bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrometallurgical Application of a Novel Porous Resin
Authors: Unger Peter D. , Rohrbach Ronald P.
Published: March 2011

The technology to manufacture rigid, highly porous materials of very low density that are suitable for use in a wide range of industrial applications has recently been developed in this laboratory. These materials, derived from naturally occurring polymers, have many useful physical characteristics including very large pore volume, pore size distribution in a useful range, and high surface area. These characteristicsw, hen combinedw ith their robust mechanicals trength, make them potentially useful as support matrices for various complexing agents. One demonstrated application of this material is as a polymeric carrierfo r selective liquid metal extractants in hydrometallurgicalp rocesses. We have successfully impregnated our porous matrix with several selective metal extractants, and demonstrated retention of the basic metal binding properties of the immobilized agent. Results of bench scale pilot studies using a copper selective impregnated resin indicate excellent capacity, and good selectivity and extraction/elution kinetics.
Direct Colorimetric Detection of Virus by a Polymerized Bilayer Assembly
Authors: Charych Deborah H. , Nagy Jon O. , Spevak Wayne , Ager Joel , Bednarski Mark D.
Published: March 2011

Screening and detecting virus by receptor-ligand interactions presents an important challenge in medical and environmental diagnostics, and in drug development. We have developed a direct colorimetric detection method based on a polymeric bilayer assembly. The bilayer is composed of a self-assembled monolayer of octadecyl siloxane and a Langmuir-Blodgett layer of polydiacetylene. The polydiacetylene layer is functionalized with receptor-specific ligands such as analogs of sialic acid. The ligand serves as a molecular recognition element, while the conjugated polymer backbone signals binding at the surface by a chromatic transition. The color transition is readily visible to the naked eye as a blue to red color change and can be quantified by visible absorption spectroscopy. The color transition can be inhibited by the presence of soluble inhibitors. Raman spectroscopic analysis shows that the color transition may arise from binding induced strain on the material resulting in bond elongation and conjugation length reduction.
Nephila Clavipes Dragline Silk: Approaches to a Recombinantly Produced Silk Protein
Authors: Mello Charlene M. , Arcidiacono Steven , Beckwitt Richard , Prince John , Senecal Kris , Kaplan David L.
Published: March 2011

Spider silks exhibit an unusual combination of strength and toughness that distinguishes them from other natural and synthetic fibers. Silk proteins perform a key natural function as structural fibers, to absorb impact energy from flying insects without breaking. They dissipate energy over a broad area and balance stiffness, strength and extensibility (1,2). In addition to their unusual mechanical properties and visual lustre, silks also exhibit interesting interference patterns within the electromagnetic spectrum (3), unusual viscometric patterns related to processing (4), and piezoelectric properties (3,5,6). These properties suggest they would be good candidates for high performance fiber and composite applications. However, the spider is not capable of producing sufficient quantities of proteins to enable thorough evaluation of their potential. Consequently, we are pursuing recombinant DNA techniques to clone and express adequate quantities of recombinant spider silk for these studies.
Chemical Synthesis of Nanostructures
Authors: Stoddart J. Fraser , Amabilino David B.
Published: March 2011

Molecular recognition is central to the self-assembly of catenanes and rotaxanes. The design criteria for efficient formation of these compounds is gradually becoming clear. Selfassembly of mechanically-interlocked compounds is heading apace towards the nanometre scale.
Cell Function on Substrates Containing Immobilized Bioactive Peptides
Authors: Dee Kay C , Andersen Thomas T. , Bizios R.
Published: March 2011

Adhesion, proliferation and motility of bovine pulmonary artery endothelial cells and of rat calvarial osteoblasts were examinedin vitroand on glass surfaces modified with immobilized bioactive peptides. The peptides Arginine-Glycine-Aspartic Acid-Serine (RGDS), Arginine-Aspartic Acid-Glycine-Serine (RDGS), and Tyrosine-Isoleucine-Glycine-Serine-Arginine-Glycine (YIGSRG) were covalently bound to aminophase glass. The results of this study showed that modification of the substrate surface with immobilized peptides affected each cell line in different ways. Incorporation of this knowledge in the design of implant materials could result in biomaterials which promote and/or sustain a number of desirable cellular functions at the tissue-implant interface.
Osteoblast Adhesion on Biodegradable Polymer Substrates
Authors: Ishaug Susan L. , Yaszemski Michael J. , Bizios Rena , Mikos Antonios G.
Published: March 2011

We have investigated the adhesion of rat osteoblasts on biodegradable poly(α-hydroxy ester) films as an in vitro model of bone regeneration. Osteoblasts cultured on poly(L-lactic acid), poly(DL-lactic-co-glycolic acid) copolymers, and poly(glycolic acid) films for 14 days grew with rates comparable to those observed for tissue culture polystyrene and retained their phenotype as expressed by activity of alkaline phosphatase and collagen synthesis.
The Development of an In Situ Assay for bFGF Release
Authors: Hobbs S. K. , Periolat L. M. , Cima L. G. , Nugent M. , Leunig M. , Jain R. K.
Published: March 2011

There is a need for an in situ assay to quantify tissue reactivity to sustained release of bFGF to better understand and control growth factor-induced angiogenesis. To this end we have adapted the alginate/heparin-sepharose release system for use in the mouse dorsal skinfold chamber. A mathematical model was used to predict the time dependence of bFGF release as a function of bFGF loading, heparin concentration, and device geometry. The model predictions agreed well with previously reported in vitro data. In vivo studies to correlate blood vessel growth as a function of release rate are in progress.
Development of a Collagen-Gag Copolymer Implant for the Study of Tendon Regeneration
Authors: Louie L. K. , Yannas I. V. , Spector M.
Published: March 2011

Following injuries resulting in a gap, tendons generally do not heal sufficiently because the defect does not fill with reparative tissue, or the resulting scar tissue is not functionally adequate. The objective of this study was to engineer a collagen-GAG (CG) copolymer to facilitate tendon regeneration. Previous work in our laboratory using similar porous resorbable analogs of extracellular matrix have led to regeneration of skin and peripheral nerve.

