bluuebunny/crossref_metadata_2025_split huggingface dataset:
Deposition of Heavily-Doped μc-Silicon Thin Films by Remote Plasma-Enhanced Chemical-Vapor Deposition Process (remote PECVD)
Authors: Wang C. , Bjorkman C.H. , Lee D.R. , Williams M.J. , Lucovsky G. 
Published: March 2011

ABSTRACTWe have succeeded in depositing both activated n- and p-type μc-Si, by a low temperature, 250°C, remote PECVD process in which dopant gases (PH3 or B2H6)/Silane (SiH4) mixtures are injected downstream from the exit port of a He/H2 plasma. The room temperature conductivities and activation energies for the n- and p-type μc-Si are respectively, 40 S/cm with Eaa=0.018 eV, and 5 S/cm with Ea =0.040 eV. Doped μc-Si is obtained for PH3/SiH4 ratios up to 1%, and for B2H6/SiH4 ratios to 0.1%. For B2H6/SiH4 ratios < 0.1%, the deposited p-type material is doped a-Si rather than doped μc-Si. We have shown that these heavily doped μc-Si film are a viable candidate for the gate electrode in MOS devices. The application of these doped μc-Si films in p-i-n diode devices has also been studied.
Effect of Plasma Modulation in the Glow Discharge Deposition of Amorphous Silicon Films
Authors: Bruno G. , Capezzuto P. , Cicala G. , Manodoro P. 
Published: March 2011

ABSTRACTThe plasma deposition of hydrogenated and fluorinated amorphous silicon (a-Si:H,F) and silicon-germanium alloys (a-Si,Ge:H,F) from SiF4-H2 and SiF 4-GeH 4-H2 mixtures, respectively, has been studied in continuous (CW) and modulated wave (MW) r.f. discharges. It has been found that the period and duty cycle of the modulated wave strongly affect the plasma composition, the surface homogeneity and the material properties. The plasma-phase characterization, performed by time resolved optical emission spectroscopy (TR-OES), supplies arguments on the origin of emitting species and on their formation kinetics. It has been found that H* and SiFx are formed by a direct electron impact process involving the same species in the ground state. In addition, the surface homogeneity and some material properties are strongly improved by plasma modulation.
Properties of in Situ Doped Amorphous and Polycrystalline Silicon Deposited by Chemical Vapor Deposition from Tertiarybutylarsine and Tertiarybutylphosph INE
Authors: Kotccki David E. , Blouse Jeffrey L. , Parks Christopher C. , Sarkozy Robcrt F. 
Published: March 2011

ABSTRACTTcrtiarybutylarsine (TBA) and tertiarybutylphosphine (TBP) were evaluated as n-type dopant precursors for low pressure chemical vapor deposition (LPCVD) of in situ doped amorphous and polycrystalline silicon from silanc. The deposition kinetics, film composition, and electrical properties obtained with TBA and TBP dopant precursors are compared to that obtained when using arsine and phosphine as dopant precursors. Compared to the hydride dopant sources, TBA and TBP provide increased safety due to their sub-atmospheric vapor pressure (≃ 200 Torr at 26°C) and lower toxicity. Using mixtures of TBA and TBP with silane and hydrogen, high quality films of arsenic and phosphorus in situ doped amorphous and polycrystalline silicon were obtained. Dopant incorporation levels ranged from 5×1019 to l.5×1021 cm−3 as measured by SIMS. The deposition rate of polycrystallinc films deposited from TBA and TBP was enhanced by a factor of-≃-3X compared to the hydride dopants for the same mole fraction of dopant precursor. The minimum resistivitics of 5.0 and 1.4 mΩ-cm were obtained, following a 1000°C, 30 second rapid thermal anneal, for ≃500Å thick films on SiO2 deposited with TBA and TBP respectively. A drawback of TBA and TBP is the incorporation of ≃1.0 atomic percent carbon which is > 15X higher than obtained when using the hydride dopant sources. Carbon was observed under all deposition conditions examined.
Adsorption and Desorption Kinetics for Chlorosilanes on Si(111) 7×7
Authors: Gupta P. , Coon P.A. , Koehler B.G. , Wise M.L. , George S.M. 
Published: March 2011

