bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth Rate Enhancement in Selective Area Movpe
Authors: Fujii Takuya , Ekawa Mitsuru , Tanahashi Toshiyuki 
Published: April 2011

AbstractWe investigated the growth rate enhancement in selective area metalorganic vapor phase epitaxy with a new surface boundary condition for the vapor phase concentration of source materials. In our model, the growth rate is proportional to the vapor phase concentration at a distance of the vapor phase mean-free path of source materials from the substrates, and the vapor phase concentration is laterally uniform at the top of the stagnant layer. This model predicts that the growth rate modulation produced by mask-patterning disappears at a specific pressure at which the vapor phase mean-free path reaches the stagnant layer thickness. We controlled the vapor phase mean-free path of trimethylindium in InP growth by varying the growth pressure from 6 to 180 Torr with a fixed total inlet gas flow rate to the reactor. Experiments showed a great reduction of the growth rate enhancement with the decrease in the growth pressure and the growth rate enhancement virtually disappeared at the lowest pressure. We also investigated the dependence of the stagnant layer thickness on the mask design. The experimental stagnant layer thickness related to the typical surface length, such as the period of mask-patterning.
Formation of Quantum Wires by Strain-Induced Lateral-Layer Ordering Process: Growth Mechanism and Device Applications
Authors: Cheng K. Y. , Hsieh K. C. 
Published: April 2011

AbstractGaxIn1−xAs and GaxIn1−xP quantum wire (QWR) arrays were grown by a single-step molecular beam epitaxy. Lateral Ga(In composition modulation perpendicular to the growth direction occurs spontaneously during the growth of (GaAs)m/(InAs)n or (GaP)m/(InP)n shortperiod superlattices on InP or GaAs substrates, respectively, by the strain-induced lateral-layer ordering (SILO) process, producing lateral quantum wells. This straightforward method employs standard on-axis (001)-oriented substrates, and requires no pre-growth substrate patterning, nor does it involve post-growth processing for the formation of QWRs. Both GaxIn1−xAs infrared (1.7 μm) lasers and GaxIn1−xP visible (0.7 μm) lasers with QWR active regions have been successfully fabricated. These lasers showed many unique features that have never been observed in quantum well lasers.
Compositional Modulation and its Optoelectric Properties of Zn(S,Se,Te) Crystals Grown by Hydrogen Radical-Enhanced CVD
Authors: Fujiwara Hiroyuki , Ii Toshihiro , Shimizu Isamu 
Published: April 2011

AbstractHigh-quality (ZnS)n(ZnSe)12n and (ZnSe)n(ZnTe)11n (n=1∼4) crystals were grown at a low temperature of 200°C by hydrogen radical-enhanced chemical vapor deposition. From satellite peaks in x-ray diffraction spectra, these periodic structure crystals were confirmed to be grown coherently on substrates, in spite of large lattice mismatches between the grown layers and the substrates (͛=4∼7%). In photoluminescence (PL) spectra of these films, strong band-edge emissions were predominantly observed, resulting from a suppression of deep-level emissions. We found that the PL peak energy of (ZnSe)n(ZnTe)11n shifts systematically to lower energy by 200 meV with changes in the number of ZnSe layers (n), while relatively small shift of 13 meV was observed in (ZnS)n(ZnSe)12n. These discrepancy can be attributed to the difference of band-lineups or chemical natures of constituent atoms in these crystals.
AlInAs Band Gap Modulations Observed by Tem and Optical Measurements
Authors: Bearzi E. , Benyattou T. , Bru-Chevallier C. , Guillot G. , Harmand J. C. , Marty O. , Pitaval M. 
Published: April 2011

AbstractAt a low MBE growth temperature (400°C), an anisotropic composition modulation has been observed by Transmission Electron Microscopy (TEM) on AIlnAs layers. Optical measurements have been performed on these samples and compared with classical AllnAs grown at 530°C. We show the clustering “organization” on the low temperature layers and we propose some hypothesis to explain the composition modulation effects on the AlInAs optical properties.
Ordering in GaxIn1−xAsyP1−y Detected by Diffraction Methods
Authors: Rechenberg I. , Oster A. , Knauer A. , Richter U. , Menniger J. , Weyers M. 
Published: April 2011

AbstractGa0.54In0.46As0.12P0.88 lattice matched to GaAs and grown by metal organic vapor phase epitaxy (MOVPE) shows an anomalous temperature behaviour of its cathodoluminescence (CL) emission. Using high resolution x-ray diffraction (HRXRD) and transmission electron diffraction (TED), ordering in this quarternary alloy can be identified as the reason for this behaviour. The ordering follows the same trends with respect to misorientation that are known for InGaP. In addition to ordering, compositional fluctuations related to a miscibility gap are found in this material. In contrast, layers with a higher As-content (y=0.5; y=0.76) do not show properties related to ordering.
Texture and Related Phenomena of Copper Electrodeposits
Authors: Lee D. N. 
Published: April 2011

