bluuebunny/crossref_metadata_2025_split huggingface dataset:
Formation of Alloy Phases at Fe-Al Interface by Ion Beam Mixing, asRevealed by Interface-Sensitive Conversion Electron Mössbauer Spectroscopic Measurements
Authors: Godbole V.P. , Bhide V.G. , Ghaisas S.V. , Kanetkar S.M. , Chaudhari S.M. , Ogale S. B. 
Published: March 2011

ABSTRACTThe physical processes associated with the formation of various normal as well as metastable phases at an ion beam mixed Fe-Al interface are studied by using a novel interfacesensitive Conversion Electron Mbssbauer Spectroscopic (CEMS) technique.This technique which has been introduced and used for the first time in these investigations, is based on the deposition of a thin (less than 50 A°) layer of enriched Fe 5 7 isotope (95.45% by composition) at the interface between the aluminium substrate and a post-deposited 250A° film of natural iron (only 2.2% of Fe57), leading to a considerably enhanced spatial selectivity of the M~ssbauer information regarding the reactions occurring at the interface.A number of samples prepared in the manner mentioned above are subjected to an argon ion bombardment at an incident ion energy of 100 keV and a dose of ≃ 2 × 1016ions/cm2The ion beam mixed samples are annealed at different temperatures in the range between 300°C to 600°C for twenty minutes, to provide the thermal energy for the growth of different FexAlyphases at the interface.Conversion Electron Mössbauer Spectroscopy is employed at each stage of the ion beam processing and annealing of the samples, to characterize the phases formed. All the Mbssbauer spectra are least square fitted using the MOSFIT programme to obtain the best-fit values of Mössbauer parameters. The results indicate a substantial broadening of the Mössbauer lines for the as-implanted samples, a fact which can be attributed to the beam induced radiation damage. Subsequent annealing of the samples at different temperatures leads to annealing of damage and further to the formation of Fe3Al and FeAl solid solution. Mössbauer spectra of the samples annealed at 500°C indicate segregation of Fe at the interface along with the formation of Fe3Al phase, while annealing at 600°C results in the formation of Fe-Al solid solution phase with traces of effectively unreacted metallic Fe. The unimplanted composites heat-treated in an identical manner do not show these features. These results which are supported by RBS measurements, are interpreted and discussed in terms of the non-equilibrium nature of the ion beam processing of the interface.
On the Segregation of in Solutes to High-Angle (001) Twist Grain Boundaries in Al
Authors: Wolf D. , Lam N. Q. 
Published: March 2011

ABSTRACTThe energies of the Σ = 5, 13, and 17 (001) coincidentsite lattice (CSL) twist boundaries in Al containing small amounts of Zn solutes have been calculated using an iterative energy minimization technique in conjunction with interatomic potentials derived entirely from first principles. By determining both the energies of substitution in the bulk and in different sites in the boundary, the site selectivity for Zn segregation at the grain boundary has been investigated. In the lattice plane immediately near the grain boundary, Zn solutes were found to prefer the lower-symmetry non-coincidence sites while, in the next plane, substitution in the coincidence sites is preferred. The effect of Zn-Zn interactions has also been considered for small solute concentrations. It is found that the magnitude of the Zn-Zn interaction energy is remarkably insensitive to the particular sites occupied by the Zn atoms as well as the detailed geometry of the interface.
Structure and Dissociation of 15° <110> Tilt Boundaries in Germanium
Authors: Skrotzki W. , Wendt H. , Carter C. B. , Kohlstedt D. L. 
Published: March 2011

ABSTRACTThe structure and dissociation of grain boundaries in Ge bicrystals, grown by the Czochralski method, have been analyzed by visible light and transmission electron microscopy. The seed crystals were oriented to yield either a symmetric or an asymmetric grain boundary plane with a 15° rotation about a common <110> direction. The asymmetric boundary, with a {111} boundary plane, dissociated along most of its length into a first order twin boundary (Σ 3) and a symmetric 55° grain boundary (Σ 41c). The symmetric 15° boundary is composed of an array of Lomer dislocations. Contrary to theoretical predictions, this boundary is stable.
Nucleation Phenomena in Transitions from two to three phases, diffusion Couples, Phase Stability,the thin film formation of some silicides
Authors: D»Heurle F. M. 
Published: March 2011

