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Sample records for mo-si mo-ge w-si

  1. Commensurate vortex lattices and oscillation effects in superconducting Mo/Si and W/Si multilayers

    NASA Astrophysics Data System (ADS)

    Mikhailov, M. Yu.; Yuzephovich, O. I.; Bomze, Yu. V.; Buchstab, E. I.; Fogel, N. Ya.

    2005-03-01

    We report experimental results of a vortex lattice structure investigation in artificial superconducting Mo/Si and W/Si superlattices. Resistance R and critical current Ic measurements in parallel magnetic fields are performed as well as measurements in tilted magnetic fields. At temperatures where the condition of strong layering is satisfied the dependences Ic(H∥) and R(H∥) exhibit oscillatory behavior. It is shown that the appearance of oscillations and of reentrant behavior (vanishing of the resistivity in definite ranges of H∥) are due to the strong intrinsic pinning and to the effect of commensurability between the vortex lattice period and multilayer wavelength. The locations of Ic(H∥) and R(H∥) extrema correspond to the stable states of a commensurate vortex lattice. Our experimental data are in good quantitative agreement with the Ivlev, Kopnin, and Pokrovsky (IKP) theory. It is shown that the values of the commensurability fields depend exclusively on the superlattice period s and anisotropy coefficient γ and do not depend on the type of materials used for multilayer preparation. A memory effect, i.e., dependence of the oscillation pattern on the magnetic history of the sample, is observed. It is shown experimentally that the state of the vortex matter in the layered superconductors is essentially different from that of type-II superconductors with a random distribution of the pinning centers. Investigation of oscillation and reentrance behavior may be used as a new tool for the study of the vortex lattice arrangement in layered superconductors. The essential advantage of this method is connected with its simplicity and with the possibility of using it in arbitrary large fields. Investigations of the commensurate states may be used for rather precise determination of the anisotropy coefficient γ.

  2. Elastic moduli of MoSi sub 2 -based materials

    SciTech Connect

    Srinivasan, S.R.; Schwarz, R.B. )

    1992-07-01

    We prepared MoSi{sub 2}, two-phase MoSi{sub 2}/Mo{sub 5}Si{sub 3}, and (Mo,W)Si{sub 2} solid-solution alloy powders by mechanically alloying mixtures of elemental molybdenum, silicon, and tungsten. These powders were consolidated by hot-pressing them at 1500 {degree}C in graphite dies. We measured the elastic moduli of these alloys by a recently developed technique for non-contact ultrasonic spectroscopy. Second-phase Mo{sub 5}Si{sub 3} additions to MoSi{sub 2} result in decreased values for {ital G} and {ital E}, whereas alloying MoSi{sub 2} with WSi{sub 2} results in increased values for {ital G} and {ital E}. An analysis of these Young's moduli and of data from the literature for various intermetallic alloys suggests that for any given alloy system, the Young's moduli for its various intermetallics as a function of density fall on a straight line. Further, the lines for the different alloy systems are approximately parallel.

  3. MoSi2-Base Composites

    NASA Technical Reports Server (NTRS)

    Hebsur, Mohan G.

    2003-01-01

    Addition of 30 to 50 vol% of Si3N4 particulate to MoSi2 eliminated its low temperature catastrophic failure, improved room temperature fracture toughness and the creep resistance. The hybrid composite SCS-6/MoSi2-Si3N4 did not show any matrix cracking and exhibited excellent mechanical and environmental properties. Hi-Nicalon continuous fiber reinforced MoSi2-Si3N4 also showed good strength and toughness. A new MoSi2-base composite containing in-situ whisker-type (Beta)Si3N4 grains in a MoSi2 matrix is also described.

  4. Mechanical behavior of MoSi{sub 2} and MoSi{sub 2} composites

    SciTech Connect

    Petrovic, J.J.

    1994-06-01

    MoSi{sub 2} is a key member of the new class high temperature structural silicide materials. Important features of the mechanical behavior of MoSi{sub 2} and MoSi{sub 2} composites are reviewed. The mechanical properties of MoSi{sub 2} single crystals, polycrystalline MoSi{sub 2}, and MoSi{sub 2}-based composites are discussed in association with properties such as elevated temperature deformation and low temperature fracture toughness. Interrelationships between single crystal, polycrystal, and composite mechanical behavior are identified.

  5. Mo-Si alloy development

    SciTech Connect

    Liu, C.T.; Heatherly, L.; Wright, J.L.

    1996-06-01

    The objective of this task is to develop new-generation corrosion-resistant Mo-Si intermetallic alloys as hot components in advanced fossil energy conversion and combustion systems. The initial effort is devoted to Mo{sub 5}-Si{sub 3}-base (MSB) alloys containing boron additions. Three MSB alloys based on Mo-10.5Si-1.1B (wt %), weighing 1500 g were prepared by hot pressing of elemental and alloy powders at temperatures to 1600{degrees}C in vacuum. Microporosities and glassy-phase (probably silicate phases) formations are identified as the major concerns for preparation of MSB alloys by powder metallurgy. Suggestions are made to alleviate the problems of material processing.

  6. Preparation and Characterization of (Mo, W)Si2-SiC Composites by In Situ Microwave Reaction Sintering

    NASA Astrophysics Data System (ADS)

    Wu, Haijiang; Chen, Fang; Xu, Jianguang

    2017-07-01

    MoSi2-based materials are considered potentially useful for making high-temperature structural parts. In this work, (Mo, W)Si2-SiC composites have been successfully prepared in situ by microwave reaction sintering of the elemental reactants. Benefiting from the lower sintering temperature and faster densification procedure, the as-prepared composites have finer microstructures compared to the analogs prepared by conventional reaction sintering, resulting in a significant improvement of mechanical properties. The flexural strength, Vickers hardness and fracture toughness of 10%SiC/10%WSi2/80%MoSi2 are as high as 302.81 MPa, 8.55 GPa and 8.90 MPa m1/2, respectively, which are also better than those of monolithic MoSi2 and 10%SiC/90%MoSi2 composite due to the synergistic strengthening and toughening effects of W alloying and SiC second phase.

  7. Combustion synthesis of a complex composite based on MoSi[sub 2

    SciTech Connect

    Subrahmanyam, J.; Mohan Rao, R.; Somaraju, K. . Combustion Synthesis Group)

    1994-11-15

    Self-propagating High-temperature Synthesis (SHS), also known as combustion synthesis, is gaining importance as a technique for producing powders and near net shape components of metals, intermetallics, ceramics and their composites. The agglomeration of reinforcement particles and their non-uniform distribution, which are often attributed to the poor strength of MoSi[sub 2] composites can be avoided in this process. SHS is capable of producing composites with a homogeneous distribution of fine reinforcements in a single step. MoSi[sub 2] has been produced by SHS earlier. The authors have reported the combustion synthesis of MoSi[sub 2]-SiC composites and MoSi[sub 2]-WSi[sub 2] alloys. In this paper, combustion synthesis of a complex composite, namely (Mo,W)Si[sub 2]-SiC, starting from elemental powders by the thermal explosion mode is reported. In the thermal explosion mode of SHS, a volumetric reaction occurs in the reactant compact when it is rapidly heated to the ignition temperature.

  8. Growth Kinetics and Microstructure Evolution of Intermediate Phases in MoSi2-Si3N4-WSi2/Mo Diffusion Couples

    NASA Astrophysics Data System (ADS)

    Zhang, Houan; Huang, Yu; Lin, Jia; Chen, Ying; Gu, Siyong

    2016-12-01

    The growth kinetics and silicon diffusion coefficients of intermediate silicide phases in MoSi2-3.5 vol.% Si3N4-5.0 vol.% WSi2/Mo diffusion couple prepared by spark plasma sintering were investigated in temperatures ranging from 1200 to 1500 °C. The intermediate silicide phases were characterized by x-ray diffraction. The microstructures and components of the MoSi2-Si3N4-WSi2/Mo composites were investigated using scanning electron microscope with energy-dispersive spectroscopy. A special microstructure with MoSi2 core surrounded by a thin layer of (Mo,W)Si2 ring was found in the MoSi2-Si3N4-WSi2 composites. The intermediate layers of Mo5Si3 and (Mo,W)5Si3 in the MoSi2-Si3N4-WSi2/Mo diffusion couples were formed at different diffusion stages, which grew parabolically. Activation energy of the growth of intermediate layers in MoSi2-3.5 vol.% Si3N4-5.0 vol.% WSi2/Mo diffusion couple was calculated to be 316 ± 23 kJ/mol. Besides, the hindering effect of WSi2 addition on the growth of intermediate layers was illustrated by comparing the silicon diffusion coefficients in MoSi2-3.5 vol.% Si3N4-5.0 vol.% WSi2/Mo and MoSi2-3.5 vol.% Si3N4/Mo diffusion couples. MoSi2-3.5 vol.% Si3N4-5.0 vol.% WSi2 coating on Mo substrate exhibited a better high-temperature oxidation resistance in air than that of MoSi2-3.5 vol.% Si3N4 coating.

  9. Growth Kinetics and Microstructure Evolution of Intermediate Phases in MoSi2-Si3N4-WSi2/Mo Diffusion Couples

    NASA Astrophysics Data System (ADS)

    Zhang, Houan; Huang, Yu; Lin, Jia; Chen, Ying; Gu, Siyong

    2017-02-01

    The growth kinetics and silicon diffusion coefficients of intermediate silicide phases in MoSi2-3.5 vol.% Si3N4-5.0 vol.% WSi2/Mo diffusion couple prepared by spark plasma sintering were investigated in temperatures ranging from 1200 to 1500 °C. The intermediate silicide phases were characterized by x-ray diffraction. The microstructures and components of the MoSi2-Si3N4-WSi2/Mo composites were investigated using scanning electron microscope with energy-dispersive spectroscopy. A special microstructure with MoSi2 core surrounded by a thin layer of (Mo,W)Si2 ring was found in the MoSi2-Si3N4-WSi2 composites. The intermediate layers of Mo5Si3 and (Mo,W)5Si3 in the MoSi2-Si3N4-WSi2/Mo diffusion couples were formed at different diffusion stages, which grew parabolically. Activation energy of the growth of intermediate layers in MoSi2-3.5 vol.% Si3N4-5.0 vol.% WSi2/Mo diffusion couple was calculated to be 316 ± 23 kJ/mol. Besides, the hindering effect of WSi2 addition on the growth of intermediate layers was illustrated by comparing the silicon diffusion coefficients in MoSi2-3.5 vol.% Si3N4-5.0 vol.% WSi2/Mo and MoSi2-3.5 vol.% Si3N4/Mo diffusion couples. MoSi2-3.5 vol.% Si3N4-5.0 vol.% WSi2 coating on Mo substrate exhibited a better high-temperature oxidation resistance in air than that of MoSi2-3.5 vol.% Si3N4 coating.

  10. Mo-Si-B Alloy Development

    SciTech Connect

    Schneibel, J.H.; Kruzie, J.J.; Ritchie, R.O.

    2003-04-24

    Mo-Si-B silicides consisting of the phases {alpha}-Mo (Mo solid solution), Mo{sub 3}Si, and Mo{sub 5}SiB{sub 2} have melting points on the order of 2000 C and have potential as ultra-high temperature structural materials. Mo-Si-B alloys can be processed such that the {alpha}-Mo is present in the form of isolated particles in a silicide matrix, or as a continuous matrix ''cementing'' individual silicide particles together. The latter microstructure is similar to that of WC-Co hard metals. This paper focuses on the relationship between the topology as well as scale of the microstructure of Mo-Mo{sub 3}Si-Mo{sub 5}SiB{sub 2} alloys, and their creep strength and fracture toughness. For example, the creep strength of Mo-Si-B alloys is improved by reducing the {alpha}-Mo volume fraction and by making the {alpha}-Mo phase discontinuous. The fracture toughness is improved by increasing the {alpha}-Mo volume fraction and by making the {alpha}-Mo phase continuous. Room temperature stress intensity factors as high as 21 MPa m{sup 1/2} were obtained. The room temperature fracture toughness of Mo-Si-B alloys can also be improved by microalloying with Zr. The room temperature ductility of Mo itself can be improved by adding MgAl{sub 2}O{sub 4} spinel particles suggesting yet another way to improve the ductile phase toughening of Mo-Si-B alloys.

  11. Comparison of lithographic performance between MoSi binary mask and MoSi attenuated PSM

    NASA Astrophysics Data System (ADS)

    Yamana, Mitsuharu; Lamantia, Matthew; Philipsen, Vicky; Wada, Shingo; Nagatomo, Tatsuya; Tonooka, Yoji

    2009-04-01

    The mask error budget continues to shrink with shrinking DRAM half pitch and MPU gate size year by year. The ITRS roadmap calls for mask CDU to be cut in half by 2014[1]. Both mask maker and mask user must take advantage of various mask properties, OPC strategies and resolution enhancement techniques to drive improvements. Mask material selection impacts both lithographic performance and mask manufacturability. In turn mask material properties and manufacturing techniques impact our ability to meet the technology roadmap. Studies have shown the advantages of polarized light[2,3] as well as the impact of various mask materials on high NA lithography[4]. In this paper we select the recently introduced binary mask material made from a MoSi absorber called Opaque MoSi On Glass (OMOG) for comparison with the conventional 6% att. PSM and 20% att. MoSi PSM. Through simulation and wafer prints, we optimized mask feature from viewpoint of MEEF and maximum exposure latitude (EL). The MoSi att. PSMs suffer from higher MEEF, which is attributed to the negative effect of TE polarization for mask duty cycle of 50% for 50 nm half pitch and below. Therefore a lower mask duty cycle is required for att. PSM to bring the MEEF performance back to acceptable levels. Experimental results confirm simulation results. As a result of the lower mask duty cycle, the att. MoSi PSMs exhibit poor Sub Resolution Assist Feature (SRAF) printability. On the contrary, the MoSi binary mask delivers both acceptable MEEF and acceptable SRAF printing performance. Moreover, we found that the mask structure impact of OMOG to wafer CD is smallest among three masks. OMOG gives the best combination of lithographic performance and delivery compared to the MoSi att. PSMs.

  12. Sonochemical Synthesis of Molybdenum Disilicide (MoSi2).

    DTIC Science & Technology

    2007-11-02

    Two successful solution phase synthesis methods were developed for the preparation of Nanocrystalline MoSi particles. The first method consisted of...ignition at approximately 500 deg C that resulted in the evolution of SiCl4 and the formation of MoSi crystallites. Nanoparticles were compacted using a

  13. A perspective on MoSi sub 2 based composites

    SciTech Connect

    Petrovic, J.J. ); Vasudevan, A.K. )

    1992-01-01

    MoSi{sub 2} based composites represent an important new class of high temperature structural silicides,'' with significant potential for elevated temperature structural applications in the range of 1200--1600{degrees}C in oxidizing and aggressive environments. The properties of MoSi{sub 2} which make it an attractive matrix for high temperature composites are described and the development history of these materials traced. Latest results on elevated temperature creep resistance, low temperature fracture toughness, and composite oxidation behavior are summarized. Important avenues for future MoSi{sub 2} based composite development are suggested.

  14. Adsorption of oxygen atom on MoSi2 (110) surface

    NASA Astrophysics Data System (ADS)

    Sun, S. P.; Li, X. P.; Wang, H. J.; Jiang, Y.; Yi, D. Q.

    2016-09-01

    The adsorption energy, structural relaxation and electronic properties of oxygen atom on MoSi2 (110) surface have been investigated by first-principles calculations. The energetic stability of MoSi2 low-index surfaces was analyzed, and the results suggested that MoSi2 (110) surface had energetically stability. The site of oxygen atom adsorbed on MoSi2 (110) surface were discussed, and the results indicated that the preference adsorption site of MoSi2 (110) surface for oxygen atom was H site (hollow position). Our calculated work should help to understand further the interaction between oxygen atoms and MoSi2 surfaces.

  15. Mo-Si-B-Based Coatings for Ceramic Base Substrates

    NASA Technical Reports Server (NTRS)

    Perepezko, John Harry (Inventor); Sakidja, Ridwan (Inventor); Ritt, Patrick (Inventor)

    2015-01-01

    Alumina-containing coatings based on molybdenum (Mo), silicon (Si), and boron (B) ("MoSiB coatings") that form protective, oxidation-resistant scales on ceramic substrate at high temperatures are provided. The protective scales comprise an aluminoborosilicate glass, and may additionally contain molybdenum. Two-stage deposition methods for forming the coatings are also provided.

  16. MoSi2-Base Composite for Engine Applications

    NASA Technical Reports Server (NTRS)

    Hebsur, Mohan G.; Nathal, Michael V.

    1997-01-01

    The intermetallic compound MoSi2 has long been known as a high temperature material that has excellent oxidation resistance and electrical/thermal conductivity. Also its low cost, high melting point (2023 C), relatively low density (6.2 g/cm versus 8 g/cm for current engine materials), and ease of machining make it an attractive structural material. However, the use of MoSi2 has been hindered because of the brittle nature of the material at low temperatures, inadequate creep resistance at high temperatures, accelerated oxidation (also known as 'pest' oxidation) at temperatures between approximately 400 and 500 C, and a coefficient of thermal expansion (CTE) that is relatively high in comparison to potential reinforcing fibers such as SiC. This CTE mismatch between the fiber and the matrix resulted in severe matrix cracking during thermal cycling.

  17. Silicide layer growth rates in Mo/Si multilayers

    SciTech Connect

    Rosen, R.S.; Stearns, D.G. ); Viliardos, M.A.; Kassner, M.E. ); Vernon, S.P. ); Cheng, Y. )

    1993-12-01

    The thermal stability of sputter-deposited Mo/Si multilayers was investigated by annealing studies at relatively low temperatures ([similar to]250--350 [degree]C) for various times (0.5--3000 h). Two distinct stages of thermally activated Mo/Si interlayer growth were found: a primary surge, followed by a (slower) secondary steady-state growth in which the interdiffusion coefficient is constant. The interdiffusion coefficients for the interlayer formed by deposition of Mo-on-Si are higher than those of the interlayer formed by deposition of Si-on-Mo. Assuming that the activation energy is constant, an extrapolation of our results to ambient temperature finds that interlayer growth is negligible, suggesting long-term thermal stability in soft-x-ray projection lithography applications.

  18. Anisotropy of heat conduction in Mo/Si multilayers

    SciTech Connect

    Medvedev, V. V.; Yakshin, A. E.; Kruijs, R. W. E. van de; Bijkerk, F.; Yang, J.; Schmidt, A. J.; Zoethout, E.

    2015-08-28

    This paper reports on the studies of anisotropic heat conduction phenomena in Mo/Si multilayers with individual layer thicknesses selected to be smaller than the mean free path of heat carriers. We applied the frequency-domain thermoreflectance technique to characterize the thermal conductivity tensor. While the mechanisms of the cross-plane heat conduction were studied in detail previously, here we focus on the in-plane heat conduction. To analyze the relative contribution of electron transport to the in-plane heat conduction, we applied sheet-resistance measurements. Results of Mo/Si multilayers with variable thickness of the Mo layers indicate that the net in-plane thermal conductivity depends on the microstructure of the Mo layers.

  19. Environmentally Resistant Mo-Si-B-Based Coatings

    NASA Astrophysics Data System (ADS)

    Perepezko, J. H.; Sossaman, T. A.; Taylor, M.

    2017-06-01

    High-temperature applications have demonstrated aluminide-coated nickel-base superalloys to be remarkably effective, but are reaching their service limit. Alternate materials such as refractory (e.g., W, Mo) silicide alloys and SiC composites are being considered to extend high temperature capability, but the silica surfaces on these materials require coatings for enhanced environmental resistance. This can be accomplished with a Mo-Si-B-based coating that is deposited by a spray deposition of Mo followed by a chemical vapor deposition of Si and B by pack cementation to develop an aluminoborosilica surface. Oxidation of the as-deposited (Si + B)-pack coatings proceeds with partial consumption of the initial MoSi2 forming amorphous silica. This Si depletion leads to formation of a B-saturated Mo5Si3 (T1) phase. Reactions between the Mo and the B rich phases develop an underlying Mo5SiB2 (T2) layer. The T1 phase saturated with B has robust oxidation resistance, and the Si depletion is prevented by the underlying diffusion barrier (T2). Further, due to the natural phase transformation characteristics of the Mo-Si-B system, cracks or scratches to the outer silica and T1 layers can be repaired from the Si and B reservoirs of T2 + MoB layer to yield a self-healing characteristic. Mo-Si-B-based coatings demonstrate robust performance up to at least 1700 °C not only to the rigors of elevated temperature oxidation, but also to CMAS attack, hot corrosion attack, water vapor and thermal cycling.

  20. MoSi absorber photomask for 32nm node

    NASA Astrophysics Data System (ADS)

    Konishi, Toshio; Kojima, Yosuke; Takahashi, Hiroyuki; Tanabe, Masato; Haraguchi, Takashi; Lamantia, Matthew; Fukushima, Yuichi; Okuda, Yoshimitsu

    2008-05-01

    The development of semiconductor process for 32nm node is in progress. Immersion lithography has been introduced as an extension of 193nm lithograpy. In addition, DPL (Double patterning lithography) is becoming a strong candidate of next generation lithography. The extension of optical lithography increases more mask complexity and tighter specification of photomasks. CD performance is the most important issue in the advanced photomask technology. However, it is expected that conventional mask cannot satisfy the required mask specifications for 32nm node and beyond. Most of CD errors are contributed to the dry etching process. Mask CD variation is greatly influenced by the loading effect from dry etching of the absorber. As the required accuracy of the mask arises, Cr absorber thickness has been gradually thinner. CD linearity with the thinner Cr absorber thickness has better performance. However, it is difficult to apply thinner Cr absorber thickness simply under the condition of OD > 3, which is needed for wafer printing. So, we adopted MoSi absorber instead of conventional Cr absorber, because MoSi absorber has less micro and global loading effect than that of Cr absorber. By using MoSi absorber, we can reduce Cr thickness as a hardmask. The thinner Cr hardmask allows for reduce resist thickness and become same condition for conventional EB resist lithography. The lithography performances were confirmed by the simulation and wafer printing. The new MoSi absorber mask behaves similar to the conventional Cr absorber mask. The adoption of super thin Cr as a hardmask made it possible to reduce resist thickness. By the application of the thin resist and the latest tools, we'll improve the mask performance to meet the 32 nm generation specification.

  1. MoSi2-Base Structural Composite Passed Engine Test

    NASA Technical Reports Server (NTRS)

    Nathal, Michael V.; Hebsur, Mohan G.

    1999-01-01

    The intermetallic compound molybdenum disilicide (MoSi2) is an attractive high-temperature structural material for advanced engine applications. It has excellent oxidation resistance, a high melting point, relatively low density, and high thermal conductivity; and it is easily machined. Past research at the NASA Lewis Research Center has resulted in the development of a hybrid composite consisting of a MoSi2 matrix reinforced with silicon nitride (Si3N4) particulate and silicon carbide (SiC) fibers. This composite has demonstrated attractive strength, toughness, thermal fatigue, and oxidation resistance, including resistance to "pest" oxidation. These properties attracted the interest of the Office of Naval Research and Pratt & Whitney, and a joint NASA/Navy/Pratt & Whitney effort was developed to continue to mature the MoSi2 composite technology. A turbine blade outer air seal, which was part of the Integrated High Performance Turbine Engine Technology (IHPTET) program, was chosen as a first component on which to focus.

  2. MoSi2-Base Hybrid Composites from Aeroengine Applications

    NASA Technical Reports Server (NTRS)

    Hebsur, Mohan G.

    2000-01-01

    Addition of about 30 to 50 vol % of Si3N4 particulate to MoSi2 improved low temperature accelerated oxidation resistance by forming a Si2ON2 protective scale and thereby eliminated catastrophic 'pest failure'. The Si3N4 addition also improved the high temperature creep strength by nearly five orders of magnitude, doubled the room temperature toughness, and significantly lowered the CTE of the MoSi2 which eliminated matrix cracking in SCS-6 reinforced composites even after thermal cycling. The SCS-6 fiber reinforcement improved the room temperature fracture toughness by seven times and impact resistance by five times. The composite exhibited this excellent strength and toughness improvement up to 1673 K. More recently, tape casting was adopted as the preferred processing of MoSi2-base composites due to improved fiber spacing, ability to use small diameter fibers, and for lower cost. Good strength and toughness values were also obtained with fine diameter Hi-Nicalon tow fibers. These hybrid composites remain competitive with ceramic matrix composites as a replacement for Ni-base superalloys in aircraft engine applications.

  3. Effects of Mo/Si Ratio Inversion on the Oxidation of Nb-Cr-Mo-Si-B Alloys

    NASA Astrophysics Data System (ADS)

    Thomas, Kathryn S.; Varma, Shailendra K.

    2015-11-01

    The effect of inverting the Mo/Si ratio on the oxidation of two boron-containing alloys has been studied in air for temperatures 700-1400°C. The compositions of the alloys in atomic percent are Nb-25Cr-20Mo-15Si-15B, Nb-25Cr-20Mo-15Si-10B, Nb-25Cr-15Mo-20Si-10B, and Nb-25Cr-15Mo-20Si-15B hereafter referred to as 10B, 15B, 2010, and 2015 alloys, respectively. The as-cast microstructure of the alloys contains a mixture of NbCr2 Laves phase, Nb5Si3 silicide, and additionally Nb3Si silicide for the Mo/Si modified alloys. Primary oxides developed for all alloys are CrNbO4, Nb2O5, and SiO2. Improvements in high-temperature oxidation have been seen for the Mo/Si-modified 15B containing alloy under cyclic testing. Samples have shown similar oxidation responses in both long-term static and cyclic oxidation for 168-h exposures up to 1300°C. Characterization of oxide products was done by x-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy.

  4. MoSi2-Base Hybrid Composite Passed Engine Test

    NASA Technical Reports Server (NTRS)

    Keith, Theo G., Jr.; Hebsur, Mohan

    1998-01-01

    The intermetallics compound molybdenum disilicide (MoSi2) is an attractive high-temperature structural material for advanced engine applications. It has excellent oxidation resistance, a high melting point, relatively low density, and high thermal conductivity, and it is easily machined. Past research'at the NASA Lewis Research Center has resulted in the development of a hybrid composite consisting of a MoSi2 matrix reinforced with silicon nitride (Si3N4) Particulate and silicon carbide (SiC) fibers. This composite has demonstrated attractive strength, toughness, thermal fatigue, and oxidation resistance, including resistance to "pest" oxidation. These properties attracted the interest of the Office of Naval Research and Pratt & Whitney, and a joint NASA/Navy/Pratt & Whitney effort was developed to continue to mature the MoSi2 Composite technology. A turbine blade outer air seal, which was part of the Integrated High Performance Turbine Engine Technology (IHPTET) program, was chosen as a first component on which to focus. The first tasks of the materials development effort were to develop improved processing methods to reduce costs and to use fine-diameter fibers that enable the manufacturing of complex shapes. Tape-casting methods were developed to fully infiltrate the fine SiC fibers with matrix powders. The resulting composites were hot pressed to 100-percent density. Composites with cross-plied fiber architectures with 30 vol. % hi-nicalon SiC fibers and 30 vol. % nitride particles are now made routinely and demonstrate a good balance of properties. The next task entailed the measurement of a wide variety of mechanical properties to confirm the suitability of this composite in engines. In particular, participants in this effort demonstrated that composites made with Hi-Nicalon fibers had strength and toughness properties equal to or better than those of the composites made with the large-diameter fibers that had been used previously. Another critically

  5. Recovery of Mo/Si multilayer coated optical substrates

    DOEpatents

    Baker, Sherry L.; Vernon, Stephen P.; Stearns, Daniel G.

    1997-12-16

    Mo/Si multilayers are removed from superpolished ZERODUR and fused silica substrates with a dry etching process that, under suitable processing conditions, produces negligible change in either the substrate surface figure or surface roughness. The two step dry etching process removes SiO.sub.2 overlayer with a fluroine-containing gas and then moves molybdenum and silicon multilayers with a chlorine-containing gas. Full recovery of the initial normal incidence extreme ultra-violet (EUV) reflectance response has been demonstrated on reprocessed substrates.

  6. Recovery of Mo/Si multilayer coated optical substrates

    DOEpatents

    Baker, S.L.; Vernon, S.P.; Stearns, D.G.

    1997-12-16

    Mo/Si multilayers are removed from superpolished ZERODUR and fused silica substrates with a dry etching process that, under suitable processing conditions, produces negligible change in either the substrate surface figure or surface roughness. The two step dry etching process removes SiO{sub 2} overlayer with a fluroine-containing gas and then moves molybdenum and silicon multilayers with a chlorine-containing gas. Full recovery of the initial normal incidence extreme ultra-violet (EUV) reflectance response has been demonstrated on reprocessed substrates. 5 figs.

  7. Characterization of Mo/Si multilayer growth on stepped topographies

    SciTech Connect

    Boogaard, A. J. R. vcan den; Louis, E.; Zoethout, E.; Goldberg, K. A.; Bijkerk, F.

    2011-08-31

    Mo/Si multilayer mirrors with nanoscale bilayer thicknesses have been deposited on stepped substrate topographies, using various deposition angles. The multilayer morphology at the stepedge region was studied by cross section transmission electron microscopy. A transition from a continuous- to columnar layer morphology is observed near the step-edge, as a function of the local angle of incidence of the deposition flux. Taking into account the corresponding kinetics and anisotropy in layer growth, a continuum model has been developed to give a detailed description of the height profiles of the individual continuous layers. Complementary optical characterization of the multilayer system using a microscope operating in the extreme ultraviolet wavelength range, revealed that the influence of the step-edge on the planar multilayer structure is restricted to a region within 300 nm from the step-edge.

  8. Pressureless sintering of MoSi{sub 2} materials

    SciTech Connect

    Scholl, R.; Juengling, T.; Kieback, B. |

    1995-07-01

    Various powder mixtures were prepared by a modified mechanical alloying technique. Starting from elemental Mo-, Si and C-powders the influence of milling conditions on phase formation during the milling process and the subsequent beat treatment was investigated. Phase formation during sintering and sintering kinetics of activated starting mixtures were studied by differential scanning calorimetry (DSC), thermal graphimetry (TG), X-ray diffraction (XRD) and dilatometry. The results show that phase formation during milling or sintering strongly depends on milling conditions. Optimized powder mixtures of single phase and reinforced molybdenum silicides show high densities up to 98.5% TD by pressureless sintering in various atmospheres. Full density is possible by post-HIP because the samples show only closed porosity. The microstructure was studied in dependence of sintering parameters. The level of impurities, i.e. C, O{sub 2} was determined. Hardness, fracture toughness and bending strength were measured for single phase and particle reinforced materials.

  9. Interdiffusion in W/Si Multilayers with Boron Carbide Interlayers

    SciTech Connect

    Potdar, Satish; Gupta, M.; Gupta, A.; Schneider, M.; Stahn, J.

    2011-07-15

    W/Si multilayers with B{sub 4}C as a diffusion barrier were deposited using ion beam sputtering technique. It was found that incorporation of B{sub 4}C at both interfaces of Si enhances the reflectivity of the multilayer. Though the interface of W/Si or W/B{sub 4}C has been studied in literature, what happens at Si/B{sub 4}C interfaces is largely unknown. This is primarily due to absence of contrast between Si/B{sub 4}C for x-rays. For neutrons there is significant contrast between Si and B{sub 4}C, therefore we used neutron reflectivity to study thermal stability of Si/B{sub 4}C multilayers. It was found that up to an annealing temperature of 573 K, the multilayer remains intact however at higher temperature interdiffusion starts.

  10. First-principles study of the interfacial adhesion between Si O2 and Mo Si2

    NASA Astrophysics Data System (ADS)

    Jiang, D. E.; Carter, Emily A.

    2005-10-01

    Upon oxidation, a silica scale forms on MoSi2 , a potential high-temperature coating material for metals. This silica scale protects MoSi2 against high-temperature corrosive gases or liquids. We use periodic density functional theory to examine the interface between SiO2 and MoSi2 . The interfacial bonding is localized, as evidenced by an adhesion energy that changes only slightly with the thickness of the SiO2 layer. Moreover, the adhesion energy displays a relatively large (0.40J/m2) variation with the relative lateral position of the SiO2 and MoSi2 lattices due to changes in Si-O bonding across the interface. The most stable interfacial structure yields an ideal work of adhesion of 5.75J/m2 within the local density approximation ( 5.02J/m2 within the generalized-gradient approximation) to electron exchange and correlation, indicating extremely strong adhesion. Local densities of states and electron density difference plots demonstrate that the interfacial Si-O bonds are covalent in character. Mo-O interactions are not found in the SiO2/MoSi2 interface investigated here. Our work predicts that the SiO2 scale strongly adheres to MoSi2 , and further supports the potential of MoSi2 as a high-temperature structural material and coating.

  11. Aperiodic Mo/Si multilayers for hard x-rays

    DOE PAGES

    Pardini, Tom; Alameda, Jennifer; Platonov, Yuriy; ...

    2016-08-04

    In this work we have developed aperiodic Molybdenum/Silicon (Mo/Si) multilayers (MLs) to reflect 16.25 keV photons at a grazing angle of incidence of 0.6° ± 0.05°. To the best of our knowledge this is the first time this material system has been used to fabricate aperiodic MLs for hard x-rays. At these energies new hurdles arise. First of all a large number of bilayers is required to reach saturation. This poses a challenge from the manufacturing point of view, as thickness control of each ML period becomes paramount. The latter is not well defined a priori, due to the thicknessmore » of the interfacial silicide layers which has been observed to vary as a function of Mo and Si thickness. Additionally an amorphous-to-crystalline transition for Mo must be avoided in order maintain reasonably low roughness at the interfaces. This transition is well within the range of thicknesses pertinent to this study. Despite these difficulties our data demonstrates that we achieved reasonably flat ML response across the angular acceptance of ± 0.05°, with an experimentally confirmed average reflectivity of 28%. Such a ML prescription is well suited for applications in the field of hard x-ray imaging of highly diverging sources.« less

  12. Aperiodic Mo/Si multilayers for hard x-rays

    SciTech Connect

    Pardini, Tom; Alameda, Jennifer; Platonov, Yuriy; Robinson, Jeff; Soufli, Regina; Spiller, Eberhard; Walton, Chris; Hau-Riege, Stefan P.

    2016-08-04

    In this work we have developed aperiodic Molybdenum/Silicon (Mo/Si) multilayers (MLs) to reflect 16.25 keV photons at a grazing angle of incidence of 0.6° ± 0.05°. To the best of our knowledge this is the first time this material system has been used to fabricate aperiodic MLs for hard x-rays. At these energies new hurdles arise. First of all a large number of bilayers is required to reach saturation. This poses a challenge from the manufacturing point of view, as thickness control of each ML period becomes paramount. The latter is not well defined a priori, due to the thickness of the interfacial silicide layers which has been observed to vary as a function of Mo and Si thickness. Additionally an amorphous-to-crystalline transition for Mo must be avoided in order maintain reasonably low roughness at the interfaces. This transition is well within the range of thicknesses pertinent to this study. Despite these difficulties our data demonstrates that we achieved reasonably flat ML response across the angular acceptance of ± 0.05°, with an experimentally confirmed average reflectivity of 28%. Such a ML prescription is well suited for applications in the field of hard x-ray imaging of highly diverging sources.

  13. Oxidation of Nb particulate-reinforced MoSi sub 2

    SciTech Connect

    Meschter, P.J. )

    1991-01-01

    This paper reports on molybdenum disilicide (MoSi{sub 2}) which is a promising high-temperature material because of its moderate density (6.31 g cm{sup {minus}3}), high melting temperature (2020 {degrees}C), ductility above 900-1000{degrees} C related to its b.c.c.-like C11b crystal structure, and excellent high-temperature oxidation resistance. MoSi{sub 2} is brittle below 900-1000{degrees} C and hence must be reinforced to obtain acceptable low-temperature toughness. Addition of a ductile reinforcement such as Nb as wire or particulate has been shown to increase the ambient-temperature toughness of MoSi{sub 2}. Additions of Nb, which oxidizes rapidly to form non-protective Nb{sub 2}O{sub 5}, may degrade the oxidation resistance of an MoSi{sub 2}-matrix composite. The purpose of this research is to determine the effect of particulate Nb additions on the oxidation resistance of MoSi{sub 2} in the high-temperature regime ({ge}550{degrees} C), where a protective SiO{sub 2} product layer is formed on monolithic MoSi{sub 2}, and in the low-temperature regime (400-500{degrees} C), where Mo and Si oxidize simultaneously.

  14. Abrasive wear behavior of MoSi(2)-SiC Composites

    SciTech Connect

    Alman, David E.; Hawk, Jeffrey A.; Petrovic, J.J.; Henager, C.H., Jr.; Singh, M.

    1998-01-01

    This paper investigates the influence of SiC volume fraction and composite processing route on the abrasive wear behavior of MoSi sub 2 -SiC composites. The MoSi sub 2 -SiC (10-67 vol%) particulate composites were produced by: (i) the conventional hot-pressing of mixtures of MoSi sub 2 powders and SiC whiskers; and (ii) through the solid-state displacement reaction between Mo sub 2 C and Si powders to form MoSi sub 2 and SiC during hot-pressing. A MoSi sub 2 -80 vol% SiC composite was also produced by the reactive melt infiltration of a carbon preform with a molten Si-Mo alloy. The incorporation of SiC into a MoSi sub 2 matrix is an effective way to enhance wear resistance, provided the composites are processed to as near full density as possible.

  15. Toughness of dense MoSi sub 2 and MoSi sub 2 /tantalum composites produced by low pressure plasma deposition

    SciTech Connect

    Castro, R.G.; Rollett, A.D.; Stanek, P.W. ); Smith, R.W. )

    1992-01-15

    The thrust to develop new high temperature materials for advanced aircraft turbine engines has focused on composite systems based on metal-matrix, ceramic-matrix, intermetallic matrix and carbon-carbon composites. For the case of intermetallic matrix composites, candidate materials such as aluminides and silicides have been identified as potential materials due to their excellent oxidation resistance at high temperatures. More specific to the class of silicides, is molybdenum disilicide (NoSi{sub 2}), which has been used as a high melting intermetallic (2030 {degrees} C) for more than eighty years. One of the properties which has discouraged the application of MoSi{sub 2}, as well as other intermetallic compounds, is the inherent lack of ductility at low to intermediate temperatures. Plasma spraying as a means of fabricating composite structures of metals has been addressed recently by a number of researchers. In this paper the use of low pressure plasma deposition (LPPD) for producing spray deposits of MoSi{sub 2} and MoSi{sub 2} with a 20 volume fraction of tantalum is investigated. Initial results focusing on the as-deposited densities and fracture toughness of the spray deposited material are compared to those properties measured on conventionally hot pressed MoSi{sub 2}. Effects of post consolidation on fracture toughness of the spray deposits are also addressed.

  16. Reaction synthesis of MoSi sub 2 from high purity elemental powders

    SciTech Connect

    Hardwick, D.A.; Martin, P.L.; Moores, R.J. )

    1992-08-15

    This paper reports that Molybdenum disilicide (MoSi{sub 2}) is an intermetallic compound that combines a high melting point (2293K) with excellent resistance to high temperature oxidation. With respect to mechanical properties the behavior of polycrystalline MoSi{sub 2} falls into one of three regimes, based on the sue temperature: t {lt} 925{degrees} C: strong + brittle; 925 {lt} T {lt} 1250{degrees} C:strong + ductile and T {gt} 1250{degrees} C:weak + ductile. The majority of recent investigations have focused on the properties of MoSi{sub 2}-based materials processed from commercially available powder. Commercial MoSi{sub 2} powder contains significant amounts of oxygen; for example, a chemical analysis of powder obtained from Cerac Inc. revealed an oxygen content of 0.6 wt%. Consolidation of such powder resulted in a substantial volume fraction of amorphous silica in the final product. MoSi{sub 2} powder produced by the crushing and grinding of arc-melted elemental Mo and Si also exhibited amorphous Si-rich particles after vacuum hot-pressing at 1973K and 30MPa. Grinding of the cast material to powder was done in ethanol but one this was driven off, the powder was air-handled. The high energy mechanical alloying in an argon atmosphere of elemental Mo and Si powder to produce MoSi{sub 2} has also been investigated. Following hot pressing, the MoSi{sub 2} made in this fashion still contained a substantial volume fraction of SiO{sub 2}.

  17. Thermoelectric properties of bulk MoSi2 synthesized by solid state microwave heating

    NASA Astrophysics Data System (ADS)

    Lan, Yu; Xie, Mianyu; Ouyang, Ting; Yue, Song

    2016-07-01

    In this research, single phase α-MoSi2 was prepared by solid state hybrid microwave heating within 90 min at relatively low temperature 1273 K. Such precursor powders were then ball milled and sintered by microwave heating at different temperatures. The thermoelectric (TE) properties of MoSi2 bulks were investigated in the temperature range of 300-673 K. When the sintering temperature increases from 973 K to 1273 K, the electrical resistivity decreases significantly and the Seebeck coefficients increase obviously, leading to the maximum TE powder factor of 6.2 × 10-6Wm-1K-2 at 673 K. These results demonstrate the feasibility of high efficient and economical synthesis of MoSi2 by microwave heating technique, with the final products having comparable TE performance in comparison to those from typical methods with long duration and energy-extensive consumption.

  18. Creep behavior of MoSi{sub 2}-SiC composites

    SciTech Connect

    Butt, D.P.; Maloy, S.A.; Kung, H.; Korzekwa, D.A.; Petrovic, J.J.

    1993-12-31

    Using a cylindrical indenter, indentation creep behavior of hot pressed and HIPed MoSi{sub 2}-SiC composites containing 0--40% SiC by volume, was characterized at 1000--1200C, 258--362 MPa. Addition of SiC affects the creep behavior of MoSi{sub 2} in a complex manner by pinning grain boundaries during pressing, thus leading to smaller MoSi{sub 2} grains; by obstructing or altering both dislocation motion and grain boundary sliding; and by increasing the overall yield stress of the material. Comparisons are made between indentation and compressive creep studies. It is shown that under certain conditions, compressive creep and indentation creep measurements yield comparable results after correcting for effective stresses and strain rates beneath the indenter.

  19. In-situ synthesis and rapid consolidation of fully dense MoSi[sub 2

    SciTech Connect

    Raman, R.V.; Rele, S.V.; Paskowitz, M.J. )

    1993-01-01

    Molybdenum disilicide (MoSi[sub 2]) is emerging as a high-temperature material of significant technical interest because of its unique combination of high-temperature oxidation resistance, outstanding corrosion resistance, and high melting point. Its outstanding oxidation resistance is due to the formation of a glassy silica phase on the surface that acts as a protective layer at higher temperatures. However, a number of issues impede the use of MoSi[sub 2] in structural applications. Above the brittle-to-ductile transition temperature, MoSi[sub 2] behaves as a metal but loses strength and undergoes creep and plastic deformation. Synthesis of MoSi[sub 2] is an expensive and lengthy process involving sintering or hot pressing in high-temperature furnaces. Such processing unavoidably results in the formation of a grain-boundary silica phase that degrades the mechanical properties at both ambient and elevated temperatures. Conventional processing techniques, such as hot pressing and hot isostatic pressing (HIPing), require expensive dies, canning materials, long cycle times, and are not cost-effective or energy efficient. Extended high-temperature exposure during processing results in a less-than-optimum microstructure. MoSi[sub 2] also pests, disintegrating rapidly during oxidation at temperatures around 500[degrees]C. However, pesting does not occur in materials with a density greater than 98% of the theoretical. To overcome some of the drawbacks of high processing costs and long processing times, the use of self-propagating, high-temperature synthesis (SHS) to fabricate MoSi[sub 2] from elemental molybdenum and silicon powders has been explored. An advantage of the SHS process is that higher phase purities compared to conventional synthesis are achieved. However, porosity values of up to 50% persist in SHS-processed samples.

  20. SiC reinforced-MoSi sub 2 based matrix composites

    SciTech Connect

    Petrovic, J.J.; Honnell, R.E.

    1990-01-01

    SiC reinforced-MoSi{sub 2} based matrix composites possess very significant potential as high temperature structural materials for temperatures above 1200{degree}C in oxidizing environments, due to their combination of oxidation resistance, thermodynamic stability, machinability, elevated temperature ductility and strength, and ability to alloy the MoSi{sub 2} matrix with other silicides. The fabrication, microstructures, oxidation, and mechanical properties of these materials are described, and their current properties are compared to high temperature metals and structural ceramics. 22 refs., 5 figs., 2 tabs.

  1. Nanoscale mapping of the W/Si(001) Schottky barrier

    SciTech Connect

    Durcan, Chris A.; Balsano, Robert; LaBella, Vincent P.

    2014-07-14

    The W/Si(001) Schottky barrier was spatially mapped with nanoscale resolution using ballistic electron emission microscopy (BEEM) and ballistic hole emission microscopy (BHEM) using n-type and p-type silicon substrates. The formation of an interfacial tungsten silicide is observed utilizing transmission electron microscopy and Rutherford backscattering spectrometry. The BEEM and BHEM spectra are fit utilizing a linearization method based on the power law BEEM model using the Prietsch Ludeke fitting exponent. The aggregate of the Schottky barrier heights from n-type (0.71 eV) and p-type (0.47 eV) silicon agrees with the silicon band gap at 80 K. Spatially resolved maps of the Schottky barrier are generated from grids of 7225 spectra taken over a 1 μm × 1 μm area and provide insight into its homogeneity. Histograms of the barrier heights have a Gaussian component consistent with an interface dipole model and show deviations that are localized in the spatial maps and are attributed to compositional fluctuations, nanoscale defects, and foreign materials.

  2. Fabrication of Ta2O5 Dispersion-Strengthened Mo-Si-B Alloy by Powder Metallurgical Method

    NASA Astrophysics Data System (ADS)

    Byun, Jong Min; Choi, Won June; Bang, Su-Ryong; Park, Chun Woong; Do Kim, Young

    2017-01-01

    In this study, we investigate the effect of oxide dispersion strengthening on mechanical properties by dispersion of nano-sized Ta2O5 particles in Mo-Si-B alloy. A Mo-Si-B core-shell powder consisting of two intermetallic compounds of Mo5SiB2 and Mo3Si as the core and nano-sized Mo solid solution surrounding intermetallic compounds was fabricated by chemical vapor transport. And Mo-Si-B core-shell powder with uniformly dispersed nano-sized Ta2O5 particles on the surface of a Mo solid solution shell was produced by a wet blending process with TaCl5 solution and heat treatment. Then, pressureless sintering was performed at 1400°C for 3 h under a H2 atmosphere. The hardness and fracture toughness of the Ta2O5-dispersed Mo-Si-B alloy were measured using Vickers hardness and 3-point bending tests, respectively. The Vickers hardness and fracture toughness of the fabricated Mo-Si-B-Ta2O5 alloy were more improved than that of the Mo-Si-B alloy fabricated using core-shell powder with no addition of Ta2O5 particles (Mo-Si-B alloy: 353 Hv, 13.5 MPa·√m, Mo-Si-B-Ta2O5 alloy: 509 Hv, 15.1 MPa·√m).

  3. Evaluation of Mo-SiO{sub 2} continuous FGM`s. Final report

    SciTech Connect

    Tomsia, A.P.; Cannon, R.M.; McNaney, J.M.; Ishibashi, H.; Saiz, E.; MoberlyChan, W.; Becker, T.J.; Ritchie, R.O.

    1997-09-01

    The TOTO sponsored program at LBL involved characterization of continuous Mo-SiO{sub 2} FGMs in terms of microstructure, mechanical and thermal properties and corrosion resistance which would relate to the steady state, high temperature performance as well as the heating and cooling transients that occur at the beginning and end of operation in various applications.

  4. Synthesis and densification of MoSi{sub 2} by self-propagating high-temperature synthesis

    SciTech Connect

    Gi-Wook Lee, Hyun-Woo Lee, Yong-Seog Kim

    1995-12-31

    The possibility of producing dense MoSi{sub 2} by the thermal explosion mode of Self-propagating High-temperature Synthesis(SHS) was demonstrated. It was shown that the density of MoSi{sub 2} produced by SHS process without applied pressure can be increased by a proper combination of processing parameters such as heating rate, addition of alloying elements, processing atmosphere, and Mo and Si powder sizes used. The heating rate and alloying elements were found to influence the density Of MoSi{sub 2} formed the most. Proper combinations of the processing is parameter yielded MoSi{sub 2} with density close to 90% theoretical density which comparable to pressurelessly sintered MoSi{sub 2}.

  5. Characterization of electrical resistivity as a function of temperature in the Mo-Si-B system

    SciTech Connect

    Beckman, Sarah E.

    1999-12-10

    Measurements of electrical resistivity as a function of temperature from 25 to 1,500 C were conducted on polycrystalline samples in the Mo-Si-B system. Single phase, or nearly single phase, samples were prepared for the following phases: Mo3Si, Mo5SiB2, Mo5Si3Bx, MoB, MoSi2, and Mo5Si3. Thesis materials all exhibit resistivity values within a narrow range(4--22 x 10-7Ω-m), and the low magnitude suggests these materials are semi-metals or low density of states metals. With the exception of MoSi2, all single phase materials in this study were also found to have low temperature coefficient of resistivity(TCR) values. These values ranged from 2.10 x 10-10 to 4.74 x 10-10Ω-m/° C, and MoSi2 had a TCR of 13.77 x 10-10Ω-m/° C. The results from the single phase sample measurements were employed in a natural log rule-of-mixtures model to relate the individual phase resistivity values to those of multiphase composites. Three Mo-Si-B phase regions were analyzed: the binary Mo5Si3-MoSi2 system, the ternary phase field Mo5Si3BxMoB-MoSi2, and the Mo3Si-Mo5SiB2-Mo5Si3Bx ternary region. The experimental data for samples in each of these regions agreed with the natural log model and illustrated that this model can predict the electrical resistivity as a function of temperature of multi-phase, sintered samples within an error of one standard deviation.

  6. Mechanically Activated Combustion Synthesis of MoSi2-Based Composites

    SciTech Connect

    Shafirovich, Evgeny

    2015-09-30

    The thermal efficiency of gas-turbine power plants could be dramatically increased by the development of new structural materials based on molybdenum silicides and borosilicides, which can operate at temperatures higher than 1300 °C with no need for cooling. A major challenge, however, is to simultaneously achieve high oxidation resistance and acceptable mechanical properties at high temperatures. One approach is based on the fabrication of MoSi2-Mo5Si3 composites that combine high oxidation resistance of MoSi2 and good mechanical properties of Mo5Si3. Another approach involves the addition of boron to Mo-rich silicides for improving their oxidation resistance through the formation of a borosilicate surface layer. In particular, materials based on Mo5SiB2 phase are promising materials that offer favorable combinations of high temperature mechanical properties and oxidation resistance. However, the synthesis of Mo-Si-B multi-phase alloys is difficult because of their extremely high melting temperatures. Mechanical alloying has been considered as a promising method, but it requires long milling times, leading to large energy consumption and contamination of the product by grinding media. In the reported work, MoSi2-Mo5Si3 composites and several materials based on Mo5SiB2 phase have been obtained by mechanically activated self-propagating high-temperature synthesis (MASHS). Short-term milling of Mo/Si mixture in a planetary mill has enabled a self-sustained propagation of the combustion front over the mixture pellet, leading to the formation of MoSi2-T1 composites. Combustion of Mo/Si/B mixtures for the formation of T2 phase becomes possible if the composition is designed for the addition of more exothermic reactions leading to the formation of MoB, TiC, or TiB2. Upon ignition, Mo/Si/B and Mo/Si/B/Ti mixtures exhibited spin combustion, but the products were porous, contained undesired secondary phases, and had low oxidation resistance. It has been shown that use of

  7. Application of EB repair for high durable MoSi PSM

    NASA Astrophysics Data System (ADS)

    Kanamitsu, Shingo; Morishita, Keiko; Hirano, Takashi

    2014-07-01

    Recently there has been a demand for high durability MoSi masks. There are some candidates for MoSi mask materials. They are preferable for both mask user and mask manufacture because they show not only high durability against exposure or cleaning process but also process compatibility in production line[1]. They are gaining momentum to practical application. However, there is a drawback for manufacturing regarding the mask repair process. Because ebeam repair employs pure chemical reaction, it faces severe etching difficulty due to higher chemical stability. Meanwhile, the tool supplier has looked into that chemical reaction in detail since the problem was unveiled. They developed a dedicated etching process for high durable materials. It's so important for the mask manufacturer to evaluate this process properly before they transfer conventional MoSi to new high durability MoSi. A comprehensive understanding of this new process should be acquired by trying several kinds of etching tests. In this paper we will report the results ranging from basic etching rate, selectivity, repair accuracy to flexibility for complicated shaped defects. This data tells us a lot about if it can be applied for practical use. The experiment was performed with e-beam repair tool "MeRiTⓇ", which was released as the latest version from ZEISS last year. An improved new etching process was applied to "A6L2" type high durable blanks provided by HOYA corporation. A wide variety of programmed defects were arranged on a line and space featured test mask. These programmed defects were repaired with the procedure developed by ZEISS. After repair, printed image was evaluated by AIMSTM system. This paper will discuss the initial results of these first steps into the uncharted territory of high durability MoSi repair.

  8. Activated combustion features in the Mo-Si-C-promoter system and synthesis of MoSi{sub 2}-SiC composite powders

    SciTech Connect

    Hambartsumyan, A.A. Harutyunyan, A.B.

    2007-12-04

    Opportunities on combustion synthesizing the MoSi{sub 2}-SiC ceramic composites in a wide range of compositions under the chemical activated mode were studied. Molybdenum, silicon powders and carbon black were used as initial reagents, and Teflon was used as an activating additive. It was established that Teflon displays a dual (kinetic and thermal) impact on the interaction between reagents. The phasic character of the combustion process evolution, being characterized by low- and high-temperature regimes, was revealed. The end-products were subjected to SEM, XRD and chemical analyses.

  9. Processing and Properties of SiC/MoSi2-SiC Composites Fabricated by Melt Infiltration

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.; Hebsur, Mohan G.

    2000-01-01

    Hi-Nicalon SiC fiber reinforced MoSi2-SiC matrix composites (SiC/MoSi2-SiC) have been fabricated by the melt infiltration approach. The composite consists of approximately 60 vol%, 2-D woven BN/SiC coated Hi-Nicalon SiC fibers and approximately 40 vol% MoSi2-SiC matrix. The room temperature tensile properties and thermal conductivity of the SiC/MoSi2-SiC composites were measured and compared with those of the melt infiltrated SiC/SiC composites. The influence oi fiber architecture on tensile properties was also evaluated. Results indicate that the primary modulus, stress corresponding to deviation from linearity, and transverse thermal conductivity values for the SiC/MoSi2-SiC composites are significantly lower than those for the SiC/SiC composites. Microcracking of the matrix due to the large difference in thermal expansion between MoSi2 and SiC appears to be the reason for the lower matrix dominated properties of SiC/MoSi2-SiC composites.

  10. Oxidation and interdiffusion behavior of Niobium substrate coated MoSi2 coating prepared by spark plasma sintering

    NASA Astrophysics Data System (ADS)

    Yan, JianHui; Wang, Yi; Liu, LongFei; Wang, Yueming

    2014-11-01

    In order to protect Niobium material from oxidation, MoSi2 coating was prepared on the Niobium substrate by spark plasma sintering. Oxidation behavior of MoSi2 coating was investigated in air over the temperature range of 1200-1500 °C. The interfacial diffusion between MoSi2 coating and Niobium substrate was also examined. Dense MoSi2 coating was successfully prepared using spark plasma sintering. The porosities of top and side coatings are about 5.5% and 6.4%, respectively. No cracks were present in the MoSi2 coating. Cracking and spallation of the SiO2 scale did not occur at test temperatures. Two intermediate phases-(Nb,Mo)5Si3 and Nb5Si3 phases, were detected in the boundary of MoSi2 coating and Nb substrate. The growth of the reaction layer was dominated by the diffusion of Si toward the Nb substrate and obeyed a parabolic rate law. A multi-layered structural coating formed on Nb substrate, which consisted of MoSi2, (Mo,Nb)5Si3 and Nb5Si3 in turn.

  11. Effect of carbon addition on elevated temperature crack growth resistance in (Mo,W)Si[sub 2]-SiC[sub p] composite

    SciTech Connect

    Ramamurty, U. . Division of Engineering); Suresh, S. . Dept. of Materials Science and Engineering); Petrovic, J.J. . Materials Science and Technology Division)

    1994-10-01

    Experimental results on subcritical crack growth behavior of hot-pressed MoSi[sub 2]-50 mol% WSi[sub 2] alloy reinforced with 30 vol% SiC particles in the temperature range 1,200--1,300 C are presented. The effect of 2 wt % C addition on the stable crack growth resistance of this composite was investigated under both static and cyclic loading conditions. The results indicate that the addition off carbon to the composite improves the subcritical crack growth resistance under both static and cyclic loads and increases the elevated temperature capabilities of the (Mo, W) Si[sub 2] composite. Increasing the temperature from 1,200 to 1,300 C is found to increase the crack growth velocities with a concomitant decrease in the crack growth initiation thresholds. Electron microscopy of the crack-tip region indicates that the stable crack growth process is influenced primarily by interfacial cavitation. At 1,300 C, deformation processes such as twinning of the SiC particles and dislocation motion within the matrix grains appear to play an active role in determining the crack growth kinetics. The role of glassy phase in influencing the high-temperature fracture behavior and its implications for design of the microstructure of the brittle materials are discussed.

  12. Reticle blanks for extreme ultraviolet lithography: Ion beam sputter deposition of low defect density Mo/Si multilayers

    SciTech Connect

    Vernon, S.P.; Kania, D.R.; Kearney, P.A.; Levesque, R.A.; Hayes, A.V.; Druz, B.; Osten, E.; Rajan, R.; Hedge, H.

    1996-06-24

    We report on growth of low defect density Mo/Si multilayer (ML) coatings. The coatings were grown in a deposition system designed for EUVL reticle blank fabrication. Complete, 81 layer, high reflectance Mo/Si ML coatings were deposited on 150 mm dia (100) oriented Si wafer substrates using ion beam sputter deposition. Added defects, measured by optical scattering, correspond to defect densities of 2x10{sup -2}/cm{sup 2}. This represents a reduction in defect density of Mo/Si ML coatings by a factor of 10{sup 5}.

  13. Oxidation Behavior and Chlorination Treatment to Improve Oxidation Resistance of Nb-Mo-Si-B Alloys

    SciTech Connect

    Behrani, Vikas

    2004-01-01

    This thesis is written in an alternate format. The thesis is composed of a general introduction, two original manuscripts, and a general conclusion. References cited within each chapter are given at the end of each chapter. The general introduction starts with the driving force behind this research, and gives an overview of previous work on boron doped molybdenum silicides, Nb/Nb5Si3 composites, boron modified niobium silicides and molybdenum niobium silicides. Chapter 2 focuses on the oxidation behavior of Nb-Mo-Si-B alloys. Chapter 3 contains studies on a novel chlorination technique to improve the oxidation resistance of Nb-Mo-Si-B alloys. Chapter 4 summarizes the important results in this study.

  14. Isothermal and cyclic oxidation resistance of pack siliconized Mo-Si-B alloy

    NASA Astrophysics Data System (ADS)

    Majumdar, Sanjib

    2017-08-01

    Oxidation behaviour of MoSi2 coated Mo-9Si-8B-0.75Y (at.%) alloy has been investigated at three critical temperatures including 750, 900 and 1400 °C in static air. Thermogravimetric analysis (TGA) data indicates a remarkable improvement in the oxidation resistance of the silicide coated alloy in both isothermal and cyclic oxidation tests. The cross-sectional scanning electron microscopy and energy dispersive spectroscopic analysis reveal the occurrence of internal oxidation particularly at the crack fronts formed in the outer MoSi2 layer during thermal cycling. The dominant oxidation mechanisms at 750-900 °C and 1400 °C are identified. Development of MoB inner layer further improves the oxidation resistance of the silicide coated alloy.

  15. NaF-assisted combustion synthesis of MoSi2 nanoparticles and their densification behavior

    NASA Astrophysics Data System (ADS)

    Nersisyan, Hayk H.; Lee, Tae Hyuk; Ri, Vladislav; Lee, Jong Hyeon; Suh, Hoyoung; Kim, Jin-Gyu; Son, Hyeon Taek; Kim, Yong-Ho

    2017-03-01

    The exothermic reduction of oxides mixture (MoO3+2SiO2) by magnesium in NaF melt enables the synthesis of nanocrystalline MoSi2 powders in near-quantitative yields. The combustion wave with temperature of about 1000-1200 °C was recorded in highly diluted by NaF starting mixtures. The by-products of combustion reaction (NaF and MgO) were subsequently removed by leaching with acid and washing with water. The as-prepared MoSi2 nanopowder composed of spherical and dendritic shape particles was consolidated using the spark plasma sintering method at 1200-1500 °C and 50 MPa for 10 min. The result was dense compacts (98.6% theoretical density) possessing submicron grains and exhibiting hardness of 8.74-12.92 GPa.

  16. Investigation into the joining of MoSi{sub 2} to 316L stainless steel

    SciTech Connect

    Vaidya, R.U.; Bartlett, A.H.; Conzone, S.D.; Butt, D.P.

    1996-10-01

    Partial transient liquid phase joining and low temperature brazing were applied in joining MoSi{sub 2} to 316L ss. Exploratory studies were carried out on various interlayer materials. Mechanical, physical, and chemical compatibilities between various interlayers, brazing material, and substrate materials were investigated. Effect of thermal expansion mismatch between various components of the joint on the overall joint integrity was also studied. Preliminary findings are outlined.

  17. MoSi 2 Oxidation in 670-1498 K Water Vapor

    DOE PAGES

    Sooby Wood, Elizabeth; Parker, Stephen S.; Nelson, Andrew T.; ...

    2016-03-08

    Molybdenum disilicide (MoSi2) has well documented oxidation resistance at high temperature (T > 1273 K) in dry O2 containing atmospheres due to the formation of a passive SiO2 surface layer. But, its behavior under atmospheres where water vapor is the dominant species has received far less attention. Oxidation testing of MoSi2 was performed at temperatures ranging from 670–1498 K in both 75% water vapor and synthetic air (Ar-O2, 80%–20%) containing atmospheres. Here the thermogravimetric and microscopy data describing these phenomena are presented. Over the temperature range investigated, MoSi2 displays more mass gain in water vapor than in air. The oxidationmore » kinetics observed in water vapor differ from that of the air samples. Two volatile oxides, MoO2(OH)2 and Si(OH)4, are thought to be the species responsible for the varied kinetics, at 670–877 K and at 1498 K, respectively. Finally, we observed an increase in oxidation (140–300 mg/cm2) from 980–1084 K in water vapor, where passivation is observed in air.« less

  18. Extended Functionality of Environmentally-Resistant Mo-Si-B-Based Coatings

    NASA Astrophysics Data System (ADS)

    Perepezko, J. H.; Sakidja, R.

    2013-02-01

    Multiphase Mo-Si-B alloys with compositions which yield the ternary intermetallic Mo5SiB2 (T2) phase as a key microstructure constituent together with the Mo and Mo3Si phases, offer an attractive balance of high melting temperature, oxidation resistance, and mechanical properties. The investigation of reaction kinetics involving the T2 phase enables the analysis of oxidation in terms of diffusion pathways and the design of effective coatings. From this basis, kinetic biasing is used together with pack cementation to develop Mo-Si-B-based multilayered coatings with an aluminoborosilica surface and in situ diffusion barriers with self-healing characteristics for enhanced oxidation resistance. While a combustion environment contains water vapor that can accelerate an attack of silica-based coatings, the Mo-Si-B-based coatings provide oxidation resistance in water vapor up to at least 1,500°C. An exposure to hot ionized gas species generated in an arc jet confirms the robust coating performance in extreme environments. To extend the application beyond Mo-based systems, a two-stage process has been implemented to provide effective oxidation resistance for refractory metal cermets, SiC and ZrB2 ultra-high-temperature composites.

  19. Microstructure and wear behavior of Cu-Mo-Si coatings by laser cladding

    NASA Astrophysics Data System (ADS)

    Peilei, Zhang; Xiaopeng, Liu; Yunlong, Lu; Hua, Yan; Zhishui, Yu; Chonggui, Li; Qinghua, Lu

    2014-08-01

    Three Cu-Mo-Si coatings were synthesized on steel using laser cladding. The coatings have dense microstructure with composite phases including metal silicates and Cu-based solid solution. Different alloy compositions reduce different phases generated in the coatings. Phases appeared in three coatings were Cu + MoSi2 + Mo5Si3 + Cu3Si (Coatings 1 and 2), Cu + Mo3Si + Mo5Si3 + Cu3Si (Coating 3), respectively. The microhardness of coatings is in the range of 600 to 900 HV. The amount of Mo5Si3 phase decides the hardness of Cu-Mo-Si coatings in laser processing. The proof is that the highest hardness which is about 900 HV occurs in the clad layer of Coating 1. The thickness of clad layer of three coatings is about 0.7 mm (Coating 1), 0.8 mm (Coating 2) and 1.0 mm (Coating 3), respectively. The average friction coefficient for Coatings 1-3 is 0.40, 0.56 and 0.60, respectively. Wear rate values of 2.9 × 10-6 g/N m (Coating 1), 3.1 × 10-6 g/N m (Coating 2) and 3.5 × 10-6 g/N m (Coating 3) are calculated, respectively. The amount and kind of metal silicates have a huge influence on the wear resistance of coatings.