AbstractThe texture of copper electrodeposits changes from the orientation that places the lowest energy crystal facets parallel to the substrate under a condition of low ion concentration adjacent to the deposit, to the orientation that places the higher energy crystal facets parallel to the substrate as the ion concentration adjacent to the deposit increases. The copper electrodeposits have peculiar surface morphologies and microstructures depending on their textures, which in turn may affect their mechanical properties even when they are obtained in similar electrolysis conditions. The electrodeposits undergo recrystallization, when annealed. The recrystallization texture may be different from the original deposit texture. These phenomena have been discussed.
Sub-Half Micron Electroless Cu Metallization
Authors: Dubin V. M. , Shacham-Diamand Y. , Zhao B. , Vasudev P. K. , Ting C. H. 
Published: April 2011

AbstractElectroless Cu metallization has been fabricated by blanket electroless Cu deposition into the trenches in SiO2 dilectric layer on sputtered Cu seed layer with Ta diffusion layer and Al protection layer. Chemical-mechanical polishing of copper has been used to planarize the structure. Selective electroless CoWP layer has been deposited to protect inlaid Cu metallization.
Mocvd of Copper from New and Liquid Precursors (hfac)CuL, Where L = 1-Pentene, Atms, and Vtmos
Authors: Shin H. K. , Shin H. J. , Lim S. J. , Yoo D. J. , Oh N. Y. , Yoo H. J. , Baek J. T. , Jun C. H. , Kim Y. T. 
Published: April 2011

AbstractLiquid and volatile (hfac)CuL compounds where hfac = 1,1,1,5,5,5-hexafluoro- 2,4-pentanedionate and L = 1-pentene (1), acetyltrimethylsilane (2), and vinyltri- methoxysilane (3) were newly developed for reproducible copper deposition. During CVD processes, no premature decomposition of the precursor was observed in the source reservoir that contained the mixture of (hfac)CuL and excess free ligand L. Pure Cu films were deposited in the deposition temperature range 180°C ˜ 220°C
Impact of Rapid Thermal Annealing of Ti/Tin Bilayers On Subsequent Chemical Vapor Deposition Of Tungsten
Authors: Mourouxt A. , Palmans R. , Keinonen J. , Zhang S. -L. , Maex K. , Petersson S. 
Published: April 2011

AbstractThe influence of rapid thermal annealing (RTA) of Ti/TiN on the stress in the subsequently deposited tungsten (W) films and on the impurity contents at the TiN-W interface was investigated for two types of Ti/TiN bilayers sputter-deposited at 300 °C and 550 °C. A post treatment of the Ti/TiN bilayers resulted in a substantially decreased stress in the W films. It also led to a considerable reduction of the fluorine contents at the TiN-W interface. Both effects were more pronounced for the W deposited on the low-temperature Ti/TiN bilayers and/or annealed in the NH3 atmosphere, than on the high-temperature Ti/TiN bilayers and/or annealed in the N2 atmosphere. Annealed in N2, the interfacial oxygen at the TiN-W interface increased slightly, which can be attributed to the presence of trace amounts of O2 in the N2 atmosphere. A slight increase in the W film resistivity was thus found for the W films deposited on the N2 annealed Ti/TiN bilayers, while the resistivity decreased somewhat for the W films deposited on the NH3 annealed Ti/TiN bilayers. After the post treatment, a large amount of nitrogen was found incorporated in the Ti layer forming TiNx (× < 0.3). However, the post treatment led to a considerable increase in the tensile stress in the Ti/TiN bilayers, and then an increase in the total stress of the whole Ti/TiN/W system. This stress increase could be controlled by using moderate anneal temperatures (e.g. < 550 °C) for the post treatment.
Interdiffusion and Phase Formation During Thermal Annealing of Ti/Mo Bilayers on Si Substrates
Authors: Mouroux A. , Zhang S.-L. , Kaplan W. , Nygren S. , Östling M. , Petersson C. S. 
Published: April 2011

