bluuebunny/crossref_metadata_2025_split huggingface dataset:
Light Harvesting Molecular Assemblies in the Design of Highly Luminescent Sol-Gel Derived Glasses
Authors: Dulebohn Joel I. , Van Vlierberge Béatrice , Berglund Kris A. , Lessard Ronald B. , Yu Jeong-a , Nocera Daniel G. 
Published: March 2011

ABSTRACTSol-gel derived molecular composites exhibiting intense luminescence, induced from efficient energy transduction processes, have been prepared. The composites are comprised of an Eu3+⊂ 2.2.1 cryptate complex or native Eu3+ ion embedded in sol-gel derived titania glass films. The titania glasses contain interconnected porous networks that permit the diffusion of exogenous substrates, such as the salts of benzoic and 4-tert-butylbenzoic acids, through the film. Interaction of the substrate with the embedded lanthanide complex is indicated by enhanced luminescence from the lanthanide ion. The carboxylic acid salts whose electronic excited states are produced upon capture of incident photons, undergo facile transfer of their electronic energy to the lanthanide ion. By monitoring europium ion luminescence, the diffusion constants of the benzoate and 4-tert-butylbenzoate salts have been measured. Although the diffusion of the 4-tert-butylbenzoate is slower than that of benzoate, the overall higher sensitivity of the former is consistent with hydrophobic guest-host interactions. These new molecular composites relying on the immobilization of an absorption-energytransfer- emission molecular assembly in porous, optically transparent ceramic glasses may be useful in the design of practical sensing devices.
Nmr Spectroscopic Investigations of Pbtio3 Sol-Gel Processing
Authors: Ramamurthi S.D. , Payne D.A. 
Published: March 2011

ABSTRACTLead titanate gels were prepared by sol-gel processing from lead acetate and titanium isopropoxide in methoxyethanol. In the present study, 1H, and 13C FTNMR spectroscopic and mass spectrometric techniques were used to identify the structures of lead and titanium precursors formed by refluxing lead acetate and titanium isopropoxide in methoxyethanol, respectively. Lead acetate was found to be partially alkoxylated, whereas, the titanium precursor was identified as a dimer with complete alkoxy group exchange. Similar procedures were applied to identify the lead titanium complex formed from lead and titanium precursors.
Laser Densification Modeling
Authors: Chia Taipau , Hench L. L. , Qin Chaobin , Hsieh C. K. 
Published: March 2011

ABSTRACTA three-dimensional transient model for heat conduction in silica glass is developed. The model simulates a three-dimensional temperature distribution in a silica glass irradiated by a moving CO2laser. Both the reflectivity of the glass surface and the strong attenuation of the laser energy in the glass medium are accounted for by a detailed radiation analysis. The energy absorbed by the glass is determined to be confined in a 10 μm thickness; the laser irradiation is thus treated as a boundary condition. The heat diffusion equation is solved by an alternating direction-implicit method.
Emulsion Precipitation and Characterization of Zirconia
Authors: Shyu Lieh-Jiun , Cambria Frank M. 
Published: March 2011

ABSTRACTZirconia and yttria-stabilized zirconia (YSZ) powders were prepared from water/oil emulsions followed by high temperature calcination. The morphology and particle size were correlated with several variables such as composition of emulsions, concentration of starting materials and surfactants, stirring rate, hydrolysis rate and calcination temperature. The powders were characterized according to crystalline phase, particle size distribution, and flow rate. Emulsion precipitation typically yielded spherical zirconia particles which were either solid or hollow. Particle size could be controlled from submicron to a few hundred microns depending primarily on the composition of the emulsion and stirring rate during hydrolysis. SEM/EDX results showed that yttria was uniformly distributed throughout the zirconia particles. The crystalline phase of the powders after calcination at 800°C was entirely non-transformable tetragonal. The flow rate increased with increasing particle size and with increasing sphericity.
Review of Hydrolysis Behavior of Ions in Aqueous Solutions
Authors: Mesmer R. E. , Baes C. F. 
Published: March 2011

