bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Dynamics Simulations of Ion Beam Mixing at Subthreshold Energies in Metallic Superlattices Structural Effects
Authors: Mazzone A. M.
Published: March 2011

This work presents results of molecular dynamics simulations of the intermixing of a heterostructure formed by a Fe-Ag bilayer of thickness of few tens of Å. The intermixing is generated by As+ ions with energy of few eV. It has been found that the structure of the lattice has profound effects on mixing and disordering.
Physical and Chemical Effects of Focused Ga-Ion Beam on GaAs (100)
Authors: Chen Wei , Chen P. , Viswanathan R. , Madhukar A. , Chen Jun , Kaviani Kian , Xie Q. , Hu Kezhong
Published: March 2011

Ga droplet formation on GaAs(100) substrates milled by focused Ga ion beam is studied using scanning electron microscopy and scanning Auger microscopy. It is found that Ga droplet formation requires a threshold Ga+ dose of ∽ 1016/cm 2 and is closely correlated to the formation of Ga overlayer at the milled surface and the increase in Ga concentration by ∽ 32% in the subsurface region. The Ga droplet evolution appears to be driven by the instantaneous energy deposited continuously by the ions.
Temperature Dependence of Ion-Beam-Induced In-Plane Stress in Silicon
Authors: Yuan J. Z. , Hartmann R. , Verner I. V. , Corbett J. W.
Published: March 2011

Experiments were conducted to determine the sample temperature dependence of ion-beaminduced in-plane stress in silicon. Implantations were carried out for B+, Ar+ and Ti+ at various dose ranges and different silicon temperatures. The ion-beam-induced surface stress was measured by using a newly developed technique, which has a high sensitivity. A large abnormal stress was observed for B+ implantation at room temperature. The results show that the silicon temperature has a significant effect on the ion-beam-induced stress. The influence of temperature on stress curves were presented. This effect is consistent with the temperature effect on the ionbeam-induced amorphization of silicon. However, the effect on chemically active ions, such as B+, is significant, indicating that some preferable temperature can be used for minimizing ionimplantation-induced stress.
Correlation between Chemical Modification and Generated Refractive Index on Ion Implanted PMMA
Authors: Kallweit R. , Roll U. , Eichinger P. , Strack H. , Pöcker A.
Published: March 2011

The optical characteristics of polymethylmetacrylate (PMMA) can be changed selectively with the aid of ion implantation. This can be explained by the manner in which the chain molecules are decomposed by the bombardment. New binding states can be identified by means of XPS on the irradiated surface and traced throughout the implantation depth using dynamic SIMS. In order to avoid chemical reactions, inert gas ions, ranging from He to Xe, have been implanted at energies between 100 keV and 380 keV, and fluences from 1 × 1013 /cm2 to 7 × 1015 /cm2. The results indicate a correlation of the refractive index and the surface layer contraction with surface CH- and COH-groups generation (XPS) and with in-depth damage described by the emission of secondary ions with masses 26 and 42 (SIMS), assigned to (CH2)- and (C2OH2)-.
Oxygen-Doped-Silicon/Silicon Heterointerfaces by Ion Implantation
Authors: Srikanth K. , Ashok S.
Published: March 2011

We have investigated oxygen ion implantation at substoichiometric doses for bandgap modification in silicon. Redistribution of the oxygen atoms during the high temperature anneal results in sharp interfaces aiding the formation of a heterojunction. A most interesting observation is the presence of donors in the vicinity of the implanted region, resulting in extensive counterdoping. Mesa type diodes on the implanted sample exhibit excellent rectification with a diode ideality factor n of 1.2 and a reverse saturation current density of 1 × 10−8 A/cm 2. The near surface region is shown to be crucial for achieving the high rectification behavior.
Detailed Model of the Afterglow Region of a Microwave Generated Oxygen Plasma
Authors: Chou Chin-Hao , Wei Ta-Chin , Phillips Jonathan
Published: March 2011

A one dimensional mass continuity equation was used to model a low pressure, high radical concentration, non-isothermal oxygen afterglow reactor. The mathematics are very similar to those used to model flames. It was shown that the model, with no adjustable parameters, yielded very good agreement with experimental measures of O-atom flux. The model was manipulated to study the influence of temperature profile, pressure, homogeneous and heterogeneous kinetics, O-atom generation and flow rate on the afterglow plasma.
New Approaches for Dry Etching Metal Oxides at low Temperature and High Rates
Authors: Rousseau Francois , Jain A. , Perry L. , Farkas J. , Kodas T. T. , Hampden-Smith M. J. , Paffett M. , Muenchausen R.
Published: March 2011

The reactions of metal oxides including CuO, ZnO, V2O5, and PbO with 1,1,1,5,5,5-hexaflouro- 2,4-pentanedione (hfacH) were investigated. A hot-wall reactor was used to react hfacH with metal oxide powders to form sufficient quantities of volatile reaction products for characterization by Infrared Spectroscopy (IR), Elemental Analysis (EA), Nuclear Magnetic Resonance (NMR), Mass Spectroscopy (MS), Thermogravimetric Analysis and Differential Thermal Analysis (DTA). PbO, ZnO and CuO powders reacted rapidly at 200 °C to form the corresponding metal β-diketonates and V2O5 reacted to give OV(hfac)2. A differential cold-wall reactor was to used to measure etch rates of CuOx films as a function of temperature and hfacH partial pressure. AES and XPS analysis of the laser ablation deposited CuOx film annealed in an O2 atmosphere revealed that the film was composed of CuO and Cu2O. Etch rates of up to a I l.βm/min at hfacH partial pressure of 1 Torr at 270 °C were obtained. Laser induced etching of the same CuOx film with hfacH showed evidence of copper oxide removal.
Removal of Surface Carbon Impurities from Ultra-Low Loss Fluoride Glasses
Authors: Sanghera J. S. , Pureza P. C. , Aggarwal I. D.
Published: March 2011