ABSTRACTThe adsorption and desorption kinetics for SiCl4 and SiCl2H2 on Si(111) 7×7 were studied using laser-induced thermal desorption (LITD) and temperature programmed desorption (TPD) techniques. Both LITD and TPD experiments monitored SiCl2 as the main desorption product at 950 K at all coverages of SiCl4 and SiCl2H2 on Si(111) 7×7.HC1 desorption at 850 K and H2 desorption at 810 K were also observed following SiCl2H2 adsorption. Isothermal LITD measurements of SiCl4 and SiCl2H2) adsorption on Si(111) 7×7 revealed that the initial reactive sticking coefficient decreased with increasing surface temperature for both molecules. The temperature-dependent sticking coefficients were consistent with precursor-mediated adsorption kinetics. Isothermal LITD studies of SiC12 desorption revealed second-order SiCl2 desorption kinetics. The desorption kinetics were characterizedby a desorption activation energy of Ed = 67 kcal/mol and a preexponential of vd = 3.2 cm2/s. TPD studies observed that the HCI desorption yield decreased relative to H2 and SiCl2 desorption as a function of surface coverage following SiCl2H2 exposure. These results indicate that when more hydrogen desorbs as H2 at higher coverages, The remaining chlorine is forced to desorb as SiCl 2.
An Investigation of in Situ Chlorination of Tungsten
Authors: Thomas N. , Blanquet E. , Vahlas C. , Bernard C. , Madar R. 
Published: March 2011

ABSTRACTA thermodynamic and experimental study of in-situ chlorination of tungsten is presented. When gaseous tungsten chlorides are used as metal precursors for tungsten and tungsten silicide CVD, their direct synthesis provide a reproductible volatile chloride source.The conditions leading to the best production of volatile tungsten chlorides have been optimized by means of thermodynamic calculations. The influence of the different production parameters (temperature, nature of reactant gas, …) have been determined.During some chlorination experiments, volatile chlorides have been detected in-situ by a quadrupole mass spectrometer.Good agreement between theoretical and experimental results is obtained.
Photoreactions in Polyalkylsilynes Induced by ArF-Laser Irradiation
Authors: Kunz R. R. , Bianconi P. A. , Horn M. W. , Smith D. A. , Freed C. A. 
Published: March 2011

ABSTRACTPhotoreactions in polyalkylsilyne thin films induced by ArFlaser (193 nm) irradiation have been examined. Photoexcitation of the σ-conjugated Si-network at 193 nm (6.42 eV) results in Si-Si bond scission and alkyl-group desorption when irradiated in a vacuum. In addition to these processes, efficient (up to 7% quantum efficiency) insertion of oxygen into the Si backbone occurs when the irradiation is performed in air, resulting in the formation of a siloxane. Both infrared and X-ray photoelectron spectroscopies indicate a higher oxygen coordination about the Si atoms in the oxidized product than observed for linear polysilanes. This higher oxygen coordination indicates a siloxane network. The polysilynes have been demonstrated as deep UV photoresists and may have additional applications as precursors for thin film or binary optical components.
Increased Volatility of Barium Metal Organics by the Use of Nitrogen Lewis Bases
Authors: Buriak Jillian M. , Cheatham Linda K. , Graham John J. , Gordon Roy G. , Barron Andrew R. 
Published: March 2011

ABSTRACTSubstituted β-diketonate complexes of barium have limited volatility even at reduced pressures. The addition of nitrogen Lewis bases to the CVD carrier gas allows barium β-diketonates, even those with no reported volatility, to be transported in the vapor phase at temperatures as low as 70°C (atmospheric pressure) with no decomposition. No increase in volatility is observed, however, for barium carboxylate complexes.
Chemical Phase Separation in Binary Iron-Chromium Alloys
Authors: Hawick K.A. , Epperson J.E. , Windsor C.G. , Rainey V.S. 
Published: March 2011

AbstractA study of chromium-enriched domain growth occurring in binary Fe-Cr alloys quenched from above to various temperatures within the miscibility gap has been made. We present kinetic sequences of in-situ small angle neutron scattering (SANS) data for ageing times up to 75 hours on alloys containing 20, 30 and 40 atomic percent chromium. The SANS measurements are compared with partial structure functions obtained from computer simulations performed on a distributed array processor (DAP). We use a pair-potential lattice model, but simulate large systems containing up to 16 million lattice sites. We find good agreement between the scaled structure factors for our SANS data and computer simulated system.
Time-Resolved X-ray Scattering Investigation of Ordering Kinetics in Fe3Ai
Authors: Park B. , Stephenson G. B. , Ludwig K. F. , Allen S. M. 
Published: March 2011

