bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carbon Incorporation in Metal Organic Vapor Phase Epitaxy Grown Gaas Using chyX1-y, TMG, and ASH3
Authors: Kuech T.F. , Buchan N.I. , Scilla G. , Cardone F. , Potemski R. 
Published: March 2011

ABSTRACTThe unintentional and intentional incorporation of carbon has been investigated in order to understand both the growth kinetics as well as develop new and useful carbon doping sources. We present in this study a systematic investigation of the use of halomethanes during the MOVPE based growth of GaAs. We have used 13C tagged trimethyl gallium, AsH3, together with non-isotopically tagged halomethane sources, in order to determine the source and mechanism of the carbon incorporation. The carbon concentration was determined by secondary ion mass spectroscopy (SIMS). The carbon incorporation in the unintentionally doped material is compared to that obtained with the series of halomethanes, CHxI4-x (x=0,2-4), the chlorine analogs, CHC13 and CCI4, and the bromine containing compounds, CHBr3 and CBr4 which are used to intentionally introduce carbon in the epitaxial GaAs. The incorporation of carbon is studied here as a function of the halogen/H ratio in the source material and on the halogen ligand on the carbon nucleus. The standard growth parameters of susceptor temperature and gas phase composition were varied in order to discern the useful growth parameter regimes for these compounds.
Design and Characteristics of a Novel Close-Spaced Reactor for Organometallic Epitaxy
Authors: Chinoy P.B. , Ghandhi S.K. 
Published: March 2011

ABSTRACTA novel, close-spaced, inverted, stagnation flow, organometallic vapor phase epitaxy (OMVPE) reactor has been designed and fabricated for achieving high deposition efficiency and good large-area uniformity for solar cell applications. A computer model for this reactor, which is based on the conservation of mass, momentum, energy and species equations, has been used for predicting its operating characteristics. Due to the close spacing between the nozzle and susceptor, extensive measurements of the nozzle temperature were carried out for different reactor conditions and compared with simulation results. The maximum nozzle temperature was about 110°C showing the feasibility of GaAs growth from trimethylgallium and arsine. GaAs epitaxial layers were grown at different susceptor-nozzle distances, gas flow rates, reactor pressures and susceptor temperatures. The morphology, electrical properties and thickness uniformity of the layers were found to be of an acceptable quality. The measured and computed deposition efficiencies were found to be independent of reactor pressure and increasing with decreasing gas flow rates. The highest gallium deposition efficiency achieved was about 42%.
Surface Chemistry of Te-RICH CdTe
Authors: Zinck J.J. , Brewer P.D. , Olson G.L. 
Published: March 2011

ABSTRACTA study of the changes in surface structure and composition of CdTe(100) irradiated by 248 nm excimer laser radiation in the fluence range 18-75 mJ/cm2 is presented. Material is removed from the CdTe surface at all fluences, but above a threshold fluence of 40 mJ/cm2 the surface becomes Te-rich. Reflection high energy electron diffraction measurements indicate that the original 2×1 surface reconstruction is converted to a 1×1 pattern at fluences < 40 mJ/cm2. At exposures which generate a Te-rich surface a RHEED pattern is not observed. Temperature programmed desorption experiments show that weakly bound Tex exists on the surface after exposure at all fluences used in this study. A correlation of Auger data, desorption lineshapes, and model calculations suggest that the excess Te forms three dimensional islands on the surface.
Limitation of Selective Epitaxial Growth Conditions in Gas Source MBE Using Si2H6
Authors: Sakai Junro , Aketagawa Ken-Ichi , Tatsumi Toru 
Published: March 2011

ABSTRACTLow temperature and high growth rate selective epitaxial growth (SEG) on Si02 patterned Si (001) substrate in gas-source molecular-beam epitaxy (GS-MBE) using pure Si2H6 has been investigated by RHEED observation. In the temperature range of 550 to 850°C, SEG was completely obtained at an initial growth stage. Limiting conditions of SEG were closely related with critical volume of supply gas that was equal to the total amount molecules supplied on SiO2 surface during the incubation period of initial growth. The surface SiO2 was induced to evaporate with Si2H6 supplied above 800°C, so that thermal cleaning temperature for removing native oxide came down to 800°C. As a result, the maximum process temperature of Si SEG now became 800°C, and its growth rate reached as high as 645A/min at growth temperature of 700°C.
Ftir Studies of Water and Ammonia Decomposition on Silicon Surfaces
Authors: Dillon A.C. , Gupta P. , Robinson M.B. , Bracker A.S. , George S.M. 
Published: March 2011

