bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coating of Silicon Nitride with Sintering Aid
Authors: Joshi P. N. , Mccauley R. A. 
Published: March 2011

ABSTRACTCommercially available silicon nitride powders were coated with various metal oxides with the help of metal-organic surfactants in an aqueous medium. A surfactants could also act as a dispersant. The coatings were studied by XPS, TEM and accoustophoresis and the mechanism for formation of these coatings is proposed. The amount of sintering aid incorporated was determined by the surface area and surface chemistry of the nitride powder, the pH of the solution, the structure of the surfactant and the surface charge behavior of the powder and the coating. Multicomponent coatings were also possible by precise control of these parameters. The sintering behavior of the coated powders and the properties of the sintered material were promising.
In-Situ Preparation of TiC/Al2O3, TiN/Al2O3 and TiN/AIN Composites From Alkoxide-Derived Precursors
Authors: Jiang Zhiping , Rhine Wendell E. 
Published: March 2011

ABSTRACTThe reaction between furfuryl alcohol (FuOH) and the hydrolysis product of a mixture of Ti(O-n-Bu)4 and Al(O-sec-Bu)3 (AI:Ti=1:1) resulted in the formation of soluble polymeric solids. Pyrolysis of these polymers in argon yielded TiC/A2O3 composite at 1250 °C. When these polymers were pyrolyzed in ammonia, TiN/AI2O3 or TiN/AIN composite was formed. All these composites showed fine microstructure and excellent homogeneity. Furthermore, the structure and pyrolysis chemistry of these polymeric precursors as well as the microstructure of the pyrolysis products were studied by means of FTIR, TGA, XRD, SEM, TEM, STEM, Auger, elemental analyses etc.
Synthesis of Reaction Bonded Silicon Nitride from High Purity Si Powders
Authors: Haggerty John S. 
Published: March 2011

ABSTRACTSignificantly improved reaction kinetics and properties have been realized for reaction bonded Si3N4 (RBSN) by using Si powders having unusual physical and chemical characteristics combined with clean, oxygen-free processing conditions. For instance, complete nitridation can be achieved in < 1 h at 1150°C or < 100 m at 1250°C without pre-nucleation, or < 1 h at 1100°C with pre-nucleation. These compare with normal schedules of ∼100 h at 1470-1500°C. Resulting strengths (up to 870 MPa) and oxidation resistances of the RBSN essentially equal those of fully dense Si3N4 even though RBSN includes 25% open porosity. The results show that every aspect of the process, ranging from powder synthesis to < ppm levels of oxygen in the nitriding atmosphere, have demonstrable effects on the reaction kinetics and the resulting properties of the parts. With careful processing, reaction formed ceramics can compete advantageously with fully dense counterparts.
Synthesis of a MoSi2/SiC Composite in Situ Using a Solid State Displacement Reaction
Authors: Henager C. H. , Brimhall J. L. , Hirth J. P. 
Published: March 2011

ABSTRACTSolid state displacement reactions are being studied at Pacific Northwest Laboratory (PNL) as a method of synthesizing intermetallic and ceramic composites in situ. A high-strength in situ composite of MoSi2/SiC was synthesized using a solid state displacement reaction between Mo2C and Si. Diffusion couples between Mo2C and Si processed at 1200°C revealed the formation of aligned SiC platelets in a MoSi2 matrix. In situ composites were also synthesized by blending Mo2C and Si powders and vacuum hot-pressing the powders at 1350°C for 2 h followed by 1 h at 1700°C. The resulting microstructure consisted of 1-μm diameter SiC particles (30 vol%) uniformly dispersed in a fine grained MoSi2 matrix. Densities of 5.53 g/cm3 were obtained along with a microhardness of 14.2 GPa. Bend bars and chevron-notched bars revealed a strength of 475 MPa and a fracture toughness of 6.7 MPa√m at room temperature. Bend strengths increased to 515 MPa at 1000°C and then decreased to 112 MPa at 1200°C. Measured fracture toughness increased to 10.5 MPa√m at 1050°C.
The Combustion Synthesis of B4C-A1203-Al Composite Materials
Authors: Feng H. J. , Moore John J. , Wirth D. G. 
Published: March 2011