AbstractWe have investigated the kinetics of the B2/DO3 transition in Fe3AI (28 at. %) using in situ time-resolved x-ray scattering. In these experiments, the evolution of the diffuse and/or Bragg intensity near the (½ ½ ½) DO3 superlattice peak is observed after the temperature of the sample is abruptly changed. H-ere we present results for the kinetics of re-equilibration of short-range order within the disordered (B2) phase, and of short- and long-range order within the ordered (DO3) phase. The short-range order is characterized by the diffuse peak intensity IDIFFUSE and correlation length ξ;the long-range order is characterized by the Bragg intensity IBRAGG. For quenches within the disordered phase, IDIFFUSE and ξ both relax exponentially at the same rate. The temperature dependence of the relaxation time shows evidence of a divergence at the critical temperature. For shallow quenches within the ordered phase, IBRAGG, IDIFFUSE and ξ all relax exponentially, but with different rates. However, for deep quenches within the ordered phase, IDIFFUSE and ξ do not show simple exponential relaxation. Instead, coarsening of short-range order into long-range order is seen, as in quenches from the disordered phase into the ordered phase. Investigation of up-quenches and down-quenches to the same temperature within the ordered phase indicates that disordering is faster than ordering.
Kinetics of Sro and Lro in FeAl Alloys with A2 and DO3 Structures
Authors: Cadeville M.C. , Pierron-Bohnes V. , Vennegues P. , Afyouni M. , Kim T.H. 
Published: March 2011

AbstractThe kinetics of short and long-range ordering in FeAlx alloys have been investigated using resistometry. The results were obtained in the A2 solid solution (x = 0.10 and 0.17), in the DO3 ordered phase (x = 0.23, 0.27, 0.30 and 0.33) and in the A2 + DO3 two-phase region (x = 0.19). The ordering kinetics curves are well described in a classical model with a lognormal distribution of relaxation times whose center varies with the temperature according to an Arrhenius law. One thus gets the thermodynamic quantities which drive the atomic mobility. The data display a strong decrease of the activation energy with Al content and with the formation of the D03 structure, as well as very short relaxation times. Such an abnormally high atomic mobility can be attributed to a decrease of the migration energy through a lattice dynamics effect, similar to that recently proposed by several authors to explain the enhanced diffusion in some bcc transition metals and alloys.
Structural Defects in Amorphous Silicon Probed by Sub-Picosecond Photocarrier Dynamics
Authors: Stolk P.A. , Roorda S. , Calcagnile L. , Sinke W.C. , Van Linden Van Den Heuvell H.B. , Saris F.W. 
Published: March 2011

AbstractThe dynamics of a photogenerated electron-hole plasma in pure amorphous silicon (a-Si) in different stages of structural relaxation have been studied with sub-picosecond resolution using pump-probe reflectivity measurements. For high plasma densities (> 1020/cm3) the plasma evolution is dominated by Auger recombination. At lower plasma densities (≈ 1018/cm3) the plasma decays exponentially with a time constant τ, suggesting that carrier trapping dominates in this regime. The decay time τ increases with the temperature at which the a-Si has been annealed, ranging from τ = 1 ps for as-implanted a-Si to τ=14 ps for a-Si annealed at 500 °C. This observation is consistent with a reduction in the number of defects in a-Si upon thermal annealing.
Interface Structure, Grain Morphology, and Kinetics of Growth of the Superconducting Intermetallic Compound Nb3Sn Doped with ZrO2and Copper
Authors: Hall Ernest L. , Benz Mark G. , Rumaner Lee E. , Jones Karen D. 
Published: March 2011

AbstractOne method for the fabrication of the superconducting compound Nb3Sn involves interdiffusion of a surface coating of Sn alloyed with Cu on Nb containing Zr and O. In this study, the kinetics and microstructure associated with this reaction have been studied in detail. The results show that small Nb3Sn grains nucleate at the Nb3Sn/Nb interface, and that the Nb3Sn grains experience grain growth immediately after they are formed. ZrO2precipitates are observed in the Nb3Sn at the Nb3Sn/Nb interface and throughout the Nb3Sn. The ZrO2precipitates occur in the form of small partially-coherent spheres in the Nb3Sn. No ZrO2precipitates are observed by TEM in the unreacted Nb. The grain boundaries in the Nb3Sn region are coated with a Sn-Nb-Cu alloy which would have been liquid at the diffusion/reaction temperature. The thickness of the Nb3Sn reaction layer formed during the isothermal diffusion anneal is proportional to time to the first power, indicating “reaction”-controlled rather than “diffusion”-controlled kinetics. The absence of diffusion-controlled kinetics can be explained by the presence of the liquid coating on the Nb3Sn grains. Diffusion of Sn in this liquid layer is apparently fast enough to not be the limiting kinetic step.
Formation of Palladium Silicide and Germanide in the Pd/a-Si/Si., Pd/a-Ge/Si, and Pd/a-GeSi/Si Systems During Thermal Treatment
Authors: Edelman F. , Cytermann C. , Brener R. , Eizenberg M. , Weil R. , Beyer W. 
Published: March 2011