This paper describes a novel route for removal of surface carbon from heavy-metal fluoride glasses melted in vitreous carbon crucibles. The technique utilizes dry etching with active fluorine produced in a NF3 plasma generated in a microwave cavity.
Amorphous Soft Magnetic Material Formation by Ion Mixing
Authors: Gerard P. , Suran G. , Blanchard B. , Devenyi J. , Dupuy M. , Martin P.
Published: March 2011

Ion mixing of FeNi-Si multilayers is performed at the same dose of 3.1015 Xe+ cm−2 with either of the three energies 200, 300 or 400 keV. The irradiation is done at liquid nitrogen temperature (LNT) or at room temperature (RT). The mixed layers are characterized by reflection high energy electron diffraction (RHEED), transmission electron microscopy (TEM), Rutherford backscattering (RBS), secondary ion mass spectroscopy (SIMS) and ferromagnetic resonance (FMR). Films made at 400 keV are more reproducible and as homogeneous as the best amorphous films realized up to now, using sputtering techniques.
A New Hafnium-Beryllium System Prioduced by Ion Implantation and Annealing Techniques
Authors: Soares J.C. , Melo A.A. , DA Silva M.F. , Alves E.J. , Freitag K. , Vianden R.
Published: March 2011

Low and high dose hafnium imolanted beryllium samoles have been prepared at room temperature by ion implantation of beryllium commercial foils and single crystals. These samples have been studied before and after annealing with the time differential perturbed angular correlation method (TDPAC) and with Rutherford backscattering and channeling techniques. A new metastable system has been discovered in TDPAC-measurements in a low dose hafnium implanted beryllium foil annealed at 500°C. Channeling measurements show that the hafnium atoms after annealing, are in the regular tetrahedral sites but dislocated from the previous position occupied after implantation. The formation of this system is connected with the redistribution of oxygen in a thin layer under the surface. This effect does not take place precisely at the same temperature in foils and in single crystals.
Implantation Induced Filamentary Structures
Authors: Jaussaud C. , Maillot B. , Bruel M.
Published: March 2011

Heavy rare gases implantations have been performed in layered structures : Sb/In/Si bulk and Sb/Ga/Si bulk. Layer thicknesses lie in the range of 150 Å – 600 Å, ion doses in the range of 1014 cm−2 – 1016cm−2

Ion implantation induces in such structures a change in the visual aspect from a metallic appearance to a dark black aspect. This modification corresponds to the creation of voids with, as a consequence, the expansion of the structure. This effect is so important that even for low and medium doses, the structure becomes filamentary. Expansions as high as 2,8 μm have been measured. SEM photographs illustrate this spectacular effect.

Relations between expansion and implantation parameters are given. A comparison between this effect and those observed in bulk InSb, GaSb and Ge is presented.
Ion-Beam Processing of Ion-Implanted Si
Authors: Dietrich H.B. , Corazzi R.J. , Tseng W.F.
Published: March 2011

Substrates can undergo major temperature excursions during ion implantation if they are not well heat sunk. At power densities on the order of 50 watts per cm−2 radiatively cooled Si will melt in a matter of seconds. Such power densities can be maintained over a few sq. cms with many of the beams produced by even the moderate current machines currently used for doping Si and the III-V's. We have made use of this fact to study pulsed ion-beam annealing of implanted Si. Two types of studies have been carried out. In the first, 5–20 sec proton irradiations were done at power densities of 3–35 watts cm−2 to produce sample temperatures of 500 to 1100°C. 2×1016 cm−2 280 keV B, BF2 , As and P implants were annealed in this manner. Sheet resistances, ρs, versus power density curves were obtained for each ion and compared to psρs vs T data obtained for furnace annealed companion samples. In the second study the 2×1016cm−2 280 keV implants were carried out at progressively higher current densities so that the dopant beam itself raised the sample temperature to 500–1000°C. For each ion (other than B) it was possible to obtain power densities which resulted in self-annealing implants whose sheet resistances were as low as those obtained with the optimal furnace anneal. Details of the experiments, electrical and physical properties of the pulsed ion-beam annealed layers and device applications will be presented in this paper.
Lattice Site Location of Group VII Impurities in Silicon
Authors: Boerma D.O. , Smulders P.J.M. , Wierenga T.S.
Published: March 2011

Chlorine- and iodine-implanted silicon have been investigated using the channeling/RBS technique after laser and oven annealing. Both annealing methods result in good epitaxial recrystallization of the implanted layer. A large near-substitutional I fraction exceeding 90% was found after oven annealing at 875°C. The near-substitutional fractions found after laser annealing for Cl and I, and after thermal annealing at 900°C for Cl are in the order of 50% only. The precise lattice site for these Cl and I fractions are determined by fitting the angular scans with simulated results. The results are interpreted in terms of vacancy association.
High Resolution Transmission Electron Microscopy Study of Se+ Implanted and Annealed GaAs
Authors: Sadana D.K. , Sands T. , Washburn J.
Published: March 2011

High resolution transmission electron microscopy (HRTEM) has been applied to the study of amorphization and recrystallization mechanisms in Se+ implanted (100) GaAs. An Se+ dose of 1 × 1014 cm−2 at 450 keV (projected range 1550Å) produced an amorphous band in the depth range 250 to 2150Å below the surface. Annealing at 400°C resulted in the epitaxial regrowth of the upper and lower transition region (0–250Å and 2150 – 2500Å, respectively). Regrowth of the amorphous layer was found to proceed by the nucleation and propagation of the dense network of stacking faults bundles. These bundles disappeared on higher ≥600°C) temperature annealing. Amorphization and recrystallization mechanisms in Se+ implanted GaAs are discussed in light of these HRTEM results.
Ion Implantation in Gallium Indium Arsenide
Authors: Anjum M. , Shahid M. A. , Gill S. S. , Sealy B. J. , Marsh J. H.
Published: March 2011

