfred , Chadderton Lewis T. , Chubaci Jose F. , Tabacniks Manfredo H. 
Published: April 2011

AbstractFullerite nanotubules of 100 nm to 2 μm radius, up to 200 nm wal thickness and 10 μm length were produced inside etched swift heavy ion tracks in a polymer, by letting fullerence precipitate from a concentrated C60 solution within the tracks. After contacting the tubules on both sides with silver paste, their resistivity was measured as a function of temperature. All of the 13 prepared samples show a complex behaviour that can be described by tw Arrhenius curves, the low temperature branch with activation energy Eact = (1.77 ± 0.2) eV stemming from pure C60, and the high temperature branch being tentatively ascribed to C60Agx with x ≍ 12.4 and Eact = (0.68 ± 0.2) eV, as the letter compound has found to be produced at ambient temperature by C60 / Ag thermal intermixture. Such samples with tw branches of negative temperature coefficients of resistance might be useful to construct advanced thermoresistors.
Building Two and Three-dimensional Structures of Colloidal Particles on Surfaces using Optical Tweezers and Critical Point Drying
Authors: Vossen Dirk L. J. , Hoogenboom Jacob P. , Overgaag Karin , Blaaderen Alfons van 
Published: April 2011

AbstractWe describe a method for patterning substrates with colloidal particles in any designed two-dimensional structure. By using optical tweezers particles are brought from a reservoir to a surface that carries a surface charge opposite to that of the particles. Using this technique large, two-dimensional patterns can be created, where the pattern can be manipulated on a single particle level. We show that these structures can be dried using critical point drying thus preventing distortions due to surface tension forces. After drying patterned surfaces can be used for further processing, which includes repeating the procedure of patterning. We show some first results of three-dimensional structures created using this layer-by-layer method. The method is generally applicable and has been demonstrated for a variety of (core-shell) colloidal particles including particles that are interesting for photonic applications like high-refractive index (ZnS)-core – silica shell particles, metallodielectric (gold)-core – silica-shell particles, fluorescently labeled particles and small (several nanometers large) gold particles. Particle sizes used range from a few nanometers to several micrometers.
Patterned Nanoparticle Assembly as Novel Chemical and Biological Platforms
Authors: Maye M.M. , Luo J. , Han L. , Kariuki N. , Zhang F.X. , Zhong C.J. 
Published: April 2011

AbstractThe ability to self-assemble nanoparticles into thin films and subsequently characterize the structural or morphological responses to interfacial chemical/biological reactivity is increasingly important. Surface patterning and tailoring us ing nanoparticle assemblies are expected to provide such abilities for selective immobilization and chemical and biological recognition. We describe herein recent results of an investigation of hydrogen-bonding based self-assembly of core-shell nanoparticles onto monolayer-patterned surfaces, and its potential utility for in-situ atomic force microscopic characterizations of interfacial chemical and biological reactivities. This system is potentially useful for immunoassays based on topographical height changes with well-defined internal morphological standard.