bluuebunny/crossref_metadata_2025_split huggingface dataset:
New Zinc-bis(Dialkylamides) Potentially Usable as Site-Selective Dopants For p-Type ZnSe.
Authors: Rees William S. , Just Oliver 
Published: March 2011

AbstractIn earlier work, the effective utilization of Zn {N\Si(CH3)3]2}2 as a site-selective dopant for the production of p-type ZnSe by OMVPE was demonstrated. Several new zinc-bis(dialkylamides) of the general form (R)(R′)NZnN(R″)(R‴) now have been prepared. They have been characterized by 1H- and 13C-NMR, GC/MS and elemental analysis. Vapor pressures and gas phase decompositior profiles have been examined. Correlations of vapor pressure and structure are discussed for this series of compounds. A mechanism for the site-selectivity observed in the incorporation of nitrogen is proposed.
Nanosecond and Femtosecond UV Laser Ablation of CdTe (100): Time-Of-Flight and Angular Distributions
Authors: Brewer P.D. , Späth M. , Stuke M. 
Published: March 2011

AbstractAngularly resolved time-of-flight (TOF) measurements have been used to probe the velocity and angular distributions of Cd atoms and Te2 molecules ejected from CdTe (100) substrates under irradiation by 248 nm nanosecond and sub-picosecond laser pulses. These experiments employ a dye laser TOF mass spectrometer with resonance enhanced multiphoton ionization for sensitive, high resolution detection of the desorbed products. The velocity distributions are well described by Maxwell-Boltzmann distributions for low fluence nanosecond (<60 mJ/cm2) and sub-picosecond (<3.3 mJ/cm2) pulses. Angular flux distributions for nanosecond irradiation are observed to be highly forward peaked about the surface normal, whereas, for sub-picosecond irradiation the distribution approaches cos3θ.
Gas-Phase Silicon Atom Densities in the Chemical Vapor Deposition of Silicon from Silane
Authors: Coltrin Michael E. , Breiland William G. , Ho Pauline 
Published: March 2011

AbstractSilicon atom number density profiles have been measured using laser-induced fluorescence during the chemical vapor deposition of silicon from silane. Measurements were obtained in a rotating-disk reactor as a function of silane partial pressure and the amount of hydrogen added to the carrier gas. Absolute number densities were obtained using an atomic absorption technique. Results were compared with calculated density profiles from a model of the coupled fluid flow, gas-phase and surface chemistry for an infinite-radius rotating disk. An analysis of the reaction mechanism showed that the unimolecular decomposition of SiH2 is not the dominant source of Si atoms. Profile shapes and positions, and all experimental trends are well matched by the calculations. However, the calculated number density is up to 100 times smaller than measured.
The Effects of Deposition Parameters on the Properties of SiO2 Films Deposited by Microwave Ecr Plasmas
Authors: Chau T. T. , Lam P. M. , Kao K. C. 
Published: March 2011

AbstractElectronic and physical properties of SiO2 films deposited by microwave ECR plasmas of the mixtures of SiH4 and N2O have been measured as functions of the pressure and the gas-flow ratio of N2O to SiH4 gases in the processing chamber. Experimental results show that the film deposition rate increases with increasing SiH4 concentration, that is, with decreasing gas-flow ratio. The films deposited at N2O/SiH4 gas-flow ratios smaller than 10 tend to have a refractive index higher than the thermally grown oxide. However, for the N2O/SiH4 gas-flow ratios between 10 and 20, the films have the refractive index close to that of thermally grown oxide, which is about 1.45-1.46. The film deposition rate increases linearly with increasing pressure. In general, the films deposited at high pressures (>100 mTorr) have a higher refractive index as compared with the thermally grown oxide; also films deposited at high pressures have more electron traps. Good quality SiO2 films can be deposited at pressures with the range of 20 -50 mTorr and the N2O/SiH4 gas-flow ratio of 10.
High Rate Deposition of SiO2 by the Remote Pecvd Technique
Authors: Ishida Arichika , Hiramatsu Masato , Kawakyu Yoshito 
Published: March 2011

AbstractThe deposition of SiO2 by remote PECVD using microwave activated oxygen species and SiH4 were examined. The deposition rate has been found to be greatly enhanced by reducing the distance between the substrate surface and the end of the supplying nozzle for the plasma excited oxygen species.The deposition rate decreased with increasing substrate temperature under the condition that the activated oxygen species and SiH4 molecules collide with each other many times. Its activation energy was -0.27 eV.It has been found that the gas phase reaction caused by the collision is important to obtain high quality films. A SiO2 film with a resistivity larger than 1×1016 Ω·cm was able be obtained with high deposition rates beyond 200 nm/min, at low temperatures below 400°C. The minimum interface state density was 4.3×1010 cm−2eV−1 for a film deposited at 230 nm/min, and 2.0×1010 cm−2eV−1 for a film deposited at 30 nm/min.
New Dry-Etch Chemistries for III-V Semiconductors
Authors: Pearton S. J. , Chakrabarti U. K. , Ren F. , Abernathy C. R. , Katz A. , Hobson W. S. , Constantine C. 
Published: March 2011