EXTENDED ABSTRACTNucleation is generally understood to refer to the initial process of creating a new phase, for example, liquid water, from another phase, water vapor, as a result of a temperature excursion which carries the system through some critical temperature (in the case at hand, at normal atmospheric pressure, 100°C). The processes involved in such transformations have been the object of careful observations for a long time, at least two centuries; a very good historical perspective on this subject is found at the beginning of Ref. 1. The special case of metal vapors condensing on substrates in order to form thin films is considered in all texts dealing with thin film preparation [2]. The precipitation of a new phase, such as CuAl2, from a supersaturated solution (of copper in aluminum) has immense technological importance which motivates the attention being paid to nucleation phenomena in all metallurgical treatises [3,4].(A particularly thorough discussion is found in Ref. 5.) In all cases, nucleation phenomena are controlled by the necessity of creating an interface between the nucleated phase and the original matrix. The energy of the interface imposes special thermodynamic constraints on the evolution of the system.
Photoemission Studies of the Ag/InP(110) Interface: Interfacial Reactions and Schottky Barrier Formation
Authors: Petro W. G. , Kendelewicz T. , Babalola I. A. , Lindau I. , Spicer W. E. 
Published: March 2011

ABSTRACTRoom-temperature interfacial reactions at the Ag/InP (110) interface have been studied using soft x-ray photoemission spectroscopy of the In 4d and P 2p core levels. For low Ag coverages (less than 1 monolayer (ML)) no measurable change in core level shapes is observed, and the shift in core level position is due solely to band bending. At high Ag coverages (up to 72 ML) we observe dissociated In metal, P atoms near the surface, and Ag clustering. Fermi level movement is deduced from these spectra using a deconvolution technique, and pinning positions of 0.40 ± 0.05 eV below the conduction-band minimum for n-type and 0.5 ± 0.l eV above the valence-band maximum for p-type are found. These positions are in close agreement with calculations of native defect levels.
Selective Growth, Diffusion Layers and the Schottky Barrier Height in Nickel Silicide-Silicon Interfaces
Authors: Erskine J. L. , Chang Yu-Jeng 
Published: March 2011

ABSTRACTSelected interface phenomena associated with metal semiconductor contacts are discussed in relation to recent experimental and theoretical work on the electronic properties, interface formation and structure, and device characteristics of nickel-silicon interfaces. Evidence is presented which suggests that a well-defined interfacial phase is present at all nickel silicide-silicon boundaries formed by deposition of nickel atoms onto silicon surfaces. The existence of this phase is shown to account for several important interface properties of the nickel silicide system including selective growth, the rotational twin structure of epitaxial films and the observed invariance of the nickel silicide-silicon Schottky barrier height as the silicide contact stoichiometry is varied.
Shallow Contact Formation of Gadolinium Silicide
Authors: Cheng I. C. , Lau S. S. , Thompson R. D. , Tu K. N. 
Published: March 2011

ABSTRACTGadolinium silicide with its attractive features of low formation temperature of about 350°C and low Schottky barrier height on n-type single-crystal silicon substrates (ϕnB1∼O.4ev,ϕpB ∼ 0.7ev) was chosen for studying the feasibility of forming shallow uniform contacts. Samples with various compositions prepared by both bilayer evaporation with a configuration of Si(α)/Gd/Si(xtl) and coevaporation with a Si−Gd /Si(xtl)structure were used for studying the contact formation as a function of composition and heat treatment. We found that shallow contact formation can be achieved provided that the following conditions are met: (a) for bilayer evaporation, the atomic ratio of Si(α)/Gd ≥ 2 should be maintained, (b) for coevaporation, the Si to Gd atomic ratio between 1.7 and 2.0 is desired. The bilayer deposition scheme appears to be a more convenient technique to use in practice.
Epitaxial Growth of FeSi2 on (111)Si
Authors: Cheng H.C. , Chen L.J. , Your T.R. 
Published: March 2011

ABSTRACTIsothermal annealing, two step annealing and ion beam mixing were performed to induce interfacial reactions between iron thin films and silicon substrate. Both orthorhombic and tetragonal FeSi2 were found to grow epitaxially on (lll)Si with orthorhombic FeSi2 being the predominant phase. No epitaxial growth of FeSi2 on (001)Si was detected. Epitaxial islands as large as 40 μm in size were formed by a scheme combining ion beam mixing and two step annealing.
Material Properties of Semiconductor Strained-Layer Superlattices
Authors: Osbourn G. C. 
Published: March 2011