  20. Kinetics of MoSi[sub 2] pest during low-temperature oxidation

    SciTech Connect

    Chou, T.C. ); Nieh, T.G. )

    1993-07-01

    The kinetics of MoSi[sub 2] pest, caused by oxidation in air, has been studied. Experimental results indicated that pest disintegration occurred at temperatures between 375 and 500 [degree]C. The volumes of test samples increased with oxidation duration. Analysis of change in sample volume versus oxidation duration revealed that the pest disintegration consisted of two stages, namely nucleation (or incubation) and growth.The onset of growth stage depended on the test temperature. More importantly, changes in sample volume were found to obey a linear relationship with time during the growth stage. Equations were formulated to demonstrate that the growth kinetics of pest disintegration was proportional to the rates of change in sample volume. The rates of volume change during MoSi[sub 2] pest were calculated to be 4.9[times]10[sup [minus]6], 2.8[times]10[sup [minus]5], 3.7[times]10[sup [minus]5], and 5.4[times]10[sup [minus]5] cm[sup 3]/s at 375, 400, 425, and 450 [degree]C, respectively; the growth kinetics increased with oxidation temperature. The activation energy for the growth stage of pest disintegration was determined to be 27.6 kcal/mole, which agrees well with the activation energy for the low-temperature oxidation of MoSi[sub 2].

  1. MoSi 2 Oxidation in 670-1498 K Water Vapor

    SciTech Connect

    Sooby Wood, Elizabeth; Parker, Stephen S.; Nelson, Andrew T.; Maloy, Stuart A.; Butt, D.

    2016-03-08

    Molybdenum disilicide (MoSi2) has well documented oxidation resistance at high temperature (T > 1273 K) in dry O2 containing atmospheres due to the formation of a passive SiO2 surface layer. But, its behavior under atmospheres where water vapor is the dominant species has received far less attention. Oxidation testing of MoSi2 was performed at temperatures ranging from 670–1498 K in both 75% water vapor and synthetic air (Ar-O2, 80%–20%) containing atmospheres. Here the thermogravimetric and microscopy data describing these phenomena are presented. Over the temperature range investigated, MoSi2 displays more mass gain in water vapor than in air. The oxidation kinetics observed in water vapor differ from that of the air samples. Two volatile oxides, MoO2(OH)2 and Si(OH)4, are thought to be the species responsible for the varied kinetics, at 670–877 K and at 1498 K, respectively. Finally, we observed an increase in oxidation (140–300 mg/cm2) from 980–1084 K in water vapor, where passivation is observed in air.

  2. Processing of Mo-Si-B intermetallics by extrusion and oxidation properties of the extruded Tl-MoSi2-MoB System

    SciTech Connect

    Summers, Eric

    1999-11-08

    An extrusion process was developed that is able to consistently produce large quantities of Mo-Si-B rods without the presence of defects. Binder removal from the extruded rods was studied in detail and it was determined that heating rates on the order of 0.02°/minute (1.2°/hour) are necessary to remove the binder without the formation of defects. This low heating rate resulted in debinding times in excess of 70 hours (approximately 3 days). Wicking was investigated as a means to decrease the time necessary for binder removal. Using 0.05μm alumina powder as a wicking agent, binder removal times were reduced to 10 hours with heating rates up to 1°/minute employed without defect formation. Once the extrusion process was complete the oxidation properties of the Tl-MoSi2-MoB extruded phase assemblage was investigated. It was determined that this composition exhibits catastrophic oxidation or pesting in the temperature range of 660-760°C, resulting in the material turning to dust. Outside of this temperature range the composition is oxidatively stable. Continuous mass measurements were taken at 1,300, 1,450, and 1,600 C to determine the oxidation rate constants of this material. Parabolic rate constants of 6.9 x 10-3, 1.3 x 10-3, and 9.1 x 10-3 mg2/cm4/hr were determined for 1,300, 1,450, and 1,600 C respectively.

  3. Interfacial reactions between amorphous W-Si thin films and polycrystalline overlayers

    SciTech Connect

    Thomas, R.E.; Perepezko, J.H.; Wiley, J.D.

    1985-01-01

    Interactions between amorphous metal thin films and either a substrate or an overlayer can limit their effectiveness as diffusion barriers. We have found in previous studies that Au and Al polycrystalline thin films in contact with amorphous W-Si lowers the crystallization temperature of the a-(W-Si) by at least 100C. In contrast Cu and Mo have no apparent effect on the stability of the amorphous layer. The mechanisms leading to premature crystallization are not well understood. Amorphous W/sub .72/Si/sub .28/ was deposited by dc sputtering onto single crystal Si substrates. Overlayers of Al were then evaporated onto the W-Si. Using Auger electron spectroscopy depth profiling coupled with cross-section TEM, we have studied interfacial reactions between the amorphous layer and polycrystalline Al. Auger profiling results show that in the case of Al overlayers, W and Si diffuse out of the a-(W-Si) into the Al where WAl/sub 12/ forms. These results can be explained in the context of three binary diffusion couples, W-Si, W-Al, Al-Si, and the individual interactions associated with these couples.

  4. Characterisation of amorphous molybdenum silicide (MoSi) superconducting thin films and nanowires

    NASA Astrophysics Data System (ADS)

    Banerjee, Archan; Baker, Luke J.; Doye, Alastair; Nord, Magnus; Heath, Robert M.; Erotokritou, Kleanthis; Bosworth, David; Barber, Zoe H.; MacLaren, Ian; Hadfield, Robert H.

    2017-08-01

    We report on the optimisation of amorphous molybdenum silicide thin film growth for superconducting nanowire single-photon detector (SNSPD) applications. Molybdenum silicide was deposited via co-sputtering from Mo and Si targets in an Ar atmosphere. The superconducting transition temperature (T c) and sheet resistance (R s) were measured as a function of thickness and compared to several theoretical models for disordered superconducting films. Superconducting and optical properties of amorphous materials are very sensitive to short- (up to 1 nm) and medium-range order (˜1-3 nm) in the atomic structure. Fluctuation electron microscopy studies showed that the films assumed an A15-like medium-range order. Electron energy loss spectroscopy indicates that the film stoichiometry was close to Mo83Si17, which is consistent with reports that many other A15 structures with the nominal formula A 3 B show a significant non-stoichiometry with A:B > 3:1. Optical properties from ultraviolet (270 nm) to infrared (2200 nm) wavelengths were measured via spectroscopic ellipsometry for 5 nm thick MoSi films indicating high long wavelength absorption. We also measured the current density as a function of temperature for nanowires patterned from a 10 nm thick MoSi film. The current density at 3.6 K is 3.6 × 105 A cm-2 for the widest wire studied (2003 nm), falling to 2 × 105 A cm-2 for the narrowest (173 nm). This investigation confirms the excellent suitability of MoSi for SNSPD applications and gives fresh insight into the properties of the underlying materials.

  5. Novel Processing of mo-si-b Intermetallics for improved efficiency of power systems

    SciTech Connect

    M.J. Kramer; O. Degirmen; A.J. Thom; M. Akinc

    2004-09-30

    Multiphase composite alloys based on the Mo-Si-B system are candidate materials for ultra-high temperature applications. In non load-bearing applications such as thermal barrier coatings or heat exchangers in fossil fuel burners, these materials may be ideally suited. Alloys based on the Mo{sub 5}Si{sub 3}B{sub x} phase (Tl phase) possess excellent oxidation resistance to at least 1600 C in synthetic air atmospheres. However, the ability of Tl-based alloys to resist aggressive combustion environments has not yet been determined. The present work seeks to investigate the resistance of these Mo-Si-B alloys to simulated combustion atmospheres. Material was pre-alloyed by combustion synthesis, and samples for testing were prepared by classic powder metallurgical processing techniques. Precursor material synthesized by self-heating-synthesis was sintered to densities exceeding 98% in an argon atmosphere at 1800 C. The approximate phase assemblage of the material was 57% Tl, 29% MoB, 14% MoSi{sub 2} (wt%). The alloy was oxidized from 1000-1100 C in flowing air containing water vapor at 18 Torr. At 1000 C the material achieved a steady state mass loss, and at 1100 C the material undergoes a steady state mass gain. The oxidation rate of these alloys in this temperature regime was accelerated by the presence of water vapor compared to oxidation in dry air. The results of microstructural analysis of the tested alloys will be discussed. Techniques and preliminary results for fabricating near-net-shaped parts will also be presented.

  6. Application of Reactive Ion Etching to the Fabrication of Microstructure on Mo/Si Multilayer

    NASA Astrophysics Data System (ADS)

    Le, Zi-chun; L, Dreeskornfeld; S, Rahn; R, Segler; U, Kleineberg; U, Heinzmann

    1999-09-01

    Mo/Si multilayer mirrors (30 periods, doublelayer thickness 7 nm) with the AZ-PF514 resist pattern whose smallest lines and spaces structure was 0.5 μm were etched by reactive ion etching (RIE) in a fluorinated plasma. The etch rate, selectivity and etch profile were investigated as a function of the gas mixture, pressure, and plasma rf power. The groove depth and the etch profile were investigated by an atomic force microscope before RIE, after RIE and after resist removal.

  7. Near-Eutectic Ternary Mo-Si-B Alloys: Microstructures and Creep Properties

    NASA Astrophysics Data System (ADS)

    Hasemann, G.; Kaplunenko, D.; Bogomol, I.; Krüger, M.

    2016-11-01

    In the present work, the microstructural evolution during the solidification of different near-eutectic Mo-Si-B alloys was investigated. The alloy compositions were chosen from the vicinity of the eutectic region with respect to published liquidus projections. The aim was to identify a eutectic alloy composition in the Mo-rich region of the system, which would be suitable for directional solidification (DS). In a second step, two alloy compositions were prepared via DS and first creep results of these near-eutectic DS alloys are presented and discussed.

  8. Impact of new MoSi mask compositions on processing and repair

    NASA Astrophysics Data System (ADS)

    Garetto, Anthony; Stuckey, John; Butler, Don

    2010-09-01

    The mask industry has recently witnessed an increasing number of new MoSi mask blank materials which are quickly replacing the older materials as the standard in high end mask shops. These new materials, including OMOG (opaque MoSi on glass) and high transmission (Hi-T) films, are driven foremost by the need to reduce feature size through resolution enhancement techniques (RET). The subject of this paper is a new low stress, Hi-T material which addresses the challenges presented by transitioning to smaller technology nodes including difficulties with pattern transfer, cleaning and repair. This material, based on currently employed MoSi films, eliminates process steps and utilizes a thinner overall substrate stack than currently used Hi-T schemes allowing an increase in critical dimension (CD) uniformity and feature resolution and more robustness due to a lower aspect ratio. While this new material is MoSi based the small compositional change requires, in some cases, a significant change in processing. Among the most impacted areas are the etch, clean and repair steps. Given the potential for defects to manifest on masks, repair is an invaluable step that can significantly impact the overall yield and lead to a reduction in cycle time1. The Carl Zeiss MeRiT® electron beam mask repair line provides the most advanced repair capabilities allowing a wide range of repairs to be performed on a number of mask types2. In a joint effort between MP Mask Technology Center LLC and Carl Zeiss SMT, this paper focuses on the benefits of the new Hi-T mask blank and the challenges it presents to the repair community. The differences between the new low stress, Hi-T material and current Hi-T technologies are presented and on site compositional analysis is performed with x-ray photoelectron spectroscopy (XPS) to illuminate the compositional differences. The development of a repair process for the new material utilizing the on-site Carl Zeiss MeRiT® MG 45 is presented along with

  9. Vortex Pinning in Superconducting MoGe Films Containing Conformal Arrays of Nanoscale Holes and Magnetic Dots

    NASA Astrophysics Data System (ADS)

    Wang, Y. L.; Latimer, M. L.; Xiao, Z. L.; Ocola, L. E.; Divan, R.; Welp, U.; Crabtree, G. W.; Kwok, W. K.

    2013-03-01

    Recent numerical simulations by Ray et al. predict that a conformal pinning array can produce stronger vortex pinning effect than other pinning structures with an equivalent density of pinning sites. Here we present experimental investigations on conformal pinning structures. Direct and conformal pinning arrays of triangular and square lattices were introduced into MoGe superconducting films using focused-ion-beam milling or electron-beam lithography. Transport measurements on critical currents and magnetoresistances were carried out on these samples to reveal the advantages of conformal pinnings. Effects of random pinnings with the same average density were also studied for comparison. Details on sample fabrications and effects of pinning types (holes versus magnetic dots) will be presented. Work supported by the US DoE-BES funded Energy Frontier Research Center (YLW), and by Department of Energy, Office of Science, Office of Basic Energy Sciences (MLL, ZLX, LEO, RD, UW, WKK), under Contract No. DE-AC02-06CH11357

  10. a Study on the Tribology Characteristics of MoSi2 Intermetallic Compounds Under Different Sintering Temperatures

    NASA Astrophysics Data System (ADS)

    Park, Won Jo; Huh, Sun Chul; Lee, Kang Young; Song, Hong Tae; Yoon, Han Ki

    Molybdenum disilicide (MoSi2) is considered to be a promising high temperature material for turbojet and hypersonic engines in aerospace and various industrial applications, because of a high melting point (2030°C), adequate density (6.3g/cm3) and an excellent oxidation resistance. Some researches on MoSi2 have been carried out but the wear behavior of this material is seldom studied. This paper focused on the effect of sintering temperature of MoSi2 on the wear behavior. MoSi2 powder was evaluated from the variation of fabricating conditions such as preparation temperature 1250°C, 1350°C and 1500°C. Wear tests were performed with a sliding speed of 5.21mm/sec and a normal load of 8kgf. Each test was run over a period of 6 hours. The wear behavior is evaluated with respect to the hardness of materials. Hardness test was carried out with a Micro-Vickers hardness tester. As a result of the tests, the friction coefficient was decreased with the increasing sintering temperature of MoSi2 but the friction coefficient did not vary much for all specimens at temperatures. Hardness values decreased with a decrease in sintering temperature because the indentation under a lower temperature probably contained more defects.

  11. Mechanical characterization of SiC whisker-reinforced MoSi/sub 2/

    SciTech Connect

    Carter, D.H.; Gibbs, W.S.; Petrovic, J.J.

    1988-01-01

    The mechanical characteristics of an intermetallic matrix with two different reinforcements were studied. The matrix material was MoSi/sub 2/, with either Los Alamos VLS SiC whiskers or Huber VS SiC whiskers. The purpose of the reinforcement was to provide toughening at ambient temperature and strengthening at elevated temperatures. The VLS whiskers greatly improved the yield strength of the matrix at 1200/degree/C, and also increased the room temperature fracture toughness of the matrix. The VS whiskers were added because they are much smaller in length and diameter, and therefore decreased the mean free path between whiskers, at the same volume fraction. The VS whiskers improved the toughness of the matrix at ambient temperature, and increased the yield strength of MoSi/sub 2/ at 1400/degree/C by 470%. The high strength of this new composite places this material in the realm of attractive engineering materials for high-temperature applications. 11 refs., 6 refs., 1 tab.

  12. Mo-Si-B alloys for ultrahigh-temperature structural applications.

    PubMed

    Lemberg, J A; Ritchie, R O

    2012-07-10

    A continuing quest in science is the development of materials capable of operating structurally at ever-increasing temperatures. Indeed, the development of gas-turbine engines for aircraft/aerospace, which has had a seminal impact on our ability to travel, has been controlled by the availability of materials capable of withstanding the higher-temperature hostile environments encountered in these engines. Nickel-base superalloys, particularly as single crystals, represent a crowning achievement here as they can operate in the combustors at ~1100 °C, with hot spots of ~1200 °C. As this represents ~90% of their melting temperature, if higher-temperature engines are ever to be a reality, alternative materials must be utilized. One such class of materials is Mo-Si-B alloys; they have higher density but could operate several hundred degrees hotter. Here we describe the processing and structure versus mechanical properties of Mo-Si-B alloys and further document ways to optimize their nano/microstructures to achieve an appropriate balance of properties to realistically compete with Ni-alloys for elevated-temperature structural applications.

  13. In-situ formation of alumina coatings in niobium toughened Mo(Si,Al)[sub 2

    SciTech Connect

    Costa e Silva, A.; Kaufman, M.J. . Dept. of Materials Science and Engineering)

    1994-10-01

    One approach that has been explored for the toughening and strengthening of MoSi[sub 2] based materials is the introduction of ductile refractory metal reinforcements. Due to the considerable stability of the transition metal silicides and the relatively high mobility of silicon in systems consisting of silicides and refractory metals, it has been found that this approach leads to materials that have poor long term stability at high temperature, unless a coating is interposed between the silicide matrix and the refractory metal reinforcement. Both Xiao and Abbaschian and Lu and coworkers have applied coatings to these reinforcements using conventional techniques. The most promising coatings were oxides, namely alumina and yttria. Besides the difficulties associated with preserving these conventional coatings during processing, it has also been observed that silica inclusions possibly degrade the coating during high temperature exposure. While in-situ coatings have been applied to refractory metal reinforcements in NbAl[sub 3] and NiAl matrices, the authors known of no successful scheme developed for in-situ coating of these metals in silicide matrices. In this work, an attempt was made to produce in-situ alumina coatings on preoxidized Nb fibers by using an aluminum-rich Mo(Si, Al)[sub 2]-(C40) matrix. Furthermore, the effectiveness of this layer for (a) protecting the fiber from interaction with the matrix and (b) promoting debonding was investigated.

  14. Microstructure of a plasma-sprayed Mo-Si-B alloy

    NASA Astrophysics Data System (ADS)

    Kramer, M. J.; Okumus, S. C.; Besser, M. F.; Ünal, Ö.; Akinc, M.

    2000-03-01

    Powders of Mo52Si38B10 were plasma sprayed under inert conditions onto stainless steel substrates to determine if high density free standing forms could be synthesized by this process. Thermal spray conditions were varied to minimize porosity and oxygen impurities while minimizing evaporative metal losses. The assprayed and sintered microstructures were characterized using scanning and transmission electron microscopy and quantitative x-ray diffraction (XRD). The as-sprayed microstructure consisted of elongated splats tens of microns in length and only one to three microns in thickness. The splats contained submicrometer grains of primarily MoB and Mo5Si3B x (T1) and minor amounts of MoSi2 and a glassy grain boundary phase. The interior of the splats typically consisted of a fine eutectic of MoB and T1. Small pieces were cut out of the cross section of the sample and pressureless sintered for 2, 6, and 10 h at 1800 °C in flowing Ar. After sintering for 2 h at 1800 °C, the samples exhibited a coarser but equiaxed microstructure (1 to 5 µm grain size) containing 78 vol.% T1, 16 vol.% MoB, and 6 vol.% MoSi2 as determined by XRD. Approximately 8 at.% of the Si formed silica. The high-temperature anneal removed all vestiges of the layered structure observed in the as-sprayed samples.

  15. Development of a Mo-Si-B coating for Nb-based Alloys and the Effects of Zr Additions to Mo-Si-B Coatings for Enhanced Oxidation Protection in Ultra-High Temperature Applications

    NASA Astrophysics Data System (ADS)

    Lu-Steffes, Otto John

    Higher efficiencies and reduced emissions performance of fossil fuel energy systems are achieved with increasing operation temperatures. This increase in operating temperature requires the use of materials with higher melting points such as refractory metal alloys. However, refractory metals suffer from catastrophic oxidation in this type of environment. Thus, oxidation protection for refractory metal alloys is a crucial step in developing next generation ultra-high temperature materials. To meet this challenge, an oxidation resistant coating for Nb based alloys has been designed as well as the incorporation of zirconium into the Mo-Si-B coating to provide further corrosion protection and a reduction in temperature for the underlying multi-layered structure. Niobium samples coated with a Mo-Si-B coating demonstrate enhanced oxidation protection compared to samples only coated with Si-B. Thermogravimetric analysis testing at 1300°C for 24 hours for both the Mo-Si-B coated Nb and Nb-based alloys show enhanced oxidation protection with mass changes of 0.44 mg/cm2 and 0.55 mg/cm2, respectively, compared to the uncoated alloy that had a mass change of 87.6 mg/cm2. To demonstrate the design concept for a coating with thermal barrier behavior, Zr is added to the Mo-Si-B coating through the pack cementation technique. The resulting coating shows that the Zr reacts with the aluminosilica top layer to form Zr silicides and ZrO2. Upon oxidation, the coating forms a mixed top layer composed of borosilica, ZrO2 and ZrSiO 4. Oxidation testing of the Zr modified Mo-Si-B coating exhibits low mass change indicating that the coating provides oxidation protection and that the Zr additions do not interfere with the oxidation protection of the Mo-Si-B coating. Finite element modeling using object oriented finite element analysis of the coating structures yielded an evaluation of the mechanical and thermal properties of the coatings, providing insight into the thermal performance and

  16. Mechanically alloyed Mo-Si-B alloys with a continuous a-Mo matrix and improved mechanical properties

    SciTech Connect

    Krueger, M.; Franz, S.; Heilmaier, M.; Schneibel, Joachim H; Jehanno, P.; Boening, Mike Boening; Kestler, Heinrich

    2008-01-01

    Mechanical alloying (MA) followed by cold isostatic pressing (CIPing), sintering and hot isostatic pressing (HIPing) was used to prepare Mo-base silicide alloys consisting of a Mo(Si) solid solution and the intermetallic phases Mo{sub 3}Si and Mo{sub 5}SiB{sub 2}. The microstructural development during milling of both binary Mo-Si and Mo-B and ternary Mo-Si-B powder mixtures was evaluated. While obtaining a supersaturated solid solution requires rather long milling times, domain size (which correlates with the grain size) is reduced to below 100 {angstrom} after about 10 h of milling. After heat treatment and consolidation the microstructure reveals a continuous {alpha}-Mo matrix with embedded, uniformly distributed intermetallic particles. The establishment of such a microstructure is beneficial for the mechanical properties since, as compared to a discontinuous {alpha}-Mo matrix, it decreases the brittle-to-ductile transition temperature (BDTT) by about 150 K.

  17. Chemical vapor deposition of W-Si-N and W-B-N

    DOEpatents

    Fleming, J.G.; Roherty-Osmun, E.L.; Smith, P.M.; Custer, J.S.; Jones, R.V.; Nicolet, M.; Madar, R.; Bernard, C.

    1999-06-29

    A method of depositing a ternary, refractory based thin film on a substrate by chemical vapor deposition employing precursor sources of tungsten comprising WF[sub 6], either silicon or boron, and nitrogen. The result is a W-Si-N or W-B-N thin film useful for diffusion barrier and micromachining applications. 10 figs.

  18. Chemical vapor deposition of W-Si-N and W-B-N

    DOEpatents

    Fleming, James G.; Roherty-Osmun, Elizabeth Lynn; Smith, Paul M.; Custer, Jonathan S.; Jones, Ronald V.; Nicolet, Marc-A.; Madar, Roland; Bernard, Claude

    1999-01-01

    A method of depositing a ternary, refractory based thin film on a substrate by chemical vapor deposition employing precursor sources of tungsten comprising WF.sub.6, either silicon or boron, and nitrogen. The result is a W--Si--N or W--B--N thin film useful for diffusion barrier and micromachining applications.

  19. Mechanical properties of Mo-Si-B alloys fabricated by using core-shell powder with dispersion of yttria nanoparticles

    NASA Astrophysics Data System (ADS)

    Byun, Jong Min; Bang, Su-Ryong; Choi, Won June; Kim, Min Sang; Noh, Goo Won; Kim, Young Do

    2017-01-01

    In recent years, refractory materials with excellent high-temperature properties have been in the spotlight as a next generation's high-temperature materials. Among these, Mo-Si-B alloys composed of two intermetallic compound phases (Mo5SiB2 and Mo3Si) and a ductile α-Mo phase have shown an outstanding thermal properties. However, due to the brittleness of the intermetallic compound phases, Mo-Si-B alloys were restricted to apply for the structural materials. So, to enhance the mechanical properties of Mo-Si-B alloys, many efforts to add rare-earth oxide particles in the Mo-Si-B alloy were performed to induce the improvement of strength and fracture toughness. In this study, to investigate the effect of adding nano-sized Y2O3 particles in Mo-Si-B alloy, a core-shell powder consisting of intermetallic compound phases as the core and nano-sized α-Mo and Y2O3 particles surrounding the core was fabricated. Then pressureless sintering was carried out at 1400 °C for 3 h, and the mechanical properties of sintered bodies with different amounts of Y2O3 particles were evaluated by Vickers hardness and 3-point bending test. Vickers hardness was improved by dispersed Y2O3 particles in the Mo-Si-B alloy. Especially, Mo-3Si-1B-1.5Y2O3 alloy had the highest value, 589 Hv. The fracture toughness was measured using Mo-3Si-1B-1.5Y2O3 alloy and the value indicated as 13.5 MPa·√m.

  20. The influence of working gas pressure on interlayer mixing in magnetron-deposited Mo/Si multilayers

    SciTech Connect

    Pershyn, Yuriy; Gullikson, Erik; Artyukov, Igor; Kondratenko, Valeriy; Sevryukova, Victoriya; Voronov, Dmitriy; Zubarev, Evgeniy; Vinogradov, Alexander

    2011-08-08

    Impact of Ar gas pressure (1-4 mTorr) on the growth of amorphous interlayers in Mo/Si multilayers deposited by magnetron sputtering was investigated by small-angle x-ray scattering ({lambda} = 0.154 nm) and methods of cross-sectional transmission electron microscopy. Some reduction of thickness of the amorphous inter-layers with Ar pressure increase was found, while composition of the layers was enriched with molybdenum. The interface modification resulted in raise of EUV reflectance of the Mo/Si multilayers.

  1. Oxidation Behavior of Mo-Si-B Alloys in Wet Air

    SciTech Connect

    M. Kramer; A. Thom; O. Degirmen; V. Behrani; M. Akinc

    2002-04-22

    Multiphase composite alloys based on the Mo-Si-B system are candidate materials for ultra-high temperature applications. In non load-bearing uses such as thermal barrier coatings or heat exchangers in fossil fuel burners, these materials may be ideally suited. The present work investigated the effect of water vapor on the oxidation behavior of Mo-Si-B phase assemblages. Three alloys were studied: Alloy 1 = Mo{sub 5}Si{sub 3}B{sub x} (T1)- MoSi{sub 2}- MoB, Alloy 2 = T1- Mo{sub 5}SiB{sub 2} (T2)- Mo{sub 3}Si, and Alloy 3 = Mo- T2- Mo{sub 3}Si. Tests were conducted at 1000 and 1100C in controlled atmospheres of dry air and wet air nominally containing 18, 55, and 150 Torr H{sub 2}O. The initial mass loss of each alloy was approximately independent of the test temperature and moisture content of the atmosphere. The magnitude of these initial losses varied according to the Mo content of the alloys. All alloys formed a continuous, external silica scale that protected against further mass change after volatilization of the initially formed MoO{sub 3}. All alloys experienced a small steady state mass change, but the calculated rates cannot be quantitatively compared due to statistical uncertainty in the individual mass measurements. Of particular interest is that Alloy 3, which contains a significant volume fraction of Mo metal, formed a protective scale. All alloys formed varying amounts of subscale Mo and MoO{sub 2}. This implies that oxygen transport through the external silica scale has been significantly reduced. For all alloys, water vapor accelerated the growth of a multiphase interlayer at the silica scale/unoxidized alloy interface. This interlayer is likely composed of fine Mo and MoO{sub 2} that is dispersed within a thin silica matrix. Alloy 3 was particularly sensitive to water accelerated growth of this interlayer. At 1100 C, the scale thickness after 300 hours increased from about 20 mm in dry air to nearly 100 mm in wet air.

  2. High reflectance-low stress Mo-Si multilayer reflective coatings

    DOEpatents

    Montcalm, Claude; Mirkarimi, Paul B.

    2000-01-01

    A high reflectance-low stress Mo-Si multilayer reflective coating particularly useful for the extreme ultraviolet (EUV) wavelength region. While the multilayer reflective coating has particular application for EUV lithography, it has numerous other applications where high reflectance and low stress multilayer coatings are utilized. Multilayer coatings having high near-normal incidence reflectance (R.gtoreq.65%) and low residual stress (.ltoreq.100 MPa) have been produced using thermal and non-thermal approaches. The thermal approach involves heating the multilayer coating to a given temperature for a given time after deposition in order to induce structural changes in the multilayer coating that will have an overall "relaxation" effect without reducing the reflectance significantly.

  3. Process for fabricating high reflectance-low stress Mo--Si multilayer reflective coatings

    DOEpatents

    Montcalm, Claude; Mirkarimi, Paul B.

    2001-01-01

    A high reflectance-low stress Mo--Si multilayer reflective coating particularly useful for the extreme ultraviolet (EUV) wavelength region. While the multilayer reflective coating has particular application for EUV lithography, it has numerous other applications where high reflectance and low stress multilayer coatings are utilized. Multilayer coatings having high near-normal incidence reflectance (R.gtoreq.65%) and low residual stress (.ltoreq.100 MPa) have been produced using thermal and non-thermal approaches. The thermal approach involves heating the multilayer coating to a given temperature for a given time after deposition in order to induce structural changes in the multilayer coating that will have an overall "relaxation" effect without reducing the reflectance significantly.

  4. Single shot damage mechanism of Mo/Si multilayer optics under intense pulsed XUV-exposure.

    PubMed

    Khorsand, A R; Sobierajski, R; Louis, E; Bruijn, S; van Hattum, E D; van de Kruijs, R W E; Jurek, M; Klinger, D; Pelka, J B; Juha, L; Burian, T; Chalupsky, J; Cihelka, J; Hajkova, V; Vysin, L; Jastrow, U; Stojanovic, N; Toleikis, S; Wabnitz, H; Tiedtke, K; Sokolowski-Tinten, K; Shymanovich, U; Krzywinski, J; Hau-Riege, S; London, R; Gleeson, A; Gullikson, E M; Bijkerk, F

    2010-01-18

    We investigated single shot damage of Mo/Si multilayer coatings exposed to the intense fs XUV radiation at the Free-electron LASer facility in Hamburg - FLASH. The interaction process was studied in situ by XUV reflectometry, time resolved optical microscopy, and "post-mortem" by interference-polarizing optical microscopy (with Nomarski contrast), atomic force microscopy, and scanning transmission electron microcopy. An ultrafast molybdenum silicide formation due to enhanced atomic diffusion in melted silicon has been determined to be the key process in the damage mechanism. The influence of the energy diffusion on the damage process was estimated. The results are of significance for the design of multilayer optics for a new generation of pulsed (from atto- to nanosecond) XUV sources.

  5. Blister formation in Mo/Si multilayered structures induced by hydrogen ions

    NASA Astrophysics Data System (ADS)

    van den Bos, R. A. J. M.; Lee, C. J.; Benschop, J. P. H.; Bijkerk, F.

    2017-07-01

    We report on blister formation in nanometer thick Mo/Si multilayer structures due to exposure to hydrogen ion fluxes. The influence of hydrogen flux and ion energy for blister formation have been measured and compared to a blister model. The blister number density increases significantly around 100 eV when increasing the ion energy from 50 to 200 eV. This stepwise behavior could be explained by the fact that for energies  >100 eV hydrogen ions could directly penetrate to the depth where delamination takes place. From the blister model also the blisters internal pressure and surface energy was calculated to be around 100-800 MPa and γ =1.87~\\text{J}~{{\\text{m}}-2} respectively.

  6. Zero-bias anomaly in homogeneously disordered MoGe nanowires undergoing a superconductor-insulator transition

    NASA Astrophysics Data System (ADS)

    Kim, Hyunjeong; Rogachev, A.

    2016-12-01

    Nanowires made of superconducting Mo-Ge alloys undergo a superconductor-insulator transition when their cross-sectional area is reduced. On the insulating side of the transition, the differential resistance of the nanowires drops with voltage and displays a positive zero-bias anomaly (ZBA). To reveal the origin of this ZBA, we fabricated and studied a series of nanowires made of amorphous alloys with composition M o50G e50 . The length of wires was in the range 150 nm-11 μm and width was in the range 10-20 nm. We also fabricated and measured several more complex nanowire-based structures: (i) a nanowire gated by a nearby film electrode, (ii) a nanowire connected to film electrodes with an "adiabatically reduced" width, (iii) a nanowire with a multielectrode configuration which allowed comparison of different sections of the same nanowire, and (iv) a nanowire with different sizes of film electrodes. We found that for M o50G e50 nanowires all experimental parameters of the ZBA and their dependence on nanowire length can be explained by electron heating. Several physical processes thought to be responsible for the ZBA have been analyzed and rejected.

  7. Effect of separating layer thickness on W/Si multilayer replication.

    PubMed

    Wang, Fangfang; Mu, Baozhong; Jin, Huijun; Yang, Xiajun; Zhu, Jingtao; Wang, Zhanshan

    2011-08-15

    The direct replication of W/Si multilayers and the effect of separating layer thickness on the performance of the multilayer before and after replication are investigated systematically. Platinum separating layers with different layer thicknesses were first deposited onto different supersmooth mandrels and then W/Si multilayers with the similar structure were deposited onto these Pt-coated mandrels by using a high vacuum DC magnetron sputtering system. After the deposition, these multilayers were replicated onto the commercially available float glass substrates by epoxy replication technique. These multilayers before and after replication are characterized by grazing-incident X-ray reflectance measurement and atomic force microscope. The measured results show that before and after replication, the reflectivity curves are much similar to those calculated and the surface roughness of each sample is close to that of the mandrel, when the separating layer thickness is larger than 1.5 nm. These results reveal that the W/Si multilayer with the separating layer thickness larger than 1.5 nm can be successfully replicated onto a substrate without modification of the structure, significant increase of surface roughness or apparent change of reflectivity.

  8. Synthesis and analysis of Mo-Si-B based coatings for high temperature oxidation protection of ceramic materials

    NASA Astrophysics Data System (ADS)

    Ritt, Patrick J.

    The use of Ni-based superalloys in turbine engines has all but been exhausted, with operating temperatures nearing the melting point of these materials. The use of ceramics in turbine engines, particularly ceramic matrix composites such as SiC/C and SiC/SiC, is of interest due to their low density and attractive mechanical properties at elevated temperatures. The same materials are also in consideration for leading edges on hypersonic vehicles. However, SiC-based composites degrade in high temperature environments with low partial pressures of oxygen due to active oxidation, as well as high temperature environments containing water or sand. The need for a protective external coating for SiC-based composites in service is obvious. To date, no coating investigated for SiC/C or SiC/SiC has been proven to be resistant to oxidation and corrosion at intermediate and high temperatures, as well as in environments deficient in oxygen. The Mo-Si-B coating shows great promise in this area, having been proven resistant to attack from oxidation at extreme temperatures, from water vapor and from calcia-magnesia-aluminosilicate (CMAS). The adaptation of the Mo-Si-B coating for ceramic materials is presented in detail here. Evaluation of the coating under a range of oxidation conditions as well as simulated re-entry conditions confirms the efficacy of the Mo-Si-B based coating as protection from catastrophic failure. The key to the oxidation and corrosion resistance is a robust external aluminoborosilica glass layer that forms and flows quickly to cover the substrate, even under the extreme simulated re-entry conditions. Suppression of active oxidation of SiC, which may occur during atmospheric re-entry and hypersonic flight trajectories, has also been examined. In order to adapt the Mo-Si-B based coating to low partial pressures of oxygen and elevated temperatures, controlled amounts of Al were added to the Mo-Si-B based coating. The resulting coating decreased the inward

  9. Development and Characterization of SiC)/ MoSi2-Si3N4(p) Hybrid Composites

    NASA Technical Reports Server (NTRS)

    Hebsur, Mohan G.

    1998-01-01

    Intermetallic compound MoSi2 has long been known as a high temperature material that has excellent oxidation resistance and electrical/thermal conductivity. Also its low cost, high melting point (2023 C), relatively low density (6.2 g/cu cm versus 9 g/cu cm for current engine materials), and ease of machining, make it an attractive structural material. However, the use of MoSi2 has been hindered due to its poor toughness at low temperatures, poor creep resistance at high temperatures, and accelerated oxidation (also known as 'pest' oxidation) at temperatures between approximately 450 and 550 C. Continuous fiber reinforcing is very effective means of improving both toughness and strength. Unfortunately, MoSi2 has a relatively high coefficient of thermal expansion (CTE) compared to potential reinforcing fibers such as SiC. The large CTE mismatch between the fiber and the matrix resulted in severe matrix cracking during thermal cycling. Addition of about 30 to 50 vol % of Si3N4 particulate to MoSi2 improved resistance to low temperature accelerated oxidation by forming a Si2ON2 protective scale and thereby eliminating catastrophic 'pest failure'. The Si3N4 addition also improved the high temperature creep strength by nearly five orders of magnitude, doubled the room temperature toughness and significantly lowered the CTE of the MoSi2 and eliminated matrix cracking in SCS-6 reinforced composites even after thermal cycling. The SCS-6 fiber reinforcement improved the room temperature fracture toughness by seven times and impact resistance by five times. The composite exhibited excellent strength and toughness improvement up to 1400 C. More recently, tape casting was adopted as the preferred processing of MoSi2-base composites for improved fiber spacing, ability to use small diameter fibers, and for lower cost. Good strength and toughness values were also obtained with fine diameter Hi-Nicalon tow fibers. This hybrid composite remains competitive with ceramic matrix

  10. Growth of Oriented C11(b) MoSi(2) Bicrystals Using a Modified Czochralski Technique

    SciTech Connect

    Chu, F.; Garrett, J.D.; McClellan, K.J.; Michael J.R.; Mitchell, T.E.; Peralta, P.

    1999-06-02

    Oriented bicrystals of pure C11b MoSi2 have been grown in a tri-arc furnace using the Czochralski technique. Two single crystal seeds were used to initiate the growth. Each seed had the orientation intended for one of the grains of the bicrystals, which resulted in a 60° twist boundary on the (110) plane. Seeds were attached to a water-cooled seed rod, which was pulled at 120 mm/h with the seed rod rotating at 45 rpm. The water- cooled copper hearth was counter-rotated at 160 rpm. Asymmetric growth ridges associated with each seed crystal were observed during growth and confirmed the existence of a bicrystal. It was also found that careful alignment of the seeds was needed to keep the grain boundary from growing out of the boule. The resulting boundary was characterized by imaging and crystallographic techniques in a scanning electron microscope. The boundary was found to be fairly sharp and the misorientation between the grains remained within 2° from the disorientation between the seeds.

  11. Rapid Solidification Behavior of Fe-Cr-Mn-Mo-Si-C Alloys

    NASA Astrophysics Data System (ADS)

    Ranganathan, Sathees; Makaya, Advenit; Fredriksson, Hasse; Savage, Steven

    2007-12-01

    The rapid solidification behavior of alloys in the Fe-Cr-Mn-Mo-Si-C system was investigated for different compositions and cooling rates. The C content was varied and alloying additions of Mo and B were studied with respect to their effect on the microstructure. The alloys were cast as either melt-spun ribbons or as 1-mm-thick plates after levitation or as rods 2 to 4 mm in diameter by injection into copper molds. A homogeneous single-phase structure was obtained for the alloy of composition 72.8Fe-8Cr-6Mn-5Si-5Mo-3.2C (wt pct), for a sample diameter of 2.85 mm, at a cooling rate of ≈1100 K/s. The single-phase structure was identified as a metastable solid solution, exhibiting the characteristics of the ɛ phase. Upon reheating, decomposition of the single-phase structure into fine bainite plates and secondary carbides was observed between 600 °C and 700 °C. The annealed structure obtained showed high hardness values (>850 HV).

  12. Pest resistant MoSi2-based materials containing in-situ grown .beta.-Si3N4whiskers

    NASA Technical Reports Server (NTRS)

    Hebsur, Mohan G. (Inventor)

    2001-01-01

    A MoSi.sub.2 pest resistant material includes in-situ grown .beta.-Si.sub.3 N.sub.4 whiskers. In addition to excellent pest resistance, the material provides a lower coefficient of thermal expansion for better match with continuous reinforcing fibers such as SiC fibers. A two stage heating and pressing production technique enables lower temperature processing with substantially full densification.

  13. Pest resistant MoSi2-based materials containing in-situ grown .beta.-Si3N4 whiskers

    NASA Technical Reports Server (NTRS)

    Hebsur, Mohan G. (Inventor)

    2002-01-01

    A MoSi.sub.2 pest resistant material includes in-situ grown .beta.-Si.sub.3 N.sub.4 whiskers. In addition to excellent pest resistance, the material provides a lower coefficient of thermal expansion for better match with continuous reinforcing fibers such as SiC fibers. A two stage heating and pressing production technique enables lower temperature processing with substantially full densification.

  14. Al-MoSi2 Composite Materials: Analysis of Microstructure, Sliding Wear, Solid Particle Erosion, and Aqueous Corrosion

    NASA Astrophysics Data System (ADS)

    Gousia, V.; Tsioukis, A.; Lekatou, A.; Karantzalis, A. E.

    2016-08-01

    In this effort, AMCs reinforced with new intermetallic phases, were produced through casting and compared as far as their microstructure, sliding wear, solid particle erosion, and aqueous corrosion response. Casting was selected as a production method based on the concept: (a) ease-to-handle and low cost production route and (b) optimum homogeneity of the reinforcing phase distribution. The MoSi2 phase was produced through vacuum arc melting and the resulting drops were milled for 30 h to produce fine powder, the characteristics of which were ascertained through SEM-EDS and XRD analysis. MoSi2 was used as precursor source for the final reinforcing phase. The powder material was incorporated in molten Al1050 alloy to additions of 2, 5 and 10 vol.% respectively. Extensive reactivity between the molten Al and the MoSi2 particles was observed, leading to the formation of new reinforcing phases mainly of the Al-Mo system. In all cases, a uniform particle distribution was observed, mainly characterized by isolated intermetallic phases and few intermetallic phase clusters. Sliding wear showed a beneficial action of the reinforcing phase on the wear of the composites. Surface oxidation, plastic deformation, crack formation, and debris abrasive action were the main degradation features. The results of solid particle erosion showed that the mechanism is different as the impact angle and the vol.% change. Regarding the corrosion, the analysis revealed localized corrosion effects. The composite behavior was not altered significantly compared to that of the monolithic matrix.

  15. Bias-polarity-dependent resistance switching in W/SiO2/Pt and W/SiO2/Si/Pt structures.

    PubMed

    Jiang, Hao; Li, Xiang Yuan; Chen, Ran; Shao, Xing Long; Yoon, Jung Ho; Hu, Xiwen; Hwang, Cheol Seong; Zhao, Jinshi

    2016-02-26

    SiO2 is the most significantly used insulator layer in semiconductor devices. Its functionality was recently extended to resistance switching random access memory, where the defective SiO2 played an active role as the resistance switching (RS) layer. In this report, the bias-polarity-dependent RS behaviours in the top electrode W-sputtered SiO2-bottom electrode Pt (W/SiO2/Pt) structure were examined based on the current-voltage (I-V) sweep. When the memory cell was electroformed with a negative bias applied to the W electrode, the memory cell showed a typical electronic switching mechanism with a resistance ratio of ~100 and high reliability. For electroforming with opposite bias polarity, typical ionic-defect-mediated (conducting filament) RS was observed with lower reliability. Such distinctive RS mechanisms depending on the electroforming-bias polarity could be further confirmed using the light illumination study. Devices with similar electrode structures with a thin intervening Si layer between the SiO2 and Pt electrode, to improve the RS film morphology (root-mean-squared roughness of ~1.7 nm), were also fabricated. Their RS performances were almost identical to that of the single-layer SiO2 sample with very high roughness (root-mean-squared roughness of ~10 nm), suggesting that the reported RS behaviours were inherent to the material property.

  16. Bias-polarity-dependent resistance switching in W/SiO2/Pt and W/SiO2/Si/Pt structures

    PubMed Central

    Jiang, Hao; Li, Xiang Yuan; Chen, Ran; Shao, Xing Long; Yoon, Jung Ho; Hu, Xiwen; Hwang, Cheol Seong; Zhao, Jinshi

    2016-01-01

    SiO2 is the most significantly used insulator layer in semiconductor devices. Its functionality was recently extended to resistance switching random access memory, where the defective SiO2 played an active role as the resistance switching (RS) layer. In this report, the bias-polarity-dependent RS behaviours in the top electrode W-sputtered SiO2-bottom electrode Pt (W/SiO2/Pt) structure were examined based on the current-voltage (I-V) sweep. When the memory cell was electroformed with a negative bias applied to the W electrode, the memory cell showed a typical electronic switching mechanism with a resistance ratio of ~100 and high reliability. For electroforming with opposite bias polarity, typical ionic-defect-mediated (conducting filament) RS was observed with lower reliability. Such distinctive RS mechanisms depending on the electroforming-bias polarity could be further confirmed using the light illumination study. Devices with similar electrode structures with a thin intervening Si layer between the SiO2 and Pt electrode, to improve the RS film morphology (root-mean-squared roughness of ~1.7 nm), were also fabricated. Their RS performances were almost identical to that of the single-layer SiO2 sample with very high roughness (root-mean-squared roughness of ~10 nm), suggesting that the reported RS behaviours were inherent to the material property. PMID:26916050

  17. Development and Oxidation Resistance of Plasma Sprayed Mo(Si,Al)2 Coating on Nbss/Nb5Si3 in Situ Composites

    NASA Astrophysics Data System (ADS)

    Yao, Dendzun; Wei, Haixia; Zhou, Chungen

    A Mo(Si,Al)2 coating is developed to protect Nbss/Nb5Si3 in situ composite by plasma spraying. The binary layers of this coating consist of an inner interdiffusion layer surrounded by Mo(Si,Al)2 layer with C40 crystal structure. After oxidation at 1250°C for 100h, Mo(Si,Al)2 coating exhibited an excellent protection against oxidation and good adherence to substrate. The oxidation curve followed parabolic law and even after oxidation at high temperature for 100h, the weight gain per unit area of Mo(Si,Al)2 coating is 8.24mg/cm2. No evident spalling of coating to substrate was observed but a continuous and compact layer of Al2O3 was formed on coating surface to prevent oxidation below coating and substrate.

  18. Ab initio calculations of the cohesive energy of Mo and W and heat of formation of MoSi/sub 2/ and WSi/sub 2/

    SciTech Connect

    Zhu, M.J.; Bylander, D.M.; Kleinman, L.

    1987-08-15

    Using fully relativistic norm-conserving pseudopotentials, we calculate the energy bands, cohesive energy, equilibrium lattice constant, and bulk modulus of Mo and W and compare the results with several recent all-electron and pseudopotential calculations. Comparing these cohesive energies with those we have calculated elsewhere for MoSi/sub 2/, WSi/sub 2/, and Si we also obtain MoSi/sub 2/ and WSi/sub 2/ heats of formation.

  19. Anisotropic phase separation through the metal-insulator transition in amorphous Mo-Ge and Fe-Ge alloys

    SciTech Connect

    Regan, Michael J.

    1993-12-01

    Since an amorphous solid is often defined as that which lacks long-range order, the atomic structure is typically characterized in terms of the high-degree of short-range order. Most descriptions of vapor-deposited amorphous alloys focus on characterizing this order, while assuming that the material is chemically homogeneous beyond a few near neighbors. By coupling traditional small-angle x-ray scattering which probes spatial variations of the electron density with anomalous dispersion which creates a species-specific contrast, one can discern cracks and voids from chemical inhomogeneity. In particular, one finds that the chemical inhomogeneities which have been previously reported in amorphous FexGe1-x and MoxGe1-x are quite anisotropic, depending significantly on the direction of film growth. With the addition of small amounts of metal atoms (x<0.2), no films appear isotropic nor homogeneous through the metal/insulator transition. The results indicate that fluctuations in the growth direction play a pivotal role in preventing simple growth models of a columnar structure or one that evolves systematically as it grows. The anomalous scattering measurements identify the metal atoms (Fe or Mo) as the source of the anisotropy, with the Ge atoms distributed homogeneously. The author has developed a method for using these measurements to determine the compositions of the phase-separating species. The results indicate phase separation into an amorphous Ge and an intermetallic phase of stoichiometry close to FeGe2or MoGe3. Finally, by manipulating the deposited power flux and rates of growth, FexGe1-x films which have the same Fe composition x can be grown to different states of phase separation. These results may help explain the difficulty workers have had in isolating the metal/insulator transition for these and other vapor-deposited amorphous alloys.

  20. Conformal growth of Mo/Si multilayers on grating substrates using collimated ion beam sputtering

    SciTech Connect

    Voronov, D. L.; Gawlitza, Peter; Cambie, Rossana; Dhuey, Scott; Gullikson, Eric M.; Warwick, Tony; Braun, Stefan; Yashchuk, Valeriy V.; Padmore, Howard A.

    2012-05-07

    Deposition of multilayers on saw-tooth substrates is a key step in the fabrication of multilayer blazed gratings (MBG) for extreme ultraviolet and soft x-rays. Growth of the multilayers can be perturbed by shadowing effects caused by the highly corrugated surface of the substrates, which results in distortion of the multilayer stack structure and degradation of performance of MBGs. In this study, to minimize the shadowing effects, we used an ion-beamsputtering machine with a highly collimated atomic flux to deposit Mo/Si multilayers on saw-tooth substrates. The sputtering conditions were optimized by finding a balance between smoothening and roughening processes in order to minimize degradation of the groove profile in the course of deposition and at the same time to keep the interfaces of a multilayer stack smooth enough for high efficiency. An optimal value of energy of 200 eV for sputtering Kr+ ions was found by deposition of test multilayers on flat substrates at a range of ion energies. Two saw-tooth substrates were deposited at energies of 200 eV and 700 eV for the sputtering ions. It was found that reduction of the ion energy improved the blazing performance of the MBG and resulted in a 40% gain in the diffraction efficiency due to better replication of the groove profile by the multilayer. As a result of the optimization performed, an absolute diffraction efficiency of 28.8% was achieved for the 2nd blaze order of the MBG with a groove density of 7350 lines/mm at a wavelength of 13.5 nm. Lastly, details of the growth behavior of the multilayers on flat and saw-tooth substrates are discussed in terms of the linear continuous model of film growth.

  1. Conformal growth of Mo/Si multilayers on grating substrates using collimated ion beam sputtering

    SciTech Connect

    Voronov, D. L.; Cambie, R.; Dhuey, S.; Gullikson, E. M.; Warwick, T.; Yashchuk, V. V.; Padmore, H. A.; Gawlitza, P.; Braun, S.

    2012-05-01

    Deposition of multilayers on saw-tooth substrates is a key step in the fabrication of multilayer blazed gratings (MBG) for extreme ultraviolet and soft x-rays. Growth of the multilayers can be perturbed by shadowing effects caused by the highly corrugated surface of the substrates, which results in distortion of the multilayer stack structure and degradation of performance of MBGs. To minimize the shadowing effects, we used an ion-beam sputtering machine with a highly collimated atomic flux to deposit Mo/Si multilayers on saw-tooth substrates. The sputtering conditions were optimized by finding a balance between smoothening and roughening processes in order to minimize degradation of the groove profile in the course of deposition and at the same time to keep the interfaces of a multilayer stack smooth enough for high efficiency. An optimal value of energy of 200 eV for sputtering Kr{sup +} ions was found by deposition of test multilayers on flat substrates at a range of ion energies. Two saw-tooth substrates were deposited at energies of 200 eV and 700 eV for the sputtering ions. It was found that reduction of the ion energy improved the blazing performance of the MBG and resulted in a 40% gain in the diffraction efficiency due to better replication of the groove profile by the multilayer. As a result of the optimization performed, an absolute diffraction efficiency of 28.8% was achieved for the 2nd blaze order of the MBG with a groove density of 7350 lines/mm at a wavelength of 13.5 nm. Details of the growth behavior of the multilayers on flat and saw-tooth substrates are discussed in terms of the linear continuous model of film growth.

  2. Ion effects in hydrogen-induced blistering of Mo/Si multilayers

    SciTech Connect

    Kuznetsov, A. S.; Gleeson, M. A.; Bijkerk, F.

    2013-09-21

    The role that energetic (>800 eV) hydrogen ions play in inducing and modifying the formation of blisters in nanoscale Mo/Si multilayer samples is investigated. Such samples are confirmed to be susceptible to blistering by two separate mechanisms. The first is attributed to the segregation of H atoms to voids and vacancies associated with the outermost Mo layer, driving blister formation in the form of H{sub 2} filled bubbles. This process can occur in the absence of ions. A second blister distribution emerges when energetic ions are present in the irradiating flux. This is attributed to an ion-induced vacancy clustering mechanism that produces void blisters. The defects and strained states associated with the Mo-on-Si interfaces provide the preferred nucleation points for blistering in both cases. The effects of ions are ascribed to promotion of hydrogen uptake and mobility, in particular through the Si layers; to the generation of additional mobile species in the Si and Mo layers; and to the creation of new blister nucleation points. In addition to directly stimulating blistering via vacancy clustering, ions modify the development of H{sub 2}-filled blisters. This is most evident in the formation of multi-component structures due to overlapping delaminations at different layer interfaces. This affect is attributed to the introduction of active transport of hydrogen from the H{sub 2} filled blisters across the outermost Mo-on-Si interface to the underlying layers. Ion-induced variations in hydrogen uptake and distribution and in the rates of blister nucleation and growth produce lateral differences in blister size and areal number density that create a macroscopic concentric pattern across the surface.

  3. Plastic deformation of directionally solidified ingots of binary and some ternary MoSi2/Mo5Si3 eutectic composites.

    PubMed

    Matsunoshita, Hirotaka; Sasai, Yuta; Fujiwara, Kosuke; Kishida, Kyosuke; Inui, Haruyuki

    2016-01-01

    The high-temperature mechanical properties of directionally solidified (DS) ingots of binary and some ternary MoSi2/Mo5Si3 eutectic composites with a script lamellar structure have been investigated as a function of loading axis orientation and growth rate in a temperature range from 900 to 1500°C. These DS ingots are plastically deformed above 1000 and 1100 °C when the compression axis orientations are parallel to [1[Formula: see text]0]MoSi2 (nearly parallel to the growth direction) and [001]MoSi2, respectively. [1[Formula: see text]0]MoSi2-oriented DS eutectic composites are strengthened so much by forming a script lamellar microstructure and they exhibit yield stress values several times higher than those of MoSi2 single crystals of the corresponding orientation. The yield stress values increase with the decrease in the average thickness of MoSi2 phase in the script lamellar structure, indicating that microstructure refinement is effective in obtaining better high-temperature strength of these DS eutectic composites. Among the four ternary alloying elements tested (V, Nb, Ta and W), Ta is found to be the most effective in obtaining higher yield strength at 1400 °C.

  4. Manufacturing of Composite Coatings by Atmospheric Plasma Spraying Using Different Feed-Stock Materials as YSZ and MoSi2

    NASA Astrophysics Data System (ADS)

    Koch, D.; Mauer, G.; Vaßen, R.

    2017-02-01

    Yttria-stabilized zirconia (YSZ) is the state-of-the-art material for the top coat of thermal barrier coatings. To increase the efficiency and lifetime of gas turbines, the integration of MoSi2 as a healing material was proposed. A new method of manufacture was explored in order to enable the spraying of a homogeneous mixed layer of YSZ and MoSi2. As the chemical and physical properties of these powders are very different, they require contrasting process conditions. Due to the evaporation of Si from MoSi2 at spraying conditions suitable for YSZ, more moderate conditions and a shorter time of flight are required for depositing MoSi2. At the same time, the spraying conditions still need to be sufficient for melting the YSZ particles in order to produce a coating. To obtain a homogeneous mixture, both conditions can be matched using an injection system that allows powder injection at two different locations of the plasma jet. Two-color pyrometry during flight (DPV-2000, Tecnar) was used to monitor the actual particle temperature. By optimizing the injection point for the MoSi2, a mixed coating was obtained without decomposition of the MoSi2, which has been analyzed by means of XRD and SEM.

  5. Surface modification of a MoSiON phase shift mask to reduce critical dimension variation after exposure to a 193-nm ArF excimer laser

    NASA Astrophysics Data System (ADS)

    Choo, Hyeokseong; Seo, Dongwan; Lim, Sangwoo

    2014-08-01

    Introduction of a MoSi-based phase shift mask (PSM) improves photolithography resolution by causing light to shift phase by 180° thus canceling the overlap. However, when MoSiON PSM was exposed to an ArF excimer laser (λ = 193 nm), a significant increase in patterned critical dimension (CD) was observed. It was confirmed that the CD increase resulted from oxidation progression into the MoSiON layer. In this study, N2O or NH3 plasma treatment and thermal annealing in NH3 effectively suppressed CD variation after ArF laser exposure. While the compositional ratio of Si, N, O, and Mo elements in the MoSiON layer was not changed, an increase in oxygen content only in the top 5 nm was observed. Therefore, it is concluded that slight oxidation of the top surface of MoSiON PSM by introducing either N2O or NH3 plasma treatment or thermal annealing in NH3 suppresses an increase in the patterned CD of MoSiON PSM after exposure to a 193-nm ArF excimer laser.

  6. Manufacturing of Composite Coatings by Atmospheric Plasma Spraying Using Different Feed-Stock Materials as YSZ and MoSi2

    NASA Astrophysics Data System (ADS)

    Koch, D.; Mauer, G.; Vaßen, R.

    2017-04-01

    Yttria-stabilized zirconia (YSZ) is the state-of-the-art material for the top coat of thermal barrier coatings. To increase the efficiency and lifetime of gas turbines, the integration of MoSi2 as a healing material was proposed. A new method of manufacture was explored in order to enable the spraying of a homogeneous mixed layer of YSZ and MoSi2. As the chemical and physical properties of these powders are very different, they require contrasting process conditions. Due to the evaporation of Si from MoSi2 at spraying conditions suitable for YSZ, more moderate conditions and a shorter time of flight are required for depositing MoSi2. At the same time, the spraying conditions still need to be sufficient for melting the YSZ particles in order to produce a coating. To obtain a homogeneous mixture, both conditions can be matched using an injection system that allows powder injection at two different locations of the plasma jet. Two-color pyrometry during flight (DPV-2000, Tecnar) was used to monitor the actual particle temperature. By optimizing the injection point for the MoSi2, a mixed coating was obtained without decomposition of the MoSi2, which has been analyzed by means of XRD and SEM.

  7. Plastic deformation of directionally solidified ingots of binary and some ternary MoSi2/Mo5Si3 eutectic composites

    PubMed Central

    Matsunoshita, Hirotaka; Sasai, Yuta; Fujiwara, Kosuke; Kishida, Kyosuke; Inui, Haruyuki

    2016-01-01

    Abstract The high-temperature mechanical properties of directionally solidified (DS) ingots of binary and some ternary MoSi2/Mo5Si3 eutectic composites with a script lamellar structure have been investigated as a function of loading axis orientation and growth rate in a temperature range from 900 to 1500°C. These DS ingots are plastically deformed above 1000 and 1100 °C when the compression axis orientations are parallel to [11¯0]MoSi2 (nearly parallel to the growth direction) and [001]MoSi2, respectively. [11¯0]MoSi2-oriented DS eutectic composites are strengthened so much by forming a script lamellar microstructure and they exhibit yield stress values several times higher than those of MoSi2 single crystals of the corresponding orientation. The yield stress values increase with the decrease in the average thickness of MoSi2 phase in the script lamellar structure, indicating that microstructure refinement is effective in obtaining better high-temperature strength of these DS eutectic composites. Among the four ternary alloying elements tested (V, Nb, Ta and W), Ta is found to be the most effective in obtaining higher yield strength at 1400 °C. PMID:27877900

  8. Development of Tough, Strong, and Pest-Resistant MoSi2-(Beta)Si3N4 Composites for High-Temperature Structural Applications

    NASA Technical Reports Server (NTRS)

    Hebsur, M. G.; Choi, S. R.; Whittenberger, J. D.; Salem, J. A.; Noebe, R. D.

    2001-01-01

    A new MoSi2-base composite was developed that contains in-situ reinforcement of whisker-type beta-Si3N4 grains in a MoSi2 matrix. The advantages of this in-situ reinforced MoSi2-Si3N4 are lower density, higher fracture toughness and better strength than typical MoSi2 alloys, combined with excellent environmental and pest resistance. The average fracture toughness of the in-situ reinforced material determined by one technique was 12.2 MPa.m(exp 1/2) compared to 4.9 to 5.5 MPa.m(exp 1/2) for similar materials with the exception that the beta-Si3N4 had a blocky morphology as opposed to the whisker-like morphology typical of the in-situ toughened material. This MoSi2-(beta)Si3N4 was also resistant to pesting at intermediate temperatures (400 to 600 C) even when precracked or under applied load; conditions that would quickly reduce typical MoSi2 alloys to oxidized powder.

  9. A sintering model for SiC(sub)w/Si3N4 composites

    NASA Technical Reports Server (NTRS)

    Freedman, Marc R.; Kiser, James D.; Sanders, William A.

    1988-01-01

    Presented is a model which suggests that it should be possible to pressureless sinter a SiC(sub w)/ Si3N4 composite to theoretical density. Prior failure to achieve complete densification by sintering is attributed to the use of compositions which result in a glass deficit. There is one basic premise for this model. The ratio of glass amount to surface area of nonglass constituents must be the same for both composite and sinterable monolithic Si3N4. This model suggests that whisker and grain sizes and whisker loading influence the glass amount necessary for successful sintering of composites. According to the model, a large glass amount will be necessary for successful sintering of these composites. However, grain boundary thicknesses in the composite will be less than those in the analogous monolithic materials. This suggests that good high temperature strength may still be attained. A recent report supports the predictions of the model.

  10. Effects of Wet Air and Synthetic Combustion Gas Atmospheres on the Oxidation Behavior of Mo-Si-B Alloys

    SciTech Connect

    Kramer, M.J.; Thom, A.J.; Mandal, P.; Behrani, V.; Akinc, M.

    2003-04-24

    Continuing our work on understanding the oxidation behavior of multiphase composite alloys based on the Mo-Si-B system, we investigated three alloys in the Mo-Si-B system, designated as A1, A2, and A3. The nominal phase assemblages of these alloys are: A1 = Mo{sub 5}Si{sub 3}B{sub x} (T1)-MoSi{sub 2}-MoB, A2 = T1-Mo{sub 5}SiB{sub 2} (T2)-Mo{sub 3}Si, and A3 = Mo-T2-Mo{sub 3}Si. Our previous work showed that for exposures to 1100 C, all alloys formed a protective oxide scale in dry air. Exposures to wet air containing about 150 Torr water promoted the formation of a multiphase layer near the scale/alloy interface composed of Mo and MoO{sub 2}. Interrupted mass loss measurements indicated a near zero mass change. In the present study, isothermal mass measurements were conducted in order to quantitatively determine the oxidation rate constants at 1000 C in both dry and wet air. These measurements are critical for understanding the nature of scale development during the initial exposure, as well as the nature of scale stability during the long-term exposure. Isothermal measurements were also conducted at 1600 C in dry air to make an initial determination of alloy stability with respect to Vision 21 goals. We also conducted alloy oxidation testing in a synthetic oxidizing combustion atmosphere. Alloys were exposed up to 300 hours at 1100 C to a gas mixture having an approximate gas composition of N{sub 2} - 13 CO{sub 2} - 10 H{sub 2}O - 4 O{sub 2}. This gas composition simulates oxidizing flue gas, but does not contain a sulfidizing agent that would also be present in flue gas. The oxidized samples were carefully analyzed by SEM/EDS. This analysis will be discussed to provide an understanding of the role of water vapor and the synthetic combustion atmosphere on the oxidative stability of Mo-Si-B alloys.

  11. Fabrication and characterization of a Mo/Si multilayer monochromator with a narrow spectral bandwidth in the xuv domain

    NASA Astrophysics Data System (ADS)

    Benbalagh, Rabah; André, Jean-Michel; Barchewitz, Robert; Ravet, Marie-Françoise; Raynal, Alain; Delmotte, Frank; Bridou, Françoise; Julié, Gwaénäelle; Bosseboeuf, Alain; Laval, René; Troussel, Philippe

    2001-02-01

    A new kind of xuv multilayer monochromator with a narrow spectral bandwidth is introduced. This monochromator is based on a Mo/Si multilayer mirror etched according to the profile of a lamellar grating. The fabrication of such a device involving multilayer deposition, UV lithography and reactive ion etching is presented. The monochromator has been characterized by means of the synchrotron radiation around the Si-L edge (100 eV). A reduction of the bandwidth has been observed with respect to the unpatterned mirror by a factor close to 3.

  12. Inorganic molecular-scale MoSI nanowire-gold nanoparticle networks exhibit self-organized critical self-assembly.

    PubMed

    Strle, Jure; Vengust, Damjan; Mihailovic, Dragan

    2009-03-01

    We investigate for the first time the topological characteristics of large molecular-scale inorganic networks self-assembled in solution using the unique sulfur-bonding chemistry of conducting MoSI molecular wires and gold nanoparticles (GNPs). The network self-assembly is shown to display power-law distribution of graph edges, indicating an intrinsic tendency to self-organize into scale-invariant critical state, without any external control parameter. We discuss the electronic transport properties of such networks particularly with regard to the possibility of data processing.

