bluuebunny/crossref_metadata_2025 huggingface dataset:
Tumor Cell - Substrate Stabilization Mediated by Integrins
Authors: Patton John T. , McIntire Larry V. , Menter David G. , Nicolson Garth L.
Published: March 2011

Metastasis formation is dependent on the arrest and stabilization of adhesive interactions to prevent detachment from secondary sites. Primary receptor-ligand interactions are not sufficient to maintain prolonged adhesive contacts without secondary events that lead to stabilization. Tumor cell arrest and stabilization were studied under physiologically relevant shear conditions. We used a parallel-plate flow chamber with surfaces coated with human plasma fibronectin or vitronectin. Our previous work suggested that stabilization of cells to immobilized proteins is in part attributed to transglutaminase covalently cross-linking cytoskeletal-integrin-fibronectin multiprotein complexes via lysine-glutamine linkages. To study the role of integrins in mediating arrest and initiating stabilization we used a human melanoma line (70w) and polyclonal antibodies that inhibit the function of the fibronectin (α5β1) and vitronectin (αvβ3/β5) integrin receptors. To confirm the role of integrins in initiating stabilization we used CHO (Chinese hamster ovary) cells selected for low levels of α5β1integrin expression and integrin transfected CHO cells selected for α5βloverexpression. The level of fibronectin receptor surface expression was inversely related to the adhesion stabilization lag time. These studies confirmed that integrins are essential for mediating arrest and initiating stabilization. They also confirm that secondary events are necessary for complete stabilization to occur. Finally, it is important to note that the arrest and stabilization methods we have developed are capable of detecting biologic effects at far greater sensitivity than static adhesion assays. Some examples of pharmacologic agents or biomaterials effects that can be detected using stabilization assays include: 1) very low drug doses, 2) very low levels of peptide, carbohydrate, and antibody inhibitors, 3) slight modification of endogenous protein expression by antisense oligonucleotides or transfected genetic expression constructs.
Characterization of Biodegradable Polyester Films and their Interaction with Hepatocytes
Authors: Park Ann , Cima Linda Griffith , Kaufmann P.-Matthias
Published: March 2011

Polymers derived from lactic and glycolic acid have achieved success in many medical applications and have been investigated as possible materials for degradable scaffolds required in tissue transplantation. Previous investigators have found significant differences in the behavior of cells cultured on chemically similar polyesters of this family but the mechanisms for these differences have remained unclear.

In this study, we fabricated polylactic acid, polylactic-co-glycolic acid, and blend films by melt-processing. The bulk and surface properties of these films were characterized by GPC, DSC, WAXS, SEM, and contact angle. All films were smooth and amorphous and differed only in chemical composition. The films were assessed for their ability to sustain or promote hepatocyte attachment, growth, and function. Cells adhered to and exhibited similar morphology on all substrates. Cells decreased in number to 50–60% of the initial cell number but exhibited high retention of differentiated function on all of the polymer substrates over five days. Cell response was not statistically different on the different substrates indicating that chemical composition, in our range of polymer formulations, does not affect cell behavior.
Structural Elements Which Govern the Resistance of Intestinal Tissues to Compound Transport
Authors: Rubas Werner , Cromwell Mary , Gadek Tom , Narindray Daljit , Mrsny Randy
Published: March 2011

The series of cyclized RGD peptides in this study demonstrated a very low partition into octanol as judged by HPLC. Thus, these molecules are likely to move predominantly through the paracellular pathway. Permeability across Caco-2 monolayers was determined using reversed phase HPLC and found to be restricted by molecular weight and possibly charge-charge interactions between the solute and charged moieties within the paracellular shunt. When normalized for molecular weight, molecules with a net charge between -1 and -2 demonstrated the highest permeabilities, which suggests an optimal net charge with respect to permeability.
Theoretical Prediction of Gas-Phase Nucleation Kinetics of SiO
Authors: Zachariah Michael R. , Tsang Wing
Published: March 2011

This paper describes the application of ab-initio molecular orbital (MO) theories in conjunction with reaction rate theory to obtain thermochemistry and energetics of nucleation processes. The specific example used for the illustration of this approach is the nucleation of SiO. MO computations on the equilibrium structures have shown the polymers up to the tetramer to be planar rings and exothermic to addition of the monomer. Transition state analysis has shown that subsequent addition of the monomer (SiO) most likely proceeds without an energy barrier. Reaction rate theory analysis of the polymerization shows the rate coefficients to be very pressure dependent, with the dimer formation process rate limiting. Oxidation of clusters however showed a substantial barrier which should result in oxygen deficient clusters.
New Organometallic Selenium Reagents for Low Temperature Omcvd of Znse
Authors: Danek M. , Huh J-S. , Jensen K. F. , Gordon C. , Kosar W. P.
Published: March 2011