ABSTRACTThe word “hydrolysis,” literally “water splitting,” refers here to those reactions of metallic ions with water that liberate protons and produce hydroxy or oxy complexes in solution and precipitate hydroxide or oxide solids. Over the wide range of pH available in water, the strong tendency of hydroxide to bond to and bridge among cations leads to a multitude of species for many of the metals. Properties of the metal ion such as “hardness” and, especially, charge and size, determine the strength of these interactions and the species formed by each. Over 200 mononuclear species have been identified that predominate in dilute solutions across the pH scale. It is the stability of these species that largely determines the pH dependence of the solubility of the oxide or hydroxide solid formed. Both the tendency of the variety of polynuclear species (those containing more than one metal ion) to form and the solubility of the hydrolytic solid correlate with the stability of the first mononuclear species. Other correlations allow one to predict the enthalpy and entropy of a variety of hydrolysis reactions, and therefore the dependence of the stability of hydrolysis products on temperature.
Soluble and Volatile Precursors for the Preparation of Superconducting Films
Authors: Sauer Nancy N. , Garcia Eduardo , Ryan Robert R. 
Published: March 2011

ABSTRACTAttempts to identify intermediates in an alkoxide-based solution route to films of the high temperature superconductor YBa2Cu3O7 reported by Fahrenholtz et al.[1] have led to the isolation of the first molecular barium-copper cluster, Ba2Cu2(OR)4(acac)4·2 HOR, R = CH2CH2OCH3. The extension of this route to the preparation of the bismuth superconductors has necessitated the investigation of bismuth alkoxide chemistry. Two separate routes to bismuth alkoxides have been examined: the metathesis of the metal halides with NaOR, (R = t-butyl, and diisopropylphenoxide) and the alcoholysis of bismuth amides, Bi(NR2)3, [R = N(SiMe3)2] The alcoholysis preparation gives high yields of several alkoxides suitable as precursors to the high Tc materials. A monomeric bismuth phenoxide, which is targeted as a volatile precursor, and a bismuth t-butoxide cluster have been isolated and stucturally characterized. Solubility and volatility studies have also been undertaken.
Inorganic-Organic Composites (Ormocers) as Structured Layers for Microelectronics
Authors: Popall Michael , Meyer Henning , Schmidt Helmut , Schulz Jochen 
Published: March 2011

ABSTRACTEnhanced integration, faster signal transmission and reduced size of mounting devices in components for microelectronics requires new patternable materials. Inorganic-organic copolymers (ORMOCERs = ORganically MOdified CERamics), prepared by sol-gel techniques have been developed for interconnection technologies in microelectronics. Photopolymerization is enabled by unsaturated hydrocarbon or epoxide substituents and UV-sensitive initiators. Using a frequency doubled Argonion laser at 257 nm for direct laser writing, patterned layers with high edge quality have been realized. In combination with high breakthrough voltages, low permittivity constants and high bulk resistivities they open interesting aspects for very large system integration techniques (VLSI).
Investigation of Texture and Stress in Undoped Polysilicon Films
Authors: Huang J. , Krulevitch P. , Johnson G.C. , Howe R.T. , Wenk H.R. 
Published: March 2011

AbstractUndoped LPCVD polysilicon films deposited on thermal oxide and prepared under various process conditions have been investigated for their texture and stress characteristics. Pole figures measured by X-ray diffraction in reflection geometry were used to determine the orientation. distribution function which provides a quantitative description of the texture. Stresses were determined using wafer curvature measurements. Both texture and stress show substantial variation with deposition condition. Textures typically exhibit axial symmetry and appear to be correlated with the sign and magnitude of the stress. Under certain deposition conditions, the stress varies considerably along the tube, with the stress in the wafers at the upstream end being tensile and at the downstream end being compressive.
Characterization of Polysilicon Thin Films by Variable Angle Spectroscopic Ellipsometry
Authors: Xiong Yi-Ming , Snyder Paul G. , Woollam John A. , Krosche Eric R. , Strausser Yale 
Published: March 2011

AbstractVariable angle spectroscopic ellipsometry was used to characterize polysilicon multilayer structures. Five different multilayer wafers, each containing a polysilicon layer, were studied. Layer thicknesses and compositions were determined at several locations across each wafer. The thickness measurements obtained by ellipsometry are compared with those determined from cross-sectional transmission electron microscopy (XTEM).
High Performance Polysilicon Thin Film Transistors
Authors: Mitra U. , Khan B.A. , Venkatesan M. , Carlson A. , Vaez-Iravani M. 
Published: March 2011