AbstractFor some dry etching applications in III-V semiconductors, such as via hole formation in InP substrates, the currently used plasma chemistries have etch rates that are up to a factor of 30 too slow. We report on the development of 3 new classes of discharge chemistries, namely C12/CH4 /H2/Ar at 150°C (yielding InP etch rates of >1 μm · min−1 at 1 mTorr and –80V dc), HBr/H2 for selective etching of InGaAs over AlInAs, and iodine-based plasmas (HI/H2, CH3 I/H2) that offer rapid anisotropic etching of all III-V materials at room temperature. In all cases, Electron Cyclotron Resonance sources (either multipolar or magnetic mirror) with additional rf biasing of the sample position are utilized to obtain low damage pattern transfer processes that generally use metal contacts on device structures as self-aligned etch masks. The temperature dependence of etch rates with these new chemistries display non-Arrhenius behavior in the range 50-250°C and a detailed study of the phenomenon are reported. Electrical, optical and chemical analysis of the etched surfaces show that it is possible to achieve essentially damage-free pattern transfer.
New Damage-Less Patterning Method of A GaAs Oxide Mask and Its Application to Selective Growth by Mombe
Authors: Yoshida Seikoh , Sasaki Masahiro 
Published: March 2011

AbstractA new damage-less patterning method of the photo-oxidized GaAs mask used for the selective-area growth of GaAs has been developed. We have found a new characteristic of the GaAs oxide: a metal Ga deposition onto the GaAs oxide surface lowers the desorption temperature of the oxide. The patterning method employed is based upon this characteristic. The GaAs oxide where 15 atomic layers (ALs) of Ga is deposited is locally removed at 540°C to form an opening area in the oxide mask. After forming this opening area, GaAs is selectively grown there by metal-organic molecular beam epitaxy (MOMBE).
Pyrolytic Lcvd of Silicon Using A Pulsed Visible Laser - Experiment and Modelling
Authors: Ivanov B. , Popov C. , Shanov V. , Filipov D. 
Published: March 2011

AbstractMaskless deposition of silicon from silane on Si monocrystalline wafer using copper bromide vapor laser (CBVL) is investigated. Morphology and geometric parameters of the stripes obtained are studied and some conclusions for the process mechanism are made. Applying Kirchoff's transform and Green's function analysis nonlinear heat diffusion problem for different pulse shapes was solved. The influence of pulse shape on the temperature distribution and its time evolution was studied. Nonisothermal and non-stationary deposition kinetic models using the obtained results were developed.
Low Temperature CVD of TiN from Ti(NR2)4 and NH3: FTIR Studies of the Gas-Phase Chemical Reactions
Authors: Weiller Bruce H. 
Published: March 2011

AbstractThe gas-phase chemical reaction between Ti(NMe2)4 and NH3 is a critical step in the Metallorganic Chemical Vapor Deposition (MOCVD) of TiN at low temperatures. We have examined this reaction using a flow-tube reactor coupled to an FTIR spectrometer. A sliding injector provides control over the reaction time and the kinetics of reactive species can be measured as a function of the partial pressure of an added reagent. The disappearance of Ti(NMe2)4 was measured as a function of reaction time and NH3 pressure at 26°C. The resulting bimolecular rate constant is (1.1±0. 1) x 10-16 cm3molecules−1s−1 Dimethylamine is observed as a direct product from this reaction consistent with other studies. We have also measured the rate constant using ND3 and find a substantial isotope effect, kh/kd ≈2.4± 0.4. This indicates that H-atom transfer is involved in the rate limiting step. We show that these results can be explained by a mechanism comprised of transamination reactions with NH3.
Theoretical Modeling of Chemical Vapor Deposition of Silicon Carbide in a Hot Wall Reactor
Authors: Gao Feng , Lin Ray Y. 
Published: March 2011