ZnSe epitaxial films have been grown on (100) GaAs by reduced pressure organometallic chemical vapor deposition (OMCVD) from tertiary-butyl(allyl)selenium (tBASe) and dimethylzinc triethylamine adduct (DMZnNEt3) at temperatures of 325-450ΰC. Good surface morphology, film crystallinity and interface quality have been found with scanning electron microscopy (SEM), double crystal X-ray diffraction (DCD) and Rutherford back scattering spectroscopy (RBS). Secondary ion mass spectrometry (SIMS) shows negligible carbon concentration (below 5x1017atoms/cm3). Low temperature photoluminescence (PL) exhibits a strong near band-edge emission with a dominant donor-bound peak. Gas-phase pyrolysis of tBASe has been probed at reduced pressure in a molecular beam mass spectrometric system in hydrogen and deuterium carrier gases. The precursor decomposes above 200ΰC by β-hydrogen elimination and by homolysis of the Se-C bonds. High isobutene vs. isobutane ratios (50-100) indicate a predominance of β-hydrogen elimination over homolysis at temperatures below 400ΰC. Diallylselenium is present in the gasphase in low concentrations at temperatures of 200-350ΰC. Diallylselenium, methylallylselenium and dimethyl-selenium have been observed as minor by-products during pyrolysis of co-dosed tBASe and DMZnNEt3. The effect of the retro-ene decomposition pathway of allylselenium reagents on carbon incorporation into ZnSe films is further probed by growth experiments with in situ generated 2-methylpropaneselenal.
Picosecond Optical Second Harmonic Studies of Adsorbate Reduction Kinetics on Cadmium Sulfide
Authors: Scott T. W. , Martorell J. , Chang Y. J.
Published: March 2011

Time resolved surface second harmonic generation has been used to probe the photoreduction kinetics of malachite green adsorbed onto single crystal cadmium sulfide. A detailed analysis is presented of how the adsorbates and the noncentrosymmetric substrate contribute separately to the total second harmonic signal. Conditions under which the adsorbates can be cleanly detected are described. To complement kinetic measurements of adsorbate reduction, the time evolution of conduction band carriers was determined using sum frequency up conversion of the recombination luminescence. In addition, the formation and decay of surface trapped carriers was monitored using near infrared transient absorption. Comparing the time scale for photoreduction with the relaxation kinetics of mobile and trapped charge carriers indicates that short lived mobile carriers rather than longer lived surface trapped carriers dominate interfacial charge transfer in this system.
Adsorption and Reaction of TiCl4 on W(100)
Authors: Chen Wei , Roberts Jeffrey T.
Published: March 2011

The adsorption and reaction of titanium tetrachloride (TiC14) on W(100) was investigated using temperature programmed desorption mass spectrometry (TPRS), x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and low energy electron diffraction (LEED). TiC14 adsorbs molecularly on W(100) at 100 K. Desorption from the molecularly bound state occurs near 220 K. Competing with desorption is dissociation to adsorbed TiCl3, which reacts to form gaseous TiCl4 near 450 K. TiC13 also decomposes into atomically adsorbed Ti and Cl on the surface upon heating to 700 K.
Ecr Plasma Enhanced MOCVD of Titanium Nitride
Authors: Gross M.E. , Weber A. , Nikulski R. , Klages C.-P. , Charatan R.M. , Brown W.L. , Dons E. , Eagleshamn D.J.
Published: March 2011

The ability to deposit high purity TiN by a CVD process that can provide improved conformality over current sputter deposition processes is critical for multilevel Si ULSI device applications. Low temperature deposition of high quality TiN films has been achieved by an ECR plasma enhanced CVD process using the metal-organic precursor, tetrakis(dimethylamido) titanium, Ti(N(CH3)2)4 (TDMAT). TDMAT is introduced into the downstream region of either a N2 or NH3 ECR plasma to deposit highly conducting films at deposition temperatures of as low as 100°C. The electrical resistivity of the TiN films decreases from 100-150μΩ-cm at a deposition temperature of 100°C to 45μΩ-cm at 600°C. The choice of plasma gas, N2 or NH3, affects the composition as well as the crystallographic texture of the films, which exhibit preferred (200) and (111) orientations, respectively. Pretreatment of the Si substrate with N2 or NH3 plasmas also affects the film morphologies, as demonstrated by switching the plasma gas between pretreatment and deposition.
Investigations of Tin and Ti Film Deposition by Plasma Activated Cvd Using Cyclopentadienyl Cycloheptatrienyl Titanium, a Low Oxidation State Precursor
Authors: Charatan Robert M. , Gross Mihal E. , Eaglesham David J.
Published: March 2011

Sequential Ti and TiN thin film deposition by CVD is highly desirable for advanced Si integrated circuit applications. To date, most CVD TiN work has been performed using Ti(IV) compounds. We have investigated plasma assisted CVD using a lower oxidation state precursor, cyclopentadienyl cycloheptatrienyl titanium, (C5H5)Ti(C7H7) (CPCHT), which might provide a more facile pathway to both Ti and TiN film formation. CPCHT was introduced with H2 carrier gas into the downstream region of an NH3, N2 or H2 plasma. Low resistivity (100-250 μΩ-cm), nitrogen rich TiN films with little C or O incorporation were deposited at 300 to 600°C, inclusive with either activated N2 or NH3. Although the film texture was influenced by the chosen plasma gas, the average grain size of the N2 and NH3 plasma deposits was similar. Annealing studies showed that the CVD TiN was an effective diffusion barrier between aluminum and silicon to at least 575°C. TEM micrographs revealed that, in contrast to many CVD metal films, the growth of this TiN was not columnar. Film conformality was investigated by scanning electron microscopy (SEM). Experiments performed with activated H2 resulted in deposits of Ti contaminated with C. No depositions were observed in the absence of plasma excitation.
Characterization of Silicon-Nitride Film Growth by Remote Plasmaenhanced Chemical-Vapor Deposition (Rpecvd)
Authors: Lu Zhong , Ma Yi , Habermehl Scott , Lucovsky Gerry
Published: March 2011