Matrices with controlled pore structure were produced by adapting the manufacturing technique developed in our laboratory for grafts with cylindrical geometry. CG suspensions contained within silicone elastomer tubes were frozen and lyophilized in a controlled manner. Quantitative optical microscopy was used to determine the percent porosity, average pore size, and pore orientation of the matrices.

The CG matrices, formed in silicone elastomer tubes, 3.8 mm in diameter, had average pore sizes ranging from 20 to 150 μm. his range of pore sizes was comparable to that obtained previously using a diameter of 1.5 mm.1The average pore size did not appear to be strongly dependent on the tubing diameter. The homogeneity of the pore structure and the pore channel orientation could be controlled by adjusting the temperature of the bath used for freezing the CG suspension and the velocity with which the graft was immersed into the coolant bath.
Temperature- and pH- Sensitive Hydrogels for Controlled Release of Antithrombotic Agents
Authors: Brazel Christopher S. , Peppas Nicholas A.
Published: March 2011

Polymeric hydrogels capable of reversible swelling with changes in environmental temperature and pH were synthesized and studied as matrix systems capable of controlled release of antithrombotic drugs to the site of a blood clot. Monomers N-isopropylacrylamide (NIPAAm) and methacrylic acid (MAA) were chosen for the temperature- and pHdependent swelling characteristics of their polymers, respectively. Equilibrium swelling studies were performed as functions of pH and of temperature, and kinetic swelling studies were performed on the thermally responsive gels as a function of time after the gel was subjected to a step-change in temperature. Experimental results indicate that P(NIPAAmco- MAA) hydrogels can be synthesized so that they are either pH- or temperaturesensitive, depending upon the composition of the network. The pure PNIPAAm gels showed a lower critical solubility temperature (LCST) of around 32°C, below which the gel was in its swollen state, and above which the gel collapsed. As the amount of methacrylic acid in the gels was increased, the degree of swelling in deionized water decreased and the temperature sensitivity was lost. The hydrogels containing MAA displayed a transition in swelling behavior between pH 4 and 6. The mesh sizes of the hydrogel networks were calculated from the results of the swelling studies by Flory-Rehner theory. A kinetic experiment on the temperature-sensitive pure PNIPAAm hydrogel showed that the polymer network collapsed rapidly upon temperature changes across the LCST.
The Impact of Formulated Interleukin-2 / Delivery Device Surface Interactions on Bioefficacy
Authors: Tzannis Stelios T. , Przybycien Todd M. , Hrushesky William J. M. , Wood Patricia
Published: March 2011

The interactions between a therapeutic protein and the surfaces of a delivery device may play a pivotal role in the efficacy of a recombinant protein-based biologic therapy program. Protein adsorption may induce conformational changes and aggregation, resulting in the inactivation of the protein of interest and even malfunction of the delivery device itself. We studied the interactions of formulated interleukin-2 (IL-2) with the surfaces of a commonly used pump-based delivery system at 37°C over a 24-hour period. Delivered protein concentration and bioactivity assays were performed at intervals in order to quantitate the impact of exposure time. Adsorption to the catheter tubing walls resulted in 20 to 30% reduction in the concentration of delivered IL-2 relative to the initial concentration. After 2 hours of operation, delivered IL-2 bioactivity levels fell to -10% of the initial activity levels. These activity losses were accompanied by a significant decrease in the protein's helical content, as monitored by circular dichroism spectroscopy. Attenuated total reflectance Fourier transform infrared spectroscopy indicated that adsorbed IL-2 had non native secondary structure contents. We hypothesize that surface-mediated IL-2 denaturation is responsible for the majority of the observed activity losses
Characterization of a Polyanhydride Series by Ftir
Authors: Kreitz Mark R. , Pekarek Kathleen J. , Mathiowitz Edith
Published: March 2011

Using Fourier-transform infrared (FTIR) spectroscopy we have characterized a polyanhydride copolymer series composed of various ratios of the diacids 1,3-bis(p -carboxyphenoxy)propane (CPP) and sebacic acid (SA). Typical peaks corresponding to the aliphatic-aliphatic (SA-SA), aromatic-aliphatic (CPP-SA), and aromatic-aromatic (CPP-CPP) diads were found in the 1820- 1710 cm−1 wavenumber range. Further peaks corresponding to the SA-SA diads were identified in the fingerprint region at 1382, 1360, 1307, and 1286 cm−1. These peak characterizations facilitate identification of bond distribution in the CPP-SA copolymer as well as other polyanhydride copolymers, and correlate well with previously presented information obtained with nuclear magnetic resonance (NMR) spectroscopy and X-ray powder diffraction.
Use of Porous Bone Mineral to Increase Bone Density
Authors: Boyne Philip J.
Published: March 2011