AbstractX-ray diffraction and transmission electron microscopy have been used to study the kinetics of phase transformations and the structure of Pd/a-Si, Pd/a-Ge and Pd/a-GeSi thin films deposited on Si substrates. Different kinds of amorphouis structures were used: a-Si:H:D, a-Si.:F, a-Ge:H:D, and a-GeSi:H:D. The first stage of phase transformation during heat treatment was palladium silicide (Pd2Si) and palladium germanide (Pd2Ge) formation at temperatures above 200°C. Annealing studies demonstrated that the presence of F in a-Si promotes the Pd2Si formation. The study of the Pd2Si crystallization process showed that: a) when the Pd layer and the a-Si layer are thin, then c-PdSi grows in a fractal-]ike form; b) when the Pd and a-Si both are thick, then c-Pd2Si grows in a globular structure; c) in both above mentioned cases a well-oriented [0011 texture forms. The growth of the silicide and germanide layers in the temperature range of 200-300°C was found to be controlled by a diffusion limited process. It was found that c-Pd2Ge transforms to c-PdGe above 200°C. The a-Ge,.,Si,. 5 alloy behaved similarly to a-Si forming only [001] textured c-Pd2(Ge,Si).
Measurements of to Temperatures of Supersaturated Si-As Alloys
Authors: Lee Kwang-Ryeol , West Jeffrey A. , Smith Patrick M. , Aziz M. J. , Knapp J. A. 
Published: March 2011

AbstractThe congruent melting point, or To curve, of crystalline Si-As alloys has been measured in the range of 1.6 to 18.1 at. % arsenic by line source electron beam annealing. Alloys were created by ion implantation of As into 0.1mm Si-on-sapphire and crystallized by pulsed laser melting. To temperatures decrease from 1673±10K at 2.0 at.% As to 1516±30K at 18.1 at.% As. The results of these measurements are significantly higher than the previous results of studies using pulsed laser melting techniques. Advantages of the e-beam technique over previous techniques are discussed. Chemical free energy functions of the solid and liquid phases were calculated from existing thermodynamic data. The calculated To curve agrees with the measured values only in low concentration region (less than 8 at.%).
Phase Transformation Kinetics During Precipitation of an Ordered Intermetallic from a Disordered Matrix -a Computer Simulation
Authors: Chen Long-Qing , Khachaturyan A.G. 
Published: March 2011

AbstractThe precipitation kinetics of an ordered intermetallic from a disordered matrix, which involves simultaneous ordering and decomposition, is studied by a computer simulation technique based on the microscopic diffusion theory. It is found that the precipitation starts from a congruent ordering transition, which may be continuous or nucleation and growth. This congruent ordering transition transforms the initially disordered state into a single phase nonstoichiometric ordered state with antiphase domains. The next stage is the decomposition which starts from the antiphase domain boundaries and then propagates into the ordered domains. And the final process is the coarsening of the order/disorder two-phase mixture. The predicted kinetics of precipitation is in excellent agreement with recent experimental observations in important alloy systems.
A Survey of Segregation at Interphase Boundaries in Ternary Ni-Ag-X Alloys
Authors: Rao G. , Wynblatt P. 
Published: March 2011

AbstractThis paper presents an alternative derivation of a discrete lattice regular solution model for computing the composition profile across an interphase boundary in a three component system. The model is applied to the calculation of the composition profiles across interfaces separating Ni-rich and Ag-rich phases in several Ni-Ag-X ternary systems (where X stands for Cu, Pd or Au). The results show that segregation to a (001) Ni-Ag interface is expected to be strong in the case of Cu, moderate in the case of Pd, and weak in the case of Au. It is also found that the Gibbsian interfacial excess of these segregants decreases with increasing temperature.
Molecular Dynamics Studies of Tweed and ω -Phase Instabilities in B2 NI62.5AL37.5 Alloys
Authors: Becquart C. , Clapp P.C. , Rifkin J.A. 
Published: March 2011