  13. Comparison of ZrB2-MoSi2 Composite Coatings Fabricated by Atmospheric and Vacuum Plasma Spray Processes

    NASA Astrophysics Data System (ADS)

    Niu, Yaran; Wang, Zhong; Zhao, Jun; Zheng, Xuebin; Zeng, Yi; Ding, Chuanxian

    2017-01-01

    In this work, ZrB2-20 vol.% MoSi2 (denoted as ZM) composite coatings were fabricated by atmospheric plasma spray (APS) and vacuum plasma spray (VPS) techniques, respectively. Phase composition and microstructure of the composite coatings were characterized. Their oxidation behaviors and microstructure changes at 1500 °C were comparatively investigated. The results showed that VPS-ZM coating was composed of hexagonal ZrB2, tetragonal and hexagonal MoSi2, while certain amount of ZrO2 existed in APS-ZM coating. The oxide content, surface roughness and porosity of VPS-ZM coating were apparently lower than those of APS-ZM coating. The mass gain of APS-ZM coating was maximum at the beginning (1500 °C, 0 h) and then decreased with the oxidation time extending, while the mass of VPS-ZM coating gradually increased with increasing the oxidation time. The possible reasons for the different oxidation behaviors of the two kinds of coatings were analyzed.

  14. PLASMA SPRAYED FUNCTIONALLY GRADED AND LAYERED MoSi2-A1203 COMPOSITES FOR HIGH TEMPERATURE SENSOR SHEATH APPLICATION

    SciTech Connect

    R. VAIDYA; ET AL

    2001-01-01

    Protective sensor sheaths are required in the glass industry for sensors that are used to measure various properties of the melt. Molten glass presents an extremely corrosive elevated temperature environment, in which only a few types of materials can survive. Molybdenum disilicide (MoSi{sub 2}) has been shown to possess excellent corrosion resistance in molten glass, and is thus a candidate material for advanced sensor sheath applications. Plasma spray-forming techniques were developed to fabricate molybdenum dilicide-alumina (Al{sub 2}O{sub 3}) laminate and functionally graded composite tubes with mechanical properties suitable for sensor sheath applications. These functionally graded materials (FGMs) were achieved by manipulating the powder hoppers and plasma torch translation via in-house created computer software. Molybdenum disilicide and alumina are thermodynamically stable elevated temperature materials with closely matching thermal expansion coefficients. Proper tailoring of the microstructure of these MoSi{sub 2}-Al{sub 2}O{sub 3} composites can result in improved strength, toughness, and thermal shock resistance. This study focuses on the mechanical performance of these composite microstructures.

  15. Synergistic toughening of hard, nacre-mimetic MoSi2 coatings by self-assembled hierarchical structure

    NASA Astrophysics Data System (ADS)

    Xu, Jiang; Zhao, Xiaoli; Munroe, Paul; Xie, Zonghan

    2014-02-01

    Like many other intermetallic materials, MoSi2 coatings are typically hard, but prone to catastrophic failure due to their low toughness at ambient temperature. In this paper, a self-assembled hierarchical structure that closely resembles that of nacre (i.e., mother of pearl) was developed in a MoSi2-based coating through a simple, yet cost-effective, depostion technique. The newly formed coating is tough and can withstand multiple indentations at high loads. Key design features responsible for this remarkable outcome were identified. They include a functionally graded multilayer featuring elastic modulus oscillation, varying sublayer thickness and a columnar structure that are able to attenuate stress concentrations; interlocking boundaries between adjacent sublayers that improve the bonding and arrest the cracks; a transitional layer that bridges the coating and substrate and facilitates load transfer. Moreover, the contributions of six important structural characteristics to damage resistance are quantified using finite elemnet analysis and in an additive manner (i.e., from low- to high-level complexity). The in-situ toughened coating is envisaged to enhance the mechanical performance and extend the lifespan of metal components used in safety-critical applications.

  16. Synergistic toughening of hard, nacre-mimetic MoSi2 coatings by self-assembled hierarchical structure.

    PubMed

    Xu, Jiang; Zhao, Xiaoli; Munroe, Paul; Xie, Zonghan

    2014-02-28

    Like many other intermetallic materials, MoSi2 coatings are typically hard, but prone to catastrophic failure due to their low toughness at ambient temperature. In this paper, a self-assembled hierarchical structure that closely resembles that of nacre (i.e., mother of pearl) was developed in a MoSi2-based coating through a simple, yet cost-effective, depostion technique. The newly formed coating is tough and can withstand multiple indentations at high loads. Key design features responsible for this remarkable outcome were identified. They include a functionally graded multilayer featuring elastic modulus oscillation, varying sublayer thickness and a columnar structure that are able to attenuate stress concentrations; interlocking boundaries between adjacent sublayers that improve the bonding and arrest the cracks; a transitional layer that bridges the coating and substrate and facilitates load transfer. Moreover, the contributions of six important structural characteristics to damage resistance are quantified using finite elemnet analysis and in an additive manner (i.e., from low- to high-level complexity). The in-situ toughened coating is envisaged to enhance the mechanical performance and extend the lifespan of metal components used in safety-critical applications.

  17. Synergistic toughening of hard, nacre-mimetic MoSi2 coatings by self-assembled hierarchical structure

    PubMed Central

    Xu, Jiang; Zhao, Xiaoli; Munroe, Paul; Xie, Zonghan

    2014-01-01

    Like many other intermetallic materials, MoSi2 coatings are typically hard, but prone to catastrophic failure due to their low toughness at ambient temperature. In this paper, a self-assembled hierarchical structure that closely resembles that of nacre (i.e., mother of pearl) was developed in a MoSi2-based coating through a simple, yet cost-effective, depostion technique. The newly formed coating is tough and can withstand multiple indentations at high loads. Key design features responsible for this remarkable outcome were identified. They include a functionally graded multilayer featuring elastic modulus oscillation, varying sublayer thickness and a columnar structure that are able to attenuate stress concentrations; interlocking boundaries between adjacent sublayers that improve the bonding and arrest the cracks; a transitional layer that bridges the coating and substrate and facilitates load transfer. Moreover, the contributions of six important structural characteristics to damage resistance are quantified using finite elemnet analysis and in an additive manner (i.e., from low- to high-level complexity). The in-situ toughened coating is envisaged to enhance the mechanical performance and extend the lifespan of metal components used in safety-critical applications. PMID:24577416

  18. Structural properties of reactively sputtered W-Si-N thin films

    SciTech Connect

    Vomiero, A.; Boscolo Marchi, E.; Quaranta, A.; Della Mea, G.; Brusa, R. S.; Mariotto, G.; Felisari, L.; Frabboni, S.; Tonini, R.; Ottaviani, G.; Mattei, G.; Scandurra, A.; Puglisi, O.

    2007-08-01

    Tungsten-silicon-nitrogen, W-Si-N, ternary thin films have been reactively sputter deposited from W{sub 5}Si{sub 3} and WSi{sub 2} targets using several nitrogen partial pressures. The films have been thermal annealed in the 600-1000 deg. C temperature range and a wide region of the W-Si-N ternary phase diagram has been explored by changing the N{sub 2}/Ar ratio during the deposition. Multitechnique approach was adopted for the analysis of the samples. Composition has been determined via ion beam analysis; chemical states were investigated using x-ray photoelectron spectroscopy (XPS); crystalline structure was studied using transmission electron microscopy (TEM) and x-ray diffraction (XRD) and surface morphology by scanning electron microscope. The films deposited in pure argon atmosphere are tungsten rich and approach the target contents as N{sub 2}/Ar ratio is varied during deposition. Tungsten enrichment in the films is caused by resputtering of silicon which can be inhibited by the formation of silicon nitride, allowing films with Si/W ratio closer to the target compositions. The higher capability to form nitrides with silicon than with tungsten favors enhancement of nitrogen content in samples deposited from the silicon rich target (WSi{sub 2}). The samples with excess nitrogen content have shown losses of this element after thermal treatment. XPS measurements show a break of W-N bonds caused by thermal instability of tungsten nitrides. TEM and XRD revealed the segregation of tungsten in form of metallic or silicide nanoclusters in samples with low nitrogen content (W{sub 58}Si{sub 21}N{sub 21} and W{sub 24}Si{sub 42}N{sub 34}). High amounts of nitrogen were revealed to be highly effective in inhibiting metallic cluster coalescence. Measurements of electrical resistivity of as deposited films were performed using four point probe technique. They were found to lie in the range between 0.4 and 79 m{omega} cm depending on sample composition.

  19. In-situ and real time stress of 30.4 nm Mo/Si multilayer mirror for the moon-based EUV Camera

    NASA Astrophysics Data System (ADS)

    Li, Yun-peng; Chen, Bo; He, Fei; Yang, Hua-bin; Wang, Xiao-duo; Zheng, Xin; Wang, Xiao-dong; Zhang, Hong-ji; Wang, Hai-feng; Cao, Jian-lin

    2014-12-01

    Applications of Mo/Si multilayer mirrors for the moon-based extreme ultraviolet Camera (EUVC) require not only the minimal residual stress, but also little stress changes in the temperature environment on lunar surface. Hence, we deposit the 16.5 nm period Mo/Si multilayer mirror with a low as-deposited residual stress of -36 Mpa (compressive). The in-situ and real time stress tests are measured in the temperature cycling range from 20 °C to 130 °C. The results indicate that the stress gradually increases to the maximum of -100 MPa when heating up to 105 °C, then it gradually relaxes to 10 Mpa after thermal cycling to 130 °C. Such stress change has little influence on the performance of the Mo/Si multilayer mirror.

  20. Demonstration of the high collection efficiency of a broadband Mo/Si multilayer mirror with a graded multilayer coating on an ellipsoidal substrate

    NASA Astrophysics Data System (ADS)

    Ichimaru, S.; Takenaka, H.; Namikawa, K.; Gullikson, E. M.; Maruyama, M.; Oku, S.

    2015-09-01

    A graded and broadband Mo/Si multilayer mirror for EUV spectroscopy is demonstrated. This mirror has an average reflectivity profile of 16% in the wavelength region from 15 nm to 17 nm and an effective area of 1100-1500 mm2. This reflectivity is about 4 times larger than that of a standard Mo/Si multilayer mirror on a 1 in. diameter substrate, showing that the mirror can be used for measuring EUV fluorescence at wavelengths in the region around 15 nm to 17 nm.

  1. Demonstration of the high collection efficiency of a broadband Mo/Si multilayer mirror with a graded multilayer coating on an ellipsoidal substrate.

    PubMed

    Ichimaru, S; Takenaka, H; Namikawa, K; Gullikson, E M; Maruyama, M; Oku, S

    2015-09-01

    A graded and broadband Mo/Si multilayer mirror for EUV spectroscopy is demonstrated. This mirror has an average reflectivity profile of 16% in the wavelength region from 15 nm to 17 nm and an effective area of 1100-1500 mm(2). This reflectivity is about 4 times larger than that of a standard Mo/Si multilayer mirror on a 1 in. diameter substrate, showing that the mirror can be used for measuring EUV fluorescence at wavelengths in the region around 15 nm to 17 nm.

  2. An Analysis of Shock-Compression in Mo-Si Powder Mixtures Using Recovery and Time-Resolved Measurements

    NASA Astrophysics Data System (ADS)

    Vandersall, Kevin S.; Thadhani, Naresh N.

    1999-06-01

    The densification and reaction characteristics in the Mo-Si system were investigated utilizing recovery experiments as well as time resolved measurements with in-situ stress gages. The starting sample in all cases consisted of statically pressed Mo + 2 Si powder mixtures ( ~55% TMD). The recovery experiments were performed using the Sandia Momma Bear and Momma Bear A fixtures with baratol and composition B explosives respectively. The instrumented experiments were performed in a capsule design similar to that of the Momma Bear, but modified to incorporate poly-vinyl di-flouride (PVDF) stress gages at the front and rear surfaces of the powder. These experiments were performed using a single stage gas gun in the velocity range of 500 m/s to 1 km/s. The instrumented experiments allow the crush strength, densification history, and reaction threshold to be mapped at increasing pressure to correlate with reaction observed in the recovery experiments.

  3. Understanding Influence of MoSi2 Addition (5 Weight Percent) on Tribological Properties of TiB2

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, Amartya; Raju, G. B.; Basu, Bikramjit

    2008-12-01

    In densifying engineering ceramics such as TiB2 using nonmetallic sinter additives, it is important to assess the influence of the addition of sinter-aid on the properties of TiB2. The present article reports how a small addition of MoSi2 (5 wt pct) sinter-aid enhances the wear resistance of TiB2 at mode-I fretting contact. This has been confirmed using a series of unlubricated wear tests on hot-pressed ceramics using two different counterbodies, viz. bearing steel and WC-6 wt pct Co cemented carbide, under identical testing conditions. Steady-state coefficient of friction (COF) against steel counterbody has been found to noticeably vary in the range of 0.5 to 1, with variation in load or MoSi2 addition. However, insignificant variation in COF (˜0.5) has been recorded during fretting against WC-Co. Furthermore, lower wear rate (˜10-6 mm3/Nm) is measured against the cemented carbide, as compared to that against steel (˜10-5 mm3/Nm). It has been observed that the material removal of TiB2-based ceramics against steel involves tribochemical wear as well as abrasive wear, and the occurrence of tribochemical wear is explained in terms of various feasible reactions at the tribological interface. Lower contact area, resulting in reduced adhesive wear, along with the absence of additional tribochemical wear, has been attributed to lower wear rate as observed after fretting against the harder (WC-Co) counterbody. A number of possible reactions along with their thermodynamic feasibility are discussed to explain the tribochemical wear at the interface of the mating couple. Irrespective of counterbody or material composition, the measured wear volume exhibits linear dependency on abrasion parameter, confirming the role of material parameters on the contribution of abrasive wear to the material removal/damage of the investigated materials.

  4. Thermal and stress studies of the 30.4 nm Mo/Si multilayer mirror for the moon-based EUV camera

    NASA Astrophysics Data System (ADS)

    Li, Yunpeng; Zhang, Hongji; Wang, Haifeng; He, Fei; Wang, Xiaodong; Liu, Yang; Han, Suli; Zheng, Xin; Wang, Xiaoduo; Chen, Bin; Li, Haibo; Chen, Bo; Cao, Jianlin

    2014-10-01

    To investigate the environmental adaptability of the Mo/Si multilayers on lunar surface, we studied the stability and stress of Mo/Si multilayers under the low and high temperature environment. The in-situ X-ray diffraction (XRD) and the ex-situ intrinsic stress are measured in the temperature range from -135 °C to 600 °C and from -190 °C to 600 °C, respectively. The results demonstrate that the periodic structure of Mo/Si multilayers is stable between -135 °C and 300 °C. The stress is unaffected under low temperature and it gradually increases from -260 MPa to 1G MPa when the temperature changes from room temperature to 600 °C. Above 600 °C, large tensile stress leads to folds and cracks in the film. Thus, the large temperature range on lunar surface has little effect on the structure, performance and stress of the Mo/Si multilayers and the high temperature in lunar day releases the stress of the multilayer mirror.

  5. SiC Nanoparticles Toughened-SiC/MoSi2-SiC Multilayer Functionally Graded Oxidation Protective Coating for Carbon Materials at High Temperatures

    NASA Astrophysics Data System (ADS)

    Abdollahi, Alireza; Ehsani, Naser; Valefi, Zia; Khalifesoltani, Ali

    2017-05-01

    A SiC nanoparticle toughened-SiC/MoSi2-SiC functionally graded oxidation protective coating on graphite was prepared by reactive melt infiltration (RMI) at 1773 and 1873 K under argon atmosphere. The phase composition and anti-oxidation behavior of the coatings were investigated. The results show that the coating was composed of MoSi2, α-SiC and β-SiC. By the variations of Gibbs free energy (calculated by HSC Chemistry 6.0 software), it could be suggested that the SiC coating formed at low temperatures by solution-reprecipitation mechanism and at high temperatures by gas-phase reactions and solution-reprecipitation mechanisms simultaneously. SiC nanoparticles could improve the oxidation resistance of SiC/MoSi2-SiC multiphase coating. Addition of SiC nanoparticles increases toughness of the coating and prevents spreading of the oxygen diffusion channels in the coating during the oxidation test. The mass loss and oxidation rate of the SiC nanoparticle toughened-SiC/MoSi2-SiC-coated sample after 10-h oxidation at 1773 K were only 1.76% and 0.32 × 10-2 g/cm3/h, respectively.

  6. Matrix grain characterisation by electron backscattering diffraction of powder metallurgy aluminum matrix composites reinforced with MoSi{sub 2} intermetallic particles

    SciTech Connect

    Corrochano, J. Hidalgo, P.; Lieblich, M.; Ibanez, J.

    2010-11-15

    Research highlights: Six extruded PM AA6061/MoSi{sub 2}/15p were processed with and without ball milling {yields} EBSD was used to characterise matrix grain size and grain orientation. {yields} Ball milling decreases matrix grain size to submicrometric level. {yields} Ball milling produces a more equiaxed microstructure and larger misorientation. {yields} Increasing milling time produces matrix texture randomization.

  7. Characterization of ion beam sputtered deposited W/Si multilayers by grazing incidence x-ray diffraction and x-ray reflectivity technique

    SciTech Connect

    Dhawan, Rajnish Rai, Sanjay

    2016-05-23

    W/Si multilayers four samples have been deposited on silicon substrate using ion beam sputtering system. Thickness of tungsten (W) varies from around 10 Å to 40 Å while the silicon (Si) thickness remains constant at around 30 Å in multilayers [W-Si]{sub x4}. The samples have been characterized by grazing incidence X-ray diffraction (GIXRD) and X-ray reflectivity technique (XRR). GIXRD study shows the crystalline behaviour of W/Si multilayer by varying W thickness and it is found that above 20 Å the W film transform from amorphous to crystalline phase and X-ray reflectivity data shows that the roughnesses of W increases on increasing the W thicknesses in W/Si multilayers.

  8. 248-nm DUV MoSiON embedded phase-shifting mask for 0.25 micrometer lithography

    NASA Astrophysics Data System (ADS)

    Dao, Giang T.; Liu, Gang; Hainsey, Robert F.; Farnsworth, Jeff N.; Tokoro, Yasuo; Kawada, Susumu; Yamamoto, Tsuneo; Yoshioka, Nobuyuki; Chiba, Akira; Morimoto, Hiroaki

    1995-07-01

    Over the past five years worldwide efforts have been made to develop new techniques for optical lithography enhancement. These techniques include optical proximity correction, off-axis illumination, pupil filtering and phase-shifting mask (PSM). Among many phase-shifting mask approaches, embedded PSM (EPSM) method has drawn significant interest due to its relatively simple reticle fabrication process and excellent lithographic performance, in particular, for dark field mask layers such as contact and via holes. Perhaps, the most difficult task in materializing the EPSM technology is the creation of a thin film structure that controls both phase and transmission. In addition, this film structure must withstand severe environment of mask making process and yet can be inspected and repaired successfully using currently available tool sets. The newly developed MoSiON material meets these requirements and has demonstrated a feasibility for DUV EPSM pilot production. In this paper, characteristics of the DUV lifetime test results. Details of reticle fabrication process including e-beam writing, dry etching, inspection and repair will be presented along with chemical durability data and process capability. Finally, wafer level lithographic performance for contact holes printed on a step-and-scan and a projection aligner will be shown to demonstrate lithographic performance of 248 nm DUV EPSM for 0.25 micrometer lithography.

  9. Microstructure Characterization and Wear-Resistant Properties Evaluation of an Intermetallic Composite in Ni-Mo-Si System.

    PubMed

    Huang, Boyuan; Song, Chunyan; Liu, Yang; Gui, Yongliang

    2017-02-04

    Intermetallic compounds have been studied for their potential application as structural wear materials or coatings on engineering steels. In the present work, a newly designed intermetallic composite in a Ni-Mo-Si system was fabricated by arc-melting process with commercially pure metal powders as starting materials. The chemical composition of this intermetallic composite is 45Ni-40Mo-15Si (at %), selected according to the ternary alloy diagram. The microstructure was characterized using optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS), and the wear-resistant properties at room temperature were evaluated under different wear test conditions. Microstructure characterization showed that the composite has a dense and uniform microstructure. XRD results showed that the intermetallic composite is constituted by a binary intermetallic compound NiMo and a ternary Mo₂Ni₃Si metal silicide phase. Wear test results indicated that the intermetallic composite has an excellent wear-resistance at room-temperature, which is attributed to the high hardness and strong atomic bonding of constituent phases NiMo and Mo₂Ni₃Si.

  10. High damping Al-Fe-Mo-Si/Zn-Al composites produced by rapidly solidified powder metallurgy process

    SciTech Connect

    Li, P.Y.; Dai, S.L.; Chai, S.C.; Li, Y.R.

    2000-05-10

    The metallic materials commonly used in aircraft and aerospace fields, such as aluminum and titanium alloys, steels, etc., show extremely low damping capacity (usually of the order of or less than 10{sup {minus}3}). Thus, some problems related to vibration may emerge and influence the reliability, safety and life of airplanes, satellites, etc. It has been reported that almost two thirds of errors for rockets and satellites are related to vibration and noise. One effective way to solve these vibration-related problems is to adopt high damping metallic materials. Conventional high damping alloys exhibit damping capacity above 10{sup {minus}2}, however, their densities are usually great than 5 x 10{sup 3} kg m{sup {minus}3}, or their strengths are less than 200 MPa (for alloys based on dislocation damping), making them impossible to be applied to aircraft and aerospace areas. Recently, some low-density high-damping metal/metal composites based on aluminum and high damping alloys have been developed in Beijing Institute of Aeronautical Materials (BIAM) by the rapidly solidified power metallurgy process. This paper aims to report the properties of the composites based on a high temperature Al-Fe-Mo-Si alloy and a high damping Zn-Al alloy, and compare them with that of 2618-T61 alloy produced by the ingot metallurgy process.

  11. Mo/Si multilayer-coated amplitude-division beam splitters for XUV radiation sources

    PubMed Central

    Sobierajski, Ryszard; Loch, Rolf Antonie; van de Kruijs, Robbert W. E.; Louis, Eric; von Blanckenhagen, Gisela; Gullikson, Eric M.; Siewert, Frank; Wawro, Andrzej; Bijkerk, Fred

    2013-01-01

    Amplitude-division beam splitters for XUV radiation sources have been developed and extensively characterized. Mo/Si multilayer coatings were deposited on 50 nm-thick SiN membranes. By changing the multilayer structure (periodicity, number of bilayers, etc.) the intensity of the reflected and transmitted beams were optimized for selected incident radiation parameters (wavelength, incident angle). The developed optical elements were characterized by means of XUV reflectometry and transmission measurements, atomic force microscopy and optical interferometry. Special attention was paid to the spatial homogeneity of the optical response and reflected beam wavefront distortions. Here the results of the characterization are presented and improvements required for advanced applications at XUV free-electron lasers are identified. A flatness as low as 4 nm r.m.s. on 3 × 3 mm beam splitters and 22 nm r.m.s. on 10 × 10 mm beam splitters has been obtained. The high-spatial-frequency surface roughness was about 0.7–1 nm r.m.s. The middle-spatial-frequency roughness was in the range 0.2–0.8 nm r.m.s. The reflection and transmission of the beam splitters were found to be very homogeneous, with a deviation of less than 2% across the full optical element. PMID:23412481

  12. Structural size effects of intermetallic compounds on the mechanical properties of Mo-Si-B alloy: An experimental investigation

    NASA Astrophysics Data System (ADS)

    Byun, Jong Min; Bang, Su-Ryong; Park, Chun Woong; Suk, Myung-Jin; Kim, Young Do

    2016-01-01

    In general, size, shape and dispersion of phases in alloys significantly affect mechanical properties. In this study, the mechanical properties of Mo-Si-B alloys were experimentally investigated with regards to the refinement of intermetallic compound. To confirm the size effect of the intermetallic compound phases on mechanical properties, two differently sized intermetallic compound powders consisting Mo5SiB2 and Mo3Si were fabricated by mechano-chemical process and high-energy ball milling. A modified powder metallurgy method was used with core-shell intermetallic powders where the intermetallic compound particles were the core and nano-sized Mo particles which formed by the hydrogen reduction of Mo oxide were the shells, leading to the microstructures with uniformly distributed intermetallic compound phases within a continuous α-Mo matrix phase. Vickers hardness and fracture toughness were measured to examine the mechanical properties of sintered bodies. Vickers hardness was 472 Hv for the fine intermetallic compound powder and 415 Hv for the coarse intermetallic compound powder. The fracture toughness was 12.4 MPa·√m for the fine IMC powders and 13.5 MPa·√m for the coarse intermetallic compound powder.

  13. An ultra-high temperature Mo-Si-B based coating for oxidation protection of NbSS/Nb5Si3 composites

    NASA Astrophysics Data System (ADS)

    Su, Linfen; Lu-Steffes, Otto; Zhang, Hu; Perepezko, John H.

    2015-05-01

    A Mo-Si-B based coating was prepared on an NbSS/Nb5Si3 composite by a two-step process consisting of the initial deposition of Mo followed by pack cementation co-deposition of Si and B. After a conditioning treatment, an aluminoborosilica layer fully covered the sample. Following oxidation at 1300 °C for 24 h, the coated sample demonstrated a weight loss of about 0.55 mg/cm2 and the uncoated sample exhibited catastrophic oxidation with a weight gain of 87.6 mg/cm2. These results demonstrate that the Mo-Si-B based coating can enable the use of the NbSS/Nb5Si3 composites at temperature up to 1300 °C in an oxidizing environment.

  14. The Effect of Milling Time on the Microstructural Characteristics and Strengthening Mechanisms of NiMo-SiC Alloys Prepared via Powder Metallurgy.

    PubMed

    Yang, Chao; Muránsky, Ondrej; Zhu, Hanliang; Thorogood, Gordon J; Avdeev, Maxim; Huang, Hefei; Zhou, Xingtai

    2017-04-06

    A new generation of alloys, which rely on a combination of various strengthening mechanisms, has been developed for application in molten salt nuclear reactors. In the current study, a battery of dispersion and precipitation-strengthened (DPS) NiMo-based alloys containing varying amounts of SiC (0.5-2.5 wt %) were prepared from Ni-Mo-SiC powder mixture via a mechanical alloying (MA) route followed by spark plasma sintering (SPS) and rapid cooling. Neutron Powder Diffraction (NPD), Electron Back Scattering Diffraction (EBSD), and Transmission Electron Microscopy (TEM) were employed in the characterization of the microstructural properties of these in-house prepared NiMo-SiC DPS alloys. The study showed that uniformly-dispersed SiC particles provide dispersion strengthening, the precipitation of nano-scale Ni₃Si particles provides precipitation strengthening, and the solid-solution of Mo in the Ni matrix provides solid-solution strengthening. It was further shown that the milling time has significant effects on the microstructural characteristics of these alloys. Increased milling time seems to limit the grain growth of the NiMo matrix by producing well-dispersed Mo₂C particles during sintering. The amount of grain boundaries greatly increases the Hall-Petch strengthening, resulting in significantly higher strength in the case of 48-h-milled NiMo-SiC DPS alloys compared with the 8-h-milled alloys. However, it was also shown that the total elongation is considerably reduced in the 48-h-milled NiMo-SiC DPS alloy due to high porosity. The porosity is a result of cold welding of the powder mixture during the extended milling process.

  15. The Effect of Milling Time on the Microstructural Characteristics and Strengthening Mechanisms of NiMo-SiC Alloys Prepared via Powder Metallurgy

    PubMed Central

    Yang, Chao; Muránsky, Ondrej; Zhu, Hanliang; Thorogood, Gordon J.; Avdeev, Maxim; Huang, Hefei; Zhou, Xingtai

    2017-01-01

    A new generation of alloys, which rely on a combination of various strengthening mechanisms, has been developed for application in molten salt nuclear reactors. In the current study, a battery of dispersion and precipitation-strengthened (DPS) NiMo-based alloys containing varying amounts of SiC (0.5–2.5 wt %) were prepared from Ni-Mo-SiC powder mixture via a mechanical alloying (MA) route followed by spark plasma sintering (SPS) and rapid cooling. Neutron Powder Diffraction (NPD), Electron Back Scattering Diffraction (EBSD), and Transmission Electron Microscopy (TEM) were employed in the characterization of the microstructural properties of these in-house prepared NiMo-SiC DPS alloys. The study showed that uniformly-dispersed SiC particles provide dispersion strengthening, the precipitation of nano-scale Ni3Si particles provides precipitation strengthening, and the solid-solution of Mo in the Ni matrix provides solid-solution strengthening. It was further shown that the milling time has significant effects on the microstructural characteristics of these alloys. Increased milling time seems to limit the grain growth of the NiMo matrix by producing well-dispersed Mo2C particles during sintering. The amount of grain boundaries greatly increases the Hall–Petch strengthening, resulting in significantly higher strength in the case of 48-h-milled NiMo-SiC DPS alloys compared with the 8-h-milled alloys. However, it was also shown that the total elongation is considerably reduced in the 48-h-milled NiMo-SiC DPS alloy due to high porosity. The porosity is a result of cold welding of the powder mixture during the extended milling process. PMID:28772747

  16. Corrosion of Si 3N 4-MoSi 2 ceramic composite in acid- and basic-aqueous environments: surface modification and properties degradation

    NASA Astrophysics Data System (ADS)

    Winterhalter, F.; Medri, V.; Ruffini, A.; Bellosi, A.

    2004-03-01

    The corrosion behaviour of an electroconductive Si 3N 4-35 vol.% MoSi 2 composite, hot pressed with the addition of Al 2O 3 and Y 2O 3 as sintering aids, was studied in 1.8 M sulphuric acid and 4 M sodium hydroxide aqueous solutions at room temperature, 40 and 70 °C up to 400 h. In acidic environment, the corrosion follows linear kinetics involving the progressive chemical dissolution of glassy grain boundary phases, in the system Al-Y-Si-O-N up to 40 °C. At 70 °C, the dissolution mechanism is hampered by the formation of a barrier that limits the transport of the aggressive cations towards the sites of chemical attack. In basic environment, the rate controlling step for corrosion of this ceramic composite is the chemical dissolution of MoSi 2. Si 3N 4 phase is less affected by the selected corrosive environments. The effect of the corrosion on electrical resistivity and flexural strength were investigated. The electrical resistivity rises after long term corrosion in line with the progressive chemical dissolution of grain boundary phase and of the electroconductive MoSi 2 particles. The flexural strength values are about 21 and 13% lower than the as-sintered ones, after a permanence of 400 °C at 70 °C in H 2SO 4 and in NaOH solutions, respectively.

  17. Development of a multi-variate calibration approach for quantitative analysis of oxidation resistant Mo-Si-B coatings using laser ablation inductively coupled plasma mass spectrometry

    NASA Astrophysics Data System (ADS)

    Cakara, Anja; Bonta, Maximilian; Riedl, Helmut; Mayrhofer, Paul H.; Limbeck, Andreas

    2016-06-01

    Nowadays, for the production of oxidation protection coatings in ultrahigh temperature environments, alloys of Mo-Si-B are employed. The properties of the material, mainly the oxidation resistance, are strongly influenced by the Si to B ratio; thus reliable analytical methods are needed to assure exact determination of the material composition for the respective applications. For analysis of such coatings, laser ablation inductively coupled mass spectrometry (LA-ICP-MS) has been reported as a versatile method with no specific requirements on the nature of the sample. However, matrix effects represent the main limitation of laser-based solid sampling techniques and usually the use of matrix-matched standards for quantitative analysis is required. In this work, LA-ICP-MS analysis of samples with known composition and varying Mo, Si and B content was carried out. Between known analyte concentrations and derived LA-ICP-MS signal intensities no linear correlation could be found. In order to allow quantitative analysis independent of matrix effects, a multiple linear regression model was developed. Besides the three target analytes also the signals of possible argides (40Ar36Ar and 98Mo40Ar) as well as detected impurities of the Mo-Si-B coatings (108Pd) were considered. Applicability of the model to unknown samples was confirmed using external validation. Relative deviations from the values determined using conventional liquid analysis after sample digestion between 5 and 10% for the main components Mo and Si were observed.

  18. Structure and stress studies of low temperature annealed W/Si multilayers for the X-ray telescope.

    PubMed

    Huang, Qiushi; Zhang, Jinshuai; Qi, Runze; Yang, Yang; Wang, Fengli; Zhu, Jie; Zhang, Zhong; Wang, Zhanshan

    2016-07-11

    Low stress W/Si multilayer mirrors are demanded in the hard X-ray telescopes to achieve the high angular resolution. To reduce the stress of the as-deposited multilayer and maintain a high reflectivity, two groups of low-temperature annealing experiments were performed on the periodic multilayers with a d-spacing of ~3.8 nm. The temperature-dependent experiments show that the 150 °C annealing can slightly increase the reflectivity while the stress reduced only by 24%. Higher temperature annealing induced a larger reduction of the stress and the multilayer reached an almost zero stress state at 250 °C. The stress relaxation was accompanied by a small drop of reflectivity of ≤5% and a period compaction of <0.02 nm. The time-dependent experiments indicate that most of the stress changes occurred within the first 10 minutes while a prolonged annealing is not useful. The X-ray scattering and transmission electron microscopy were further used to study the microstructure changes of the multilayers. It is found that the W/Si multilayer exhibits an amorphous structure before and after annealing, while an enhanced diffusion and intermixing is the main reason for the stress relaxation and structure changes.

  19. The effect of a weak W/SiC interface on the strength of sigma silicon carbide monofilament

    PubMed

    Dyos; Shatwell

    1999-11-01

    Fractography studies have shown that the strength-determining flaws in silicon carbide monofilaments are generally at the core/silicon carbide interface or in the vicinity of the outside, carbon-based coating. In tungsten-cored monofilaments like DERA Sigma, the W/SiC flaws primarily determine the strength. Fracture is accompanied by brittle failure of the tungsten. The crack propagates simultaneously outwards through the silicon carbide, inwards through the tungsten and also around the W/SiC interface before being deflected into the tungsten or out through the silicon carbide. Experiments depositing boundary layers between the tungsten and silicon carbide have resulted in significantly different fracture behaviour. The tungsten fails in a ductile manner and the strength-determining flaws are located predominantly at the outside surface of the silicon carbide. This behaviour is discussed in terms of models proposed by E. Martin and W. Curtin. It is thought that the work will ultimately lead to a significantly stronger, tungsten-based monofilament.

  20. Spectroscopic and structural characterization of chlorine loading effects on Mo/Si:Ti catalysts in oxidative dehydrogenation of ethane.

    PubMed

    Liu, Chang; Ozkan, Umit S

    2005-02-17

    The structural changes induced in a silica-titania mixed-oxide support (1:1 molar ratio) by chlorine addition at different loading levels, their relation to the structural characteristics of supported MoOx species over the support, and their correlation with ethane oxidative dehydrogenation (ODH) activity have been examined. The molybdenum and chlorine precursors are incorporated into the Si/Ti support network as it forms during gelation by using a "one-pot" modified sol-gel/coprecipitation technique. In situ X-ray diffraction during calcination shows the Si/Ti 1:1 mixed-oxide support is in a state of nanodispersed anatase titania over amorphous silica. With the addition of molybdenum and chlorine modifier, this anatase feature becomes more pronounced, indicating a decreased dispersion of titania. The effective titania surface area on the chlorine-doped Si:Ti support obtained from 2-propanol temperature-programmed reaction supports this observation. Raman spectra of dehydrated samples point to an enhanced interaction of MoOx species with silica at the expense of titania. X-ray photoelectron spectroscopic results show that, without forming a molybdenum chloride, the presence of chlorine significantly alters the relative surface concentration of Si vs Ti, the electronic structure of the surface MoOx species, and the oxygen environment around supported MoOx species in the Si/Ti network. Secondary ion mass spectrometry detected the existence of SiCl fragments from the mass spectra, which provides molecular insight into the location of chlorine in Mo/Si:Ti catalysts. The observed increase in ethane ODH selectivity with chlorine modification may be ascribed to the MoOx species sharing more complex ligands with silica and titania with the indirect participation of chlorine. Steady-state isotopic transient kinetic analysis (SSITKA) is used to to examine the oxygen insertion and exchange mechanisms. The catalysts show very little oxygen exchange with the gas phase in the

  1. Processing, Microstructure and Creep Behavior of Mo-Si-B-Based Intermetallic Alloys for Very High Temperature Structural Applications

    SciTech Connect

    Vijay Vasudevan

    2008-03-31

    This research project is concerned with developing a fundamental understanding of the effects of processing and microstructure on the creep behavior of refractory intermetallic alloys based on the Mo-Si-B system. In the first part of this project, the compression creep behavior of a Mo-8.9Si-7.71B (in at.%) alloy, at 1100 and 1200 C was studied, whereas in the second part of the project, the constant strain rate compression behavior at 1200, 1300 and 1400 C of a nominally Mo-20Si-10B (in at.%) alloy, processed such as to yield five different {alpha}-Mo volume fractions ranging from 5 to 46%, was studied. In order to determine the deformation and damage mechanisms and rationalize the creep/high temperature deformation data and parameters, the microstructure of both undeformed and deformed samples was characterized in detail using x-ray diffraction, scanning electron microscopy (SEM) with back scattered electron imaging (BSE) and energy dispersive x-ray spectroscopy (EDS), electron back scattered diffraction (EBSD)/orientation electron microscopy in the SEM and transmission electron microscopy (TEM). The microstructure of both alloys was three-phase, being composed of {alpha}-Mo, Mo{sub 3}Si and T2-Mo{sub 5}SiB{sub 2} phases. The values of stress exponents and activation energies, and their dependence on microstructure were determined. The data suggested the operation of both dislocation as well as diffusional mechanisms, depending on alloy, test temperature, stress level and microstructure. Microstructural observations of post-crept/deformed samples indicated the presence of many voids in the {alpha}-Mo grains and few cracks in the intermetallic particles and along their interfaces with the {alpha}-Mo matrix. TEM observations revealed the presence of recrystallized {alpha}-Mo grains and sub-grain boundaries composed of dislocation arrays within the grains (in Mo-8.9Si-7.71B) or fine sub-grains with a high density of b = 1/2<111> dislocations (in Mo-20Si-10B), which

  2. PROCESSING, MICROSTRUCTURE AND CREEP BEHAVIOR OF Mo-Si-B-BASED INTERMETALLIC ALLOYS FOR VERY HIGH TEMPERATURE STRUCTURAL APPLICATIONS

    SciTech Connect

    Vijay K. Vasudevan

    2005-12-21

    This research project is concerned with developing a fundamental understanding of the effects of processing and microstructure on the creep behavior of refractory intermetallic alloys based on the Mo-Si-B system. During this year, the compressive creep behavior of a Mo-3Si-1B (in wt.%) alloy at 1100 and 1200 C were studied and related to the deformation mechanisms through electron microscopy observations of microstructural changes and deformation structures. The microstructure of this alloy was three-phase, being composed of {alpha}-Mo, Mo{sub 3}Si and T2-Mo{sub 5}SiB{sub 2} phases. Results of compressive creep tests at 1200 and 1100 C showed that the creep rates were quite high at stress levels between 250 and 500 MPa, Two minima in the creep strain rate versus strain data were noted, one at small strain values and the second at much larger strains. A stress exponent of 4.26 was obtained upon plotting the strain rate corresponding to the first minima versus stress, which suggests that dislocation climb and glide dominate the creep process in the early stages. On the other hand, the large strain, minimum creep rate versus stress data gave a stress exponent of {approx}1.18, which indicates diffusional mechanisms and recrystallization dominate the later stages of the creep process. At 1100 C, a stress exponent of 2.26 was obtained, which suggests that both diffusional and dislocation mechanisms contribute to the creep strain. Based on the minimum creep rate data at 1100 C and 1200 C, the activation energy for creep was determined to be 525 kJ/mole, which is somewhat higher than that reported for self diffusion in {alpha}-Mo. Microstructural observations of post-crept samples indicated the presence of many voids in the {alpha}-Mo grains and few cracks in the intermetallic particles and along their interfaces with the {alpha}-Mo matrix. In addition, TEM observations revealed the presence of recrystallized grains and sub-grain boundaries composed of dislocation arrays

  3. Probing the valence orbitals of transition metal-silicon diatomic anions: ZrSi, NbSi, MoSi, PdSi and WSi.

    PubMed

    Gunaratne, K Don Dasitha; Berkdemir, Cuneyt; Harmon, C L; Castleman, A W

    2013-04-28

    Evolution of electronic properties and the nature of bonding of the 4d-transition metal silicides (ZrSi, NbSi, MoSi and PdSi) are discussed, revealing interesting trends in the transition metal-silicon interactions across the period. The electronic properties of select transition metal silicide diatomics have been determined by anion photoelectron imaging spectroscopy and theoretical methods. The electron binding energy spectra and photoelectron angular distributions obtained by 2.33 eV (532 nm) photons have revealed the distinct features of these diatomics. The theoretical calculations were performed at the density functional theory (DFT) level using the unrestricted B3LYP hybrid functional and at the ab initio unrestricted coupled cluster singles and doubles (triplets) (UCCSD(T)) methods to assign the ground electronic states of the neutral and anionic diatomics. The excited electronic states were calculated by the DFT (TD-DFT)/UB3LYP method. We have observed that the valence molecular orbital configuration of the ZrSi and NbSi anions are significantly different from that of the MoSi and PdSi anions. By combining our experimental and theoretical results, we report that the composition of the highest occupied molecular orbitals shift from a majority of transition metal s- and d-orbital contribution in ZrSi and NbSi, to mainly silicon p-orbital contribution for MoSi and PdSi. We expect these observed atomic scale transition metal-silicon interactions to be of increasing importance with the miniaturization of devices approaching the sub-nanometer size regime.

  4. Spectral reflectance data of a high temperature stable solar selective coating based on MoSi2 -Si3N4.

    PubMed

    Hernández-Pinilla, D; Rodríguez-Palomo, A; Álvarez-Fraga, L; Céspedes, E; Prieto, J E; Muñoz-Martín, A; Prieto, C

    2016-06-01

    Data of optical performance, thermal stability and ageing are given for solar selective coatings (SSC) based on a novel MoSi2-Si3N4 absorbing composite. SSC have been prepared as multilayer stacks formed by silver as metallic infrared reflector, a double layer composite and an antireflective layer (doi: 10.1016/j.solmat.2016.04.001 [1]). Spectroscopic reflectance data corresponding to the optical performance of samples after moderate vacuum annealing at temperatures up to 600 °C and after ageing test of more than 200 h with several heating-cooling cycles are shown here.

  5. Spectral reflectance data of a high temperature stable solar selective coating based on MoSi2–Si3N4

    PubMed Central

    Hernández-Pinilla, D.; Rodríguez-Palomo, A.; Álvarez-Fraga, L.; Céspedes, E.; Prieto, J.E.; Muñoz-Martín, A.; Prieto, C.

    2016-01-01

    Data of optical performance, thermal stability and ageing are given for solar selective coatings (SSC) based on a novel MoSi2–Si3N4 absorbing composite. SSC have been prepared as multilayer stacks formed by silver as metallic infrared reflector, a double layer composite and an antireflective layer (doi: 10.1016/j.solmat.2016.04.001 [1]). Spectroscopic reflectance data corresponding to the optical performance of samples after moderate vacuum annealing at temperatures up to 600 °C and after ageing test of more than 200 h with several heating–cooling cycles are shown here. PMID:27182544

  6. Development and realization of non-periodic W/Si multilayer mirrors for 5 14 keV X-ray plasma diagnostic

    NASA Astrophysics Data System (ADS)

    Champeaux, J.-Ph.; Troussel, Ph.; Villier, B.; Vidal, V.; Khachroum, T.; Vidal, B.; Krumrey, M.

    2007-11-01

    W/Si aperiodic multilayer mirrors were developed at the Commissariat à l'Energie Atomique (CEA-DIF) in collaboration with the Laboratoire des Matériaux et de Microélectronique de Provence (L2MP). These "super-mirrors" [F. Mezei, Commun. Phys. 2 (1977) 41. [1]; E. Spiller, Appl. Phys. Lett. 20 (1972) 365. [2

  7. Effects of thermal annealing of W/SiO2 multilayer Bragg reflectors on resonance characteristics of film bulk acoustic resonator devices with cobalt electrodes

    NASA Astrophysics Data System (ADS)

    Yim, Munhyuk; Kim, Dong-Hyun; Chai, Dongkyu; Yoon, Giwan

    2004-05-01

    In this article, we present the thermal annealing effects of the W/SiO2 multilayer reflectors in ZnO-based film bulk acoustic resonator (FBAR) devices with cobalt (Co) electrodes in comparison with those with aluminum (Al) electrodes. Various thermal annealing conditions have been implemented on the W/SiO2 multilayer reflectors formed on p-type (100) silicon substrates. The resonance characteristics could be significantly improved due to the thermal annealing and were observed to depend strongly on the annealing conditions applied to the reflectors. Particularly, the FBAR devices with the W/SiO2 multilayer reflectors annealed at 400 °C/30 min have shown superior resonance characteristics in terms of return loss and quality factor. In addition, the use of Co electrodes has resulted in the further improvement of the resonance characteristics as compared with the Al electrodes. As a result, the combined use of both the thermal annealing and Co electrodes seems very useful to more effectively improve the resonance characteristics of the FBAR devices with the W/SiO2 multilayer reflectors. .

  8. Improvement of the Adhesion Strength of MoSi2-ZrB2 Coating by Optimizing Particle Spraying and Subsequent Heat Treatment

    NASA Astrophysics Data System (ADS)

    Lu, Wang; Qian-gang, Fu; Ning-kun, Liu; Jia, Sun

    2016-10-01

    A MoSi2-ZrB2 coating was prepared on SiC-coated C/C composites by supersonic plasma spraying, and the effects of particle diameter and subsequent heat treatment in argon at different temperatures on the adhesion strength were studied. The results show that the MoSi2-ZrB2 coating sprayed with an average powder diameter of 29.2 μm could melt thoroughly and form a dense structure without micro-pore, which results in a relatively good adhesion strength of 11.4 MPa compared with 9.2 and 8.6 MPa of the coatings sprayed with the powder diameter of 58.2 and 35.5 μm. The coating presents a decreasing porosity from 2.2 to 1.5% and an increasing adhesion strength from 11.6 to 16.9 MPa after heat treatment at 800 °C, which is mainly caused by slight sintering of SiO2 and B2O3

  9. Fabrication and mechanical properties of continuously graded MoSi{sub 2}-ZrO{sub 2}(2Y) materials using wet-molding

    SciTech Connect

    Arata, Kenji; Takeuchi, Nobutaka; Yoshinaka, Masaru; Hirota, Ken; Yamaguchi, O.

    1997-08-01

    Continuously graded MoSi{sub 2}-ZrO{sub 2}(2Y) materials with high density (97.5% of theoretical) have been fabricated by uniaxial wet-molding, followed by hot pressing (1,000 C/1 h/30 MPa) and hot isostatic pressing (1,400 C/2 h/196 MPa). Their composition profiles are greatly influenced by the viscosity of mixed solutions of glycerin and ethanol used as a dispersion medium; a linear compositional gradient from MoSi{sub 2}/ZrO{sub 2}(2Y) = 70/30 to {approximately}20/80 mol% is obtained from the solution (50/50 vol%) with a viscosity of {approximately}20 mPa{center_dot}s. Vickers hardness (H{sub v}) and fracture toughness (K{sub IC}) increase from 9.7 to 12.4 GPa and from 5.1 to 12.5 MPa{center_dot}m{sup 1/2}, respectively, with increasing ZrO{sub 2}(2Y) composition.

  10. Time dependent changes in Schottky barrier mapping of the W/Si(001) interface utilizing ballistic electron emission microscopy

    SciTech Connect

    Durcan, Chris A.; Balsano, Robert; LaBella, Vincent P.

    2015-06-28

    The W/Si(001) Schottky barrier height is mapped to nanoscale dimensions using ballistic electron emission microscopy (BEEM) over a period of 21 days to observe changes in the interface electrostatics. Initially, the average spectrum is fit to a Schottky barrier height of 0.71 eV, and the map is uniform with 98% of the spectra able to be fit. After 21 days, the average spectrum is fit to a Schottky barrier height of 0.62 eV, and the spatial map changes dramatically with only 27% of the spectra able to be fit. Transmission electron microscopy shows the formation of an ultra-thin tungsten silicide at the interface, which increases in thickness over the 21 days. This increase is attributed to an increase in electron scattering and the changes are observed in the BEEM measurements. Interestingly, little to no change is observed in the I-V measurements throughout the 21 day period.

  11. Reaction-bonding preparation of Si{sub 3}N{sub 4}/MoSi{sub 2} and Si{sub 3}N{sub 4}/WSi{sub 2} composites from elemental powders

    SciTech Connect

    Zhang, B.R.; Marino, F.

    1997-01-01

    Si{sub 3}N{sub 4}/MoSi{sub 2} and Si{sub 3}N{sub 4}/WSi{sub 2} composites were prepared by reaction-bonding processes using as starting materials powder mixtures of Si-Mo and Si-W, respectively. A presintering step in an Ar-base atmosphere was used before nitriding for the formation of MoSi{sub 2} and WSi{sub 2}; the nitridation in a N{sub 2}-base atmosphere was followed after presintering with the total stepwise cycle of 1,350 C {times} 20 h + 1,400 C {times} 20 h + 1,450 C {times} 2 h. The final phases obtained in the two different composites were Si{sub 3}N{sub 4} and MoSi{sub 2} or WSi{sub 2}; no free elemental Si and Mo or W were detected by X-ray diffraction.

  12. Experimental investigation of the dynamic elastic modulus and vibration damping in MoSi{sub 2}-30%Si{sub 3}N{sub 4} as a function of temperature

    SciTech Connect

    Olsen, G.T.; Wolfenden, A.; Hebsur, M.G.

    2000-02-01

    The dynamic elastic modulus, E, and vibration damping of molybdenum disilicide (MoSi{sub 2}) with 30% volume addition of silicon nitride (Si{sub 3}N{sub 4}) were measured at varying temperatures using the piezoelectric ultrasonic composite oscillator technique (PUCOT). The value of the elastic modulus of the composite was observed to decrease as temperature, T, was increased. The value of dE/dT of MoSi{sub 2} was determined to be {minus}0.03 GPa/K. The vibration damping of MoSi{sub 2}-30%Si{sub 3}N{sub 4} increased as temperature was increased, with an effective activation energy of 0.076 eV/atom. This was an average over the entire temperature range, but two distinct slopes were observed in the plot of damping versus inverse temperature.

  13. Bragg amplification of the Si {kappa}{alpha} line emitted from a Mo/Si multilayer irradiated by an electron beam

    SciTech Connect

    Jonnard, P.; Bonnelle, C.; Pardo, B.; Andre, J.-M.; Bridou, F

    2003-01-24

    We report on the intensity modulation of the Si {kappa}{alpha} line emitted from a Mo/Si multilayer as a function of the exit angle of the photons. The observation takes place around the direction corresponding to the Bragg diffraction of Si {kappa}{alpha} by the multilayer. The sample is irradiated by an electron beam whose the energy is varied between 2 and 6 keV. An important intensity variation is observed within the angular range corresponding to the diffraction pattern of the emitting structure. A 15 % enhancement of the emitted radiation is measured in the Bragg direction of the multilayer, whatever the incident electron energy. This amplification is interpreted on the basis of the reciprocity theorem. A possible application as x-ray resonator is suggested.

  14. Microstructure and property modifications of an AISI H13 (4Cr5MoSiV) steel induced by pulsed electron beam treatment

    SciTech Connect

    Zhang Kemin; Zou Jianxin; Grosdidier, Thierry; Dong Chuang

    2010-11-15

    In the present work, surface modifications generated by the low energy high current pulsed electron beam (LEHCPEB) treatments have been investigated on an AISI H13 (4Cr5MoSiV) steel. From the observations of scanning electron microscopy, x-ray diffraction, and electron back scattering diffraction determinations, it could be established that the final structure in the melted layer is a mixture of ultrafine {delta} phase, martensite, and residual austenite. The formation of the heterogeneous microstructures on the surface layer is related to the very rapid heating, melting, solidification, and cooling induced by the LEHCPEB irradiation. After the LEHCPEB treatment, the wear resistance of the steel effectively improved. This can be mainly attributed to the higher hardness of the ultrafine structures formed on the top surface and the hardened subsurface layers after the treatment.

  15. Evaluation of lubricating oil preparation procedures for the determination of Al, Ba, Mo, Si and V by high-resolution continuum source FAAS.

    PubMed

    Amorim Filho, Volnei Resta; Gomes Neto, José Anchieta

    2009-01-01

    Microwave-assisted acid decomposition and oil-in-water emulsification were evaluated as sample pretreatment procedures to determine Al, Ba, Mo, Si and V in lubricating oils by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS). Average recoveries of Al, Ba and V in oil digests (107, 103 and 101%) were close to those obtained for emulsions prepared in kerosene medium (94, 113 and 95%). Average recoveries for Mo were close to 105 and 46% for emulsions and digests, respectively. Improved average recoveries (101%) were obtained for Mo in digests using the analyte addition technique. Silicon was successfully quantified only in digested samples. Limits of quantification for Al, Ba, Mo and V were 1.4, 31.5, 1.5 and 11.4-fold lower than those obtained by line-source FAAS. Enhanced sensitivity, multi-elemental capability, and high sample throughput are among the main advantages of HR-CS FAAS in comparison with the line-source FAAS technique.

  16. The effect of post-treatment of a high-velocity oxy-fuel Ni-Cr-Mo-Si-B coating part 2: Erosion-corrosion behavior

    NASA Astrophysics Data System (ADS)

    Shrestha, S.; Hodgkiess, T.; Neville, A.

    2001-12-01

    In this paper, a study of the erosion-corrosion characteristics of a Ni-Cr-Mo-Si-B coating applied by the high-velocity oxy-fuel (HVOF) process on to an austenitic stainless steel (UNS S31603) substrate are reported. The coatings were studied in the as-sprayed condition, after vacuum sealing with polymer impregnation and after vacuum furnace fusion. The erosion-corrosion characteristics were assessed in an impinging liquid jet of 3.5% NaCl solution at 18 °C at a velocity of 17 m/s at normal incidence in two conditions: (1) free from added solids and (2) containing 800 ppm silica sand. The methodology employed electrochemical control and monitoring to facilitate the identification of the separate and interrelated erosion and corrosion contributions to the erosion-corrosion process. The rates of erosion-corrosion damage were drastically accelerated in the presence of the suspended solids. The application of cathodic protection significantly reduced the deterioration process. The study showed the effect of sealing with polymer impregnation did not significantly alter the erosion-corrosion behavior of the sprayed coating. However, there was a significant improvement in erosion-corrosion durability afforded by the postfusion process. The mechanisms by which the improved performance of vacuum-fused coatings is achieved are discussed.

  17. Hot pressing effect on the shear bond strength of dental porcelain to CoCrMoSi alloy substrates with different surface treatments.

    PubMed

    Henriques, B; Faria, S; Soares, D; Silva, F S

    2013-01-01

    The purpose of this study was to evaluate the effect of hot pressing on the shear bond strength of a CoCrMoSi alloy to a low-fusing feldspathic porcelain, for two types of surface treatments: polished and grit-blasted. Moreover, the shear strength of hot pressed porcelain was also compared with that of conventional vacuum sintered porcelain. Bond strength of metal-porcelain composites were assessed by the means of a shear test performed in a universal test machine until fracture. Fracture surfaces and interfaces were investigated by optical microscope, stereomicroscope and SEM/EDS. Data was analyzed with Shapiro-Wilk test to test the assumption of normality. The 2-way ANOVA followed by Tukey HSD multiple comparison test was used to compare shear bond strength results and the t-test was used to compare the porcelain shear strength (p<0.05). Hot pressed specimens exhibited significantly (p<0.001) higher bond strength values than those obtained by conventional PFM technique. Significant differences (p<0.001) were found in the shear bond strength between grit-blasted and polished specimens. Significant differences (p<0.05) were also found between the shear strength of vacuum sintered and hot pressed porcelain. This study revealed that metal-ceramic bond strength is maximized for hot pressed porcelain onto rough metal substrates, with lower variability in results. Hot pressing technique was also shown to enhance the cohesion of porcelain.

  18. Deposition and cyclic oxidation behavior of a protective (Mo,W)(Si,Ge) [sub 2] coating on Nb-base alloys

    SciTech Connect

    Mueller, A.; Wang, G. . Dept. of Materials Science and Engineering); Rapp, R.A. )

    1992-05-01

    A multicomponent diffusion coating has been developed to protect Nb-base alloys from high-temperature environmental attach. A solid solution of molybdenum and tungsten disilicide (Mo, W)Si[sub 2], constituted the primary coating layer which supported a slow-growing protective silica scale in service. Germanium additions were made during the coating process to improve the cyclic oxidation resistance by increasing the thermal expansion coefficient of the vitreous silica film formed and to avoid pesting by decreasing the viscosity of the protective film. In this paper, the development of the halide-activated pack cementation coating process to produce this (Mo,W)(Si,Ge)[sub 2] coating on Nb-base alloys is described. The results of cyclic oxidation for coupons coated under different conditions in air at 1370[degrees]C are presented. Many coupons have successfully passed 200 1 h cyclic oxidation tests at 1370[degrees]C with weight-gain values in the range of 1.2 to 1.6 mg/cm[sup 2].

  19. EPR and diffuse reflectance studies of the physico-chemical phenomena occurring during the preparation of Mo/SiO[sub 2] catalysts by the grafting method

    SciTech Connect

    Louis, C.; Che, M. )

    1992-05-01

    Mo/SiO[sub 2] catalysts were prepared by the grafting method, i.e., by air- and water-free reaction between MoCl[sub 5] and hydroxyl groups of silica support. This reaction may be performed either in a liquid medium (cyclohexane) or in the vapor phase. It is shown by EPR and diffuse reflectance spectroscopies that two types of molybdenum were deposited onto silica during the grafting reaction: (i) grafted Mo as [triple bond]SiOMoCl[sub 4] (g = 1.9652 and g = 1.968), and (ii) physically adsorbed Mo as the diamagnetic Mo[sub 2] Cl[sub 10] dimer; this compound turns blue in air because of both its partial oxidation and hydrolysis to form the so-called molybdenum blues. After the grafting reaction itself, the second step involves washing by water or ammonia solution. The physically adsorbed Mo is eliminated and the grafted Mo remaining on the silica is hydrolyzed and partially oxidized in air, so as to lead to the following species: [triple bond]SiOmO[sup v](OH)[sub 4] or [triple bond]SiOMo[sup vi](OH)[sub 5]. In consequence, at the very end of the preparation, only the grafted Mo species remains on the silica and the sample color is brown. The catalytic behavior of the unwashed and washed catalysts in the reaction of methanol oxidation emphasizes the differences in the Mo species. The unwashed sample containing molybdenum blues behaves like a polycrystalline MoO[sub 3] catalyst, producing mainly methylal at low reaction temperature (230 C) and formaldehyde at higher temperature (280 C), whereas the washed one, containing only grafted Mo, produces mainly methylformate and, to a lower extent, formaldehyde.

  20. Evaluation of backside particle contamination and electrostatic chuck design on the cleanliness of EUV reticle mask blanks in a multilayer Mo/Si ion beam deposition system

    NASA Astrophysics Data System (ADS)

    Hayes, A. V.; Randive, R.; Reiss, I.; Menendez, J.; Kearney, P.; Sugiyama, T.

    2008-10-01

    A key requirement for the success of EUV lithography is a high volume supply of defect-free Mo/Si multilayer (ML)- coated mask blanks. The process of fabricating mask blanks is particularly sensitive to particle contamination because decoration by the deposition of the reflective stack on sub-lithographic (< 22 nm) particles can create larger, printable defects. One possible source of added defects is the mask substrate fixturing method, which, in the Veeco ion beam deposition (IBD) system used to deposit our ML coatings, must allow tilt and rotation of a vertically oriented substrate. As commonly practiced, an electrostatic chuck (ESC) is used instead of a mechanical clamping fixture to avoid transferring particles to the front surface of the mask by mechanical clamping and declamping operations. However, a large number of particles can be introduced to the backside of the mask by electrostatic clamping. Up to now, there has been little concern about such backside particles, except for relatively large particles (> 1 micron) that may affect out-of-plane distortion of the mask in an EUV lithography tool. As the cleanliness of the EUV masks and mask blank fabrication approaches perfection, however, there is more concern that particles transferred from the backside to the frontside of the mask may be a significant issue. Such transfer may occur in the deposition chamber, in the substrate cassette, or in the transfer module and may be indirect. In this paper, we present data from characterizing the amount, size, shape, composition, and location of the backside particle defects generated by electrostatic clamping, using a particle counter and scanning electron microscope (SEM), and compare results for a pin-type e-chuck, which has a small contact area, with the standard flat e-chuck. The key result is a 10X to 30X reduction in the total number of backside particles for the pin chuck. Also, preliminary data indicates that the pin chuck stays cleaner under service

  1. A point-focusing small angle x-ray scattering camera using a doubly curved monochromator of a W/Si multilayer

    NASA Astrophysics Data System (ADS)

    Sasanuma, Yuji; Law, Robert V.; Kobayashi, Yuji

    1996-03-01

    A point-focusing small angle x-ray scattering (SAXS) camera using a doubly curved monochromator of a W/Si multilayer has been designed, constructed, and tested. The two radii of curvature of the monochromator are 20 400 and 7.6 mm. The reflectivity of its first-order Bragg reflection for CuKα radiation was calculated to be 0.82, being comparable to that (0.81) of its total reflection. By only 10 s x-ray exposure, scattering from a high-density polyethylene film was detected on an imaging plate (IP). A rotating-anode x-ray generator operated at 40 kV and 30 mA was used. Diffraction from rat-tail collagen has shown that the optical arrangement gives the Bragg spacing up to, at least, 30 nm for CuKα radiation. Combined with IPs, the camera may permit us to carry out time-resolved SAXS measurements for phase behaviors of liquid crystals, lipids, polymer alloys, etc., on conventional x-ray generators available in laboratories.

  2. Fatigue Response of Mo-Si-B Alloys

    DTIC Science & Technology

    2005-09-01

    4 S-1 _00- 0- 6 S-1l -0 s-- 6 se -. •.10-7 S-1 0 0o jA -0 2 4 6 8 10 12 2 4 6 8 10 1𔃼 Strain...CoooIýD 6 0 n 3 . 40 U) 0 . ..10 . . - . . ’ . . .. • . . n ’ 0 5 10 15 10-8 10-7 10- 6 10" 10- 4 10-3 10-2 Strain (% Strain Rate (s-1) Figure 8...ae eim 04s1 o107 s-1 In n) th5aitoni.h2omrsieflwsrs 100 CAi100 V c33 n 2.5 50 5 0 1 2 3 4 5 6 7108 10-7 10- 6 10-5 104 10-3 Strain ()Strain Rate

  3. The high-temperature oxidation behavior of MoSi(2) and MoSi(2)-based composites

    NASA Astrophysics Data System (ADS)

    Beatrice, Pamela

    Single-crystal MoSisb2 and four polycrystalline MoSisb2 materials prepared by three different preparation techniques (hot pressing, arc melting, and vacuum plasma spraying) were isothermally oxidized for 100 hours at 1500sp°C in 1 atm. oxygen. After an initial period which varied among the samples, these materials exhibited parabolic oxidation behavior and their parabolic rate constants ranged from 0.4 × 10sp{-9} to 2.0 × 10sp{-9} gsp2cmsp{-4}hrsp{-1}, indicating that preparation method does not have a significant effect on the oxidation behavior. Short-time oxidation runs showed that the higher initial oxidation rate in two of the materials did not correspond to variations in the crystallization rate of the scale from amorphous silica to cristobalite, but instead correlated to higher impurity levels of Al and Fe which diffused into the scale within 0.25 hr. A Mosb5Sisb3 interlayer between the oxide and the MoSisb2 was observed in the single crystal but not in the polycrystalline materials, indicating the importance of grain boundary diffusion in delaying the formation of the Mosb5Sisb3 interlayer. Four MoSisb2-based composites containing 40 vol.% SiC, 5 vol.% SiC. 10 vol.%SiC-10vol.% partially stabilized zirconia, and 20 vol.% ZrOsb2, respectively, were also oxidized at 1500sp°C in 1 atmosphere oxygen. With all four composites, the Al and Fe impurities rapidly diffused into the oxide scale, which after 100 hours had regions of high impurity content near the gas-oxide interface and regions of high purity silica near the oxide-composite interface. The 40% SiC and 5% SiC containing composites had isothermal oxidation growth rates of 4.4 × 10sp{-9} and 2.9 × 10sp{-9} gsp2cmsp{-4}hrsp{-1}, respectively. The 10vol.%SiC-10vol.% partially stabilized zirconia composite exhibited parabolic oxidation behavior over 100 hours but showed complicated scale reactions with the dissolution of yttria from the zirconia to form a yttrium silicate within 0.25 hr. and zircon formation within 2 hours. The 20% ZrOsb2 material showed logarithmic oxidation behavior, a loss of integrity of the initial composite structure, and the formation of internal porosity.