AbstractPolysilicon TFT characteristics are shown to be dependent on the nature of the polysilicon film used as well as the TFT fabrication process. Best results were obtained when silicon self-implant and regrowth techniques were used together with plasma hydrogenation. TFTs exhibiting a mobility of 115 cm2/V-sec, subthreshold slope of 0.27 V/decade, leakage current below 0.01 pA/μ;m, and an on-off ratio of 10 orders of magnitude have been fabricated.
Polysilicon High-Voltage TFT with Field-Plate-Controlled Offset Region
Authors: Huang T. Y. , Wu I. W. , Lewis A. G. , Chiang A. , Bruce R. H. 
Published: March 2011

AbstractAn improved polysilicon high voltage thin film transistor (HVTFT) structure with field-plate-controlled offset region (FP-HVTFT) is proposed for eliminating the current-pinching phenomena often observed in the conventional offset-gate polysilicon HVTFTs. The new metal field plate serves, in lieu of ion implantation, to control the conductivity of the offset region. By properly biasing the field plate to distribute the drain electric field at both ends of the offset region, high-voltage operation of up to 100 V, suitable for many large-area applications, is achieved. Good turn-on characteristics without current-pinching effects are consistently obtained. Moreover, the new FP-HVTFT also eliminates the lightly-doped-drain implant normally required in conventional offset-gate HVTFTs, resulting in a simpler and more reproducible process flow.
Comparative Studies of Furnace and Rapid Thermal Passivation for Accumulation and Inversion Mode Polysilicon-On-Oxide Mosfets.
Authors: Batra S. , Park K. , Banerjee S. , Sundaresan R. 
Published: March 2011

AbstractCarrier transport in the channel region of polysilicon thin film MOSFETs is affected by the presence of grain boundary potential barriers and is further complicated by the modulation of the grain boundary barrier height with gate voltage. Passivation of the trap sites with atomic hydrogen reduces the barrier height and thereby improves the performance of polysilicon transistors. In this paper, we demonstrate the effectiveness of Rapid Thermal Annealing (RTA) using Si3N4 as a solid source of H as a passivation technique for both inversion and accumulation mode polysilicon MOSFETs. ON/OFF ratios of 107 can be obtained by RTA passivation for inversion mode polysilicon MOSFETs compared to 106 after furnace passivation permitting the potential application of these MOSFETs both as load transistors in SRAMs as well as pass transistors in DRAMs. In contrast, the ON&OFF ratio of accumulation mode polysilicon MOSFETs does not show any improvement even though ID and VT improve with passivation. This is because of excessive back channel leakage in accumulation mode MOSFETs which increases with passivation.
TiSi2 Thin Films Formed on Crystalline and Amorphous Silicon
Authors: Xiao Z.G. , Jiang H. , Honeycutt J. , Osburn C.M. , Mcguire G. , Rozgonyi G.A. 
Published: March 2011

AbstractTiSi2 thin films were formed on crystalline and amorphous silicon substrates obtained by Ge+ and Ge++B+ implantation and optional subsequent annealing. Transmission electron microscopy, X-ray diffraction and electrical resistivity analysis revealed that the silicide formed on amorphous Si has more tendency to have a C54 structure rather than the metastable C49 structure. Also, the grain size is smaller and the silicide/silicon interface is smoother for silicides formed on amorphous Si. Comparison between implanted and unimplanted, (100) and (111) Si substrates indicated that the origin of the differences can be attributed to the latent energy stored in amorphous silicon, which favors the silicide with fine grains and promotes the transformation to the C54 phase. Non-random distribution of planar defects in C49 grains has been observed by plan-view TEM. A proposal that these defects are transformation stress induced microtwins is presented.
High Resolution Study of CoSi2/Si (111) Interfaces
Authors: Catana A. , Lu Ping , Smith David J. 
Published: March 2011

AbstractThe atomic structure of A- and B-type CoSi2/Si (111) interfaces has been investigated by observations of samples in cross-section using a 400 kV high-resolution electron microscope. The samples were prepared by UHV e–beam evaporation of Co layers followed by annealing at temperatures between 300°C and 500°C. Based upon image simulations for various interface bonding models we have found evidence for 7–fold Co coordination at the A–type CoSi2/Si interfaces and for 7– and 8–fold coordination at the B-type interfaces.
Hrem and Nano-Scale Microanalysis of the Titanium-Silicon Interfacial Reaction
Authors: Kouzaki T. , Ogawas S. , Nakamura S. 
Published: March 2011