AbstractThe formation of TiSi2 from deposited Ti layers on Si and the subsequent transformation of TiSi 2 from the C49 to the C54 phase have long been of concern, particular for the silicide formation on heavily doped, narrow polycrystalline Si lines. In this work, phase formation during rapid thermal annealing of Ti/Mo bilayers sequentially deposited on blanket Si wafers and on narrow polycrystalline Si lines (0.6 μm width) is studied. The Mo layer is always 0.5 nm thick, and the Ti either 45 nm or 60 nm. It is shown that the initial physical separation of Ti from Si by the interposed Mo layer leads to complete prevention of the formation of the C49 phase. Instead, a Mo-bearing silicide phase of hexagonal structure forms first, and the C54 phase nucleates and then grows on top of it via Si diffusion through the growing silicide layers. The significance of this finding is that the usual sequence for the formation of TiSi2,. e. the C49 phase forms as a result of the Ti-Si interaction and the C54 phase forms as the product of phase transformation, is altered by the interposition of a thin refractory metal layer, here Mo. The difficulties involved in nucleation and growth of the C54 phase are then overcome, yet by a different approach than the usually employed ones which rely on ion implantation to enhance the formation of the C49 phase and the subsequent transformation to the C54 phase.
Dependence of Crystallographic Texture of C54 Tisi2 on Thickness and Linewidth In Submicron Cmos Structures
Authors: Svilan V. , Rodbell K. P. , Clevenger L. A. , Cabral C. , Roy R. A. , Lavoie C. , Jordan-Sweet J. , Harper J. M. E. 
Published: April 2011

AbstractPreferential crystal orientation of low-resistance C54 TiSi2 formed in the reaction of polycrystalline and single crystal silicon with titanium was investigated for Ti thicknesses ranging from 15 to 44 nm. Using in situ synchrotron x-ray diffraction during heating of 15 nm of Ti on single crystal Si, we observed that the C54 TiSi2 silicide film showed predominantly <040> grains oriented normal to the sample. In thicker silicide films the <311> orientation dominated or film was randomly oriented. An ex situ four circle diffractometer was used to investigate the strong <040> texture in narrow line arrays of C54-TiSi2 formed on polycrystalline silicon with linewidths from 0.2 to 1.1 μm. We observed that the angular distribution of <040> Ti Si2 grains is dependent on the line direction, where the majority of grains had their (100) planes oriented parallel with the line direction. These findings support a model of the C49 to C54 TiSi2 transformation involving rapid growth of certain orientations favored by the one-dimensional geometry imposed by narrow lines.
Structural Evolution in Carbon Aerogels as a function of Precursor Material and Pyrolysis Temperature
Authors: Gross J. , Alviso C. T. , Pekala R. W. 
Published: April 2011

AbstractSeveral organic reactions that proceed through a sol-gel transition have been identified at LLNL. The most-studied reaction involves the aqueous polycondensation of resorcinol (1,3- dihydroxybenzene) with formaldehyde. Recently, we have shown that phenol can be added to this polymerization as a comonomer. The resultant crosslinked gels are supercritically dried from carbon dioxide (Tc=31°C, Pc = 7.4 MPa) to give resorcinol-phenol-formaldehyde (RPF) aerogels. Because RPF aerogels are composed of a highly crosslinked aromatic polymer, they can be pyrolyzed in an inert atmosphere to form vitreous carbon monoliths (CRPF). The resultant aerogels are black in color and no longer transparent, yet they retain the high porosity (40–98 %), ultrafine cell/pore size (< 50 nm), high surface area (600–800 m2/g), and interconnected particle (˜10 nm) morphology of their organic precursors. In this study, we examine the acoustic and mechanical properties of these materials as a function of precursor material and pyrolysis temperature. It is shown that the elastic moduli of RPF and CRPF is higher than that of pure RF / CRF aerogels at a given density. Upon pyrolysis RPF aerogels tend to shrink to a larger extent.
Preparation of Supported Zeolite Films and Layers: Processing of Zeolite Suspensions and In Situ Growth from Homogeneous Solutions
Authors: Lovallo Mark C. , Boudreau Laura , Tsapatsis Michael 
Published: April 2011

AbstractThe influence of microstructure on the properties of zeolite films and means of controlling the former (film thickness, crystal orientation) are the theme of this report. Firstly, the formation of thin silicalite films from regrowth of nanocrystalline silicalite/alumina composite films is presented. The crystallites at the intergrown top layer are oriented with their straight channels parallel to the substrate film. The membranes show H2/N2 selectivities of about 60 at 150 °C.This high selectivity is attributed to the orientation of the separating layer. Secondly, the formation of oriented multilayers of zeolite L crystallites by alternating dippjpg of a glass substrate in a bohemite and a “plate-like” zeolite L suspensions is illustrated. Finally, continuous films of zeolite NaA are prepared on various substrates (glass, porous and nonporous alumina) using in situ growth from homogeneous solutions. The films exhibit good adhesion to the substrates. The films prepared on porous alumina disks show He/N2 and O2/N2 selectivities of 10 and 0.4 respectively at 120 °C.
Characterization of Porous AlN Separators for Batteries
Authors: Thorsland Brett N. , Giesche Herbert , Mroz Thomas J. , Martin Michael 
Published: April 2011