We have studied the formation of heavily doped n-type layers in LPE GaInAs using ion implantation. 400 keV selenium ions have been implanted in dose ranges of 5 × 1013 to 1 × 1015 cm−2 at room temperature. For the high dose implants we have reproducibly achieved activities of 20–40% and sheet Hall mobilities of 700–1000 cm−2 V−1 s−1 and peak carrier concentrations of about 1019 cm−3. TEM and RBS results indicate that for long time anneals residual damage persists in the implanted layers, however, anneals at 800°C for 30 seconds perfectly recrystallize the implanted layers.
Microstructural Development of TiB2 Ion Implanted with 1 Mev Nickel
Authors: Sklad P. S. , Angelini P. , Lewis M. B. , Mchargue C. J.
Published: March 2011

An Analytical Electron Microscopy (AEM) investigation of polycrystalline TiB2 implanted with 1 MeV Ni+ to 1 × 1021 ions/m2 has shown that the implanted region remained crystalline and showed no evidence of precipitation. A region containing tangled dislocations extended from the implanted surface to ∼500 nm. Between ∼500 and 750 nm, the microstructure was more complicated and could be indicative of a high density of 5 to 10 nm diam defects. The maximum nickel concentration determined by energy dispersive spectroscopy (EDS) occurred at ∼450 nm, slightly deeper than the calculated depth of 390 nm. Observations after in situ annealing revealed cavities and nickel-rich precipitates. Radiation damage models are invoked to explain the microstructures observed.
Chemical and Physical Interactions in Covalent Polymers Implanted with Transition Metals
Authors: Pehrsson Pehr E. , Weber D. C. , Koons N. , Campana J .E. , Rose S.L.
Published: March 2011

Multiple analytical techniques including FABMS, XPS/Auger, magnetic susceptibility,and conductivity are used to probe the effects of transition-metal implantation on the structural and physical properties of covalent polymers and HOPG. Post-implantation chemistry and solid-state interactions between the implanted atoms and the polymer are investigated.
Surface Modification by Ion Beam Enhanced Deposition
Authors: Kant R. A. , Sartwell B. D.
Published: March 2011

Copper films given multiple sequences of Ta implantation and Cu depositions were analyzed using electron microscopy, backscattering, and Auger spectroscopy. Ta retention is 92% following direct implantation, and 100% retention was achieved for the same Ta dose if sputtered Cu is replaced during implantation. Lateral migration of Ta and microroughness were observed for all cases studied. Evidence for TaC formation is presented.
H Implantation Improves Superconductivity in Non-Transition Metals
Authors: Ochmann F. , Stritzker B.
Published: March 2011

The superconducting transition temperature, Tc, of a series of non-transition metals was improved by implantation of H and D into these metals kept below 10 K. In all cases the increase of Tc was considerably larger for H and D implantation with respect of He implantation causing only radiation effects. It could be shown that the enhancement of Tc depends on the electron-phonon coupling constant of the host metal, suggesting that mainly phonon effects dominate the improvement of Tc.
Retention of Ions Implanted at Non-Normal Incidence
Authors: Grabowski K.S. , Hartley N.E.W. , Gossett C. R. , Manning I.
Published: March 2011

Future applications of ion implantation require a knowledge of how the retention of implanted ions varies with angle of ion incidence. In this work the retention of 150-keV Ar,Ti,Cr,and Ta ions in AISI-M50 and 52100 bearing steels was measured for incidence angles up to 60° off normal. Fluences between 3×1015 and 3×1017/cm2 were used, typically on 3/8” diameter cylindrical samples. Retention was measured for Ar, Ti, and Cr by ion induced x-ray emission and for Ta by backscattering of He ions. Range and sputtering parameters needed for model calculations were experimentally determined from Ta-implanted thin Fe film samples. Generally, at the low-fluence limit a near-cos θ dependence obtained while at the high-fluence limit a (cos θ)8/3 dependence applied where θ is the angle between the sample normal and the beam direction.
The Reduction of Wear and Wear Variability Under Lubricated Sliding by Ion Implantation
Authors: Au J.J. , Sioshansi P.
Published: March 2011

Block-on-ring wear tests were performed on Ti-implanted AISI 52100 steel sliding against three commercial alloys: CDA 673 brass, AISI 4140 low alloy steel, and AISI 0–6 tool steel. A turbine oil, meeting MIL-L 23699 specifications, was used as the lubricant. The 52100 wear rings were ion implanted to a fluence of 2 × 1017 Ti/cm2 at 55 KeV or 125 KeV. Comparison with non-treated 52100 wear rings indicated that ion implantation reduced the amount of wear and wear variability. It is hypothesized that reduced adhesion and improved lubricant film formation due to the presence of the implanted layer was responsible for the reduction in wear and wear variability.
Study of Ion Bombardment-Induced SubSurface Compositional Modifications in Ni-Cu Alloys at Elevated Temperatures by Ion Scattering Spectroscopy
Authors: Lam N. Q. , Hoff H. A. , Wiedersich H. , Rehn L. E.
Published: March 2011

Changes in the subsurface composition of Ni-40 at.% Cu alloys during 3-keV Ne+ bombardment at temperatures between 25 and 700°C were studied by means of ion scattering spectroscopy.Both the time evolution of the composition in the surface atom layer during ion bombardment and subsurface concentration profiles after rapid specimen cooling to room temperature were measured as a function of temperature. Radiation-enhanced diffusion coefficients were derived from the effective altered-layer thicknesses obtained. A comparison of the experimental measurements with theoretical calculations based on a phenomenological model enabled the identification of processes and kinetics responsible for subsurface compositional modifications.
Boltzmann Approach to Cascade Mixing
Authors: Manning Irwin
Published: March 2011