  4. Microstructural analysis of W-SiCf/SiC composite

    NASA Astrophysics Data System (ADS)

    Yoon, Hanki; Oh, Jeongseok; Kim, Gonho; Kim, Hyunsu; Takahashi, Heishichiro; Kohyama, Akira

    2015-03-01

    Continuous silicon carbide fiber-reinforced silicon carbide (SiCf/SiC) composites are promising structure candidates for future fusion power systems such as gas coolant fast channels, extreme high temperature reactor and fusion reactors, because of their intrinsic properties such as excellent mechanical properties, high thermal conductivity, good thermal-shock resistance as well as excellent physical and chemical stability in various environments under elevated temperature conditions. In this study, bonding of tungsten and SiCf/SiC was produced by hot-press method. Microstructure analyses were performed using SEM and TEM.

  5. Pinning of superconducting vortices in MoGe/Au Thin nano-squares

    NASA Astrophysics Data System (ADS)

    Serrier-Garcia, Lise; Timmermans, Matias; Van de Vondel, Joris; Moshchalkov, Victor V.

    2017-02-01

    In this work, we report a scanning tunneling spectroscopy study of vortex patterns in mesoscopic superconducting squares and explore the impact of defects and corrugations inherently present in nanofabricated structures. We find that a hillock at the edge can function as an attractive or repulsive pinning center for vortices deforming the, theoretically predicted, symmetry-induced vortex configurations. In addition, we exploit the inherently present imperfections, creating metastable states, to visualize the dynamics of vortex penetration during magnetic field sweeps.

  6. Mo-Si-B Alloys and Diboride Systems for High Enthalpy Environments: Design and Evaluation

    DTIC Science & Technology

    2016-01-15

    candidate material species production over a range of test gas enthalpies and pressures for UWM and ISU samples. Year 3: 3.1 Begin FTIR...C and the reaction is enhanced at lower temperature in a combustion environment with water vapor and/or lower oxygen partial pressure in the...used as the plasma gas and helium was used as auxiliary gas (gas pressure 10.3 bar (150 psi) and 3.4 bar (50 psi) respectively). A ZrO2 coated

  7. Pest resistant MoSi.sub.2 materials and method of making

    NASA Technical Reports Server (NTRS)

    Hebsur, Mohan G. (Inventor)

    1995-01-01

    A pest resistant molybdenum disilicide composition is provided for use in high temperature structural applications. The composition includes molybdenum disilicide and silicon nitride and can be used to prepare improved reinforced composites.

  8. Modification of Mo-Si alloy microstructure by small additions of Zr.

    PubMed

    Mousa, M; Wanderka, N; Timpel, M; Singh, S; Krüger, M; Heilmaier, M; Banhart, J

    2011-05-01

    Molybdenum and its alloys are potential materials for high-temperature applications. However, molybdenum is susceptible to embrittlement because of oxygen segregation at the grain boundaries. In order to alleviate the embrittlement small amounts of zirconium were alloyed to a solid solution of Mo-1.5Si alloy. Two Mo-based alloys, namely Mo-1.5Si and Mo-1.5Si-1Zr, were investigated by the complementary high-resolution methods transmission electron microscopy and atom probe tomography. The Mo-1.5Si alloy shows a polycrystalline structure with two silicon-rich intermetallic phases Mo(5)Si(3) and Mo(3)Si located at the grain boundaries and within the grains. In addition, small clusters with up to 10 at% Si were found within the molybdenum solid solution. Addition of a small amount of zirconium to Mo-1.5Si leads to the formation of two intermetallic phases Mo(2)Zr and MoZr(2), which are located at the grain boundaries as well as within the interior of the grain. Transmission electron microscopy shows that small spherical Mo-Zr-rich precipitates (<10nm) decorate the grain boundaries. The stoichiometry of the small precipitates was identified as Mo(2)Zr by atom probe tomography. No Si-enriched small precipitates were detected in the Mo-1.5Si-1Zr alloy. It is concluded that the presence of zirconium hinders their formation.

  9. 193-nm radiation durability study of MoSi binary mask and resulting lithographic performance

    NASA Astrophysics Data System (ADS)

    Servin, Isabelle; Belledent, Jérôme; Pain, Laurent; Connolly, Brid; Sczyrba, Martin; Lamantia, Matt

    2011-05-01

    Dimensions on mask continue to shrink to keep up with the ITRS roadmap. This has implications on the material of choice for the blanks. For example, the new binary OMOG stack (Opaque MOSi on Glass) was successfully introduced to meet the mask specifications at the 32nm technology node. Obviously 193-nm optical lithography will be further used in production at even higher NA and lower k1 emphasizing, for example, the impact on wafer of any electromagnetic field migration effects. Indeed, long term radiation damage inducing CD growth and consequently, device yield loss, has already been reported [1, 2]. This mechanism, known as Electric Field induced Migration of chrome (EMF) often shortens the mask's lifetime. Here, a study was conducted to investigate the impact of intensive ArF scanner exposure both on final wafer and mask performances. The Si printed wafers measured with top-down CD-SEM were characterized with respect to CD uniformity, linearity, Sub Resolution Assist Feature (SRAF) printability through process window, MEEF, DOF, and OPC accuracy. The data was also correlated to advanced mask inspection results (e.g. AIMSTM) taken at the same location. More precisely, this work follows a preliminary study [1] which pointed out that OMOG is less sensitive to radiation than standard COG (Chrome On Glass). And, in this paper, we report on results obtained at higher energy to determine the ultimate lifetime of OMOG masks.

  10. Ductilization of Mo-Si solid solutions manufactured by powder metallurgy

    SciTech Connect

    Saage, H.; Krueger, M.; Sturm, D.; Heilmaier, M.; Schneibel, J H; George, Easo P; Heatherly Jr, Lee; Somsen, Ch.; Eggeler, G.; Yang, Ying

    2009-01-01

    Mo-1.5 at.% Si alloys with additions of either Y{sub 2}O{sub 3} or Zr were manufactured by mechanical alloying. The Y{sub 2}O{sub 3} particles reduced the grain size and increased the room temperature strength, but did not alleviate the brittleness of previously investigated Mo-1.5 at.% Si without Y{sub 2}O{sub 3}. Additions of Zr, on the other hand, resulted not only in a fine grain size and an extremely high bend strength ({approx}2 GPa), but also in limited bend ductility at room temperature. Zr additions are seen to be beneficial for three reasons. First, Zr reduces the grain size. Second, Zr getters detrimental oxygen by forming ZrO{sub 2} particles (which in turn help to pin the grain boundaries). Third, in situ Auger analysis shows that Zr reduces the concentration of Si segregated at the grain boundaries. This is thought to enhance the grain boundary cohesive strength and thus leads to the observed ductility.

  11. Spatial angles sensitivity of Fe83Ga17/AlN/Mo/Si magnetoelectric device

    NASA Astrophysics Data System (ADS)

    Shi, Jiaxing; Yin, Liping; Lu, Cifu; Zhu, Jie

    2017-05-01

    Magnetoelectric (ME) devices based on Fe-Ga/AlN/Mo thin films deposited on Si(100) substrates were prepared by magnetron sputtering. The cantilever device possessed a high magnetoelectric coefficient of 167.7 V/cm.Oe at its resonance frequency and exhibited anisotropic properties. More importantly, the magnetoelectric coefficient changed with the out-of-plane space angle, from 15 to 167.7 V/cm.Oe. After annealing under a 500-Oe magnetic field, the magnetic domains of the thin film partly remained in the field direction. Moreover, the anisotropic properties of the ME device significantly improved; the ME coefficient increased by 30% to 218 V/cm.Oe and became more sensitive to the in-plane angle. Thus, the ME device proposed in this work can be used to detect changes in spatial angles.

  12. Crystallization of ultrathin W-Si multilayer structures by high-energy heavy ion irradiations

    SciTech Connect

    Marfaing, J.; Marine, W. ); Vidal, B. ); Toulemonde, M. ); Hage Ali, M.; Stoquert, J.P. )

    1990-10-22

    Ultrathin amorphous multilayers structures (1.55 nm bilayer period) were irradiated by high-energy heavy ion ({sup 127}I and {sup 238}U ions). Transmission electron microscopy study shows that the ion-material interaction in such a configuration leads to an irreversible transformation of the initial amorphous structures. In this letter, we report the first observation of the crystallization of the multilayers induced by the heavy ion irradiations with a subsequent formation of a new WSi structure. The crucial role of the electronic effects in the crystallization process is discussed relatively to the other phenomena induced under the ion irradiation.

  13. MoSI (Monitoreo de Sobrevivencia Invernal): assessing habitat-specific overwintering survival of neotropical migratory landbirds

    Treesearch

    David F. DeSante; T. Scott Sillett; Rodney B. Siegel; James F. Saracco; Claudia A. Romo de Vivar Alvarez; Salvadora Morales; Alexis Cerezo; Danielle R. Kaschube; Manuel Grosselet; Borja Mila

    2005-01-01

    Recent evidence suggests that population declines in many Neotropical-wintering migratory landbird species are caused by habitat loss and degradation on their wintering grounds. Such habitat loss and degradation can lower overwintering survival rates and cause surviving birds to leave their wintering grounds in poor physical condition, leading to high mortality during...

  14. Bimetallic catalysts. V. Kinetics of the hydrogenolysis of butane over Pt-Mo/SiO[sub 2] catalysts

    SciTech Connect

    Leclercq, G.; Gharbi, A.El.; Pietrzyk, S. )

    1993-11-01

    The kinetics of the hydrogenolysis of butane on various Pt-Mo catalysts deposited on silica with the same metal content but with various Mo/(Mo + Pt) ratios has been studied. The hydrogenolysis of the two different kinds of C-C bonds has been distinguished. It is shown that the addition of Mo to Pt drastically changes the selectivity of the reaction, but that this selectivity is approximately the same for all the bimetallic Pt-Mo catalysts. Using a rate equation that had already been used for the hydrogenolysis of alkanes (Maurel, R., Leclercq, G., and Leclercq, L., J. Catal. 44, 68 (1975)), calculation has been made of the values of the equilibrium adsorption constants ([lambda]) and those of the rate constants of the C-C bond splitting steps (k) for the hydrogenolysis of the terminal C-C bonds ([lambda][sub 1] and k[sub 1]) and of the middle C-C bond ([lambda][sub 2] and k[sub 2]). In this way it has been shown that only Pt alone, two different intermediaries with high [lambda] values are formed in which the C-C bonds will be broken further with different selectivities but with low rate constants. On the contrary, on all Pt-Mo catalysts, butane is adsorbed as a single intermediate adsorbed species with a much lower adsorption equilibrium constant than on Pt alone, but this adsorbed species is much more reactive (k[sub 1] and k[sub 2]). The adsorption equilibrium constants are the same for all Pt-Mo taking into account the margin of error, which shows that, on all Pt-Mo, butane is adsorbed on the same mixed Pt-Mo site of constant composition whatever the catalyst's composition. The number of these active sites (proportional to k[sub 1] and k[sub 2]) increases as Mo/(Mo + Pt) increases up to 25-30%, then it decreases. 38 refs., 3 figs., 5 tabs.

  15. Study of the durability of the Ru-capped MoSi multilayer surface under megasonic cleaning

    NASA Astrophysics Data System (ADS)

    Kurtuldu, Hüseyin; Rastegar, Abbas; House, Matthew

    2012-11-01

    Because EUV masks lack of a pellicle, they are prone to particle contamination and must be cleaned frequently. Despite the relatively good resistance of the TaN absorber lines to pattern damage by megasonic cleaning, the Ru cap can be easily damaged by it. We demonstrate that the type and concentration of the dissolved gas are critical factors in determining the cavitation that eventually introduces pits on the surface of Ru-capped multilayer films. In particular, oxygen creates many more pits than CO2 under similar conditions. In this paper, we present the results of SEMATECH's extensive experimental studies of pit creation on Ru-capped multilayer EUV blanks by megasonics as a function of acoustic field power, gas type and concentration in ultra-pure water, and chemicals during sonication.

  16. Investigation of Shock-Induced Chemical Reactions in Mo-Si Powder Mixtures Using Instrumented Experiments with PVDF Stress Gauges

    SciTech Connect

    Vandersall, K S; Thadhani, N N

    2001-05-29

    Shock-induced chemical reactions in {approx}58% dense Mo+2Si powder mixtures were investigated using time-resolved instrumented experiments, employing PVDF-piezoelectric stress gauges placed at the front and rear surfaces of the powders to measure the input and propagated stresses, and wave speed through the powder mixture. Experiments performed on the powders at input stresses less than 4 GPa, showed characteristics of powder densification and dispersed propagated wave stress profiles with rise time > {approx}40 nanoseconds. At input stress between 4-6 GPa, the powder mixtures showed a sharp rise time (<{approx}10 ns) of propagated wave profile and an expanded state of products revealing evidence of shock-induced chemical reaction. At input stresses greater than 6 GPa, the powder mixtures showed a slower propagated-stress-wave rise time and transition to a low-compressibility (melt) state indicating lack of shock-induced reaction. The results illustrate that premature melting of Si, at input stresses less than the crush-strength of the powder mixtures, restricts mixing between reactants and inhibits ''shock-induced'' reaction initiation.

  17. Ambient- to elevated-temperature fracture and fatigue properties of Mo-Si-B alloys: Role of microstructure

    NASA Astrophysics Data System (ADS)

    Kruzic, J. J.; Schneibel, J. H.; Ritchie, R. O.

    2005-09-01

    Ambient- to elevated-temperature fracture and fatigue-crack growth results are presented for five Mo-Mo3Si-Mo5SiB2-containing α-Mo matrix (17 to 49 vol pct) alloys, which are compared to results for intermetallic-matrix alloys with similar compositions. By increasing the α-Mo volume fraction, ductility, or microstructural coarseness, or by using a continuous α-Mo matrix, it was found that improved fracture and fatigue properties are achieved by promoting the active toughening mechanisms, specifically crack trapping and crack bridging by the α-Mo phase. Crack-initiation fracture toughness values increased from 5 to 12 MPa√m with increasing α-Mo content from 17 to 49 vol pct, and fracture toughness values rose with crack extension, ranging from 8.5 to 21 MPa√m at ambient temperatures. Fatigue thresholds benefited similarly from more α-Mo phase, and the fracture and fatigue resistance was improved for all alloys tested at 1300 °C, the latter effects being attributed to improved ductility of the α-Mo phase at elevated temperatures.

  18. Effects of sputtering power Schottky metal layers on rectifying performance of Mo-SiC Schottky contacts

    NASA Astrophysics Data System (ADS)

    Lee, Seula; Lee, Jinseon; You, Sslimsearom; Kyoung, Sinsu; Kim, Kyung Hwan

    2016-01-01

    In this study, Schottky barrier diodes based on silicon carbide with various levels of Schottky metal layer input power were prepared and characterized. In this structure, molybdenum and aluminum were employed as the Schottky metal and top electrode, respectively. Schottky metal layers were deposited with input power ranging from 30 to 210 W. Schottky metal layers and top electrodes were deposited with a thickness of 3000 Å. The Schottky barrier heights, series resistances, and ideality factor were calculated from current-voltage (I-V) curves obtained using the Cheung-Cheung and Norde methods. All deposition processes were conducted using a facing targets sputtering system. Turn on voltage was minimized when the input power was 90 W, at which point electrical characteristics were observed to have properties superior to those at other levels of input power.

  19. Study on the lifetime of Mo/Si multilayer optics with pulsed EUV-source at the ETS

    NASA Astrophysics Data System (ADS)

    Schürmann, Mark; Yulin, Sergiy; Nesterenko, Viatcheslav; Feigl, Torsten; Kaiser, Norbert; Tkachenko, Boris; Schürmann, Max C.

    2011-06-01

    As EUV lithography is on its way into production stage, studies of optics contamination and cleaning under realistic conditions become more and more important. Due to this fact an Exposure Test Stand (ETS) has been constructed at XTREME technologies GmbH in collaboration with Fraunhofer IOF and with financial support of Intel Corporation. This test stand is equipped with a pulsed DPP source and allows for the simultaneous exposure of several samples. In the standard set-up four samples with an exposed area larger than 35 mm2 per sample can be exposed at a homogeneous intensity of 0.25 mW/mm2. A recent update of the ETS allows for simultaneous exposures of two samples with intensities up to 1.0 mW/mm2. The first application of this alternative set-up was a comparative study of carbon contamination rates induced by EUV radiation from the pulsed source with contamination rates induced by quasicontinuous synchrotron radiation. A modified gas-inlet system allows for the introduction of a second gas to the exposure chamber. This possibility was applied to investigate the efficiency of EUV-induced cleaning with different gas mixtures. In particular the enhancement of EUV-induced cleaning by addition of a second gas to the cleaning gas was studied.

  20. High temperature metallization system for solar cells and geothermal probes

    NASA Astrophysics Data System (ADS)

    Wiley, J. D.; Perepezko, J. H.; Nordman, J. E.

    1980-12-01

    Amorphous films of the alloys Ni-Nb, Ni-Mo, W-Si, and Mo-Si were deposited on semiconducting substrates by RF sputtering from composite cathodes. The films adhere extremely well to Si, GaAs, and GaP during and after thermal cycling from -2000 C to at least 5000 C. All films investigated to date remained amorphous during 1 hour anneals at 5000 C, and some alloy compositions were found which remain amorphous after annealing at greater than or equal to 5750 C. Rutherford backscatter analysis was used to study the diffusivity of Au in amorphous Ni-Nb.

  1. Mossbauer and XRD characterization of the phase transformations in a Fe-Mn-Al-C-Mo-Si-Cu as cast alloy during tribology test

    NASA Astrophysics Data System (ADS)

    Ramos, J.; Piamba, J. F.; Sánchez, H.; Alcazar, G. A. Pérez

    2015-06-01

    In present study Fe-29.0Mn-6Al-0.9C-1.8Mo-1.6Si-0.4Cu (%w) alloy was obtained after melted in an induction furnace, and then molded as an ingot. From the as cast ingot it were cut samples for the different characterization measurements. The microstructure of the as-cast sample is of dendritic type and its XRD pattern was refined with the lines of the austenite, with a big volumetric fraction, and the lines of the martensite, with small volumetric fraction. The Mössbauer spectrum of the sample was fitted with a broad singlet which corresponds to disordered austenite. After the tribology test, its XRD pattern was refined with the lines of two austenite phases, one similar to the previous one and other with bigger lattice parameter. The total volumetric fraction of the austenite is smaller than that obtained for sample without wear. It was added the lines of the martensite phase with bigger volumetric fraction than that of the previous sample. The Mössbauer spectrum of the weared sample was fitted with two paramagnetic sites which correspond to the two Fe austenite phases and a hyperfine magnetic field distribution which is associated to the disordered original martensite and the new one which appears in the surface as a consequence of the wear process. These results show that during wear process the original austenite phase is transformed in martensite and in a new austenite phase. The increases of the martensitic phase improves mechanical properties and wear behavior.

  2. Structure, Bonding, and Adhesion of Materials Interfaces With Density Functional Theory: Cr/Fe, SiC/Fe, MoSi2/Ni

    DTIC Science & Technology

    2006-11-01

    2002). There is a need for an improved environmental barrier coating ( EBC ) on steel which protects, not only against high temperature, but also...Fe interface. SiC may still be useful as a thin layer in a multilayer EBC system since it is resistant to diffusion of corrosive blast gases...Hutchinson, G.H. Meier, F.S. Pettit, 2001: Mechanisms controlling the durability of the thermal barrier coatings, Prog. Mater. Sci., 46 , 505-553

  3. Prediction of phase distribution pattern in phase field simulations on Mo5SiB2-primary areas in near eutectic Mo-Si-B alloy

    NASA Astrophysics Data System (ADS)

    Kazemi, O.; Hasemann, G.; Krüger, M.; Halle, T.

    2017-03-01

    A Mo-10.9Si-20.3B (if not stated otherwise all compositions are given in at.%) alloy was modeled using the phase field method with linearized phase diagrams and thermodynamic data. The simulation results showed that there are two specific microstructural constituents. According to the simulations and experimental microstructural investigations the primary Mo5SiB2 phase observed in this study was combined by the Moss-Mo3Si-Mo5SiB2 eutectics. The overall composition of the both primary and eutectic area was probed and the phase evolution along with the concentration change of the core areas were explored and visualized in the solidification domain. To verify the accuracy of the simulation results, they were comprised with the experimental achievements. In terms of the fraction of phases, the portion of the primary phase and the eutectic constituent and the phase distribution pattern our results were in good agreement with the experimental observations.

  4. Conceptual design study of concentrator enhanced solar arrays for space applications. 2kW Si and GaAs systems at 1 AU

    NASA Technical Reports Server (NTRS)

    1980-01-01

    The effect of concentration level on the specific power for a deployable, thin, gallium arsenide cell array in geosynchronous orbit for 10 years in conjunction with a two dimensional flat plate trough concentrator (V trough) and also with a multiple flat plate concentrator was investigated as well as the effects for a conventional silicon cell array on a rigid substrate. For application to a thin GaAs array at 1 AU for 10 years, the V trough produces a 19% benefit in specific power and a dramatic reduction in array area, while the multiple flat plate collector design is not only of no benefit, but is a considerable detriment. The benefit it achieves by reducing array area is duplicated by the 2D design. For the silicon array on a rigid substrate, improvement in performance due to a concentrator with ordinary mirror coating is quite small: 9% increase in specific power, and 13% reduction in array area. When the concentrator mirrors are coated with an improved cold mirror coating, somewhat more significant results are obtained: 31% specific power improvement; and 27% area reduction. In both cases, a 10 year exposure reduces BOL output by 23%.

  5. High-temperature degradation of one-dimensional metallodielectric (W/SiO2) photonic crystal as selective thermal emitter for thermophotovoltaic system

    NASA Astrophysics Data System (ADS)

    Kim, Jin Hwan; Jung, Sang Min; Shin, Moo Whan

    2017-10-01

    In this paper, thermal stability of a one-dimensional metallodielectric photonic crystal (1D MDPhC) structure based on W and SiO2 for thermophotovoltaic systems is reported. The thermal degradation mechanism of the structure, in its operating temperature range, is thoroughly investigated by using energy dispersive spectroscopy (EDS) with transmission electron microscope (TEM) and depth-profiling X-ray photoelectron spectroscopy (XPS). It is found that the structure is entirely destroyed under 1400 K by an inter-diffusion process forming a mixture of W and SiO2 without measurable oxidization of W. But, long-term annealing results in oxidization of W layer even at a lower temperature of 1300 K. During the long-term annealing, oxygen atoms in outside atmosphere are believed to cause oxidation of the upper W layer below the top SiO2 layer. Additionally, delaminated spots are observed over the surface. These thermal behaviors are potential clues to prevent or minimize thermal degradation of the multilayer structure under high temperature operation.

  6. Numerical simulation on the thermal radiative properties of a 2D SiO2/W/SiO2/W layered grating for thermophotovoltaic applications

    NASA Astrophysics Data System (ADS)

    Zhao, Yi; Fu, Ceji

    2016-10-01

    Tailoring the spectrum of thermal emission from the emitter is important for improving the performance of a thermophotovoltaic (TPV) system. In this work, a two-dimensional (2D) layered grating structure made of SiO2 and tungsten (W), which can realize wavelength-selective control of thermal emission, was proposed for a potential emitter in TPV applications. Numerical simulations of the spectral emissivity of the structure from the ultraviolet (UV) to the mid-infrared region reveals that the spectral-normal emissivity of the structure is enhanced to above 0.95 in the wavelength region from 0.55 μm to 1.9 μm for both TE and TM waves, but drops sharply at wavelength larger than 2 μm. Physical mechanisms responsible for the wavelength-selective emissivity were elucidated as due to resonance of magnetic polaritons (MPs) in the SiO2 spacer and in the grooves of the tungsten grating, Wood's anomaly (WA), excitation of surface plasmon polaritons (SPPs) and wave interference. Furthermore, the structure was found to exhibit quasi-diffuse and polarization-insensitive features of thermal emission, suggesting that the proposed structure can serve as the emitter in the design of high performance TPV systems.

  7. A 10-kW SiC Inverter with A Novel Printed Metal Power Module With Integrated Cooling Using Additive Manufacturing

    SciTech Connect

    Chinthavali, Madhu Sudhan; Ayers, Curtis William; Campbell, Steven L; Wiles, Randy H; Ozpineci, Burak

    2014-01-01

    With efforts to reduce the cost, size, and thermal management systems for the power electronics drivetrain in hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs), wide band gap semiconductors including silicon carbide (SiC) have been identified as possibly being a partial solution. This paper focuses on the development of a 10-kW all SiC inverter using a high power density, integrated printed metal power module with integrated cooling using additive manufacturing techniques. This is the first ever heat sink printed for a power electronics application. About 50% of the inverter was built using additive manufacturing techniques.

  8. Multilevel and long retentive resistive switching in low temperature nanostructured Cu/SiO{sub x}-W-SiO{sub x}/Pt

    SciTech Connect

    Wang, Jinzhi Wang, Fang; Hu, Guoqi; Liu, Xianglian; Chi, Zhenhua; Chen, Renjie; Yan, Aru; Li, Runwei

    2013-11-18

    Amorphous SiO{sub x}-based memory films are fabricated at room temperature, and study on their resistive switching characteristics and improvement approaches is performed. Multilevel resistive states with large ratio 1: ∼10{sup 2}: 3 × 10{sup 5} and long retention exceeding 2 × 10{sup 6} s at ambient temperature and humidity are observed in Cu/SiO{sub x} (9 nm)-W (∼2 nm)-SiO{sub x} (9 nm)/Pt ultrathin stack. Nonvolatile switching is consistently realized in microscopy. Based on investigations of microscopic conduction and microstructure, tungsten incorporation with copper as relay bridges for conducting filaments is proposed to attribute to the performance improvement and the multilevel switching mechanism.

  9. Amorphous metallizations for high-temperature semiconductor device applications

    NASA Technical Reports Server (NTRS)

    Wiley, J. D.; Perepezko, J. H.; Nordman, J. E.; Kang-Jin, G.

    1981-01-01

    The initial results of work on a class of semiconductor metallizations which appear to hold promise as primary metallizations and diffusion barriers for high temperature device applications are presented. These metallizations consist of sputter-deposited films of high T sub g amorphous-metal alloys which (primarily because of the absence of grain boundaries) exhibit exceptionally good corrosion-resistance and low diffusion coefficients. Amorphous films of the alloys Ni-Nb, Ni-Mo, W-Si, and Mo-Si were deposited on Si, GaAs, GaP, and various insulating substrates. The films adhere extremely well to the substrates and remain amorphous during thermal cycling to at least 500 C. Rutherford backscattering and Auger electron spectroscopy measurements indicate atomic diffussivities in the 10 to the -19th power sq cm/S range at 450 C.

  10. High-efficiency diffractive x-ray optics from sectioned multilayers

    SciTech Connect

    Kang, H C; Stephenson, G B; Liu, C; Conley, R; Macrander, A T; Maser, J; Bajt, S; Chapman, H N

    2004-12-14

    We investigate the diffraction properties of sectioned multilayers in Laue (transmission) geometry, at hard x-ray energies (9.5 and 19.5 keV). Two samples are studied, a 200 period W/Si multilayer of 29 nm d-spacing, and a 2020 period Mo/Si multilayer of 7 nm d-spacing, with cross-section depths ranging from 2 to 17 {micro}m. Rocking curves across the Bragg reflections exhibit well-defined interference fringes originating from the depth of the sample. Efficiencies as high as 70% were obtained. This exceeds the theoretical limit for standard zone plates operating in the multi-beam regime, demonstrating that all of the intensity can be directed into a single diffraction order in small-period structures.

  11. Comparison of the Thermal Expansion Behavior of Several Intermetallic Silicide Alloys Between 293 and 1523 K

    NASA Technical Reports Server (NTRS)

    Raj, Sai V.

    2014-01-01

    Thermal expansion measurements were conducted on hot-pressed CrSi(sub 2), TiSi(sub 2), W Si(sub 2) and a two-phase Cr-Mo-Si intermetallic alloy between 293 and 1523 K during three heat-cool cycles. The corrected thermal expansion, (L/L(sub 0)(sub thermal), varied with the absolute temperature, T, as (deltaL/L(sub 0)(sub thermal) = A(T-293)(sup 3) + B(T-293)(sup 2) + C(T-293) + D, where A, B, C and D are regression constants. Excellent reproducibility was observed for most of the materials after the first heat-up cycle. In some cases, the data from the first heatup cycle deviated from those determined in the subsequent cycles. This deviation was attributed to the presence of residual stresses developed during processing, which are relieved after the first heat-up cycle.

  12. Film stress studies and the multilayer laue lens project.

    SciTech Connect

    Liu, C.; Conley, R.; Macrander, A. T.; X-Ray Science Division

    2006-01-01

    A Multilayer Laue Lens (MLL) is a new type of linear zone plate, made by sectioning a planar depth-graded multilayer and used in Laue transmission diffraction geometry, for nanometer-scale focusing of hard x-rays. To produce an MLL, a depth-graded multilayer consisting of thousands of layers with a total thickness of tens of microns is needed. Additionally, the multilayer wafer has to be sectioned and polished to a thickness of {approx}10 to 25 microns to yield a diffracting grating to focus x-rays. The multilayers must have both low stress and good adhesion to survive the subsequent cutting and polishing processes, as well as sharp interfaces and accurate layer placement. Several partial MLLs using WSi{sub 2}/Si multilayers with precise zone-plate structures have been successfully fabricated. A W/Si multilayer with the same structure, however, cracked and peeled off from the Si substrate after it was grown. Here we report results of our film stress studies of dc magnetron-sputtered WSi{sub 2}, W, and Mo thin films and WSi{sub 2}/Si, W/Si, and Mo/Si multilayers grown on Si(100) substrates. The stress measurements were carried out using a stylus profiler to measure the curvatures of 2-inch-diameter, 0.5-mm-thick Si(100) wafers before and after each coating. The physical origins of the stress and material properties of these systems will be discussed.

  13. Origin of in Situ Domain Formation of Heavily Nb-Doped Pb(Zr,Ti)O3 Thin Films Sputtered on Ir/TiW/SiO2/Si Substrates for Mobile Sensor Applications.

    PubMed

    Han, Chan Su; Park, Kyu Sik; Choi, Hong Je; Cho, Yong Soo

    2017-06-07

    High-quality piezoelectric thin films have recently been in demand for mobile sensor applications. An investigation was conducted to understand the improvements in the piezoelectric and imprint characteristics of heavily Nb-doped lead zirconate titanate thin films with an extensive range of Nb content (up to 14 mol %) beyond the typical solid solubility limit of Nb. The positive effects produced by the unusual doping of Nb were realized by utilizing an in situ sputtering process that did not require a subsequent annealing and poling procedure. An enhanced piezoelectric coefficient, -e31, of -12.87 C/m(2) and a stronger shift in the coercive field, Ec,shift, of ∼20 kV/cm, which are ideally useful for mobile sensor applications, were obtained for the 12 mol % Nb-doped films deposited on nonconventional buffer electrodes of Ir/TiW. The reduced oxygen vacancy concentration and preferred domain orientation with a stronger piezoresponse induced by the Nb donor doping contributed to the enhancement of the piezoelectric properties. Potential defect dipoles aligned by a residual stress gradient along columnar structures seemed to induce an internal electric field in the Nb-doped films, leading to the preferred domain orientation, as well as the strong imprint behavior due to a clamping of domain walls.

  14. Characterization of r.f. sputtered thin Mo, W and Si films as precursors to multilayer X-ray mirrors

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, D.; Joseph, D.; Poswal, A. K.

    2006-08-01

    Single layers of Mo, W and Si thin films have been deposited by r.f. sputtering on float glass and c-Si substrates kept at room temperature. The films have been characterised by grazing incidence X-ray reflectometry (GIXR), X-ray transmission (XRT), Rutherford backscattering spectrometry (RBS), atomic force microscopy (AFM) and phase modulated spectroscopic ellipsometry (SE) studies. The thickness values obtained from the GIXR measurements have been used to calibrate the in situ thickness monitors. The surface roughness of the thin layers have also been determined from the GIXR measurements. The atomic mass density in the films have been obtained from the RBS measurements while X-ray absorption has been estimated from the XRT measurements. The surface morphology of the films has been investigated by the AFM micrographs. The Si thin films have also been characterized by the SE technique. The characterization of the samples by these complementary techniques have been very useful in optimizing the process parameters to obtain good quality layers as precursors to the fabrication of the multilayer X-ray mirrors based on Mo/Si and W/Si structures.

  15. Synchrotron x-ray study of multilayers in Laue geometry

    SciTech Connect

    Kang, H C; Stephenson, G B; Liu, C; Conley, R; Macrander, A T; Maser, J; Bajt, S; Chapman, H N

    2004-07-21

    Zone plates with depth to zone-width ratios as large as 100 are needed for focusing of hard x-rays. Such high aspect ratios are challenging to produce by lithography. We are investigating the fabrication of high-aspect-ratio linear zone plates by multilayer deposition followed by sectioning. As an initial step in this work, we present a synchrotron x-ray study of constant-period multilayers diffracting in Laue (transmission) geometry. Data are presented from two samples: a 200 period W/Si multilayer with d-spacing of 29 nm, and a 2020 period Mo/Si multilayer with d-spacing of 7 nm. By cutting and polishing we have successfully produced thin cross sections with section depths ranging from 2 to 12 {micro}m. Transverse scattering profiles (rocking curves) across the Bragg reflection exhibit well-defined interference fringes originating from the depth of the sample, in agreement with dynamical diffraction theory for a multilayer in Laue geometry.

  16. Performance of Multilayer Monochromators for Hard X-Ray Imaging with Coherent Synchrotron Radiation

    SciTech Connect

    Dietsch, R.; Holz, T.; Kraemer, M.; Weissbach, D.; Rack, A.; Weitkamp, T.; Morawe, Ch.; Cloetens, P.; Ziegler, E.; Riotte, M.; Rack, T.; Siewert, F.

    2011-09-09

    We present a study in which multilayers of different periodicity (from 2.5 to 5.5 nm), composition (W/Si, Mo/Si, Pd/B{sub 4}C, Ru/B{sub 4}C), and numbers of layers have been compared. Particularly, we chose mirrors with similar intrinsic quality (roughness and reflectivity) to study their performance (flatness and coherence of the outgoing beam) as monochromators in synchrotron radiography. The results indicate that material composition is the dominating factor for the performance. This is important to consider for future developments in synchrotron-based hard x-ray imaging methods. In these techniques, multilayer monochromators are popular because of their good tradeoff between spectral bandwidth and photon flux density of the outgoing beam, but sufficient homogeneity and preservation of the coherent properties of the reflected beam are major concerns. The experimental results we collected may help scientists and engineers specify multilayer monochromators and can contribute to better exploitation of the advantages of multilayer monochromators in microtomography and other full-field imaging techniques.

  17. Novel CD control of HTPSM by advanced process for sub-20nm tech

    NASA Astrophysics Data System (ADS)

    Jo, Sangjin; Choi, Chungseon; Oh, Sunghyun; Ha, Taejoong; Lee, Youngmo; Kim, Sangpyo; Yim, Donggyu

    2015-10-01

    As the design rule of the semiconductor shrinks, the CD MTT (Critical Dimension Mean-to-Target) specification for photomask becomes tighter. So, more precise control of CD MTT is required. We have investigated the CD MTT control and applied it to the attenuated PSM (Phase Shift Mask) successfully for several years. We can control the CD MTT of MoSi pattern by measuring Cr/MoSi pattern to estimate MoSi pattern CD and additional etch to shrink MoSi pattern as reported in previous study. At first, the MoSi pattern CD can be estimated with the Cr/MoSi pattern CD because the CD gap between MoSi pattern and Cr/MoSi pattern is relatively constant. Additional MoSi etch is performed to shrink the MoSi pattern CD after then. The CD gap alwasys exists and the variation of the CD gap is enough small to be not considered in conventional photomask production until now. However, the variation of the CD gap is not ignorable in case of sub-20 nm tech. In this study, we investigated new method to measure MoSi pattern CD before Cr strip process to eliminate the CD gap between MoSi pattern and Cr/MoSi pattern. To eliminate the CD gap, we attempt three solutions - 1) Optimize etch process to perform perfect Cr/MoSi pattern profile without the CD gap, 2) Improve CD measurement accuracy by developing new SEM measuring mechanism, 3) Develop of new process to modify Cr/MoSi pattern profile to be measured without the CD gap. It was found that the CD gap can be eliminated and MoSi pattern CD can be measured perfectly. Finally, MoSi pattern CD control was improved because of CD gap elimination.

  18. Microstructure and mechanical properties of nitrided molybdenum silicide coatings

    SciTech Connect

    Hirvonen, J.P.; Suni, I.; Kattelus, H.; Lappalainen, R.; Torri, P.; Kung, H.; Jervis, T.R.; Nastasi, M.

    1993-12-31

    Mo-Si-N films with a high nitrogen concentration were produced by sputter-deposition in nitrogen plasma. Chemical composition was determined with Rutherford backscattering and nuclear reaction analysis. Ratio of Mo to Si was 1:2 in the coatings with a nitrogen concentration of 50%. Microstructure of the as-deposited coatings on a silicon substrate was amorphous and no crystallization was found after annealing up to 1000{degree}C, although some relaxation was observed in X-ray diffraction. This was confirmed by high-resolution TEM. Hardness of Mo-Si-N films was 18.8 GPa as determined with a nanoindenter. This is significantly higher than that of MoSi{sub 2} films, 11.2 GPa. Hardness of the Mo-Si-N films increased to 24.4 GPa after annealing at 800{degree}C, which is the same as that of the tetragonal phase of MoSi{sub 2}, 25.5 GPa. Similarly, modulus of as-deposited Mo-Si-N film was higher (257 GPa) than that of MoSi{sub 2} film (222 GPa). However, only a slight increase in the modulus of the Mo-Si-N film was found after annealing at 800C, whereas the modulus of the crystallized tetragonal MoSi{sub 2} was 382 GPa. No cracking was found in the Mo-Si-N films even after annealing at 1000C.

  19. MOLYBDENUM DISILICIDE MATERIALS FOR GLASS MELTING SENSOR SHEATHS

    SciTech Connect

    J. PETROVIC; R. CASTRO; ET AL

    2001-01-01

    Sensors for measuring the properties of molten glass require protective sensor sheaths in order to shield them from the extremely corrosive molten glass environment. MoSi{sub 2} has been shown to possess excellent corrosion resistance in molten glass, making it a candidate material for advanced sensor sheath applications. MoSi{sub 2}-coated Al{sub 2}O{sub 3} tubes, MoSi{sub 2}-Al{sub 2}O{sub 3} laminate composite tubes, and MoSi{sub 2}-Al{sub 2}O{sub 3} functionally graded composite tubes have been produced by plasma spray-forming techniques for such applications.

  20. Fracture and fatigue-crack growth behavior in ductile-phase toughened molybdenum disilicide: Effects of niobium wire vs particulate reinforcements

    NASA Astrophysics Data System (ADS)

    Badrinarayanan, K.; McKelvey, A. L.; Ritchie, R. O.; Venkateswara Rao, K. T.

    1996-12-01

    A study has been made of the fracture toughness/resistance-curve (R-curve) and cyclic fatigue-crack propagation behavior in a molybdenum disilicide composite, ductile-phase toughened with nominally 20 vol pct Nb-wire mesh reinforcements (Nb m /MoSi2); results are compared with monolithic MoSi2 and MoSi2 reinforced with 20 vol pct spherical Nb particles (Nb p /MoSi2). It is found that the high aspect ratio wire reinforcements induce significant toughening in MoSi2, both under monotonic and cyclic fatigue loading conditions. Specifically, the Nb m /MoSi2 composite exhibits R-curve behavior with a steady-state fracture toughness of ˜13 MPasqrt m , compared to unstable fracture at K c values below 5 MPasqrt m in unreinforced MoSi2 or Nb p /MoSi2. Such behavior is seen to be associated with extensive crack deflection within the reaction layer between Nb and the matrix, which leads to crack bridging by the unbroken ductile phase. Similarly, resistance to fatigue-crack growth is found to be far superior in the wire-reinforced composite over pure MoSi2 and Nb p /MoSi2. Although crack paths are again characterized by extensive deflection along the Nb/matrix reaction layer, the role of crack bridging is diminished under cyclic loading due to fatigue failure of the Nb. Instead, the superior fatigue properties of the Nb m /MoSi2 composite are found to be associated with high levels of crack closure that result from highly deflected crack paths along the (Nb,Mo)5Si3 reaction layer interface.

  1. High temperature structural silicides

    SciTech Connect

    Petrovic, J.J.

    1997-03-01

    Structural silicides have important high temperature applications in oxidizing and aggressive environments. Most prominent are MoSi{sub 2}-based materials, which are borderline ceramic-intermetallic compounds. MoSi{sub 2} single crystals exhibit macroscopic compressive ductility at temperatures below room temperature in some orientations. Polycrystalline MoSi{sub 2} possesses elevated temperature creep behavior which is highly sensitive to grain size. MoSi{sub 2}-Si{sub 3}N{sub 4} composites show an important combination of oxidation resistance, creep resistance, and low temperature fracture toughness. Current potential applications of MoSi{sub 2}-based materials include furnace heating elements, molten metal lances, industrial gas burners, aerospace turbine engine components, diesel engine glow plugs, and materials for glass processing.

  2. The thermal conductivity of silicon nitride with molybdenum disilicide additions

    SciTech Connect

    Beecher, S.C.; Dinwiddie, R.B.; Abeel, A.M.; Lowden, R.A.

    1993-12-31

    Room-temperature thermal conductivity has been measured for a series of silicon nitride (Si{sub 3}N{sub 4}) matrix composites with molybdenum disilicide (MoSi{sub 2}) additions of 2, 5 10, 25 and 50 wt. %. Included in these measurements were a pure MoSi{sub 2} sample and a Si{sub 3}N{sub 4} sample containing only sintering aids. Aluminum oxide (Al{sub 2}O{sub 3}) and yttrium oxide (Y{sub 2}O{sub 3}) were added as the sintering aids, at approximately 6 and 2 respectively. When the amount of MoSi{sub 2} was increased to greater than 10 wt. %, the amount of the sintering aids necessary to densify the composite was decreased. No sintering aids were added to the pure MoSi{sub 2} sample. Thermal conductivities of the Si{sub 3}N{sub 4} sample without MoSi{sub 2} and the pure MoSi{sub 2} sample wee 36 W/m.K and 52 W/m.K respectively, which agree very well with the literature values for similar materials. No statistically significant changes were observed in the thermal conductivity for those samples containing up to 10 wt. % MoSi{sub 2}. However, between 10 and 25 wt. % MoSi{sub 2} there was a dramatic decrease in the thermal conductivity from 37 to 20.9 W/m.K. The thermal conductivity then increased steadily with further additions of MoSi{sub 2} up to 52 W/m.K for the pure MoSi{sub 2} specimen.

  3. Surface Characterization of New Biomaterials

    NASA Astrophysics Data System (ADS)

    Minciuna, M. G.; Vizureanu, P.; Abdullah, M. M. B.; Achitei, D. C.; Istrate, B.; Cimpoesu, R.; Focsaneanu, S. C.

    2017-06-01

    This paper presents the characterization of new alloys CoCrMoSi6, CoCrMoSi7, CoCrMoSi10, in terms of hardness determinations, fractographic analysis and surface analysis. The original version of the alloy was obtained by casting process in a vacuum arc furnace. Experimental results obtained from this study confirms that by increasing content of silicon, the mechanical properties are superior and the positive results obtained at surface studies favoring the formation of compounds, that lead to the reduction of alloying grade for α solid solution and the plasticity of the alloys.

  4. Laser Instrumentation for Attosecond Experimentation

    DTIC Science & Technology

    2009-06-15

    matter lab. (b) CCD image and spectrum of XUV high- harmonic pulses generated in Ne gas (black line), and reflectivity of MoSi mirror (blue). The...XUV pulses were optimized in the region around 95 eV to coincide with the high reflectivity region of the multi-layer MoSi mirror used for focusing of...piezo- controlled split mirror separately reflects XUV and near-IR pulses for precise timing delay. The MoSi mirror reflectivity cuts out a ~4-eV

  5. Chemical Reactions in the Processing of Mosi2 + Carbon Compacts

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Lee, Kang N.; Maloy, Stuart A.; Heuer, Arthur H.

    1993-01-01

    Hot-pressing of MoSi2 powders with carbon at high temperatures reduces the siliceous grain boundary phase in the resultant compact. The chemical reactions in this process were examined using the Knudsen cell technique. A 2.3 wt pct oxygen MoSi2 powder and a 0.59 wt pct oxygen MoSi2 powder, both with additions of 2 wt pct carbon, were examined. The reduction of the siliceous grain boundary phase was examined at 1350 K and the resultant P(SiO)/P(CO) ratios interpreted in terms of the SiO(g) and CO(g) isobars on the Si-C-O predominance diagram. The MoSi2 + carbon mixtures were then heated at the hot-pressing temperature of 2100 K. Large weight losses were observed and could be correlated with the formation of a low-melting eutectic and the formation and vaporization of SiC.

  6. Chemical Reactions in the Processing of Mosi2 + Carbon Compacts

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Lee, Kang N.; Maloy, Stuart A.; Heuer, Arthur H.

    1993-01-01

    Hot-pressing of MoSi2 powders with carbon at high temperatures reduces the siliceous grain boundary phase in the resultant compact. The chemical reactions in this process were examined using the Knudsen cell technique. A 2.3 wt pct oxygen MoSi2 powder and a 0.59 wt pct oxygen MoSi2 powder, both with additions of 2 wt pct carbon, were examined. The reduction of the siliceous grain boundary phase was examined at 1350 K and the resultant P(SiO)/P(CO) ratios interpreted in terms of the SiO(g) and CO(g) isobars on the Si-C-O predominance diagram. The MoSi2 + carbon mixtures were then heated at the hot-pressing temperature of 2100 K. Large weight losses were observed and could be correlated with the formation of a low-melting eutectic and the formation and vaporization of SiC.

  7. Physical and optoelectronic characterization of reactively sputtered molybdenum-silicon-nitride alloy metal gate electrodes

    NASA Astrophysics Data System (ADS)

    Patel, P.; Nadesalingam, M.; Wallace, R. M.; Buchanan, D. A.

    2009-01-01

    With continued transistor scaling, work function tuning of metal gates has become important for advanced complementary-metal-oxide-silicon applications. The work function tuning of reactively sputtered MoxSiyNz (also referred to as MoSiN) gates has been studied through the incorporation of nitrogen. The nitrogen concentration in the MoSiN films was altered by controlling the gas flow ratio, RN=N2/(N2+Ar), during gate deposition. The sheet resistance (Rs) of blanket MoSiN films, measured using four-point resistance method, was found to increase as the gas flow ratio was varied from 10% to 40%. Current-voltage measurements confirmed excellent electrical stability of MoSiN/SiO2/p-Si gate stack for applied electric fields ranging up to 6 MV/cm. High frequency capacitance-voltage measurements were used to extract the MoSiN work function (Φm) using the relationship between the flatband voltage (VFB) and the oxide thickness (tox). The extracted MoSiN/SiO2 interfacial barrier heights, obtained through the internal photoemission of electrons, were used to corroborate the extracted values of MoSiN work function. The MoSiN work functions (Φm), extracted independently using both techniques, were consistent and were observed to decrease with increasing gas flow ratio [N2/(N2+Ar)]. Secondary ion mass spectrometry depth analysis revealed uniform distribution of nitrogen throughout the bulk MoSiN films, with no piling up at gate-dielectric interface. X-ray photoelectron spectroscopy surface analysis suggested a steady increase in the Mo-N bonds, and therefore the total nitrogen concentration (from ˜20% to 32%), as the gas flow ratio is increased from 10% to 40%. A similar trend was observed in the nitrogen concentration (in percent), measured using Rutherford backscattering spectroscopy, for these gate deposition conditions. These material characterization results demonstrate that the increase in nitrogen concentration in MoSiN films is consistent with the lowering of MoSi

  8. High temperature stability multilayers for EUV condenser optics

    SciTech Connect

    Bajt, S; Stearns, D G

    2005-05-03

    We investigate the thermal stability of Mo/SiC multilayer coatings at elevated temperatures. Transmission electron microscopy and x-ray diffraction studies show that upon annealing a thermally-induced structural relaxation occurs that transforms the polycrystalline Mo and amorphous SiC layers in as-deposited multilayers into amorphous Mo-Si-C alloy and crystalline SiC, respectively. After this relaxation process is complete the multilayer is stable at temperatures up to 400 C.

  9. The chemically-specific structure of an amorphous molybdenum germanium alloy by anomalous x-ray scattering

    NASA Astrophysics Data System (ADS)

    Ishii, Hope Ami

    2002-09-01

    Since its inception in the late 1970s, anomalous x-ray scattering (AXS) has been employed for chemically-specific structure determination in a wide variety of non-crystalline materials. These studies have successfully produced differential distribution functions (DDFs) which provide information about the compositionally-averaged environment of a specific atomic species in the sample. Despite the wide success in obtaining DDFs, there are very few examples of successful extraction of the fully-chemically-specific partial pair distribution functions (PPDFs), the most detailed description of an amorphous sample possible by x-ray scattering. Extracting the PPDFs is notoriously difficult since the matrix equation involved is ill-conditioned and thus extremely sensitive to errors present in the experimental quantities that enter the equation. Instead of addressing this sensitivity by modifying the data through mathematical regularization methods, sources of error have been removed experimentally: A focussing analyzer crystal was combined with a position-sensitive linear detector to experimentally eliminate unwanted inelastic scattering intensity over most of the reciprocal space range probed. This instrumentation has been used in data collection for the extraction of PPDFs from amorphous (a)-MoGe3, the phase separation endpoint in the sputter-deposited Mo-Ge amorphous alloys. This alloy is of particular interest because it acts as the conducting phase in a percolative metal-insulator transition but has a composition with no crystalline analogue. Since the first Ge-rich compound in the Mo-Ge equilibrium system is MoGe 2, previous workers have speculated that perhaps a unique MoGe 3 compound exists in the amorphous system. Rather than indicating a distinct MoGe3 compound with definitive local structure, however, the coordination results are more consistent with a densely-packed alloy having a wide range of solid solubility. Significant improvement in the quality and

  10. The Chemically-Specific Structure of an Amorphous Molybdenum Germanium Alloy by Anomalous X-ray Scattering

    SciTech Connect

    Ishii, H. A.

    2002-06-11

    Since its inception in the late 1970s, anomalous x-ray scattering (AXS) has been employed for chemically-specific structure determination in a wide variety of noncrystalline materials. These studies have successfully produced differential distribution functions (DDFs) which provide information about the compositionally-averaged environment of a specific atomic species in the sample. Despite the wide success in obtaining DDFs, there are very few examples of successful extraction of the fully-chemically-specific partial pair distribution functions (PPDFs), the most detailed description of an amorphous sample possible by x-ray scattering. Extracting the PPDFs is notoriously difficult since the matrix equation involved is ill-conditioned and thus extremely sensitive to errors present in the experimental quantities that enter the equation. Instead of addressing this sensitivity by modifying the data through mathematical methods, sources of error have been removed experimentally: A focusing analyzer crystal was combined with a position-sensitive linear detector to experimentally eliminate unwanted inelastic scattering intensity over most of the reciprocal space range probed. This instrumentation has been used in data collection for the extraction of PPDFs from amorphous (a)-MoGe{sub 3}. This composition arises as a phase separation endpoint in the Ge-rich region of the vapor-deposited Mo-Ge amorphous alloy system but is not present at equilibrium. Since the first Ge-rich compound in the Mo-Ge equilibrium system is MoGe{sub 2}, previous workers have speculated that perhaps a unique MoGe{sub 3} compound exists in the amorphous system. Rather than indicating a distinct MoGe{sub 3} compound with definitive local structure, however, the coordination results are more consistent with a densely-packed alloy having a wide range of solid solubility. Significant improvement in the quality and reliability of experimental PPDFs from a-MoGe{sub 3} by AXS has been achieved solely

  11. MECHANICAL BEHAVIOR OF MOLYBDENUM DISILICIDE-BASED ALLOYS

    SciTech Connect

    A. MISRA; A. SHARIF; ET AL

    2000-12-01

    We have investigated the mechanical behavior of the following single-phase polycrystalline alloys with the MoSi{sub 2} body-center tetragonal structure: MoSi{sub 2} alloyed with {approximately}2.5 at.% Re, MoSi{sub 2} alloyed with 2 at.% Al, MoSi{sub 2} alloyed with 1 at.% Nb, and MoSi{sub 2} alloyed with 1 at.% Re and 2 at.% Al. Several anomalies in the mechanical behavior of alloyed materials were observed. For example, (1) addition of only {approximately}2.5 at. % Re results in an order of magnitude increase in compressive strength at 1600 C, (2) additions of Nb and Al cause solution softening at near-ambient temperatures, and (3) quaternary MoSi{sub 2}-Re-Al alloys show strengthening at elevated temperatures and reduction in flow stress with enhanced plasticity at near-ambient temperatures in compression. The mechanisms of anomalous solution hardening and softening are discussed.

  12. Combustion synthesis of molybdenum silicides and borosilicides for ultrahigh-temperature structural applications

    NASA Astrophysics Data System (ADS)

    Alam, Mohammad Shafiul

    Molybdenum silicides and borosilicides are promising structural materials for gas-turbine power plants. A major challenge, however, is to simultaneously achieve high oxidation resistance and acceptable mechanical properties at high temperatures. For example, molybdenum disilicide (MoSi2) has excellent oxidation resistance and poor mechanical properties, while Mo-rich silicides such as Mo5Si3 (called T 1) have much better mechanical properties but poor oxidation resistance. One approach is based on the fabrication of MoSi2-T 1 composites that combine high oxidation resistance of MoSi2 and good mechanical properties of T1. Another approach involves the addition of boron to Mo-rich silicides for improving their oxidation resistance through the formation of a borosilicate surface layer. In particular, Mo 5SiB2 (called T2) phase is considered as an attractive material. In the thesis, MoSi2-T1 composites and materials based on T2 phase are obtained by mechanically activated SHS. Use of SHS compaction (quasi-isostatic pressing) significantly improves oxidation resistance of the obtained MoSi2-T1 composites. Combustion of Mo-Si-B mixtures for the formation of T2 phase becomes possible if the composition is designed for the addition of more exothermic reactions leading to the formation of molybdenum boride. These mixtures exhibit spin combustion, the characteristics of which are in good agreement with the spin combustion theory. Oxidation resistance of the obtained Mo-Si-B materials is independent on the concentration of Mo phase in the products so that the materials with a higher Mo content are preferable because of better mechanical properties. Also, T2 phase has been obtained by the chemical oven combustion synthesis technique.

  13. Development of high-transmittance phase-shifting mask for ArF immersion lithography

    NASA Astrophysics Data System (ADS)

    Ahn, Won-suk; Seo, Hwan-Seok; Bang, Ju-Mi; Kim, Ji-Young; Song, Jae-Min; Seung, Byoung-Hoon; Kim, Hee-Bom; Jeon, Chan-Uk

    2015-07-01

    A new PSM using high transmittance is developed to overcome patterning process limits in ArF immersion lithography. We optimized mask structure, materials, and film thicknesses for patterning process. A new material for phase-shifter is applied to the HT-PSM to exhibit higher transmittance in ArF wavelengths and the thickness of the new material is thinner than that of the conventional 6% phase-shifter (MoSiON). A new blank structure using a MoSi shading layer with double Cr hardmasks (HM) is developed and suggested for the HTPSM process. Double HM blank stacks enable the HT-PSM to adopt thin PR process for resolution enhancement in mask process. The first Cr on the MoSi is utilized as a HM to etch MoSi shading layer, an adhesion layer for PR process, and also a capping layer to protect blind area during MoSi and phase-shifter etching. In contrast, the role of the second Cr between MoSi and phase-shifter is an etch stopper for MoSi and a HM to etch phase-shifter at the same time. However, Double HM process has some problems, such as first Cr removal during second Cr etching and complex process steps. To solve the Cr removal issues, we evaluated various Cr layers which have different etchrates and compositions. According to the evaluations, we optimized thicknesses and compositions of the two Cr layers and corresponding etching conditions. Lithography simulations demonstrate that the new HT-PSM has advantages in NILS in aerial images. As a result, initial wafer exposure experiments using the HT-PSM show 13-32% improvements in LCDU compared to that of the conventional 6% PSM due to its higher NILS.

  14. Synthesis and design of silicide intermetallic materials

    SciTech Connect

    Petrovic, J.J.; Castro, R.G.; Butt, D.P.

    1997-04-01

    The overall objective of this program is to develop structural silicide-based materials with optimum combinations of elevated temperature strength/creep resistance, low temperature fracture toughness, and high temperature oxidation and corrosion resistance for applications of importance to the U.S. processing industry. A further objective is to develop silicide-based prototype industrial components. The ultimate aim of the program is to work with industry to transfer the structural silicide materials technology to the private sector in order to promote international competitiveness in the area of advanced high temperature materials and important applications in major energy-intensive U.S. processing industries. The program presently has a number of developing industrial connections, including a CRADA with Schuller International Inc. targeted at the area of MoSi{sub 2}-based high temperature materials and components for fiberglass melting and processing applications. The authors are also developing an interaction with the Institute of Gas Technology (IGT) to develop silicides for high temperature radiant gas burner applications, for the glass and other industries. Current experimental emphasis is on the development and characterization of MoSi{sub 2}-Si{sub 3}N{sub 4} and MoSi{sub 2}-SiC composites, the plasma spraying of MoSi{sub 2}-based materials, and the joining of MoSi{sub 2} materials to metals.

  15. Ceramic-silicide composites

    SciTech Connect

    Petrovic, J.J.

    1998-12-01

    The area of ceramic-silicide composites represents a merging of structural ceramics and structural silicides. Such ceramic-silicide composites can possess the desirable characteristics of both classes of compounds. Important structural ceramics are materials such as Si{sub 3}N{sub 4}, SiC, Al{sub 2}O{sub 3}, and ZrO{sub 2}, which possess covalent, ionic, or mixed covalent-ionic atomic bonding. An important structural silicide is MoSi{sub 2}, which possesses mixed covalent-metallic bonding. The arena of ceramic-silicide composites encompasses both composites where the structural silicide is the matrix and the structural ceramic is the reinforcement, and composites where the structural ceramic is the matrix and the structural silicide is the reinforcement. In the former area, MoSi{sub 2}-SiC, MoSi{sub 2}-ZrO{sub 2}, and MoSi{sub 2}-Al{sub 2}O{sub 3} composites are discussed. In the latter area, Si{sub 3}N{sub 4}-MoSi{sub 2} composites are described.

  16. Processing temperature effects on molybdenum disilicide

    SciTech Connect

    Wade, R.K. ); Petrovic, J.J. . Materials Science and Technology Div.)

    1992-11-01

    This paper reports on a series of MoSi[sub 2] compacts that were fabricated at increasing hot-pressing temperatures to achieve different grain sizes. The materials were evaluated by Vickers indentation fracture to determine room-temperature fracture toughness, hardness, and fracture mode. From 1500[degrees] to 1800[degrees] C, MoSi[sub 2] had a constant 67% transgranular fracture and linearly increasing rain size from 14 to 21 [mu]m. Above 1800[degrees]C, the fracture percentage increased rapidly to 97% transgranular at 1920[degrees]C (32 [mu] grain size). Fracture toughness and hardness decreased slightly with increasing temperature. MoSi[sub 2] processed at 1600[degrees]C had the highest fracture toughness and hardness values of 3.6 MPa[center dot]m[sup 1/2] and 9.9 GPa, respectively. The effects of SiO[sub 2] formation from oxygen impurities in the MoSi[sub 2] starting powders and MoSi[sub 2]-Mo[sub 5]Si[sub 3] eutectic liquid formation were studied.

  17. Synthesis of molybdenum disilicide by mechanical alloying

    SciTech Connect

    Schwarz, R.B.; Srinivasan, S.R.; Petrovic, J.J.; Maggiore, C.J.

    1991-01-01

    We have used mechanical alloying (MA), a high-energy ball-milling process, to prepare MoSi{sub 2} and MoSi{sub 2}-based alloys starting from mixtures of the pure elements. This synthesis route has the potential for preparing oxygen-free MoSi{sub 2} and the flexibility for close control of second-phase additions. MA, first developed for producing oxide-dispersions in Ni-based superalloys, takes advantage of the atomic-level mixing accomplished by the intense mechanical working of the alloy constituents. All the alloying reactions during the process occur in the solid-state. This technique is thus well-suited for synthesizing high melting point materials such as MoSi{sub 2}. The product of the MA process is a highly homogeneous and fine-grained powder. Its purity is determined by the purity of the starting materials and possible impurities introduced during processing. However, a careful control of the MA process enables a minimization of the impurities. We also report here the consolidation of the mechanically alloyed powder and the characterization of the MoSi{sub 2} alloys by optical and transmission electron microscopy, x-ray diffraction, and mechanical property measurements. 21 refs., 9 figs.

  18. Focus shift impacted by mask 3D and comparison between Att. PSM and OMOG

    NASA Astrophysics Data System (ADS)

    Liu, Yansong; Su, Xiaojing; Dong, LiSong; Song, Zhiyang; Guo, Moran; Su, Yajuan; Wei, Yayi

    2015-03-01

    The impact of mask three dimensions (M3D) effect on lithography processes is getting more pronounced from 32 nm nodes1-2. In this paper, we report four research progresses on the M3Deffect. Firstly, the impacts of M3D effect on the best focus (BF) offset were studied with though pitch as test pattern. The M3D effect has negative impacts on the BF, generating the BF offset pattern by pattern. The BF offset strongly depends on MoSi film thickness (THK). However the impact of MoSi profile, or side wall angle (SWA) could be ignored. Secondly, M3D OPC is needed to mitigate the shift of dose and focus center. Thirdly, as long as enough shade, the thinner MoSi, the less BF shift, as electromagnetic field (EMF) effect makes space behave smaller, which leads to higher contrast but higher mask error enhancement factor(MEEF); So the trade-off between contrast and MEEF is needed. And MoSi THK 43.7 nm in production supposed to be the optimized value from this study. Finally, compared to attenuating phase shifting mask (att.PSM) mask, opaque MoSi on Glass (OMOG) mask is more robust in terms of MEEF, the normalized image logarithmic slope (NILS) etc., not obviously influenced by mask duty ratio.

  19. USE OF A COBALT BASED METALLIC-GLASS IN JOINING MOSI2 TO STAINLESS STEEL

    SciTech Connect

    R. VAIDYA; P. RANGASWAMY; ET AL

    2001-04-01

    The successful use of a cobalt-based metallic-glass in joining molybdenum disilicide (MoSi{sub 2}) to stainless steel 316L was demonstrated. Such joints are being investigated for sensor tube applications in glass melting operations. The cobalt-based metallic-glass (METGLAS{trademark} 2714A) was found to wet the MoSi{sub 2} and stainless steel surfaces and provide high quality joints. Joining was completed at 1050 C for 60 minutes in two different ways; either by feeding excess braze into the braze gap upon heating or by constraining the MoSi{sub 2}/stainless steel assembly with an alumina (Al{sub 2}O{sub 3}) fixture during the heating cycle. These steps were necessary to ensure the production of a high quality void free joint. Post-brazing metallographic evaluations coupled with quantitative elemental analysis indicated the presence of a Co-Cr-Si ternary phase with CoSi and CoSi{sub 2} precipitates within the braze. The residual stresses in these molybdenum disilicide (MoSi{sub 2})/stainless steel 316 L joints were evaluated using X-ray diffraction and instrumented indentation techniques. These measurements revealed that significant differences are induced in the residual stresses in MoSi{sub 2} and stainless steel depending on the joining technique employed. Push-out tests were carried out on these joints to evaluate the joint strength.

  20. Structure and soft magnetic properties of the bulk samples prepared by compaction of the mixtures of Co-based and Fe-based powders

    NASA Astrophysics Data System (ADS)

    Füzer, J.; Bednarčík, J.; Kollár, P.; Roth, S.

    2007-09-01

    Ball milling of CoFeZrB ribbons and subsequent compaction of the resulting powders were used to prepare bulk amorphous samples. Further, two sets of powder samples were prepared by cryomilling of FeCuNbMoSiB alloy in amorphous and nanocrystalline state. Amorphous and nanocrystalline FeCuNbMoSiB powders were blended with CoFeZrB powder at different concentrations. Such powder mixtures were consolidated and several bulk nanocomposites have been synthesized. An addition of nanocrystalline or amorphous FeCuNbMoSiB powder to amorphous CoFeZrB powder caused a decrease of the magnetostriction of the resultant bulk samples, while the coercivity shows an opposite behavior. Our results show that the powder consolidation by hot pressing is an alternative method for the preparation of bulk metallic glasses, which are difficult to prepare by casting methods.

  1. The analysis and minimization of oxygen contamination in the powder processing of molybdenum disilicide

    SciTech Connect

    Shannon, Kruse

    1994-04-24

    Problems with MoSi2 include low-temperature fracture toughness, high-temperature creep resistance, and ``pest`` phenomena. Oxygen introduced by powder processing may be the cause of some of these problems. This study led to the following conclusions: Supplied powders have significant oxygen present prior to processing (up to 2.5 %), in the form of silica on the surface. This oxygen contamination did not increase by exposure to air at room temperature. An improved powder processing method was developed that uses glass encapsulation. Analysis of microstructures created from powders that contained 4900 to 24,100 ppM oxygen showed that the silica was transferred to the fully dense MoSi2 as SiO2 inclusions. A method of producing MoSi2 with less oxygen was attempted.