The amount of bone density in a metal implant recipient site markedly effects the success of the implant and the prosthesis. Therefore mechanisms designed to enhance bone density are necessary. Porous bone mineral (BioOss) was used in this study to demonstrate the ability of this product to be slowly resorbed and remodelled, and to enhance in the remodelling process of the amount of calcified bone matrix available for reception of any subsequent placed prosthesis. Further research on the effect of functional prosthesis on the osseous matrix and the long term effect of function on the increase bone matrix is needed.
The Role of Hepatotrophic Stimulation in Heterotopic Hepatocyte Transplantation
Authors: Kaufmann P.-M. , Uyama S. , Sano K. , Mooney D. , Vacanti J. P.
Published: March 2011

In the future, the development of methods for transplantation of large hepatocyte numbers could provide an alternative to the established liver and split liver transplantation. The use of three dimensional prevascularized polyvinyl alcohol (PVA) scaffolds have allowed hepatocyte transplantation equivalent to a whole liver mass. This study was designed to determine if a portacaval-shunt (PCS) or a 70% hepatectomy (70% HE) enhanced engraftment and proliferation of transplanted hepatocytes in heterotopic locations.

Male Lewis rats served as both donors and recipients, respectively. PVA-sponges were implanted as matrices for the transplanted hepatocytes. Recipient animals were divided into four groups. All groups received transplantation of 5×107 Hepatocytes (HCTx). In addition, group A received 70% HE, group B received a PCS plus 70% HE whereas group D received PCS. Group C as a control, received only HCTx. Quantitative morphometric analysis of hepatocyte area was performed on day 0, 3, 7 and 14 after transplantation. BrdU staining was performed to study DNA-Synthesis in the graft on day 3 and 14.

PCS alone and in combination with a partial hepatectomy led to significantly greater cell area one week after transplantation compared to the partial hepatectomy alone. 70% HE resulted in significantly larger cell area than the controls. At two weeks after transplantation, these significant differences persisted with the exception of Group A and C results which were not significantly different. On day 3, BrdU staining revealed a significantly higher DNA synthesis rate in Groups A and B compared to Group C. On day 14, no statistically significant differences in levels of DNA synthesis could be observed.

We conclude that hepatocytes can be successfully transplanted into PVA-devices. Engraftment and proliferation can be significantly enhanced by using portacaval shunt and partial hepatectomy as hepatotrophic stimulation.
Controlled Drug Delivery to the Joints by Enzymatically Degradable Microspheres
Authors: Brown Kimberly E. , Shao Wen , Bathon Joan , Leong Kam W.
Published: March 2011

An intra-articular polymeric controlled release system was developed that is tailored to, and responsive to, the intensity of joint inflammation. Microspheres composed of the naturally occurring polyelectrolytes, gelatin and chondroitin sulfate, were synthesized by complex coacervation and the kinetics of release of encapsulated 14C-catalase was evaluated in vitro in the presence of inflammatory and non-inflammatory human joint fluids. The relative activity of gelatinase, a metalloprotease enzyme, was quantified in each of the joint fluids. Rate of degradation of the microspheres, and consequent release of 14C-catalase, was found to parallel the relative gelatinase activities in the joint fluids. Furthermore, various methods of crosslinking were found to affect the kinetics of microsphere degradation in the fluids. A catalase loading level of up to 28% was achieved, and the encapsulated catalase was found to retain up to 58 % of its biological activity.
The Erosion Properties of Polyanhydrides
Authors: Shieh Lisa , Göpferich Achim , Langer Robert
Published: March 2011

Bioerodible polymers play an important role in parenteral drug delivery. They combine the advantage of controlling drug release and being absorbed by the body after fulfilling their task. The mechanism which controls drug release is the erosion of polymer bulk. In order to understand and control the release it is, therefore, essential to know the erosion mechanism of a biodegradable polymer. We found that the polyanhydrides obey a distinct erosion pattern. An erosion zone (the region where material loss occurs) moves from the surface to the center of the discs. The monomers of which these copolymers are composed also seem to play an important role in degradation and erosion.
The Decomposition of Methyltrichlorosilane: Studies in A High-Temperature Flow Reactor
Authors: Allendorf Mark D. , Osterheld Thomas H. , Melius Carl F.
Published: March 2011

Experimental measurements of the decomposition of methyltrichlorosilane (MTS), a common silicon carbide precursor, in a high-temperature flow reactor are presented. The results indicate that methane and hydrogen chloride are major products of the decomposition. No chlorinated silane products were observed. Hydrogen carrier gas was found to increase the rate of MTS decomposition. The observations suggest a radical-chain mechanism for the decomposition. The implications for silicon carbide chemical vapor deposition are discussed.
Heterogeneous Kinetics of The Chemical Vapor Deposition of Silicon Carbide From Methyltrichlorosilane
Authors: Papasouliotis George D. , Sotirchos Stratis V.
Published: March 2011

We examine the dynamic behavior of a heterogeneous reaction model for the chemical vapor deposition of carbon, silicon, and silicon carbide from the precursors generated by the thermal decomposition of methyltrichlorosilane (MTS, CH3SiCl3 ). All reactions are treated as reversible in order to account for the strong inhibitory effect of the reaction by–products on the deposition process that was observed in our experiments and in other studies. The equilibrium constants of the adsorption steps of the reactions are treated as model parameters, and those of the other reactions are calculated from the thermodynamic constants of a set of overall deposition reactions. Results are presented on the influence of the various model parameters on the reaction rate, the stoichiometry of the deposit, and the variation of these quantities with the distance in a plug flow deposition reactor.
Effect of Oxygen on Diamond Deposition in CH4/O2/H2 Gas Mixtures
Authors: Matsuyama H. , Sato N. , Kawakami H.
Published: March 2011