The Boltzmann transport equation is used to describe a beam of ions of atomic species 1 (1-atoms) bombarding a target modelled as an amorphous mixture of 2-atoms and 3-atoms. In a manner familiar in nuclear reactor theory, the method of characteristics is used to integrate the resulting transport equations. An exact expression for the migration flux J3 of 3-atoms is obtained in closed form. This expression can be evaluated in terms of a power series in a distance parameter s. For the case of slowly varying density N3 of 3-atoms, Fick's law, relating J3 to the gradient of N3, is derived from this expression; it is given by the lowest order term of the power series. J3 is shown to be proportional to the bombarding flux. Concomittantly, a closed expression for the mixing parameter in Fick 's law is obtained, which allows a calculation of this quantity for realistic interatomic potentials. A model Kinchin-Pease displacement cascade is proposed, which is expected to allow a reasonable first approximation calculation of the mixing parameter in Fick's law. It is deduced that the mixing parameter will depend sensitively on the lattice displacement energy. This dependence constitutes a physical mechanism for chemical effect in cascade mixing, as well as for fluence and temperature dependence of cascade mixing.
Aggregation and Hydrolysis Reactions of Bismuth Alkoxides
Authors: Whitmire Kenton H. , Jones Carolyn M. , Burkart Michael D. , Chris Hutchison J. , McKnight Andrew L.
Published: March 2011

New bismuth alkoxide and oxo-alkoxide complexes have been prepared from the salt metathesis reaction of NaOR with BiCl3. When R = CH(CF3)2, the product is [Bi(μ- OR)(OR)2(THF)]2 Similar work with R = C6F5 has not yielded a simple alkoxide, but complexes of formulation NaBi3(μ3-O)(OR)8(THF), NaBi4((μ3-O)2(OR)9(THF)2, Na2Bi4(μ3- O)2(OR)10 and Bi6(μ3 -OR)(μ3 -O)4[μ3-OBi(OR)4]3 have been observed. The reaction of BiPh3 with HOC6F5, however, did produce the desired alkoxide which has been characterized as [Bi(OR)2(μ-OR)(toluene)]2 and [Bi(OR)2(μ-OR)(toluene)[2.2 toluene. The reaction of this alkoxide with NaOC6F5 led to the production of Bi6(ν3--O)2 (μ4-O)(OR)12 and NaBi3(μ3- O)(OR)8(THF)3. Reaction of BiPh3 with HOC6F5 in THF led to the formation of Bi6(μ3-OR)(μ3-O)4[μ3-OBi(OR)4]3 (THiF)2. Surprisingly the reaction of BiEt3 and HOR (R = C6F5 or Ph) displaced only one Et group to give [Et2Bi(μ-OR)]∞ which exist as infinite chain polymers with alternating Bi-O-Bi backbones. These spiral chains form chiral helices in the crystal lattice.
Preparation of BSCCO Precursors by Water Extraction Variant of Sol-Gel Process
Authors: Deptula A. , Lada W. , Olczak T. , Di Bartolomeo A.
Published: March 2011

The starling acetate sols of molar compositions of Bi:Pb:Sr:Ca:Cu=I-2:O:2:l: 2, 11–2:0:2:2:3 and 111–1.6:0.4:2:2:3 were prepared by NH4OH addition at various rates, followed by evaporation. Sols were gelled by further evaporation to shard or to microspheres (diameter below 100 μm) by water extraction from the sol emulsion drops formed in 2-ethyl-l-hexanol. The gels were converted to BSCCO phases by thermal treatment. The processes were characterized by XRD and IR examinations. The influence of the sol preparation step connected with formation of polynuclear cations on the following stages of the process was examined.
Fractal Growth During Gelation
Authors: Pope Edward J. A.
Published: March 2011

Sol-gel processing has emerged as an important new technology for the fabrication of a wide variety of glass, ceramic, and composite materials. In order to better understand and control the gelation process, a theoretical model has been developed which quantitatively links features of fractal growth with measurable properties of a solution during the sol-gel transition. The result of that effort is the fractal growth model of gelation (FGMG) which expresses the solution viscosity, light scattering, and refractive index changes as a funtion of time and the fractal dimension. In this paper, the application of FGMG to silica gels and multi-component system, such as titanium aluminosilicates, is presented.
Solvent Quality Effects in Sol-Gel Processing
Authors: Bailey Joseph K.
Published: March 2011

To understand how solvent quality can be used to tailor structure in sol-gel processing of silicon alkoxides, polymerized tetramethoxysilane polymers were synthesized and fractionated to give relatively stable, narrow molecular weight dispersion samples. These polymers had molecular weights ranging from 8000 to 45,000. The solubility parameter range for these polymers is 8.9–14.5 (cal/cm3)1/2. Light scattering confirmed that this range could be used to predict solvent quality. Bulk gels prepared using good versus poor solvents demonstrated that solvent quality can be used to tailor properties of the gels, presumably by modifying the extent of interpenetration of the growing polymers.
Electronegativity-Based Computation of29Si Chemical Shifts
Authors: M Henry. , C Gerardin. , F Taulelle.
Published: March 2011