  2. Method for characterizing mask defects using image reconstruction from X-ray diffraction patterns

    DOEpatents

    Hau-Riege, Stefan Peter

    2007-05-01

    The invention applies techniques for image reconstruction from X-ray diffraction patterns on the three-dimensional imaging of defects in EUVL multilayer films. The reconstructed image gives information about the out-of-plane position and the diffraction strength of the defect. The positional information can be used to select the correct defect repair technique. This invention enables the fabrication of defect-free (since repaired) X-ray Mo--Si multilayer mirrors. Repairing Mo--Si multilayer-film defects on mask blanks is a key for the commercial success of EUVL. It is known that particles are added to the Mo--Si multilayer film during the fabrication process. There is a large effort to reduce this contamination, but results are not sufficient, and defects continue to be a major mask yield limiter. All suggested repair strategies need to know the out-of-plane position of the defects in the multilayer.

  3. Influence of molybdenum silicide additions on high-temperature oxidation resistance of silicon nitride materials

    SciTech Connect

    Klemm, H.; Tangermann, K.; Schubert, C.; Hermel, W.

    1996-09-01

    The influence of additions of molybdenum disilicide (MoSi{sub 2}) on the microstructure and the mechanical properties of a silicon nitride (Si{sub 3}N{sub 4}) material, with neodymium oxide (Nd{sub 2}O{sub 3}) and aluminum nitride (AlN) as sintering aids, was studied. The composites, containing 5, 10, and 17.6 wt% MoSi{sub 2}, were fabricated by hot pressing. All materials exhibited a similar phase composition, detected by X-ray diffractometry. Up to MoSi{sub 2} additions of 10 wt%, mechanical properties such as strength, fracture toughness, or creep at 1,400 C were not affected significantly, in comparison to that of monolithic Si{sub 3}N{sub 4}. The oxidation resistance of the composites, in terms of weight gain, degraded. After 1,000 h of oxidation at 1,400 and 1,450 C in air, a greater weight gain (by a factor of approximately three) was obtained, in comparison to that of the material without MoSi{sub 2}. Nevertheless, after 1,000 h of oxidation, the degradation in strength of the composites was considerably less severe than that of the material without MoSi{sub 2}. An additional layer was formed, caused by processes at the surface of the Si{sub 3}N{sub 4} material, preventing the formation of pores, cracks, or glassy-phase-rich areas, which are common features of oxidation damage in Si{sub 3}N{sub 4} materials. This surface layer, containing Mo{sub 5}Si{sub 3} and silicon oxynitride (Si{sub 2}ON{sub 2}), was the result of reactions between MoSi{sub 2}, Si{sub 3}N{sub 4}, and the oxygen penetrating by diffusion into the material during the high-temperature treatment.

  4. Molybdenum Silicide Formation on Single Crystal, Polycrystalline and Amorphous Silicon: Growth, Structure and Electrical Properties

    NASA Astrophysics Data System (ADS)

    Doland, Charles Michael

    The solid state reactions that occur between a thin metal film and a silicon substrate are of scientific and technological interest. The initial interactions are poorly understood, yet the final state may critically depend on the initial interactions. In this work, the reactions of thin molybdenum films on amorphous, polycrystalline, and single crystal silicon substrates were studied, with an emphasis on the initial interdiffusion and the nucleation of the crystalline silicide phase. Our research was carried out in an ultrahigh vacuum (UHV) system in order to minimize effects of contaminants. In situ Raman scattering and Auger electron spectroscopy were used to probe the structure and composition of the films. Electron microscopy, low energy electron diffraction and Schottky barrier height measurements were used to obtain additional information. The hexagonal phase of the disilicide (h-MoSi _2) is the first phase formed. This occurs after 30 minute annealing at 400^ circC on clean samples. Impurities interfere with this reaction, but substrate crystallinity has no effect. The hexagonal phase transforms to the tetragonal phase (t-MoSi_2) after 800 ^circC annealing for all substrate types. Contamination retards this reaction, resulting in films containing both phases. For the thin films in this study, the transformation to t-MoSi_2 is accompanied by agglomeration of the films. From bulk thermodynamics, t-MoSi_2 is expected to be the first phase formed, but h -MoSi_2 is the first phase observed. This phase nucleates before t-MoSi_2, due to a lower silicide-silicon interfacial energy. Detailed knowledge of interfacial energies and effects of impurities are required to understand the initial phases of thin film solid state reactions.

  5. Synthesis and design of intermetallic materials - molybdenum disilicide

    SciTech Connect

    Petrovic, J.J.; Castro, R.G.; Butt, D.P.

    1995-05-01

    The objective of this program is to develop structural silicide-based composite materials with optimum combinations of elevated temperature strength/creep resistance, low temperature fracture toughness, and high temperature oxidation resistance for applications of importance to the U.S. processing industry. A further objective is to develop silicide-based prototype industrial components. The ultimate aim of the program is to work with industry to transfer the structural silicide materials technology to the private sector in order to promote international competitiveness in the area of advanced high temperature composite materials and important applications in major energy-intensive U.S. processing industries. The program presently has a number of developing industrial connections, including a CRADA with the advanced materials company Advanced Refractory Technologies Inc. and interactions targeted at developing industrial gas burner and metal and glass melting/processing applications. Current experimental emphasis is on the development and characterization of SiC reinforced-MoSi{sub 2} matrix composites, plasma sprayed MoSi{sub 2}-based materials and microlaminate composites, and MoSi{sub 2} reinforced-Si{sub 3}N{sub 4} matrix composites. We are developing processing methods for MoSi{sub 2{minus}}based materials and microlaminate composites, and MoSi{sub 2} reinforced-Si{sub 3}N{sub 4} matrix composites. We are developing processing methods for MoSi{sub 2{minus}} based materials, such as plasma spraying/spray forming and electrophoretic deposition. We are also pursuing the fabrication of prototype industrial gas burner and injection tube components of these materials, as well as prototype components for glass processing.

  6. Atomistic Potentials for the Molybdenum-Silicon System

    SciTech Connect

    M. I. Baskes

    1998-11-01

    Using a modified version of the Embedded Atom Method (EAM) that includes angular forces, potentials are developed for the Mo/Si system. Previously developed potentials for Mo and Si are used. The cross potential is fit to properties of MoSi2, Mo3Si, and Mo5Si3. Predictions are presented for phase stability, lattice constants, elastic constants, and point and planar defect energies. In general the agreement with experiment is good, but the predicted lattice constants are somewhat greater than experiment.

  7. JPRS Report, Science & Technology, Japan

    DTIC Science & Technology

    1991-01-31

    Pressure-Sintered (MoSi2-SiC)/TiAl FGM [Junzo Fujioka; KEISHA KINO ZAIRYO KENKYUKAI, 22 May 90].. 20 Fabrication Process, Evaluation of FGMs [Ryuzo...Watanabe; SHIN SOZAI 21 SEKI FORUM, 24 Apr 90]..... 32 Thermally Resistant FGMs by CVD Method [Chihiro Kawai, et al.; SHIN SOZAI 21 SEKI FORUM, 24 Apr...4J 60 ,fi <r B u .-■ +J ^ H O o cd 4J O H oo o\\ 19 ADVANCED MATERIALS Gas Pressure-Sintered (MoSi2~SiC)/TiAl FGM 91FE0069A Tokyo

  8. Silicon-nitride and metal composite

    DOEpatents

    Landingham, Richard L.; Huffsmith, Sarah A.

    1981-01-01

    A composite and a method for bonding the composite. The composite includes a ceramic portion of silicon nitride, a refractory metal portion and a layer of MoSi.sub.2 indirectly bonding the composite together. The method includes contacting the layer of MoSi.sub.2 with a surface of the silicon nitride and with a surface of the metal; heating the layer to a temperature below 1400.degree. C.; and, simultaneously with the heating, compressing the layer such that the contacting is with a pressure of at least 30 MPa. This composite overcomes useful life problems in the fabrication of parts for a helical expander for use in power generation.

  9. Thin film molybdenum silicide as potential temperature sensors for turbine engines

    NASA Technical Reports Server (NTRS)

    Ho, C. H.; Prakash, S.; Deshpandey, C. V.; Doerr, H. J.; Bunshah, R. F.

    1989-01-01

    Temperature measurements of Mo-Si-based thin-film resistance thermometers were studied. Annealing in an argon ambient at a temperature above 1000 C for at least 1 h is required to form the stable tetragonal MoSi2 phase. With a crack-free 2-micron-thick AlN barrier layer on top, a sensor was tested up to 1200 C. The resistivity vs temperature characteristic shows the room temperature resistivity and temperature coefficient of resistivity (TCR) of the sensor to be approximately 350 microohm and 0.01195 K, respectively. No film adhesion problems were observed for at least four testing cycles.

  10. Phenomenological study of the behavior of some silica formers in a high velocity jet fuel burner

    NASA Technical Reports Server (NTRS)

    Cawley, J. D.; Handschuh, R. F.

    1985-01-01

    Samples of four silica formers: single crystal SiC, sintered alpha-SiC, reaction sintered Si3N4 and polycrystalline MoSi2, were subjected to a Mach 1 jet fuel burner for 1 hr, at a sample temperature of 1375 deg C (2500 deg F). Two phenomena were identified which may be deleterious to a gas turbine application of these materials. The glass layer formed on the MoSi2 deformed appreciably under the aerodynamic load. A scale developed on the samples of the other materials which consisted of particular matter from the gas stream entrapped in a SiO2 matrix.

  11. Silicon-nitride and metal composite

    DOEpatents

    Landingham, R.L.; Huffsmith, S.A.

    A composite and a method for bonding the composite are described. The composite includes a ceramic portion of silicon nitride, a refractory metal portion and a layer of MoSi/sub 2/ indirectly bonding the composite together. The method includes contacting the layer of MoSi/sub 2/ with a surface of the silicon nitride and with a surface of the metal; heating the layer to a temperature below 1400/sup 0/C; and, simultaneously, compressing the layer such that the contacting is with a pressure of at least 30 MPa. This composite overcomes useful life problems in the fabrication of parts for a helical expander for use in power generation.

  12. Thin film molybdenum silicide as potential temperature sensors for turbine engines

    NASA Technical Reports Server (NTRS)

    Ho, C. H.; Prakash, S.; Deshpandey, C. V.; Doerr, H. J.; Bunshah, R. F.

    1989-01-01

    Temperature measurements of Mo-Si-based thin-film resistance thermometers were studied. Annealing in an argon ambient at a temperature above 1000 C for at least 1 h is required to form the stable tetragonal MoSi2 phase. With a crack-free 2-micron-thick AlN barrier layer on top, a sensor was tested up to 1200 C. The resistivity vs temperature characteristic shows the room temperature resistivity and temperature coefficient of resistivity (TCR) of the sensor to be approximately 350 microohm and 0.01195 K, respectively. No film adhesion problems were observed for at least four testing cycles.

  13. Multilayer films with sharp, stable interfaces for use in EUV and soft X-ray application

    DOEpatents

    Barbee, Jr., Troy W.; Bajt, Sasa

    2002-01-01

    The reflectivity and thermal stability of Mo/Si (molybdenum/silicon) multilayer films, used in soft x-ray and extreme ultraviolet region, is enhanced by deposition of a thin layer of boron carbide (e.g., B.sub.4 C) between alternating layers of Mo and Si. The invention is useful for reflective coatings for soft X-ray and extreme ultraviolet optics, multilayer for masks, coatings for other wavelengths and multilayers for masks that are more thermally stable than pure Mo/Si multilayers

  14. Method and apparatus for detecting the presence and thickness of carbon and oxide layers on EUV reflective surfaces

    DOEpatents

    Malinowski, Michael E.

    2005-01-25

    The characteristics of radiation that is reflected from carbon deposits and oxidation formations on highly reflective surfaces such as Mo/Si mirrors can be quantified and employed to detect and measure the presence of such impurities on optics. Specifically, it has been shown that carbon deposits on a Mo/Si multilayer mirror decreases the intensity of reflected HeNe laser (632.8 nm) light. In contrast, oxide layers formed on the mirror should cause an increase in HeNe power reflection. Both static measurements and real-time monitoring of carbon and oxide surface impurities on optical elements in lithography tools should be achievable.

  15. Vortex shells in mesoscopic triangles of amorphous superconducting thin films

    NASA Astrophysics Data System (ADS)

    Kokubo, N.; Miyahara, H.; Okayasu, S.; Nojima, T.

    2016-11-01

    Direct observation of vortex states confined in mesoscopic regular triangle dots of amorphous Mo-Ge thin films was made with a scanning superconducting quantum interference device microscope. The observed magnetic images illustrate clearly how vortices are distributed over the triangle dots by forming not only commensurate triangular clusters, but also unique patterns imposed by incommensurability. We discuss the results in terms of vortex shells and construct the packing sequence of vortices in the multiple shell structure.

  16. Development of Metallic Magnetic Calorimeters with a Critical Temperature Switch

    NASA Astrophysics Data System (ADS)

    Kim, S. R.; Choi, J.; Jo, H. S.; Kang, C. S.; Kim, G. B.; Kim, H. L.; Kim, I. W.; Lee, H. J.; Lee, J. H.; Lee, M. K.; Oh, S. Y.; Sala, E.; So, J. H.; Yoon, W. S.; Kim, Y. H.

    2016-07-01

    We report on the progress in the development of meander-shaped metallic magnetic calorimeters (MMCs) with a critical temperature switch. A niobium meander-shaped coil in an MMC is arranged to form a superconducting loop. It is to measure the change in magnetization and to apply a persistent current that magnetizes the MMC sensor material. In this work, part of the superconducting loop is fabricated with another superconducting material with its transition temperature (T_C) lower than that of niobium. A persistent current can be injected in the loop while reducing the temperature from above to below the T_C of the switch. Aluminum (Al) wires and an alloy of molybdenum and germanium (MoGe) were tested as critical temperature switch. The test with the Al switch demonstrated the temperature switch concept for meander-shaped MMCs that require a large field current. Microfabricated MoGe switches showed a T_C near 4.3 K, but only 7 mA of persistent current could be charged due to MoGe film discontinuity. This issue requires further improvement in the fabrication procedure.

  17. Porous acicular mullite obtained by controlled oxidation of waste molybdenum disilicide

    SciTech Connect

    Bučevac, Dušan; Dapčević, Aleksandra; Maksimović, Vesna

    2014-02-01

    Highlights: • Waste MoSi{sub 2} heating elements were used as starting material for fabrication of porous acicular mullite. • Calcined MoSi{sub 2} powder was source of SiO{sub 2} and pore former at the same time. • Porous acicular mullite is promising material for filtration of diesel engine exhaust. • Samples with decent mechanical integrity and porosity of more than 60% were fabricated. - Abstract: Porous acicular mullite was fabricated by using waste MoSi{sub 2} heating element and Al{sub 2}O{sub 3}. Careful calcination of the pulverized heating element led to the formation of a mixture of MoO{sub 3} and amorphous SiO{sub 2}. This mixture was employed as both SiO{sub 2} precursor and pore former. The oxidation of MoSi{sub 2} and mullite formation were studied. The effect of fabrication temperature on phase composition, porosity, grain morphology, and compressive strength of sintered mullite was examined. Pure mullite with porosity of more than 60% and compressive strength of ∼20 MPa was obtained at temperature as low as 1300 °C. The microstructure consisted of elongated, rectangular, prism-like grains which are known to be effective in filtration of diesel engine exhaust. The increase in sintering temperature caused the change of grain morphology and reduction in compressive strength.

  18. Stability of ZrBe[sub 17], and NiBe intermetallics during intermediate temperature oxidation

    SciTech Connect

    Chou, T.C.; Nieh, T.G.; Wadsworth, J . Research and Development Div.)

    1992-10-01

    This paper reports that since the finding of MoSi[sub 2] pest by Fitzer in 1955, a number of intermetallic compounds, e.g., ZrBe[sub 13], WSi[sub 2], and NiAl have also been reported to exhibit similar behavior during oxidation in air. For example, Lewis reported that catastrophic failure (total disintegration into powders) occurred in ZrBe[sub 13] when oxidized at 700[degrees]C in air. X-ray diffraction analyses revealed that the powders were composed of BeO, ZrO[sub 2] (cubic), Zr[sub 2]Be[sub 17], and unreacted ZrBe[sub 13]. Regardless of numerous cited incidents of pest in intermetallics, fundamental understanding of pest is very limited. Recently, MoSi[sub 2] pest has been studied in a great detail and fundamental insights to the mechanism of pest have been established. It is found that both single- and ply- crystalline MoSi[sub 2] are susceptible to pest, which leads to the disintegration of test samples into powder consisting of MoO[sub 3] whiskers, SiP[sub 2] clusters, and residual MoSi[sub 2] crystals. Pest is also noted to associate with substantial volume expansion of the samples. Most important, the occurrence of pest is contingent upon the formation of blisters, resulting from volume expansion by oxidation and the evaporation of MoO[sub 3] on the surfaces and grain boundary interfaces.

  19. Molybdenum disilicide composites produced by plasma spraying

    SciTech Connect

    Castro, R.G.; Hollis, K.J.; Kung, H.H.; Bartlett, A.H.

    1998-05-25

    The intermetallic compound, molybdenum disilicide (MoSi{sub 2}) is being considered for high temperature structural applications because of its high melting point and superior oxidation resistance at elevated temperatures. The lack of high temperature strength, creep resistance and low temperature ductility has hindered its progress for structural applications. Plasma spraying of coatings and structural components of MoSi{sub 2}-based composites offers an exciting processing alternative to conventional powder processing methods due to superior flexibility and the ability to tailor properties. Laminate, discontinuous and in situ reinforced composites have been produced with secondary reinforcements of Ta, Al{sub 2}O{sub 3}, SiC, Si{sub 3}N{sub 4} and Mo{sub 5}Si{sub 3}. Laminate composites, in particular, have been shown to improve the damage tolerance of MoSi{sub 2} during high temperature melting operations. A review of research which as been performed at Los Alamos National Laboratory on plasma spraying of MoSi{sub 2}-based composites to improve low temperature fracture toughness, thermal shock resistance, high temperature strength and creep resistance will be discussed.

  20. Microwave assisted synthesis of technologically important transition metal silicides

    SciTech Connect

    Vaidhyanathan, B.; Rao, K.J.

    1997-12-01

    A novel, simple, clean and fast microwave assisted method of preparing important transition metal silicides (MoSi{sub 2}, WSi{sub 2}, CoSi{sub 2}, and TiSi{sub 2}) has been described. Amorphous carbon is used both as a microwave susceptor and as a preventer of oxidation. {copyright} {ital 1997 Materials Research Society.}

  1. Strength and Toughness Improvement of Silicide Intermetallics by Nanophase and Microphase Reinforcements

    DTIC Science & Technology

    1993-10-01

    porosity and increase in grain size with time for m onolithic M oSi2 ...param eters for M oSi2 ............................................................................. 33 18. Mo wire in MoSi2 HIPed at 1700°C/4 h...powder-, Nb wire-, and Nb foil-reinforced M oSi2 ............................................................................. 51 30. Fracture

  2. Silicide Coating Fabricated by HAPC/SAPS Combination to Protect Niobium Alloy from Oxidation.

    PubMed

    Sun, Jia; Fu, Qian-Gang; Guo, Li-Ping; Wang, Lu

    2016-06-22

    A combined silicide coating, including inner NbSi2 layer and outer MoSi2 layer, was fabricated through a two-step method. The NbSi2 was deposited on niobium alloy by halide activated pack cementation (HAPC) in the first step. Then, supersonic atmospheric plasma spray (SAPS) was applied to obtain the outer MoSi2 layer, forming a combined silicide coating. Results show that the combined coating possessed a compact structure. The phase constitution of the combined coating prepared by HAPC and SAPS was NbSi2 and MoSi2, respectively. The adhesion strength of the combined coating increased nearly two times than that for single sprayed coating, attributing to the rougher surface of the HAPC-bond layer whose roughness increased about three times than that of the grit-blast substrate. After exposure at 1200 °C in air, the mass increasing rate for single HAPC-silicide coating was 3.5 mg/cm(2) because of the pest oxidation of niobium alloy, whereas the combined coating displayed better oxidation resistance with a mass gain of only 1.2 mg/cm(2). Even more, the combined coating could significantly improve the antioxidation ability of niobium based alloy at 1500 °C. The good oxidation resistance of the combined silicide coating was attributed to the integrity of the combined coating and the continuous SiO2 protective scale provided by the oxidation of MoSi2.

  3. Dense nanometric microalloyed molybdenum disilicide synthesized through mechanical and field activation

    NASA Astrophysics Data System (ADS)

    Woolman, Joseph Nelson

    There has been no theoretical improvements in the high temperature capability of materials used in the hot sections of turbines since 1941 [2]. Exploitation of the nickel based super-alloys to their fullest potential is a result of processing improvement, mainly in the form of vacuum arc melt furnaces [3]. Anton and Shah [4, 5] report based on ultimate tensile strength (UTS), creep strength and oxidation resistance that seven intermetallic compounds with melting points above 1600°C, have been selected as possible replacement materials for high temperature structural materials. These selected compounds are as Nb3Al, Cr3Si, Co2Nb, MoSi 2, Mo5Si3 and Nb2Al. In the terms of UTS and oxidation resistance, MoSi2 is the material with the most promise [5]. Before MoSi2 is set for industrial application, numerous problems have to be solved. High on the list is the brittle to ductile transition at approximately 1000°C. Waghmare et al., from first principles, list elements which introduced at the microalloying level offer the possibility for ductility improvement in MoSi2 without sacrificing its outstanding high temperature properties. Of the elements listed m their model, the one with the most promise as a softener of MoSi2 is magnesium. Until now, this compound had not been synthesized. Through a combination of mechanical alloying and spark plasma sintering, we were able to successfully synthesize the compound Mo(Si 2-xMgx). Hardness results presented above confirm the predictions of Waghmare et al. in that a substantial reduction in hardness was realized. Material prepared identically, lacking magnesium, displayed a hardness of 2000 Vickers, while material with 5 at% magnesium displayed a hardness of 620 Vickers. The elements predicted by Waghmare et al. to have the greatest softening potential on alpha-MoSi2: Al and Mg substituting for Si and Nb and V substituting for Mg were explored. The results for Mg match the predictions, while the results for Al, Nb and V match the

  4. Damage resistant and low-stress Si-based multilayer mirrors

    NASA Astrophysics Data System (ADS)

    Feigl, Torsten; Yulin, Sergey A.; Kuhlmann, Thomas; Kaiser, Norbert

    2001-12-01

    Applications of multilayer mirrors for extreme ultraviolet lithography (EUVL) require not only a high normal incidence reflectivity but also a long lifetime and minimal residual stress. A serious problem of Mo-Si multilayers is the structural instability in the case of localized absorption of in- and outband radiation from the EUV source followed by the degradation of the multilayer. A number os solutions have been envisaged in the past, including the use of compound materials (MoSi2Si) as well as the use of C barrier layers. We focused our interest on two Si-based systems: Mo/Si and Mo2C/Si multilayer mirrors. The mirrors were designed for normal incidence reflectivity at about 13 nm wavelength and were deposited by dc magnetron sputtering. Maximum normal incidence reflectivities of 68.4%12.8 nm for Mo/Si multilayer mirrors and 66.8%12.8 nm for Mo2C/Si have been achieved. Investigating the thermal stability of the multilayers in the temperature range from 300 degree(s)C to 500 degree(s)C we found that the reflectivity of Mo/Si mirrors is drastically decreasing after annealing above 300 degree(s)C, whereas the Mo2C/Si multilayers show a superior stability up to 400 degree(s)C...500 degree(s)C. Another problem of EUV multilayer mirrors is the large residual compressive stress (-400 to - 500 MPa), which causes undesirable distortion of the substrate figure. The reduction of residual stress of Mo/Si and Mo2C/Si multilayers with annealing has been investigated. Using a slow thermal annealing (1 degree(s)C/min), it is possible to reduce the stress from -520 MPa to zero by heating the Mo/Si samples up to 310 degree(s)C. However, this results ina reflectivity drop of about 3...4%. On the other hand one can reduce the stress of a Mo2C/Si multilayer from -490 MPa to zero by annealing without a considerable reflectivity drop.

  5. Phase identification in reactive sintering of molybdenum disilicide composites

    SciTech Connect

    Alba, Jr., Jose

    1996-10-01

    Molybdenum disilicide has been predominantly used for furnace heating elements, but recently there has been interest in its use for high temperature structural applications. The reason for this increased interest stems from its desirable characteristics which are a high melting point, relatively low density, good oxidation resistance, relatively good thermal conductivity and electronically conductive. The melting point of MoSi2 is approximately 2030°C as compared to a melting point of 1340°C for the Ni-based superalloys. This could potentially give MoSi2 a big advantage over the Ni-based superalloys in turbine applications because the operating temperature can be increased resulting in an increase in turbine efficiency and reduced emissions. The relatively low density (6.25g/cm3) compared to the Ni-based superalloys (8.9 g/cm3) is an important advantage in turbine applications because of the need for low weight. Good oxidation resistance stems from the ability of MoSi2 to form a protective SiO2 surface layer when exposed to oxygen. Another advantageous feature of MoSi2 is its thermal conductivity which is superior to Ni-based superalloys at low temperatures and comparable to the Ni-based superalloys at high temperatures. This allows heat to be dissipated at a rate better than ceramics and comparable to metals. MoSi2 is electrically conductive allowing it to be electro discharge machined. This is desirable since conventional ceramics are not generally conductive and cannot be electro discharge machined.

  6. Use of lower-end technology etch platforms for high-etch loads

    NASA Astrophysics Data System (ADS)

    Nemelka, Jefferson O.

    2003-12-01

    In order to meet the needs of multiple customers with varying design specifications, merchant photomask suppliers need to provide photomasks for a wide range of design patterns. Some masks require etching less than 1% of the total mask film, while others require etching over 80% of the mask. Etching masks with these extremes in pattern loads can often require upgrading existing tool sets, particularly as the mask specifications become tighter. One alternative to upgrading tools is to develop new load-specific processes on existing lower-end tools, which requires a substantial amount of development work. Dry etching MoSi Embedded Attenuating Phase Shift Material using sulfur hexafluoride and helium under all etch loads presents challenges in the Unaxis Generation II mask etch platform. Etch processes developed for low load masks cannot always be used for high load masks due to problems in maintaining a stable process with good performance. In order to improve the etch performance for high MoSi loads (> 70% clear), a Gen II specific hardware design which can adversely affect uniformity at high loads was identified and eliminated as a dominant source of non-uniformity. A DOE studying total gas flow, He/SF6 ratio, pressure, ICP, and RIE power was then used to identify a stable process window for high MoSi loads. Another DOE studying the effects of pressure, ICP power, and RIE power on process uniformity was then carried out within the stable process window. Process conditions were identified which produced highly loaded 248nm and 193nm EAPSM masks with phase uniformity below 3°. Sidewall profiles were vertical for 193nm MoSi films but were slightly tapered for 248nm MoSi films, both with less than 5nm of CD bias.

  7. Microstructure and mechanical properties of metal/oxide and metal/silicide interfaces

    SciTech Connect

    Shaw, L.; Miracle, D.; Abbaschian, R.

    1995-12-01

    Fracture energies of Al{sub 2}O{sub 3}/Nb interfaces and MoSi{sub 2}/Nb interfaces with and without Al{sub 2}O{sub 3} coating were measured using sandwich-type chevron-notched specimens. The relations between the mechanical properties, microstructures, types of bonds at the interface and processing routes were explored. The fracture energy of the Al{sub 2}O{sub 3}/Nb interface was determined to be 9 J/m{sup 2} and changed to 16 J/m{sup 2} when Nb was pre-oxidized before the formation of the Al{sub 2}O{sub 3}/Nb interface. The fracture energy of the MoSi{sub 2}/Nb interface could not be determined directly because of the formation of the interfacial compounds. However, the fracture energy at the MoSi{sub 2}/Nb interfacial region was found to depend on the interfacial bond strength, roughness of interfaces and microstructure of interfacial compounds. The interfacial fracture energies of Al{sub 2}O{sub 3} with silicides, MoSi{sub 2}, Nb{sub 5}Si{sub 3}, or (Nb, Mo)Si{sub 2} were estimated to be about 16 J/m{sup 2}, while the interfacial fracture energies between two silicides or between Nb and a silicide were larger than 34 J/m{sup 2}. The measured fracture energies between two silicides or between Nb and a silicide were larger than 34 J/m{sup 2}. The measured fracture energies of the various interfaces are discussed in terms of the interfacial microstructures and types of bonds at the interfaces.

  8. Comparative study on PS material of EAPSM for flat panel display

    NASA Astrophysics Data System (ADS)

    Jeong, Jin-Woong; Song, Jin-Han; Lee, Ho-Jin; Kim, Kyu-Sik; Jeong, Woo-Gun; Yoon, Young-Jin; Yun, Sang-Pil; Jung, Sung-Mo

    2016-10-01

    We evaluated and compared the i-line 5.2 % Cr based EAPSM and i-line 5.2 % MoSi based EAPSM to find more appropriate material of shifter for FPD. The evaluation items were their CD linearity, phase shift, and optical properties such as transmittance, reflectance, and absorbance under the wavelength range 200-800 nm. Finally, from the results, we performed simulations. The CD linearity and the phase shift were seen as the performances of the same level within all their specifications. The optical properties indicated that the transmittance was higher in the i-line 5.2 % Cr based EAPSM than in i-line 5.2 % MoSi based EAPSM from about 350 nm wavelength, and the reflectance was lower in the iline 5.2 % Cr based EAPSM than in i-line 5.2 % MoSi based EAPSM under the entire wavelength region. From these results, NILS and contrast were simulated between them in 5.0 μm pitch LS pattern and it was found that they did not have a significant difference. Side-lobe effect appeared in both EAPSMs when clear features were closely adjacent under 2.0 μm contact pattern. However, the side-lobe could be removed effectively by adopting Rim type EAPSM. The i-line 5.2 % MoSi based EAPSM may be more suitable for the Rim type EAPSM than the i-line 5.2 % Cr based EAPSM considering their structure and production process of the Rim type EAPSM. It may be appropriate that we use the i-line 5.2 % Cr based EAPSM in LS pattern and the i-line 5.2 % MoSi based EAPSM in contact pattern, because they were almost same level in that performance perspective.

  9. Raman study of phase transformation from diamond structure to wurtzite structure in the silicon nanowires

    NASA Astrophysics Data System (ADS)

    Shukla, A. K.; Dixit, Saurabh

    2016-07-01

    Hexagonal silicon has emerged as an exciting material due to its novel vibrational and electronic properties. Synthesis of the wurtzite silicon nanowires (w-SiNWs) is studied here using metal assisted chemical etching (MACE) technique. Stress induced in the SiNWs during wet chemical etching is attributed to formation of the w-SiNWs. Presence of the w-SiNWs is revealed by first-order and second-order Raman spectra. The effect of variation of deposition time of silver (catalyst) is explicitly studied for growth of w-SiNWs. The deposition time enhances the density of SiNWs in an island of vertically aligned SiNWs. Absorption coefficient studies of the w-SiNWs are also conducted using UV-vis spectroscopy as a function of deposition time. Increase in the absorption coefficient in SiNWs is noticed with increasing deposition time. The prominent quantum confinement along with stress and porosity is shown to be mainly responsible for the transformation from diamond structure to wurtzite structure in the silicon nanowires.

  10. Monochromateur multicouche X-UV à bande passante étroite et faible fond continu

    NASA Astrophysics Data System (ADS)

    Benbalagh, R.; André, J.-M.; Barchewitz, R.; Ravet, M.-F.; Delmotte, F.; Bridou, F.; Julié, G.; Bosseboeuf, A.; Laval, R.; Rémond, C.; Soullié, G.; Troussel, P.; Fialin, M.

    2002-07-01

    The principle of a multilayer monochromator with a narrow bandwidth and a low specular background is recalled. The elaboration of such a monochromator obtained from a Mo/Si multilau-yer mirror is briefly described. The performance of the device measured at 1500 and 98eV is presented. Le principe d'un monochromateur multicouche à bande passante étroite et présentant un faible fond continu est rappelé. Nous décrivons brièvement la fabrication d'un tel monochromateur obtenu à partir d'un miroir multicouche Mo/Si. Les performances de ce dispositif mesurées à 1500 et 98eV sont présentées.

  11. Fracture toughness dependence on grain size in molybdenum silicide, titanium silicide and aluminum nitride

    NASA Astrophysics Data System (ADS)

    Tsyfanskiy, Vyacheslav Alex

    The fracture toughness of MoSi2, Ti5Si3 and AlN as a function of grain size was measured using the controlled-flaw method in conjunction with the miniaturized disk-bend test (MDBT). The materials investigated had grain sizes of 3.5, 7.0, 11.2 and 16 mum for MoSi 2, 2, 4, 7 and 10--20 mum for Ti5Si 3 and 2.5 and 4.5 mum for AlN. The specimens used in the experiments were 3 mm in diameter and varied in thickness from 280 to 593 mum. These were indented using a Vickers pyramid indentor to indentation loads varying from 10 to 80 N. Indentation cracking was experienced at all indentation loads and R-curve behavior was exhibited. The fracture toughness, Kinfinity, was calculated using a straightforward graphical procedure involving an empirical R-curve equation. Kinfinity of MoSi2 was determined to be relatively grain-size independent, with a value of ˜4 MPa·m1/2. Kinfinity, of Ti5Si3 showed a strong dependence on grain size, with maximum of 3.56 +/- 0.41 MPa·m1/2 at a grain size of ˜4 mum. For AlN Kinfinity decreased from 2.85 +/- 0.40 to 2.32 +/- 0.21 MPa·m1/2 as the grain size increased. The grain growth behavior of polycrystalline MoSi2, Ti 5Si3 and AlN was studied during static annealing at 1400°C in an argon atmosphere. MoSi2 exhibited abnormal grain growth, Ti5Si3 showed normal grain growth behavior and annealing of AlN produced no visible increase in the grain size. The presence of Ni in contact with MoSi2 during annealing significantly increased the rate of grain growth. MoSi2 with grain sizes of 11.2 and 16 mum contained traces of Ni and exhibited a decrease in hardness compared to the Ni-free samples with grain sizes of 3.5 and 7.0 mum. Stresses arising in non-cubic materials during processing, due to the presence of thermal expansion anisotropy, were calculated for AlN, Al 2O3, MoSi2, SiC, Ti5Si3 and ZnS. These stresses, sigmamax, provide information on the maximum grain sizes, ds, that can be tolerated by these materials before they fracture

  12. Soft X-Ray Optics by Pulsed Laser Deposition

    NASA Technical Reports Server (NTRS)

    Fernandez, Felix E.

    1996-01-01

    Mo/Si and C/Co multilayers for soft x-ray optics were designed for spectral regions of interest in possible applications. Fabrication was effected by Pulsed Laser Deposition using Nd:YAG (355 nm) or excimer (248 nm) lasers in order to evaluate the suitability of this technique. Results for Mo/Si structures were not considered satisfactory due mainly to problems with particulate production and target surface modification during Si ablation. These problems may be alleviated by a two-wavelength approach, using separate lasers for each target. Results for C/Co multilayers are much more encouraging, since indication of good layering was observed for extremely thin layers. We expect to continue investigating this possibility. In order to compete with traditional PVD techniques, it is necessary to achieve film coverage uniformity over large enough areas. It was shown that this is feasible, and novel means of achieving it were devised.

  13. X-ray photoelectron spectroscopy study of radiofrequency-sputtered refractory compound steel interfaces

    NASA Technical Reports Server (NTRS)

    Wheeler, D. R.; Brainard, W. A.

    1978-01-01

    Radiofrequency sputtering was used to deposit Mo2C, Mo2B5, and MoSi2 coatings on 440C steel substrates. Both sputter etched and preoxidized substrates were used, and the films were deposited with and without a substrate bias of -300 V. The composition of the coatings was measured as a function of depth by X-ray photoelectron spectroscopy combined with argon ion etching. In the interfacial region there was evidence that bias produced a graded interface in Mo2B5 but not in Mo2C. Oxides of iron and of all film constituents except carbon were presented in all cases but the iron oxide concentration was higher and the layer thicker on the preoxidized substrates. The film and iron oxides were mixed in the MoSi2 and Mo2C films but layered in the Mo2B5 film. The presence of mixed oxides correlates with enhanced film adhesion.

  14. Multilayer optics for advanced X-ray applications; Proceedings of the Meeting, San Diego, CA, July 22, 23, 1991

    NASA Astrophysics Data System (ADS)

    Ceglio, Natale M.

    1992-01-01

    Topics discussed in these proceedings include multilayer fabrication and characterization, applications of multilayer technology, and damage and survivability of multilayer mirrors. Papers are presented on high-performance multilayer mirrors for soft X-ray projection lithography, multilayer coatings on figured optics, a simulation of the growth of Mo/Si multilayers, boron-based multilayers for soft X-ray optics, reflection masks for soft X-ray projection lithography, and multilayer mirrors for XUV Ge laser wavelengths. Attention is also given to soft X-ray reflectometry of multilayer coatings using a laser-plasma source, annealing studies of Ru/Si multilayer by high-angle annular dark-field microscopy and HREM, the fabrication and characterization of beryllium-based multilayer mirrors for soft X-rays, structural changes induced by thermal annealing in W/C multilayers, thermal stability of Mo/Si multilayers, and repair of high-performance multilayer coatings.

  15. Carbon buffer layers for smoothing superpolished glass surfaces as substrates for molybdenum /silicon multilayer soft-x-ray mirrors.

    PubMed

    Stock, H J; Hamelmann, F; Kleineberg, U; Menke, D; Schmiedeskamp, B; Osterried, K; Heidemann, K F; Heinzmann, U

    1997-03-01

    Zerodur and BK7 glass substrates (developed by Fa. Glaswerke Schott, D-55014 Mainz, Germany) from Carl Zeiss Oberkochen polished to a standard surface roughness of varsigma = 0.8 nm rms were coated with a C layer by electron-beam evaporation in the UHV. The roughness of the C-layer surfaces is reduced to 0.6 nm rms. A normal-incidence reflectance of 50% at a wavelength of 13 nm was measured for a Mo/Si multilayer soft-x-ray mirror with 30 double layers (N = 30) deposited onto the BK7/C substrate, whereas a similar Mo/Si multilayer (N = 30) evaporated directly onto the bare BK7 surface turned out to show a reflectance of only 42%.

  16. Hydrogen in titanium alloys

    SciTech Connect

    Wille, G W; Davis, J W

    1981-04-01

    The titanium alloys that offer properties worthy of consideration for fusion reactors are Ti-6Al-4V, Ti-6Al-2Sn-4Zr-2Mo-Si (Ti-6242S) and Ti-5Al-6Sn-2Zr-1Mo-Si (Ti-5621S). The Ti-6242S and Ti-5621S are being considered because of their high creep resistance at elevated temperatures of 500/sup 0/C. Also, irradiation tests on these alloys have shown irradiation creep properties comparable to 20% cold worked 316 stainless steel. These alloys would be susceptible to slow strain rate embrittlement if sufficient hydrogen concentrations are obtained. Concentrations greater than 250 to 500 wppm hydrogen and temperatures lower than 100 to 150/sup 0/C are approximate threshold conditions for detrimental effects on tensile properties. Indications are that at the elevated temperature - low hydrogen pressure conditions of the reactors, there would be negligible hydrogen embrittlement.

  17. Microstructure of hot-pressed Al2O3-Si3N4 mixtures as a function of holding temperature

    NASA Technical Reports Server (NTRS)

    Yeh, H. C.

    1976-01-01

    Powder mixtures of 40 m/o Si3N4-60 m/o Al2O3 were hot-pressed at 4000 psi at various holding temperatures from 1100 C to 1700 C. Scanning Electron Microscopy and Transmission Electro Microscopy results were correlated to X-ray phase analysis and density measurements. The progressively developed microstructure was used to interpret the densification behavior of SiAlON. Photomicrographs of microstructures are shown.

  18. Characterization of Ultra High Temperature Ceramics via Transmission Electron Microscopy. Part 2: UHTCs sintered with addition of TaSi2

    DTIC Science & Technology

    2010-01-21

    hafnium diborides and carbides belong to the class of materials defined UHTCs (Ultra-High-Temperature-Ceramics). These materials are of particular...are finally compared to composites sintered with addition of the same amount of MoSi2. FA8655-09-M-4002 8 1. Introduction Zirconium, hafnium ... alloying elements. High temperatures decrease the liquid surface tension and promote wettability. Also, the spreading rate towards equilibrium is enhanced

  19. Heat treatment giving a stable high temperature micro-structure in cast austenitic stainless steel

    DOEpatents

    Anton, Donald L.; Lemkey, Franklin D.

    1988-01-01

    A novel micro-structure developed in a cast austenitic stainless steel alloy and a heat treatment thereof are disclosed. The alloy is based on a multicomponent Fe-Cr-Mn-Mo-Si-Nb-C system consisting of an austenitic iron solid solution (.gamma.) matrix reinforced by finely dispersed carbide phases and a heat treatment to produce the micro-structure. The heat treatment includes a prebraze heat treatment followed by a three stage braze cycle heat treatment.

  20. Electric field-activated combustion synthesis of ceramics and composites

    SciTech Connect

    Munir, Z.A.

    1995-12-31

    The use of an electric field to activate self-propagating combustion synthesis is demonstrated. With the simultaneous application of a field and an ignition source, self-sustaining combustion waves can be initiated in systems which are thermodynamically excluded from such reactions at 298K. The use of the field-activated combustion synthesis (FACS) has been successfully demonstrated in a variety of single phase and composite systems. The synthesis of {beta}-SiC is described as an example of single phase systems. A minimum (threshold) field strength of about 6 V/cm is required to initiate and propagate the reaction between silicon and graphite. At or slightly above the threshold, the wave propagates in a non-steady state (pulsating) mode. As the field is increased the velocity of propagation increases and becomes independent of time and distance, i.e. steady-state. The application of high fields (> - 21 V/cm) results in simultaneous combustion without the need for an ignition source. The use of FACS in the preparation of composites was also investigated. Composites of MoSi{sub 2}-SiC, MoSi{sub 2}-Nb, MoSi{sub 2}-ZrO{sub 2}, and B{sub 4}C-TiB, were synthesized by this method. For the system (1-x) MoSi{sub 2}-xSiC, composites with 0{le}x{le}1.0 can be synthesized by self-propagating combustion. For each value of x, a threshold field is required to initiate the wave. In the case of y B{sub 4}C-TiB{sub 2} composites, systems with y {le} 0.5 can be synthesized without the field. When a field is imposed, composites with y values up to 5 have been successfully synthesized by self-propagating combustion.

  1. OSA Proceedings of the Topical Meeting on Soft-X-Ray Projection Lithography Held in Monterey, California on 10-12 April 1991. Volume 12

    DTIC Science & Technology

    1992-05-22

    Carbide because of its high thermal the mirror on its backside or edge. Shott Zerodur conductivity. Edge cooling causes a larger exceeded the limit by about...Characterization Angstrom-level noncontact profiling of mirrors for soft x-ray lithography............ 134 Paul Glenn Nonspecular Scattering from X-Ray...structed by patterning a Mo/Si Tropel Division of GCA Corporation. multilayer coated silicon wafer. The mirrors were coated at AT&T Bell The multilayer

  2. Silicide-matrix materials for high-temperature applications

    SciTech Connect

    Meschter, P.J.; Schwartz, D.S. )

    1989-11-01

    Intermetallic-matrix composites are attractive alternatives to carbon/carbon and ceramic/ceramic composities for applications up to 1,600 C. Recent work on the intermetallic compounds MoSi2 and Ti5Si3 has included determination of their mechanical properties and deformation behavior, selection of thermodynamically compatible high-strength and ductile reinforcements, and strengthening and toughening mechanisms in silicide-matrix composites for high-temperature service. 11 refs.

  3. Phase stability, electronic structure and mechanical properties of molybdenum disilicide: a first-principles investigation

    NASA Astrophysics Data System (ADS)

    Qiao, Yingjie; Zhang, Hexin; Hong, Changqing; Zhang, Xiaohong

    2009-05-01

    The phase stability, electronic structure and mechanical properties of MoSi2 at different phases were systematically investigated by first-principles density functional theory calculations. The results indicated that both tetragonal and hexagonal MoSi2 are thermodynamically and mechanically stable. The formation energy of the hexagonal phase is 6.27 kJ mol-1 smaller than that of the tetragonal one. In tetragonal MoSi2, Mo 4dxz, 4dyz and 4d_{z}^{2} orbitals overlap effectively with Si sp_{z}^{1} , px and py ones, while interactions between Mo 4d_{{x}^{2}-{y}^{2}} (4dxy) and Si 2p orbitals are confirmed in the hexagonal phase. However, the bond strengths of the hexagonal phase are smaller, leading to changes in the mechanical properties. Young's modulus decreases from 443.33 to 341.37 GPa as the phase transforms from the tetragonal to the hexagonal phase. The weakness of the Si-Mo bonds along the [0 0 1] direction and the Si-Si bonds within the (0 0 1) plane make the shear deformations of the hexagonal phase much easier to occur, and the G/B ratio correspondingly decreases, suggesting improvement in ductility. Moreover, the calculated Vicker's hardness of the hexagonal phase is 10.15 GPa, 48% smaller than the value in the tetragonal one. Besides the structural transformation, the external pressure can also affect the mechanical properties of the system. Different from the structural change, the external pressure enhances the Si-Si interactions while it reduces the Si-Mo (II) bond populations. Both the Vicker's hardness and ductility are improved as the hydrostatic pressure increases. The present calculations confirmed that the Si-Si (I) interactions play a central role in the hardness and ductility of MoSi2 materials.

  4. Symposium on Structural Intermetallics: Perspectives on Science and Technology Held at the Defence Metallurgical Research Laboratory, Hyderabad, India on 5-6 February 1994. Volume 2

    DTIC Science & Technology

    1994-02-06

    Contribution from France T.Khan and S.Naka ONERA, France 4. Microstructure, Processing and Properties of MoSi2 D.A. Hardwick Rockwell Science Centre, USA i 5...Effect of Microstructure on the Creep of Molybdenum Disilicides and their Composites3 K. Sadananda and R. Feng Naval Research Laboratory, USA i 6... properties such as low density, high thermal conductivity and excellent environmental resistance. Nevertheless, a reasonable combination of toughness and

  5. Innovative Processing of Composites for Ultra-High Temperature Applications. Book 3

    DTIC Science & Technology

    1993-11-01

    order to created MoSi 2/SiC composites. (Molybdenum disilicide has much better mechanical properties at high temperatures than silicon.) Investigations...technology necessary to fabricate ceramic-matrix, internetallic-matrix, and metal-matrix composites with superior mechanical properties in high temperature...Book I Section 1 Processing and Properties of Silicon Carbide Fibers Principal Investigators: C.D. Batich M.D. Sacks Section 2 Processing of Mullite

  6. Reactive Processing and Co-Extrusion of Ultra-High Temperature Ceramics and Composites

    DTIC Science & Technology

    2006-02-28

    properties , :and performance of zirconium diboride ceramics were studied. The initial phase of the work focused on improving the properties of...used for hot pressing ZrB2-SiC .................... 6 Table II. Physical and mechanical properties of ZrB2-SiC materials...6 Table III. Physical and mechanical properties of ZrB2 -MoSi2 materials .......................... 7 Table IV. Physical and mechanical

  7. The unexpected mechanism of carbonyl hydrosilylation catalyzed by (Cp)(ArN[double bond, length as m-dash])Mo(H)(PMe(3)).

    PubMed

    Shirobokov, Oleg G; Gorelsky, Serge I; Simionescu, Razvan; Kuzmina, Lyudmila G; Nikonov, Georgii I

    2010-11-07

    Complex (Cp)(ArN[double bond, length as m-dash])Mo(H)(PMe(3)) (2, Ar = 2,6-diisopropylphenyl) catalyzes the hydrosilylation of carbonyls by an unexpected associative mechanism. Complex 2 also reacts with PhSiH(3) by a σ-bond metathesis mechanism to give the silyl derivative (Cp)(ArN[double bond, length as m-dash])Mo(SiH(2)Ph)(PMe(3)).

  8. Plastic deformation of single crystals of WSi{sub 2} with the C11{sub b} structure

    SciTech Connect

    Ito, K.; Yano, T.; Nakamoto, T.; Inui, H.; Yamaguchi, M.

    1999-02-05

    The deformation behavior of single crystals of WSi{sub 2} has been investigated as a function of crystal orientation in the temperature range from room temperature to 1500 C in compression. Single crystals of WSi{sub 2} can be deformed only at high temperatures above 1100 C, in contrast to MoSi{sub 2} in which plastic flow is possible even at room temperature. Four slip systems, {l_brace}110{r_brace}{l_angle}111{r_angle}, {l_brace}011{r_brace}{l_angle}100{r_angle}, {l_brace}023{r_brace}{l_angle}100{r_angle} and (001){l_angle}100{r_angle}, are identified. While the former three slip systems are operative also in MoSi{sub 2}, the (001){l_angle}100{r_angle} slip is only operative in WSi{sub 2}. The (001){l_angle}100{r_angle} slip in WSi{sub 2} is the alternative to {l_brace}013{r_brace}{l_angle}331{r_angle} slip in MoSi{sub 2} since they are operative in the same orientation range. Slip on {l_brace}110{r_brace}{l_angle}331{r_angle} is hardly observed in WSi{sub 2}. The values of critical resolved shear stress (CRSS) for the commonly observed slip systems are much higher in WSi{sub 2} than in MoSi{sub 2} with the largest difference for {l_brace}110{r_brace}{l_angle}111{r_angle} slip. The higher CRSS values in WSi{sub 2} are not only due to the intrinsic difference in the deformation behavior but also due to the existence of numerous grown-in stacking faults on (001).

  9. Method to adjust multilayer film stress induced deformation of optics

    DOEpatents

    Spiller, Eberhard A.; Mirkarimi, Paul B.; Montcalm, Claude; Bajt, Sasa; Folta, James A.

    2000-01-01

    Stress compensating systems that reduces/compensates stress in a multilayer without loss in reflectivity, while reducing total film thickness compared to the earlier buffer-layer approach. The stress free multilayer systems contain multilayer systems with two different material combinations of opposite stress, where both systems give good reflectivity at the design wavelengths. The main advantage of the multilayer system design is that stress reduction does not require the deposition of any additional layers, as in the buffer layer approach. If the optical performance of the two systems at the design wavelength differ, the system with the poorer performance is deposited first, and then the system with better performance last, thus forming the top of the multilayer system. The components for the stress reducing layer are chosen among materials that have opposite stress to that of the preferred multilayer reflecting stack and simultaneously have optical constants that allow one to get good reflectivity at the design wavelength. For a wavelength of 13.4 nm, the wavelength presently used for extreme ultraviolet (EUV) lithography, Si and Be have practically the same optical constants, but the Mo/Si multilayer has opposite stress than the Mo/Be multilayer. Multilayer systems of these materials have practically identical reflectivity curves. For example, stress free multilayers can be formed on a substrate using Mo/Be multilayers in the bottom of the stack and Mo/Si multilayers at the top of the stack, with the switch-over point selected to obtain zero stress. In this multilayer system, the switch-over point is at about the half point of the total thickness of the stack, and for the Mo/Be--Mo/Si system, there may be 25 deposition periods Mo/Be to 20 deposition periods Mo/Si.

  10. Study of local in-homogeneity in ion beam mixing using SIMS ion imaging techniques

    SciTech Connect

    Singh, Ch. Kishan; Ilango, S.; Dash, S.; Tyagi, A. K.

    2012-06-05

    The local in-homogeneity in ion beam mixing of Mo/Si system subjected to 110keV Ar{sup +} ion implantation is studied using secondary ion imaging. Sequences of images are recorded across the interface and depth profiles are constructed from different regions of the image planes. Our results show a significant variation in decay length indicative of in-homogeneity in mixing.

  11. Effect of structure and deposition technology on tribological properties of DLC coatings alloyed with VIA group metals

    NASA Astrophysics Data System (ADS)

    Khrushchov, M.; Levin, I.; Marchenko, E.; Avdyukhina, V.; Petrzhik, M.

    2016-07-01

    The results of a comprehensive research on atomic structure, phase composition, micromechanical and tribological characteristics of alloyed DLC coatings have been presented. The coatings have been deposited by reactive magnetron sputtering in acetylene-nitrogen gas mixtures of different compositions (a-C:H:Cr), by plasma-assisted chemical vapor deposition in atmospheres of silicone-organic precursor gases (a-C:H:Mo:Si), and by nonreactive magnetron sputtering of a composite target (a-C:H:W).

  12. Plasma-materials interaction results at Sandia National Laboratories.

    SciTech Connect

    Causey, Rion A.; Wampler, William R.; Buchenauer, Dean A.; Karnesky, Richard A.; Whaley, Josh A.; Cowgill, Donald F.; Kolasinski, Robert D.

    2010-08-01

    Overview of Plasma Materials Interaction (PMI) activities are: (1) Hydrogen diffusion and trapping in metals - (a) Growth of hydrogen precipitates in tungsten PFCs, (b) Temperature dependence of deuterium retention at displacement damage, (c) D retention in W at elevated temperatures; (2) Permeation - (a) Gas driven permeation results for W/Mo/SiC, (b) Plasma-driven permeation test stand for TPE; and (3) Surface studies - (a) H-sensor development, (b) Adsorption of oxygen and hydrogen on beryllium surfaces.

  13. Spectroscopic characterization of novel multilayer mirrors intended for astronomical and laboratory applications

    NASA Astrophysics Data System (ADS)

    Ragozin, Eugene N.; Mednikov, Konstantin N.; Pertsov, Andrei A.; Pirozhkov, Alexander S.; Reva, Anton A.; Shestov, Sergei V.; Ul'yanov, Artem S.; Vishnyakov, Eugene A.

    2009-05-01

    We report measurements of the reflection spectra of (i) concave (spherical and parabolic) Mo/Si, Mg/Si, and Al/Zr multilayer mirrors (MMs) intended for imaging solar spectroscopy in the framework of the TESIS/CORONAS-FOTON Satellite Project and of (ii) an aperiodic Mo/Si MM optimized for maximum uniform reflectivity in the 125-250 Å range intended for laboratory applications. The reflection spectra were measured in the configuration of a transmission grating spectrometer employing the radiation of a tungsten laser-driven plasma as the source. The function of detectors was fulfilled by backside-illuminated CCDs coated with Al or Zr/Si multilayer absorption filters. High-intensity second-order interference reflection peaks at wavelengths of about 160 Å were revealed in the reflection spectra of the 304-Å Mo/Si MMs. By contrast, the second-order reflection peak in the spectra of the new-generation narrow-band (~12 Å FWHM) 304-Å Mg/Si MMs is substantially depressed. Manifestations of the NEXAFS structure of the L2, 3 absorption edges of Al and Al2O3 were observed in the spectra recorded. The broadband Mo/Si MM was employed as the focusing element of spectrometers in experiments involving (i) the charge exchange of multiply charged ions with the donor atoms of a rare-gas jet; (ii) the spectroscopic characterization of a debris-free soft X-ray radiation source excited by Nd laser pulses in a Xe jet (iii) near-IR-to-soft-X-ray frequency conversion (double Doppler effect) occurring in the retroreflection from the relativistic electron plasma wake wave (flying mirror) driven by a multiterawatt laser in a pulsed helium jet.

  14. Multilayer coatings for x-ray optics made by distributed electron cyclotron resonance (DECR) plasma sputtering

    NASA Astrophysics Data System (ADS)

    Hoghoj, Peter; Ziegler, Eric; Lueken, Eike; Peffen, Jean-Christophe; Freund, Andreas K.

    1994-11-01

    Distributed electron cyclotron resonance (DECR) plasma sputtering was used for depositing W/Si multilayers for x-rya optics. The argon plasma used in the sputtering process was excited by the DECR method. The DECR argon plasma diffusing the middle of the deposition chamber was characterized with a Langmuir probe. The ionization rate was found to be 7 X 10-4. This allowed us to sputter W and Si with a large range of target bias values at low pressures. Deposited single layers and W/Si multilayers were characterized with grazing incidence x-ray reflectometry. As an illustration of the capabilities, data is shown for a W/Si multilayer with period d equals 3.0 nm and an interface roughness (sigma) < 0.47 nm.

  15. Reflective masks for extreme ultraviolet lithography

    SciTech Connect

    Nguyen, Khanh Bao

    1994-05-01

    Extreme ultraviolet lithographic masks are made by patterning multilayer reflective coatings with high normal incidence reflectivity. Masks can be patterned by depositing a patterned absorber layer above the coating or by etching the pattern directly into the coating itself. Electromagnetic simulations showed that absorber-overlayer masks have superior imaging characteristics over etched masks (less sensitive to incident angles and pattern profiles). In an EUVL absorber overlayer mask, defects can occur in the mask substrate, reflective coating, and absorber pattern. Electromagnetic simulations showed that substrate defects cause the most severe image degradation. A printability study of substrate defects for absorber overlayer masks showed that printability of 25 nm high substrate defects are comparable to defects in optical lithography. Simulations also indicated that the manner in which the defects are covered by multilayer reflective coatings can affect printability. Coverage profiles that result in large lateral spreading of defect geometries amplify the printability of the defects by increasing their effective sizes. Coverage profiles of Mo/Si coatings deposited above defects were studied by atomic force microscopy and TEM. Results showed that lateral spread of defect geometry is proportional to height. Undercut at defect also increases the lateral spread. Reductions in defect heights were observed for 0.15 μm wide defect lines. A long-term study of Mo/Si coating reflectivity revealed that Mo/Si coatings with Mo as the top layer suffer significant reductions in reflectivity over time due to oxidation.

  16. JOINING OF MOLYBDENUM DISILICIDE TO STAINLESS STEEL USING AMORPHOUS METAL BRAZES-RESIDUAL STRESS ANALYSIS

    SciTech Connect

    VAIDYA, RAJENDRA U; KAUTZ, DOUGLAS D.; GALLEGOS, DAVID E.

    2007-01-30

    Molybdenum disilicide (MoSi{sub 2})/stainless steel 316 L jOints were produced by high temperature brazing using a cobalt-based metallic-glass (METGLAS{trademark} 2714A). Successful joining was completed in two different ways; either by feeding excess braze into the braze gap upon heating or by constraining the MoSi{sub 2}/stainiess steel assembly with an alumina (Al{sub 2}O{sub 3}) fixture during the heating cycle. These steps were necessary to ensure the production of a high quality void free joint. Residual stress measurements were completed on these joints. Indentation results show higher tensile residual stresses in the stainless steel for the joint with the external constraint, in comparison to the unconstrained state. In contrast, the compressive residual stresses In the MoSi{sub 2} (as measured by X-ray diffraction) were lower in the constrained state relative to the unconstrained state. These results and a lack of residual stress balance indicate that the stress state in the braze is significantly different under the two joining conditions and the volume of the braze plays an important role in the development of the residual stresses. Push-out tests carried out on these joints gave higher joint strengths in the unconstrained as compared to the constrained condition. The results of this study have important implications on the selection of the appropriate joining process (use of constraint versus extra braze).

  17. A model for pressurized hydrogen induced thin film blisters

    NASA Astrophysics Data System (ADS)

    van den Bos, R. A. J. M.; Reshetniak, V.; Lee, C. J.; Benschop, J.; Bijkerk, F.

    2016-12-01

    We introduce a model for hydrogen induced blister formation in nanometer thick thin films. The model assumes that molecular hydrogen gets trapped under a circular blister cap causing it to deflect elastically outward until a stable blister is formed. In the first part, the energy balance required for a stable blister is calculated. From this model, the adhesion energy of the blister cap, the internal pressure, and the critical H-dose for blister formation can be calculated. In the second part, the flux balance required for a blister to grow to a stable size is calculated. The model is applied to blisters formed in a Mo/Si multilayer after being exposed to hydrogen ions. From the model, the adhesion energy of the Mo/Si blister cap was calculated to be around 1.05 J/m2 with internal pressures in the range of 175-280 MPa. Based on the model, a minimum ion dose for the onset of blister formation was calculated to be d = 4.2 × 1018 ions/cm2. From the flux balance equations, the diffusion constant for the Mo/Si blister cap was estimated to be DH2=(10 ±1 )×10-18 cm2/s .

  18. Stacking faults on (001) in transition-metal disilicides with the C11{sub b} structure

    SciTech Connect

    Ito, K.; Nakamoto, T.; Inui, H.; Yamaguchi, M.

    1997-12-31

    Stacking faults on (001) in MoSi{sub 2} and WSi{sub 2} with the C11{sub b} structure have been characterized by transmission electron microscopy (TEM), using their single crystals grown by the floating-zone method. Although WSi{sub 2} contains a high density of stacking faults, only several faults are observed in MoSi{sub 2}. For both crystals, (001) faults are characterized to be of the Frank-type in which two successive (001) Si layers are removed from the lattice, giving rise to a displacement vector parallel to [001]. When the displacement vector of faults is expressed in the form of R = 1/n[001], however, their n values are slightly deviated from the exact value of 3, because of dilatation of the lattice in the direction perpendicular to the fault, which is caused by the repulsive interaction between Mo (W) layers above and below the fault. Matching of experimental high-resolution TEM images with calculated ones indicates n values to be 3.12 {+-} 0.10 and 3.34 {+-} 0.10 for MoSi{sub 2} and WSi{sub 2}, respectively.

  19. Connecting structural, mechanical and tribological characteristics of Al alloyed nanocrystalline molybdenum silicide coatings

    NASA Astrophysics Data System (ADS)

    Xu, Jiang; Mao, XiangZhen; Xie, Zong-Han; Munroe, Paul

    2013-02-01

    In this study, novel nanocrystalline molybdenum silicide coatings with differing Al contents were deposited on a commercial titanium substrate using a double-cathode glow discharge apparatus. Their microstructures were characterized by x-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy. These coatings mainly consisted of MoSi2 and Mo5Si3 phases; the ratio of Mo5Si3 to MoSi2 gradually increased from the surface towards the interior of coatings, forming a graded structure. With the increase in Al content, the hardness and elastic modulus of the coatings slightly decreased, but the ratios of H/E and 1/E2H, as well as damage tolerance, increased. Furthermore, these newly developed coatings showed excellent wear resistance; their specific wear rates were not only considerably lower than that of the monolithic MoSi2 coating, but also decreased with increasing Al content. The plan and cross-sectional views of the worn surfaces and wear debris were analysed using SEM and energy dispersive x-ray spectroscopy. The relationships between coating structure, mechanical property and wear mechanism were then clarified, which will help in designing hard, tough and wear-resistant coatings for applications involving severe loading conditions.

  20. Nonlinear continuum growth model of multiscale reliefs as applied to rigorous analysis of multilayer short-wave scattering intensity. I. Gratings

    PubMed Central

    Goray, Leonid; Lubov, Maxim

    2013-01-01

    It is shown that taking into proper account certain terms in the nonlinear continuum equation of thin-film growth makes it applicable to the simulation of the surface of multilayer gratings with large boundary profile heights and/or gradient jumps. The proposed model describes smoothing and displacement of Mo/Si and Al/Zr boundaries of gratings grown on Si substrates with a blazed groove profile by magnetron sputtering and ion-beam deposition. Computer simulation of the growth of multilayer Mo/Si and Al/Zr gratings has been conducted. Absolute diffraction efficiencies of Mo/Si and Al/Zr gratings in the extreme UV range have been found within the framework of boundary integral equations applied to the calculated boundary profiles. It has been demonstrated that the integrated approach to the calculation of boundary profiles and of the intensity of short-wave scattering by multilayer gratings developed here opens up a way to perform studies comparable in accuracy to measurements with synchrotron radiation, at least for known materials and growth techniques. PMID:24046500

  1. Kinetic analysis of the combustion synthesis of molybdenum and titanium silicides

    NASA Astrophysics Data System (ADS)

    Wang, Lily L.; Munir, Z. A.

    1995-05-01

    The temperature profiles associated with the passage of self-propagating combustion waves during the synthesis of MoSi2 and Ti5Si3 were determined. From these profiles, kinetic analyses of the combustion synthesis process for these two silicides were made. The synthesis is associated with high heating rates: 1.3 × 104 and 4.9 × 104 K·s-1 for MoSi2 and Ti5Si3, respectively. The width of the combustion zone was determined as 1.3 and 1.8 mm for the silicides of Mo and Ti, respectively. The degree of conversion, η, and its spatial distribution and the conversion rate, ∂η/∂t, were determined. However, because of the inherent characteristics of wave propagation in MoSi2, only in the case of Ti5Si3 could the activation energy be calculated. An average value of 190 kJ µ mol-1 was determined for titanium suicide.

  2. Investigation of plasma-induced erosion of multilayer condenser optics

    NASA Astrophysics Data System (ADS)

    Anderson, Richard J.; Buchenauer, Dean A.; Williams, K. A.; Clift, W. M.; Klebanoff, L. E.; Edwards, N. V.; Wood, O. R., II; Wurm, S.