AbstractDiffuse TEM and x-ray data has been reported by several research groups that has been interpreted in terms of both tweed and (ω -phase instabilities. Computer simulations of 1,024 atom arrays were run at various temperatures using the Voter-Chen Embedded Atom Method (EAM) interactions. If the extra Ni atoms were placed at random on the Al sub-lattice of the B2 structure, at low temperatures both <110>* and <112>* diffuse streaking were observed in reciprocal lattice plots, indicative of tweed and ω - phase instabilities, respectively. The atomic displacements causing the <110> diffuse streaking could generally be classified as {110}<1-10> local shears, in agreement with accepted models of tweed. However, the displacements producing the <112>* streaking were best described as coordinated atom row motions in <111> directions, which does not agree with traditional ω -phase models based on (111) interplanar collapse. Both types of diffuse streaking decreased with increasing temperature, but the <110> type was stronger at all temperatures and persisted to higher temperatures. Furthermore, the atomic displacements producing the streaking were static at low temperatures ( persistence times greater than 1000 vibrational periods) but became dynamic at higher temperatures ( persistence times of the order of a few vibrational periods). Another interesting result was that by merely rearranging the extra Ni atoms into an ordered superlattice pattern, virtually no diffuse streaking of any type was observed at any temperature, strongly suggesting that compositional disorder ( or other kinds of point defects) are essential to induce tweed instabilities.*The asterisk represents a quantity in reciprocal space.
Dissolution Dynamics of Sub-Critical Clusters in Liquid Silicon
Authors: Uttormark Michael J. , Cook Stephen J. , Thompson Michael O. , Clancy Paulette 
Published: March 2011

AbstractPrevious attempts to simulate by Molecular Dynamics the spontaneous nucleation and growth of a crystalline Stillinger-Weber ‘silicon’ from the liquid have been essentially impossible because of constraints on system size and time scales. We have overcome these limitations by studying the related problem of the disintegration of crystalline ‘embryos’ into the liquid phase at temperatures slightly above the melting point. Molecular Dynamics simulations using the Stillinger-Weber potential were performed by embedding crystallites of 400 atoms in a liquid consisting of approximately 3600 atoms. During each simulation, the time-evolution of the size and shape of the embryo was followed until it became indistinguishable from the liquid. These simulations provide intriguing new information on the atomic processes involved in dissolution and on the macroscopic kinetics of small clusters. Comparisons of results at different temperatures, system sizes and initial configurations are shown and the implications of these cluster dynamics for crystal growth in supercooled liquids, homogeneous nucleation, and transient nucleation are discussed.
Evidence for the Direct Ejection of Clusters from Non-Metallic Solids During Laser Vaporization
Authors: Bloomfield L. A. , Yang Y. A. , Xia P. , Junkin A. L. 
Published: March 2011

ABSTRACTWe have studied the formation of molecular scale particles or “clusters” of alkali halides and semiconductors during laser vaporization of solids. By measuring the abundances of cluster ions produced in several different source configurations, we have determined that clusters are ejected directly from the source sample and do not need to grow from atomic or molecular vapor. Using samples of mixed alkali halide powders, we have found that unalloyed clusters are easily produced in a source that prevents growth from occurring after the clusters leave the sample surface. However, melting the sample or encouraging growth after vaporization lead to the production of alloyed cluster species.The sizes of the ejected clusters are initially random, but the population spectrum quickly becomes structured as hot, unstable-sized clusters decay into smaller particles. In carbon, large clusters with odd numbers of atoms decay almost immediately. The hot even clusters also decay, but much more slowly. The longest lived clusters are the magic C50 and C60 fullerenes. The mass spectrum of large carbon clusters evolves in time from structureless, to only the even clusters, to primarily C50 and C60. If cluster growth is encouraged, the odd clusters reappear and the population spectrum again becomes relatively structureless.The laser vaporization process in non-metallic systems closely resembles multiphoton laser photodissociation of clusters themselves. As a result, the best cluster source samples are powders or powder-like materials. We have found that carbon powder or exfoliated graphite sheet (Union Carbide Grafoil) are the best samples for the production of large carbon clusters. Many previous studies of carbon clusters formed in vacuum may have relied on the vaporization of carbon dust produced by repeated vaporizations in a small region of the sample.