ABSTRACTFourier transform infrared (FTIR) transmission spectroscopy. was used to monitor the decomposition of H2O (D2O) and NH3(ND3) on silicon surfaces. Experiments were performed in-situ in an ultra-high vacuum (UHV) chamber using high surface area poroussilicon samples. The FTIR spectra revealed that H2O dissociates upon adsorption at 300K to form SiH and SiNH2 surface species. NH3 also issociates upon adsorption at 300 K to form SiH and SiOH2 species. Silicon samples with saturation exposures of H2O and NH3 were progressively annealed from 300 K to 860 K. The FTIR spectra of an H2O-saturated silicon surface revealed that the SiOH species decomposed to form a silicon oxide species and additional surface hydrogen between 460 K and 580 K. Likewise, the SiNH2 species decomposed between 540 K and 660 K to produce silicon nitride and additional surface hydrogen. In both cases, the Sill surface species decreased as H2 desorption from the silicon surface was observed above 700 K.
High Pressure Oxidation of Strained Si1−xGe Alloys
Authors: Caragianis Christine , Paine David C. , Roberts Carson B. , Crisman Everett 
Published: March 2011

ABSTRACTThermal passivation of Si1−x Gex using high pressure (10,000 psi) oxidation was studied. Alloys of Si1−xGex (with x=5.4, 11.6, and 17 at. %) approximately 200 nm thick were oxidized using two processes: (i) dry oxygen at 10,000 psi at a temperature of 550°C and (ii) conventional, 1 atm steam at 800°C. The wet oxidation conditions were chosen to produce an oxide thickness comparable (=100 nm for xGe=11.6 at. %) to that obtained during high pressure oxidation at 550°C. Auger sputter depth profiling (AES), X-ray photoelectron spectroscopy (XPS), and cross-sectional transmission electron microscopy (TEM) were used to characterize the as-grown oxides. XPS studies reveal that high pressure oxides formed from all three of the alloys of Si1−xGex have greatly enhanced incorporation of Ge compared to those grown to a similar thickness under wet atmospheric conditions. We report that a significant benefit of this increase in Ge incorporation is the minimization of Ge enrichment near the oxide/Si1−xGex interface. Cross-sectional TEM images reveal a 30 nm thick Ge-rich band at the wet oxide/alloy interface and a dramatically thinner band (<5 nm) present at the oxide/alloy interface produced by high pressure oxidation. For the atmospheric oxidation samples, interfacial misfit dislocations were observed at the alloy/substrate interface indicating that the film relaxed during oxidation. In contrast, the high pressure samples showed no interfacial defects after oxidation.
Open Circuit Repair Using Thermal Exchange Deposition of Copper
Authors: Gutfeld R. J. Von , Vigliotti D. R. 
Published: March 2011

ABSTRACTWe describe a two step method that uses thermally driven exchange plating to repair open copper circuits with local heating produced by ac Joule losses. The first step utilizes a non-acid copper sulfate solution to grow copper dendrites across the open circuit. This electrical “bridge” is then strengthened using additional plate-up in acid copper sulfate.
Kinetics of Localized Laser-Photochemical Deposition
Authors: Ward Timothy L. , Kodas Toivo T. , Jackson Robert L 
Published: March 2011

ABSTRACTHighly localized metal deposits can be produced at low temperature by direct writing using a focused laser beam to induce photodissociation of gaseous organometallic precursors. The deposition rate and localization of the deposit are influenced by the kinetics of photochemical reaction and transport of reactants and products. Two-dimensional finite-element computations were performed to determine the effect of deposition parameters, such as laser power, precursor concentration, system pressure, and sticking coefficient, on deposition rates and deposit profiles resulting from single-photon gas-phase dissociation of organometallic precursors. The effect of various gas-phase transport regimes and the conditions and importance of reactant depletion have been investigated. Numerical results have also been compared to theoretical and experimental results from the literature.
In Situ Diagnostics Of Epitaxial Growth Using Reflectance-Difference
Authors: Samuelson Lars , JÖnsson Jan , Paulsson Gert 
Published: March 2011

