bluuebunny/crossref_metadata_2025_split huggingface dataset:
Plasticity of MoSi2 Below 900°C
Authors: Chang H. , Gibala R. 
Published: March 2011

AbstractThe mechanical behavior of polycrystalline MoSi2 tested in compression at temperatures from 750°C to 950°C has been investigated. This material can be deformed to several percent strain without fracture at temperatures as low as 900°C. This same material prestrained at 1300°C and subsequently tested at lower temperatures can be deformed to substantial strain at 800°C, and even exhibits modest plasticity at 750°C. Both prestrained and unprestrained materials exhibit microcracking combined with dislocation substructures containing high densities of dislocations. Unprestrained MoSi2 exhibits a yield point in this temperature range which does not exist when it is prestrained. The stress-strain curves of the prestrained material in this temperature range are similar qualitatively to those of the unprestrained material at 1100°C and above. These observations suggest that at these temperatures MoSi2 is a dislocation density limited material which can deform by dislocation plasticity processes if a sufficient dislocation density is available.
Microstructure and Mechanical Properties of Nitrided Molybdenum Silicide Coatings
Authors: Hirvonen J-P. , Suni I. , Kattelus H. , Lappalainen R. , Torri P. , Kung H. , Jervis T.R. , Nastasi M. 
Published: March 2011

AbstractMo-Si-N films with a high nitrogen concentration were produced by sputter-deposition in the presence of nitrogen plasma. The chemical composition was determined with Rutherford backscattering and nuclear reaction analysis. The ratio of Mo to Si was 1:2 in the coatings with a nitrogen concentration of 50 %. The microstructure of the as-deposited coatings on a silicon substrate was amorphous and no crystallization was found after annealing up to 1000 °C, although some relaxation was observed in X-ray diffraction. This was confirmed in highresolution transmission electron microscope examination. The hardness of the Mo-Si-N films was 18.8 GPa as determined with a nanoindenter. This is significantly higher than that of MoSi2 films, 11.2 GPa. The hardness of the Mo-Si-N films increased to 24.4 GPa after annealing at 800 °C, which is approximately the same as the hardness of the high-temperature tetragonal phase of MoSi2, 25.5 GPa. Similarly, the modulus of the as-deposited Mo-Si-N film was higher (257 GPa) than that of the MOSi2 film (222 GPa). However, only a slight increase in the modulus of the Mo-Si-N film was found after annealing at 800 °C, whereas the modulus of the crystallized tetragonal MoSi2 was 382 GPa. No cracking was found in the Mo-Si-N films even after annealing at 1000 °C.
High Temperature Silicide Thin-Film Thermocouples
Authors: Kreider Kenneth G. 
Published: March 2011

AbstractHigh-temperature silicides have been used in mechanical structures, heating elements, and electronic, CMOS applications. Their stability in high temperature oxidizing environments and excellent electrical conductivity may also make them useful as high temperature thin-film sensors in harsh environments. We have investigated sputter deposited MoSi2, ReSi2, TaSi2, TiSi2, and WSi2 thin films and characterized their performance as thermoelements and stability up to 1200 °C. A multilayer technique was developed to ensure constant silicide stoichiometry during oxidation thereby maintaining a constant Seebeck coefficient. In addition techniques were developed to suppress the formation of metal oxides from the silicides. The results indicated excellent stability of Seebeck coefficient up to 1200 °C. These results are compared with the problems of thin film instability in the Seebeck coefficient found in noble metal thermocouples. Potential applications for temperature and heat transfer measurements will be discussed.
Overview of High Temperature Structural Silicides
Authors: Petrovic J.J. , Vasudevan A.K. 
Published: March 2011

AbstractHigh temperature structural silicides represent an important new class of structural materials, with significant potential applications in the range of 1200-1600 °C under oxidizing and aggressive environments. Silicides, particularly those based on MoSi2, are considered to be promising due to their combination of high melting point, elevated temperature oxidation resistance, brittle-to-ductile transition, and electrical conductivity. Possible structural uses for silicides include their application as matrices in structural silicide composites, as reinforcements for structural ceramic matrix composites, as high temperature joining materials for structural ceramic components, and as oxidation-resistant coatings for refractory metals and carbon-based materials. The historical development of structural silicides, their potential applications, and important issues related to their use are discussed.
The Properties and Uses of Refractory Metals and Their Alloys
Authors: Briant C.L. 
Published: March 2011