Diamond growth experiments were carried out by a microwave plasma assisted CVD technique in various gas mixtures of CH4(0–100%)/02/H2. The phase diagram obtained by this study shows that a diamond growth region exists. With addition of more than 5% O2 in reactant gases, diamond particles could be included in amorphous or graphitic carbon films even using CH4/O2 gas mixtures. Faceted diamond films were obtained if the oxygen gas concentration [O2] was approximately more than half the methane gas concentration [CH4] ([O2]>[CH4]/2). However, no films were grown when [O2] exceeded half of [CH4] plus 7% ([O2]>[CH4]/2+7%). These results corresponded to the observations by plasma emission spectroscopy. Though oxygen etches carbon films and decomposes methane by forming carbon monoxide, oxygen rarely reacts with hydrogen in a film growth region.
Atomic Layer Growth of SiO2 on Si(100) Using the Sequential Deposition of SiCl4 and H2O
Authors: Sneh Ofer , Wise Michael L. , Okada Lynne A. , Ott Andrew W. , George Steven M.
Published: March 2011

This study explored the surface chemistry and the promise of the binary reaction scheme:

(A) Si-OH+SiCl4 → Si-Cl + HCl

(B) Si-Cl + H2O → Si-OH + HCl

for controlled SiO2 film deposition. In this binary ABAB… sequence, each surface reaction may be self-terminating and ABAB… repetitive cycles may produce layer-by-layer controlled deposition. Using this approach, the growth of SiO2 thin films on Si(100) with atomic layer control was achieved at 600 K with pressures in the 1 to 50 Torr range. The experiments were performed in a small high pressure cell situated in a UHV chamber. This design couples CVD conditions for film growth with a UHV environment for surface analysis using laser-induced thermal desorption (LITD), temperature-programmed desorption (TPD) and Auger electron spectroscopy (AES). The controlled layer-by-layer deposition of SiO2 on Si(100) was demonstrated and optimized using these techniques. A stoichiometric and chlorine-free SiO2 film was also produced as revealed by TPD and AES analysis. SiO2 growth rates of approximately 1 ML of oxygen per AB cycle were obtained at 600 K. These studies demonstrate the methodology of using the combined UHV/high pressure experimental apparatus for optimizing a binary reaction CVD process.
Properties of A New Liquid Organo Gold Compound for MOCVD
Authors: Uchida Hiroto , Saitou Norimichi , Satou Masamitu , Tebakari Masayuki , Ogi Katsumi
Published: March 2011

Dimethyl(1,1,1,5,5,5-hexafluoroaminopenten-2-onato)Au(III), DMAu(hfap) was found to be very promising compound for CVD Au wiring. It is liquid at r.t. and has high vapor pressure (0.5 Torr at r.t.) and high thermal stability (dec.t. 171°C, δE=25.4Kcal/mol) and can be used as a precursor for MOCVD. CVD gold films were grown on Si(100) from DMAu(hfap) in a quartz vacuum chamber, using thermal activation by an electric heater or photo activation through quartz windows by excimer lasers(XeC1 308nm). A growth rate of 10 nm/min was achieved by thermal activation at 250 °C, (evaporation temperature of 30 °C, H2 flow rate at 100 sccm and chamber pressure of 30 Torr). Resistivities ranged between 2.8 and 5.lμΩ-cm, depending on the film morphology. The growth rate of laser CVD gold films had the tendency of increasing with decreasing the substrate temperature. This phenomenon indicates that photolysis of adsorbed species on the substrate plays an important role in film growth by laser CVD.
Infrared Studies of Ozone-Organosilicon Chemistries for SiO2 Deposition
Authors: Mucha J. A. , Washington J.
Published: March 2011

Gas-phase Fourier transform infrared spectroscopy has been used to monitor reactants and products in the study of O3 decomposition and the reaction of O3 with tetramethylsilane and tetraethoxysilane. The results confirm the interpretation that O3 decomposition is heterogeneous, and a dominant factor in SiO2 deposition using these chemistries. Product analysis shows that the higher reactivity of TEOS with O3 is probably due to the ability of TEOS to undergo α-hydride elimination of one ethoxy group, per molecule, and one oxidative acetic acid elimination, per molecule, during the deposition process. Results also suggest elimination via the Sicenter involving a single ethoxy group rather than via a 6-center elimination involving two ethoxy groups.
Spectroscopic Investigations of Laser Ablated Germanium Oxide
Authors: Wolf Paul J. , Patterson Brian M. , Witanachchi Sarath
Published: March 2011

Laser produced plumes from a GeO2 target were investigated using both optical emission spectroscopy and laser induced fluorescence. Elemental neutral and ionic Ge and diatomic GeO were monitored as a function of O2 pressure at 4 cm from the target surface. Data obtained from laser fluorescence experiments showed no indication of chemical production of GeO in these plumes under any conditions studied; however, the atomic emission intensities of several ionic and neutral Ge lines appeared to increase with O2 pressure. This signified plume interactions with the background gas. The trends in the species concentrations were determined and the results are interpreted with respect to mechanisms for thin film growth.
Indium Tin Oxide Films Formation by Laser Ablation
Authors: Zheng J.P. , Kwok H.S.
Published: March 2011