The Partial Charge Model has been modified to take into account the detailed structure of any molecular sol-gel precursors or inorganic solid networks. Starting from these structure-dependent partial charges, the classical theory of nuclear shielding is applied to compute the electronic cloud compacity p, the population unbalance Puand also the mean excitation energy ΔE. With these three parameters it is possible to explain the chemical shifts variations, spanning from +40 down to -140 ppm, of more than 50 precursors. Depending on the ligands, the well-known upside-down U-curves for series SiXnY4-n(n=0‥4) can be ascribed either to the population unbalance term Puor to a competition between the two other terms pand ΔE.
Raman and Infrared Study of Metal Alkoxides During Sol-Gel Process
Authors: Poncelet O. , Robert J -C. , Guilment J.
Published: March 2011

Organic additives are commonly used in sol-gel chemistry [1]. They can operate as stabilizers of reactive metal alkoxides [2] towards hydrolysis or as drying control chemical additives (such as dimethylformamide). These organic compounds and the by-products of sol-gel reactions can drastically modify the physical properties of final oxide materials, so that it is necessary to optimize the use of these additives. The first steps of hydrolysis of metal alkoxides stabilized by organic additives have been studied by many sophisticated analytical techniques which are difficult to use at technical level and often strongly alter the sol-gel reactions [3]. We chose to use FT-Raman and Infrared spectrocopies, which allow to remain as close as possible of the sol-gel process without altering it. The first steps of hydrolysis of group (IVb) metal alkoxides, more particularly titanium, modified by chlorides, carboxylic acids and alkanolamines have been investigated.
Production of Spherical Powders of Inorganic Compounds by Water Extraction Variant of Sol-Gel Process
Authors: DeptuLa A. , Rebandel J. , Drozda W. , Lada W. , Olczak T.
Published: March 2011

A method of preparation of spherical powders (with particle diameters <100µm) of metal oxidcs, their homegeneous mixtures or compounds, composites and metals has been elaborated. Depending on the nature of cations, the starting solutions were prepared by extraction of anions with Primene JMT from salt solutions, by addition of dopants to the sols or by complexing with acetic acid or/and ammonia. The sols or broths were then emulsified in 2-ethyl-l-hexanol containing SPAN 80. Drops of the emulsion were solidified by extraction of water with the solvent. The process was carried out continuously in a laboratory and/or in a pilot plant.
The Fast Sol-Gel Synthetic Route to Supported Glass Films: Synthetic Features, Scope, Applications and Mechanistic Studies
Authors: Haruvy Y. , Webber S. E.
Published: March 2011

The fast sol-gel synthetic route to glass films is facilitated by a solvent-free reaction of trialkoxysilane monomers at 60–80°C and near-stoichiometric water-to-siloxane ratios. The viscous polymer formed within several minutes is spin-cast onto a support (typical thickness 10–25µm), cured within a few hours at 60–70°C or 10–40 min. under an intense electric field at room temperature, and can be characterized on the same day. Multi-layered glass-film assemblies of varying indices of refraction and a total thickness up to 80µm are prepared by the same fast process with slight modifications.

Guest molecules such as laser dyes for 2D lasers and chromophores for second-harmonic-generation are incorporated into these glass films at high concentrations by direct addition to the reaction mixture. Their absorbance and fluorescence spectra are typical of monomeric chromophores up to concentrations of ∼10-2M. Crystallites that may appear at higher concentrations exhibit unusual polymorphism. The smoothness of such films enables surface anchoring of iso-environment photoactive molecules and investigation of their photophysics.

29Si-NMR studies of the hydrolysis pattern in our acid-catalyzed fast sol-gel reaction prove that uniform hydrolysis of the monomer, necessary for a single-phase polymerization, is attained only when the hydrolysis is fast enough to become kinetically controlled, e.g. at elevated temperature or at high acid-concentration. Our reaction pattern and the data of others can be interpreted in terms of a single mechanism of hydrolysis in which two different rate-determining-steps can prevail, depending predominantly on the reactivity of the alkoxysilane and the ratio of the acid-catalyst to the (apparently-inert) proton-binding solvent.
Chemical Processing and Properties of Nanocrystalline BaTiO3
Authors: Xu Z. , Chae H. K. , Frey M. H. , Payne D. A.
Published: March 2011

Barium titanate (BaTiO3) thin layers were prepared by sol-gel processing. Details are reported for the synthesis route from methoxyethoxide precursors. Partially hydrolyzed solutions were spin-cast onto metallized silicon substrates, and a multilayering technique was used to develop sub-micron structures. Information is reported on the thermal processing conditions used and the development of structure. Crystallization started at 600°C and was fully developed by 700°C. The room temperature structure was cubic, and the grain size was 25–50 nm. Details are reported for the dielectric properties. Ferroelectricity was not observed. Dielectric constant (200–300) increased with increasing grain size, and was stable with respect to temperature, field and frequency. The properties are attractive for potential integrated capacitor applications.
Microstructural Variations in Sol-Gel Processed Lithium Niobate thin Films
Authors: Joshi Vikram , Goo Grace K. , Mecartney Martha L.
Published: March 2011

LiNbO3 thin films were deposited by dip coating Li-Nb alkoxide solutions onto silicate glass substrates and single crystal sapphire substrates. Microstructural characterization using transmission electron microscopy (TEM) showed significant differences in film microstructures dependent on the initial solution chemistry. Fully crystalline films could be obtained after heat treatments at 400°C in air. The grain size and porosity were dependent on the amount of water of hydrolysis in the alkoxide sol. The higher the water content, the larger the grain size and porosity. Crystallization studies of nucleation and growth of LiNbO3 for films heat treated from 300–600°C indicated that higher temperatures or long soak times generated large facetted grain structures. Single crystalline films were obtained on (0001) sapphire substrates.
The Growth of Single Crystal-Like and Polycrystal KNbO3 Films Via Sol-Gel Process
Authors: Cheng Chih-Hsing , Xu Yuhuan , Mackenzie John D. , Zhang Jie , Eyring LeRoy
Published: March 2011

Transparent and uniform thin films of crystalline KNbO3 were synthesized on different substrates such as SrTiO3, ZrO2, MgO and Pt by the dip-coating method using a double alkoxides solution. The film was epitaxially crystallized at the temperature around 750°C for 3 hours in air on SrTiO3 single crystal substrate. The structure of the films has been studied with X-ray and electron diffraction, and transmission electron microscopy.