AbstractThis paper reviews the problems that have limited the applications of refractory metals and their alloys. It also presents examples from recent work that has been done to overcome these problems. The work discussed concerns the refractory metals niobium, tantalum, molybdenum, and tungsten and alloys based on these elements. Recent results on intermetallic compounds that contain a refractory metal and composites that are made of refractory metals and their intermetallics are also presented.
Recent Advances and Developments in Refractory Alloys
Authors: Nieh T.G. , Wadsworth J. 
Published: March 2011

AbstractRefractory metal alloys based on Mo, W, Re, Ta, and Nb (Cb) find applications in a wide range of aerospace applications because of their high melting points and high-temperature strength. In this paper, we present recent progress in the understanding and applications of these alloys. Recent studies to improve the oxidation and mechanical behavior of refractory metal alloys, and particularly Nb alloys, will also be discussed. Some Re structures, for extremely high temperature applications (> 2000°C), made by CVD and P/M processes, are also illustrated. Interesting work on the development of new W alloys (W-HfC-X) and the characterization of some commercial refractory metals, e.g., K-doped W, TZM, and Nb-l%Zr, continues. Finally, recent developments in high temperature composites reinforced with refractory metal filaments, and refractory metal-based intermetallics, e.g., Nb3A1, Nb2Be17, and MoSi2, are briefly described.
Directional Solidification of Refractory Intermetallics: Single Crystals and Composites
Authors: Pope David P. , Shah Dilip M. , Romanow William , Huntley Mark 
Published: March 2011

AbstractDirectional solidification of intermetallic compounds using the optical imaging floating zone technique is discussed. The advantages and disadvantages of the technique are described, and the systems to which this technique has been applied are listed. Finally, application of the technique to growing in situ Cr2Nb/Nb composites is described. It is shown that well aligned, fine microstructures can be obtained using the technique. The aspect ratio of the Cr2Nb platelets is 200:1, or better, and are a few microns thick. The Cr2Nb has a strong <220> texture along the growth axis but the Nb is nearly random.
Investigation of B2 and Related Phases in Ti-Modified Nb-Al Alloys
Authors: Hou D.-H. , Yang S.S. , Shyue J. , Fraser H.L. 
Published: March 2011

AbstractThe B2 ordering and phase stability of three ordered intermetallic alloys with compositions (in at.%) of Nb-15Al-10Ti (10Ti alloy), Nb-15A1-40Ti (40Ti alloy), and Nb-15Al-25Ti (25Ti alloy) have been studied. All three alloys have the B2 crystal structure in the as-cast form. The Atom Location by Channeling Enhanced Microanalysis (ALCHEMI) technique has been employed to assess the site occupancy of these B2 alloys. The results of site occupancy are represented as Ordering Tie Lines on a ternary composition diagram. Various second phases were observed in heat treated samples. An ω-type phase was found in the 1OTi alloy in samples heat treated for 10 minutes and 4 hours at 900°C. At 800°C, orthorhombic phase was found in the 40Ti alloy while a three phase microstructure of o-phase/B2/A15 was observed in both the 10Ti and 25Ti alloys. Annealing at 1100°C leads to the dissolution of the o-phase and the presence of A15 phase in the 10Ti and 25Ti alloys, but no other phase in the 40Ti alloy. The observed phase equilibria in these alloys are compared with those in the literature.
Properties of Microlaminated Intermetallic-Refractory Metal Composites
Authors: Rowe R. G. , Skelly D. W. , Larsen M. , Heathcote J. , Lucas G. , Odette G. R. 
Published: March 2011

AbstractMicrolaminated composites of Nb3Al-Nb and Cr2Nb-Nb(Cr) were synthesized by high rate magnetron sputtering. Both composites were stable at elevated temperatures. A Cr2Nb-Nb(Cr) composite with 2 µm metal and intermetallic layers had room temperature tensile fracture strength over 725 MPa and a fracture toughness of about 20 MPa√m. Composites with 2 µm and 6 µm thick refractory metal and intermetallic laminations were compared and it was found that layer thickness did not affect fracture toughness. Microlaminates with the thicker 6 µm laminations had lower fracture strength, however. Good fracture strength and high fracture toughness indicated that microlaminated high temperature composites synthesized by vapor phase deposition exhibit the properties predicted by ductile toughening models.
Effects of Environmental Exposure on Ductile-Phase Toughening in Niobium Silicide-Niobium Composites
Authors: Rigney Joseph D. , Singh Preet M. , Lewandowski John J. 
Published: March 2011