ABSTRACTThe combustion synthesis of the B4C-2Al203-xAl ceramic-metal composite system has been studied using the propagating mode of ignition for the reaction 2B203 + C + (4 + x)Al = B4C + 2Al203 + xAl in which x was varied between 0 and 3. The volatile constituent(s), eg. B2O3, resulted in the formation of an expanded or foamed ceramic with a uniform porous structure. The porosity represents ≥65%, and an expansion of 300-500% occurred mainly in the vertical direction. The effect of green density and reaction stoichiometry on product density, pore morphology, propagation rate and overall activation energy is discussed.
Biomimetic Ceramics: What, Why and How?
Authors: Calvert Paul 
Published: March 2011

ABSTRACTThe role of biomimetic approaches in materials engineering is reviewed. In the case of ceramics, close parallels in structure and function can be seen between synthetic and biological materials. Biological ceramics have resolved difficulties which are limiting the application of synthetic materials, particularly in the need for greater toughness. The enhanced toughness of materials such as shell and tooth enamel can be attributed to microstructural factors. Both natural materials contain a small amount of polymer. If this is essential, then any synthetic mimetic material would be limited by the temperature resistance of the polymer. In fact, much of the toughness is dependent on the elongated particle morphology and does not require polymer. Routes to forming ceramics with such elongated particles are discussed.
Ion-Exchange Strengthening a Mica-Based Machnable Glassceramic
Authors: Chin T.S. , Liu H.S. , Chiu S.Y. , Chen C.I. , Hsu S.E. 
Published: March 2011

ABSTRACTIon exchange was carried out on a lithium-doped fluorophlogopite machinable glassceramic with composition, in wt%, 52.2 SiO2, 14.0 Al2O3, 14.2 MgO, 12.5 MgF2, 1.4 Li2O, and 5.7 Na2O, to study the strengthening effect. The crystalline phases after annealings were Na-fluorophlogopite and betaspodumene, with a volume fraction of about 2:1. Ion exchange of Li by K in the glassceramic at 770° C for 4 h improved 2.1 to 2.3 times the three point bending strength (TPBS). Hence strong machinable ceramic with TPBS of greater than 300 MPa can be made. Ion exchange increases 100% electrical resistivity and improves 21% chemical stability, due to a surface layer of about 100 micrometer enriched with K.
Preparation of Homogeneous Aluminosr, Icate Gels by sol/gel Methods
Authors: Reese M. E. , Mccormick A. V. , Sanchez J. 
Published: March 2011

ABSTRACTThe factors affecting the production of homogeneous aluminosilicate gels from alkoxide precursors were investigated. Aluminosilicate gels were made in acidic conditions with a prepolymerization of the silicate precursor followed by the addition of the alumina precursor.Confirming earlier studies, we found that the gel homogeneity is increased when the rate of gelation decreases. The reduction of the water content and/or the aluminum precursor, and more surprisingly the increase of the acid concentration contributed to the gel time increase and thus the gel homogeneity improvement.
Processable Oligomeric and Polymeric Precursors to Silicates Prepared Directly from SiO2, Ethylene Glycol and Base.
Authors: Bickmore Clint , Hoppe Martin L. , Laine Richard M. 
Published: March 2011

ABSTRACTBimetallic glycolato silicates of the form M2 Si2(OCH2CH2O)5 where M is an alkali metal, can be synthesized directly from SiO2, ethylene glycol and MOH. Further reaction with HO(CH2CH2O)4H, PEG4, transforms these compounds into rheologically useful polymers. These polymers offer considerable potential for processing novel silicate glass shapes, e.g. thin films, fibers and membranes, from relatively inexpensive precursors materials. In this paper, we describe pyrolysis studies on the model compound Li2 Si2(OCH2CH2O)5 as a prelude to determing the utility of the polymeric precursors. These studies delineate the effects of temperature on the decomposition processes whereby the glycolato silicate transforms into almost phase pure, crystalline Li2O-2SiO2. This work is contrasted with previous pyrolysis studies on K2 Si2(OCH2CH2O)5.
Ambient Effects on Thin Film Interactions
Authors: Chang Chin-An 
Published: March 2011

ABSTRACTThin film interactions often show strong dependence on the annealing ambients used. The outdiffusion of a large number of metals and semiconductors through an overcoating gold film and subsequent formation of surface oxides have been observed to be greatly enhanced using a steam or air ambient compared with those using vacuum or inert ambients. The ambient effects become more puzzled when the overcoating metal consists of gold and silver layers, depending on the sequence of these layers. These ambient effects are shown to be well correlated by a surface potential model which considers both the relation between the overcoating metal and the underlying diffusing species, and the effects of ambient on the surface properties of the overcoating metal at the interface. Further ambient effects have been predicted and confirmed, including reduced interactions by oxygen for many systems with different overcoating metals. Different interaction mechanisms have also been observed, including competing ambient effects, competing interactions, and preferential reactions, all affected by the ambients used. Understandings of the various ambient effects not only provide important insights into the interface interactions in general, but also have great impact on metallurgical contacts in device technologies. Future studies for the ambient effects are also discussed.
Effect of Nitrogen and Oxygen Impurities on Tantalum Silicide Formation
Authors: Ho K. T. , Lien C.-D. , Nicolet M-A. , Scott D. M. 
Published: March 2011