ABSTRACTHigh quality superlattices can be grown from semiconductor materials with lattice mismatches of several percent if the layers are kept sufficiently thin. The mismatch in these structures is accommodated by coherent layer strains, so that misfit defects are not generated at the superlattice interfaces. These strained-layer superlattices have unique structural, optical, and electrical properties due to both the large layer strains and the flexibility in the choice of lattice mismatched layer materials. Recent results which demonstrate the high crystalline quality of these mismatched heterostructures are reviewed. Further results are presented which illustrate some of the unique material properties of these structures, and potential applications associated with such properties are discussed.
Ion Channeling Analysis of GaAsxP1-X/Gap Strained-Layer Superlattices
Authors: Picraux S. T. , Biefeld R. M. , Osbourn G. C. , Chu W. K. 
Published: March 2011

ABSTRACTAxial ion channeling and backscattering with 2 MeV 4He are used to probe the strain in GaAs. 16P.84/GaP strained-layer superlattices (SLS) by two methods. The tetragonal distortions in the growth direction of SLS's give rise to alternating tilts in inclined crystal directions at each interface. In the first method the large increase in dechanneling along <110> directions containing the angular tilts is measured relative to the negligible increase in dechanneling along the <100> growth direction. This method provides a sensitive depth-dependent measure of strain but requires computer simulation for quantitative analysis. In the second method, channeling angular scans are used to directly measure the lattice strain by the shift in the <110> crystal direction in the top layer relative to the average <110> direction. These results demonstrate the validity of the strain accommodation model for the interpretation of the dechanneling and indicate that GaAsxP1-x/GaP SLS structures of high crystalline quality can be obtained with strains somewhat lower than that predicted theoretically from bulk lattice properties.
Tetragonal Distortion in VPE and LPE In1-xGaxAs Grown on (100) Inp
Authors: Macrander A. T. , Chu S. N. G. 
Published: March 2011

ABSTRACTThe tetragonal distortion present in both VPE and LPE In1-xGaxAs was measured from X-ray rocking curves of the (511) reflection. These measurements were then used to establish coherency limits. In addition, wafer curvature was measured and compared to that calculated via an expression which incorporates both tetragonal distortion and misfit dislocations. Agreement was found except for a case in which stacking faults were present.
Marker Experiments for the moving Species in Silicides During Solid Phase Epitaxy of Evaporated Si
Authors: Lien Chuen-Der , Bartur Meir , Nicolet Marc-A. 
Published: March 2011

ABSTRACTEvaporated W, implanted Xe, and implanted 18O were used as markers to study the dominant moving species during (a) solid phase epitaxy (SPE) of evaporated Si, (b) silicide formation, and (c) oxidation of silicides on Si substrate.MeV 4He+ backscattering spectrometry and 18O (p, α)15 N nuclear reaction were used to monitor the evolution of elemental profiles as well as the change in the marker position. In most cases, the dominant moving species in SPE is the same as that observed in the formation and oxidation of that silicide. However, in CrSi2 the dominant moving species is Si during silicide formation, but Cr during SPE or oxidation.
Analysis of the Si-ON-Insulator Structure by Modeling of the Interface Atomic Arrangement
Authors: Saito T. , Yamakoshi Y. , Ohdomari I. 
Published: March 2011

ABSTRACTA structure of interface between crystalline Si (c-Si) and underlying SiO2 film formed by Si-on-Insulator technique has been analyzed by modeling of interface atomic arrangement. A ball-and-spoke model of a stoichiometrically abrupt c-Si/SiO2 interface has been constructed by connecting a (100) c-Si lattice and a continuous random network model of amorphous SiO2 . A Keating-type potential has been used for the interatomic interactions. The bond bending distortion energy of both Si and O atoms increases at the interface, while the bond stretching energy is negligibly small. The amount of interface energy due to bond distortion is 0.20J/m2.
Metallurgy and Morphology of the Interface of AuGe Ohmic Contact to GaAs
Authors: Lakhani Amir A. , Urech David R. 
Published: March 2011