AbstractA ceramic membrane of porous, sintered aluminum nitride (AIN) is under consideration for use as a separator in a Lithium-Metal Sulfide battery due to the corrosion resistance and thermal stability of AlN. The pore structure and electrolytic permeability of the membrane must be appropriate if AlN is to be used. Commercialization of these membranes can occur only after repeatability in the processing conditions can be assured. In this study, extensive permeability and porosity testing was performed on membranes prepared under various processing conditions. Attempts to correlate processing conditions with permeability were made in order to determine the optimum method for fabrication of the membranes. It was determined that membranes produced with a lower molecular weight binder will have a higher permeability, higher porosity, and a larger pore structure than membranes produced with a higher molecular weight binder.
Fabrication of InAs Wires in Nanochannel Glass
Authors: Berry A. D. , Tonucci R. J. , Nguyen P. P. 
Published: April 2011

AbstractIndium arsenide wires have been fabricated in a glass host consisting of a high density array of uniformly shaped channels in a matrix glass. Reactions between organoindium compounds and arsine have produced polycrystalline InAs with crystallite sizes of approximately 10 nanometers when annealed at 400°C. At higher annealing temperatures, the wires exhibit an increase in surface porosity and grain size.
The Influence of Precursor Structure on the Development of Porosity in Polymer-Derived Sic
Authors: Nebo J. F. , Scotto C. S. , Bennett C. A. , Brinker C. J. 
Published: April 2011

AbstractPolymer-based routes to ceramic oxides take advantage of precursor chemistry and structure to produce materials with a range of pore sizes. Polymer precursor routes to nonoxide ceramics offer products with superior thermal and chemical stability in many cases. Polymethylsilane (PMS), a versatile cross linked SiC precursor, [(MeHSi)x(MeSi)y], was synthesized using published procedures to yield fluid precursors with a low (20–40%) degree of cross linking. Unique, highly cross linked (60–70%), solid polymers were produced under reaction conditions which carefully conserve the volatile monomer. These two polymers were converted to SiC to determine the relative importance of the various contributions to porosity, and to assess the role of precursor structure on porosity development in non-oxides. Initial results indicate that precursor structure has little effect on porosity. The development of the porosity appears to be dominated by high temperature thermochemistry and/or microstructural changes.
Formation and Properties of Porous GaAs
Authors: Schmuki P. , Lockwood D. J. , Fraser J. W. , Graham M. J. , Isaacs H. S. 
Published: April 2011

AbstractPorous structures on n-type GaAs (100) can be grown electrochemically in chloridecontaining solutions. Crystallographic etching of the sample is a precursor stage of the attack. Polarization curves reveal the existence of a critical onset potential for pore formation (PFP). The PFP is strongly dependent on the doping level of the sample and the presence of surface defects. Good agreement between the PFP and the breakdown voltage of the space charge layer is found. Surface analytical investigations by EDX, AES and XPS show that the porous structure consists mainly of GaAs and that anion uptake in the structure can only be observed after attack has been initiated. Photoluminescence measurements reveal – under certain conditions – visible light emission from the porous structure.
Nanoporous Polyimide Films from Polyimide-Aliphatic Polyester or Polyimide-Aliphatic Polycarbonate Copolymers
Authors: Carter K. R. , Hedrick J. L. , Richter R. , Furuta P. T. , Mecerreyes D. , Jérôme R. 
Published: April 2011

AbstractWe have explored polyimide foams created using a block copolymer approach as part of our research efforts to obtain thin film dielectric layers with very low dielectric constants for use in microelectronic devices. In these systems the pore sizes are in the nanometer range thus the term “nanofoam”, The polyimide foams are prepared from phase separated block copolymers consisting of thermally stabile and thermally labile blocks, the latter being the dispersed phase. Foam formation is effected by thermolysis of the labile block leaving pores the size and shape corresponding to the initial copolymer morphology. Polyimide nanofoams generated from thermolysis of polyimidealiphatic polyester and polyimide-aliphatic polycarbonate copolymers were investigated. The aliphatic co-blocks were synthesized by ring opening polymerization of the cyclic monomers, such as E-caprolactone, valerolactone, trimethylene carbonate, and L-lactide. The aliphatic blocks were designed in such a way as to allow for incorporation into polyimide copolymers. The foams were characterized by a variety of techniques including, TEM, SAXS, WAXD, DMTA, density and refractive index measurements.
Synthesis and Characterization of Ln/Al Pillared Clays
Authors: López-Ortega A. , Domínguez J. M. , Rojas-Hremández A. , Benitez-Patricio A. , Salmón M. 
Published: April 2011