ABSTRACTTantalum, being a refractory metal, is sensitive to ambient impurities when forming a silicide. By introducing nitrogen and oxygen impurities into a tantalum-silicon system, interesting chemical and physical effects are observed in their subsequent reactions. Nitrogen and oxygen behave similarly in such a system. If initially present in Ta, they segregate into the still unreacted Ta as the silicide layer grows at a somewhat retarded rate. The same impurities, initially present in Si, are immobile in the form of stable compouis and suppress TaSi2 growth. The rare isotopes 15N and 18O are introduced bY implantation and Profiled by 15N(P,α)12C and 18O(P,α)15N nuclear reaction analyses, respectively. In addition, unintentionally incorporated 18O is checked by the 16O(d,α) 14N nuclear reaction. The results are explained in terms of the moving species Si, and of the chemical affinity, solubility and diffusivity of the impurities in their host lattice.
Oxygen Influence on Titanium Silicide Formation
Authors: Bentini G.G. , Berti M. , Cohen C. , Drigo A.V. , Guerri S. , Nipoti R. , Siejka J. 
Published: March 2011

ABSTRACTThe oxygen behaviour and its influence on the annealing properties of the TiO2/Si and Ti/TiO2/Si systems have been investigated. For the TiO2/Si system no reaction at all could be evidenced after vacuum annealing up to 900°C for 30'. In the Ti/TiO2/Si system metallic Ti reacts with the TiO2 film above 400°C and at 600°C a uniform oxygen solid solution at the solubility limit was obtained without any Si reaction. Silicide formation occurs for annealing temperatures higher than 650°C and causes oxygen expulsion from the reacted layer and consequently a rise in its concentration at the surface where Ti oxide precipitation takes place. This surface oxide layer prevents a further growth of the silicide up to 850°C. The reaction of the whole metal film is attained only by annealing at 900°C or above, when the oxide is completely reduced and an important oxygen loss takes place. A model explaining this behaviour is proposed.
RBS and TEM Analysis of Ta Silicides on GaAs
Authors: Kavanagh K.L. , Chen S.H. , Palmstrom C.J. , Carter C.B. 
Published: March 2011

ABSTRACTElectron-beam and sputter-deposited Ta silicides on GaAs were annealed in an As2 overpressure ambient to temperatures as high as 920°C for 20mim. The films were then characterized with RBS, cross-sectional TEM and both electron and x-ray diffraction. The morphology of sputtered TaSi2/GaAs interfaces did not change, however, some interaction was detected at electron-beam deposited GaAs/silicide interfaces. Arsenic in-diffusion was detected at temperatures above 800°C and it was found to be dependent on the stoichiometry of the films. Arsenic diffusion into Si-rich electron-beam and sputter deposited films was low, whereas significantly more As diffused into the Ta-rich silicide. Some indium (3×l015atoms/cm2), from the InAs used as the source of As2overpressure, was observed to accumulate at all GaAs/silicide interfaces at temperatures above 800°C.
Prediction of Silicide First Phase and Phase Sequence from Heats of Formation
Authors: Pretorius R. 
Published: March 2011

ABSTRACTAn effective heat of formation (δH') is formulated, enabling δH' to be calculated as a function of the concentration of metal and silicon available for interaction to form a silicide. A rule for first phase formation is proposed according to which, “The first silicide compound to form during metal-silicon interaction is the congruent phase with the most negative effective heat of formation at the concentration of the lowest eutectic temperature of the binary system.” The effective heat of formation concept is also extended to predict subsequent phase sequence.
Diffusion of AS, B, and P In Tasi2
Authors: Eichinger P. , Frenzel E. , Neppl F. 
Published: March 2011

ABSTRACTImplantation range parameters and diffusion characteristics of As, B, and P in TaSi2 have been investigated, mainly by SIMS. It is shown that dopant diffusion in the silicide is much faster than in polycrystalline Si. Significant outdiffusion is observed for P, segregation effects are seen with B only. No dopant penetration through gate oxide is detected.
Ion Beam Enhanced Adhesion of Thin Films
Authors: Baglin J. E. E. , Clark G. J. , BØttiger J. 
Published: March 2011