AbstractA variety of materials have been toughened by incorporating ductile phases. Brittle silicide intermetallics such as Nb5Si3 composited with niobium particles incorporated during in situ processing techniques have realized significant improvements in toughness and stable crack extension. In the present work, toughness tests conducted on Nb5Si3/Nb materials monitored in a scanning electron microscope were instrumental in viewing the role of the deforming niobium particles on the process of toughening. In particular, the behavior of the ductile phase was monitored and related to the toughness values obtained. In an attempt to vary the behavior of the ductile phase, the composite materials were exposed to a variety of gaseous environments and subsequently tested in air. The resulting toughness, resistance-curve behavior, and in situ test results highlight the importance of the behavior of the ductile phase on subsequent properties.
Potassium in Grain Boundaries of Tungsten
Authors: Vukcevich Milan R. 
Published: March 2011

AbstractMost of the recent work on the role of potassium in tungsten wire deals with the origin of bubbles and their effect on the recrystallization process. Two very important areas are neglected: the effect of potassium strings on the mechanical properties of wire during manufacturing, and the differences in distribution of bubbles in the grain boundaries vs. the bulk. Although other advances in our understanding of potassium in tungsten are reviewed, the main attention is on these two neglected areas. Derived are expressions for the yield point of the fibrous wire structure, and for the increased concentration of bubbles in the transverse boundaries. The theory and experiments are in good agreement.
Various Properties of Sputtered TaxAl1-x Films
Authors: Minkiewicz V.J. , Moore J.O. , Keller G. , Woodman S.J. , Dobbertin D. , Savoy R. , Eldridge J.M. 
Published: March 2011

AbstractFilms of TaxxAl1-x have been prepared by diode sputtering from a target consisting of an Al mask placed on the face of a Ta target. The Ta target was 8″ in diameter while the Al mask was 0.125″ thick and machined with a grid-like shape. Films were deposited for a range of pressure, at a power of 300 watts, onto oxidized 100 mm diameter Si substrates that were placed on a planetary table beneath the target. The Al/Ta area ratio of the composite target was determined on the basis of the relative sputtering rates for these metals with the intent of producing a film composition with x = 0.5. The film composition was found to vary with argon pressure, going from 24 at.% Al at 4 mtorr to 72 at.% Al at 30 mtorr. This finding was quite unexpected. This result made it possible to deposit a wide range of film compositions from one composite target. The electrical resistivity has a broad maximum of,≈ 240 micro-ohm/cm between x=0.3 and 0.6. These results compliment and extend the earlier observations by Steidel \1] The as-deposited stress of the films varied from -400 to +150 MPa as x was decreased from 0.76 to 0.28. The temperature dependence of the film stress is hysteretic on the first cycle to 475 C. After the first cycle the films are driven more into tension by as much as 500 Mpa. The oxidation characteristics of one composition Ta0.66Al0.34 were characterized in some detail using a combination of electrical resistance, AES and XPS measurements. The results show that such films oxidize at temperatures in the 300 to 600C range via a diffusion-controlled process with an activation energy of 0.98 eV. Such films are substantially more oxidation-resistant than either ccα-or β-tantalum.
The Application of Reactive Hot Compaction and In-Situ Coating Techniques to Intermetallic Matrix Composites
Authors: Doty H. , Somerday M. , Abbaschian R. 
Published: March 2011

AbstractAn overview of the application of the reactive hot compaction (RHC) process to fabricate various intermetallics such as silicides and aluminides is presented. Specific examples with the in-situ formation of diffusion barrier coatings on refractory metal reinforcements during RHC are also given. The processing involves blending the elemental powders with pre-treated refractory metal filaments and reactively synthesizing the mixture at elevated temperatures. During this process, the treated surfaces of the filaments react with one of the components (e.g. Al for aluminides or Si for silicides) to form in-situ a protective surface coating. The important influence of the RHC reaction sequence and rate on the consolidation of the composite are discussed. Finally, the fracture toughness of the composites are related to the various toughening mechanisms, with special emphasis on the role of the interfacial layer.
Ge+ Preamorphization of Si: Effects of Dose and Very Low Temperature Thermal Treatment on Extended Defect Formation During Subsequent Spe
Authors: Myers E. , Rozgonyi G. A. , Sadana D. K. , Maszara W. , Wortman J. J. , Narayan J. 
Published: March 2011