AbstractLa3+ −Al3+ and Ce3+ −A13+ pillar precursors were synthesized and intercalated in swelling montmorillonite type clays. 27Al-NMR and 139La-NMR spectra do not confirm chemical interaction between Al and La ions in solution, but after pillaring and calcination (400°C) d-spacings in the range 18.5 Å−20.5 Å indicate indeed a strong interaction between the Al-La species. Also, Ce4+ (Sulfate) cations do interact with Al3+ in the pillar-precursor-solution, into the pH interval 2.78≤p.H ≤3.99.
Immobilization of Cobalt Complexes on Mesoporous MCM-41 Support Materials
Authors: Diaz J. F. , Bedioui F. , Briot E. , Devynck J. , Balkus K. J. 
Published: April 2011

AbstractThe pore surface of mesoporous MCM-41 type materials have been functionalized with silanes to yield surface bound chelate ligands that include ethylenediamine (ED), diethylenetriamine (DET) and ethylenediaminetriacetic acid salt (EDT). Additionally, The grafted DET ligand was reacted with salicylaldehyde to generate the supported tetradentate Schiff base ligand designated as DES. The MCM-41 bound ligands were used to prepare a series of covalently attached cobalt(II) complexes that potential as oxygen carriers and catalysts. These materials were characterized by FTIR and cyclic voltammetry as well as elemental analysis.
Synthesis and Colloidal Processing of Nanocrystalline (Y2O3-Stabilized) ZrO2 Powders by a Surface Free Energy Controlled Process
Authors: Burgard Detlef , Nass Rüdiger , Schmidt Helmut 
Published: April 2011

AbstractUsing the controlled growth technique, nanocrystalline ZrO2 powders have een prepared from solution. By variation of the Y-content (0-8 mol %), redispersable monoclinic, tetragonal or cubic ZrO2 powders with particle sizes between 5 and 10 mn were obtained after crystallization at elevated temperature and pressure. Nanodisperse suspensions of the powders have been used for colloidal processing techniques such as tape casting, slip casting or extrusion. The resulting green bodies with densities of 55 % and average pore sizes of 5 nm could be sintered at temperatures below 1100 °C leading to monoclinic, tetragonal or cubic ZrO2 ceramics.
Exafs Spectroscopic Studies of Uranium (VI) Oxide Precipitates
Authors: Allen P.G. , Shuh D.K. , Bucher J.J. , Edelstein N.M. , Palmer C.E.A. , Marquez L. N. 
Published: April 2011

AbstractWe have investigated the structures of U(VI) oxides precipitated from room temperature aqueous solutions at low ionic strength as a function of pH. Using the uranium LIII - edge extended x-ray absorption fine structure (EXAFS) as a probe of the local structure around the uranium, a trend is observed whereby the axial oxygen bond lengths from the uranyl groups increase from 1.80 Å at pH=7 to 1.86 Å at pH=11. A concomitant decrease in the equatorial oxygen and nearest-neighbor uranium bond lengths also occurs with increasing pH. Expansion of the linear O=U=O group is seen directly at the L111 absorption edge where multiple scattering resonances systematically shift in energy. EXAFS curve-fitting analysis on these precipitates and a sample of synthetic schoepite indicate that the structure of the species formed at pH=7 is similar to the structure of schoepite. At pH=11, the precipitate structure is similar to that of a uranate.
Synthesis and Characterization of Akaganeite-Like Ferric Oxyhydroxides
Authors: Linehan J.C. , Darab J. G. , Matson D. W. , Chen X. , Amonette J. E. 
Published: April 2011

AbstractAkaganeite, β-FeOOH, a natural ferric oxyhydroxide mineral, has a structure containing tunnel-like cavities in which chloride ions reside. Analogs of akaganeite in which carbonate or sulfate groups replace the chloride ions have also been synthesized. Both akaganeite and its substituted analogs are known to be precursors for active hydrocracking catalysts. We present powder X-ray diffraction (XRD) and X-ray absorption fine-structure spectroscopy (XAFS) data confirming the synthesis of new ferric oxyhydroxides having structures similar to akaganeite, but contain molybdate and tungstate oxy-anions. We also present a new hydrothermal method to prepare this family of materials.