The electrical and optical properties of room temperature laser deposited indium tin oxide films were studied. It was found that the resistivity of the film was quite sensitive to the deposition conditions. At the optimized conditions, films with a bulk resistivity value of 2.8×10−4 Ω-cm and optical transmission of greater than 90% could be obtained. By using an in situ resistance measurement, it was shown that the initial growth mode was via island formation. Additionally, a classic transition from two- to three-dimensional behavior for the resistance was observed.
Photochemical Modification of Fluorocarbon Resin Surface to Adhere with Epoxy Resin
Authors: Okoshi M. , Miyokawa T. , Kashiura H. , Murahara M.
Published: March 2011

An epoxy-compatible layer was produced in the near-surface region of a fluorocarbon resin by irradiating with an ArF excimer laser in a gaseous B(CH3)3 or a B(OH)3 water solution atmosphere. The pure photochemical reaction was employed in the modification process, the defluorination of the surface was performed with boron atoms which were photo-dissociated from B(CH3)3 or B(OH)3. The CH3 or OH radicals, also photo-dissociated, replaced the fluorine atoms of the surface. As a result, chemical bonding of the surface with the epoxy was performed. The adhesive strength was evaluated by the shearing tensile test, and the epoxy break value of 130 kgf/cm2 was sucessfully achieved.
The Influence of Temperature Gradients on Partial Pressures in a Cvd Reactor
Authors: Oosterlaken T.G.M. , Leusink G.J. , Janssen G.C.A.M. , Radelaar S. , Kuijlaars K.J. , Kleijn C.R. , Van Den Akker H.E.A.
Published: March 2011

The influence of temperature gradients on the partial pressures of a binary mixture in a cold wall low pressure chemical vapor deposition reactor was determined by Raman spectroscopy of the gaseous species in the reactor. It is demonstrated for the first time that the partial pressure of the heavy constituent in the hot region of a low pressure reactor is reduced by 35 % due to the Soret effect. Model calculations that included the Soret effect are in agreement with the experimental data.
Perfect selective Si epitaxial growth realized by synchrotron radiation irradiation during disilane molecular beam epitaxy
Authors: Utsumi Yuichi , Akazawa Housei , Nagase Masao
Published: March 2011

Perfect selectivity in Si epitaxial growth on a Si/SiO2 substrate has been achieved by irradiating SR during molecular beam epitaxy (MBE) using disilane. This differs from conventional selective growth by MBE using disilane in that no Si nucleation occurs on SiO2 irrespective of growth time. Temperature above 700°C is necessary for SR -induced selective growth. This perfect selectivity might result from the elimination of adsorbed Si atoms induced by photo-stimulated evaporation of SiO2 which results in the perfect suppression of Si nucleation.
Gate Quality Oxides Prepared by Rapid Thermal Chemical Vapor Deposition
Authors: Kuehn R.T. , Xu X. , Holcombe D.J. , Misra V. , Wortman J.J. , Hauser J.R. , Wang Q.-F. , Maher D.M.
Published: March 2011

As the feature size of MOSFET devices shrink, issues such as thermal budget associated with controlling channel doping profiles and oxide growth kinetics raise concerns about using thermally grown furnace oxides for deep-submicron device applications. To address these concerns, we have developed a new RTCVD oxide process using a gas system of silane and nitrous oxide. The RTCVD oxides are deposited in a lamp-heated, cold wall, RTP system. Deposition rates ranging from 55 Å/min. to 624 Å/min. can be achieved at 800°C with silane nitrous oxide flow rate ratio of 2% and total pressure ranging from 3 to 10 Torr. The results indicate that this RTCVD process can be used to deposit both thin gate and thick isolation insulators for single wafer processing. Deposition rates of the RTCVD oxides exhibit a nonlinear dependence on the total deposition pressure. Electrical characterization of the as-deposited RTCVD oxides shows a mid-gap interface trap density of < 5×1010 eV−1 cm−2 and an average breakdown field of 13MV/cm. AES, RBS and TEM analyses have been used to study surface cleaning effects on the silicon-silicon dioxide interface quality and to determine the chemical composition of the RTCVD oxides. The results show that RTCVD oxides with stoichiometric composition and atomic flat silicon-silicon dioxide interface can be achieved using silane nitrous oxide flow rate ratio of <2%. I-V characteristics and transconductance degradation under hot carrier stress for MOSFET's using as-deposited RTCVD gate oxides have been found to be comparable to those of MOSFET's using thermal gate oxides.
Surface Chemistry of Boron-Doped SiO2 CVD: Enhanced Uptake of Tetraethyl Orthosilicate by Hydroxyl Groups Bonded to Boron
Authors: Bartram Michael E. , Moffat Harry K.
Published: March 2011

Insight into how dopants can enhance deposition rates has been obtained by comparing the reactivities of tetraethyl orthosilicate (TEOS, Si(OCH2CH3)4) with silanol and boranol groups on SiO2. This comparison has direct relevance for boron-doped SiO2 film growth from TEOS and trimethyl borate (TMB, B(OCH3)3) sources since boranols and silanols are expected to be present on the surface during the thermal chemical vapor deposition (CVD) process. A silica substrate having coadsorbed deuterated silanols (SiOD) and boranols (BOD) was reacted with TEOS in a cold-wall reactor in the mTorr pressure regime at 1000K. The reactions were followed with Fourier transform infrared spectroscopy. The use of deuterated hydroxyls allowed the consumption of hydroxyls by TEOS chemisorption to be distinguished from the concurrent formation of SiOH and BOH that results from TEOS decomposition at this temperature. It was found that TEOS reacts with BOD at twice the rate observed for SiOD, given equivalent concentrations of BOD and SiOD. This demonstrates that hydroxyl groups bonded to boron increase the rate of TEOS chemisorption. In contrast, additional results show that surface ethoxy groups produced by the chemisorption of TEOS decompose at a slower rate in the presence of TMB decomposition products. Possible dependencies on reactor geometries and other deposition conditions may determine which of these two competing effects will control deposition rates. This has significant implications for microelectronics fabrication since the specific dependencies would be expected to affect process reliability. In addition, this may explain (in part) why the rate enhancement effect is not always observed in boron-doped SiO2 CVD processes.
Hydrogen Pairing on Si(100)-(2×1): A Site-Blocking Study
Authors: Widdra Wolf , Weinberg W. Henry
Published: March 2011