We have characterized RPECVD formation of Si-nitride films by relating the chemical bonding in the deposited films to the growth conditions. Gas flow rates for different N- and Si-atom source gases have been correlated with (i) the film stoichiometry, i.e., the Si/N ratio, and the (ii) the growth rate. N2 and NH3 were used as N-atom source gases, and were either delivered (i) up-stream through the plasmageneration tube, or (ii) down-stream. Different flow-rate ratios of NH3/SiH4 were found for deposition of stoichiometric Si-nitride films using up-stream or down-stream introduction of NH3. This is explained in terms of competition between excitation and recombination processes for the N-atom precursor species. Stoichiometric nitride films could not be obtained using the N2 source gas for (i) either up-stream or down-stream delivery, and (ii) for plasma powers up to 50 W. This is attributed to the higher relative binding energy of N-atoms in N2 compared to NH3, and to significant N-atom recombination at high N2 flow rates through the plasma generation region.
Flow Tube Kinetics of Gas-Phase Cvd Reactions
Authors: Weiller Bruce H.
Published: March 2011

This paper explores the use of a flow-tube reactor coupled to an FTIR spectrometer to study gas-phase chemical reactions in CVD systems. We show that our apparatus can generate reliable kinetics data by reproducing the literature rate constant for the reaction between O3 and isobutene. We present data from this apparatus on two technologically important systems: TiN from Ti(NMe2)4 (TDMAT) and NH3 and SiO2 from tetraethoxysilane (TEOS) and O3. The results presented include kinetics data for the reaction of Ti(NMe2)4 with NH3 and ND3 at room temperature and the IR spectra of the products from the reaction of TEOS with O3 at 175°C.
Krf Excimer Laser Induced Photochemical Modification of Polyphenylenesulfide Surface Into Hydrophilic Property
Authors: Kashiura H. , Okoshi M. , Murahara M.
Published: March 2011

Carboxyl groups were photochemically substituted for hydrogen atoms at a polyphenylenesulfide surface by using an KrF excimer laser light and vaporized formic acid. In the process, the polyphenylenesulfide film was placed in the formic acid vapor, and the surface was irradiated with the KrF excimer laser light. Irradiating with the laser, the surface was dehydrogenated by the hydrogen atoms which were photodissociated from the formic acid; the dangling bonds on the surface combined with the COOH radicals which were also photodissociated. The hydrophilic property of the photomodified surface was evaluated by the measurement of the contact angle with water. The dehydrogenation reaction and the substitution reaction of the COOH radicals were inspected by XPS analysis. Surface morphology of the sample was observed by SEM photograph.
Scanning Tunneling Microscopy Observation of the Reaction of AlCl3 on Si(111)-7×7 Surface
Authors: Uesugi Katsuhiro , Takiguchi Takaharu , Izawa Michiyoshi , Yoshimura Masamichi , Yao Takafumi
Published: March 2011

The initial stage of the reaction of aluminum trichloride (AlCl3) with the Si(111)-(7×7) surface and the annealing effects of the adsorbed surface are investigated with a scanning tunneling microscope (STM). Reacted and unreacted sites manifest in the contrast of adatom sites on the AlCl3-exposed surface. An AlCl3 molecule dissociatively adsorbs onto the Si( 111)-(7×7) surface at room temperature, which yields C1 atoms. Preferential adsorption site is found to be the center adatom site rather than the corner adatom site, and Cl atom adsorbs onto the top site of the center Si adatom. The migration of adsorbed molecules (AlClx) in the (7×7) unit cell is observed at room temperature. The SiCl,, species desorb from the surface by thermal annealing at 600 'C, leaving vacancies behind. After annealing at 1200 0C, Al deposition occurs in a limited area and the surface shows the V/7×V7 reconstruction, which is a characteristic Al-induced surface structure.
High Selective Etching of SiO2/Si by ArF Excimer Laser
Authors: Kitamura K. , Murahara M.
Published: March 2011

Dry etching of SiO2 insulation layer has been required in the Si semiconductor manufacturing process. The etching of SiO2/Si is chemically carried out by using HF solution. We successfully demonstrated a new method for exclusive etching of SiO2 using the nitrosyle fluoride (NFO) gas which was produced from the mixed gas of NF3 and O2 with an ArF excimer laser irradiation.

SiO2 and Si substrates were placed side by side in a reaction cell which was filled with 3% O2 gas in NF3 at the gas pressure of 380 Torr. ArF excimer laser beam was irradiated parallel to the substrates. The laser fluence was kept at lOOmJ/cm2. As soon as the mixed gas of NF3 and O2 was irradiated with the ArF laser beam, an intermediate product of NFO was produced. The chemical behavior of NFO was confirmed from the UV absorption spectrum with absorption in the 310 to 330nm wavelength region. In the presence of SiO2, the absorption of NFO diminished. The absorption of NO2, instead of NFO, appeared at 350nm. This indicates that the oxygen atoms of SiO2 were pulled out by NFO.