    2005-05-01

    Experiments are presented that investigate the mechanistic cause of multilayer erosion observed from condenser optics exposed to EUV laser-produced plasma (LPP) sources. Using a Xe filament jet source excited with Nd-YAG laser radiation (300 mJ/pulse), measurements were made of material erosion from Au, Mo, Si and C using coated quartz microbalances located 127 mm from the plasma. The observed erosion rates were as follows: Au=99nm/106 shots, Mo= 26nm/106 shots, Si=19nm/106 shots, and C=6nm/106 shots. The relative ratio Au:Mo:Si:C of erosion rates observed experimentally, 16:4:3:1 compares favorably with that predicted from an atomic sputtering model assuming 20 kV Xe ions, 16:6:4:1. The relative agreement indicates that Xe-substrate sputtering is largely responsible for the erosion of Mo/Si multilayers on condenser optics that directly face the plasma. Time-of-flight Faraday cup measurements reveal the emission of high energy Xe ions from the Xe-filament jet plasma. The erosion rate does not depend on the repetition rate of the laser, suggesting a thermal mechanism is not operative. The Xe-filament jet erosion is ~20x that observed from a Xe spray jet. Since the long-lived (millisecond time scale) plasma emanating from these two sources are the same to within ~30%, sputtering from this long-lived plasma can be ruled out as an erosion agent.

  3. Laser mask repair system LM700A

    NASA Astrophysics Data System (ADS)

    Ueda, Atsushi; Yoshino, Yoichi; Morishige, Yukio; Watanabe, Syuichi; Kyusho, Yukio; Haneda, Tsutoma; Ohmiya, Makoto

    2001-09-01

    High throughput laser mask repair system satisfying the accuracy demanded for 0.5micrometers pattern rule reticles has been newly developed. The named Laser Mask Repair LM700A has the following versatile features: *Opaque defect repair capability of 0.5micrometers L&S patterns with high repair accuracy of 45nm (3(sigma) ) *Low Quartz damage and high transmission at the repair site, especially for MoSi KrF-HT mask, and applicable to MoSi ArF-HT mask, by newly developed pico-second solid state UV pulse laser *0.1micrometers defect detectability by high resolution UV Optics *Through pellicle repair capability by newly developed long working distance UV objective lens *Auto-edge positioning function for various patterns By utilizing a pico-second UV pulse laser, very high quality laser zapping can be obtained. This paper presents the configuration and the evaluated results for mask repair performance in MoSi KrF-HT and ArF-HT masks.

  4. Process window enhancement for 45-nm node using alterable transmission phase-shifting materials

    NASA Astrophysics Data System (ADS)

    Becker, Hans; Renno, Markus; Hess, Guenter; Buttgereit, Ute; Koepernik, Corinna; Nedelmann, Lorenz; Irmscher, Mathias; Birkner, Robert; Zibold, Axel; Scheruebl, Thomas

    2006-10-01

    A case study was carried out investigating the influence of different transmission and phase shift materials on lithographic performance at 45 nm node. The bilayer approach for embedded attenuated Phase Shift Masks (EAPSM) offers the advantages to adjust phase shift and transmission independently. The transmission of Ta/SiO2 can be tuned up to 40% depending on the required application. Three different PSM blank types with the stacks Ta/SiO2-6%, Ta/SiO2-30% and Ta/SiON-30% have been manufactured and characterized. Afterwards, an identical line pattern, consisting of different feature sizes and duty cycles, has been patterned in each of the three PSM types as well as in the MoSi-6% for reference. Using the AIMS TM 45-193i tool we have evaluated the lithographic performance of the four PSM in terms of contrast and process latitude using unpolarized and TE polarized illumination. The case study showed that the process window for Ta/SiO2-6% is comparable to standard MoSi-6%. For dense line application a 6% EAPSM is preferable. The Ta/SiO2-30% EAPSM provides a significantly larger process window for higher duty cycles compared to MoSi-6%. This means a 50% increase in depth of focus (DOF) at 10% exposure latitude (EL). Therefore for logic application with higher duty cycles a EAPSM material with 30% transmission is preferable.

  5. Effects of variable dietary sitostanol concentrations on plasma lipid profile and phytosterol metabolism in hamsters.

    PubMed

    Ntanios, F Y; Jones, P J

    1998-02-23

    To examine how variable sitostanol (SI) levels in phytosterol-supplemented diets influence plasma and hepatic lipid concentrations, fifty hamsters were divided into five groups and fed semipurified diets containing 0.25% (w/w) cholesterol for 45 days ad libitum. Four groups were fed this diet with 1% (w/w) phytosterol mixtures which contained 0.01% (w/w) SI derived from soybean, 0.2% (w/w) SI derived from tall oil, 0.2% (w/w) synthetic SI mixture (SIM) and 1% (w/w) pure SI, respectively. A control group did not receive phytosterols. Dietary SI supplementation at 1% (w/w) decreased total and non-apolipoprotein-A cholesterol levels in plasma by 34% (P=0.001) and 55% (P=0.04), respectively, whereas mean plasma total cholesterol level in the 0.2% (w/w) SI group was 23% (P=0.001) lower than that of the control group. Conversely, plasma lipid profile in hamsters fed 1 or 0.2% (w/w) SI did not differ from the 0.01% (w/w) SI group. Liver weights were 15 and 20% (P=0.012) higher in the control group compared with those fed 0.01% and 1% (w/w) SI, respectively, while the hepatic cholesterol content in the control group was greater (P<0.0001) than that of all other groups. Plasma campesterol levels were higher (P=0.04) in the 0.01% and 0.2% (w/w) SI fed groups than in the control, 0.2% (w/w) SIM and 1% (w/w) SI groups. Hepatic sitosterol content was elevated (P=0.002) in the SIM fed group compared to other groups. We conclude that dietary SI effect is proportional to its concentration in phytosterol mixtures and in the diet. Dietary SI lowered plasma cholesterol levels at concentrations higher than 0.2% (w/w) in hamsters. (c) 1998 Elsevier Science B.V.

  6. Molybdenum Disilicide Oxidation Kinetics in High Temperature Steam

    SciTech Connect

    Wood, Elizabeth Sooby; Parker, Stephen Scott; Nelson, Andrew Thomas

    2016-09-07

    The Fuel Cycle Research and Development program’s Advanced Fuels Campaign is currently supporting a range of experimental efforts aimed at the development and qualification of ‘accident tolerant’ nuclear fuel forms. One route to enhance the accident tolerance of nuclear fuel is to replace the zirconium alloy cladding, which is prone to rapid oxidation in steam at elevated temperatures, with a more oxidation-resistant cladding. Several cladding replacement solutions have been envisaged. The cladding can be completely replaced with a more oxidation resistant alloy, a layered approach can be used to optimize the strength, creep resistance, and oxidation tolerance of various materials, or the existing zirconium alloy cladding can be coated with a more oxidation-resistant material. Molybdenum is one candidate cladding material favored due to its high temperature creep resistance. However, it performs poorly under autoclave testing and suffers degradation under high temperature steam oxidation exposure. Development of composite cladding architectures consisting of a molybdenum core shielded by a molybdenum disilicide (MoSi2) coating is hypothesized to improve the performance of a Mo-based cladding system. MoSi2 was identified based on its high temperature oxidation resistance in O2 atmospheres (e.g. air and “wet air”). However, its behavior in H2O is less known. This report presents thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and x-ray diffraction (XRD) results for MoSi2 exposed to 670-1498 K water vapor. Synthetic air (80-20%, Ar-O2) exposures were also performed, and those results are presented here for a comparative analysis. It was determined that MoSi2 displays drastically different oxidation behavior in water vapor than in dry air. In the 670-1498 K temperature range, four distinct behaviors are observed. Parabolic oxidation is exhibited in only 670

  7. Stress evolution in molybdenum/silicon multilayer mirrors for extreme ultraviolet lithography

    NASA Astrophysics Data System (ADS)

    Freitag, James Mac

    The continued shrinking of microelectronic device size necessitates advances in lithography, including possibly using extreme ultraviolet (EUV) light. The Mo/Si multilayer system is a promising candidate for reflective optics at a wavelength of roughly 135 A. However, these multilayers manifest high compressive stresses of approximately -350 MPa, which cause unacceptable distortion of the optical element. The goal of this project was to develop fundamental understanding of the origins of stress during growth of Mo/Si multilayers. A 40-bilayer structure deposited by DC-magnetron sputtering yielded a peak reflectivity of 65.7% at a wavelength of 136 A. We collected the stress data during deposition by in situ substrate curvature measurements using a multiple parallel laser beam technique. We measured large tensile and compressive curvature transients during initial growth of Mo on Si and Si on Mo. However, by sputtering with Kr rather than conventional Ar, it is possible to suppress the compressive transient upon Si deposition and thereby redress the compressive stress. Evidence implies that intermixing and alloying at the Mo-Si interfaces by asymmetric Si diffusion cause the transients. Indeed, Mo/Si multilayers sputtered with Kr exhibit less intermixing and high EUV reflectivity. However, the roughness of the multilayer may limit reflectivity and we therefore compare the roughness of Kr- and Ar-sputtered multilayers. Roughness, which leads to nonspecular scattering is problematic for EUV imaging systems because it decreases the useful throughput of a lithography system. We used x-ray diffraction to characterize the evolution of roughness with increasing number of bilayers in Mo/Si multilayers sputtered by Ar and Kr. By fitting a self-affine model of roughness to the diffuse spectra, we extracted the roughness and in-plane correlation lengths. We find that the lateral length scale of the roughness increases with the number of bilayers; however, the magnitude of the

  8. Advances in the reduction and compensation of film stress in high-reflectance multilayer coatings for extreme ultraviolet lithography applications

    SciTech Connect

    Mirkarimi, P.B., LLNL

    1998-02-20

    Due to the stringent surface figure requirements for the multilayer-coated optics in an extreme ultraviolet (EUV) projection lithography system, it is desirable to minimize deformation due to the multilayer film stress. However, the stress must be reduced or compensated without reducing EUV reflectivity, since the reflectivity has a strong impact on the throughput of a EUV lithography tool. In this work we identify and evaluate several leading techniques for stress reduction and compensation as applied to Mo/Si and Mo/Be multilayer films. The measured film stress for Mo/Si films with EUV reflectances near 67.4% at 13.4 nm is approximately - 420 MPa (compressive), while it is approximately +330 MPa (tensile) for Mo/Be films with EUV reflectances near 69.4% at 11.4 nm. Varying the Mo-to-Si ratio can be used to reduce the stress to near zero levels, but at a large loss in EUV reflectance (> 20%). The technique of varying the base pressure (impurity level) yielded a 10% decrease in stress with a 2% decrease in reflectance for our multilayers. Post-deposition annealing was performed and it was observed that while the cost in reflectance is relatively high (3.5%) to bring the stress to near zero levels (i.e., reduce by 1 00%), the stress can be reduced by 75% with only a 1.3% drop in reflectivity at annealing temperatures near 200{degrees}C. A study of annealing during Mo/Si deposition was also performed; however, no practical advantage was observed by heating during deposition. A new non-thermal (athermal) buffer-layer technique was developed to compensate for the effects of stress. Using this technique with amorphous silicon and Mo/Be buffer-layers it was possible to obtain Mo/Be and Mo/Si multilayer films with a near zero net film stress and less than a 1% loss in reflectivity. For example a Mo/Be film with 68.7% reflectivity at 11.4 nm and a Mo/Si film with 66.5% reflectivity at 13.3 nm were produced with net stress values less than 30 MPa.

  9. Proximity effect of iron-based superconductor in conventional s-wave superconducting thin films

    NASA Astrophysics Data System (ADS)

    Groll, Nick; Proslier, Thomas; Koshelev, Alex; Stantev, Valentin; Chung, Duck-Young

    2012-02-01

    The proximity effect has been proposed as a mechanism to unambiguously identify the possible s±-state in iron-based superconductors.ootnotetextA. E. Koshelev, V. Stanev, Europhysics Letters, Vol. 96, 27014 (2011) With a thin s-wave superconductor atop a s±-superconductor it is suggested that the s-wave order parameter will couple to the s±-gaps differently, inducing a correction to the s-wave density of states that can be probed using electron tunneling spectroscopy. In this talk, we will present recent results of the superconducting proximity effect in s-wave MoGe thin films sputtered on top of bulk superconducting Ba0.6K0.4Fe2As2 (Tc=35K) pnictide. Electron tunneling spectroscopy measurements were performed for several MoGe film thicknesses using a homemade point contact setup. Finally, results will also be presented for similar measurements using two conventional s-wave superconductors.

  10. Rat claustrum coordinates but does not integrate somatosensory and motor cortical information.

    PubMed

    Smith, Jared B; Radhakrishnan, Harsha; Alloway, Kevin D

    2012-06-20

    The function of the claustrum is a fundamental issue in neuroscience. Anatomical data indicate that the rat claustrum is part of an interhemispheric circuit that could be involved in the bilateral coordination of whisker movements. Given that whisking is a somesthetic-guided motor behavior, the goal of the current study was to elucidate the connections of the claustrum with respect to the whisker representations in the primary somatosensory (wSI) and motor (wMI) cortical areas. Anterograde tracer injections showed that wMI projects most densely to the claustrum in the contralateral hemisphere, whereas wSI does not project to the claustrum in either hemisphere. Injections of different retrograde tracers into wMI and wSI of the same animal revealed intermingled populations of labeled neurons in the claustrum, as well as many double-labeled neurons. This indicates that the same part of the claustrum projects to the whisker representations in both SI and MI. Finally, injections of different anterograde tracers in the wMI regions of both hemispheres were combined with a retrograde tracer injection in wSI, and this produced dense terminal labeling around retrogradely labeled neurons in the claustrum of both hemispheres. Although the rodent claustrum is probably involved in the interhemispheric coordination of the MI and SI whisker representations, it does not receive inputs from both of these cortical regions. Hence, the claustrum should not be universally regarded as an integrator of somesthetic and motor information.

  11. Multilayer diffraction at 104 keV

    NASA Technical Reports Server (NTRS)

    Krieger, Allen S.; Blake, Richard L.; Siddons, D. P.

    1993-01-01

    We have measured the diffraction peak of a W:Si synthetic multilayer reflector at 104 keV using the High Energy Bonse-Hart Camera at the X-17B hard X-ray wiggler beam line of the National Synchrotron Light Source at Brookhaven National Laboratory. The characteristics of the diffraction peak are described and compared to theory.

  12. Anomalous oxidation of intermetallics

    SciTech Connect

    Berztiss, D.A.; Pettit, F.S.; Meier, G.H.

    1995-07-01

    MoSi{sub 2}, {beta}-NiAl and TiAl with Cr additions are of interest for high temperature applications in oxidizing environments, where an oxide layer such as SiO{sub 2} or Al{sub 2}O{sub 3} should form to protect the base material. At elevated temperatures (600--1,700 C), a protective SiO{sub 2} layer forms on MoSi{sub 2}, while near 500 C pesting and/or accelerated oxidation could disintegrate the material to powder as Mo and Si oxidize to form a complex, thick, non-protective oxide layer. Use of {gamma}-TiAl is limited by poor oxidation resistance, whereby layered mixed oxides of TiO{sub 2} and Al{sub 2}O{sub 3} form. With the addition of Cr from 4 to 34 at%, results are varied: protective Al{sub 2}O{sub 3} formation, mixed oxide formation as with TiAl or more rapid oxidation than TiAl. NiAl is currently used as a diffusion coating on Ni-based superalloys and is being considered for use as a structural material itself because of its excellent oxidation resistance, i.e. forming {alpha}-alumina above 1,000 C. Recent work indicates that pure NiAl oxidized under low oxygen partial pressures in a contained atmosphere develops nonprotective oxide scales similar to accelerated oxidation of MoSi{sub 2}. This study explores the parameters defining protective behavior of these intermetallics and attempts to describe and explain anomalies at low temperatures and pressures.

  13. UV light with oxygen treatment of phase shift photoblank for phase and transmission control: applicable to MxSi(1-x)OyN(y-1)

    NASA Astrophysics Data System (ADS)

    Chovino, Christian M.; Dieu, Laurent

    2003-08-01

    A method based on UV in air environment to improve the stability of the material of the photoreticles throughout cleans repeated over is suggested in this work. A typical aggressive clean was performed on two different Embedded Shifter materials, 193nm Molybdenum-Silicon-Oxy-Nitride (MoSiON) and 193nm Multilayer Silicon Nitride-Titanium Nitride (SiN-TiN). The variation of phase and transmission of each reticle is reported with the number of cleans. Given the appropriate exposure the phase and the transmission of the treated materials were significantly improved. All treated EAPSMs could stand cleans repeated over.

  14. Circular multilayer zone plate for high-energy x-ray nano-imaging

    SciTech Connect

    Koyama, Takahisa; Takano, Hidekazu; Konishi, Shigeki; Tsuji, Takuya; Kagoshima, Yasushi; Takenaka, Hisataka; Ichimaru, Satoshi; Ohchi, Tadayuki

    2012-01-15

    A circular multilayer zone plate (MZP) was fabricated and its focusing performance was evaluated using 20-keV x-rays. MoSi{sub 2} and Si layers were alternately deposited by DC magnetron sputtering on a wire core; all the interfaces satisfied the Fresnel zone condition. The measured line spread function was converted to a point spread function by tomographic reconstruction. The results suggest that the MZP has the potential to realize the diffraction-limited resolving power, which is calculated to be 35 nm using the diffraction integral. Furthermore, scanning transmission microscopy using the MZP could resolve a 50-nm line-and-space pattern.

  15. High Temperature Silicides and Refractory Alloys Symposium Held in Boston, Massachusetts on November 29 -December 2, 1993. Volume 322

    DTIC Science & Technology

    1993-12-02

    A.B.Gokhale and G.J.Abbaschian in Binary Alloy Phase Diagrams, edited by T.B.Massalski (ASM International , Materials Park. OH 1986). 28. R.G.Castro...Bewecki, (ASM International , Pittsburgh, 1991) 273. 8. O.M. Jadaan, D.L. Shelleman, J.C, Conway, Jr.. J.J. Mecholsky, Jr., and R.E. Tressler. J. of Testing...The use of MoSi 2 as a structural material was thought to be limited to 1700 oC owing to the internal formation and agglomeration of Mo5 Si3, while

  16. Processing, phase equilibria and environmental degradation of molybdenum (silicom,aluminum)(2) intermetallic compound

    NASA Astrophysics Data System (ADS)

    Eason, Paul Duane

    The Mo(Si,Al)2 C40 compound was chosen for investigation as a possible high temperature structural material. To produce the C40 phase, several processing routes were explored with emphasis on obtaining microstructure/property relationships (i.e. control of grain size and minimization of secondary phases). To facilitate processing of single phase material, the phase equilibria of the Mo-Si-Al ternary system were reevaluated with respect to the phases adjacent to the C40 compound. An anomalous environmental degradation appeared to be the primary obstacle to further study of the compound and was investigated accordingly. Several processing routes were assessed for the production of dense, nearly single-phase Mo(Si,Al)2. Hot powder compaction was chosen as the method of sample production as is the case with many refractory silicide based materials. Therefore, variations in the processing techniques came from the choice of precursor materials and methods of powder production. Mechanical alloying, arc-melting and comminution, and blending of both elemental and compound powders were all employed to produce charges for hot uniaxial pressing. The final compacts were compared on the basis of density, grain size and presence of secondary phases. Establishment of a Mo-Si-Al ternary isothermal phase diagram at 1400°C was performed. Multiphase alloy compositions were selected to identify the phase boundaries of the C40, C54, T1 and Mo3Al8 phase fields, as well as to verify the existence of the C54 phase at 1400°C. The alloys were equilibrated by heat treatment and analyzed for phase identification and quantitative compositional information. The environmental degradation phenomenon was approached as a classical "pest" with an emphasis of study on grain boundary chemistry and atmospheric dependence of attack. Both Auger spectroscopy and electron microscopy revealed carbon-impurity-induced grain boundary segregation responsible for the embrittlement and material loss. Means of

  17. High temperature composites

    NASA Technical Reports Server (NTRS)

    Nathal, M. V.

    1995-01-01

    The purpose of this paper is to review the current state of the development of new composite materials for advanced aircraft engines. The advantages and disadvantages of Ti-base, NiAl-base, and MoSi2-base composites as replacements for today's Ni-base superalloys are discussed from the standpoint of key technical issues, current status, and future directions. Results describing progress in both improved understanding of the mechanisms of deformation and fracture, and improved material performance will be covered.

  18. Radiation Effect on Microstructural Stability of RERTR Fuel

    SciTech Connect

    J. Gan; D. D. Keiser, Jr.; B. D. Miller; T. R. Allen; D. M. Wachs

    2008-03-01

    Three depleted uranium alloys are successfully cast for the radiation stability studies of the fuel-cladding interaction product using proton irradiation. SEM analysis indicates the presence of the phases of interest: U(Si,Al)3, (U,Mo)(Si,Al)3 and a mixture of UMo2Al20, U6Mo4Al43, and UAl4. Irradiation with 2.6 MeV protons at 200ºC to the doses of 0.1, 1.0 and 3.0 dpa are carried out.

  19. Hydrides of intermetallic compounds with a H/M ratio greater than unity obtained at high hydrogen pressures

    SciTech Connect

    Semenenko, K.N.; Klyamkin, S.N.

    1993-11-01

    Novel hydride phases with H/M > 1 based on Zr{sub 2}Pd, Hf{sub 2}Pd, and Hf{sub 2}Cu (structures of the MoSi{sub 2} type) have been synthesized at high H{sub 2} pressures. The X-ray diffraction investigations of the resulting hydrides have been carried out. Some factors determining the maximum hydrogen content in the hydrides of intermetallic compounds are discussed. A model structure of the hydrides obtained is proposed, which assumes the possibility of direct H-H interactions when the interatomic distances are less than 1 {angstrom}.

  20. Multilayer based soft-x-ray polarimeter at MAX IV Laboratory

    NASA Astrophysics Data System (ADS)

    Grizolli, Walan; Laksman, Joakim; Hennies, Franz; Jensen, Brian Norsk; Nyholm, Ralf; Sankari, Rami

    2016-02-01

    A high precision five rotation-axes polarimeter using transmission multilayers as polarizers and reflection multilayers as analyzers has been designed and manufactured. To cover the extreme ultraviolet regime, Mo/Si, Cr/C, Sc/Cr, and W/B4C multilayers for transmission and reflection have also been designed and produced. The polarimeter mechanics is supported on a hexapod to simplify the alignment relative to photon beam. The instrument is designed so that it can be easily transferred between different beamlines.

  1. Low-cost method for producing extreme ultraviolet lithography optics

    DOEpatents

    Folta, James A.; Montcalm, Claude; Taylor, John S.; Spiller, Eberhard A.

    2003-11-21

    Spherical and non-spherical optical elements produced by standard optical figuring and polishing techniques are extremely expensive. Such surfaces can be cheaply produced by diamond turning; however, the roughness in the diamond turned surface prevent their use for EUV lithography. These ripples are smoothed with a coating of polyimide before applying a 60 period Mo/Si multilayer to reflect a wavelength of 134 .ANG. and have obtained peak reflectivities close to 63%. The savings in cost are about a factor of 100.

  2. Film Synthesis and New Superconductors.

    DTIC Science & Technology

    1983-05-01

    use of atomic and molecular beam codeposition techniques. The pseudo-binary system Nb-Mo-Si has been investigated. The A15 phase has been extended...Istituto di Fisica Teorica and ICTP, Trieste, Italy "Plasmons and Charge Density Waves in 2H-TaSe 2 " January 26, 1978 10. Dr. J. M. Rowell, Bell...Associate Universidade Estadual 4/1/79 - 6/30/79 de Campinas Instituto De Fisica BRASIL Bormann, Rudiger Visiting Research Associate Institute fur

  3. Composition of RF-sputtered refractory compounds determined by X-ray photoelectron spectroscopy

    NASA Technical Reports Server (NTRS)

    Wheeler, D. R.; Brainard, W. A.

    1978-01-01

    RF-sputtered coatings of CrB2, MoSi2, Mo2C, TiC, and MoS2 were examined by X-ray photoelectron spectroscopy (XPS). Data on stoichiometry, impurity content, and chemical bonding were obtained. The influences of sputtering target history, deposition time, RF power level, and substrate bias were studied. Significant deviations from stoichiometry and high oxide levels were related to target outgassing. The effect of substrate bias depended on the particular coating material studied.

  4. Extreme ultra-violet movie camera for imaging microsecond time scale magnetic reconnection

    SciTech Connect

    Chai, Kil-Byoung; Bellan, Paul M.

    2013-12-15

    An ultra-fast extreme ultra-violet (EUV) movie camera has been developed for imaging magnetic reconnection in the Caltech spheromak/astrophysical jet experiment. The camera consists of a broadband Mo:Si multilayer mirror, a fast decaying YAG:Ce scintillator, a visible light block, and a high-speed visible light CCD camera. The camera can capture EUV images as fast as 3.3 × 10{sup 6} frames per second with 0.5 cm spatial resolution. The spectral range is from 20 eV to 60 eV. EUV images reveal strong, transient, highly localized bursts of EUV radiation when magnetic reconnection occurs.

  5. Multilayer based soft-x-ray polarimeter at MAX IV Laboratory

    SciTech Connect

    Grizolli, Walan; Laksman, Joakim; Hennies, Franz; Jensen, Brian Norsk; Nyholm, Ralf; Sankari, Rami

    2016-02-15

    A high precision five rotation-axes polarimeter using transmission multilayers as polarizers and reflection multilayers as analyzers has been designed and manufactured. To cover the extreme ultraviolet regime, Mo/Si, Cr/C, Sc/Cr, and W/B{sub 4}C multilayers for transmission and reflection have also been designed and produced. The polarimeter mechanics is supported on a hexapod to simplify the alignment relative to photon beam. The instrument is designed so that it can be easily transferred between different beamlines.

  6. The effect of residual stress on performance of high temperature coatings

    NASA Technical Reports Server (NTRS)

    1972-01-01

    Techniques for measurement of residual stress in MoSi2 coatings and the determination of stress in coatings prepared by metalliding, pack and slurry processes are discussed. The stress level can be determined by stress induced deflections or by X-ray techniques. The deflection method is most direct. It is based on the fact that a thin substrate, coated on one side only, is usually curved at room temperature. The radius of curvature is easily measured and readily related to residual stress.

  7. Oxidation resistance of Ru-capped EUV multilayers

    SciTech Connect

    Bajt, S; Dai, Z; Nelson, E J; Wall, M A; Alameda, J; Nguyen, N; Baker, S; Robinson, J C; Taylor, J S; Clift, M; Aquila, A; Gullikson, E M; Edwards, N G

    2005-02-23

    Differently prepared Ru-capping layers, deposited on Mo/Si EUV multilayers, have been characterized using a suite of metrologies to establish their baseline structural, optical, and surface properties in as-deposited state. Same capping layer structures were tested for their thermal stability and oxidation resistance. Post-mortem characterization identified changes due to accelerated tests. The best performing Ru-capping layer structure was studied in detail with transmission electron microscopy to identify the grain microstructure and texture. This information is essential for modeling and performance optimization of EUVL multilayers.

  8. Multilayer Phase-Only Diffraction Gratings: Fabrication andApplication to EUV Optics

    SciTech Connect

    Salmassi, Farhad; Gullikson, Eric M.; Anderson, Erik H.; Naulleau, Patrick P.

    2007-05-01

    The use of phase-only diffractive devices has long played an important role in advanced optical systems in varying fields. Such devices include gratings, diffractive and holographic optical elements, diffractive lenses, and phase-shift masks for advanced lithography. Extending such devices to the increasingly important regime of extreme ultraviolet (EUV) wavelengths, however, is not trivial. Here, we present an effective fabrication and etch process enabling high-resolution patterning of Mo/Si multilayers for use in EUV phase devices, providing another method for fabrication of high numerical aperture diffractive devices or high-resolution EUV phase shift masks.

  9. Composition of RF-sputtered refractory compounds determined by X-ray photoelectron spectroscopy

    NASA Technical Reports Server (NTRS)

    Wheeler, D. R.; Brainard, W. A.

    1978-01-01

    RF-sputtered coatings of CrB2, MoSi2, Mo2C, TiC, and MoS2 were examined by X-ray photoelectron spectroscopy (XPS). Data on stoichiometry, impurity content, and chemical bonding were obtained. The influences of sputtering target history, deposition time, RF power level, and substrate bias were studied. Significant deviations from stoichiometry and high oxide levels were related to target outgassing. The effect of substrate bias depended on the particular coating material studied.

  10. In-line extreme ultraviolet polarizer with hybrid configuration.

    PubMed

    Yang, Minghong; Tong, Xinling; Sun, Yan; Jiang, Desheng; Zhou, Ciming; Zhang, Dongsheng

    2009-03-01

    A novel hybrid Au-multilayer-Au in-line extreme ultraviolet (EUV) optical polarizer is presented in this paper. Different from all-Mo/Si multilayer EUV polarizer, this polarizer is based on the concept that Au surfaces work as reflecting elements for in-line optics routine, while polarization effect is realized by polarizing multilayer. Simulation shows that the proposed polarizer with 80 degrees-70 degrees-80 degrees angle configuration has about 30% of transmission and 12 eV of bandwidth half maximum, which enables more throughput and broader bandwidth than the all-multilayer one.

  11. Oxidation resistance and microstructure of Ru-capped extreme ultraviolet lithography multilayers

    SciTech Connect

    Bajt, S; Dai, Z; Nelson, E J; Wall, M A; Alameda, J B; Nguyen, N; Baker, S L; Robinson, J C; Taylor, J S; Aquila, A; Edwards, N V

    2005-06-15

    The oxidation resistance of protective capping layers for extreme ultraviolet lithography (EUVL) multilayers depends on their microstructure. Differently prepared Ru-capping layers, deposited on Mo/Si EUVL multilayers, were investigated to establish their baseline structural, optical, and surface properties in as-deposited state. The same capping layer structures were then tested for their thermal stability and oxidation resistance. The best performing Ru-capping layer structure was analyzed in detail with transmission electron microscopy (TEM). As compared to other Ru capping layers preparations studied here it is the only one that shows grains with preferential orientation. This information is essential for modeling and performance optimization of EUVL multilayers.

  12. Toward the development of a soft x-ray reflection imaging microscope in the Schwarzschild configuration using a soft x-ray laser at 18. 2 nm

    SciTech Connect

    Dicicco, D.; Rosser, R. ); Kim, D.; Suckewer, S. . Plasma Physics Lab.)

    1991-12-01

    We present the recent results obtained from a soft X-ray reflection imaging microscope in the Schwarzschild configuration. The microscope demonstrated a spatial resolution of 0.7 {mu}m with a magnification of 16 at 18.2 nm. The soft X-ray laser at 18.2 nm was used as an X-ray source. Mo/Si multilayers were coated on the Schwarzschild optics and the normal incidence reflectivity at 18.2 nm per surface was measured to be {approximately} 20 %. 18 refs., 6 figs.

  13. Imaging of laser-produced plasmas at wavelengths of 130 A and 34 A using a microscope with multilayer-coated mirrors

    NASA Astrophysics Data System (ADS)

    Seely, John F.; Holland, G. E.; Giasson, J. V.

    1994-02-01

    Laser-produced plasmas were imaged using a microscope consisting of spherical primary and secondary mirrors that were coated with 40 Mo/Si periods and had peak reflectance of 60% at a wavelength of 130 angstroms. Niobium, gold, and aluminum targets were irradiated by up to 24 beams of the Omega laser at the Laboratory for Laser Energetics at the University of Rochester. Magnified images were recorded on Kodak 101 film, and the resolution was limited by the 10 micrometers emulsion grain size. A variety of plasma emission features were recorded with 5 micrometers (0.6 arcsec) resolution in the object plane.

  14. Broadband multilayer-coated normal incidence blazed grating with approximately 10% diffraction efficiency through the 13-16 nm wavelength region.

    PubMed

    Zhang, Lichao; Lin, Hui; Jin, Chunshui; Zhou, Hongjun; Huo, Tonglin

    2009-03-15

    Diffraction gratings used in extreme UV are typically coated with periodic multilayer thin films. These coatings have a small bandwidth, thus leading to a narrow usable spectral region of multilayer gratings. Well-designed aperiodic multilayer coatings could provide high reflectivity over a much broader wavelength region, so they could broaden the usable spectral region of multilayer gratings. We designed and deposited an aperiodic Mo/Si multilayer coating onto a blazed grating substrate. At an incidence angle of 10 degrees, the -2nd-order diffraction efficiency of the multilayer grating is approximately 10% through the wavelength range of 13-16 nm.

  15. Recent performance of the normal incident x-ray telescope with adaptive optics

    NASA Astrophysics Data System (ADS)

    Kitamoto, S.; Ishii, R.; Nukamori, S.; Imai, K.; Mochida, A.; Sato, S.; Ohgi, Y.; Yoshida, Y.; Hoshino, A.

    2016-09-01

    We report recent results of the performance measurement of our X-ray telescope with adaptive optics. The telescope is designed to use the 13.5nm EUV with the Mo/Si multilayers, making a normal incident optics. The primary mirror is 80mm in its diameter and the focal length of 2m. The deformable mirror is controlled by measuring a wave-front of an optical laser. Effects of a difference between the light paths from the reference and from an object are examined. The angular resolution is measured with optical light and we confirm almost diffraction limited resolution as well as its appropriate function as adaptive optics.

  16. Calibration of the Multi-Spectral Solar Telescope Array multilayer mirrors and XUV filters

    NASA Technical Reports Server (NTRS)

    Allen, Maxwell J.; Willis, Thomas D.; Kankelborg, Charles C.; O'Neal, Ray H.; Martinez-Galarce, Dennis S.; Deforest, Craig E.; Jackson, Lisa; Lindblom, Joakim; Walker, Arthur B. C., Jr.; Barbee, Troy W., Jr.

    1993-01-01

    The Multi-Spectral Solar Telescope Array (MSSTA), a rocket-borne solar observatory, was successfully flown in May, 1991, obtaining solar images in eight XUV and FUV bands with 12 compact multilayer telescopes. Extensive measurements have recently been carried out on the multilayer telescopes and thin film filters at the Stanford Synchrotron Radiation Laboratory. These measurements are the first high spectral resolution calibrations of the MSSTA instruments. Previous measurements and/or calculations of telescope throughputs have been confirmed with greater accuracy. Results are presented on Mo/Si multilayer bandpass changes with time and experimental potassium bromide and tellurium filters.

  17. Extreme ultra-violet movie camera for imaging microsecond time scale magnetic reconnection.

    PubMed

    Chai, Kil-Byoung; Bellan, Paul M

    2013-12-01

    An ultra-fast extreme ultra-violet (EUV) movie camera has been developed for imaging magnetic reconnection in the Caltech spheromak/astrophysical jet experiment. The camera consists of a broadband Mo:Si multilayer mirror, a fast decaying YAG:Ce scintillator, a visible light block, and a high-speed visible light CCD camera. The camera can capture EUV images as fast as 3.3 × 10(6) frames per second with 0.5 cm spatial resolution. The spectral range is from 20 eV to 60 eV. EUV images reveal strong, transient, highly localized bursts of EUV radiation when magnetic reconnection occurs.

  18. Extreme ultra-violet movie camera for imaging microsecond time scale magnetic reconnection

    NASA Astrophysics Data System (ADS)

    Chai, Kil-Byoung; Bellan, Paul M.

    2013-12-01

    An ultra-fast extreme ultra-violet (EUV) movie camera has been developed for imaging magnetic reconnection in the Caltech spheromak/astrophysical jet experiment. The camera consists of a broadband Mo:Si multilayer mirror, a fast decaying YAG:Ce scintillator, a visible light block, and a high-speed visible light CCD camera. The camera can capture EUV images as fast as 3.3 × 106 frames per second with 0.5 cm spatial resolution. The spectral range is from 20 eV to 60 eV. EUV images reveal strong, transient, highly localized bursts of EUV radiation when magnetic reconnection occurs.

  19. Effect of Silicon on Activity Coefficients of Platinum in Liquid Fe-Si, With Application to Core Formation

    NASA Technical Reports Server (NTRS)

    Righter, K.; Pando, K.; Danielson, L. R.; Humayun, M.

    2017-01-01

    Earth's core contains approximately 10% of a light element that is likely a combination of S, C, Si, and O, with Si possibly being the most abundant light element. Si dissolved into Fe liquids can have a large effect on the magnitude of the activity coefficient of siderophile elements (SE) in Fe liquids, and thus the partitioning behavior of those elements between core and mantle. The effect of Si can be small such as for Ni and Co, or large such as for Mo, Ge, Sb, As. The effect of Si on many siderophile elements is unknown yet could be an important, and as yet unquantified, influence on the core-mantle partitioning of SE. Here we report new experiments designed to quantify the effect of Si on the partitioning of Pt (with Re and Ru in progress or planned) between metal and silicate melt. The results will be applied to Earth, for which we have excellent constraints on the mantle Pt concentrations.

  20. Lorentzian crater in superconducting microwave resonators with inserted nanowires

    NASA Astrophysics Data System (ADS)

    Bezryadin, Alexey; Brenner, Matthew W.; Gopalakrishnan, Sarang; Ku, Jaseung; Shah, Nayana; Goldbart, Paul M.

    2011-03-01

    We report on observations of nonequilibrium pulsing states in microwave (i.e., GHz) coplanar waveguide(CPW) resonators consisting of superconducting MoGe strips interrupted by a trench and connected by one or more suspended superconducting nanowires. The Lorentzian resonance peak shows a ``crater'' when driven past the critical current of the nanowire, leading to a ``pulsing'' state. In the pulsing state, the supercurrent grows until it reaches the critical current, at which point all stored energy quickly dissipates through Joule heating. We develop a phenomenological model of resonator-nanowire systems, which explains the experimental data quantitatively. For the case of resonators comprising two parallel nanowires and subject to an external magnetic field, we find field-driven oscillations of the onset power for crater formation, as well as the occurrence of a new state, in which the periodic pulsing effect is such that only the weaker wire participates in the dissipation process.

  1. Effect of Silicon on Activity Coefficients of Siderophile Elements (P, Au, Pd, As, Ge, Sb, and In) in Liquid Fe, with Application to Core Formation

    NASA Technical Reports Server (NTRS)

    Righter, K.; Pando, K.; Danielson, L. R.; Humayun, M.; Righter, M.; Lapen, T.; Boujibar, A.

    2016-01-01

    Earth's core contains approximately 10 percent light elements that are likely a combination of S, C, Si, and O, with Si possibly being the most abundant. Si dissolved into Fe liquids can have a large effect on the magnitude of the activity coefficient of siderophile elements (SE) in Fe liquids, and thus the partitioning behavior of those elements between core and mantle. The effect of Si can be small such as for Ni and Co, or large such as for Mo, Ge, Sb, As. The effect of Si on many siderophile elements is unknown yet could be an important, and as yet unquantified, influence on the core-mantle partitioning of SE. Here we report new experiments designed to quantify the effect of Si on the partitioning of P, Au, Pd, and many other SE between metal and silicate melt. The results will be applied to Earth, for which we have excellent constraints on the mantle siderophile element concentrations.

  2. Ohmic contacts to GaAs for high-temperature device applications

    NASA Technical Reports Server (NTRS)

    Anderson, W. T., Jr.; Christou, A.; Giuliani, J. F.; Dietrich, H. B.

    1981-01-01

    Ohmic contacts to n-type GaAs were developed for high temperature device applications up to 300 C. Refractory metallizations were used with epitaxial Ge layers to form the contacts: TiW/Ge/GaAs, Ta/Ge/GaAs, Mo/Ge/GaAs, and Ni/Ge/GaAs. Contacts with high dose Si or Se ion implantation of the Ge/GaAs interface were also investigated. The contacts were fabricated on epitaxial GaAs layer grown on N+ or semi-insulating GaAs substrates. Ohmic contact was formed by both thermal annealing (at temperatures up to 700 C) and laser annealing (pulsed Ruby). Examination of the Ge/GaAs interface revealed Ge migration into GaAs to form an N+ doping layer. The specific contact resistances of specimens annealed by both methods are given.

  3. Effect of Silicon on Activity Coefficients of P, Bl, CD, SN, and AG in Liquid Fe-Si, and Implications for Differentiation and Core Formation

    NASA Technical Reports Server (NTRS)

    Righter, K.; Pando, K.; Ross, D. K.

    2017-01-01

    Cores of differentiated bodies (Earth, Mars, Mercury, Moon, Vesta) contain light elements such as S, C, Si, and O. We have previously measured small effects of Si on metal-silicate partitioning of Ni and Co [1,2], and larger effects for Mo, Ge, Sb, As [2]. The effect of Si on many siderophile elements could be an important, and as yet unquantified, influence on the core-mantle partitioning of SE. Here we report new experiments designed to quantify the effect of Si on the partitioning of Bi, Cd, Sn, Ag, and P between metal and silicate melt. The results will be applied to Earth, Mars, Mercury, Moon, and Vesta, for which we have excellent constraints on the mantle Bi, Cd, Sn, Ag, and P concentrations from mantle and/or basalt samples.

  4. 4-d magnetism: Electronic structure and magnetism of some Mo-based alloys

    NASA Astrophysics Data System (ADS)

    Liu, Yong; Bose, S. K.; Kudrnovský, J.

    2017-02-01

    We report results of a first-principles density-functional study of alloys of the 4 d -element Mo with group IV elements Si, Ge and Sn in zinc blende (ZB) and rock salt (RS) structures. The study was motivated by a similar study of ours based on the 4 d -element Tc, which showed the presence of half-metallic states with integer magnetic moment (1μB) per formula unit in TcX (X=C, Si, Ge) alloys. The calculated Curie temperatures for the ferromagnetic (FM) phases were low, around or less than 300 K. Searching for the possibility of 4 d -based alloys with higher Curie temperatures we have carried out the study involving the elements Mo, Ru and Rh. Among these the most promising case appears to be that involving the element Mo. Among the MoX (X=Si, Ge, Sn) alloys in ZB and RS structures, both MoGe and MoSn in ZB structures are found to possess an integer magnetic moment of 2μB per formula unit. ZB MoSn can be classified as a marginal/weak half-metal or a spin gapless semiconductor, while ZB MoGe would be best described as a gapless magnetic semiconductor. The calculated Curie temperatures are in the range 300-700 K. Considering the theoretical uncertainty in the band gaps due not only to the treatment of exchange and correlation effects, but density functional theory itself, these classifications may change somewhat, but both merit investigation from the viewpoint of potential spintronic application. Based on their higher Curie temperatures, Mo-based alloys would serve such purpose better than the previously reported Tc-based ones.

  5. Synthesis of a base-stabilized silanone-coordinated complex by oxygenation of a (silyl)(silylene)tungsten complex.

    PubMed

    Muraoka, Takako; Abe, Keisuke; Haga, Youhei; Nakamura, Tomoko; Ueno, Keiji

    2011-10-05

    Base-stabilized silanone complex Cp*(OC)(2)W(SiMe(3)){O═SiMes(2)(DMAP)} (2) was synthesized by the reaction of (silyl)(silylene)tungsten complex Cp*(OC)(2)W(SiMe(3))(═SiMes(2)) (1) with 1 equiv of pyridine-N-oxide (PNO) in the presence of 4-(dimethylamino)pyridine (DMAP). Further oxygenation of 2 with 3 equiv of PNO at 80 °C resulted in the formation of a W-O-Si-O-Si framework to give disiloxanoxy complex Cp*(O)(2)W{OSiMes(2)(OSiMe(3))} (3). Complex 3 was also obtained by the direct reaction of complex 1 with 4 equiv of PNO at 80 °C.

  6. Surface phenomena related to mirror degradation in extreme ultraviolet (EUV) lithography

    NASA Astrophysics Data System (ADS)

    Madey, Theodore E.; Faradzhev, Nadir S.; Yakshinskiy, Boris V.; Edwards, N. V.

    2006-12-01

    One of the most promising methods for next generation device manufacturing is extreme ultraviolet (EUV) lithography, which uses 13.5 nm wavelength radiation generated from freestanding plasma-based sources. The short wavelength of the incident illumination allows for a considerable decrease in printed feature size, but also creates a range of technological challenges not present for traditional optical lithography. Contamination and oxidation form on multilayer reflecting optics surfaces that not only reduce system throughput because of the associated reduction in EUV reflectivity, but also introduce wavefront aberrations that compromise the ability to print uniform features. Capping layers of ruthenium, films ˜2 nm thick, are found to extend the lifetime of Mo/Si multilayer mirrors used in EUV lithography applications. However, reflectivities of even the Ru-coated mirrors degrade in time during exposure to EUV radiation. Ruthenium surfaces are chemically reactive and are very effective as heterogeneous catalysts. In the present paper we summarize the thermal and radiation-induced surface chemistry of bare Ru exposed to gases; the emphasis is on H 2O vapor, a dominant background gas in vacuum processing chambers. Our goal is to provide insights into the fundamental physical processes that affect the reflectivity of Ru-coated Mo/Si multilayer mirrors exposed to EUV radiation. Our ultimate goal is to identify and recommend practices or antidotes that may extend mirror lifetimes.

  7. Chemically enhanced ion etching on refractory metal silicides

    SciTech Connect

    O'Brien, W.L.; Rhodin, T.N.; Rathbun, L.C.

    1988-05-01

    Mechanisms of chemically enhanced ion etching on TiSi/sub 2/ and MoSi/sub 2/ were studied using high-resolution (250 ns) direct time-of-flight (TOF) spectroscopy and steady-state surface techniques (Auger electron spectroscopy and x-ray photoelectron spectroscopy). Argon ion pulses (4 ..mu..s, 0.2 mA/cm/sup 2/) were used in combination with a high-pressure chlorine gas doser (1 x 10/sup -5/ Torr) to study ion etchant product distributions. Ion product TOF distributions were interpreted in terms of the collisional cascade model with corrections for ionization probability. Surface chemical and compositional changes were measured after etching the silicide surfaces. Differences in TOF distributions of the same species from different substrates (e.g., Si from Si, TiSi/sub 2/ and MoSi/sub 2/) are discussed on the basis of these chemical and compositional changes. Etching mechanisms for the silicides are discussed by comparison to the etching of the elemental surfaces.

  8. Service limitations for oxidation resistant intermetallic compounds

    SciTech Connect

    Smialek, J.L.; Nesbitt, J.A.; Brindley, W.J.; Brady, M.P.; Doychak, J.; Dickerson, R.M.; Hull, D.R.

    1995-07-01

    Oxidation resistant intermetallic compounds based on NiAl, TiAl, and MoSi{sub 2} are of interest for high temperature applications. Each system exhibits different life-limiting degradation modes due to oxidation. {beta}-NiAl forms protective {alpha}-Al{sub 2}O scales. Breakdown follows well-established diffusion controlled processes resulting in survival for thousands of hours. The effect of thermal cycling and spalling is well established. Ti{sub 3}Al and TiAl compounds form less protective mixed TiO{sub 2} and Al{sub 2}O{sub 3} scales. However at realistic use temperatures (600--800 C), scale growth rates are acceptably low. The critical factor is embrittlement due to interstitial oxygen diffusion over a matter of hours. Solutions based on alloy development and coatings have not been satisfactory. MoSi{sub 2} materials exhibit very low oxidation rates at very high temperatures. However, low temperature (500 C) pest oxidation can be a catastrophic transient effect. Material integrity is a key factor. Fracture occurs because of accelerated growth of non-protective mixed MoO{sub 2}-SiO{sub 2} scales in pores and microcracks.

  9. Preparation and thermal shock resistance of high emissivity molybdenum disilicide- aluminoborosilicate glass hybrid coating on fiber reinforced aerogel composite

    NASA Astrophysics Data System (ADS)

    Shao, Gaofeng; Lu, Yucao; Wu, Xiaodong; Wu, Jun; Cui, Sheng; Jiao, Jian; Shen, Xiaodong

    2017-09-01

    To develop a flexible reusable surface insulation for thermal protection system, MoSi2-aluminoborosilicate glass hybrid coatings have been prepared on Al2O3 fiber reinforced Al2O3-SiO2 aerogel composite by slurry dipping and rapid sintering method. The effect of MoSi2 content on radiative property and thermal shock behavior was investigated. The total emissivity values of all the coatings exceeded 0.85 in the wavelength of 0.8-2.5 μm. The M10 and M50 coatings were up to 0.9, which was due to the highest amorphous glass content of the M10 coating and the largest surface roughness of the M50 coating. The M30 coated composite showed the best thermal shock resistance with only 0.023% weight loss after 20 thermal shock cycles between 1473 K and room temperature, which was attributed to the similar thermal expansion coefficients between the coating and the substrate and the appropriate viscosity of aluminoborosilicate glass at 1473 K. The cracks resulted from CTE mismatch stress with different sizes formed and grew on the surface of M10, M40 and M50 coated samples, leading to the failure of the composites.

  10. Processing, Microstructure, and Properties of Multiphase Mo Silicide Alloys

    SciTech Connect

    Heatherly, L.; Liu, C.T.; Schneibel, J.H.

    1998-11-30

    Multiphase Mo silicide alloys containing T2 (Mo{sub 5}SiB{sub 2}), Mo{sub 3}Si and Mo phases where prepared by both melting and casting (M and C) and powder metallurgical (PM) processes. Glassy phases are observed in PM materials but not in M and C materials. Microstructural studies indicate that the primary phase is Mo-rich solid solution in alloys containing {le}(9.4Si+13.8B, at. %) and T2 in alloys with {ge}(9.8Si+14.6B). An eutectic composition is estimated to be close to Mo-9.6Si-14.2B. The mechanical properties of multiphase silicide alloys were determined by hardness, tensile and bending tests at room temperature. The multiphase alloy MSB-18 (Mo-9.4Si-13.8B) possesses a flexure strength distinctly higher than that of MoSi{sub 2} and other Mo{sub 5}Si{sub 3} silicide alloys containing no Mo particles. Also, MSB-18 is tougher than MoSi{sub 2} by a factor of 4.

  11. Resonant ultrasound spectroscopy: Elastic properties of some intermetallic compounds

    SciTech Connect

    Chu, F.; Thoma, D.J.; He, Y.; Maloy, S.A.; Mitchell, T.E.

    1996-09-01

    A novel nondestructive evaluation method, resonant ultrasound spectroscopy (RUS), is reviewed with an emphasis upon defining the elastic properties of intermetallic phases. The applications and advantages of RUS as compared to other conventional elastic constant measurement methods are explained. RUS has been employed to measure the elastic properties of single crystal and/or polycrystalline intermetallics, such as Laves phases (C15 HfV{sub 2} and NbCr{sub 2}), Nb-modified titanium aluminides, and transition metal disilicides (C11{sub b} MoSi{sub 2}, C40 NbSi{sub 2} and TaSi{sub 2}). For Laves phases, the elastic properties of HfV{sub 2}-based C15 phases show various anomalies and those of C15 NbCr{sub 2} do not. For Nb-modified titanium aluminides, the elastic properties of O-phase alloys are investigated as a function of alloying content. For transition metal disilicides, single crystal elastic constants of MoSi{sub 2}, NbSi{sub 2}, and TaSi{sub 2} are obtained and compared. Based on the experimentally determined elastic properties, the characteristics of interatomic bonding in these materials are examined and the possible impact of the elastic properties on mechanical behavior is discussed.

  12. Optical Elements: Effect of structural defects of aperiodic multilayer mirrors on the properties of reflected (sub)femtosecond pulses

    NASA Astrophysics Data System (ADS)

    Garakhin, S. A.; Meltchakov, E. N.; Polkovnikov, V. N.; Salashchenko, N. N.; Chkhalo, N. I.

    2017-05-01

    The effect of structural defects (for example, of interlayer roughness, layer thickness fluctuations and departures of Mo film density from the tabular one) on the amplitude and phase of the complex reflection coefficient as well as on the amplitude and duration of reflected pulses is numerically studied by the example of a model aperiodic Mo/Si multilayer mirror intended for the compression of a chirped pulse with a spectrum lying in a 50 - 80 eV photon energy range. The departures of Mo film density from the tabular values and film thickness fluctuations are shown to exert the strongest effect on the amplitude and duration of the reflected pulses. The interlayer roughness has a comparable effect on the amplitude of the reflection coefficient, but its effect on the duration of reflected pulses is weaker. Even small film thickness fluctuations may give rise to additional reflected pulses of high intensity, which are delayed in time relative to the principal pulse. The Mo-film density in a Mo/Si mirror is shown to vary from 0.77 to 0.97 (in units of the tabular value for massive molybdenum) as the film thickness varies from 1.5 to 5.5 nm. We discuss the key problems that have to be solved in the development of the fabrication technology of multilayer mirrors with desired characteristics.

  13. Subwavelength single layer absorption resonance antireflection coatings.

    PubMed

    Huber, S P; van de Kruijs, R W E; Yakshin, A E; Zoethout, E; Boller, K-J; Bijkerk, F

    2014-01-13

    We present theoretically derived design rules for an absorbing resonance antireflection coating for the spectral range of 100 - 400 nm, applied here on top of a molybdenum-silicon multilayer mirror (Mo/Si MLM) as commonly used in extreme ultraviolet lithography. The design rules for optimal suppression are found to be strongly dependent on the thickness and optical constants of the coating. For wavelengths below λ ∼ 230 nm, absorbing thin films can be used to generate an additional phase shift and complement the propagational phase shift, enabling full suppression already with film thicknesses far below the quarter-wave limit. Above λ ∼ 230 nm, minimal absorption (k < 0.2) is necessary for low reflectance and the minimum required layer thickness increases with increasing wavelength slowly converging towards the quarter-wave limit.As a proof of principle, SixCyNz thin films were deposited that exhibit optical constants close to the design rules for suppression around 285 nm. The thin films were deposited by electron beam co-deposition of silicon and carbon, with N+ ion implantation during growth and analyzed with variable angle spectroscopic ellipsometry to characterize the optical constants. We report a reduction of reflectance at λ = 285 nm, from 58% to 0.3% for a Mo/Si MLM coated with a 20 nm thin film of Si0.52C0.16N0.29.

  14. Spectral reflectance tuning of EUV mirrors for metrology applications

    NASA Astrophysics Data System (ADS)

    Yulin, Sergiy A.; Kuhlmann, Thomas; Feigl, Torsten; Kaiser, Norbert

    2003-06-01

    Mo/Si multilayer mirrors with as well an increased as a reduced bandwidth in their spectral and angular reflectance have been designed and deposited for the wavelength about 13.5 nm. For the broadband mirrors, a non-periodic multilayer design based on the thickness optimization of each layer by a stochastic method is compared to a desing that consists of 3 different monoperiodic stacks. In addition, narrowband multilayer mirrors with a significantly reduced bandwidth based on high order reflection have been designed and fabricated. A near-normal peak reflectivity of more than 20% and 30% were achieved for the broadband mirros in the wavelength range from 13 nm to 15 nm and the incidence angles from 0° to 20°, respectively. The decrease of FWHM for Mo/Si mirrors from 0.5 nm to 0.07 nm was shown for suggested narrowband design. Both the increase and the reduction of the reflection bandwidth are unavoidably connected with a decrease of peak reflectivity. Therefore, the application of such mirrors involves areas where a maximum peak reflectivity is not required, e.g. in EUV spectroscopy, radiation filtration and for the characterization of EUV sources. Furthermore, the use of such mirrors in combination with a broadband plasma source will result in a higher integral reflectivity.

  15. Solidification behavior during directed light fabrication

    SciTech Connect

    Thoma, D.J.; Lewis, G.K.; Nemec, R.B.

    1995-10-01

    Directed light fabrication (DLF) is a process that fuses gas delivered metal powders within a focal zone of a laser beam to produce fully dense, 3-dimensional metal components. A variety of materials have been processed with DLF, ranging from steels to tungsten, and including intermetallics such as NiAl and MoSi{sub 2}. To evaluate the processing parameters and resulting microstructures, solidification studies have been performed on defined alloy systems. For example, solidification cooling rates have been determined based upon secondary dendrite arm spacings in Fe-based alloys. In addition, eutectic spacings have been used to define growth velocities during solidification. Cooling rates vary from 10{sup 1}-10{sup 5} K s{sup {minus}1} and growth rates vary between 1--50 mm s{sup {minus}1}. As a result, process definition has been developed based upon the microstructural development during solidification. The materials explored were Ag-19Cu, Fe-24.8Ni, 316 stainless steel, Al-33Cu, W, MoSi{sub 2} and NiAl.

  16. Amorphous molybdenum silicon superconducting thin films

    SciTech Connect

    Bosworth, D. Sahonta, S.-L.; Barber, Z. H.; Hadfield, R. H.

    2015-08-15

    Amorphous superconductors have become attractive candidate materials for superconducting nanowire single-photon detectors due to their ease of growth, homogeneity and competitive superconducting properties. To date the majority of devices have been fabricated using W{sub x}Si{sub 1−x}, though other amorphous superconductors such as molybdenum silicide (Mo{sub x}Si{sub 1−x}) offer increased transition temperature. This study focuses on the properties of MoSi thin films grown by magnetron sputtering. We examine how the composition and growth conditions affect film properties. For 100 nm film thickness, we report that the superconducting transition temperature (Tc) reaches a maximum of 7.6 K at a composition of Mo{sub 83}Si{sub 17}. The transition temperature and amorphous character can be improved by cooling of the substrate during growth which inhibits formation of a crystalline phase. X-ray diffraction and transmission electron microscopy studies confirm the absence of long range order. We observe that for a range of 6 common substrates (silicon, thermally oxidized silicon, R- and C-plane sapphire, x-plane lithium niobate and quartz), there is no variation in superconducting transition temperature, making MoSi an excellent candidate material for SNSPDs.

  17. Novel EUV Mask Blank Defect Repair Developments

    SciTech Connect

    Hau-Riege, S; Barty, A; Mirkarimi, P

    2003-03-31

    The development of defect-free reticle blanks is an important challenge facing the commercialization of extreme ultraviolet lithography (EUVL). The basis of EUVL reticles are mask blanks consisting of a substrate and a reflective Mo/Si multilayer. Defects on the substrate or defects introduced during multilayer deposition can result in critical phase and amplitude defects. Amplitude- or phase-defect repair techniques are being developed with the goal to repair many of these defects. In this report, we discuss progress in two areas of defect repair: (1) We discuss the effect of the residual reflectance variation over the repair zone after amplitude-defect repair on the process window. This allows the determination of the maximum tolerable residual damage induced by amplitude defect repair. (2) We further performed a quantitative assessment of the yield improvement due to defect repair. We found that amplitude- and phase-defect repair have the potential to significantly improve mask blank yield. Our calculations further show that yield can be maximized by increasing the number of Mo/Si bilayers.

  18. Silicene-type Surface Reconstruction on C40 Hexagonal Silicides

    NASA Astrophysics Data System (ADS)

    Volders, Cameron; Reinke, Petra

    Silicene has emerged as the next two-dimensional material possessing a Dirac type electronic structure making it a prime candidate for integration in electronic devices. The study of silicene is relatively new and many aspects have yet to be fully understood. Here we present a scanning tunneling microscopy (STM) study of a Silicene-type surface reconstruction observed on nanometer scale hexagonal-MoSi2 crystallites. This surface reconstruction is specific to the C40 structure of h-MoSi2 and can initially be defined as a geometric silicene while the coupling between the silicene surface and the silicide bulk is under investigation. The lateral dimensions correspond to a superstructure where the silicene hexagons are slightly buckled and two of the six Si atoms are visible in the STM images creating a honeycomb pattern. The local electronic structure of the silicene is currently being studied with ST spectroscopy and the impact of confinement will be addressed. These results open an alternative route to Silicene growth by using surface reconstructions on metallic and semiconducting C40 silicide structures, which is promising for direct device integration on Si-platforms.

  19. Development of soft X-ray multilayer laminar-type plane gratings and varied-line-spacing spherical grating for flat-field spectrograph in the 1-8 keV region

    NASA Astrophysics Data System (ADS)

    Koike, Masato; Ishino, Masahiko; Imazono, Takashi; Sano, Kazuo; Sasai, Hiroyuki; Hatayama, Masatoshi; Takenaka, Hisataka; Heimann, Philip A.; Gullikson, Eric M.

    2009-08-01

    W/C and Co/SiO 2 multilayer laminar-type holographic plane gratings (groove density 1/σ = 1200 lines/mm) in the 1-8 keV region are developed. For the Co/SiO 2 grating the diffraction efficiencies of 0.41 and 0.47 at 4 and 6 keV, respectively, and for the W/C grating 0.38 at 8 keV are observed. Taking advantage of the outstanding high diffraction efficiencies into practical soft X-ray spectrographs a Mo/SiO 2 multilayer varied-line-spacing (VLS) laminar-type spherical grating (1/σ = 2400 lines/mm) is also developed for use with a flat field spectrograph in the region of 1.7 keV. For the Mo/SiO 2 multilayer grating the diffraction efficiencies of 0.05-0.20 at 0.9-1.8 keV are observed. The FWHMs of the measured line profiles of Hf-Mα 1(1644.6 eV), Si-Kα 1(1740.0 eV), and W-Mα 1 (1775.4 eV) are 13.7 eV, 8.0 eV, and 8.7 eV, respectively.

  20. Calculated efficiencies of three-material low stress coatings for diffractive x-ray transmission optics

    SciTech Connect

    Kubec, Adam Braun, Stefan; Gawlitza, Peter; Menzel, Maik; Leson, Andreas

    2016-07-27

    Diffractive X-ray optical elements made by thin film coating techniques such as multilayer Laue lenses (MLL) and multilayer zone plates (MZP) are promising approaches to achieve resolutions in hard X-ray microscopy applications of less than 10 nm. The challenge is to make a lens with a large numerical aperture on the one hand and a decent working distance on the other hand. One of the limiting factors with the coated structures is the internal stress in the films, which can lead to significant bending of the substrate and various types of unwanted diffraction effects. Several approaches have been discussed to overcome this challenge. One of these is a three-material combination such as Mo/MoSi{sub 2}/Si, where four single layers per period are deposited. Mo and Si represent the absorber and spacer in this case while MoSi{sub 2} forms a diffusion barrier; in addition the thicknesses of absorber and spacer are chosen to minimize residual stress of the overall coating. Here the diffraction efficiency as well as the profile of the beam in the focal plane are discussed in order to find a tradeoff between lowest residual stress and best diffraction properties.

  1. Microstructure of RERTR Du-Alloys Irradiated with Krypton Ions up to 100 dpa

    SciTech Connect

    J. Gan; D. D. Keiser, Jr.; D. M. Wachs; B. D. Miller; T. R. Allen; M. Kirk; J. Rest

    2011-04-01

    The radiation stability of the interaction product formed at the fuel–matrix interface of research reactor dispersion fuels, under fission-product bombardment, has a strong impact on fuel performance. Three depleted uranium alloys were cast that consisted of the following five phases to be investigated: U(Si, Al)3, (U, Mo)(Si, Al)3, UMo2Al20, U6Mo4Al43, and UAl4. Irradiation of transmission electron microscopy (TEM) disc samples with 500-keV Kr ions at 200 °C to doses up to 100 displacements per atom (dpa) were conducted using a 300-keV electron microscope equipped with an ion accelerator. TEM results show that the U(Si, Al)3 and UAl4 phases remain crystalline at 100 dpa without forming voids. The (U, Mo)(Si, Al)3 and UMo2Al20 phases become amorphous at 1 and 2 dpa, respectively, and show no evidence of voids at 100 dpa. The U6Mo4Al43 phase goes to amorphous at less than 1 dpa and reveals high density voids at 100 dpa.

  2. Development of an ultra high-precision x-ray telescope with an adaptive optics system

    NASA Astrophysics Data System (ADS)

    Kitamoto, Shunji; Takano, Haruko; Saitoh, Harue; Yamamoto, Norimasa; Kohmura, Takayoshi; Suga, Kazuharu; Sekiguchi, Hiroyuki

    2003-06-01

    We are developing an ultra high precision Soft X-ray telescope. The design of the telescope is a normal incident one for 13.5 nm band using Mo/Si multilayers. Two ideas are introduced. One is the optical measurement system in order to monitor the prevision of the optics system. The other is the adaptive optics system with a deformable mirror. Using an x-ray optical separation filter, we can always monitor the deformation of the optics by optical light. With this information, we can control the deformable mirror to compensate the system deformation as a closed loop system. We confirmed that the absolute precision of the wave front sensor was less than 3 nm rms. The preicison of the deformable mirror was roughly 5 nm rms. The shape of the primary mirror was an off-axis paraboloide with an effective diameter of 80mm. This primary mirror was coated by Mo/Si multilayers. The reflectivity of the primary mirror at 13.5 nm was rnaging from 30 to 50%. The x-ray optical separation filter was made from Zr with a thicknness of ~170nm. The transmission of the filter for low energy x-ray was measured and was roughly 50% at 13.5nm.

  3. Effect of amorphous C films deposited by RF magnetron sputtering on smoothing K9 glass substrate

    NASA Astrophysics Data System (ADS)

    Deng, Songwen; Qi, Hongji; Wei, Chaoyang; Yi, Kui; Fan, Zhengxiu; Shao, Jianda

    2009-12-01

    Soft X-ray multilayer reflectors must be deposited on super-smooth surface such as super-polished silicon wafers or glasses, which are complicate, time-consuming and expensive to produce. To overcome this shortage, C films deposited by RF magnetron sputtering were considered to smooth the K9 glass substrates' surface in the present paper. The structure of C films was systematically studied by XRD and Raman spectrum. The surface morphology and rms-roughness were obtained by AFM. Then, we calculated the impact of the C layers on the reflectivity curve of Mo/Si soft X-ray multilayer reflector around 13.5 nm. The C films exhibit typical amorphous state. With the increasing of power and thickness, the content of sp3 hybrid bonding decreases while the amount or size of well-organized graphite clusters increases. The surface rms-roughness decreases from 2.4 nm to 0.62 nm after smoothed by an 80 nm thick C layer deposited in 500 W, which is the smoothest C layer surface we have obtained. The calculation results show that the theoretical normal incidence reflectivity of Mo/Si multilayer at 13.5 nm increases from 7% to 63%.