The thermal desorption of hydrogen from a Si(100)-(2×l) monohydride surface has been reported previously to follow first-order kinetics. Pairing of hydrogen atoms on a Si-Si dimer prior to desorption is most likely the cause of this unusual behavior. To examine the degree of hydrogen pairing at various surface temperatures, this study examines the blocking of adsorption sites by hydrogen for subsequent acetylene adsorption. Temperature programmed desorption and Auger electron spectroscopy were used to measure the absolute saturation coverage of acetylene for various coverages of preadsorbed atomic deuterium. The observed linear decrease in saturation coverage of acetylene with deuterium coverage, for atomic deuterium adsorption between 550 and 150 K, indicates that deuterium is paired on Si-Si dimers. The observation that pairing occurs even at 150 K suggests that the diffusion of chemisorbed hydrogen is not responsible for pairing.
Growth of Silicon Films Onto Fluororesin Surface by ArF Excimer Laser
Authors: Miyokawa T. , Okoshi M. , Toyoda K. , Murahara M.
Published: March 2011

Silicon films were deposited on a fluororesin surface. The process was divided into two steps: surface modification process and silicon CVD onto the modified parts. In the modification process, SiH4 and B(CH3)3 mixed gases were used with ArF excimer laser. Fluorine atoms of the surface were pulled out by boron atoms which were photo—dissociated from B(CH3)3 and were replaced with silicon atoms released from SiH4. In the CVD process, SiH4 gas was used with high—density excited ArF excimer laser. Silicon films were deposited onto the nuclei by photodecomposition of SiH4.

Chemical compositions of the modified layers and the deposited parts were inspected by XPS analysis. 1000 Å thickness of the deposited silicon films was confirmed by the surface roughness interference–meter.
Effect of Post Exposed Hydrogen on Chemisorbed Ethylene on Si(100)-(2×l)
Authors: Widdra Wolf , Huang Chen , Weinberg W. Henry
Published: March 2011

The effect of post adsorbed atomic hydrogen on the adsorption, desorption, and decomposition of ethylene on Si(100)-(2×l) has been studied using high-resolution electron energy loss spectroscopy (HREELS), temperature programmed desorption (TPD), and low-energy electron diffraction (LEED). Exposures to atomic hydrogen of more than 1015 atoms/cm2 convert the initial (2×l) reconstruction of sp3-hybridized, di-σ bonded ethylene to a (l×l) structure. Furthermore, after post exposure to atomic hydrogen, the thermal desorption peak of molecular ethylene is shifted up by approximately 100 K and reduced in intensity. HREEL spectra for deuterated ethylene show the formation of a C-H bond after exposure to atomic hydrogen, whereas the C-C bond remains intact. We explain our data by an atomic hydrogen-driven conversion of the di-σ bonded ethylene to a mono-σ bonded surface ethyl. Thermal activation after post exposure to atomic hydrogen leads to decomposition of about 60% of the initial ethylene in contrast to the observed molecular desorption in the absence of hydrogen.
Deposition and Properties of AlN Films Prepared by Low Pressure CVD with a Metalorganic Precursor
Authors: Cook M. J. , Wu P. K. , Patibandla N. , Hillig W. B. , Hudson J. B.
Published: March 2011

Aluminum nitride films were deposited on Si (100) and sapphire (1102) substrates by low pressure chemical vapor deposition using the metalorganic precursor trisdimethylaluminum amide, [(CH3)2AlNH2]3. Depositions were carried out in a cold wall reactor with substrate temperatures between 500 and 700 °C and precursor temperatures between 50 and 80 °C. The films were analyzed by X-ray photoelectron spectroscopy, X-ray diffraction, optical microscopy and scanning electron microscopy. The films were generally smooth and adherent with colors ranging from transparent to opaque grey. Cracking and spallation were seen to occur at high film thickness. Deposition rates ranged from 20 to 300 Å/min and increased with both precursor and substrate temperature. Carbon concentrations were small, < 5 at. %, while oxygen concentrations were higher and showed a characteristic profile versus depth in the film. High temperature compatibility testing with sapphire/AlN/MoSi2 samples was carried out to determine film effectiveness as a fiber coating in a composite.
Electrical and Dielectric Characteristics of SrTiO3 Thin Films Grown by PE-MOCVD Technique
Authors: Shi Z. Q. , Chern C. , Liang S. , Lu Y. , Safari A.
Published: March 2011