ABSTRACTOptical in situ methods are becoming of increasing importance for studies of the mechanisms of growth and for real-time control of surface processes involved in epitaxial growth. We present data from studies, using the reflectance-difference (RD) method, of different processes related to epitaxial growth of GaAs (001) from arsine (AsH3) and from triethylgallium (TEG). RD studies make it possible to follow how the near-equilibrium, Ga-rich, configuration of the GaAs (001) surface changes with temperature and we show how the transformation to this state can be followed from As-saturated as well as from Ga-saturated surfaces. From the initial slope of the RD-transient, corresponding to the AsH3 reaction with a Ga-stabilized surface, the temperature dependence of the catalytic effect of this surface on the decomposition of arsine is measured. Of special significance for an atomic layer epitaxial process (ALE) is the demonstration of a self-limiting reaction of TEG. This process can be followed as the surface modifies itself from a state obtained by exposure to excess TEG to the near-equilibrium Ga-terminated reconstruction. Finally, we demonstrate how pulsing sequences for the realization of ALE can be followed and controlled in real time using RD as a diagnostic tool.
The LPCVD of Silicon Nitride Films from Alkylazidosilanes
Authors: Roberts David A. , Hochberg Arthur K. , O'Meara David L. , Rusnak Felicia , Hockenhull Herman 
Published: March 2011

ABSTRACTThe series of azidosilanes, SiEtn(N3)4-n where n = 1,2,3 and Si(t-butyl)(N3)3 were evaluated for the LPCVD of silicon nitride thin films. Both SiEt(N3)3 and Si(t-butyl)(N3)3 gave deposition rates of approximately 100 Å/min at temperatures of 450–500°C but films appear to be porous and air sensitive. Film properties improved as deposition temperatures were increased to 600°C. The polyazides must be handled with extreme caution. An unexplained detonation of one sample of SiEt(N3)3 occurred during the course of this study.
The Deposition of Borophosphosilicate Glass Films by LPCVD Using 2,4,6,8 Tetramethylcyclotetrasiloxane
Authors: O'Meara David L. , Hochberg Arthur K. 
Published: March 2011

ABSTRACTBorophosphosilicate glass (BPSG) films used in integrated circuit processing are grown from combinations of toxic and pyrophoric silane, diborane, and phosphine at atmospheric and reduced pressures. A safe, alternative chemical system has been developed with liquid source replacements for each dangerous gas. 2,4,6,8 tetramethylcyclotetrasiloxane (TMCTS) and oxygen are used as the silicon oxide sources, and trimethylphosphite (TMP) and trimethylborate (TMB) are the phosphorous and boron sources, respectively. Films grown in a hot wall LPCVD reactor with standard diffusion boats have thickness uniformities of ± 2 % and doping uniformities < ± 5 %.
Kinetics of the Icosahedral -to- Approximant Transformation in Al-Cu-Fe
Authors: Hayzelden Clive , Spaepen Frans 
Published: March 2011

AbstractThe kinetics of an icosahedral to approximant phase transformation were investigated in cast alloys in the composition range Al(63.65)Cu(20–25)Fe(12–15). Perfect icosahedral crystals are stable in the temperature range below the peritectic melting temperature and above approximately 700°C, below which they transform to a textured polycrystalline mixture of small microcrystals of an icosahedral approximant. The transformation is isocompositional and does not appear to occur by nucleation and growth. The kinetics of the transformation under continuous cooling and isothermal conditions were investigated using conventional and high resolution electron microscopy. The transformation is reversible, takes place over a range of compositions, temperatures and times and results in distinctive strain contrast in the electron microscope.
Composition Dependence of Solid-State Amorphization Kinetics
Authors: Boyer W. S. L. , Atzmon M. 
Published: March 2011

AbstractSolid-state amorphization rates have been measured for amorphous Ni1-cMc in contact with the crystalline terminal phase M, (M=Hf or Zr). The interdiffusion coefficient Dis found to depend on the composition of the amorphous phase, with higher Ni content resulting in a higher Dover the composition range Ni67Hf33 to Ni47Hf53. The common tangent composition at which the amorphous alloy is in metastable equilibrium with the terminal crystalline phase is found to be greater than 70 at.% Hf, which is considerably higher than previously reported values. This discrepancy is explained in terms of the interdiffusion coefficient's variation with composition.
The Annealing Induced Solid State Transformation of Quenched Beta Cr-Ti
Authors: Sinkler W. , Luzzi D. E. 
Published: March 2011