  4. Electrical properties of TiN on gallium nitride grown using different deposition conditions and annealing

    SciTech Connect

    Li, Liuan; Kishi, Akinori; Shiraishi, Takayuki; Jiang, Ying; Wang, Qingpeng; Ao, Jin-Ping

    2014-03-15

    This study evaluates the thermal stability of different refractory metal nitrides used as Schottky electrodes on GaN. The results demonstrate that TiN, MoSiN, and MoN possess good rectification and adhesion strength, with barrier heights of 0.56, 0.54, and 0.36 eV, respectively. After thermal treatment at 850 °C for 1 min, the TiN and MoN electrodes still exhibit rectifying characteristics, while the MoSiN degrades to an ohmic-like contact. For further study, several TiN films are deposited using different N{sub 2}/Ar reactive/inert sputtering gas ratios, thereby varying the nitrogen content present in the sputtering gas. Ohmic-like contact is observed with the pure Ti contact film, and Schottky characteristics are observed with the samples possessing nitrogen in the film. The average Schottky barrier height is about 0.5 eV and remains virtually constant with varying nitrogen deposition content. After examining Raman spectra and x-ray photoelectron spectroscopy results, the increase in the film resistivity after thermal treatment is attributed to oxidation and/or nitridation. Films deposited with a medium (40% and 60%) nitrogen content show the best film quality and thermal stability.

  5. Extended process window using variable transmission PSM materials for 65-nm and 45-nm node

    NASA Astrophysics Data System (ADS)

    Koepernik, Corinna; Becker, Hans; Birkner, Robert; Buttgereit, Ute; Irmscher, Mathias; Nedelmann, Lorenz; Zibold, Axel

    2006-05-01

    The bilayer approach of embedded attenuated Phase Shift Masks (EAPSM), causing phase shift and transmission by two different materials offers advantages compared to the single layer solution. Three different PSM blank types with the stacks Ta/SiO II-6%, Ta/SiO II-30% and Ta/SiON-30% have been manufactured and characterized. Afterwards, identical line pattern of different feature sizes and duty cycles have been patterned in each of the three PSM types as well as in MoSi for reference. Using the AIMS TM fab 193i tool we have evaluated the lithographic performance of the four PSM in terms of contrast, normalized image slope (NILS), process latitude and process window. Improvements of up to 20% contrast, 10% NILS and 65% exposure latitude have been achieved for the Ta/SiO II 6% stack compared to the MoSi material with the same transmittance. In addition, the high transmission PSM clearly offers advantages in contrast, NILS and exposure latitude especially for smaller features.

  6. Monitoring of VX2 tumor growth in rabbit liver using T2-weighted and dynamic contrast-enhanced magnetic resonance imaging at 1.5T

    NASA Astrophysics Data System (ADS)

    Jao, Jo-Chi; Mac, Ka-Wai; Chang, Chiung-Yun; Wu, Yu-Chiuan; Hsiao, Chia-Chi; Chen, Po-Chou

    2017-03-01

    This study aimed to investigate the VX2 tumor growth in rabbit liver using T2-weighted imaging (T2WI) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Five New Zealand white (NZW) rabbits were implanted with VX2 cell suspension in liver. Afterwards, MRI was performed 7, 14, 21 and 28 days after tumor implantation. A 1.5T clinical MRI scanner was used to perform scans. After 3-plane localizer, T1 weighted imaging (T1WI), T2WI, and DCE-MRI using a three-dimensional gradient echo pulse sequence was performed. After 4 pre-contrast images were acquired, each rabbit was injected i.v. with 0.1 mmol/kg Dotarem. The total scan time after Dotarem administration was 30 minutes. All acquired images were analyzed using ImageJ software. Several regions of interest were selected from the rims of tumor, liver, and muscle. The enhancement ratio (ER) was calculated by dividing the MR signal after Dotarem injection to the MR signal before Dotarem injection. The maximum ER (ER_max) value of tumor for each rabbit was observed right after the Dotarem injection. The T2W MR signal intensities (T2W_SI) and the ER_max values obtained 7, 14, 21 and 28 days after tumor implantation were analyzed with a linear regression algorithm. Both T2W_SI and ER_max of tumors increased with time. The changes for T2W_SI and ER_max of tumors between 7 and 28 days after tumor implantation were 32.66% and 18.14%, respectively. T2W_SI is more sensitive than ER_max for monitoring the growth of VX2 tumor in a rabbit liver model.

  7. High-temperature stability of chemically vapor-deposited tungsten-silicon couples rapid thermal annealed in ammonia and argon

    SciTech Connect

    Broadbent, E.K.; Morgan, A.E.; Flanner, J.M.; Coulman, B.; Sadana, D.K.; Burrow, B.J.; Ellwanger, R.C.

    1988-12-15

    A rapid thermal anneal (RTA) in an NH/sub 3/ ambient has been found to increase the thermal stability of W films chemically vapor deposited (CVD) on Si. W films deposited onto single-crystal Si by low-pressure CVD were rapid thermal annealed at temperatures between 500 and 1100 /sup 0/C in NH/sub 3/ and Ar ambients. The reactions were studied using Rutherford backscattering spectrometry, x-ray diffraction, Auger electron spectroscopy, transmission electron microscopy, and four-point resistivity probe. High-temperature (greater than or equal to1000 /sup 0/C) RTA in Ar completely converted W into the low resistivity (31 ..mu cap omega.. cm) tetragonal WSi/sub 2/ phase. In contrast, after a prior 900 /sup 0/C RTA in NH/sub 3/, N inclusion within the W film and at the W/Si interface almost completely suppressed the W-Si reaction. Detailed examination, however, revealed some patches of WSi/sub 2/ formed at the interface accompanied by long tunnels extending into the substrate, and some crystalline precipitates in the substrate close to the interface. The associated interfacial contact resistance was only slightly altered by the 900 /sup 0/C NH/sub 3/ anneal. The NH/sub 3/-treated W film acted as a diffusion barrier in an Al/W/Si contact metallurgy up to at least 550 /sup 0/C, at which point some increase in contact resistance was measured.

  8. Amorphouslike chemical vapor deposited tungsten diffusion barrier for copper metallization and effects of nitrogen addition

    NASA Astrophysics Data System (ADS)

    Chang, Kow-Ming; Yeh, Ta-Hsun; Deng, I.-Chung; Shih, Chieh-Wen

    1997-08-01

    In this article, we propose an amorphouslike chemical vapor deposited tungsten (CVD-W) thin film as a diffusion barrier for copper metallization. Experimental results gave no evidence of interdiffusion and structural change for Cu/amorphouslike CVD-W/Si samples annealed up to 675 °C for 30 min in N2. At higher temperatures (700 °C), Cu penetration results in the formation of η''-Cu3Si precipitates at the CVD-W/Si interface. This is due to the crystallization of the amorphouslike CVD-W film above 650 °C, rendering the grain-boundary structure and, hence, fast pathways for Cu diffusion. The Cu/amorphouslike CVD-W/p+n diodes, thus, sustain large increases in reverse leakage current. In addition, the effects of nitrogen addition by using an in situ nitridation on the amorphouslike CVD-W film are also discussed. The effectiveness of the nitrided barrier is attributed to the blocking of the grain boundaries in the tungsten film by nitrogen atoms. This slows down Cu diffusion significantly. Physical and chemical analyses indicate that interfaces in the Cu/WNx/W/Si multilayer maintain their integrity while the annealing is carried out at 750 °C. Moreover, the reverse leakage current densities of Cu/WNx/W/p+n diodes remain at 10-7 A/cm2 after 725 °C annealing.

  9. The oxidation behavior of tungsten and germanium alloyed molybdenum disilicide coatings

    SciTech Connect

    Mueller, A.; Wang, Ge; Rapp, R.A.; Courtright, E.L.; Kircher, T.

    1991-11-01

    A two-step coating process was used to produce a (Mo,W)(Si,Ge){sub 2} coating on niobium. After exposure to high temperatures, a lower silicide layer forms underneath and is effective in arresting cracks. The oxidation weight-gain kinetics are parabolic following an initial transient period. Test coupons coated with (Mo,W)(Si,Ge){sub 2} passed 200 one-hour cycles at 1370{degree}C and 60 one-hour cycles at 1540{degree}C. These results, along with evidence of a thick protective glass layer, suggest that the germanium additions help cyclic oxidation resistance. The beneficial effects of the tungsten include the formation of microvoids, which provides a lower effective elastic modulus, and mechanical strengthening. No accelerated low temperature or ``pest`` oxidation was observed in the temperature range between 500--700{degree}C. Thus, a (Mo,W)(Si,Ge) multicomponent silicide coating offers significant promise for the protection of Nb-base alloys exposed to cyclic oxidizing environments over a broad range of temperatures.

  10. The oxidation behavior of tungsten and germanium alloyed molybdenum disilicide coatings

    SciTech Connect

    Mueller, A.; Wang, Ge; Rapp, R.A. . Dept. of Materials Science and Engineering); Courtright, E.L. ); Kircher, T. . Aerospace Materials Div.)

    1991-11-01

    A two-step coating process was used to produce a (Mo,W)(Si,Ge){sub 2} coating on niobium. After exposure to high temperatures, a lower silicide layer forms underneath and is effective in arresting cracks. The oxidation weight-gain kinetics are parabolic following an initial transient period. Test coupons coated with (Mo,W)(Si,Ge){sub 2} passed 200 one-hour cycles at 1370{degree}C and 60 one-hour cycles at 1540{degree}C. These results, along with evidence of a thick protective glass layer, suggest that the germanium additions help cyclic oxidation resistance. The beneficial effects of the tungsten include the formation of microvoids, which provides a lower effective elastic modulus, and mechanical strengthening. No accelerated low temperature or pest'' oxidation was observed in the temperature range between 500--700{degree}C. Thus, a (Mo,W)(Si,Ge) multicomponent silicide coating offers significant promise for the protection of Nb-base alloys exposed to cyclic oxidizing environments over a broad range of temperatures.

  11. Concepts for Smart Protective High-Temperature Coatings

    SciTech Connect

    Tortorelli, P.F.; Brady, M.P.; Wright, I.G.

    2003-04-24

    The need for environmental resistance is a critical material barrier to the operation of fossil systems with the improved energy efficiencies and emissions performance described by the goals of the Vision 21 concept of the U.S. Department of Energy's Office of Fossil Energy. All fossil fuel-derived processes contain reactive species and high-temperature degradation arising from reactions of solids with gases and condensible products often limits performance or materials lifetimes such that efficiency, emission, and/or economic targets or requirements are not realized. Therefore, historically, the development of materials for fossil-fuel combustion and conversion systems has been closely linked to corrosion studies of alloys and ceramics in appropriate environments. This project is somewhat different from such studies in that it focuses on the feasibility of new routes to controlling the critical chemical and mechanical phenomena that collectively form the basis for environmental protection in relevant fossil environments by exploring compositional and microstructural manipulations and cooperative phenomena that have not necessarily been examined in any detail to date. This can hopefully lead to concepts for ''smart'' coatings or materials that have the ability to sense and respond appropriately to a particular set or series of environmental conditions in order to provide high-temperature corrosion protection. The strategies being explored involve cooperative or in-place oxidation or sulfidation reactions of multiphase alloys.[1,2] The first material systems to be evaluated involve silicides as there is some evidence that such materials have enhanced resistance in oxidizing-sulfidizing and sulfidizing environments and in air/oxygen at very high temperatures.[3] In this regard, molybdenum silicides may prove to be of particular interest. Molybdenum is known to sulfidize fairly slowly[4] and there has been recent progress in developing Mo-Si-B systems with improved

  12. Field assisted sintering of ceramic materials

    NASA Astrophysics Data System (ADS)

    Stanciu, Lia Antoaneta

    2003-06-01

    The objective of this dissertation is to provide an understanding of the processing mechanisms of ceramic materials under an electrical field. Different parameters of the process, such as the electrical field, the heating rate, the holding time, and the precursor powder characteristics are studied in connection with their individual effect on the microstructural evolution and properties. The work reviews the fundamentals of sintering in the presence and in the absence of an electrical field, electrical conductivity in ceramics, precursor powder preparation methods for ceramic processing, as well as the relationship between the thermal properties and the neck formation in the first sintering stage. The ceramic materials that are chosen for the sintering studies are: Al2O3, TiO2, Al2TiO5 and MoSi2. Two type of precursors are used for the studies on Al 2TiO5: an amorphous sol-gel nanosize, and a crystalline coprecipitated micron size powder. Comparative studies on the effect of the heating rates in FAST on the conductive MoSi2 versus non-conductive Al2 O3 are also presented. The initial sintering stages of alpha-Al 2O3, which displays the maximum sintering activity under electrical field, are studied by a thermo-optical measurement method (TOM). The TOM method measures in-situ the thermal diffusivity of the powder. All the materials are characterized after sintering by XRD, FTIR, SEM, TEM, density and thermal diffusivity by TOM. The results show that the electrical field application enhances the kinetics of non-conductive oxide ceramics (Al2TiO5) formation by reaction sintering of the individual oxides. It also increases the rate of the neck formation during first sintering stage, and reduces porosity, thus improving the final density of non-conductive Al2O3. The sol-gel precursor powders with nanosize particles and a higher degree of homogeneity result in improved densification of the final consolidated part as compared to micron size or mechanically mixed precursors

  13. Experimental Fracture Measurements of Functionally Graded Materials

    NASA Astrophysics Data System (ADS)

    Carpenter, Ray Douglas

    The primary objective of this research was to extend established fracture toughness testing methods to a new class of engineering materials known as functionally graded materials (FGMs). Secondary goals were to compare experimental results to those predicted by finite element models and to provide fracture test results as feedback toward optimizing processing parameters for the in-house synthesis of a MoSi2/SiC FGM. Preliminary experiments were performed on commercially pure (CP) Ti and uniform axial tensile tests resulted in mechanical property data including yield strength, 268 MPa, ultimate tensile strength, 470 MPa and Young's modulus, 110 GPa. Results from 3-point bending fracture experiments on CP Ti demonstrated rising R-curve behavior and experimentally determined JQ fracture toughness values ranged between 153 N/mm and 254 N/mm. Similar experimental protocols were used for fracture experiments on a 7- layered Ti/TiB FGM material obtained from Cercom in Vista, California. A novel technique for pre-cracking in reverse 4-point bending was developed for this ductile/brittle FGM material. Fracture test results exhibited rising R-curve behavior and estimated JQ fracture toughness values ranged from 0.49 N/mm to 2.63 N/mm. A 5- layered MoSi2/SiC FGM was synthesized using spark plasma sintering (SPS). Samples of this material were fracture tested and the results again exhibited a rising R-curve with KIC fracture toughness values ranging from 2.7 MPa-m1/2 to 6.0 MPa-m1/2. Finite Element Models predicted rising R-curve behavior for both of the FGM materials tested. Model results were in close agreement for the brittle MoSi2/SiC FGM. For the relatively more ductile Ti/TiB material, results were in close agreement at short crack lengths but diverged at longer crack lengths because the models accounted for fracture toughening mechanisms at the crack tip but not those acting in the crack wake.

  14. High-temperature oxidation behavior of reaction-formed silicon carbide ceramics

    NASA Technical Reports Server (NTRS)

    Ogbuji, Linus U. J. T.; Singh, M.

    1995-01-01

    The oxidation behavior of reaction-formed silicon carbide (RFSC) ceramics was investigated in the temperature range of 1100 to 1400 C. The oxidation weight change was recorded by TGA; the oxidized materials were examined by light and electron microscopy, and the oxidation product by x-ray diffraction analysis (XRD). The materials exhibited initial weight loss, followed by passive weight gain (with enhanced parabolic rates, k(sub p)), and ending with a negative (logarithmic) deviation from the parabolic law. The weight loss arose from the oxidation of residual carbon, and the enhanced k(sub p) values from internal oxidation and the oxidation of residual silicon, while the logarithmic kinetics is thought to have resulted from crystallization of the oxide. The presence of a small amount of MoSi, in the RFSC material caused a further increase in the oxidation rate. The only solid oxidation product for all temperatures studied was silica.

  15. High throughput measurements of soft x-ray impurity emission using a multilayer mirror telescope

    SciTech Connect

    Stutman, D.; Tritz, K.; Delgado-Aparicio, L.; Finkenthal, M.; Suliman, G.; Roquemore, L.; Kaita, R.; Kugel, H.; Johnson, D.; Tamura, N.; Sato, K.; Sudo, S.; Tarrio, C.

    2006-10-15

    A 4 in. multilayer mirror telescope has been tested on National Spherical Torus Experiment (NSTX) for high throughput measurements of the beam excited soft x-ray impurity emission. The design is aimed at imaging low-k turbulent fluctuations in the plasma core. The test device used curved and planar Mo/Si mirrors to focus with {approx_equal}15% optical transmission and few angstrom bandwidths, the 135 A ring Ly{sub {alpha}} line from injected Li III atoms, or the n=2-4 line from intrinsic C VI ions. As test detectors we used 1 cm{sup 2} absolute extreme ultraviolet diodes, equipped with 400 kHz bandwidth, low noise preamplifiers. With the available view on NSTX the telescope successfully detected small impurity density fluctuations associated with 1/1 modes rotating at midradius, indicating that a high signal to noise ratio and cost effective core turbulence diagnostic is feasible based on this concept.

  16. Multilayer coatings of 10x projection for extreme-ultraviolet lithography

    SciTech Connect

    Folta, J A; Montcalm, C; Spiller, E; Wedowski, M

    1999-03-09

    Two new sets of projections optics for the prototype 10X reduction EUV lithography system were coated with Mo/Si multilayers. The coating thickness was graded across the optics by using shadow masks to ensure maximum throughput at all incidence angles in the camera. The overall deviation of the (normalized) wavelength response across the clear aperture of each mirror is below 0.01% RMS. However, the wavelength mismatch between two optics coated in different runs is up to 0.07 nm. Nevertheless, this is still within the allowed tolerances, and the predicted optical throughput loss in the camera due to such wavelength mismatch is about 4%. EUV reflectances of 63-65% were measured around 13.40 nm for the secondary optics, which is in good agreement with the expected reflectance based on the substrate finish as measured with AFM.

  17. In Situ Analysis of the Tribochemical Films Formed by SiC Sliding Against Mo in Partial Pressures of SO2, O2, and H2S Gases

    DTIC Science & Technology

    1996-02-01

    MoO3 or one of the substoichiometric MoOx ~2 ,x, 3! compounds—formed, although MoO2 is the first to crystal- lize from the chemisorbed state with...increasing thermal activity.31,32 We therefore designate the oxide to be MoOx . In SO2 , mixtures of MoS2 and MoOx would be expected. On the SiC wear scar...from Auger data. ~2<xɛ y , z51 or 2.! Gas Solid Mo SiC Tribofilm Transfer Tribofilm Transfer SO2 MoOx /MoS2 None SiOy/SiSz , C MoOx /MoS2 O2 MoOx None

  18. EUV light source with high brightness at 13.5 nm

    NASA Astrophysics Data System (ADS)

    Borisov, V. M.; Koshelev, K. N.; Prokof'ev, A. V.; Khadzhiyskiy, F. Yu; Khristoforov, O. B.

    2014-11-01

    The results of the studies on the development of a highbrightness radiation source in the extreme ultraviolet (EUV) range are presented. The source is intended for using in projection EUV lithography, EUV mask inspection, for the EUV metrology, etc. Novel approaches to creating a light source on the basis of Z-pinch in xenon allowed the maximal brightness [130 W(mm2 sr)-1] to be achieved in the vicinity of plasma for this type of radiation sources within the 2% spectral band centred at the wavelength of 13.5 nm that corresponds to the maximal reflection of multilayer Mo/Si mirrors. In this spectral band the radiation power achieves 190 W in the solid angle of 2π at a pulse repetition rate of 1.9 kHz and an electric power of 20 kW, injected into the discharge.

  19. Nitride-Based Materials for Flexible MEMS Tactile and Flow Sensors in Robotics.

    PubMed

    Abels, Claudio; Mastronardi, Vincenzo Mariano; Guido, Francesco; Dattoma, Tommaso; Qualtieri, Antonio; Megill, William M; De Vittorio, Massimo; Rizzi, Francesco

    2017-05-10

    The response to different force load ranges and actuation at low energies is of considerable interest for applications of compliant and flexible devices undergoing large deformations. We present a review of technological platforms based on nitride materials (aluminum nitride and silicon nitride) for the microfabrication of a class of flexible micro-electro-mechanical systems. The approach exploits the material stress differences among the constituent layers of nitride-based (AlN/Mo, Si x N y /Si and AlN/polyimide) mechanical elements in order to create microstructures, such as upwardly-bent cantilever beams and bowed circular membranes. Piezoresistive properties of nichrome strain gauges and direct piezoelectric properties of aluminum nitride can be exploited for mechanical strain/stress detection. Applications in flow and tactile sensing for robotics are described.

  20. Probing material conductivity in two-terminal devices by resistance difference

    NASA Astrophysics Data System (ADS)

    Lu, Yang; Chen, I.-Wei

    2017-08-01

    It is generally impossible in two-terminal devices to separate the resistance of the device material from the parasitic resistance of terminals, interfaces, and serial loads, yet such information is needed to understand device physics. Here, we present an exact resistance-difference analysis, for a library of similarly configured two-terminal devices with self-similar material responses to external perturbations (electric current, temperature, and magnetic field), to obtain the relative conductivity change Δσ/σ in the device material using device-resistance data only. An outstanding example is nanometallic Mo/Si3N4:Pt/Pt resistance memory, in which electrons in Si3N4:Pt—the device material—display entirely different physics from those in the Pt and Mo electrodes. Our method unraveled their individual Δσ/σ, which for Si3N4:Pt exhibits self-similarity over different resistance states and film thicknesses.

  1. A method for repairing amplitude defects in multilayer-coated EUV mask blanks

    SciTech Connect

    Barty, A; Hau-Riege, S; Stearns, D; Clift, M; Mirkarimi, P; Gullikson, E; Chapman, H; Sweeney, D

    2003-10-20

    EUV mask blanks are fabricated by depositing a reflective Mo/Si multilayer film onto super-polished substrates. Localized defects in this thin film coating can significantly perturb the reflected field and produce errors in the printed image. Ideally one would want to manufacture defect-free mask blanks; however, this may be very difficult to achieve in practice. One practical way to increase the yield of mask blanks is to be able to repair a significant number of the defects in the multilayer coating. In this paper we present a method for repairing defects that are near the top surface of the coating; we call these amplitude defects because they predominantly attenuate the amplitude of the reflected field. Although the discussion is targeted to the application of manufacturing masks for EUV lithography, the conclusions and results are also applicable to understanding the optical effects of multilayer erosion, including ion-induced multilayer erosion and condenser erosion in EUVL steppers.

  2. Nanoamorphous carbon-based photonic crystal infrared emitters

    DOEpatents

    Norwood, Robert A [Tucson, AZ; Skotheim, Terje [Tucson, AZ

    2011-12-13

    Provided is a tunable radiation emitting structure comprising: a nanoamorphous carbon structure having a plurality of relief features provided in a periodic spatial configuration, wherein the relief features are separated from each other by adjacent recessed features, and wherein the nanoamorphous carbon comprises a total of from 0 to 60 atomic percent of one or more dopants of the dopant group consisting of: transition metals, lanthanoids, electro-conductive carbides, silicides and nitrides. In one embodiment, a dopant is selected from the group consisting of: Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, La and other lanthanides, Hf, Ta, W, Rh, Os, Ir, Pt, Au, and Hg. In one embodiment, a dopant is selected from the group consisting of: electro-conductive carbides (like Mo.sub.2C), silicides (like MoSi.sub.2) and nitrides (like TiN).

  3. Metallic materials for structural applications beyond nickel-based superalloys

    NASA Astrophysics Data System (ADS)

    Heilmaier, M.; Krüger, M.; Saage, H.; Rösler, J.; Mukherji, D.; Glatzel, U.; Völkl, R.; Hüttner, R.; Eggeler, G.; Somsen, Ch.; Depka, T.; Christ, H.-J.; Gorr, B.; Burk, S.

    2009-07-01

    This paper reviews our current research activities on developing new multiphase metallic materials for structural applications with a temperature capability beyond 1,200°C. Two promising material systems have been chosen: first, alloys in the system Mo-Si-B which have demonstrated potential due to their high melting point of around 2,000°C and due to the formation of a protecting borosilicate glass layer on the surface at temperatures exceeding 900°C; and second, novel Co-Re-based alloys which have been chosen as a model system for complete miscibility between the elements cobalt and rhenium, offering the possibility of continuous increases of the melting point of the alloy through rhenium additions.

  4. Design of polarization-insensitive superconducting single photon detectors with high-index dielectrics

    NASA Astrophysics Data System (ADS)

    Redaelli, L.; Zwiller, V.; Monroy, E.; Gérard, J. M.

    2017-03-01

    In this paper, the design of superconducting-nanowire single-photon detectors which are insensitive to the polarization of the incident light is investigated. By using high-refractive-index dielectrics, the index mismatch between the nanowire and the surrounding media is reduced. This enhances the absorption of light with electric field vector perpendicular to the nanowire segments, which is generally hindered in these kind of detectors. Building on this principle and focusing on NbTiN nanowire devices, we present several easy-to-realize cavity architectures which allow high absorption efficiency (in excess of 90%) and polarization insensitivity simultaneously. Designs based on ultranarrow nanowires, for which the polarization sensitivity is much more marked, are also presented. Finally, we briefly discuss the specific advantages of this approach in the case of WSi or MoSi nanowires.

  5. Towards High Accuracy Reflectometry for Extreme-Ultraviolet Lithography.

    PubMed

    Tarrio, Charles; Grantham, Steven; Squires, Matthew B; Vest, Robert E; Lucatorto, Thomas B

    2003-01-01

    Currently the most demanding application of extreme ultraviolet optics is connected with the development of extreme ultraviolet lithography. Not only does each of the Mo/Si multilayer extreme-ultraviolet stepper mirrors require the highest attainable reflectivity at 13 nm (nearly 70 %), but the central wavelength of the reflectivity of these mirrors must be measured with a wavelength repeatability of 0.001 nm and the peak reflectivity of the reflective masks with a repeatability of 0.12 %. We report on two upgrades of our NIST/DARPA Reflectometry Facility that have given us the ability to achieve 0.1 % repeatability and 0.3 % absolute uncertainty in our reflectivity measurements. A third upgrade, a monochromator with thermal and mechanical stability for improved wavelength repeatability, is currently in the design phase.

  6. Solidification processing and phase transformations in ordered high temperature alloys. Final report, 30 March 1990-30 September 1992

    SciTech Connect

    Boettinger, W.J.; Bendersky, L.A.; Kattner, U.R.

    1993-01-20

    Useful high temperature alloys generally have microstructures consisting of more than one phase. Multiphase microstructures are necessary to develop acceptable toughness and creep strength in high temperature intermetallic alloy matrices. The optimum microstructures must be developed by a careful selection of processing path that includes both solidification and solid state heat treatment. Research has been conducted on the rapid solidification of selected intermetallic alloys and on the phase transformation paths that occur during cooling, primarily in the Ti-Al-Nb system. This report describes research performed in the Metallurgy Division at NIST under DARPA order 7469 between 1/1/89 and 12/31/92. Various research tasks were completed and the results have been published or have been submitted for publication.... Intermetallics, Ti-Al-Nb Alloys, Phase Diagrams, Phase Transformations, Ti-Al-Ta Alloys, MoSi2 Alloys.

  7. Epitaxial ternary RexMo1 - xSi2 thin films on Si(100)

    NASA Astrophysics Data System (ADS)

    Vantomme, André; Nicolet, Marc-A.; Long, Robert G.; Mahan, John E.

    1994-04-01

    Reactive deposition epitaxy was used to synthesize thin layers of RexMo1-xSi2 on Si(100). In the case of x=1, ReSi2 layers of excellent crystalline quality have been reported previously [J. E. Mahan, K. M. Geib, G. Y. Robinson, R. G. Long, Y. Xinghua, G. Bai, and M.-A. Nicolet, Appl. Phys. Lett. 56, 2439 (1990)]. In the case of x=0, however, virtually no alignment of the MoSi2 and the substrate is found, although this silicide is nearly isomorphic to ReSi2. For intermediate values of x, highly epitaxial ternary silicides are obtained, at least for a Mo fraction up to 1/3.

  8. The use of an electric field as a processing parameter in the combustion synthesis of ceramics and composites

    NASA Astrophysics Data System (ADS)

    Munir, Z. A.

    1996-08-01

    The imposition of an electric field is shown to activate self-propagating combustion reactions and thus makes possible the synthesis of a variety of ceramic and composite phases. Experimental observations and modeling studies indicated that activation is accomplished by the localized effect of the current. The relationship between wave propagation and the direction of the applied field was investigated. The synthesis of composites by field-activated combustion synthesis (FACS) was demonstrated. It was shown that the imposition of a field during the combustion synthesis of MoSi2 results in a decrease in the product particle size. The results suggest that the field can be used as a processing parameter in self-propagating combustion synthesis.

  9. The use of an electric field as a processing parameter in the combustion synthesis of ceramics and composites

    SciTech Connect

    Munir, Z.A.

    1996-08-01

    The imposition of an electric field is shown to activate self-propagating combustion reactions and thus makes possible the synthesis of a variety of ceramic and composite phases. Experimental observations and modeling studies indicated that activation is accomplished by the localized effect of the current. The relationship between wave propagation and the direction of the applied field was investigated. The synthesis of composites by field-activated combustion synthesis (FACS) was demonstrated. It was shown that the imposition of a field during the combustion synthesis of MoSi{sub 2} results in a decrease /in the product particle size. The results suggest that the field can be used as a processing parameter in self-propagating combustion synthesis.

  10. Substitution for chromium in 304 stainless steel. [effects on oxidation and corrosion resistance

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Barrett, C. A.

    1978-01-01

    An investigation was conducted to determine the effects of substituting less strategic elements for Cr on oxidation and corrosion resistance of AISI 304 stainless steel. Cyclic oxidation resistance was evaluated at 870 C. Corrosion resistance was determined by exposure of specimens to a boiling copper-rich solution of copper sulfate and sulfuric acid. Alloy substitutes for Cr included Al, Mn, Mo, Si, Ti, V, Y, and misch metal. A level of about 12% Cr was the minimum amount of Cr required for adequate oxidation and corrosion resistance in the modified composition 304 stainless steels. This represents a Cr saving of 33 percent. Two alloys containing 12% Cr plus 2% Al plus 2% Mo and 12% Cr plus 2.65% Si were identified which exhibited oxidation and corrosion resistance comparable to AISI 304 stainless steel.

  11. X-ray interferometer with an x-ray beam splitter

    NASA Astrophysics Data System (ADS)

    Kitamoto, S.; Sakata, K.; Murakami, H.; Yoshida, Y.; Seta, H.

    2012-09-01

    We report our examination of a new X-ray interferometer for observation of celestial objects and our recent work for preparation of laboratory experiments. The new X-ray interferometer is consisting of two at mirrors and one at beam splitter which are used as grazing incident optics. The aimed wave length is a O-K band or a C-K band. The beam splitter and the mirrors are fabricated by Mo/Si multilayer. We measured their atness and found that the measured atness is acceptable for the test experiment. A pin hole X-ray source is also preparing for a laboratory experiment in order to demonstrate a X-ray interference. We investigated a possible observation of accretion disks around BHs and nearby stars. With a reasonable size of the base line, we can measure their size and possibly we can obtain an evidence of a black hole shadow.

  12. Materials corrosion and protection from first principles

    NASA Astrophysics Data System (ADS)

    Johnson, Donald F.

    suggests that alloying Fe with Si can be an effective means to limit uptake of these elements into steel. Spallation of protective layers on jet engine turbine blades is a problem that arises during thermal cycling. An alternative thermal barrier coating system involving MoSi2 is considered and calculations predict strong adhesion at the MoSi2/Ni interface. The interfacial bonding structure reveals a mixture of metallic and covalent cross-interface bonds. The adhesion energy is similar across all three MoSi2 facets studied. Upon exposure to oxygen, this MoSi2 alloy will form a strongly adhered oxide scale, which in turn may strongly adhere the heat shield material (yttria-stabilized zirconia), thereby potentially extending the lifetime of the barrier coating. Lastly, the interaction of hydrogen isotopes (fusion fuel) with tungsten (a proposed fusion reactor wall material) is examined. Exothermic dissociative adsorption is predicted, along with endothermic absorption and dissolution. Surface-to-subsurface diffusion energy barriers for H incorporation into bulk W are large and the corresponding outward diffusion barriers are very small. In bulk W, deep energetic traps (trapping multiple H atoms) are predicted at vacancy defects. Thus, under high neutron fluxes that will produce vacancies in W, H are predicted to collect at these vacancies. In turn, locally high concentrations of H at such vacancies will enhance decohesion of bulk W, consistent with observed blistering under deuterium implantation. Limiting vacancy formation may be key to the survival of W as a fusion reactor wall material.

  13. Oxidation behavior of molybdenum silicides and their composites

    SciTech Connect

    Natesan, K.; Deevi, S. C.

    2000-04-03

    A key materials issue associated with the future of high-temperature structural silicides is the resistance of these materials to oxidation at low temperatures. Oxidation tests were conducted on Mo-based silicides over a wide temperature range to evaluate the effects of alloy composition and temperature on the protective scaling characteristics and testing regime for the materials. The study included Mo{sub 5}Si{sub 3} alloys that contained several concentrations of B. In addition, oxidation characteristics of MoSi{sub 2}-Si{sub 3}N{sub 4} composites that contained 20--80 vol.% Si{sub 3}N{sub 4} were evaluated at 500--1,400 C.

  14. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: First-Principles Calculations of Elastic and Thermal Properties of Molybdenum Disilicide

    NASA Astrophysics Data System (ADS)

    Zhu, Zun-Lue; Fu, Hong-Zhi; Sun, Jin-Feng; Liu, Yu-Fang; Shi, De-Heng; Xu, Guo-Liang

    2009-08-01

    The first-principles plane-wave pseudopotential method using the generalized gradient approximation within the framework of density functional theory is applied to anaylse the equilibrium lattice parameters, six independent elastic constants, bulk moduli, thermal expansions and heat capacities of MoSi2. The quasi-harmonic Debye model, using a set of total energy versus cell volume obtained with the plane-wave pseudopotential method, is applied to the study of the elastic properties, thermodynamic properties and vibrational effects. The calculated zero pressure elastic constants are in overall good agreement with the experimental data. The calculated heat capacities and the thermal expansions agree well with the observed values under ambient conditions and those calculated by others. The results show that the temperature has hardly any effect under high pressure.

  15. Mechanical properties and oxidation and corrosion resistance of reduced-chromium 304 stainless steel alloys

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Barrett, C. A.; Gyorgak, C. A.

    1979-01-01

    An experimental program was undertaken to identify effective substitutes for part of the Cr in 304 stainless steel as a method of conserving the strategic element Cr. Although special emphasis was placed on tensile properties, oxidation and corrosion resistance were also examined. Results indicate that over the temperature range of -196 C to 540 C the yield stress of experimental austenitic alloys with only 12 percent Cr compare favorably with the 18 percent Cr in 304 stainless steel. Oxidation resistance and in most cases corrosion resistance for the experimental alloys were comparable to the commercial alloy. Effective substitutes for Cr included Al, Mo, Si, Ti, and V, while Ni and Mn contents were increased to maintain an austenitic structure.

  16. Oxidation and corrosion behavior of modified-composition, low-chromium 304 stainless steel alloys

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Barrett, C. A.

    1977-01-01

    The effects of substituting less strategic elements than Cr on the oxidation and corrosion resistance of AISI 304 stainless steel were investigated. Cyclic oxidation resistance was evaluated at 870 C. Corrosion resistance was determined by exposure of specimens to a boiling copper-rich solution of copper sulfate and sulfuric acid. Alloy substitutes for Cr included Al, Mn, Mo, Si, Ti, V, Y, and misch metal. A level of about 12% Cr was the minimum amount of Cr required for adequate oxidation and corrosion resistance in the modified composition 304 stainless steels. This represents a Cr saving of at least 33%. Two alloys containing 12% Cr and 2% Al plus 2% Mo and 12% Cr plus 2.65% Si were identified as most promising for more detailed evaluation.

  17. EUV light source with high brightness at 13.5 nm

    SciTech Connect

    Borisov, V M; Prokof'ev, A V; Khristoforov, O B; Koshelev, K N; Khadzhiyskiy, F Yu

    2014-11-30

    The results of the studies on the development of a highbrightness radiation source in the extreme ultraviolet (EUV) range are presented. The source is intended for using in projection EUV lithography, EUV mask inspection, for the EUV metrology, etc. Novel approaches to creating a light source on the basis of Z-pinch in xenon allowed the maximal brightness [130 W(mm{sup 2} sr){sup -1}] to be achieved in the vicinity of plasma for this type of radiation sources within the 2% spectral band centred at the wavelength of 13.5 nm that corresponds to the maximal reflection of multilayer Mo/Si mirrors. In this spectral band the radiation power achieves 190 W in the solid angle of 2π at a pulse repetition rate of 1.9 kHz and an electric power of 20 kW, injected into the discharge. (laser applications and other topics in quantum electronics)

  18. Lithographic performance of a new "low-k" mask

    NASA Astrophysics Data System (ADS)

    Adachi, Takashi; Tani, Ayako; Fujimura, Yukihiro; Hayano, Katsuya; Morikawa, Yasutaka; Miyashita, Hiroyuki; Inazuki, Yukio; Kawai, Yoshio

    2016-05-01

    We have been researching new mask blank materials for the next generation lithography (NGL) and developed a new mask blank with low-k phase shifter [1] [2]. The low-k phase shifter consists of only Si and N. In our previous work, we reported the advantages of developed SiN phase shift mask (PSM) [2]. It showed high lithographic performance and high durability against ArF excimer laser as well as against cleaning. In this report, we further verified its high lithographic performance on several types of device pattern. The SiN PSM had high lithographic performance compared with conventional 6% MoSi PSM. Exposure latitude (EL) and mask enhancement factor (MEEF) were especially improved on originally designed Gate, Metal and Via patterns.

  19. High temperature nanostructured MoA1Si coatings on Alloys for ultrasupercritical coal-fired boilers: Final Technical Report DOE/SBIR/Phase I

    SciTech Connect

    Reddy, Ganta S.

    2012-11-21

    The goal of improving the efficiency of pulverized coal power plants has been pursued for decades. The need for greater fuel efficiency and reduced environmental impact is pushing utilities to Ultra Supercritical Steam Conditions (USC) of 760°C and 35 MPa. USC plants can operate at energy efficiencies in excess of 55%, while the conventional boilers are operating at 538°C and 17 MPa with an efficiency of 36 to 39%. Each percentage increase in energy efficiency gives rise to about an effective 2% reduction in CO2 and SO2 emissions. However USC boiler component life is limited by air oxidation, steam oxidation and erosion. Improving this life with an adherent MoSiAl nanostructure coating has been the focus of this research during the Phase I.

  20. Stability of EUV multilayer coatings to low energy alpha particles bombardment.

    PubMed

    Nardello, M; Zuppella, Paola; Polito, V; Corso, Alain Jody; Zuccon, Sara; Pelizzo, M G

    2013-11-18

    Future solar missions will investigate the Sun from very close distances and optical components are constantly exposed to low energy ions irradiation. In this work we present the results of a new experiment related to low energy alpha particles bombardments on Mo/Si multilayer optical coatings. Different multilayer samples, with and without a protecting capping layer, have been exposed to low energy alpha particles (4keV), fixing the ions fluency and varying the time of exposure in order to change the total dose accumulated. The experimental parameters have been selected considering the potential application of the coatings to future solar missions. Results show that the physical processes occurred at the uppermost interfaces can strongly damage the structure.

  1. Substitution for chromium in 304 stainless steel. [effects on oxidation and corrosion resistance

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Barrett, C. A.

    1978-01-01

    An investigation was conducted to determine the effects of substituting less strategic elements for Cr on oxidation and corrosion resistance of AISI 304 stainless steel. Cyclic oxidation resistance was evaluated at 870 C. Corrosion resistance was determined by exposure of specimens to a boiling copper-rich solution of copper sulfate and sulfuric acid. Alloy substitutes for Cr included Al, Mn, Mo, Si, Ti, V, Y, and misch metal. A level of about 12% Cr was the minimum amount of Cr required for adequate oxidation and corrosion resistance in the modified composition 304 stainless steels. This represents a Cr saving of 33 percent. Two alloys containing 12% Cr plus 2% Al plus 2% Mo and 12% Cr plus 2.65% Si were identified which exhibited oxidation and corrosion resistance comparable to AISI 304 stainless steel.

  2. Towards High Accuracy Reflectometry for Extreme-Ultraviolet Lithography

    PubMed Central

    Tarrio, Charles; Grantham, Steven; Squires, Matthew B.; Vest, Robert E.; Lucatorto, Thomas B.

    2003-01-01

    Currently the most demanding application of extreme ultraviolet optics is connected with the development of extreme ultraviolet lithography. Not only does each of the Mo/Si multilayer extreme-ultraviolet stepper mirrors require the highest attainable reflectivity at 13 nm (nearly 70 %), but the central wavelength of the reflectivity of these mirrors must be measured with a wavelength repeatability of 0.001 nm and the peak reflectivity of the reflective masks with a repeatability of 0.12 %. We report on two upgrades of our NIST/DARPA Reflectometry Facility that have given us the ability to achieve 0.1 % repeatability and 0.3 % absolute uncertainty in our reflectivity measurements. A third upgrade, a monochromator with thermal and mechanical stability for improved wavelength repeatability, is currently in the design phase. PMID:27413610

  3. Application of Plasma Spraying as a Precursor in the Synthesis of Oxidation-Resistant Coatings

    NASA Astrophysics Data System (ADS)

    Ritt, P.; Lu-Steffes, O.; Sakidja, R.; Perepezko, J. H.; Lenling, W.; Crawmer, D.; Beske, J.

    2013-08-01

    Thermal spray methods offer a versatile and flexible approach to the manufacture of coatings as a final product. A novel application of thermal spray coating is demonstrated by incorporating a plasma-sprayed Mo layer coating as a precursor step within an integrated costing design. The effectiveness of the two-step design is illustrated for aluminoborosilica coatings on SiC/C composites and W substrates based on the plasma-sprayed Mo precursor and subsequent codeposition of Si and B by a pack cementation method. Even with incomplete precursor coverage, an aluminoborosilica coating is developed because of the high initial fluidity of the as-pack coating. An effective oxidation resistance is observed following exposure at elevated temperatures (1373-1673 K) in ambient air and during torch testing at 1773 K, providing clear evidence that the plasma spraying of Mo is a viable precursor step in the formation of the oxidation-resistant Mo-Si-B-based coating.

  4. Diffusion Resistant, High-Purity Wafer Carriers For SI Semiconductor Production

    SciTech Connect

    Tiegs, T.N.; Leaskey, L.

    2000-10-01

    The Cooperative Research and Development Agreement (CRADA) was directed towards development of diffusion resistant, high-purity wafer carriers for Si semiconductor production with improved properties compared to current materials. The determination of the infiltration behavior is important for controlling the fabrication process to. obtain consistent high-quality products. Ammonium molybdate or molybdenum carbide were found to be suitable as a precursor to produce SiC-MoSi{sub 2}-Si composites by Si infiltration into carbon preforms. Experiments on the pyrolysis of the preforms showed variable infiltration behavior by the molten Si (within the range of conditions in the present study). Further research is required to reproducibly and consistently fabricate flaw-free articles. The strength of the composites fabricated to-date was 325{+-}124 MPa, which is higher than current commercial products. Better process control should result in higher average strengths and reduce the variability.

  5. Sub-diffraction-limited multilayer coatings for the 0.3 numerical aperture micro-exposure tool for extreme ultraviolet lithography.

    PubMed

    Soufli, Regina; Hudyma, Russell M; Spiller, Eberhard; Gullikson, Eric M; Schmidt, Mark A; Robinson, Jeff C; Baker, Sherry L; Walton, Christopher C; Taylor, John S

    2007-06-20

    Multilayer coating results are discussed for the primary and secondary mirrors of the micro-exposure tool (MET): a 0.30 NA lithographic imaging system with a 200 microm x 600 microm field of view at the wafer plane, operating in the extreme ultraviolet (EUV) region at an illumination wavelength around 13.4 nm. Mo/Si multilayers were deposited by DC-magnetron sputtering on large-area, curved MET camera substrates. A velocity modulation technique was implemented to consistently achieve multilayer thickness profiles with added figure errors below 0.1 nm rms demonstrating sub-diffraction-limited performance, as defined by the classical diffraction limit of Rayleigh (0.25 waves peak to valley) or Marechal (0.07 waves rms). This work is an experimental demonstration of sub-diffraction- limited multilayer coatings for high-NA EUV imaging systems, which resulted in the highest resolution microfield EUV images to date.

  6. XPS and AES analysis of passive films on Fe-25Cr-X (X = Mo, V, Si and Nb) model alloys.

    PubMed

    Hubschmid, C; Landolt, D; Mathieu, H J

    1995-10-01

    Corrosion resistance of stainless steel is due to the presence of a thin passive film of typically 1-2 nm thickness. The influence of ternary alloying elements on the composition of passive films on Fe-Cr alloys and their pitting corrosion resistance has been investigated. Iron-chromium alloys were analyzed by XPS and AES with model alloys (Fe-25Cr-X with X = at % Mo, Si, V and Nb) formed in sulphate solution in the presence and absence of chloride ions. All ternary alloying elements increase the pitting potential compared to the corresponding binary alloy. Films formed in chloride containing sulphate solution contain both electrolyte anions. Scanning Auger microscopy reveals that for a two phase system such as Fe-25Cr-11Nb, the dendritic phase is enriched with chromium, while essentially all of the niobium is located in the interdendritic eutectic.

  7. Optimized capping layers for EUV multilayers

    DOEpatents

    Bajt, Sasa; Folta, James A.; Spiller, Eberhard A.

    2004-08-24

    A new capping multilayer structure for EUV-reflective Mo/Si multilayers consists of two layers: A top layer that protects the multilayer structure from the environment and a bottom layer that acts as a diffusion barrier between the top layer and the structure beneath. One embodiment combines a first layer of Ru with a second layer of B.sub.4 C. Another embodiment combines a first layer of Ru with a second layer of Mo. These embodiments have the additional advantage that the reflectivity is also enhanced. Ru has the best oxidation resistance of all materials investigated so far. B.sub.4 C is an excellent barrier against silicide formation while the silicide layer formed at the Si boundary is well controlled.

  8. A New Method of Metallization for Silicon Solar Cells

    NASA Technical Reports Server (NTRS)

    Macha, M.

    1979-01-01

    The determination of the firing cycle in a horizontal tube furnace for MoO3: Sn ink composition applied by silk screening process on P or N structured solar cells is presented. In comparison with the strip heater used to determine the reaction mechanism, the reduction of MoO3 in the tube furnace progresses at a much faster rate and the Sn:Mo alloy forms at a much lower temperature. The device characteristics determined by the V-I curve showed a high resistance (approx. 10 Ohms) at peak temperatures between 600 C and 800 C. The high series resistance is attributed to the lack of formation of MoSi2 within the used temperature range.

  9. Software for x-ray optics research instrumentation. Final report, 1991

    SciTech Connect

    Knight, L.V.

    1992-03-01

    The statement of work for this contract between The Regents of the University of California and Brigham Young University called for the implementation of computer controlled substrate motion in an existing DC magnetron sputtering system. This task entailed the design and fabrication of a vacuum compatible motor drive and substrate holder, the system had to be capable of closed loop microcomputer control which required the development of a suitable computer interface and control software. Concurrent with this task, the existing magnetron sputtering system was to be upgraded to permit ion assisted deposition. This required modification of the existing sputtering hardware to permit independent control of voltages applied to the substrate and other additional electrode assemblies. In addition to design, fabrication and installation of the system modifications a systematic study of Mo-Si multilayer coatings grown using ion assisted deposition was undertaken. These studies served, in part, as training of LLNL personnel in the ion assisted deposition technique.

  10. Recent advances and developments in refractory alloys

    SciTech Connect

    Nieh, T.G.; Wadsworth, J.

    1993-11-01

    Refractory 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. This paper, presents recent progress in understanding and applications of these alloys. Recent studies to improve the oxidation and mechanical behavior of refractory metal alloys, and particularly Nb alloys, are also discussed. Some Re structures, for extremely high temperature applications (> 2000C), 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-1%Zr, continues. Finally, recent developments in high temperature composites reinforced with refractory metal filaments, and refractory metal-based intermetallics, e.g., Nb{sub 3}Al, Nb{sub 2}Be{sub 17}, and MoSi{sub 2}, are briefly described.

  11. Soft x-ray free electron laser microfocus for exploring matter under extreme conditions.

    PubMed

    Nelson, A J; Toleikis, S; Chapman, H; Bajt, S; Krzywinski, J; Chalupsky, J; Juha, L; Cihelka, J; Hajkova, V; Vysin, L; Burian, T; Kozlova, M; Fäustlin, R R; Nagler, B; Vinko, S M; Whitcher, T; Dzelzainis, T; Renner, O; Saksl, K; Khorsand, A R; Heimann, P A; Sobierajski, R; Klinger, D; Jurek, M; Pelka, J; Iwan, B; Andreasson, J; Timneanu, N; Fajardo, M; Wark, J S; Riley, D; Tschentscher, T; Hajdu, J; Lee, R W

    2009-09-28

    We have focused a beam (BL3) of FLASH (Free-electron LASer in Hamburg: lambda = 13.5 nm, pulse length 15 fs, pulse energy 10-40 microJ, 5 Hz) using a fine polished off-axis parabola having a focal length of 270 mm and coated with a Mo/Si multilayer with an initial reflectivity of 67% at 13.5 nm. The OAP was mounted and aligned with a picomotor controlled six-axis gimbal. Beam imprints on poly(methyl methacrylate) - PMMA were used to measure focus and the focused beam was used to create isochoric heating of various slab targets. Results show the focal spot has a diameter of < or =1 microm. Observations were correlated with simulations of best focus to provide further relevant information.

  12. Imaging diffraction VLS spectrometer for a wavelength range λ > 120 Å

    NASA Astrophysics Data System (ADS)

    Vishnyakov, E. A.; Kolesnikov, A. O.; Kuzin, A. A.; Negrov, D. V.; Ragozin, E. N.; Sasorov, P. V.; Shatokhin, A. N.

    2017-02-01

    A broadband stigmatic (imaging) soft X-ray (λ > 120 Å) spectrometer is experimentally realised. The optical configuration of the spectrometer comprises a plane grazing-incidence reflection grating with a spacing varying across its aperture according to a preassigned law [a so-called varied line-space (VLS) grating] and a broadband spherical normal-incidence mirror with an aperiodic Mo/Si multilayer structure. The average plate scale amounts to ˜5.5 Å mm-1. The radiation is recorded with a matrix CCD detector (2048 × 1024 pixels of size 13 μm). The line spectra of the multiply charged ions LiIII and FV-FVII excited in laser-produced plasma are recorded with a spatial resolution of ˜26 μm and a spectral resolving power R ≈ 500 is experimentally demonstrated.

  13. Molybdenum-tin as a solar cell metallization system

    NASA Technical Reports Server (NTRS)

    Boyd, D. W.; Radics, C.

    1981-01-01

    The operations of solar cell manufacture are briefly examined. The formation of reliable, ohmic, low-loss, and low-cost metal contacts on solar cells is a critical process step in cell manufacturing. In a commonly used process, low-cost metallization is achieved by screen printing a metal powder-glass frit ink on the surface of the Si surface and the conductive metal powder. A technique utilizing a molybdenum-tin alloy for the metal contacts appears to lower the cost of materials and to reduce process complexity. The ink used in this system is formulated from MoO3 with Sn powder and a trace amount of titanium resonate. Resistive losses of the resulting contacts are low because the ink contains no frit. The MoO3 is finally melted and reduced in forming gas (N2+H2) to Mo metal. The resulting Mo is highly reactive which facilitates the Mo-Si bonding.

  14. Oxidation resistance of composite silicide coatings on niobium

    SciTech Connect

    Gloshko, P.I.; Kurtsev, N.F.; Lisichenko, V.I.; Nadtoka, V.N.; Petrenko, M.I.; Zmii, V.I.

    1986-07-01

    This paper reports the oxidation of NbSi/sub 2/-MoSi/sub 2/ composite silicide coatings produced by diffusive siliconizing of molybdenum films on a niobium surface. Molybdenum-coated niobium was siliconized and an x-ray microspectral analysis of the composite silicide coating showed the phase composition to be an ca 80-um-thick outer molybdenum disilicide film with a characteristic coarsely crystalline columnar structure, and inner ca 20-um film of niobium disilicide consisting of the tiny columnar crystals, and a substrate/coating interface comprising a thin, 2-3 um film of lower silicide, i.e., Nb/sub 5/Si/sub 3/. The average grain sizes, unit cell parameters, and x-ray determined densities of the Mo films obtained by various methods are shown.

  15. Growth model of binary alloy nanopowders for thermal plasma synthesis

    SciTech Connect

    Shigeta, Masaya; Watanabe, Takayuki

    2010-08-15

    A new model is developed for numerical analysis of the entire growth process of binary alloy nanopowders in thermal plasma synthesis. The model can express any nanopowder profile in the particle size-composition distribution (PSCD). Moreover, its numerical solution algorithm is arithmetic and straightforward so that the model is easy to use. By virtue of these features, the model effectively simulates the collective and simultaneous combined process of binary homogeneous nucleation, binary heterogeneous cocondensation, and coagulation among nanoparticles. The effect of the freezing point depression due to nanoscale particle diameters is also considered in the model. In this study, the metal-silicon systems are particularly chosen as representative binary systems involving cocondensation processes. In consequence, the numerical calculation with the present model reveals the growth mechanisms of the Mo-Si and Ti-Si nanopowders by exhibiting their PSCD evolutions. The difference of the materials' saturation pressures strongly affects the growth behaviors and mature states of the binary alloy nanopowder.

  16. Investigation of shock-induced and shock-assisted chemical reactions in molybdenum-silicon powder mixtures

    NASA Astrophysics Data System (ADS)

    Vandersall, Kevin Stewart

    1999-10-01

    In this research, chemical reactions occurring in molybdenum and silicon powder mixtures under "shock-induced" (those occurring during the high-pressure shock state) and "shock-assisted" (those occurring subsequent to the shock event, but due to bulk temperature increases) conditions were investigated. Differences in the densities and yield strengths of the two constituents, in addition to the large heat of reaction associated with molybdenum disilicide (MoSi2) formation can lead to shock-induced as well as shock-assisted reactions, which make this an ideal system to delineate the kinetics and mechanisms of reactions occurring in shock-compressed powder mixtures. Shock recovery experiments performed on Mo + 2 Si powder mixtures employing cylindrical implosion geometry showed thermally initiated reactions. A mixed phase eutectic type microstructure of MoSi2 and Mo 5Si3, resulting from reaction occurring due to melting of both reactants, was observed in axial regions of the cylindrical compacts. In regions surrounding the mach stem, melting of only silicon and reaction occurring via dissolution and re-precipitation forming MoSi2 spherules surrounding molybdenum particles in a melted and solidified silicon matrix was observed. The planar pressure shock recovery geometry showed a single phase MoSi2, microstructure formed due to a solid-state pressure-induced reaction process. The time-resolved instrumented experiments were performed using a single stage gas gun in the velocity range of 500 m/s to 1 km/s, and employed poly-vinyl di-flouride (PVDF) stress gauges placed at the front and rear surfaces of the powder to determine the crush strength, densification history, and reaction initiation threshold conditions. Time-resolved experiments performed on ˜58% dense Mo + 2 Si powder mixtures at input stresses less than 4 GPa, showed characteristics of powder densification and dispersed propagated wave stress profiles with rise time >˜40 nanoseconds. At input stress between

  17. Photomask film degradation effects in the wafer fab: how to detect and monitor over time

    NASA Astrophysics Data System (ADS)

    Whittey, John; Hess, Carl; Garcia, Edgardo; Wagner, Mark; Duffy, Brian

    2012-11-01

    As a result of repeated cleanings and exposure effects such as chrome migration or MoSi oxidation some photomasks in the semiconductor fabs exhibit changes in critical dimension uniformity (CDU) over time. Detecting these effects in a timely manner allows for better risk management and process control in manufacturing. By monitoring changes in film reflectance intensity due to the various degradation mechanisms it is possible to predict when they may begin to influence across chip line width variations (ACLV). By accurately predicting the magnitude of these changes it is possible for semiconductor manufacturers to replace the photomasks before they have an impact on yields. This paper looks at possible causes of CDU variations on reticles during use and how this information might be used to improve or monitor reticle CDU changes over time.

  18. Upgrading multilayer zone plate technology for hard x-ray focusing

    NASA Astrophysics Data System (ADS)

    Hirotomo, Toshiki; Takano, Hidekazu; Sumida, Kazuhiro; Koyama, Takahisa; Konishi, Shigeki; Ichimaru, Satoshi; Ohchi, Tadayuki; Takenaka, Hisataka; Tsusaka, Yoshiyuki; Kagoshima, Yasushi

    2016-01-01

    Multilayer zone plate (MZP) technology for hard X-ray focusing was upgraded and its focusing performance was evaluated using 20-keV X-rays at the synchrotron beamline (BL24XU) of SPring-8. The MZP consists of MoSi2 and Si layers alternately deposited on a glass fiber by magnetron sputtering so that all zone boundaries satisfy the Fresnel zone configuration. The focused beam was evaluated using knife-edge scanning in which the measured intensity distribution is identical to the line spread function (LSF) in the focal plane. The focused beamsize of about 30 nm was estimated by oscillation peaks observed in the measured LSF according to Rayleigh's criterion.

  19. Measurement of soft x-ray multilayer mirror reflectance at normal incidence using laser-produced plasmas

    SciTech Connect

    Trail, J.A.; Byer, R.L.; Barbee T.W. Jr.

    1988-01-25

    We have used laser-produced plasmas as a broadband source of soft x rays to measure the normal incidence reflectance of multilayer mirrors in the 10--25 nm spectral region. The measurements have a spectral resolution of 0.03 nm and a reflectance resolution of 10%. Measurements made on a Mo/Si multilayer show excellent agreement with results obtained using a synchrotron and indicate a normal incidence peak reflectance of over 50% at 15 nm. By repeating the reflectance measurement at different positions across a single 7.5 cm mirror we determined multilayer uniformity as a function of position and we relate this dependence to the geometry of the deposition process.

  20. SiC/Mg multilayer coatings for SCORE coronagraph: long term stability analysis

    NASA Astrophysics Data System (ADS)

    Pelizzo, Maria Guglielmina; Fineschi, Silvano; Zuppella, Paola; Corso, Alain Jody; Windt, David L.; Nicolosi, Piergiorgio

    2011-10-01

    SiC/Mg multilayers have been used as coatings of the Sounding-rocket CORonagraphic Experiment (SCORE) telescope mirrors launched during the NASA HERSCHEL program. This materials couple has been largely studied by researchers since it provides higher performances than a standard Mo/Si multilayer; the SCORE mirrors show in fact a peak reflectance of around 40% at HeII 30.4 nm. Nevertheless, long term stability of this coating is an open problem. A study on the aging and stability of this multilayer has been carried on. SiC/Mg multilayer samples characterized by different structural parameters have been deposited. They have been measured just after deposition and four years later to verify degradation based on natural aging. Experimental results and analysis are presented.

  1. Exploring the origin of charging-induced pattern positioning errors in mask making using e-beam lithography

    NASA Astrophysics Data System (ADS)

    Chen, Chien-Cheng; Liu, Tzu-Ling; Chang, Shao-Wen; Ho, Yen-Cheng; Chen, Chia-Jen; Lin, Chih-Cheng; Lien, Ta-Cheng; Lee, Hsin-Chang; Yen, Anthony

    2015-10-01

    The authors present a detailed observation of the charge-induced pattern positioning errors (CIPPEs) in a variableshape e-beam writer on an opaque-MoSi-over-glass (OMOG) mask by directly measuring the pattern shifts using a mask registration tool. The CIPPEs are found to have one short-range, that is exponentially decaying in space, and the other constant offset components. The exponential term that decays slowly in time, whereas the constant offset fast diminishes. By applying a charge dissipation layer (CDL), the authors experimentally verify that the exponential component results from the charges in resist. On the other hands, the constant offset that can not be eliminated by the CDL is speculated to be charges in the substrate according to the Monte Carlo simulation.

  2. Alternate Multilayer Gratings with Enhanced Diffraction Efficiency in the 500-5000 eV Energy Domain

    SciTech Connect

    Polack, Francois; Lagarde, Bruno; Idir, Mourad; Cloup, Audrey Liard; Jourdain, Erick; Roulliay, Marc; Delmotte, Franck; Gautier, Julien; Ravet-Krill, Marie-Francoise

    2007-01-19

    An alternate multilayer (AML) grating is a 2 dimensional diffraction structure formed on an optical surface, having a 0.5 duty cycle in the in-plane and in the in-depth direction. It can be made by covering a shallow depth laminar grating with a multilayer stack. We show here that their 2D structure confer AML gratings a high angular and energetic selectivity and therefore enhanced diffraction properties, when used in grazing incidence. In the tender X-ray range (500eV - 5000 eV) they behave much like blazed gratings. Over 15% efficiency has been measured on a 1200 lines/mm Mo/Si AML grating in the 1.2 - 1.5 keV energy range. Computer simulations show that selected multilayer materials such as Cr/C should allow diffraction efficiency over 50% at photon energies over 3 keV.

  3. Molybdenum-tin as a solar cell metallization system

    NASA Technical Reports Server (NTRS)

    Boyd, D. W.; Radics, C.

    1981-01-01

    The operations of solar cell manufacture are briefly examined. The formation of reliable, ohmic, low-loss, and low-cost metal contacts on solar cells is a critical process step in cell manufacturing. In a commonly used process, low-cost metallization is achieved by screen printing a metal powder-glass frit ink on the surface of the Si surface and the conductive metal powder. A technique utilizing a molybdenum-tin alloy for the metal contacts appears to lower the cost of materials and to reduce process complexity. The ink used in this system is formulated from MoO3 with Sn powder and a trace amount of titanium resonate. Resistive losses of the resulting contacts are low because the ink contains no frit. The MoO3 is finally melted and reduced in forming gas (N2+H2) to Mo metal. The resulting Mo is highly reactive which facilitates the Mo-Si bonding.

  4. Process for producing dispersed particulate composite materials

    DOEpatents

    Henager, Jr., Charles H.; Hirth, John P.

    1995-01-01

    This invention is directed to a process for forming noninterwoven dispersed particulate composite products. In one case a composite multi-layer film product comprises a substantially noninterwoven multi-layer film having a plurality of discrete layers. This noninterwoven film comprises at least one discrete layer of a first material and at least one discrete layer of a second material. In another case the first and second materials are blended together with each other. In either case, the first material comprises a metalloid and the second material a metal compound. At least one component of a first material in one discrete layer undergoes a solid state displacement reaction with at least one component of a second material thereby producing the requisite noninterwoven composite film product. Preferably, the first material comprises silicon, the second material comprises Mo.sub.2 C, the third material comprises SiC and the fourth material comprises MoSi.sub.2.

  5. 5000 groove/mm multilayer-coated blazed grating with 33percent efficiency in the 3rd order in the EUV wavelength range

    SciTech Connect

    Advanced Light Source; Voronov, Dmitriy L.; Anderson, Erik; Cambie, Rossana; Salmassi, Farhad; Gullikson, Eric; Yashchuk, Valeriy; Padmore, Howard; Ahn, Minseung; Chang, Chih-Hao; Heilmann, Ralf; Schattenburg, Mark

    2009-07-07

    We report on recent progress in developing diffraction gratings which can potentially provide extremely high spectral resolution of 105-106 in the EUV and soft x-ray photon energy ranges. Such a grating was fabricated by deposition of a multilayer on a substrate which consists ofa 6-degree blazed grating with a high groove density. The fabrication of the substrate gratings was based on scanning interference lithography and anisotropic wet etch of silicon single crystals. The optimized fabrication process provided precise control of the grating periodicity, and the grating groove profile, together with very short anti-blazed facets, and near atomically smooth surface blazed facets. The blazed grating coated with 20 Mo/Si bilayers demonstrated a diffraction efficiency in the third order as high as 33percent at an incidence angle of 11? and wavelength of 14.18 nm.

  6. Molecular dynamics and dynamic Monte-Carlo simulation of irradiation damage with focused ion beams

    NASA Astrophysics Data System (ADS)

    Ohya, Kaoru

    2017-03-01

    The focused ion beam (FIB) has become an important tool for micro- and nanostructuring of samples such as milling, deposition and imaging. However, this leads to damage of the surface on the nanometer scale from implanted projectile ions and recoiled material atoms. It is therefore important to investigate each kind of damage quantitatively. We present a dynamic Monte-Carlo (MC) simulation code to simulate the morphological and compositional changes of a multilayered sample under ion irradiation and a molecular dynamics (MD) simulation code to simulate dose-dependent changes in the backscattering-ion (BSI)/secondary-electron (SE) yields of a crystalline sample. Recent progress in the codes for research to simulate the surface morphology and Mo/Si layers intermixing in an EUV lithography mask irradiated with FIBs, and the crystalline orientation effect on BSI and SE yields relating to the channeling contrast in scanning ion microscopes, is also presented.