AbstractA theoretical model, which describes the coupled hydrodynamics, mass transport and chemical reaction, has been developed to simulate chemical vapor deposition (CVD) of silicon carbide (SiC) from gas mixture of methyltrichlorosilane (MTS), hydrogen and argon in a hot wall reactor. In the model analysis, the governing equations were developed in the cylindrical coordinate, and solved numerically by using a finite difference method. A kinetic rate expression of CVD-SiC deposition from the gas mixture was obtained from this study. The deposition rate has an Arrhenius-type dependence on the deposition temperature and is first order with respect to the MTS concentration. Estimated activation energy is 254 kJ/mol. Predicted deposition rate profiles by the model analysis incorporated with the obtained kinetic rate expression showed excellent agreement with experimental data over a variety of applied deposition conditions.
Synthetic Strategies for MOCVD Precursors for HTcS Thin Films
Authors: Meinema Harry A. , Timmer Klaas , Linden Hans L. , Spee Carel I. M. A. 
Published: March 2011

AbstractIn recent years much attention has been given world-wide to the development of suitable MOCVD precursors for the deposition of HTcS thin films. Synthetic research has been and is concentrated on the development of superior Ba-, Sr-, Ca- and Y-precursors. Most emphasis is given to the synthesis of thermally stable volatile barium compounds. Synthetic strategies are based on encapsulating the central metal atom, by use of multidentate ligand systems and/or bulky substituents. Most attention is given to the development of thermally stable volatile ß-diketonate complexes, fluorine-free and fluorine-substituted, with auxiliary ligands. Thermally stable monomeric complexes of fluorine-substituted ß-diketonates with polyethers are by far the most volatile Ba-, Sr-, and Ca-precursors presently available. Low melting Y(thd)3.L complexes where L is 4-Et- or 4-t-Bupyridine- N-oxide can be used as liquid yttrium MOCVD precursors at temperatures above 100°C. This paper gives a survey of the trends in recent research activity and developments in these areas.
Advances in Precursor Development for CVD of Bariumcontaining Materials
Authors: Vaartstra Brian A. , Gardiner R. A. , Gordon D. C. , Ostrander R. L. , Rheingold A. L. 
Published: March 2011

AbstractBarium titanate and barium-strontium titanate (BST) are high dielectric materials, likely to replace state-of-the-art capacitor materials for memory applications. Chemical Vapor Deposition (CVD) of these materials has been hampered, particularly by the lack of suitable precursors for barium. Although attempts to make volatile metal-organic barium compounds have met with some progress, a suitably stable, volatile barium source is still in demand. This paper will highlight recent developments at ATM, including syntheses and structures of polyamine and glycol ether adducts which have been designed to limit aggregation of barium diketonates, and stabilize the adducts with respect to ligand dissociation.
Structure and Kinetics Study of MOCVD Lead Oxide (PbO) from Lead BIS-Tetramethylheptadionate (Pb(thd)2)
Authors: Hendricks Warren C. , Desu Seshu B. , Tsai Ching Yi 
Published: March 2011

AbstractLead bis-tetramethylheptadionate (Pb(thd)2) is an extremely useful precursor for the preparation of lead-based thin films such as PZT, lead titanate, etc. In this paper, lead oxide was deposited from Pb(thd)2 in a hot-walled CVD reactor using oxygen as a reactive species and diluent gas. XRD and SEM were used to determine the structure of the material deposited by the CVD process. The CVD process consistently produced the monoxide of lead which was found to consist of a mixture of orthorhombic PbO with small tetragonal PbO platelets. TEM was used to determine the orientation of the individual platelets which was found to be consistently normal to the <201> family of zone axes. Deposition rates were determined and simulated using an FEM computer model to determine the rate constants for the overall deposition process.
Liquid Delivery of Low Vapor Pressure MOCVD Precursors
Authors: Gardiner R. A. , Van buskirk P. C. , Kirlin P. S. 
Published: March 2011

AbstractA significant limitation in MOCVD processing of advanced materials is the ability to deliver low volatility precursors, in a repeatable fashion, to the deposition reactor. Apparatus for delivering low volatility precursors in gaseous form, wherein a precursor source liquid is flash vaporized at elevated temperature has been developed. Stable, reproducible delivery of liquid precursors for TiN and Ta2O5 has been demonstrated. For multicomponent ceramic material systems simultaneous delivery of multiple cation species via a single source liquid has been achieved. The effect of flash vaporization on precursors for PZT was investigated. Pb, Zr and Ti precursors were dissolved in an organic medium with a defined cation ratio. The source solution was vaporized, the precursors transported as vapor then collected and analyzed by 1H and 13C nmr. No decomposition of the precursors was observed post vaporization and source solution stoichiometry was maintained in the collected material. The use of this flash vaporization technique has already been particularly successful for MOCVD of BaTiO3, MgAl2O4, YBa2Cu3O7−x, YSZ, LaSrCoO3 and Cu metal.
Local Equilibrium Phase Diagrams for SiC Deposition in a Hot Wall LPCVD Reactor
Authors: Chiui Chien C. , Desu Seshu B. , Chen Zhi J. , Tsai Ching Yi 
Published: March 2011