The etching reactions continued for 3 minutes after irradiation when the SiO2 and Si substrates were kept in an atmosphere of the reactant gases. As a result, not the Si but SiO2 substrate was etched with the depth of 2000Å.
Plasma Etching and Surface Analysis of a-SiC:H Films Deposited by Low Temperature Plasma Enhanced Chemical Vapor Deposition
Authors: Thomas J. H. , Loboda M. J. , Seifferly J. A.
Published: March 2011

Organosilicon precursors were used to deposit thin films of highly stable amorphous hydrogenated silicon carbide at low temperatures by plasma enhanced chemical vapor deposition. X-ray photoemission and Auger electron spectroscopy were employed to characterize the surface chemistry of air exposed and plasma etched films. Auger analysis of the as-deposited material shows its composition to be constant throughout its depth. RF plasma etching was performed in CF4/O2 and SF6/O2 gas mixtures. Etch rates in these atmospheres are similar to those reported in the literature. After plasma etching, the surface was converted to a highly fluorinated state. In addition to the expected SiC bond, Si-OF bonds were found after plasma etching. Fluorocarbon residue was not produced in this process. Chlorine etching of this low temperature PECVD film is described and is shown to be compatible with standard integrated circuit manufacture processing as an hermetic-like sealant.
Surface Perturbation by Energetic Particle Beams
Authors: Chang Che-Chen , Yang Jung-Yen , Shieh Jaw-Chang
Published: March 2011

The state of the surface after energetic keV particle bombardment is investigated using molecular dynamics. The model utilizes a Ag{110} microcrystallite which is statically bombarded by Ar particles at normal incidence. After being bombarded at incident energy of 1 keV, the relocation probability is <0.3 for all the surface atoms initially residing within four lattice spacings from the target. The probability decreases exponentially as the initial distance of the substrate atom from the target is increased. The most probable distances of displacement from the lattice site also vary with the initial atomic distance from the target atom. The probable displacement of the surface atom, except the target atom, is less than one twentieth of the surface lattice spacing. An analytical formulae for the initial-distance dependence of the relocation probability is also proposed. The formula has three adjustable parameters which are determined by the least-squares method.
Cleaning during Initial Stages of Epitaxial Growth in an Ultrahigh Vacuum Rapid Thermal Chemical Vapor Deposition Reactor
Authors: Sanganeria Mahesh K. , Violette Katherine E. , ÖZtÜRk Mehmet C. , Harris Gari , Lee C. Archie , Maher Dennis. M.
Published: March 2011

In this paper, we report our results on surface preparation for the growth of epitaxial Si films. Hydrogen passivated surfaces are currently being investigated for application in Si epitaxy to eliminate the high temperature in-situ bake necessary to remove the native oxide. Hydrogen passivation is obtained by a dilute HF dip before the substrate is loaded in the process chamber. However the passivation is partially lost when the HF dip is followed by a water rinse which results in oxygen absorption on the substrate. It was found that the peak oxygen concentration at the epitaxy substrate interface increase by an order of magnitude due to a five minute water rinse. We report here that oxygen and carbon at the epitaxy substrate interface can be desorbed during initial stage of epitaxial growth by reducing epitaxial growth rate. In this work, epitaxial Si films were deposited over a wide range of growth rates obtained by varying Si2H6 flow rates. The peak oxygen concentration decreases by an order of magnitude by changing the growth rate from 3000 to 700Å/kminute for a deposition temperature of 800°C. We believe that at higher growth rates Si overgrows on absorbed oxygen maintaining epitaxial alignment reflected in the good electrical quality of the epitaxial films. However, at low growth rates oxygen has sufficient time to desorb before overgrowth can take place, improving the epitaxy substrate interface quality.
Growth and Characterization of Si-GaP and Si-GaP-Si Heterostructures
Authors: Dietz N. , Habermehl S. , Kelliher J. T. , Lucovsky G. , Bachmann K. J.
Published: March 2011

The low temperature epitaxial growth of Si / GaP / Si heterostructures is investigated with the aim using GaP as a dielectric isolation layer for Si circuits. GaP layers have been deposited on Si(100) surfaces by chemical beam epitaxy (CBE) using tertiarybutyl phosphine (TBP) and triethylgallium (TEG) as source materials. The influence of the cleaning and passivation of the GaP surface has been studied in-situ by AES and LEED, with high quality epitaxial growth proceeding on vicinal GaP(100) substrates. Si / GaP / Si heterostructures have been investigated by cross sectional high resolution transmission electron microscope (HRTEM) and secondary ion mass spectroscope (SIMS). These methods reveal the formation of an amorphous SiC interlayer between the Si substrate and GaP film due to diffusion of carbon generated in the decomposition of the metalorganic precursors at the surface to the GaP/Si interface upon prolonged growth (layer thickness > 300Å). The formation of twins parallel to {111} variants in the GaP epilayer are extended into the subsequently grown Si film with minor generation of new twins.
Growth Kinetics and Corresponding Luminescence Characteristics of Amorphous C:H Deposited from Ch4 by Dc Saddle-Field Plasma-Assisted Cvd
Authors: Kruzelecky Roman V. , Wang Chun , Zukotynski Stefan
Published: March 2011

Hydrogenated amorphous carbon (a-C:H) thin films were deposited onto various substrates at 200 °C by DC saddle-field glow-discharge dissociation of CH4. In situ plasma probe mass and energy spectroscopy was employed to systematically study the effects of the discharge parameters on the formation of reactive precursors. The ion current at the substrate holder consists mainly of CH3+ for pressures < 75 mTorr; higher pressures and lower discharge currents encourage the formation of C2Hn+ and C3Hn+ radicals in the discharge. The growth rate was largely independent of the total pressure, increasing approximately linearly with the discharge current. Under 476 nm photo-excitation, the a-C:H films exhibited room-temperature photoluminescence in the visible, near 1.9 eV, with an intensity that was strongly dependant on the discharge parameters.
Predictive Surface Kinetic Analysis: The Case of TiSi2 CVD
Authors: Mendicino M. A. , Southwell R. P. , Seebauer E. G.
Published: March 2011