ABSTRACTScanning electron microscopy and energy dispersive x-ray analysis have been used to study the formation of AuGe ohmic contacts to GaAs. Both sintering and alloying of the metallization result in deep trenches and spikes. Lateral growth of the metallization at the perimeter of the contact is also reported. In situ analysis during the formation of the ohmic contact has demonstrated the formation of a solid phase complex of Au-Ge-As and the rapid loss of As at 450°C. The influence of the Au-Ge-As complex and the loss of As on the specific contact resistivity is discussed.
Transport Studies in Single-Crystal Films of Cosi2 and Nisi2
Authors: Hensel J. C. , Tung R. T. , Poate J. M. , Unterwald F. C. , Jacobson D. C. 
Published: March 2011

ABSTRACTTransport studies have been performed on thin films of CoSi 2 and NiSis2 in the temperature range 1 to 300 K. The conductivities are metallic with essentially the same temperature dependence; however, the residual resistivities are markedly different even though the two silicides are structurally similar (the room temperature resistivity of NiSi2 being at least twice that of CoSi2 of 15 μΩ cm). The difference is attributed to intrinsic defects in NiSi2. This defect has been simulated by ion bombardment of the film where it is also shown that Matthiesen's rule is obeyed over a remarkable range of bombardment doses.
Interface Reactions In Tasi 2/Si Contacts at High Temperature
Authors: Oppolzer H. , Neppl F. , Hieber K. 
Published: March 2011

ABSTRACTThe influence of deviations from TaSi2 stoichiometry in co-sputtered,amorphous Ta-Si films on interface reactions in contacts to silicon at 900°C was investigated by TEM of thin cross sections through the contact windows. Excess silicon precipitates epitaxially in the contacts, pits are formed for silicon deficiency. The involved lateral silicon transport ranges over several tens of microns. The effects of interfacial oxides and a crystalline TaSi 2 pad layer were studied.
Introduction of Electrical Defects in P-Type Silicon due to Electron-Beam and RF Sputtering Metallization Processes
Authors: Paz O. , Auret F. D. 
Published: March 2011

ABSTRACTDefects introduced in p-type silicon during RF sputter deposition of Ti-W and electron-beam evaporation of hafnium were investigated using I-V, deep level transient spectroscopy and electron-beam induced current techniques. DLTS measurements indicate the presence of several deposition and evaporation induced defect states. H(0.35) at EV + .35 eV and H(0.38) were the most prominent defects. Minority carrier diffusion length results taken after annealing showed that in the case of the Hf contacts the damage was annealed out while in the case of Ti-W it was not. These differences in carrier recombination are traced to the concentration of H(0.35). Sputtering or evaporation induced damage also increased the barrier height. This observed increase was modeled assuming the introduction of donor-like defects.
SI Contacts Formed from Spun-on Metallo-Organic Solutions
Authors: Pai C. S. , Zhang B. , Scott D. M. , Lau S. S. , Bartur M. , Tseng W. F. 
Published: March 2011

ABSTRACTThe use of spun-on liquids to form ohmic and Schottky barrier contacts on Si has been investigated. Two commercially available metallo-organic solutions containing Au or Pt were applied to Si substrates by spinning techniques. The Au or Pt contacts were then formed by annealing at 250°C or 450°C respectively. The metallurgical interactions between the spun-on Au or Pt layers and the Si substrate were investigated by MeV backscattering spectrometry and X-ray diffraction as a function of the annealing temperature. The resulting electrical characteristics were investigated with four point probe, I-V and C-V techniques. It was found that the spun-on Au or Pt films react with Si substrates at much higher temperatures than those deposited by vacuum evaporation. The diode characteristics of the spun-on Au films are comparable to those of evaporated Au films ( φB ∼0.85V, n ∼1.08), whereas diode characteristics of spunon Pt films show no linear region on the ln I-V curve. The application of spun-on Au also improves the bondability of Si chips on Mo headers.
The Measurement of Silicide Schottky Barrier Heights by Use of Photovoltaic Techniques
Authors: Kuech T.F. , Wu C.S. , Lau S.S. 
Published: March 2011

ABSTRACTSchottky barrier structures often exhibit forward bias current voltage characteristics possessing a marked deviation from ideal behavior. In many cases, this deviation can be attributed to the influence of an appreciable series resistance on the diode characteristic making the determination of the actual Schottky barrier height from this characteristic difficult. In a study of rare earth silicides on Si, the present authors have successfully employed an alternative technique which overcomes this series resistance effect. This technique is derived from the conventional methods for obtaining barrier height and series resistance values in photovoltaic devices, although not necessarily requiring transparent metallizations. Photogenerated current from the device periphery is utilized here in the determination of the barrier height. The measurement of both open circuit voltage and the short circuit current at varying illumination intensities allows the junction characteristic to be determined essentially free from series resistance effects. A comparison will be made between the values of the barrier height derived from conventional J-V and photoresponse measurements, with photovoltaic measurements made on structures possessing either a semi-transparent or opaque metallization.
Lateral Silicide Growth
Authors: Zheng L. R. , Zingu E. , Mayer J. W. 
Published: March 2011