AbstractThe traditional CVD phase diagrams are only valid for cold wall reactors because of the neglecting of the depletion effects in hot wall reactors. Due to the depletion effects along the reactor, the traditional CVD phase diagrams can not accurately predict the phases deposited on the substrate in a hot wall CVD system. In this paper, a new approach to calculate the local equilibrium CVD phase diagrams in a hot wall reactor is presented by combining the depletion effects with the equilibrium thermodynamic computer codes (SOLGASMIX–PV). In this study, the deposition of SiC using methyltrichlorosilane (MTS)–hydrogen (H2) was chosen to verify this new approach. The differences between the new CVD phase diagrams and the traditional phase diagrams were discussed. The calculated CVD phase diagrams were also compared with the experimental data. The single phase of SiC predicted by this approach is much better than the traditional phase diagrams. The experimental regions for depositing single phase SiC are larger than the calculated local phase diagrams because of the higher linear velocity of the gas flux under low pressure and the polarity of the Si carrying intermediate species.
Plasma-Enhanced MOCVD of Superconducting Oxides
Authors: Ebihara Kenji , Fujishima Tomoyuki , Shiga Masanobu , Jia Quanxi 
Published: March 2011

AbstractThe plasma-enhanced MOCVD is developed to prepare high-Tc oxide superconducting thin films. Plasmas generated by microwave and rf discharges decompose effectively the source materials ( β-diketonate chelates) into their elements and oxides. YBaCuO thin films were deposited on the MgO substrate of 500–650 °C at total pressure of 0.6–5 Torr with O2 contents less than 30%. The as-grown films produced by two kinds of plasma enhancement were porous and consisted of crystalline grains, but showed the superconducting transition after heating procedure at around 800 °C. It is shown that the inherent crystalline orientations of the as-grown films determine the crystal structure of the post-annealed films. The film of the metal atomic ratios of 0.91 for Ba/Y and 2.64 for Cu/Y showed the superconducting properties with Tc(zero) of 89 K and the critical current density (at 77 K) of 5×104 A/cm2. Spectroscopic analysis showed that the plasmas are composed of many excited species such as Y, Y+, Ba, Ba+, Cu, YO, BaO, CuO. Formation of the metal-oxides through the gas phase reaction is essential for the high-quality YBaCuO superconducting thin film preparation in the PEMOCVD.
Metal-Organic Chemical Vapor Deposition of Epitaxial Tl2Ba2Ca2Cu3O10−x Thin Films
Authors: Hinds Bruce J. , Schindler Jon L. , Han Bin , Neumayer Deborah A. , Degroot Donald C. , Marks Tobin J. , Kannewurf Carl. R. 
Published: March 2011

AbstractSuperconducting thin films of Tl2Ba2Ca2Cu3O10−x (TL-2223) have been grown on single crystal (110) LaAlO3 using a two-step process. Ba2Ca2Cu3Ox precursor films are deposited via metal-organic chemical vapor deposition (MOCVD) in a horizontal hot walled reactor. The second generation precursors Ba(hfa)2•tet, Ca(hfa)2•tet, and Cu(hfa)2 (hfa = hexafluoroacetylacetonate, tet = tetraglyme) were used as volatile metal sources due to their superior volatility and stability. Tl was introduced into the film via a high temperature post anneal in the presence of a Tl2O3:BaO:CaO:CuO pellet (1:2:2:3 ratio). Low O2 partial pressures were used to reduce the temperature in which the TI-2223 phase forms and to improve the surface morphology associated with a liquid phase intermediate. Films are highly oriented with the c-axis perpendicular to the substrate and a-b axis epitaxy is seen from x-ray φ- scans. The best films have a resistively measured Tc of 115K and a magnetically derived Jc of 6×105 A/cm2 (77K, 0 T). Preliminary surface resistance measurements, using parallel plate techniques, give Rs = 0.35 mΩ at 5K (ω = 10 GHz).
MOCVD of Group III Chalcogenide Compound Semiconductors
Authors: Barron Andrew R. 
Published: March 2011

AbstractA review is presented of recent advances in the metal-organic chemical vapor deposition (MOCVD) of thin films of group III-chalcogenides. The deposition of thermodynamic phases of composition ME and M2E3 (M = Ga, In; E = S, Se. Te) will be presented. Also included is a discussion of the development of molecular control over the structure of deposited films and the atmospheric pressure MOCVD growth of the high pressure phase of InS and a meta-stable cubic phase of GaS.
Nucleus of Spheroidal Graphite in Cast Iron
Authors: Kusakawa Takaji , Ogame Akito , Xu Xingcheng , Lin Hanton 
Published: March 2011