Epitaxial strontium titanate (SrTiO3) thin films have been grown by plasma enhanced metalorganic chemical vapor deposition (PE-MOCVD) technique on different bottom electrode materials, such as Pt/MgO and YBCO/LaAlO3. The as grown SrTiO3 film exhibited an epitaxial structure with <100> orientation perpendicular to the substrates as examined by X-ray diffraction (XRD). The electrical and dielectric properties of the films were investigated by capacitance-voltage (C-V) and current-voltage (I-V) measurements in a temperature range from 80K to 300K. The dielectric constant and dielectric loss were found to be 320 and 0.08 at 100 kHz and room temperature. The dc leakage current density and breakdown voltage were strongly dependent on the choice of the bottom electrode materials. For the films grown on YBCO/LaAlO3, the leakage current density is 8.8×10−7 A/cm2 at 200 kV/cm and the breakdown voltage is about 2.0 MV/cm. These results indicated that the SrTiO3 films are suitable for many devices applications. The frequency dependence of the dielectric constant and dielectric loss were studied in the range of 12 Hz to 1 MHz at room temperature. With the increase of the frequency, the dielectric constant showed a little decrease, while the dielectric loss exhibited a sharp increase which could be attributed to the electrode resistance loss.
Development and Implementation of Large Area, Economical Rotating Disk Reactor Technology for Metalorganic Chemical Vapor Deposition
Authors: Tompa G. S. , Zawadzki P. A. , Mckee M. , Wolak E. , Moy K. , Stall R. A. , Gurary A. , Schumaker N. E.
Published: March 2011

The vertical, high speed, rotating disk reactor (RDR) has, in recent years, found broad application in the Metalorganic Chemical Vapor Deposition of a variety of material systems. These applications include epitaxial films of III-V and II-VI compound semiconductors, oxides (such as YBCO superconductors/ferroelectrics and SiO2, amongst others), Group IV materials (such as diamond and SiC), and metals (such as copper and tungsten). As production of these material systems increases, so too does the need for economical, high yield equipment capable of producing these materials with high levels of uniformity and repeatability. We have used computational fluid dynamic modeling to investigate the complex flow and thermal dynamics required for scaling existing RDRs (as large as a 7.25″ diameter disk handling up to 3×3″ wafers) to larger dimensions (11″ and 12″ diameter disks for multiple 4″ and 15.5″ diameter disk for 3×6″ wafers). The scaling parameters predicted by the modeling codes are reviewed and correlate well with experimental results. Materials results on GaAs films using TBAs, TMGa, and TMA1 for the 11″ diameter system routinely demonstrate within wafer thickness uniformities of <1.1% for 3×4″ wafers, as well as for 6″ or 8″ diameters, wafer to wafer uniformities <1% and run to run repeatabilities within 1%. These results are verified by SEM analysis, as well as with GaAs/AJGaAs Bragg reflectors. The excellent results on the 11″ and 15.5″ diameter platters combined with modeling indicated that 4×4″ wafers on a 12″ diameter platter would produce ideal films which, indeed, is the case. The 11″ diameter results have been surpassed, demonstrating <0.9% for >9″ diameters (4×4″ wafers) on a 12″ diameter susceptor. With high reactant efficiencies (>3 6%), short cycle times between growths using the loadlock, and minimal maintenance requirements, the costs per wafer in a cost of ownership model are found to be dramatically less than in competitive technologies.
Some Considerations of MOCVD for the Preparation of High Tc Thin Films
Authors: Hitchman Michael L. , Shamlian Sarkis H. , Gilliland Douglas D. , Cole-Hamilton David J. , Thompson Simon C. , Cook Stephen L. , Richards Barbara C.
Published: March 2011

In this paper we first give a brief overview of the MOCVD of high temperature superconductors and consider the general requirements of a precursor. We then present results for deposition from Y containing precursors and compare apparent enthalpies of sublimation and deposition activation energies with values in the literature. The problem of Ba containing precursors are briefly reviewed and results given for the sublimation of and deposition from a new stable and volatile precursor. Finally, some comments are made about possible deposition mechanisms.
In Situ Heteroepitaxial Bi2Sr2CaCu2O8 Thin Films Prepared by Metalorganic Chemical Vapor Deposition
Authors: Dimeo Frank , Wessels Bruce W. , Neumayer Deborah A. , Marks Tobin J. , Schindler Jon L. , Kannewurf Carl R.
Published: March 2011

Bi2Sr2CaCu2O8 thin films have been prepared in situ by low pressure metalorganic chemical vapor deposition using fluorinated β–diketonate precursors. The influence of the growth conditions on the oxide phase stability and impurity phase formation was examined as well as the superconducting properties of the films. Thin films deposited on LaAIO3 substrates were epitaxial as confirmed by x-ray diffraction measurements, including θ-2θ and φ scans. Four probe resistivity measurements showed the films to be superconducting with a maximum Tc0 of 90 K without post annealing. This Tc0 is among the highest reported for thin films of the BSCCO (2212) phase, and approaches reported bulk values.
Deposition of Cerium Dioxide Thin Films on Silicon Substrates by Atomic Layer Epitaxy
Authors: Mölsä Heini , Niinistö Lauri
Published: March 2011

CeO2 overlayers up to 360 nm thick were deposited on Si(100) substrates in a flowtype ALE reactor from Ce(thd)4 (thd = 2,2,6,6-tetramethyl-3,5-heptanedione) precursor and ozone. The growth rate was studied as a function of deposition and source temperatures, reactor pressure and pulse durations. The films were characterized for crystallinity, thickness and composition by using XRD, profilometry, XRF, RBS, XPS and SIMS techniques. Films deposited at 375 °C showed a preferential (110) orientation while at 425 °C they were (111) preferentially oriented. Due to the steric hindrance caused by the bulky precursor the growth rate was only 0.4 Å/cycle.
Growth of BaTiO3 Thin Films by MOCVD
Authors: Kaiser Debra L. , Vaudin Mark D. , Gillen Greg , Hwang Cheol-Seong , Robins Lawrence H. , Roiter Lawrence D.
Published: March 2011