ABSTRACTCross-section transmission electron microscopy (X-TEM) has been used to illustrate the amornhous/ crystalline (a/c) micromorphology dependence of various low dose Ge+ preamorphizatlon implants in Si. Ge+ Implants were done at room _emperature at energies of 150 and 300 keV in the dose range of 1 to 9E14 cm−2. These implants result in the formation of either a buried or a continuous amorphous layer, with rough a/c interfaces. Nucleation of spanning “hairpin” dislocations during subsequent solid phase epltaxy (SPE) regrowth is known to be related to rough a/c interface morphology. Very low temperature anneals (VLTA),less than 500°C where the rate of SPE is minimal, were utilized to sharpen rough a/c interfaces prior to subsequent SPE regrowth. Sharpening of rough a/c interfaces is shown to result from an unexpected reverse crystalline to amorphous phase transition. This reverse phase transition results in the dissolution of detached microcrystallltes located within the amorphous layer near the a/c interface. Utilization of VLTA interfacial smoothing prior to SPE regrowth therfore, results in the reduction of residual spanning “hairpin” dislocations along with homogenization of the amorphous material.
The Structure of Oxygen-Implanted (111) Silicon Before and After Heat-Pulse Annealing
Authors: Liliental-Weber Z. , Carpenter R. W. , Kelly J. C. 
Published: March 2011

ABSTRACTThe structure of (111) oriented, unheated oxygen-implanted silicon (dose -7.3×1016cm-2) has been studied by transmission electron microscopy (TEM). The as-implanted material exhibited four structurally different layers: defect-free monocrystaline silicon, amorphous silicon, monocrystalline silicon with a high defect density, and the perfect crystalline substrate. After heat-pulse annealing for 20s at 800°C, 900°C, or 1000°C, the amorphous layer recrystallized resulting in polycrystalline silicon, rich in oxygen. The uniform insulator buried layer was not formed under these specific implantation and annealing conditions.
Rapid Thermal Annealing of Al and P Implanted Single Crystal Beta Silicon Carbide Thin Films
Authors: Edmond J. A. , Kim H. J. , Davis R. F. 
Published: March 2011

ABSTRACTIon implantation of 27Al+ and 31p+ ions into monocrystalline s-SiC films was conducted in order to acquire p-type and n-type conducting layers, respectively. Implant energies ranging from 110 to 190 keV and fluences from 7 × 1013 to 9 × 1014 cm-2 were used. In order to activate each dopant specie, rapid thermal annealing (RTA) was employed. A decrease in sheet resistance with increasing annealing temperature for both type layers was observed up to 1800°C. After annealing at this highest temperature for 300 s in 1 atm. Ar, the percent of activated and ionized n-type and p-type dopant was ≅20% and ≅0.5%, respectively, as determined by room temperature capacitance-voltage measurements. Recrystallization of both heavily damaged and amorphized layers occurred as a result of the use of the aforementioned annealing process. Unlike SPE regrowth in other compound semiconductors, no microtwins were present in the regrown bulk as observed by XTEM. SIMS analyses also showed that there was essentially no redistribution of P and moderate redistribution of Al from the corresponding as-implanted profiles after annealing.
Deep Level Spectra of Ion-Implantation Defects and Slip Dislocations Introduced by CO2 Laser
Authors: Bao X. M. , Zhang X. Y. , Liu C. E. , Zheng X. Q. 
Published: March 2011

ABSTRACTThe CW CO2 laser annealing is an effective method for removing deep level defects induced by ion-implantation. The available laser density range is 350˜600 W/cm2, which is consistent with that needed to fully activate implanted impurities. At high power density (>600W/cm2 ) slip dislocations can be induced. The energy spectra of dislocations were measured with DLTS technique. One peak at Ev + 0.33eV in p-Si and two at peaks at Ec −0.37eV and Ec −0.50eV in n-Si have been found. These peaks are stable during thermal annealing at high temperature. But they can be passivated with hydrogen plasma annealing and reactivated by subsequent thermal annealing in vacuum. The dislocation core is reconstructed.
Comparison of Short Time Annealing of Implanted Silicon Layers With Tungsten-Halogen Lamp and Mercury Arc Lamp Sources
Authors: Wouters D. , Avau D. , Mertens P. , Maes H. E. 
Published: March 2011

ABSTRACTShort time anneal (STA) experiments were performed in a specially designed system which uses either a bank of Tungsten-Halogen lamps or a moving Mercury arc lamp as the light source. Both STA results were compared with conventional furnace anneal. The Mercury arc lamp anneal is found to be a critical process but optimization for wafer damage free conditions can be achieved. The anneals result in general in a better profile control which is most outspoken for shallow Boron implants while the electrical activation is comparable for all elements to that obtained with Tungsten-Halogen or furnace anneal.
Rapid Thermal Annealing of Ion Implanted p-n Junction in Silicon
Authors: Ho C. , Kwor R. , Araujo C. , Gelpey J. 
Published: March 2011