AbstractMicrostructural changes in the bcc-based water-quenched alloy β Cr40Ti60 have been investigated as a function of annealing time at 873 K. The as-quenched structure has been found to contain a non-ideal form of the ω structure, which has been detected and characterized on the basis of diffuse scattering to which it gives rise in electron diffraction patterns. Annealing at 873 K results initially in platelet precipitates of the metastable β″ phase, which is found to posses a bulk body centered tetragonal structure in which chemical ordering has been detected via electron diffraction and high resolution microscopy. After several hours of annealing at 873 K the equilibrium phases α-Ti and the C15 Laves phase Cr2Ti form as spherical polycrystalline aggregates. No evidence is found of reported annealing-induced amorphization [1]. It is suggested that amorphization cannot occur in this alloy via thermal activation, and that the reported findings may have resulted from impure specimens.
Kinetics of Glass Formation by Solidification and Melting
Authors: Fecht Hans J. 
Published: March 2011

AbstractA scenario has been developed combining the glass transition (liquid to glass) with the crystal-to glass transition. If the “melting” point of a crystalline solid solution is reduced to the ideal glass transition temperature a triple point is predicted between crystal, liquid and glass. Based on extrapolations of measured specific heat data of undercooled liquid glass-forming Au- Pb-Sb alloys the excess entropy is found to vanish close to the glass transition. On the other hand, the amorphization reaction of crystalline Fe2Er-hydrides is characterized by a lambda-type anomaly in the specific heat. The logarithmic temperature-dependence of the specific heat results from local fluctuations in the crystalline phase, rather than thermally activated lattice defects. These results suggest that glass formation from the liquid as well as the crystalline state is characterized by an underlying instability.
Melting Velocity Measurements in Silicon
Authors: Homan B.E. , Macdonald C.A. 
Published: March 2011

AbstractMelting velocities in silicon were measured on a picosecond time scale by employing pump-probe and self-reflectivity measurements. The pump laser was a 40 picosecond XeCl excimer (308 am) and the probe a dye laser at 600 am. Samples were phosphorous doped silicon wafers. Average melt-in velocities as high as 800 m/s were observed. Best fit to the data was achieved with an asymmetric transient state theory model.
Rapid-Quenching Investigation of the Nb-Pd-Ge System
Authors: Krill C. E. , Johnson W. L. 
Published: March 2011

AbstractThe structure of rapidly quenched Nb100-x-yPdxGey alloys has been investigated using x-ray diffraction. Niobium concentrations were varied between 100 and 45 at.% the remainder at each Nb concentration was composed of Pd and up to y = 15 at.% Ge. Germanium was found to suppress the nucleation rate of the fcc α-NbPd phase relative to that of the bcc α-Nb phase, thereby extending the single-phase bcc solubility range by ≈ 2 at.% Nb. High Ge content (y > 6) also induced quenching of the amorphous phase. These results can be understood from the standpoint of classical nucleation theory and from a consideration of the polymorphic phase diagram of Nb-Pd. The two approaches are consistent with Ge addition depressing the To line of the fcc phase more rapidly than it depresses the To line of the bcc phase.
Interface Stability During Rapid Directional Solidification
Authors: Hoglund David E. , Aziz Michael J. 
Published: March 2011

AbstractAt the solidification velocities observed during pulsed laser annealing, the planar interface between solid and liquid is stabilized by capillarity and nonequilibrium effects such as solute trapping. We used Rutherford backscattering and electron microscopy to determine the nonequilibrium partition coefficient and critical concentration for breakdown of the planar interface as a function of interface velocity for Sn-implanted silicon. This allows us to test the applicability of the Mullins- Sekerka stability theory to interfaces not in local equilibrium and to test the Coriell-Sekerka and other theories for oscillatory instabilities.
Solute Trapping of Ge in Al
Authors: Smith Patrick M. , West Jeffrey A. , Aziz Michael J. 
Published: March 2011

AbstractPartitioning during rapid solidification of dilute Al-Ge alloys has been investigated. Implanted thin films of Al have been pulsed-laser melted to obtain solidification at velocities in the range of 0.01 m/s to 3.3 m/s, as measured by the transient conductance technique. Previous and subsequent Rutherford Backscattering depth profiling of the Ge solute in the Al alloys has been used to determine the nonequilibrium partition coefficient k. A significant degree of lateral film growth during solidification confines determination of k to the placing of an upper bound of 0.22 on k for solidification velocities in this range. We place a lower limit of 10m/s on the “diffusive velocity,” which locates the transition from solute paritioning to solute trapping in the Continuous Growth Model.
Calculation and Simulation of Interdiffusion Coefficients and Ordering Kinetics in Binary Alloys.
Authors: Atzmon M. 
Published: March 2011