ABSTRACTIon beam enhanced adhesion has been studied for the case of thin Cu films deposited on substrates of alumina, fused quartz and glass-ceramic. Beams of He+ (200 keV) and Ne+ (280 keV) were used, in order to test the respective roles of nuclear and electronic interactions in this process. Peel tests were used to produce the first quantitative studies of adhesion strength as a continuous function of ion dose. Bond strengths improved after irradiation at modest doses, sometimes by a factor of 20. Subsequent heating in a helium furnace produced as much as an order of magnitude further adhesion improvement in irradiated samples. Similar tests for Cu on Teflon produced excellent bonding for ion doses of ∼ 1014/cm2. The results indicate bond breaking and reconstruction at a sharp interface, with no significant metalsubstrate intermixing. The new bond is stable under heat cycling.
Phase Formation and Kinetic Processes in Silicide Growth.
Authors: Ottaviani G. 
Published: March 2011

ABSTRACTTwenty years of research have now been devoted to investigating reaction products obtained by annealing metal-layer/silicon structures. A wide variety of cases have been analyzsed and a considerable amount of data has been produced. Despite the vast amount of information available, several aspects concerning phase formation and kinetic processes are not yet well established. The purpose of this paper is to investigate the mechanisms of phase formation and to show the importance of kinetic factors in the appearance of various compounds. Results will be shown for a single metal layer deposited on silicon, for bilayers. and for alloys. Depending upon the starting structure, metal-rich or silicon-rich silicides can be formed. Moreover, by modifying the boundary conditions, it is possible to change the growth kinetics of the silicide phase that forms.
An Interface-Sensitive Conversion Electron Mössbauer Spectroscopic Study of the Ion Beam Induced Reactions at Fe-Si Interface.
Authors: Godbole V.P. , Bhide V.G. , Ghaisas S.V. , Kanetkar S.M. , Joshee R.S. , Ogale S.B. 
Published: March 2011

ABSTRACTThe ion beam induced reactions at Fe-Si interface are studied for the first time using a novel interface-sensitive Mössbauer probe.The samples used in these studies are prepared by depositing a thin layer (<450A°) of enriched Fe57 isotope (95.45% by composition) on a freshly cleaned silicon (111) substrate followed by a deposition of a 150Ao film of natural iron (Fe 57 only 2.2%).These samples are subjected to Xetion bombardment at an incident ion energy of 100 keV and a dose of 6 × 1015 ions/cm2 The technique of Conversion Electron Mössbauer Spectroscopy (CEMS) is used to characterize the formation and growth of different phases as a function of annealing treatment. The spectra are leastsquare fitted using the MOSFIT programme.The MHssbauer lines for as-deposited and ion bombarded samples show a considerable broadening, which is a clear signature of a large concentration of defects formed at the interface due to ion beam induced collision cascades. As the samples are annealed the resonance lines are sharpened indicating recovery of stoichiometrically well-defined phases from an initial defective state. The present study indicates formation of FeSi and Fe3 Si phases after the annealing treatment-RBS measurements are used to confirm the mixing.These results are analyzed in terms of the non-equilibrium features of the directed energy processing of interface.
Precipitation of Copper in Transmutation Doped Silicon
Authors: Gleichmann R. 
Published: March 2011

ABSTRACTDuring the long-time diffusion of transmutation doped silicon a variety of large CuSi precipitates is introduced into the material. The precipitates have been found to be metastable and transform during subsequent heat treatments. One of the most surprising results of such a transformation is the generation of large, extended monolayer precipitates, which are shown to represent the stable configuration of the precipitate system.
The Growth and Characterization of Epitaxial Fluoride Films on Semiconductors
Authors: Phillips Julia M. , Gibson J. M. 
Published: March 2011

ABSTRACTThis review considers the growth and characterization of epitaxial alkaline earth fluoride compounds on semiconductors. The field has developed quite rapidly in recent years, from the original demonstration of epitaxial growth in these systems to the investigation of the structure and properties of the layers. Two recent developments are reviewed in detail: the epitaxial relations which have been discovered between fluoride films and semiconductor substrates and the variety of interface structures which these systems display. These findings are beginning to lead to an understanding of the epitaxial growth process in these systems and how it relates to that in other more thoroughly studied systems.
Epitaxial Growth of Fluoride Films on Silicon Substrates
Authors: Ishiwara Hiroshi , Asano Tanemasa 
Published: March 2011