ABSTRACTThe Spheroidal Graphites in cast iron and Ni-C alloy are extracted by using chloric acid or aqua regia and clean up using hydro-fluoric acid and hot water. The spheroidal graphite is crushed down till under five micron thickness wrapped by aluminium foil. The nucleus of spheroidal graphite can be observed by electron probe micro-analyser. Magnesium, Calcium, Cerium, Oxygen, Sulphur and Silicon etc. are recognized in the nucleus of spheroidal graphite.
Computer Simulation of the Structure Formed During Solidification of Cast Iron
Authors: Fredriksson Hasse , Svensson Ingvar L. 
Published: March 2011

ABSTRACTBy combining heat extraction laws with kinetic growth laws, the solidification process of nodular, grey and white cast iron have been calculated. The risk for formation of white structure during solidification of grey and nodular cast iron was calculated. The calculations was done for different thickness of the casting as well as, as a function of the number of growing units. The fraction of white structure was also calculated.
Effect of Minor Additives on First Stage Graphitisation in White Cast Iron
Authors: Roy P. L. , Chakrabart A. K. , Banerjee P. 
Published: March 2011

ABSTRACTMinor additions (0.05-0.2 wt.%) of sodium chloride, hexachloroethane and elemental sulphur to commercial white iron melts have been found to enhance the kinetics of first stage graphitisation during subsequent annealing of white iron samples. The optimum dose of sodium chloride and hexachloroethane addition is around 0.1%. Yield strength and ductility of annealed test bars treated with NaCl or C2Cl6 compare favourably with those of untreated test bars. Sulphur treatment causes slight deterioration in mechanical properties. Fully grown nodules in both treated and untreated samples appear porous under SEM. Possible mechanisms of acceleration of graphitisation in the treated samples have been suggested.
Effect of Twin/Tilt on the Growth of Graphite
Authors: Peiyue Zhu , Rozeng Sha , Yanxiang Li 
Published: March 2011

ABSTRACTThe effect of twin/tilt initiated in the process of graphite growth making the graphite curling and change from flake to vermicular and spheroidal is discussed. With the developing of the solidification process,the modifying elements enrich in the front of solid-liquid interface, the amount of twin defects in the graphite increases,its tilt fashion changes and the graphite formed varies from flake to vermicular and spheroidal. The modifying elements promote the formation of twin/tilt. When the modifying elements are insufficient for spheroidizing,the tilt orientation of twins is changeable,and the graphite formed is twisted. When the modifying elements are sufficient enough, the tilt orientation of twins becomes singular, and the graphite formed tends to be round. According to the energy and kinetics consideration of the formation of twin/tilt boundary, it is predicted that the twin plane would firstly adopt (10Tm), especially the (10T2) plane. This result coincides well with the experimental observations. It is proposed that the formation of SG can be divided into two steps: growth of graphite nucleus into spherulite by twin/tilt mechanism and brancing on it in a spiral mode.
The Effect of Alloying Elements on the Bainiite Transformation in Ductile Iron
Authors: Stenfors Sven-Eric 
Published: March 2011

ABSTRACTThe formation of retained austenite in nodular cast iron by austenitizing and heat treating at 450 or 350 C has been studied by X-ray measurements and metallographic examination. It has thus been related to the detailed mechanism of the bainite transformation.The effects of the addition of a few tenths of a percent of Mn, Cr and Mo were examined and the effect of higher contents was estimated from literature data. Already small additions increase the maximum amount of retained austenite but larger additions are needed in order to increase the time for complete transformation substantially.A small addition of Sn which has a strong effect on the transformation to pearlite had no effect on the transformation to bainite.
Some Aspects on the Formation of the Microstructure in Multipass Welds in Ferritic Ductile Cast Iron
Authors: Hällén G. 
Published: March 2011

ABSTRACTThe microstructure obtained in the heat-affected zone (HAZ) and the carbide zone in the weld metal adjacent to HAZ has been studied in multipass welds in ferritic ductile cast iron. The effects of postweld anneal were also studied. The amount of martensite in the HAZ and the carbide zone can be reduced by the heating cycles of subsequent weld beads during multipass welding. The amount of martensite in the structure affects the graphite morphology after postweld annealing in both the HAZ and the carbide zone. It is also proposed that the graphite in the carbide zone, when arc-welding ductile cast iron with no or moderate preheat, is formed from cementite by grafitization.