AbstractRate equations for thermally activated atomic exchange were used to calculate chemical diffusion coefficients for an initially disordered simple-cubic lattice and for a body-centered lattice with equilibrium long-range order. The results show that the chemical enhancement as a function of the enthalpy of mixing saturates, in contrast with results of conventional mean-field theories. Simulations in a disordered alloy agree with the calculations. The existence of longrange order is shown to increase the apparent activation energy for diffusion. The present theory is also shown to provide a simple method of calculating ordering kinetics and equilibrium longrange order, and good agreement with previous experiments and simulations is achieved.
Molecular Dynamics Study of the Elastic Response of Crystalline, Amorphous and Chemically Disordered NiZr2
Authors: Massobrio Carlo , Rosato Vittorio , Willaime Francois 
Published: March 2011

AbstractWe calculate the shear elastic constants of the alloy NiZr2 by molecular dynamics simulations in the crystalline and amorphous phases as well as upon introduction of antisite defects in the crystal at T=300K. For S (long range order parameter) equal to 0.5, the system is amorphous and C' is larger than the same quantity relative to the crystal whereas C44 and C66 are smaller.
A Comparison of Semiconductor Models for the Study of Liquid Phase Epitaxy
Authors: Cook Stephen J. , Clancy Paulette 
Published: March 2011

AbstractThe phase behavior of silicon is studied using the Modified Embedded Atom Method (MEAM) proposed by Baskes, Nelson and Wright. We find this model to quantitatively reproduce aspects of both the solid and liquid phases with an accuracy comparable to the widely-used Stillinger-Weber (SW) potential, thus providing an opportunity to examine the consistency of results obtained previously using the SW model. Although the models are very different, they both produce solid-liquid interfaces on both silicon (100) and (111) which have very similar morphologies. We find that the MEAM predicts the melting point of silicon to be 1445K, or 14% lower than the experimental value. The model also predicts the heat of melting to be 34.9 kJ/mol, 45% lower than the experimental value of 50.6 kJ/mol, and a liquid density which is 5.4% larger than that of the solid at the melting point, which is the density ratio found by experiment. The liquid density is found to be too low with respect to experiment. We also suggest a correction which might be applied to the MEAM model to improve its description of the liquid phase.
Asymmetric Membrane Formation in the Heterogeneous Polymerization of Methyl Methacrylate
Authors: Mikos Antonios G. , Kiparissides Costas 
Published: March 2011

AbstractA mathematical model is presented to describe the fundamental phenomena occurring in the vicinity of the interface between a polymerizing medium and a non-solvent. The model combines the principles of polymerization kinetics, mass transfer and polymer solution thermodynamics and is applied to the polymerization of methyl methacrylate with water. Numerical simulations indicate the development of large interface velocities and the formation of a dense polymer skin at very low monomer conversions in agreement with experimental observations.
Epitaxy and Nucleation in Cu and Ag Doped Amorphous Si
Authors: Custer J. S. , Thompson Michael O. , Eaglesham D. J. , Jacobson D. C. , Poate J. M. , Liefting J. R. , Saris F. W. 
Published: March 2011

AbstractThe competition between solid phase epitaxy and random nucleation during thermal annealing of amorphous Si implanted with the fast diffusers Cu and Ag has been studied. For low concentrations of these impurities, solid phase epitaxy proceeds with small deviations from the intrinsic rate and with the impurity remaining in the shrinking amorphous layer. At a critical metal concentration in the amorphous layer of ∼ 0.12 at.% rapid random nucleation occurs, halting epitaxy and transforming the remaining amorphous material to polycrystalline Si via grain growth. The nucleation rate is at least 8 orders of magnitude greater than the intrinsic homogeneous rate. At higher Cu concentrations nucleation is observed below the temperature needed for epitaxy (400°C). This nucleation, clearly caused by the presence of Cu or Ag in the layer, may be induced by the impurities exceeding the absolute stability concentration and starting to phase separate, leading to enhanced crystal Si nucleation in the metal rich regions.