ABSTRACTGrowth conditions and structural properties of vacuumevaporated fluoride films on Si(lll) and (100) substrates are reviewed. It has been found that single crystal CaF2 films are grown on both (111) and (100) substrates at temperatures of 600–800°C and 500–600°C, respectively. It has also been found that SrF2 and BaF2 films of good crystalline quality are grown on Si(lll) at temperatures around 600°C, but that the films grown on Si(100) contain (111) oriented crystallites. In epitaxial growth of a Si/CaF2/Si structure, a novel growth method is presented, in which a thin Si layer is deposited at room temperature prior to deposition of a thick Si film at elevated temperature. Investigations on growth of mixed fluoride films, radiation damage in CaF2 films, and epitaxial relations in the fluoride/Si heterostructures are also presented.
On the Structure of Metal Silicide:Silicon Interfaces.
Authors: Cherns D. , Pond R.C. 
Published: March 2011

ABSTRACTA new crystallographic theory of interfacial structure is applied to the case of interfaces between NiSi2, CoSi2 and Pd2Si grown epitaxially on Si. In the case of NiSi2 layers grown in parallel orientation it is shown that dislocations with Burgers vectors ¼<111> separate energetically degenerate interfacial domains on {hko} interfaces. Observations, of such defects on (001) interfaces, using transmission electron microscopy, are presented and show detailed agreement with the theory.
Domain and Interface Structures of Epitaxial PtSi
Authors: Kawarada H. , Ohdomari I. , Horiuchi S. 
Published: March 2011

ABSTRACTThe crystalline perfection of epitaxial PtSi thin films and the microstructure of the PtSi/Si interface have been examined using transmission electron microscopy (TEM), including lattice image techniques. Epitaxial PtSi layers grow with domains which have three different positions on a (111) Si substrate. Inside a domain the crystalline perfection is high, and at the domain boundary no intermediate region has been observed. The undulation of the PtSi/Si interface is larger than that of other epitaxial silicide/Si interfaces. Despite the large undulation, a cross-sectional lattice image shows the epitaxial layer extends to the interface. The interface is abrupt in the epitaxial PtSi/Si system.
Grain boundary Diffusion of Ni through Pd2Si
Authors: Zingu E. C. , Mayer J. W. 
Published: March 2011

ABSTRACTInterdiffusion in the Si<100>/Pd2Si/Ni and Si<111>/Pd2Si/Ni thin film systems has been investigated using Rutherford backscattering spectrometry. Nickel is found to diffuse along the grain boundaries of polycrystalline Pd2Si upon which it accumulates at the Si<100>Pd2Si interface. The high mobility of Ni compared to that of si suggests that Pd diffuses faster than Si along the Pd2Si grain boundaries. An activation energy of 1.2 eV is determined for Ni grain boundary diffusion in Pd2Si.
Ion Channeling in Elastically Strained Superlattices
Authors: Barrett John H. 
Published: March 2011

ABSTRACTA review is given of the channeling behavior observed in superlattice materials. Elastic strains within the layers have been shown to be the source of the unusual ion dechanneling observed originally in InAs/GaSb and since observed in several other semiconductor superlattices. These strains occur because of the slight mismatch between the lattice constants of the two materials and cause the rows and planes of atoms in the crystal that are inclined to the surface normal to have small directional misalignments at the interfaces between the layers. The effects of these misalignments have been studied by computer simulations of ion trajectories in the crystal and shown to account in a reasonable manner for the observed dechanneling behavior. Calculations have been done as a function of the amount of misalignment to give an indication of how much dechanneling might be expected in other superlattices formed of any pair of materials that have slight mismatches. Various ways of measuring the amount of misalignment have also been studied by simulations and experiments.
Tetragonal Strain in MBE GexSi1-x Films Grown on (100) Si Observed by Ion Channeling and X-Ray Diffraction
Authors: Fiory A. T. , Feldman L. C. , Bean J. C. , Robinson I. K. 
Published: March 2011

ABSTRACTStructure of GexSi1-x alloy films grown on (100) Si by molecular beam epitaxy is analyzed by MeV He+ ion channeling and X-ray diffraction as functions of Ge concentration, film thickness and growth temperature. Critical thicknesses for pseudomorphic growth are determined for x ≤ 0.5, where coherent tetragonally-strained layers are observed. The average strain decreases approximately as the square-root of thickness when the critical thickness is exceeded. At temperatures near the threshold for islanding growth, surface roughness appears as a precursor to degradation of strained-layer epitaxy. No effect on the amount of the tetragonal strain was found in a study of ion-beam damage.