Different molar ratios of 2-ethylhexanoic acid (2EHA) to alkoxides were applied to control the hydrolysis rate of the sol-gel solution. Dense films were obtained after modification of the alkoxides solution.
Synthesis of Cuprate Based High-Tc Superconductors by Polymerized Complex Method
Authors: Kakihana Masato , Yoshimura Masahiro , Mazaki Hiromasa , Yasuoka Hiroshi , BöRj Esson Lars
Published: March 2011

We report on a novel precursor technique to produce highly pure and homogeneous cuprate based high-Tc superconductors based on the formation of a polymer metal complex in which various metal ions in desired stoichiometric ratio can be uniformly dispersed. Application of the polymerized complex method is demonstrated on the ceramic synthesis of polycrystalline compounds viz. YBa2Cu3Oy, YBa2Cu4Oy, Bi1.6Pb0.4Sr2Ca2Cu3Oy and Bi2Sr2Ca0.8Cu2Oy. The superconducting properties were studied with complex magnetic susceptibility measurements which exhibited sharp superconducting transitions without any indication of two-phase character. The materials fabricated by this method showed improved properties compared to those for ceramic samples of previously reported synthesis procedures.
Corrosion Resistant ZrO2 Sol-Gel Coating on Stainless Steel
Authors: Atik M. , Aegerter M. A.
Published: March 2011

Corrosion resistant Sol-Gel ZrO2, coatings deposited by dip coating technique on 316 L stainless steel sheets have been fabricated utilizing sonocatalysed precursors sols prepared from zirconium alkoxide Zr(OC3H7)4, isopropanol, glacial acetic acid and water. Their composition varied between 0,025 to 0,9 mol/1 ZrO2. The coatings have been characterized by X-ray diffraction, IR optical reflection, ellipsometry and scanning electron microscopy. When densified under a slow heat treatment thin coatings exhibit outstanding corrosion resistance as no weight change has been observed after 24 h chemical attack in H2SO4 aqueous solution at 81°C and 10 h oxidation treatment in air at 800°C. Thick films as well as films densified under rapid heat treatments tend to crack and are less corrosion resistant.
The Effect of Gel Aging on the Physical and Optical Properties of a Gel-Derived Grin Glass
Authors: Banash Mark A. , Che Tessie M. , Brian Caldwell J. , Mininni Robert M. , Soskey Paul R. , Warden Victor N. , Chin Hui H.
Published: March 2011

Variations in gel aging times and temperatures are shown to affect the optical properties of a gel-derived GRIN lens. These properties include the variation of the total index change as well as the shape of the index profile. However, these optical properties do not appear to correlate with the amount of modifier removed during the leaching step. Also, regardless of aging, gels appear identical with respect to calcining response and composition of pore liquid.
Pore Size and Surface Texture Modification of Silica Via Trialkylsilylation
Authors: Hua Duen-Wu , Smith Douglas M.
Published: March 2011

Surface modification of silica via silylation is often undertaken to change surface chemistry and hence, adsorption characteristics but little attention is paid to its use for pore morphology modification, the subject of this work. Modification of two silica samples was conducted by trimethylsilylation. The degree of silylation/ surface coverage was monitored by TGA and elemental analysis. Pore structure was studied by nitrogen adsorption and condensation, and small angle x-ray scattering (SAXS). Previously, we demonstrated that surface area, surface texture, pore size distribution, and total pore volume are indeed changed in a controlled fashion due to silylation of mesoporous silicas. Generally, the mean pore size is smaller, the pore size distribution is narrower, and the pore surface is smoother after silylation. However, questions remain concerning the effect of small-scale surface roughness and the fractional surface coverage on the effective pore size. This study concentrates on the silylation of smaller pore material (r < 40 Å). Significant pore size distribution narrowing and smoothing of the pore surface with increasing surface coverage was noted.
Polynuclear Titanium Oxoalkoxides: Molecular Building Blocks for New Materials?
Authors: Chen Y. W. , Klemperer W. G. , Park C. W.
Published: March 2011

The [Ti7O4](OEt)20 molecule, Et = C2H5, is very reactive toward ethanol, and its [Ti7O4] metal oxide core structure is largely decomposed in <10 minutes. The [Ti16O16](OEt232 molecule, however, has a [Ti16O16] core structure which is relatively stable toward alcoholysis, and solid state 17O MAS NMR experiments using selective 17O labeling techniques show that this core structure is preserved in good yield during sol-gel polymerization.
Preparation and Physical Properties of V2 O5 Aerogels
Authors: Hirashima Hiroshi , Sudoh Kazumi
Published: March 2011

Monolithic aerogels and aerogel coatings of hydrated V2O5 containing 0 to 10 mol% GeO2 were prepared from metal alkoxides by hydrolysis and autoclave drying. The bulk aerogels of high porosity, more than 90 %, were obtained. On the other hand, the porosity of the aerogel coatings, about 50 nm in thickness, was about 50 %. The aerogels consisted of micro fibrils, less than 20 nm in diameter. Diffraction peaks of crystalline vanadium oxides were not observed for the as-dried aerogels. Dynamic microhardness of the bulk aerogels was very low, but increased with addition of GeO2· Dc electrical conductivity of the bulk aerogels was lower than that of the bulk xerogels by one order of magnitude, and was isotropie. The aerogels were surface fractal with Ds ≅ 2.7.
Macro-Defect-Free Cement: A Novel Organoceramic Composite
Authors: Francis Young J. , Berg M.
Published: March 2011