Polycrystalline thin films of BaTiO3 were deposited on fused quartz substrates at 600°C by metalorganic chemical vapor deposition (MOCVD). The films were characterized by x-ray powder diffraction (XRD), transmission electron microscopy (TEM), secondary ion mass spectroscopy (SIMS) and Raman spectroscopy. Films prepared in the early stages of this study that had appeared to contain only crystalline BaTiO3 by XRD were found to have nonuniform composition and microstructure through the film thickness by SIMS and TEM. The MOCVD system was then modified by installing a process gas bypass apparatus and an elevated pressure bubbler for the titanium isopropoxide precursor. A 1.2 μm thick BaTiO3 film prepared in the modified system demonstrated much improved compositional and microstructural uniformity through the thickness of the film. This film had a columnar microstructure with grain widths of 0.1–0.2 μm and exhibited tetragonality as detected by Raman spectroscopy.
Deposition of Dielectric Thin Films by Irradiation of Condensed Reactant Mixtures
Authors: Moore J. F. , Strongin D. R. , Ruckman M. W. , Strongin M.
Published: March 2011

Results of ongoing investigations of a new method for processing molecular solids to form refractory thin films are presented. We have extended past work on boron nitride and alumina growth from molecular solids induced by synchrotron radiation (SR), to silica growth from tetramethylsilane and water at 80 K. Also reported are experiments where alumina is formed using 4.64 eV laser irradiation. The majority of the results suggest that with SR, the film growth is induced by secondary electrons from the substrate, whereas laser light excites the film growth by direct photolysis. Implications of this will be discussed.
Influence of SiC Additions on the Microstructure of Gray Cast Iron
Authors: Schubert W. D. , Ta A. T. , Kahr G. , Benecke Th. , Lux B.
Published: March 2011

The influence of additions of different SiC grades on the solidification of hypoeutectic and eutectic gray cast iron has been studied and compared with the additions of “FeSi 75” and pure silicon.

It is shown that additions of SiC change undercooling, microstructure as well as graphite shape and distribution in cast iron melts in a different manner than either FeSi or pure Si do. The difference is explained by the special dissolution kinetics of SiC which leads to formation of graphite and a lonqer-lastirg influence of carbon agglomerates in the melt. It is shown that SiC grades which are partially protected by SiO2 films from rapid dissolution in the iron melt show the most pronounced effect.

From the laboratory experiments it can be concluded that melt additions of special SiC grades can modify the microstructure of gray cast iron. A-graphite is more evenly distributed and formation of the Fe/Fe3C eutectic is more difficult. Similar influences are known from industrial production and can now be partially explained.
Structure and Formation of Vermicular Graphite
Authors: Xijun Den , Peiyue Zhu , Gifu Liu
Published: March 2011

Using both liquid quenching and SEM technique is found that the vermicular graphite (CVG ) is formed Mainly in two ways. First, it grows out from flake graphite, and second, it degenerates, from spheroidal graphite (SC).According to this, two models of morphology and formation process.of CVS are sugguted. It. is discovered that the qrowth.direction of CVG of ten changes from a-to c-direction, or vice versa. Because of thu influence of modifying elements, the CVG is. twistad sq-verely, changing its growth direction continually and branching frequently. The growth of the branches may be in a-and/or c-direction; and their tips may be round and/or sharp. In all cases, there exists a large fraction of thick flake graphithe in the vermicular graphite. It is Suggested that the redistribution of modifying elements plays an importeant role in the formatinn of CVG.
Solidification of Flake, Compacted/Vermicular and Spheroidal Graphite Cast Irons as Revealed by Thermal Analysis and Directional Solidification Experiments
Authors: Stefanescu Doru Michael
Published: March 2011

When trying to understand the thermal behavior of solidifying cast irons, two experimental procedures seem to be especially helpful in generating the expected type of information, which then can be used for a quantitative understanding of the phenomena. They are thermal analysis and directional solidification.
Computer Simulation of Solidification of Nodular Cast Iron
Authors: Su Kou-Chang , Ohnaka Itsuo , Yamauchi Isamu , Fukusako Tatsuichi
Published: March 2011

Solidification of a nodular iron casting was simulated by an undercooling nucleation and diffusion controlled growth model. Simulated cooling curves were similar to measured ones but estimating nodular size distribution requires improving the model.
Further use of Secondary Ion Mass Spectrometry in the Study of Graphite Morphology Control TN Cast Irons
Authors: Franklin S. E. , Stark R. A.
Published: March 2011

In a previous publication, preliminary results obtained using secondary ion mass spectrometry to determine selective elemental distributions in cast iron were reported. These results were used to tentatively assign possible roles to the important solutes in controlling the graphite morphology. The current paper is a continuation of this work and presents the most recent results of the SIMS analysis.
Transition from Grey to White and White to Grey in Fe-C-X Eutectic Alloys
Authors: Magnin P. , Kurz W.
Published: March 2011

The effect of small additions of Si, P, Cr, Mn and Ti on transition velocities from grey to white and white to grey of pure Fe-C eutectics has been measured by varying growth rates in directional solidification experiments. Growth undercoolings were measured as a function of growth rate, while white and grey eutectic temperatures were obtained from DTA experiments. As a result of these experiments, alloying elements can be classified into three categories : graphitizing (Si, P), carburizing (Cr) and “opposite effect” (Mn, Ti). Each category is characterized by a given influence on eutectic temperature, growth undercooling, and nucleation of cementite. A qualitative model which permits determination of the influence of alloying elements on these latter three parameters is proposed.