AbstractThe interfacial reaction of titanium with single crystal silicon has been characterized using high-resolution electron microscopy(HREM) combined with nano-scale microanalysis. HREM shows that there is an amorphous interdiffused alloy formation at titanium-silicon interfaces. The reacted layer is about 1.7nm thick for single crystal silicon, but is 2.5nm thick for sputter-amorphized silicon. Annealing increases the thickness of the amorphous alloy. We have used high-spatial-resolution microanalysis to obtain energy dispersive spectrometry (EDS) using a 2nm probe size. The results clearly show that reliable composition analysis can be obtained at this level since some of the layers are only about 2nm thick. It was found that the amorphous alloy composition was Ti55Si45for the sputter-amorphized silicon. Futhermore we ascertained no induced reaction by 2nm probe electron beam irradiation.
Hrem Study of α-Si3N4 Precipitates in Silicon
Authors: De Veirman A. , Broddini D. , Van Landuyt J. , Skorupa W. , Voelskow M. 
Published: March 2011

AbstractNitrogen and also sequential nitrogen/oxygen implantations at an energy of 330 keV result in the formation of α-Si3N4 precipitates below the buried layer. A particular orientation relation between the α-Si3N4 and the Si lattice was established: the basal (00.1) α-Si3N4 plane is parallel to one of the Si {111} planes. Planar defects with (00.1) habit planes have been identified by HREM as stacking faults with a displacement vector of 1/3<10.0>.
High-Resolution STEM Observations of Nanometer-Sized Cavities in Rapidly Solidified 304 Stainless Steel
Authors: Kelly Thomas F. , Shin Keesam , Bae Jung Chan , Noll Richard K. , Flinn John E. 
Published: March 2011

AbstractBased upon coarsening studies of larger cavities (8 nm) in a rapidly solidified 304SS, it was determined that there should be a large number of very small cavities (1–2 nm) in these materials that are too small to observe with out-of-focus imaging techniques on a conventional TEM. Out-of-focus imaging on a high-resolution TEM could also be used but ambiguities would remain in the interpretation of the origin of the image contrast. In order to overcome these problems of ambiguity, the annular dark field (ADF) image on a VG HB501 STEM was employed. Since this signal is proportional to mass thickness and Z3/2, we expected that the change in mass thickness locally associated with a cavity would be detectable in a thin enough region. These images show a clear correlation between features in the BF through-focus series which behave as cavities and features in the ADF image. This combination of imaging modes has provided convincing evidence for existence of the 1 nm cavities.
Solving Defect Structures by Hrtem: Expectations and Limitations
Authors: Barry John C. 
Published: March 2011

AbstractMost metals have small unit cells, and in small unit-cell materials in low-index zones the strength of the diffracted beams is often greater for lighter metals than it is for heavier metals. The reason for this is that the strong double-diffraction in heavy metals gives rise to weak Bragg diffraction. In this paper it is shown that for small unit-cell materials, light atom precipitates can be easily detected in heavy atom matrices; and that in large unit-cell materials, the breakdown in the weak-phase-object approximation in thick crystals can be used to identify atom type at defects.
Hrem Visualization of Light Atoms: An Application to the Study of Carbon Defects in Ordered Transition Metal Carbides
Authors: Epicier T. 
Published: March 2011

AbstractThis paper gives an overview of recent High Resolution Electron Microscopy (HREM) observations of transition metal carbides. The main point is to show how HREM can be used to study a sublattice of light atoms within a complex crystal. General tendencies of this approach will be outlined, which appear, to a large extent, to be common to similar possible studies of other compounds such as nitrides, borides or oxides. Specifically, attention is focused on studies of long-range ordered structures in carbides, due to non-stoichiometry accommodated by metalloid vacancies. Various examples are given for representative compounds, including V8C7, V6C, 5, Nb6C5 and W2C.
Hrtem Observations of Sol-Gel Derived Yag and Alumina/Yag Thin Films
Authors: Hay R. S. 
Published: March 2011

AbstractThin films of YAG and YAG/alumina mixtures were prepared by gelling a sol across a TEM grid. The grids were heat-treated to temperatures as high as 1550°C. The resulting ceramic thin films were observed by standard and high resolution TEM techniques. Ion-milling, carbon coating, or other specimen preparation was not necessary. The phase and microstructure evolution, as well as pore structure evolution and spheroidization of film edges could be easily observed. Abnormal grain growth was observed in yttrium-aluminum garnet (YAG) films. Lattice images were taken of the matrix, abnormal grains, and structures that evolved from the abnormal rains at higher temperatures. The grain size preceding abnormal grain growth was 20–50 nm. The abnormal grains were composed of 20–50 nm subgrains with up to several degrees of misorientation. High resolution observations were also made of small (< 0.2 μm) YAG inclusions in alumina. An orientation relationship of (111)[011]alumina//(112)[021]YAGwas observed. This orientation relationship was not observed in large inclusions.
Interdiffusion in Metallic Layers
Authors: Bourret A. , Rouviere J. L. 
Published: March 2011