Macro-defect-free cement is a composite material made by processing a hydraulic cement with a water-soluble polymer under high shear roll-milling. This paper examines the principles of processing and the development of microstructure that results in a material with ceramic-like properties. The nature of the chemical interaction between the cement and the polymer is also considered in some detail.
Formation of Highly Dispersed Metals on Functionalized Silica Supports
Authors: Rousseau Francois , Duan Z. , Hampden-Smtth M. J. , Datye A.
Published: March 2011

The hydrolysis of H2N(CH2)2NH(CH2)3Si(oMe)3 with a stoichiometric amount of water results in loss of the -OMe groups after two days and formation of a mixture of species mainly with empirical formula, [H2N(CH2)2NH(CH2)3Si(O)3]. The reaction of representative examples of metal salts, e.g. Cu(NO1.5)2, and metal-organic compounds, [(NBD)RhCl]2, with the amino-group of the amine functionalized polysiloxanes [H2N(CH2)2NH(CH2)3Si(O)1.5] has been demonstrated. These species undergo thermal decomposition in air, typically at 200°C, with complete loss of the organic supporting ligands. On heating to 450°C in O2, sintering occurs to form large, ∼1μm, sized silica particles which contain highly dispersed, ∼4nm sized metal-containing particles. The surface areas range from 228 to 583 m2/g. After reduction, the rhodium species is active towards catalytic hydrogenation of pyrene.
Energy Transfer Between Eu2+, Eu3+ and Rh6G in Silica, Zirconia and Alumina Gels
Authors: Nie W. , Dunn B. , Sanchez B. , Griesmar P.
Published: March 2011

The sol-gel process provides new opportunities for the synthesis of photonic materials. Sol-gel chemistry is mainly based on inorganic polymerization reactions performed in solution at lower temperatures than conventional chemical methods. Homogeneous doping by mixing components at a molecular level and synthesis of mixed organic-inorganic materials can then be performed. Luminescent properties of dyes inside silica, aluminosilicates or transition metal oxide based gels have been studied extensively. Much less work has been devoted to the study of energy transfer (ET) inside sol-gel matrices. Sol-gel materials provide the opportunity to investigate dye-dye ET, as well as dye-ion ET. This communication presents an optical study of a variety of sol-gel matrices (SiO2, Al2O3, ZrO2 based gels) codoped with rhodamine 6G(Rh6G) and europium. Different types of ET are observed among Rh6G, Eu3+ and Eu2+. The Eu2+/Eu3+ ratio is found to be strongly dependent on the host matrices. The reduction of Eu3+ t· Eu2+ in dried gels may relate to the presence of Rh6G.
Dense Xerogel Matrices and Films for Optical Memory
Authors: Chaput F. , Boilot J. P. , Devreux F. , Canva M. , Georges P. , Brun A.
Published: March 2011

Optically clear gels doped with organic molecules are prepared in the zirconia-silica system by hydrolysis of metal alkoxides in a wet atmosphere. After drying, dense xerogels are obtained which exhibit a closed porosity. By using the same route, organic-inorganic hybrid xerogels are also produced as films.

The molecule-matrix interactions are evaluated from the absorption recovery times of the S0→S1 transition for triphenylmethane dyes. Concerning doped xerogels with other organic molecules having polar groups, the application of the strong polarized electric field of an ultrashort optical pulse allows to locally create a birefringence with a memory effect. This type of sample could be used for optical storage and treatment of information.
Polymer-Derived Silicon Carbide Fibers with Improved Thermomechanical Stability
Authors: Toreki W. , Batich C. D. , Sacks M. D. , Saleem M. , Choi G. J.
Published: March 2011

Continuous silicon carbide fibers (”UF fibers”) with low oxygen content (∼2 wt%) were prepared by dry spinning of high molecular weight polycarbosilane solutions and subsequent pyrolysis of the polymer fibers. Room temperature mechanical properties were similar to those of commercially-available Nicalon™ fibers, as average tensile strengths as high as 3 GPa were obtained for some batches with fiber diameters in the range ∼10–15 μm Furthermore, UF fibers showed significantly better thermomechanical stability compared to Nicalon™, as indicated by lower weight losses, lower specific surface areas, and improved strength retention after heat treatment at temperatures up to 1700°C. UF fibers were also characterized by elemental analysis, X-ray diffraction, and scanning Auger microprobe. Strategies were suggested for achieving further improvements in thermomechanical stability.
Syntheses, Structures and Properties of Polycarbosilanes Formed Directly by Polymerization of Alkenylsilanes
Authors: Masnovi John , Bu Xin Y. , Beyene Kassahun , Heimann Paula , Kacik Terrence , Harry Andrist A. , Hurwitz Frances I.
Published: March 2011

Vinylsilane polymerizes to form predominantly a carbosilane polymer using dimethyltitanocene catalyst. This is in contrast to alkylsilanes, which afford polysilanes under the same conditions. The mechanism of polymerization of alkenylsilanes has been shown to be fundamentally different from that for the polymerization of alkylsilanes. The silyl substituent apparently activates a double bond to participate in a number of polymerization processes in this system, particularly hydrosilation. Isotopie labeling indicates the involvement of silametallocyclic intermediates, accompanied by extensive nuclear rearrangement. Polymers and copolymers derived from alkenylsilanes have relatively high char yields even for conditions which afford low molecular weight distributions. Formation of crystalline β-SiC is optimum for a copolymer of an alkylsilane and an alkenylsilane having a silane/carbosilane backbone ratio of 85/15 and a C/Si ratio of 1.3/1.
Silicon Oxycarbide Glasses from Sol-Gel Precursors
Authors: Babonneau F. , Soraru G. D. , D'Andrea G. , Dire S. , Bois L.
Published: March 2011