Recently, TiSi2 has been the object of considerable study because of its low resistivity among the transition metal silicides and its compatibility with existing ULSI technology [1,2]. Film growth by CVD offers the potential for selective area deposition and high production throughput. However, selective CVD of TiSi2 from gas phase SiH4 and TiCl4 is usually accompanied by a competing reaction which consumes intolerable amounts of the Si substrate [3,4]. Controlling this consumption is crucial in TiSi2 growth; however, no quantitative correlation exists between silicon consumption and growth conditions or film thickness. Additionally, the reaction mechanism for TiSi2 growth is poorly understood, and some disagreement even exists about the reaction stoichiometry [5,6]. The combined CVD/UHV approach we have developed fills many gaps in the current understanding of TiSi2 CVD.
Molecular Dynamics Simulation of Large Cluster Growth
Authors: Zachariah Michael R. , Carrier Michael J. , Blaisten-Barojas Estela
Published: March 2011

Classical Molecular dynamics simulation of silicon cluster growth (up to 1000 atoms) have been conducted using the Stillinger-Weber 3-body interaction potential. The cluster binding energy has been fit to an expression that separates the surface and bulk contribution to the energy over a wide temperature and size range. Cluster growth simulations show that large heat release results from new bond formation at gas kinetic rates (i.e. sticking coefficient = unity). Temperature was found to be the primary controlling process parameter in the evolution of cluster morphology from an aggregate to a coalesced cluster below 1000 K, with the impact parameter playing a secondary role.
Thermochemical Data for CVD Modeling from Ab initio Calculations
Authors: Ho Pauline , Melius Carl F.
Published: March 2011

Ab initio electronic-structure calculations are combined with empirical bond-additivity corrections to yield thermochemical properties of gas-phase molecules. A self-consistent set of heats of formation for molecules in the Si-H, Si-H-Cl, Si-H-F, Si-N-H and Si-NH- F systems is presented, along with preliminary values for some Si-O-C-H species.
Growth of Epitaxial β-SiC Films on Porous Si(100) Substrates from MTS in a Hot Wall LPCVD Reactor
Authors: Chiu Chien C. , Desu Seshu B. , Chen Gang
Published: March 2011

β–SiC thin films were epitaxially grown on porous Si(100) substrates at 1150° C from methyltrichlorosilane (CH3SiCl3 or MTS) in a hot wall reactor by Vsing low pressure chemical vapor deposition (LPCVD). The growth rate was 120 Å/min. Epitaxial β–SiC(100) thin films were obtained after a deposition time of 12.5 min. The crystallinity of the β–SiC films was affected by the deposition time. For instance, rotational β–SiC(100) crystals and polycrystalline β–SiC with a highly preferred orientation of (100) planes were observed for a deposition time of 50 min. The results from XRD and TEM indicated that polycrystalline β–SiC films with a preferred orientation of β–SiC(111) appeared after further increasing the deposition times (time ≥ 75 min). The change in crystallinity is attributed to increasing roughness with increasing deposition time.
Precursor Delivery for the Deposition of Superconducting Oxides: a Comparison Between Solid Sources and Aerosol
Authors: Thomas O. , Weiss F. , Hudner J. , Haase R. , Dubourdieu C. , Mossang E. , Didier N. , Senateur J.P.
Published: March 2011

Epitaxial thin layers of YBa 2Cu 3O7−x (Tc=90 K, Jc (OT, 77 K) = 2 106 A cm-2) were synthesised by thermal decomposition (750 − 830 °C) of tetramethylheptanedionates of yttrium, barium and copper in the presence of oxygen. Three different precursor delivery systems have been used: In the first, the precursor's surface is flushed with the carrier gas (Ar), in the second, argon is directly injected through the powder leading to a much higher transport rate, and in the third, a liquid (diketonates in a solvent) is nebulized via a piezoelectric transducer. The transport and deposition rates obtained in these three different reactors will be compared.
LPCVD of InN on GaAs(110) Using HN3 and TMIn: Comparison with Si(100) Results
Authors: Bu Y. , Lin M.C.
Published: March 2011

Low-pressure chemical vapor deposition (LPCVD) of InN and laser-assisted LPCVD on GaAs(110) and Si(100) using HN3 and trimethyl indium (TMIn) has been studied with XPS, UPS and SEM. Without 308-nm excimer laser irradiation, InN film was built on the GaAs but not on Si surface under the present low-pressure conditions. When the photon beam was introduced, InN films with In:N atomic ratio of 1.0±0.1 and a thickness of more than 20 Å (the limit of the electron escaping depth for the In3d X-ray photoelectrons) were formed on Si(100) surface. In both cases, the formation of surface nitrides at the initial film growth processes was clearly indicated in the XPS spectra. The He(II) UP spectra taken from InN films on GaAs and Si are nearly identical and agree well with the result of a pseudo-potential calculation for the InN valence band. The corresponding SEM pictures showed smooth InN films on GaAs(110), while grains with diameter of ∼100 nm were observed for InN on Si(100).
Synthesis and Decomposition of a Novel Carboxylate Precursor to Indium Oxide
Authors: Hepp Aloysius F. , Andras Maria T. , Duraj Stan A. , Clark Eric B. , Hehemann David G. , Scheiman Daniel A. , Fanwick Phillip E.
Published: March 2011