ABSTRACTThe rapid thermal annealing (RTA) of p+n and n+p diodes, fabricated by the LOCOS process, and its subsequent effects on junction leakage current, junction depth and dopant activation were investigated. The reverse bias diode leakage currents of implanted Si <100> samples (As+: 60 KeY, 5×1014 5×1015 cm−2, B+: 25 KeV, l×1014, l×1015 cm−2 and BF2+: 45 KeV, 1×1015cm−2 ) were measured as functions of annealing temperature, and dwell time. The annealing was performed using an Eaton RTA system (Nova ROA-400) at temperatures ranging from 950 °C to 1150 °C. Annealing times ranged from 0.2 sec. to 10 sec. The results from the diode leakage current analysis are correlated with those from Secondary Ion Mass Spectroscopy (SIMS) and differential Hall measurements. The reverse-biased leakage currents from the RTA-treated samples are compared with those from furnace-annealed samples.
Direct Silicidation of Co on Si by Rapid Thermal Annealing
Authors: Tabasky M. , Bulat E. S. , Ditchek B. M. , Sullivan M. A. , Shatas S. 
Published: March 2011

ABSTRACTRapid thermal annealing is used to form cobalt silicide directly on unimplanted as well as B, As, and P implanted wafers. The films are characterized by sheet resistance, X-ray diffraction, SEM, SIMS, and contact resistance measurements. The direct silicidation of cobalt on Si by rapid thermal annealing yields smooth, low resistivity films with minimal dopant redistribution.
Formation of Titanium Nitride/Silicide Bilayers by Rapid Thermal Anneal in Nitrogen
Authors: Morgan A. E. , Broadbent E. K. , Reader A. H. 
Published: March 2011

ABSTRACTSputter deposited Ti films on Si and SiO2 substrates have been rapid thermal annealed in N2 at temperatures of 400–1100°C, and the reaction followed using AES, TEM, electron diffraction and sheet resistance measurements. The Ti initially becomes contaminated with oxygen before being nitrided at the surface and silicided at the interface. The oxygen is expelled from the siuicide and a TiNxO1−x/TiSix bilayer eventually results. With Si substrates, TiNxO1−x is much the thinner layer whereas the reverse is true on SiO2. Extended annealing in N2 completely converts the TiSi2 layer on Si into TiN.
Stability of Heavily Doped Si Formed by As+ Implantation and Rapid Thermal Annealing
Authors: Numan Muhammad Z. , Lu Z. H. , Chu W. K. , Fathy D. , Wortman J. J. 
Published: March 2011

ABSTRACTDeactivation of ion implanted and rapid thermal annealed (RTA) metastable arsenic in silicon during subsequent furnace annealing has been studied by sheet resistance measurement, Rutherford backs cat t ering/ channeling (RBS), and transmission electron microscopy (TEM). Following RTA, thermal annealing induces deactivation of the dopant which increases the sheet resistivity monotonically with temperature for a very short time, Dislocation loops are formed near the peak of As concentration at post-anneal temperatures of 750°C or higher, where deactivation rate is fast. At lower temperatures deactivation is accompanied by displacement of As atoms, possibly forming clusters.
SiO2 Growth and Annealing by Lamp heating
Authors: Weinberg Z. A. , Nguyen T. N. , Cohen S. A. , Kalish R. 
Published: March 2011

ABSTRACTThis paper reports the results of a study of thin SiO2 growth and annealing in a lamp heater (Heatpulse). Good quality 5–10 mn SiO2 films on silicon have been obtained. For good oxides the average destructive breakdown- field was 13 MV/cm and very few or no low-field breakdowns were found. The breakdown statistics were obtained with Al gate capacitors and by a current staircase-ramp technique which is described in the paper. Processing with a single oxidation step, oxidationannealing, and oxidation-annealing-oxidation are discussed.
Transient Thermal Processing of GaAs
Authors: Pearton S. J. , Gibson J. M. , Jacobson D. C. , Poate J. M. , Williams J. S. , Boerma D. O. 
Published: March 2011

ABSTRACTA comprehensive review is presented of the use of transient thermal processing for the activation of implanted dopants, the alloying of ohmic contacts, the pulse diffusion of Zn for p+ contacts, and other heat treatments of GaAs. In all cases, transient processing produces results at least as good as furnace heating, and in some instances, markedly better. The special needs of GaAs, such as encapsulation of the wafer surface, and prevention of slip and warpage are discussed, as well as recent results detailing implant damage removal processes during transient annealing.