Silicon oxycarbide glasses have been prepared from sol-gel precursors containing not only Si-CH3, but also Si-H bonds. Three systems have been chosen containing various Si units but the same C/Si ratio. Their pyrolysis process has been mainly followed by 29Si MAS-NMR and the composition of the final glass extracted. This study shows that a suitable choice of Si-CH3 and Si-H functionnalized silicon alkoxides can lead to a strong decrease in the free carbon content and to an almost pure silicon oxycarbide phase.
Characterization of High Surface Area Silicon Oxynitrides
Authors: Lednor Peter W. , Ruiter Rene De , Emeis Kees A.
Published: March 2011

High surface area silicon oxynitrides have been prepared by nitrida- tion of silica with ammonia. Characterization by Fourier-transform infrared spectroscopy has allowed quantitative determination of hydroxyl, amido and imido groups. Data obtained by X-ray photoelectron spectroscopy show that the nitrogen is well distributed in the surface of the materials.
Electronic Properties of OMVPE Grown films of YBa2Cu3O7-δ on 1” LaAlO3 Substrates
Authors: Rees William S. , Hascicek Yusuf S. , Testardi Louis R.
Published: March 2011

Films of YBa2CU3O7-δ have been grown on 1” LaAlO3 by OMVPE utilizing M(tmhd)n (M = Ba, Cu: n = 2; M = Y: n = 3; tmhd = 2,2,6,6-tetramethylheptane-3,5-dionato) as the source materials in a cold wall, vertical rotating disk reactor. The resultant films were characterized by SEM, XRD, Tc, Jc, and surface profilometry measurements. Relative to laser ablated thin films, the surface morphology was determined to be virtually featureless. In-situ depositions at substrate temperatures of <700°C, employing nitrous oxide as the oxidizing reagent, produced annular irregularities in the electronic properties of these films. The highest quality was observed near the film's center, with a marked decay evident toward the exterior 7 mm perimeter of the coated wafer.
Omcvd Elaboration and Characterization of Silicon Carbide and Carbon-Silicon Carbide Films from Organosilicon Compounds
Authors: Morancho R. , Reynes A. , Amjoud M'b. , Carles R.
Published: March 2011

Two organosilicon molecules tetraethysilane (TESi) and tetravinylsilane (TVSi) were used to prepare thin films of silicon carbide by chemical vapor deposition (C. V. D.). In each of the molecule, the ratio C/Si = 8, the only difference between TESi and TVSi is the structure of the radicals ethyl (.CH2-CH3) and vinyl (.CH=CH2). This feature induces different thermal behavior and leads to the formation of different materials depending on the nature of the carrier gas He or H2· The decomposition gases are correlated with the material deposited which is investigated by I.R. and Raman spectroscopy. The structure of the starting molecule influences the mechanisms of decomposition and consequently the structure of the material obtained.
Deposition of Ceramic Films by A Novel Pulsed-Gas Mocvd Technique
Authors: Aitchison Kenneth A. , Barrie James D. , Ciofalo Joseph
Published: March 2011

Metal-Organic Chemical Vapor Deposition (MOCVD) is a versatile technique for the deposition of thin films of metals, semiconductors and ceramics. Commonly used hot wall flow-reactor designs suffer from a number of limitations. Chemical processes occurring in these reactors typically include a combination of homogeneous (gas-phase) and heterogeneous (gas-surface) reactions. These complex conditions are difficult to model and are poorly understood. In addition, flow reactors use large quantities of expensive precursor materials and are not well suited to the formation of abrupt interfaces. We report here a novel MOCVD technique which addresses these problems and enables a more thorough mechanistic understanding of the heterogeneous decomposition pathways of metal-organic compounds. This technique, the low-pressure pulsed gas method, has been demonstrated to provide high deposition rates with excellent control over film thickness. The deposition conditions effectively eliminate homogeneous processes allowing surface-mediated reactions to dominate. This decoupling of gas-phase chemistry from film deposition allows a better understanding of reaction mechanisms and provides better control over film growth. Both single metal oxides and binary oxide systems have been investigated on a variety of substrate materials. Effects of precursor chemistry, substrate surface, temperature and pressure on film composition and morphology will be discussed.
Synthesis and Properties of Molecular Fragments of Metal Chalcogenides
Authors: Steigerwald Michael L.
Published: March 2011

In this manuscript we describe several approaches to the preparation of molecule-sized fragments of inorganic solids. The first is the arrested precipitation of metal selenides in reverse micelles; the second is the arrested pyrolysis of molecular precursors to II–VI compounds; and the third is the chemical moderation of molecules-to-solids reactions.
Clusters of Electron Rich Transition Metal Elements
Authors: Fenske Dieter
Published: March 2011

In the widest sense, a cluster is an aggregate of molecules or atoms. Many clusters contain metal atom groups Mn in which the metals are chemically bonded to each other. To decide whether metal-metal bonds are present, the comparison with bonding in pure metals is often made.
Analysis of Collective Resonances in Clusters: Metals and Carbon
Authors: Kresin Vitaly V.
Published: March 2011

Dipole photoabsorption spectra of small clusters are analyzed. Two types of systems are considered: metal clusters and the carbon fullerenes. Both have been found to exhibit strong collective photoabsorption modes associated with the motion of delocalized electrons. We describe analytical results for the resonance frequencies in both spherical (closed-shell metallic, C60 ) and spheroidal (openshell metallic, C70) particles. The calculation is based on the techniques of many-body physics (random-phase approximation, sum rules), affords a unified view of the dynamical response of microscopic clusters, and leads to good agreement with experimental data.