Reaction of metallic indium with benzoyl peroxide in 4-methylpyridine (4-Mepy) at 25 °C produces an eight-coordinate mononuclear indium(III) benzoate, In(η2-O2CC6H5)3(4- Mepy)2 4H2O (I), in yields of up to 60%. The indium(III) benzoate was fully characterized by elemental analysis, spectroscopy, and X-ray crystallography; (I) exists in the crystalline state as discrete eight-coordinate molecules; the coordination sphere around the central indium atom is best described as pseudo-square pyramidal. Thermogravimetric analysis of (I) and X-ray diffraction powder studies on the resulting pyrolysate demonstrate that this new benzoate is an inorganic precursor to indium oxide. Decomposition of (I) occurs first by loss of 4-methylpyridine ligands (100°-200°C), then loss of benzoates with formation of In2O3 at 450°C. We discuss both use of carboxylates as precursors and our approach to their preparation.
Optimization of Jc for Photo-Assisted MOCVD Prepared YBCO Thin Films by Robust Design
Authors: Chou P. C. , Zhong Q. , Li Q. L. , Ignatiev A. , Wang C. Y. , Deal E. E. , Chen J. G.
Published: March 2011

Metalorganic chemical vapor deposition (MOCVD) is emerging as a practical high Tc superconducting thin film preparation technique for industrial application. Intrinsically this technique involves a large number of variable parameters. This is especially critical for the quarternary or higher high Tc materials. Thus, effective methods are required to optimize the parameters for the preparation of high Tc films. A matrix experimental design named Robust Design has been employed for this purpose. The first-phase design was based on a starting knowledge of growth temperature and pressure, and annealing temperature for MOCVD preparation of YBCO thin films. A minimum lab effort of only nine deposition experiments was then used to optimize the process control parameters of precursor oven temperature, carrier gas (Ar) flow rate, O2 flow rate and N2O flow rate. The results were then followed by three confirmation depositions. The Robust Design resulted in the growth of YBCO film with Tc consistently in the range of 87.0 K to 90.2 K and Jc improved from about 1.0 × 106 A/cm2 to 3–5 × 106 A/cm2.
Epitaxial Growth of Ba1−xSrxTiO3 Thin Films on YBa2Cu3O7−x Electrode by PE-MOCVD
Authors: Chern C.S. , Liang S. , Shi Z.Q. , Yoon S. , Safari A. , Lu P. , Kear B.H.
Published: March 2011

Plasma-enhanced metalorganic chemical vapor deposition (PE-MOCVD) has been successfully employed for the deposition of (100) oriented barium strontium titanate (BST) thin films on a variety of substrate and electrode materials. The incorporation of O2 plasma, which was used as oxidation reactant, has helped to reduce the required temperature for deposition of high-quality STO and BST thin films. This low temperature processing may make it possible to integrate BST on Si and GaAs. BST films with low leakage current densities of about 10−7 A/cm2 at 2-volt (about 105 V/cm) operation were obtained from PE-MOCVD processing. Moreover, the BST results of capacitance-temperature (C-T) measurements show that most of the PE-MOCVD BST films have Curie temperatures of about 30–35°C and a peak dielectric constant of 600–800 at zero bias voltage, The sharp transition in the C-T data indicates that the BST films may have a high induced pyroelectric coefficient at room temperature, which is highly desirable for uncooled IR imaging arrays. The x-ray diffraction and Rutherford backscattering spectrometry results show that the BST film composition reproducibility was well controlled at around Ba0.75Sr0.25TiO3 with a 4% variation. Device quality BST thin films with the thickness of 1000–2000 Å were produced. These results indicate that PE-MOCVD has high potential to be further developed and promoted as a production deposition technique providing high permittivity dielectric thin films for microelectronics and IR sensor industries.
Raman Spectra of MOCVD-Grown Ferroelectric PbTiO3 Thin Films
Authors: Feng Z. C. , Kwak B. S. , Erbil A. , Boatner L. A.
Published: March 2011

Lead titanate (PbTiO3) has been grown on a variety of substrates by using the metalorganic chemical vapor deposition (MOCVD) technique. The substrates employed included Si, GaAs, MgO, fused-quartz, sapphire, and KTaO3. Raman spectra from these heterostructures are presented. All of the films exhibited the strong, narrow spectral features characteristic of PbTiO3 perovskite-oxide crystals and indicative of high crystalline quality. Temperature behaviors of the Raman modes, including the socalled “soft-mode”, were studied. A “difference-Raman” technique was used to distinguish the contributions of the PbTiO3 film and the KTaO3 single-crystal substrate.
Recent Advances in the CVD of Metal Nitrides and Oxides
Authors: Gordon Roy G.
Published: March 2011

Use of metal-organic precursor materials has permitted thermal CVD of many metal nitrides at remarkably low temperatures and without corrosive by-products. Metallic TiN, VN, Nb3N4 and Mo2N3; semiconducting GaN and Sn3N4; and insulating AIN, Zr3N4, Hf3N4 and Ta3N5 can be deposited at temperatures typically in the range 100 to 400 C. Deposits free of carbon are obtained by transamination reactions of metal dialkylamido precursors with a sufficiently large excess of ammonia. The resulting TiN films are good diffusion barriers, and provide low contact resistance between metals and silicon.

Transparent semiconducting oxide films, such as SnO2, ZnO and TiO2, are often made by MOCVD for use in solar cells, energy-efficient window coatings and electro-optical displays. These wide band-gap semiconductors can be doped to n-type conductivity by a variety of dopant elements. Fluorine is the dopant which produces materials with the highest electron mobility, conductivity and transparency, by substituting for oxygen. Certain organic fluorine compounds have been found to be very effective fluorine dopants for these CVD reactions, yielding films with very shallow donors having nearly 100 % electrical activity.