AbstractThe atomic structure of ion-sputtered Fe/Ti multilayers with an average composition FeTi2 is studied by high resolution electron microscopy. A systematic use of diffractometry is made to measure the local parameter change as well as to recognise the crystalline phase. Local lattice parameter changes are attributed to compositional changes indicating interdiffusion at a scale of 1.8 nm. The phases are very dependent on the multilayer period, Λ. For small periods, Λ < 4 nm, the layers are amorphous. For intermediate periods 4 nm < Λ < 8 nm the Ti-rich layer is crystalline. And for larger periods both the Fe-rich and the Ti-rich layers are crystalline. These observations are explained in terms of a growth model, assuming a constant depth of mixing during sputtering.
High Resolution Transmission Electron Microscopy of Aluminophosphates; Proposed Structure for AlPO4–8
Authors: Ulan Judith G. , Szostak Rosemarie , Sørby Kristin , Gronsky Ron 
Published: March 2011

AbstractVPI-5 transforms to AlPO4–8 under mild thermal treatment (100 °C, 18 hrs). HRTEM micrographs, oriented normal to the c axis, show extensive defect-free regions in VPI-5, while slip planes normal to the c axis are found in AlPO4–8. Analysis of the HRTEM data, in conjunction with infrared and thermal analysis, adsorption studies and x-ray powder diffraction, has lead to a proposed structure for AlPO4–8. Though the sheets containing the 18 member rings which define the pores in VPI-5 remain intact in AlPO4–8, reduction in the porosity is attributed to blockages created by the movement of these sheets relative to each other.
High-Resolution Electron Microscopy of Process-Induced Defects in Silicon
Authors: Cerva Hans , Oppolzer Helmut 
Published: March 2011

AbstractSeveral examples of defect characterization which are of topical inter-est to Si device technology are presented. The results obtained by high-reso-lution electron microscopy (HREM) are discussed in context with the actual defect problem. - Reinvestigation of platelike defects in Si produced by reactive ion etching in hydrogen containing plasmas (CHF3) shows that some of the {111} platelets are of extrinsic nature. The defects contain probably both constituents from the plasma and Si-interstitials created by the impin-ging ions. - A high dose As-implantation forms an amorphous Si surface layer which has a sharply curved amorphous/crystalline (a/c)-interface below the implantation mask edge. Annealing at 900°C leads to formation of vacancy-type defects under the mask edge. This is due to the different regrowth rates on the various lattice planes of the curved a/c-interface. - Metal-silicide pre-cipitation at the SiO2/Si interface reduces the breakdown field strength of thin oxides. The main failure mechanism observed in model experiments is the thinning of the oxide layer thickness. - Additional x-ray peaks which are frequently observed in low-pressure chemical vapour deposited (625 7deg;C) po-lycrystalline Si layers arise from a diamond hexagonal Si phase. Small inclu-sions and bands of this phase were for the first time directly observed by HREM.
Stability of Multilayered Semiconductor Systems
Authors: Kim Y. , Ourmazd A. 
Published: March 2011

ABSTRACTWe have studied the atomic scale relaxation of multilyered semiconductor systems through interdiffusion, and its implications for layer and hence device stability. Our technique combines chemical lattice imaging and vector pattern recognition to measure interdiffusion coefficients as small as 10-20 cm2/s at single AiGaAs/GaAs interfaces. Our results can be summarized as follows. (a) The interdiffusion coefficient and hence layer stability depend strongly on the distance from the top surface. (b) The strong influence of the surface stems from its role as the source of rative point defects (interstitials, vacancies) involved in the diffusion process. (c) The study of the initial transients in the diffusion process can directly yield the migration and formation energies of these defects as a function of their charge state. (d) The non-linear nature of the diffusion process can have serious consequences for the low temperature stability of multilayered materials and devices. We also discuss the implications of our results for the design and fabrication of stable multilayered systems.