ABSTRACTSilicide formation and growth kinetics have been investigated with lateral diffusion couples formed by deposition of Ni and Cr layers on patterned Si substrates and by deposition of Ni patterns on Si films. For annealing temperatures between 520 and 650°C the growth of CrSi2follows a (time)½ dependence with an activation energy of 1.4± 0.1 eV. In Ni-silicide formation at temperatures below 600°C, Ni was the predominant moving species. As the temperature increased, the motion of Si became significant. The apparent activation energy for silicide formation varied from Ea ≅ 1.4 eV for Ni motion at relatively low temperatures to Ea≅ 2.3 eV for Si motion that occurs at high temperatures. Lateral diffusion in device geometry structures resulted in degradation of contact planarity due to the penetration of metal silicides in Ni-Si structures or the erosion of silicon in Cr-Si structures.
The Kinetics of Platinum Silicide Formation Using CW Lamp Annealing
Authors: Hopkins C. G. , Baumann S. M. , Blattner R. J. 
Published: March 2011

ABSTRACTThe reaction of a metal film with polycrystalline silicon to form a metal silicide has been shown to occur very rapidly when using cw lamp annealing in contrast to conventional furnace annealing. The faster reaction kinetics implies a more efficient energy coupling (radiative heating) versus the conductive/convective heat transfer processes which dominate furnace annealing. From Rutherford backscattering determinations of the thickness of PtSi formed as a function of anneal time (t), we have found the relationship to be linear in t with growth rates in the rangg 10−7–10−6 cm/sec (10 – 100Å/sec) for the temperature range 375 – 450° C. From these data the activation energy for the formation of PtSi was calculated to be 1.8± 0.2eV for cw lamp annealing, in reasonable agreement with literature values from conventional furnace annealing experiments.
Properties of In Situ Reinforced Silicon Nitride Ceramics
Authors: Li C.-W. , Yamanis J. , Whalen P.J. , Gasdaska C.J. , Ballard C.P. 
Published: March 2011

ABSTRACTIn situ reinforced (ISR) silicon nitride ceramics have been developed to have microstructures that mimic the best whisker containing ceramic matrix composites. Large, interlocking needle-like grains of beta silicon nitride can be produced throughout these materials to create an isotropic, high-temperature ceramic with high fracture toughness (˜9 MPa√m), good high-temperature strength (4 Pt MOR = 750 MPa at 25°C and 500 MPa at 1375°C), high Weibull modulus (m >20), and low creep at high temperature. Since these materials do not rely on transforming metastable phase inclusions as a toughening mechanism, their fracture resistance is virtually insensitive to temperature. The high crack growth resistance of these ceramics also yields a material which is extremely defect tolerant. Residual MOR strengths of 300–400 MPa are typical after multiple 50-kg Vicker's indentations of the sample tensile surface. After abrasive particle impact, the biaxial strengths of the in situ reinforced ceramics are typically more than twice that of traditional, fine-grained silicon nitrides.Unlike ceramic composites toughened using whisker additives, the in situ reinforcement approach to silicon nitride development does not require the use of complicated whisker dispersion techniques for green processing, nor is shape-limiting hot pressing required for densification during sintering.
Porous Alumina by Hot Isostatic Pressing
Authors: Kuzjukevics Anatolijs , Ishizaki K. 
Published: March 2011

ABSTRACTProduction of porous alumina ceramics by capsule-free hot isostatic pressing of bimodally distributed alumina powders with a large size difference (>10) and reaction sintering of alumina powder and boron oxide formed by oxidation of boron nitride during sintering were investigated. The influence of the composition of bimodally distributed alumina and alumina-boron nitride mixture of powders on open and closed porosity was studied.HIP treatment at 1600°C provided sintering of only fine-grained powder. A small loss in open porosity (about 4%) is observed with increasing of the fine powder weight fraction up to 0.4.Reaction sintering of a fine-grained alumina powder with boron oxide gives significant (about 30%) increase of open porosity.