Precursors for the CVD of alkaline earth metal oxides, particularly barium, lack the volatility and stability needed for reproducible deposition of superconducting, ferroelectric or magnetic oxides. Use of ammonia or volatile amines as carrier gases greatly enhances the volatility and stability of betadiketonates of barium, strontium and calcium, providing high and stable transport rates for source temperatures below 100 C, even for non-fluorinated ligands.
Electron Microscopical Observations of Graphite in Cast Irons
Authors: Purdy Gary R. , Audier Marc
Published: March 2011

Graphite flakes and spheroids, extracted from rare-earth treated cast irons, have been examined using electron microscopy. Transmission microscopy has been used to investigate the defect structure of flakes and to demonstrate the concentric aromatic shell structure of spheroids. Each spheroid is shown to possess a rare-earth containing core or nucleus.

High resolution lattice images are presented as evidence for the presence of amorphous regions within flake graphite crystals. For spheroidal graphite, the lattice images indicate a greater degree of crystalline perfection. In addition, they suggest:

1) The presence of intercalation structures

2) The presence of an amorphous phase, on the graphite-iron interface, from which crystalline graphite forms at growth sites.

The implications for possible mechanisms of graphite crystallization are discussed.
Contributions to the Study of the Solidification Mechanism and of the Influence of Structure on the Properties of Compacted/Vermicular Graphite Cast Iron
Authors: Riposan I. , Chisamera M. , Sofroni L. , Brabie V.
Published: March 2011

In the paper we have analysed some aspects of the structural,mechanical, technological and casting properties of compacted/vermicular graphite(C/VG)cast iron,with reference to our works published in the past 10 years.As regards the primary structure(eutectic solidification)we were interested in the composition and growth conditions of eutectic cells, of C/VG formation,on the basis of Mg and Si distribution,of intergranular phases,in different cooling conditions.We have also analysed the carbide formation and the inverse chill tendency. C/VG is characterised by form factors(compactness)on whose basis we propose some new typical graphite forms. The tendency to ferritic shells formation in the case of C/VG is compared with that recorded for NG,coral graphite,and FG type A,B,D. We note the possibility of favouring pearlite Dy thermal treatment,alloying and the use of a treatment-alloy with Al,Ti and other elements with a pearlitic action.We have also analysed the influence of wall thickness,cross-section geometry,holding time,anti- spheroidizing elements,nature of casting mould upon structure.Finally,we present a synthesis of the applicational properties,based on our data.
A Study of the Shrinkage and Dilatation during Solidification of Nodular Cast Iron - its Relation to the Morphology of Crystallisation
Authors: Hummer R.
Published: March 2011

This study deals with the solidification behaviour of cast iron with nodular graphite. By measurement of the “apparent shrinkage” the real feeding requirement can be determined under operating conditions. By means of cooling curves and measurements of dilatation the mode of solidification is established. The results are in accordance with today's knowledge of the morphology of crystallisation and offer an operating hypothesis for feeding technique in practice.
Formation of Internal Defects in S.G. Cast Irons in Relation to the Solidification Process
Authors: Lesoult G. , Dietrich P. , Arnould F. , Theret J. M.
Published: March 2011

It is well known that ductile iron is more prone to the formation of internal defects and to the swelling-out of the mold than grey iron. This is likely related to differences in the way the volume changes due to solidification and graphitization occur for these two cast irons. Direct study of these phenomena is difficult because interdendritic feeding and graphite expansion are intimately related.

A simple physical model is proposed to simulate the effects of a few variables on the tendency for a S.G. cast iron to lead to a casting with internal defects: its chemical composition, inoculation and the rate of heat extraction.

The aim of the model is to calculate the pressure of the residual liquid at any point of the casting during its solidification. A special attention is payed to the pressure drop due to the movement of the residual liquid in the mushy zone. Therefore the evolution of the fractions of liquid, austenite and graphite are taken into account for calculating the local volume changes which are assumed to be the main driving forces for the liquid flow. In the same time, the evolution of the permeability of the mushy zone is estimated for calculating the liquid flow pattern and the pressure drop pattern.

The numerical values for the quantities which describe the solidification of the cast iron are issued from quantitative image analysis of samples quenched during directional solidification (Q.D.S.).
Solidification Behavior of Technical Metastable Near-Eutectic Iron-Carbon Alloys (Experimental and Numerical Simulation)
Authors: Wolf G. , Flender E. , Sahm P. R.
Published: March 2011

By way of unidirectional solidification, the critical parameters of the transition from a metastable to a stable eutectic in technical cast-iron alloys were investigated. A critical growth rate which was determined for near-eutectic alloys can be attributed to the stable-to-metastable transition. The structural parameters for the metastable eutectic were defined as a function of the growth rates.
Reducing Size Effect of Grahite in Malleable iron by Prestressing before Heat Treatment
Authors: Plenard Elisabeth , Fromont Claude
Published: March 2011

The present article aims to show that high intensity compressive prestressing applied to white iron to be malleabilized, alters the final structure of the iron after malleabilization. The graphite nodules are finer and more numerous and ferritisation is greater. The phenomenon increases, with several factors as follows: intensity, repetitionmultiaxiality of prestress and hot prestressing.

Initial results of the study of correlations between finer graphite structure and certain mechanical properties show that there is little change to static properties, but some dynamic properties are improved (1).
First Stage Graphitization of Subcritically Treated White Cast Iron
Authors: Hussein A. A. , El-Menawati L. I. , Kassem M. A. , Yostos B. I.
Published: March 2011

The kinetics of first stage graphitization was studied in white cast irons of different compositions. These irons were presubjected to various isothermal anneals at 300–500°C, after being step-quenched from the intercritical (austenite and carbide) region. As a consequence of such pretreatment, the kinetics of post first stage graphitization were substantially accelerated. Both light and scanning electron metallography hive indicated that such acceleration arises due to the creation of vast areas of austenite/carbide interfaces upon cooling to and during subcritical transformations. These interfaces act as favourable nucleation sites for graphite and additionally they provide shorter diffusion paths for carbon. The latter also allows faster growth of graphite nodules. Effects of varying Si and Hn contents of the cast iron were determined. The practical significance of such treatment in providing] faster malleabilization and uniform distribution of graphite nodules is thus evident.
Effects of Nickel substitution by Manganese in Austenitic S.G. Cast Iron for Low-Temperature Uses
Authors: Poyet P. , Couchinave P. , Dancoisne P. I.
Published: March 2011

For an economical purpose, an austenitic spheroidal graphite cast iron grade, containinq nickel-manganese, has been developed to replace Ni-Resist cast iron, type D2M, for cryogenic applications.

Several tests were carried out to produce semi-industrial. heats of 200 kg so as to cast samples with a thickness ranging between 25 and 75 mm, and a variable nickel and manganese content. The resulting grades were compared each other and with Ni-Resist cast irons, before and after heat treatment, for their metallographic structure, their hardness, their mechanical tensile properties at room temperature and their impact values at temperatures down to - 150° C.

The results show that it is possible to produce cast iron grades with 7 to 10 % manganese and 9 to 11 % nickel contents, featuring, at quenched state, better mechanical tensile properties at room temperature than Ni- Resist D2M with a 22–25 % Ni content, for roughly equivalent impact values at low temperatures. For as-cast material, the properties obtained vary with material thickness, and ductility is steeply decreasing for thicknesses under 30 mm.

Weldability of Ni/Mn cast iron can be compared to Ni-Resist D2M weldability; machinability however seems more difficult, especially when boring quenched material.

Generally speaking, the overall properties of these new grades and their lower cost-price if compared to Ni-Resist cast iron, should lead to promising outlets for low temperature uses and/or applications requiring high-level mechanical properties.
The Spherulitic Growth of Graphite
Authors: Minkoff I.
Published: March 2011

The spherulitic growth of graphite from the melt is described in terms of instability mechanisms. Initially a pyramidal form grows which becomes unstable on the bounding face and a stellar polyhedral form results. The number of polyhedral facets increases in growth and the polyhedral apex angle decreases with the decrease of undercooling due to recalescence. Finally a rounded spherical form is produced.

The observations are taken from different experimental programmes, and from observations reported in the literature. Some comparison is also made with the behaviour of silicon under similar growth conditions.
A Study of Austempered Ductile Cast Iron
Authors: Verhoeven J. D. , Nagar A. El , Sarnagawa B. El , Cornwell D. P. , Laabs F.
Published: March 2011

Experiments were carried out on unalloyed ductile cast iron to evaluate the % retained austenite (%RY) and its lattice parameter as a function of austenitizing time and temperature for austempering temperatures ranging from 270 to 420°C. Results are related to expected carbon levels in the gamma iron matrix at the austenitizing temperature. It is shown that the rate of austenitization can be described as a two step process and experiments demonstrate that 900°C austenitizatlon is complete after 8m. An 1100°C homogenizatdon has been shown to have a small effect upon %RY and rate of austenitization.
Graphite Morphology Control in Cast Iron
Authors: Subramanian S. V. , Kay D. A. R. , Purdy G. R.
Published: March 2011

Graphite morphology in cast iron is analyzed in terms of the growth kinetics of graphite crystals in liquid iron. At small driving forces, i.e., low supersaturation or small kinetic undercooling, graphite growth is characterized by faceted growth, resulting in flake, compacted and spherulitic graphite morphologies. However, at large driving forces, there is a transition from facted to non-faceted growth, resulting in a dendritic growth morphology.

Flake morphology is rationalized in terms of impurity dependent crystal growth mechanisms, whereas a spherulitic morphology is attributed to a defect controlled spiral growth mechanism. Compacted graphite morphology is considered as a transition between flake and spherulitic morphology.

A thermodynamic approach is used to inter-relate the residual concentrations of impurities of technological interest, i.e. S and 0, as a function of the residual concentration of the reactive elements, Mg, Ca, and Ce in a typical cast iron melt at 1500'C and atmospheric pressure. Such a diagram that quantitatively relates graphite morphology in thick cast iron sections to soluble concentrations of impurities is referred to as a graphite morphology control diagram.

In thin section castings that freeze at faster cooling rates and large kinetic undercoolings, the basal spiral growth mechanism dominates over the impurity controlled prism growth mechanism, leading to deviations from predictions based simply on the graphite morphology control diagram. In the ase of compacted graphite, where growth on both the prism and basal faces is involved, the degree of nodularity increases with the cooling rate, giving rise to section sensitivity.

At large undercoolings, the prevention of the nucleation and growth of cementite is an essential feature of graphite morphology control. It is estimated that the mobility of the cementite interface exceeds that of the prism interface in flake graphite growth by an order of magnitude and that of the basal interface in spherulitic graphite growth by three orders of magnitude. In practice, the driving force for graphite growth is raised selectively through the addition of graphite stabilizing elements, such as silicon, which raise the temperature of the graphite eutectic and depress the temperature of the carbide eutectic. Kinetic growth undercooling can be decreased by increasing the number of heterogeneous nuclei for graphite growth through inoculation. The application of the above concepts for the control of graphite morphology in shaped automotive castings is discussed.