  7. Upgrading multilayer zone plate technology for hard x-ray focusing

    SciTech Connect

    Hirotomo, Toshiki; Konishi, Shigeki; Takano, Hidekazu Sumida, Kazuhiro; Tsusaka, Yoshiyuki; Kagoshima, Yasushi; Koyama, Takahisa; Ichimaru, Satoshi; Ohchi, Tadayuki; Takenaka, Hisataka

    2016-01-28

    Multilayer zone plate (MZP) technology for hard X-ray focusing was upgraded and its focusing performance was evaluated using 20-keV X-rays at the synchrotron beamline (BL24XU) of SPring-8. The MZP consists of MoSi{sub 2} and Si layers alternately deposited on a glass fiber by magnetron sputtering so that all zone boundaries satisfy the Fresnel zone configuration. The focused beam was evaluated using knife-edge scanning in which the measured intensity distribution is identical to the line spread function (LSF) in the focal plane. The focused beamsize of about 30 nm was estimated by oscillation peaks observed in the measured LSF according to Rayleigh’s criterion.

  8. Experimental investigations on the chemical state of solid fission-product elements in U3Si2

    NASA Astrophysics Data System (ADS)

    Ugajin, M.; Itoh, A.

    1994-10-01

    The uranium silicide U3Si2 has a congruent melting point of 1665 C and possesses higher uranium density (11.3 g U/cc) and higher thermal conductivity than the uranium dioxide currently used in light water reactors. U3Si2 is in use as a research reactor fuel (US Nuclear Regulatory Commission, NUREG-1313, July, 1988), representing a potentiality for power reactor fuel. A first attempt is made in this study to predict the chemical state of the solid fission-product elements comprising zirconium, molybdenum, rare earth elements, alkaline earth metals and elements of the platinum group. Ternary phase equilibria in the U-Mo-Si and U-Ru-Si systems are also investigated to supplement the fission product chemistry in U3Si2.

  9. Friction and wear properties of three hard refractory coatings applied by radiofrequency sputtering

    NASA Technical Reports Server (NTRS)

    Brainard, W. A.

    1977-01-01

    The adherence, friction, and wear properties of thin hard refractory compound coatings applied to 440C bearing steel by radiofrequency sputtering were investigated. Friction and wear tests were done with nonconforming pin on disk specimens. The compounds examined were chromium carbide, molybdenum silicide, and titanium carbide. The adherence, friction, and wear were markedly improved by the application of a bias voltage to the bearing steel substrate during coating deposition. Analysis by X-ray photoelectron spectroscopy indicated that the improvement may be due to a reduction in impurities in bias deposited coatings. A fivefold reduction in oxygen concentration in MoSi2 coating by biasing was noted. Chromium carbide was not effective as an antiwear coating. Molybdenum silicide provided some reduction in both friction and wear. Titanium carbide exhibited excellent friction and antiwear properties at light loads. Plastic flow and transfer of the coating material onto the pin specimen appears to be important in achieving low friction and wear.

  10. In-line phase retarder and polarimeter for conversion of linear to circular polarization

    SciTech Connect

    Kortright, J.B.; Smith, N.V.; Denlinger, J.D.

    1997-04-01

    An in-line polarimeter including phase retarder and linear polarizer was designed and commissioned on undulator beamline 7.0 for the purpose of converting linear to circular polarization for experiments downstream. In commissioning studies, Mo/Si multilayers at 95 eV were used both as the upstream, freestanding phase retarder and the downstream linear polarized. The polarization properties of the phase retarder were characterized by direct polarimetry and by collecting MCD spectra in photoemission from Gd and other magnetic surfaces. The resonant birefringence of transmission multilayers results from differing distributions of s- and p-component wave fields in the multilayer when operating near a structural (Bragg) interference condition. The resulting phase retardation is especially strong when the interference is at or near the Brewster angle, which is roughly 45{degrees} in the EUV and soft x-ray ranges.

  11. Surface Engineering of Mo-Base Alloys for Elevated-Temperature Environmental Resistance

    NASA Astrophysics Data System (ADS)

    Perepezko, J. H.

    2015-07-01

    The synthesis of robust coatings that provide protection against environmental attack at ultrahigh temperatures is a difficult challenge. To achieve this goal for Mo-base alloys, the fundamental concepts of reactive diffusion pathway analysis and kinetic biasing are used to design a multilayer Mo-Si-B-base coating with a phase sequencing that allows for structural and thermodynamic compatibility and an underlying diffusion barrier to maintain coating integrity. The coating design concepts have a general applicability. The coating structure evolution during high-temperature exposure facilitates a prolonged lifetime as well as self-healing capability. The borosilicide coatings that can be synthesized by a pack cementation process yield superior environmental resistance for Mo-base systems at temperatures up to at least 1,700°C and can be adapted to apply to other refractory metal and ceramic systems.

  12. M5Si3(M=Ti, Nb, Mo) Based Transition-Metal Silicides for High Temperature Applications

    SciTech Connect

    Tang, Zhihong

    2007-01-01

    Transition metal silicides are being considered for future engine turbine components at temperatures up to 1600 C. Although significant improvement in high temperature strength, room temperature fracture toughness has been realized in the past decade, further improvement in oxidation resistance is needed. Oxidation mechanism of Ti5Si3-based alloys was investigated. Oxidation behavior of Ti5Si3-based alloy strongly depends on the atmosphere. Presence of Nitrogen alters the oxidation behavior of Ti5Si3 by nucleation and growth of nitride subscale. Ti5Si3.2and Ti5Si3C0.5 alloys exhibited an excellent oxidation resistance in nitrogen bearing atmosphere due to limited dissolution of nitrogen and increased Si/Ti activity ratio. MoSi2 coating developed by pack cementation to protect Mo-based Mo-Si-B composites was found to be effective up to 1500 C. Shifting coating composition to T1+T2+Mo3Si region showed the possibility to extend the coating lifetime above 1500 C by more than ten times via formation of slow growing Mo3Si or T2 interlayer without sacrificing the oxidation resistance of the coating. The phase equilibria in the Nb-rich portion of Nb-B system has been evaluated experimentally using metallographic analysis and differential thermal analyzer (DTA). It was shown that Nbss (solid solution) and NbB are the only two primary phases in the 0-40 at.% B composition range, and the eutectic reaction L {leftrightarrow} NbSS + NbB was determined to occur at 2104 ± 5 C by DTA.

  13. Prospect of EUV mask repair technology using e-beam tool

    NASA Astrophysics Data System (ADS)

    Kanamitsu, Shingo; Hirano, Takashi; Suga, Osamu

    2010-09-01

    Currently, repair machines used for advanced photomasks utilize principle method like as FIB, AFM, and EB. There are specific characteristic respectively, thus they have an opportunity to be used in suitable situation. But when it comes to EUV generation, pattern size is so small highly expected as under 80nm that higher image resolution and repair accuracy is needed for its machines. Because FIB machine has intrinsic damage problem induced by Ga ion and AFM machine has critical tip size issue, those machines are basically difficult to be applied for EUV generation. Consequently, we focused on EB repair tool for research work. EB repair tool has undergone practical milestone about MoSi based masks. We have applied same process which is used for MoSi to EUV blank and confirmed its reaction. Then we found some severe problems which show uncontrollable feature due to its enormously strong reaction between etching gas and absorber material. Though we could etch opaque defect with conventional method and get the edge shaped straight by top-down SEM viewing, there were problems like as sidewall undercut or local erosion depending on defect shape. In order to cope with these problems, the tool vender has developed a new process and reported it through an international conference [1]. We have evaluated the new process mentioned above in detail. In this paper, we will bring the results of those evaluations. Several experiments for repair accuracy, process stability, and other items have been done under estimation of practical condition assuming diversified size and shape defects. A series of actual printability tests will be also included. On the basis of these experiments, we consider the possibility of EB-repair application for 20nm pattern.

  14. Effectiveness of Diffusion Barrier Coatings for Mo-Re Embedded in C/SiC and C/C

    NASA Technical Reports Server (NTRS)

    Glass, David E.; Shenoy, Ravi N.; Wang, Zeng-Mei; Halbig, Michael C.

    2001-01-01

    Advanced high-temperature cooling applications may often require the elevated-temperature capability of carbon/silicon carbide or carbon/carbon composites in combination with the hermetic capability of metallic tubes. In this paper, the effects of C/SiC and C/C on tubes fabricated from several different refractory metals were evaluated. Though Mo, Nb, and Re were evaluated in the present study, the primary effort was directed toward two alloys of Mo-Re, namely, arc cast Mo-41Re and powder metallurgy Mo-47.5Re. Samples of these refractory metals were subjected to either the PyC/SiC deposition or embedding in C/C. MoSi2(Ge), R512E, and TiB2 coatings were included on several of the samples as potential diffusion barriers. The effects of the processing and thermal exposure on the samples were evaluated by conducting burst tests, microhardness surveys, and scanning electron microscopic examination (using either secondary electron or back scattered electron imaging and energy dispersive spectroscopy). The results showed that a layer of brittle Mo-carbide formed on the substrates of both the uncoated Mo-41Re and the uncoated Mo-47.5Re, subsequent to the C/C or the PyC/SiC processing. Both the R512E and the MoSi2(Ge) coatings were effective in preventing not only the diffusion of C into the Mo-Re substrate, but also the formation of the Mo-carbides. However, none of the coatings were effective at preventing both C and Si diffusion without some degradation of the substrate.

  15. Development of intermetallic-hardened abrasion-resistant weld hardfacing alloys

    SciTech Connect

    School, M.R.

    1986-01-01

    Chromium and cobalt are strategic materials in the US and both are major constituents in many weld hardfacing alloys. Substitution for these materials or alternatives to their use was a primary direction of this investigation which was conducted in conjunction with the US Bureau of Mines. Minimization of the use of strategic materials was the criteria guiding the development of intermetallic-hardened abrasion resistant weld hardfacing materials. Other criteria were that the new alloy contain a hard intermetallic compound in an FCC matrix, and that these intermetallic compounds be stable at room temperature. A survey of ternary systems was made and the Fe-Mo-Ni system was selected to provide a basis for alloy development. Fe-Mo-Ni alloys synthesized by arc-melting and similar alloys made by welding possessed similar microstructures, a (Fe, Ni){sub 7}Mo{sub 6} intermetallic plus austenite eutectic in an austenitic matrix. These materials exhibited poor abrasive resistance. Silicon additions to the alloy promoted formation of a Laves phase FeMoSi intermetallic which helped increase the abrasive wear resistance. Through a series of alloy chemistry iterations a final composition of Fe-20Mo-15Ni-5Si was selected. Heat treatment of this alloy at 550 to 650 C caused second phase precipitation in the matrix and raised the hardness about 14 points HRC to 50 HRC. The alloy's wear rate, measured with the pin-on-drum abrasive wear test, was 6.3 to 6.5 mg/m. However this was twice the wear rate observed in commercial high-carbon high-chromium alloys. Based on examination of the alloy microstructures, their chemistry, and an analysis of the Fe-Mo-Si phase system; directions for further research are to increase the molybdenum and silicon content to produce a Fe-20Mo-10Ni-15Si composition.

  16. Elastic properties of C40 transition metal disilicides

    SciTech Connect

    Chu, F.; Maloy, S.A.; Petrovic, J.J.; Mitchell, T.E.; Lei, M.

    1996-08-01

    Room-temperature and low temperature elastic properties of hexagonal C40 transition metal disilicides, NbSi{sub 2} and TaSi{sub 2}, have been studied using Resonant Ultrasound Spectroscopy (RUS). All five independent elastic stiffness constants c{sub ij} for NbSi{sub 2} and TaSi{sub 2} single crystals have been obtained. The temperature dependence of the c{sub ij} is normal but not large. The orientation dependence of the Young`s and shear moduli was examined in comparison with other transition metal disilicides. The room temperature shear moduli in the {l_brace}0001{r_brace} plane, with values of 145.3 and 143.7 GPa for NbSi{sub 2} and TaSi{sub 2} respectively, are low relative to those in the equivalent pseudo hexagonal {l_brace}220{r_brace} close-packed plane for tetragonal C11{sub b} MoSi{sub 2} and WSi{sub 2}. The isotropic elastic constants for polycrystalline materials were also calculated. The results show that the various moduli are all much higher than those of the constituent elements. The room temperature Poisson`s ratios of NbSi{sub 2} and TaSi{sub 2} are 0.18 and 0.19, respectively, which are smaller than those of the constituent elements and smaller than most materials. The Debye temperatures, {theta}{sub D}, were estimated to be 688 K for NbSi{sub 2} and 552 K for TaSi{sub 2}. The elastic properties of C40 VSi{sub 2}, NbSi{sub 2}, TaSi{sub 2}, and CrSi{sub 2} and C11{sub b} MoSi{sub 2} and WSi{sub 2} are compared and the possible influence on mechanical behavior discussed.

  17. Residual stress control by ion beam assisted deposition

    SciTech Connect

    Was, G.S.; Jones, J.W.; Parfitt, L.; Kalnas, C.E.; Goldiner, M.

    1996-12-31

    The origin of residual stresses were studied in both crystalline metallic films and amorphous oxide films made by ion beam assisted deposition (IBAD). Monolithic films of Al{sub 2}O{sub 3} were deposited during bombardment by Ne, Ar or Kr over a narrow range of energies, E, and a wide range of ion-to-atom arrival rate ratios, R and were characterized in terms of composition, thickness, density, crystallinity, microstructure and residual stress. The stress was a strong function of ion beam parameters and gas content and compares to the behavior of other amorphous compounds such as MoSi{sub x} and WSi{sub 2.2}. With increasing normalized energy (eV/atom), residual stress in crystalline metallic films (Mo, W) increases in the tensile direction before reversing and becoming compressive at high normalized energy. The origin of the stress is most likely due to densification or interstitial generation. Residual stress in amorphous films (Al{sub 2}O{sub 3}, MoSi{sub x} and WSi{sub 2.2}) is initially tensile and monotonically decreases into the compressive region with increasing normalized energy. The amorphous films also incorporate substantially more gas than crystalline films and in the case of Al{sub 2}O{sub 3} are characterized by a high density of voids. Stress due to gas pressure in existing voids explains neither the functional dependence on gas content nor the magnitude of the observed stress. A more likely explanation for the behavior of stress is gas incorporation into the matrix, where the amount of incorporated gas is controlled by trapping.

  18. Laser-plasma SXR/EUV sources: adjustment of radiation parameters for specific applications

    NASA Astrophysics Data System (ADS)

    Bartnik, A.; Fiedorowicz, H.; Fok, T.; Jarocki, R.; Kostecki, J.; Szczurek, A.; Szczurek, M.; Wachulak, P.; Wegrzyński, Ł.

    2014-12-01

    In this work soft X-ray (SXR) and extreme ultraviolet (EUV) laser-produced plasma (LPP) sources employing Nd:YAG laser systems of different parameters are presented. First of them is a 10-Hz EUV source, based on a double-stream gaspuff target, irradiated with the 3-ns/0.8J laser pulse. In the second one a 10 ns/10 J/10 Hz laser system is employed and the third one utilizes the laser system with the pulse shorten to approximately 1 ns. Using various gases in the gas puff targets it is possible to obtain intense radiation in different wavelength ranges. This way intense continuous radiation in a wide spectral range as well as quasi-monochromatic radiation was produced. To obtain high EUV or SXR fluence the radiation was focused using three types of grazing incidence collectors and a multilayer Mo/Si collector. First of them is a multfoil gold plated collector consisted of two orthogonal stacks of ellipsoidal mirrors forming a double-focusing device. The second one is the ellipsoidal collector being part of the axisymmetrical ellipsoidal surface. Third of the collectors is composed of two aligned axisymmetrical paraboloidal mirrors optimized for focusing of SXR radiation. The last collector is an off-axis ellipsoidal multilayer Mo/Si mirror allowing for efficient focusing of the radiation in the spectral region centered at λ = 13.5 ± 0.5 nm. In this paper spectra of unaltered EUV or SXR radiation produced in different LPP source configurations together with spectra and fluence values of focused radiation are presented. Specific configurations of the sources were assigned to various applications.

  19. M(5)-silicon (M= titanium, niobium, molybdenum) based transition-metal silicides for high temperature applications

    NASA Astrophysics Data System (ADS)

    Tang, Zhihong

    2007-12-01

    Transition metal silicides are being considered for future engine turbine components at temperatures up to 1600ºC. Although significant improvement in high temperature strength, room temperature fracture toughness has been realized in the past decade, further improvement in oxidation resistance is needed. Oxidation mechanism of Ti5Si3-based alloys was investigated. Oxidation behavior of Ti5Si3-based alloy strongly depends on the atmosphere. Presence of Nitrogen alters the oxidation behavior of Ti5Si3 by nucleation and growth of nitride subscale. Ti5Si3.2 and Ti5Si3C0.5 alloys exhibited an excellent oxidation resistance in nitrogen bearing atmosphere due to limited dissolution of nitrogen and increased Si/Ti activity ratio. MoSi2 coating developed by pack cementation to protect Mo-based Mo-Si-B composites was found to be effective up to 1500ºC. Shifting coating composition to T1+T2+Mo3Si region showed the possibility to extend the coating lifetime above 1500ºC by more than ten times via formation of slow growing Mo3Si or T2 interlayer without sacrificing the oxidation resistance of the coating. The phase equilibria in the Nb-rich portion of Nb-B system has been evaluated experimentally using metallographic analysis and differential thermal analyzer (DTA). It was shown that Nbss (solid solution) and NbB are the only two primary phases in the 0-40 at.% B composition range, and the eutectic reaction L ↔ Nbss + NbB was determined to occur at 2104+/-5°C by DTA.

  20. Innovative multilayer coatings for space solar physics: performances and stability over time

    NASA Astrophysics Data System (ADS)

    Zuppella, Paola; Corso, Alain J.; Nicolosi, Piergiorgio; Windt, David L.; Pelizzo, Maria G.

    2011-05-01

    Different solar mission are in progress and others are foreseen in the next future to study the structure and the dynamics of the Sun and its interaction with the Earth. Different instruments devoted to solar physics are required to have high reflecting MultiLayers (MLs) coatings. For example, the Multi Element Telescope for Imaging and Spectroscopy (METIS) coronograph will fly on board of SOLar Orbiter (SOLO) mission to perform simultaneous observation at 30.4 nm (He - II Lyman - α line), 121.6 nm (H - I Lyman - α line) and in the visible range, therefore its optics will require high performances in a wide spectral region. It should be desirable to reach higher reflectivity as well as long term stability and lifetime, then different candidate coatings will be considered. The Sounding - Rocket Coronographic Experiment (SCORE) is a prototype of METIS equipped with Mg/SiC optics and it has flown on board of a NASA sounding rocket. The Mg/SiC multilayers offer good performances in terms of reflectivity, but the long term stability and the lifetime have been preliminary investigated and there are open problems to be further studied. Besides standard Mo/Si multilayer, a possible alternative is represented by new multilayer structures based on well known Mo/Si stack in which the performances have been improved by superimposing innovative capping layers. Another alternative is represented by a recently developed multilayer based on an Ir/Si material couple. In this paper we review and compare the performances of such multilayer in all the spectral ranges of interest for SOLO.

  1. Development of an ultrahigh-precision x-ray optics

    NASA Astrophysics Data System (ADS)

    Kitamoto, Shunji; Takano, Haruko; Saitoh, Harue; Yamamoto, Norimasa; Kohmura, Takayoshi; Suga, Kazuharu; Sekiguchi, Hiroyuki; Ohkawa, Yohei; Kanai, Jun'ichi; Chiba, Shigeto

    2003-12-01

    We are developing an ultra high precision Soft X-ray telescope. The design of the telescope is a normal incident one for 13.5 nm band using Mo/Si multilayers. Two ideas are introduced. One is the optical measurement system in order to monitor the precision of the optics system. The other is the adaptive optics system with a deformable mirror. Using an X ray-optical separation filter, we can always monitor the deformation of the optics by optical light. With this information, we can control the deformable mirror to compensate the system distortion as a closed loop system. We confirmed that the absolute precision of the wave front sensor was less than 3 nm rms. This is also confirmed that the determination of the image center of each micro lens can be ~1/100 of the pixel size. The precision of the deformable mirror was roughly 5 nm rms. Using the closed loop control the accuracy of the repeatability of the shape of the deformable mirror is less than 2 nm rms. The shape of the primary mirror was an off-axis paraboloide with an effective diameter of 80 mm. This primary mirror was coated by Mo/Si multilayers. The reflectivity of the primary mirror at 13.5 nm was ranging from 30 to 50%. The X ray-optical separation filter was made from Zr with a thickness of ~170 nm. The transmission of the filter for low energy X-ray measured and was roughly 50% at thickness of ~170 nm. The transmission of the filter for low energy X-ray was measured and was roughly 50% at 13.5 nm.

  2. Advanced repair solution of clear defects on HTPSM by using nanomachining tool

    NASA Astrophysics Data System (ADS)

    Lee, Hyemi; Kim, Munsik; Jung, Hoyong; Kim, Sangpyo; Yim, Donggyu

    2015-10-01

    As the mask specifications become tighter for low k1 lithography, more aggressive repair accuracy is required below sub 20nm tech. node. To meet tight defect specifications, many maskshops select effective repair tools according to defect types. Normally, pattern defects are repaired by the e-beam repair tool and soft defects such as particles are repaired by the nanomachining tool. It is difficult for an e-beam repair tool to remove particle defects because it uses chemical reaction between gas and electron, and a nanomachining tool, which uses physical reaction between a nano-tip and defects, cannot be applied for repairing clear defects. Generally, film deposition process is widely used for repairing clear defects. However, the deposited film has weak cleaning durability, so it is easily removed by accumulated cleaning process. Although the deposited film is strongly attached on MoSiN(or Qz) film, the adhesive strength between deposited Cr film and MoSiN(or Qz) film becomes weaker and weaker by the accumulated energy when masks are exposed in a scanner tool due to the different coefficient of thermal expansion of each materials. Therefore, whenever a re-pellicle process is needed to a mask, all deposited repair points have to be confirmed whether those deposition film are damaged or not. And if a deposition point is damaged, repair process is needed again. This process causes longer and more complex process. In this paper, the basic theory and the principle are introduced to recover clear defects by using nanomachining tool, and the evaluated results are reviewed at dense line (L/S) patterns and contact hole (C/H) patterns. Also, the results using a nanomachining were compared with those using an e-beam repair tool, including the cleaning durability evaluated by the accumulated cleaning process. Besides, we discuss the phase shift issue and the solution about the image placement error caused by phase error.

  3. Mask CD uniformity metrology for logic patterning and its correlation to wafer data

    NASA Astrophysics Data System (ADS)

    Le Gratiet, Bertrand; Zékri, Raphaël.; Sundermann, Frank; Trautzsch, Thomas; Thaler, Thomas; Birkner, Robert; Buttgereit, Ute

    2012-06-01

    With the next technology nodes 193nm lithography is pushed to its utmost limits. The industry is forced to print at low k1 factor which goes along with a high MEEF. Additionally, new blank materials are being introduced for smaller nodes. From 4x node and beyond, global CD uniformity on wafer is getting more critical and becomes key factor to ensure a high yield in chip production. Advanced process control is required and correction strategies are applied to maintain tight wafer CD uniformity. Beside other parameters, like scanner and etch process, mask CD uniformity is one main contributor to the intra-field CD on wafer. To enable effective CDU correction strategies it is necessary to establish a mask CD uniformity metrology which shows a good correlation to wafer prints. Especially for logic pattern mask uniformity measurements to control intra-field CD uniformity becomes challenging. In this paper we will focus on mask CD uniformity measurement for logic application utilizing WLCD, which is based on aerial image technology. We will investigate 40nm node and 28nm node gate masks using 6% MoSi phase shifting mask and MoSi binary mask respectively. Furthermore, we will correlate the mask CD uniformity data to wafer data to evaluate the capability of WLCD to predict the intra-field wafer CD uniformity correctly in order to support feedforward correction strategies. We will show that WLCD shows an excellent correlation to wafer data. Additionally, we will provide an outlook on logic contact-hole masks showing first CD uniformity data and wafer correlation data.

  4. Developing Topological Insulator Fiber Based Photon Pairs Source for Ultrafast Optoelectronic Applications

    DTIC Science & Technology

    2016-04-01

    telecom wavelengths [1-3]. The large n2 ~ 10-10 cm2/W [4] of the TI (compared to ZnO Quantum Dots : n2 ~10-14 cm2/W; GaAs: n2 ~ 10-13 cm2/W; Si: n2...singular opportunity for accurate quantum operations in secure quantum communications and quantum computation. 15. SUBJECT TERMS Topological insulator...entangled photon pairs; quantum computation 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT U 18. NUMBER OF PAGES 19a. NAME OF

  5. Method of improving field emission characteristics of diamond thin films

    DOEpatents

    Krauss, Alan R.; Gruen, Dieter M.

    1999-01-01

    A method of preparing diamond thin films with improved field emission properties. The method includes preparing a diamond thin film on a substrate, such as Mo, W, Si and Ni. An atmosphere of hydrogen (molecular or atomic) can be provided above the already deposited film to form absorbed hydrogen to reduce the work function and enhance field emission properties of the diamond film. In addition, hydrogen can be absorbed on intergranular surfaces to enhance electrical conductivity of the diamond film. The treated diamond film can be part of a microtip array in a flat panel display.

  6. Method of improving field emission characteristics of diamond thin films

    DOEpatents

    Krauss, A.R.; Gruen, D.M.

    1999-05-11

    A method of preparing diamond thin films with improved field emission properties is disclosed. The method includes preparing a diamond thin film on a substrate, such as Mo, W, Si and Ni. An atmosphere of hydrogen (molecular or atomic) can be provided above the already deposited film to form absorbed hydrogen to reduce the work function and enhance field emission properties of the diamond film. In addition, hydrogen can be absorbed on intergranular surfaces to enhance electrical conductivity of the diamond film. The treated diamond film can be part of a microtip array in a flat panel display. 3 figs.

  7. Capping Layer (CL) Induced Antidamping in CL/Py/β-W System (CL: Al, β-Ta, Cu, β-W).

    PubMed

    Behera, Nilamani; Guha, Puspendu; Pandya, Dinesh K; Chaudhary, Sujeet

    2017-08-29

    For achieving ultrafast switching speed and minimizing dissipation losses, the spin-based data storage device requires a control on effective damping (αeff) of nanomagnetic bits. Incorporation of interfacial antidamping spin orbit torque (SOT) in spintronic devices therefore has high prospects for enhancing their performance efficiency. Clear evidence of such an interfacial antidamping is found in Al capped Py(15 nm)/β-W(tW)/Si (Py = Ni81Fe19 and tW = thickness of β-W), which is in contrast to the increase of αeff (i.e., damping) usually associated with spin pumping as seen in Py(15 nm)/β-W(tW)/Si system. Because of spin pumping, the interfacial spin mixing conductance (g(↑↓)) at Py/β-W interface and spin diffusion length (λSD) of β-W are found to be 1.63(±0.02) × 10(18) m(-2) (1.44(±0.02) × 10(18) m(-2)) and 1.42(±0.19) nm (1.00(±0.10) nm) for Py(15 nm)/β-W(tW)/Si (β-W(tW)/Py(15 nm)/Si) bilayer systems. Other different nonmagnetic capping layers (CL), namely, β-W(2 nm), Cu(2 nm), and β-Ta(2,3,4 nm) were also grown over the same Py(15 nm)/β-W(tW). However, antidamping is seen only in β-Ta(2,3 nm)/Py(15 nm)/β-W(tW)/Si. This decrease in αeff is attributed to the interfacial Rashba like SOT generated by nonequilibrium spin accumulation subsequent to the spin pumping. Contrary to this, when interlayer positions of Py(15 nm) and β-W(tW) is interchanged irrespective of the fixed top nonmagnetic layer, an increase of αeff is observed, which is ascribed to spin pumping from Py to β-W layer.

  8. Quantum creep in a highly crystalline two-dimensional superconductor

    NASA Astrophysics Data System (ADS)

    Saito, Yu; Kasahara, Yuichi; Ye, Jianting; Iwasa, Yoshihiro; Nojima, Tsutomu

    Conventional studies on quantum phase transitions, especially on superconductor-insulator or superconductor-metal-insulator transitions have been performed in deposited metallic thin films such as Bismuth or MoGe. Although the techniques of thin films deposition have been considerably improved, unintentional disorder such as impurities and deficiencies, generating the pinning centers, seems to still exist in such systems. The mechanical exfoliated highly crystalline two-dimensional material can be a good candidate to realize a less-disordered 2D superconductor with extremely weak pinning, combined with transfer method or ionic-liquid gating. We report on the quantum metal, namely, magnetic-field-induced metallic state observed in an ion-gated two-dimensional superconductor based on an ultra-highly crystalline layered band insulator, ZrNCl. We found that the superconducting state is extremely fragile against external magnetic fields; that is, zero resistance state immediately disappears, once an external magnetic field switches on. This is because the present system is relatively clean and the pinning potential is extremely weak, which cause quantum tunneling and flux flow of vortices, resulting in metallic ground state.

  9. Triplet proximity effect in superconducting heterostructures with a half-metallic layer

    NASA Astrophysics Data System (ADS)

    Mironov, S.; Buzdin, A.

    2015-11-01

    We present the Usadel theory describing the superconducting proximity effect in heterostructures with a half-metallic layer. It is shown that the full spin polarization inside the half-metals gives rise to an additional component of the Green's function which results in the giant triplet spin-valve effect in superconductor (S)-ferromagnet (F)-half-metal (HM) trilayers and provides a natural explanation for the φ0-junction formation in the S/F/HM/F/S systems. In addition, we consider the exactly solvable model of the S/F/HM trilayers of atomic thickness and demonstrate that it reproduces the main features of the spin-valve effect found within the Usadel approach. Our results are shown to be in qualitative agreement with the recent experimental data on the spin-valve effect in MoGe /Ni /Cu /CrO2 hybrids [Singh et al., Phys. Rev. X 5, 021019 (2015), 10.1103/PhysRevX.5.021019].

  10. Doping-dependent critical Cooper-pair momentum pc in thin underdoped cuprate films

    NASA Astrophysics Data System (ADS)

    Lemberger, Thomas; Draskovic, John; Steers, Stanley; McJunkin, Thomas; Anmed, Adam

    2015-03-01

    We apply a low-field (<100 G) technique to measure the critical Cooper pair momentum pc in thin, underdoped films of Y0.7Ca0.3Ba2Cu3O7-δ and Bi2Sr2CaCu2O8+δ, where doping is effected by adjusting the oxygen stoichiometry through post-deposition annealing. The technique is based on applying a perpendicular magnetic field to the center of a superconducting film and measuring the field at which screening of the field catastrophically fails. Theory together with measurements on thin films of conventional superconductors Nb and MoGe argue for the validity of the technique. In underdoped cuprates, spectroscopy identifies multiple characteristic energy scales, e.g., the pseudogap and the ``nodal'' gap, neither of which is proportional to Tc. On general grounds, we expect to find that pc ~ 1/1ξ ξ is proportional to the characteristic superconducting energy scale. We observe that pc ~Tc as Tc decreases with underdoping, identifying kBTc as the characteristic energy. While this result is trivial in conventional superconductors whose spectroscopic gaps are proportional to Tc, it is significant in cuprates. Research supported by DOE-Basic Energy Sciences through Grant No. FG02-08ER46533.

  11. Superconductor-Metal-Insulator transition in two dimensional Ta thin Films

    NASA Astrophysics Data System (ADS)

    Park, Sun-Gyu; Kim, Eunseong

    2013-03-01

    Superconductor-insulator transition has been induced by tuning film thickness or magnetic field. Recent electrical transport measurements of MoGe, Bi, Ta thin films revealed an interesting intermediate metallic phase which intervened superconducting and insulating phases at certain range of magnetic field. Especially, Ta thin films show the characteristic IV behavior at each phase and the disorder tuned intermediate metallic phase [Y. Li, C. L. Vicente, and J. Yoon, Physical Review B 81, 020505 (2010)]. This unexpected metallic phase can be interpreted as a consequence of vortex motion or contribution of fermionic quasiparticles. In this presentation, we report the scaling behavior during the transitions in Ta thin film as well as the transport measurements in various phases. Critical exponents v and z are obtained in samples with wide ranges of disorder. These results reveal new universality class appears when disorder exceeds a critical value. Dynamical exponent z of Superconducting sample is found to be 1, which is consistent with theoretical prediction of unity. z in a metallic sample is suddenly increased to be approximately 2.5. This critical exponent is much larger than the value found in other system and theoretical prediction. We gratefully acknowledge the financial support by the National Research Foundation of Korea through the Creative Research Initiatives.

  12. Quantum melting of a two-dimensional vortex lattice at zero temperature

    SciTech Connect

    Rozhkov, A.; Stroud, D.

    1996-11-01

    We consider the quantum melting of a two-dimensional flux lattice at temperature {ital T} = 0 in the {open_quote}{open_quote}superclean limit.{close_quote}{close_quote} In this regime, we find that vortex motion is dominated by the Magnus force. A Lindemann criterion predicts melting when {ital n}{sub {ital v}}/{ital n}{sub {ital p}}{ge}{beta}, where {ital n}{sub {ital v}} and {ital n}{sub {ital p}} are the areal number densities of vortex pancakes and Cooper pairs, and {beta}{approx_equal}0.1. A second criterion is derived by using Wigner-crystal and Laughlin wave functions for the solid and liquid phases respectively, and setting the two energies equal. This gives a melting value similar to the Lindemann result. We discuss the numerical value of the {ital T}=0 melting field for thin layers of a low-{ital T}{sub {ital c}} superconductor, such as {ital a}-MoGe, and single layers of high-{ital T}{sub {ital c}} materials. {copyright} {ital 1996 The American Physical Society.}

  13. Tungsten diffusion in silicon

    SciTech Connect

    De Luca, A.; Texier, M.; Burle, N.; Oison, V.; Pichaud, B.; Portavoce, A.; Grosjean, C.

    2014-01-07

    Two doses (10{sup 13} and 10{sup 15} cm{sup −2}) of tungsten (W) atoms were implanted in different Si(001) wafers in order to study W diffusion in Si. The samples were annealed or oxidized at temperatures between 776 and 960 °C. The diffusion profiles were measured by secondary ion mass spectrometry, and defect formation was studied by transmission electron microscopy and atom probe tomography. W is shown to reduce Si recrystallization after implantation and to exhibit, in the temperature range investigated, a solubility limit close to 0.15%–0.2%, which is higher than the solubility limit of usual metallic impurities in Si. W diffusion exhibits unusual linear diffusion profiles with a maximum concentration always located at the Si surface, slower kinetics than other metals in Si, and promotes vacancy accumulation close to the Si surface, with the formation of hollow cavities in the case of the higher W dose. In addition, Si self-interstitial injection during oxidation is shown to promote W-Si clustering. Taking into account these observations, a diffusion model based on the simultaneous diffusion of interstitial W atoms and W-Si atomic pairs is proposed since usual models used to model diffusion of metallic impurities and dopants in Si cannot reproduce experimental observations.

  14. Geometry-dependent phase, stress state and electrical properties in nickel-silicide nanowires

    NASA Astrophysics Data System (ADS)

    Wang, C. C.; Lai, W. T.; Hsiao, Y. Y.; Chen, I. H.; George, T.; Li, P. W.

    2016-05-01

    We report that the geometry of single-crystalline Si nanowires (NWs) prior to salicidation at 500 °C is the key factor controlling the phase, stress state, and electrical resistivity of the resulting Ni x Si y NWs of width less than 100 nm. This is a radical departure from previous observations of a single phase formation for nickel silicides generated from the silicidation of bulk Si substrates. The phase transition from NiSi for large NWs ( W Si NW  =  250-450 nm) to Ni2Si for small NWs ( W Si NW  =  70-100 nm) is well correlated with the observed volumetric expansion and electrical resistivity variation with the NW width. For the extremely small dimensions of Ni x Si y NWs, we propose that the preeminent, kinetics-based Zhang and d’Heurle model for salicidation be modified to a more thermodynamically-governed, volume-expansion dependent Ni x Si y phase formation. A novel, plastic deformation mechanism is proposed to explain the observed, geometry-dependent Ni x Si y NW phase formation that also strongly influences the electrical performance of the NWs.

  15. Microstructural transformations and kinetics of high-temperature heterogeneous gasless reactions by high-speed x-ray phase-contrast imaging

    SciTech Connect

    Reeves, Robert V.; Son, Steven F.; White, Jeremiah D. E.; Mukasyan, Alexander S.; Dufresne, Eric M.; Fezzaa, Kamel; Varma, Arvind

    2009-12-01

    Heterogeneous gasless reactive systems, including high-energy density metal-nonmetal compositions, have seen increasing study due to their various applications. However, owing to their high reaction temperature, short reaction time, and small scale of heterogeneity, investigation of their reaction mechanisms and kinetics is very difficult. In this study, microstructural changes and the kinetics of product layer growth in the W-Si system was investigated using a high-speed x-ray phase-contrast imaging technique. Using the Advanced Photon Source of Argonne National Laboratory, this method allowed direct imaging of irreversible reactions in the W-Si reactive system at frame rates up to 36 000 frames per second with 4 {mu}s exposure and spatial resolution of 10 {mu}m. Details of the Si melt and reactions between W and Si, that are unable to be viewed with visible-light imaging, were revealed. These include processes such as the initiation of nucleated melting and other physical phenomena that provide insight into the mixing of reactants and subsequent reaction. Through the use of this imaging technique and future optimization in the imaging process, a model for accurately identifying kinetics of chemical reactions, both spatially and temporally, is also proposed.

  16. Dissolution of Al2TiO5 inclusions in CaO-SiO2-Al2O3 slags at 1823 K

    NASA Astrophysics Data System (ADS)

    Wang, De-Yong; Liu, Jun; Jiang, Mao-Fa; Tsukihashi, Fumitaka; Matsuura, Hiroyuki

    2011-12-01

    Al-Ti-O inclusions always clog submerged nozzles in Ti-bearing Al-killed steel. A typical synthesized Al2TiO5 inclusion was immersed in a CaO-SiO2-Al2O3 molten slag for different durations at 1823 K. The Al2TiO5 dissolution paths and mechanism were revealed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Decreased amounts of Ti and Al and increased amounts of Si and Ca at the dissolution boundary prove that inclusion dissolution and slag penetration simultaneously occur. SiO2 diffuses or penetrates the inclusion more quickly than CaO, as indicated by the w(CaO)/ w(SiO2) value in the reaction region. A liquid product (containing 0.7-1.2 w(CaO)/ w(SiO2), 15wt%-20wt% Al2O3, and 5wt%-15wt% TiO2) forms on the inclusion surface when Al2TiO5 is dissolved in the slag. Al2TiO5 initially dissolves faster than the diffusion rate of the liquid product toward the bulk slag. With increasing reaction time, the boundary reaches its largest distance, the Al2TiO5 dissolution rate equals the liquid product diffusion rate, and the dissolution process remains stable until the inclusion is completely dissolved.

  17. Development and characterization of coatings on silicon pore optics substrates for the ATHENA Mission

    NASA Astrophysics Data System (ADS)

    Ferreira, Desiree Della Monica; Jakobsen, Anders C.; Christensen, Finn E.; Shortt, Brian J.; Krumrey, Michael; Garnæs, Jørgen; Simonsen, Ronni B.

    2012-09-01

    We present description and results of the test campaign performed on Silicon Pore Optics (SPO) samples to be used on the ATHENA mission. We perform a pre-coating characterization of the substrates using Atomic Force Microscopy (AFM), X-ray Re ectometry (XRR) and scatter measurements. X-ray tests at DTU Space and correlation between measured roughness and pre-coating characterization are reported. For coating development, a layer of Cr was applied underneath the Ir/B4C bi-layer with the goal of reducing stress, and the use of N2 during the coating process was tested in order to reduce the surface roughness in the coatings. Both processes show promising results. Measurements of the coatings were carried out at the 8 keV X-ray facility at DTU Space and with synchrotron radiation in the laboratory of PTB at BESSY II to determine re ectivity at the grazing incidence angles and energies of ATHENA. Coating development also included a W/Si multilayer coating. We present preliminary results on X-ray Re ectometry and Cross-sectional Transmission Electron Microscopy (TEM) of the W/Si multilayer.

  18. Adaptive x-ray optics with a deformable mirror

    NASA Astrophysics Data System (ADS)

    Kitamoto, Shunji; Yamamoto, Norimasa; Kohmura, Takayoshi; Suga, Kazuharu; Sekiguchi, Hiroyuki; Sato, Jun'ichi; Sudo, Keisuke; Watanabe, Takeshi; Ohkubo, Youhei; Sekiguchi, Akiko; Tsujimoto, Masahiro

    2005-08-01

    We are developing a soft x-ray telescope with an adaptive optics system for future astronomical observation with very fine angular resolution of an order of milli-arc-second. From a technical point of view, we are trying to develop a normal incident telescope with multi layers. Thus the wave length is limited to be around 13.5 nm with a band pass of roughly 1nm. Since the x-ray telescope must be installed on a satellite, a stable conditions of temperature, gravity etc, can not be expected. Therefore, we investigate to use an adaptive optics system using an optical light source attached in the telescope. In this paper, we report our present status of the development. The primary mirror is an off-axis paraboloid with 80 mm effective diameter and 2 m focal length. This mirror has been coated with Mo/Si multi-layers. The reflectivity of the 13.5 nm x rays is ranging from 35% to 55%. We use a deformable mirror for the secondary mirror, which has also been coated with Mo/Si multi-layers. This mirror consists of 31 element-bimorph-piezo electrodes. The surface roughness of the mirror is ~6 nm rms. The reflectivity of the 13.5 nm x rays is roughly 65%. The adaptive optics system using an optical laser and a wave front sensor has been performed. We are using a shack-hartmann sensor (HASO 32) with a micro-lens array and a CCD. A pin hole with one micron diameter is used for the optical light source. The precision of the measurement of the wave front shape is a few nm. X-ray exposure test is now conducting, although the optical adaptive optics system is not yet installed. The x-ray detector is a back illumination CCD. The quantum efficiency for 13.5 nm x ray is ~50%. The pixel size is 24 micron square. X-ray source is an electron impact source with an Al/Si alloy target. We confirmed that the x-ray intensity around 13.55 nm is bright enough for our experiment. The imaging performance is now trying to improve and the adaptive optics system will be installed in this year.

  19. Processing, Compatibility and Oxidation of Diboride - Oxide Matrix Composites for Ultrahigh-Temperature Applications.

    NASA Astrophysics Data System (ADS)

    Abada, Ahmed

    1990-01-01

    Promising results for the development of a ceramic/ceramic composite to be used for structural applications in the ultra high temperature range (1650-1850^ circC) have been obtained for alumina reinforced with titanium or zirconium diboribe coated with molybdenum disilicide. Prior to this achievement, several theoretical and experimental studies of particulate composites with (TiB_2 or ZrB_2) imbedded in (ZrO_2, Y_2 O_3 or Al_2 O_3) were conducted. Calculations of the compatibility and stability of oxide matrices with the diborides in vacuum showed positive energies of formation, indicating suitability of reinforcement of alumina under vacuum conditions. Also, since the sublimation of vapor species at ultra high temperatures is very critical to the stability of substances still existing in their condensed states, a detailed thermodynamic analysis of the metal -oxygen systems, was carried out using elemental data of the TiB_2, ZrB_2 , ZrO_2, Y_2 O_3, Al_2 O_3, MoSi_2 and their combinations (TiB_2 or ZrB_2)/(ZrO_2 , Y_2O_3 or Al_2O_3) for comparison, at 1650, 1850 and 2050^ circC. A comparison of the combination TiB _2 and ZrB_2 in MoSi_2/(Al_2O _3 or ZrO_2) at 1650^circC was also made. A stability analysis using equilibrium oxygen partial pressures for the TiB_2 and ZrB_2 decomposition at 1650, 1850 and 2050^ circC was carried out. A detailed characterization of the powders used for the oxide matrices, the diborides and the molybdenum disilicide are presented. The effects of the powder characteristics and the vacuum hot pressing parameters on the densification of the composites are discussed. Stability and chemical compatibility of the particulate and ternary composites in their as hot pressed states and following their vacuum and air oxidation treatments were characterized. Interdiffusion of elemental species across diboride/disilicide and oxide/disilicide interfaces was studies by EDS dot mapping. It is proposed that the growth of the Mo _5Si_3 is interface

  20. Extreme ultraviolet lithography mask etch study and overview

    NASA Astrophysics Data System (ADS)

    Wu, Banqiu; Kumar, Ajay; Chandrachood, Madhavi; Sabharwal, Amitabh

    2013-04-01

    An overview of extreme ultraviolet lithography (EUVL) mask etch is presented and a EUVL mask etch study was carried out. Today, EUVL implementation has three critical challenges that hinder its adoption: extreme ultraviolet (EUV) source power, resist resolution-line width roughness-sensitivity, and a qualified EUVL mask. The EUVL mask defect challenges result from defects generated during blank preparation, absorber and multilayer deposition processes, as well as patterning, etching and wet clean processes. Stringent control on several performance criteria including critical dimension (CD) uniformity, etch bias, micro-loading, profile control, defect control, and high etch selectivity requirement to capping layer is required during the resist pattern duplication on the underlying absorber layer. EUVL mask absorbers comprise of mainly tantalum-based materials rather than chrome- or MoSi-based materials used in standard optical masks. Compared to the conventional chrome-based absorbers and phase shift materials, tantalum-based absorbers need high ion energy to obtain moderate etch rates. However, high ion energy may lower resist selectivity, and could introduce defects. Current EUVL mask consists of an anti-reflective layer on top of the bulk absorber. Recent studies indicate that a native oxide layer would suffice as an anti-reflective coating layer during the electron beam inspection. The absorber thickness and the material properties are optimized based on optical density targets for the mask as well as electromagnetic field effects and optics requirements of the patterning tools. EUVL mask etch processes are modified according to the structure of the absorber, its material, and thickness. However, etch product volatility is the fundamental requirement. Overlapping lithographic exposure near chip border may require etching through the multilayer, resulting in challenges in profile control and etch selectivity. Optical proximity correction is applied to further

  1. Multilayer Optics for Ultra-high Resolution Solar Imaging in the EUV Region

    NASA Astrophysics Data System (ADS)

    Soufli, R.; Spiller, E.; Sommargren, G. E.; Bajt, S.; Folta, J. A.; Taylor, J. S.; Gullikson, E. M.

    2003-05-01

    Highly reflective multilayer-coated optics operating at near-normal incidence angles have been the enabling technology for solar imaging instruments in the extreme ultraviolet (EUV) energy range. Despite the advances made in recent years towards understanding of solar processes through missions such as TRACE, major unresolved questions in solar physics still remain, for instance on the subjects of coronal heating, eruptive flare and coronal wind initiation. Future generations of missions will need to study the physics of hot magnetized plasmas that occur in the corona on extremely small spatial and temporal scales, requiring imaging instruments with extremely high resolution and large fields of view. Proposals for future solar missions require optics with diameters up to 700 mm and system wavefront errors as low as 0.4 nm. Experimental results will be presented for normal-incidence, four-mirror and two-mirror EUV cameras operating around 13.4 nm. Mirror substrates were manufactured by commercial vendors and achieved figure errors around 0.25 nm rms, verified by phase-shifting, point-diffraction visible light interferometers developed at Lawrence Livermore Lab. The optics were multilayer-coated aligned and tested at facilities at Lawrence Livermore and Lawrence Berkeley National Labs. A large-scale DC-magnetron sputtering tool is used to coat the optics and can accommodate multiple optics up to 600 mm in diameter in a single deposition run. During multilayer deposition, a velocity modulation algorithm is applied in order to achieve extremely precise film thickness control. The deposited Mo/Si coatings demonstrate added figure errors below 0.05 nm rms. While these systems were constructed for EUV lithographic applications, the experimental results are immediately applicable to astronomical x-ray optics. Currently these are the only multilayer-coated EUV cameras worldwide meeting such stringent specifications, and have been implemented in the construction of the first

  2. Electron beam inspection of 16nm HP node EUV masks

    NASA Astrophysics Data System (ADS)

    Shimomura, Takeya; Narukawa, Shogo; Abe, Tsukasa; Takikawa, Tadahiko; Hayashi, Naoya; Wang, Fei; Ma, Long; Lin, Chia-Wen; Zhao, Yan; Kuan, Chiyan; Jau, Jack

    2012-11-01

    EUV lithography (EUVL) is the most promising solution for 16nm HP node semiconductor device manufacturing and beyond. The fabrication of defect free EUV mask is one of the most challenging roadblocks to insert EUVL into high volume manufacturing (HVM). To fabricate and assure the defect free EUV masks, electron beam inspection (EBI) tool will be likely the necessary tool since optical mask inspection systems using 193nm and 199nm light are reaching a practical resolution limit around 16nm HP node EUV mask. For production use of EBI, several challenges and potential issues are expected. Firstly, required defect detection sensitivity is quite high. According to ITRS roadmap updated in 2011, the smallest defect size needed to detect is about 18nm for 15nm NAND Flash HP node EUV mask. Secondly, small pixel size is likely required to obtain the high sensitivity. Thus, it might damage Ru capped Mo/Si multilayer due to accumulated high density electron beam bombardments. It also has potential of elevation of nuisance defects and reduction of throughput. These challenges must be solved before inserting EBI system into EUV mask HVM line. In this paper, we share our initial inspection results for 16nm HP node EUV mask (64nm HP absorber pattern on the EUV mask) using an EBI system eXplore® 5400 developed by Hermes Microvision, Inc. (HMI). In particularly, defect detection sensitivity, inspectability and damage to EUV mask were assessed. As conclusions, we found that the EBI system has capability to capture 16nm defects on 64nm absorber pattern EUV mask, satisfying the sensitivity requirement of 15nm NAND Flash HP node EUV mask. Furthermore, we confirmed there is no significant damage to susceptible Ru capped Mo/Si multilayer. We also identified that low throughput and high nuisance defect rate are critical challenges needed to address for the 16nm HP node EUV mask inspection. The high nuisance defect rate could be generated by poor LWR and stitching errors during EB writing

  3. Spectroscopy of highly charged ions and its relevance to EUV and soft x-ray source development

    NASA Astrophysics Data System (ADS)

    O'Sullivan, Gerry; Li, Bowen; D'Arcy, Rebekah; Dunne, Padraig; Hayden, Paddy; Kilbane, Deirdre; McCormack, Tom; Ohashi, Hayato; O'Reilly, Fergal; Sheridan, Paul; Sokell, Emma; Suzuki, Chihiro; Higashiguchi, Takeshi

    2015-07-01

    The primary requirement for the development of tools for extreme ultraviolet lithography (EUVL) has been the identification and optimization of suitable sources. These sources must be capable of producing hundreds of watts of extreme ultraviolet (EUV) radiation within a wavelength bandwidth of 2% centred on 13.5 nm, based on the availability of Mo/Si multilayer mirrors (MLMs) with a reflectivity of ˜70% at this wavelength. Since, with the exception of large scale facilities, such as free electron lasers, such radiation is only emitted from plasmas containing moderately to highly charged ions, the source development prompted a large volume of studies of laser produced and discharge plasmas in order to identify which ions were the strongest emitters at this wavelength and the plasma conditions under which their emission was optimized. It quickly emerged that transitions of the type 4p64dn - 4p54dn+1 + 4dn-14f in the spectra of Sn IX to SnXIV were the best candidates and work is still ongoing to establish the plasma conditions under which their emission at 13.5 nm is maximized. In addition, development of other sources at 6.X nm, where X ˜ 0.7, has been identified as the wavelength of choice for so-called Beyond EUVL (BEUVL), based on the availability of La/B based MLMs, with theoretical reflectance approaching 80% at this wavelength. Laser produced plasmas of Gd and Tb have been identified as potential source elements, as n = 4 - n = 4 transitions in their ions emit strongly near this wavelength. However to date, the highest conversion efficiency (CE) obtained, for laser to BEUV energy emitted within the 0.6% wavelength bandwidth of the available mirrors is only 0.8%, compared with values of 5% for the 2% bandwidth relevant for the Mo/Si mirrors at 13.5 nm. This suggests a need to identify other potential sources or the selection of other wavelengths for BEUVL. This review deals with the atomic physics of the highly-charged ions relevant to EUV emission at these

  4. Vortex Dynamics in Anisotropic Superconductors

    NASA Astrophysics Data System (ADS)

    Steel, David Gordon

    Measurements of the ac screening response and resistance of superconducting Bi_2Sr _2CaCu_2O _8 (BSCCO) crystals have been used to probe the dynamics of the magnetic flux lines within the mixed state as a function of frequency, temperature, and applied dc field. For the particular range of temperature and magnetic field in which measurements were made, the systematic behavior of the observed dissipation peak in the screening response is consistent with electromagnetic skin size effects rather than a phase transition. According to microscopic theories of the interaction between the flux lines and a driving ac field, such a skin size effect is expected for the case when the vortex motion is diffusive in nature. However, diffusive motion is inconsistent with simple activation models that use a single value for the pinning energy (derived from direct measurement of the dc resistance). This contradiction suggests a distribution of pinning energies within the sample. Interlayer vortex decoupling has been directly observed as a function of temperature and applied magnetic field using electronic transport perpendicular to the layers in synthetic amorphous MoGe/Ge multilayer samples. Perpendicular transport has been shown to be a far more sensitive measure of the phase coupling between layers than in-plane properties. Below the decoupling temperature T_{D} the resistivity anisotropy collapses and striking nonlinearities appear in the perpendicular current-voltage behavior, which are not observed in parallel transport. A crossover in behavior is also observed at a field H _{x}, in accordance with theory. The data suggest the presence of a phase transition into a state with finite in-plane resistivity. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.).

  5. Interlaced X-ray diffraction computed tomography

    PubMed Central

    Vamvakeros, Antonios; Jacques, Simon D. M.; Di Michiel, Marco; Senecal, Pierre; Middelkoop, Vesna; Cernik, Robert J.; Beale, Andrew M.

    2016-01-01

    An X-ray diffraction computed tomography data-collection strategy that allows, post experiment, a choice between temporal and spatial resolution is reported. This strategy enables time-resolved studies on comparatively short timescales, or alternatively allows for improved spatial resolution if the system under study, or components within it, appear to be unchanging. The application of the method for studying an Mn–Na–W/SiO2 fixed-bed reactor in situ is demonstrated. Additionally, the opportunities to improve the data-collection strategy further, enabling post-collection tuning between statistical, temporal and spatial resolutions, are discussed. In principle, the interlaced scanning approach can also be applied to other pencil-beam tomographic techniques, like X-ray fluorescence computed tomography, X-ray absorption fine structure computed tomography, pair distribution function computed tomography and tomographic scanning transmission X-ray microscopy. PMID:27047305

  6. Investigation of Miniaturized Radioisotope Thermionic Power Generation for General Use

    NASA Technical Reports Server (NTRS)

    Duzik, Adam J.; Choi, Sang H.

    2016-01-01

    Radioisotope thermoelectric generators (RTGs) running off the radioisotope Pu238 are the current standard in deep space probe power supplies. While reliable, these generators are very inefficient, operating at only approx.7% efficiency. As an alternative, more efficient radioisotope thermionic emission generators (RTIGs) are being explored. Like RTGs, current RTIGs concepts use exotic materials for the emitter, limiting applicability to space and other niche applications. The high demand for long-lasting mobile power sources would be satisfied if RTIGs could be produced inexpensively. This work focuses on exposing several common materials, such as Al, stainless steel, W, Si, and Cu, to elevated temperatures under vacuum to determine the efficiency of each material as inexpensive replacements for thermoelectric materials.

  7. Production and performance of multilayer-coated conical x-ray mirrors.

    PubMed

    Ulmer, Melville P; Altkorn, Robert; Graham, Michael E; Madan, Anita; Chu, Yong S

    2003-12-01

    A method of fabricating replica figured x-ray optics with integral multilayer coatings is presented. With the intact electroforming multilayer process (IEMP) technique, we sputter multilayers onto a reusable superpolished mandrel, electroform nickel over the multilayers, and remove the multilayer-coated nickel shell intact from the mandrel. This approach offers advantages over more traditional, original, and segmented-replica fabrication techniques, including low cost; compatibility with a wide range of mirror designs, diameters, and focal lengths; simple integration with multilayer sputtering processes; and the ability to produce complete shells of revolution. The fabrication of W/Si multilayer-coated 10-cm-diameter conical x-ray mirrors is described, as are reflectivity measurements at 10 and 30 keV. The measured reflectivity of the IEMP multilayers at the 10-keV primary Bragg peak was 17%. Measurements of multiple points on the cone showed multilayer uniformity to within a few percent around the mirror.

  8. Laser ablation inductively coupled plasma mass spectrometry for direct analysis of the spatial distribution of trace elements in metallurgical-grade silicon.

    PubMed

    Pisonero, Jorge; Kroslakova, Ivana; Günther, Detlef; Latkoczy, Christopher

    2006-09-01

    The spatial distribution and concentration of impurities in metallurgical-grade silicon (MG-Si) samples (97-99% w/w Si) were investigated by use of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The spatial resolution (120 mum) and low limits of detection (mg kg(-1)) for quality assurance of such materials were studied in detail. The volume-dependent precision and accuracy of non-matrix-matched calibration for quantification of minor elements, using NIST SRM 610 (silicate standard), indicates that LA-ICP-MS is well suited to rapid process control of such materials. Quantitative results from LA-ICP-MS were compared with previously reported literature data obtained by use of ICP-OES and rf-GD-OES. In particular, the distribution of element impurities and their relationship to their different segregation coefficients in silicon is demonstrated.

  9. Tests of variable-band multilayers designed for investigating optimal signal-to-noise vs artifact signal ratios in Dual-Energy Digital Subtraction Angiography (DDSA) imaging systems

    SciTech Connect

    Boyers, D.; Ho, A.; Li, Q.; Piestrup, M.; Rice, M.; Tatchyn, R.

    1993-08-01

    In recent work, various design techniques were applied to investigate the feasibility of controlling the bandwidth and bandshape profiles of tungsten/boron-carbon (W/B{sub 4}C) and tungsten/silicon (W/Si) multilayers for optimizing their performance in synchrotron radiation based angiographical imaging systems at 33 keV. Varied parameters included alternative spacing geometries, material thickness ratios, and numbers of layer pairs. Planar optics with nominal design reflectivities of 30%--94% and bandwidths ranging from 0.6%--10% were designed at the Stanford Radiation Laboratory, fabricated by the Ovonic Synthetic Materials Company, and characterized on Beam Line 4-3 at the Stanford Synchrotron Radiation Laboratory, in this paper we report selected results of these tests and review the possible use of the multilayers for determining optimal signal to noise vs. artifact signal ratios in practical Dual-Energy Digital Subtraction Angiography systems.

  10. Non-selective tungsten CVD using tungsten hexacarbonyl

    SciTech Connect

    Creighton, J.R.

    1987-01-01

    We have used tungsten hexacarbonyl to deposit thin (<1000 A) non-selective tungsten films on silicon and silicon dioxide at 550/sup 0/C. Thicker (approx. =1 micron) tungsten films were then deposited using conventional H/sub 2/ reduction of WF/sub 6/ at 470/sup 0/C using the non-selective film as an adhesion layer. Films grown in this manner have excellent adhesion to SiO/sub 2/, essentially 100% step coverage, and good resistivity. Samples could be transferred under vacuum from the deposition chamber to a uhv chamber equipped with Aguer spectroscopy, thus allowing surface and interface properties of the tungsten films to be studied at the initial stages of growth. No evidence was found for a stoichiometric tungsten oxide or tungsten silicide at the W/SiO/sub 2/ interface. 13 refs., 4 figs.

  11. Non-selective tungsten chemical-vapor deposition using Tungsten hexacarbonyl

    SciTech Connect

    Creighton, J.R.

    1988-09-15

    We have used tungsten hexacarbonyl to deposit thin (<1000 A) non-selective tungsten films on silicon and silicon dioxide at 550/sup 0/C. Thicker (greater than or equal to1 micron) tungsten films were then deposited using film as an adhesion layer. Films grown in this manner have excellent adhesion to SiO/sub 2/, essentially 100% step coverage, and good resistivity (7.5--14 ..mu cap omega..-cm). Samples could be transferred under vacuum from the deposition chamber to a UHV chamber equipped with Auger spectroscopy, thus allowing surface and interface properties of the tungsten films to be studied at the initial stages of growth. No evidence was found for a stoichiometric tungsten oxide or tungsten silicide at the W/SiO/sub 2/ interface.

  12. Selective deposition of tungsten on ITM-CoSi 2

    NASA Astrophysics Data System (ADS)

    Kähler, J. D.; Depta, D.; Ferretti, R.

    1995-10-01

    In the present work a silane reduced selective tungsten deposition on ITM processed SALICIDE CoSi 2 was evaluated. The contact resistance of W/CoSi 2/Si contacts are lower compared to W/Si contacts. CoSi 2 was formed by a selective silicide formation process using a single RTA step. During the ion implantation the interface between cobalt and silicon was mixed up and a possible native oxide has been cracked. This promotes a better metal-silicon reaction. Contact resistance and sheet resistance measurements were performed using Kelvin structures (CBKR) and contact chains or van der Pauw structures, respectively. A processing window was determined with respect to a good selectivity and low contact resistances. SIMS measurements were made in order to investigate the influence of the flow ratio of SiH 4/WF 6 on the sheet resistance.

  13. Silicon Carbide (SiC) Power Processing Unit (PPU) for Hall Effect Thrusters

    NASA Technical Reports Server (NTRS)

    Reese, Bradley

    2015-01-01

    Arkansas Power Electronics International (APEI), Inc., is developing a high-efficiency, radiation-hardened 3.8-kW SiC power supply for the PPU of Hall effect thrusters. This project specifically targets the design of a PPU for the high-voltage Hall accelerator (HiVHAC) thruster, with target specifications of 80- to 160-V input, 200- to 700-V/5A output, efficiency greater than 96 percent, and peak power density in excess of 2.5 kW/kg. The PPU under development uses SiC junction field-effect transistor power switches, components that APEI, Inc., has irradiated under total ionizing dose conditions to greater than 3 MRad with little to no change in device performance.

  14. Investigation of miniaturized radioisotope thermionic power generation for general use

    NASA Astrophysics Data System (ADS)

    Duzik, Adam J.; Choi, Sang H.

    2016-04-01

    Radioisotope thermoelectric generators (RTGs) running off the radioisotope Pu238 are the current standard in deep space probe power supplies. While reliable, these generators are very inefficient, operating at only ~7% efficiency. As an alternative, more efficient radioisotope thermionic emission generators (RTIGs) are being explored. Like RTGs, current RTIGs concepts use exotic materials for the emitter, limiting applicability to space and other niche applications. The high demand for long-lasting mobile power sources would be satisfied if RTIGs could be produced inexpensively. This work focuses on exposing several common materials, such as Al, stainless steel, W, Si, and Cu, to elevated temperatures under vacuum to determine the efficiency of each material as inexpensive replacements for thermoelectric materials.

  15. A poly(vinylidene fluoride)-coated ZnO film bulk acoustic resonator for nerve gas detection

    NASA Astrophysics Data System (ADS)

    Chen, Da; Wang, Jingjing; Li, Dehua; Liu, Yijian; Song, Hongwei; Liu, Qixin

    2011-08-01

    We apply the film bulk acoustic resonator for the detection of nerve gas. The resonator is consisted of a ZnO piezoelectric stack and a W/SiO2 Bragg reflector. Poly(vinylidene fluoride) (PVDF) is used as the sensing coating to adsorb the analyte under test. The testing results show that our proposed sensor can yield a sensitive, reversible and reproducible response to nerve gas. The relationship between the frequency shifts and the concentrations of the nerve gas exhibits a perfect linear correlation in the range of 10-50 ppm. The gas sensitivity of the proposed sensor is 718 kHz ppm-1, which is several orders of magnitude higher than that of a quartz crystal microbalance with the same sensitive coating. This study proves that it is feasible to use the PVDF-coated thin film bulk acoustic resonator for the detection of the traced nerve gas.

  16. X-ray mirror development and testing for the ATHENA mission

    NASA Astrophysics Data System (ADS)

    Della Monica Ferreira, Desiree; Jakobsen, Anders C.; Massahi, Sonny; Christensen, Finn E.; Shortt, Brian; Garnæs, Jørgen; Torras-Rosell, Antoni; Krumrey, Michael; Cibik, Levent; Marggraf, Stefanie

    2016-07-01

    This study reports development and testing of coatings on silicon pore optics (SPO) substrates including pre and post coating characterisation of the x-ray mirrors using Atomic Force Microscopy (AFM) and X-ray reflectometry (XRR) performed at the 8 keV X-ray facility at DTU Space and with synchrotron radiation in the laboratory of PTB at BESSY II. We report our findings on surface roughness and coating reflectivity of Ir/B4C coatings considering the grazing incidence angles and energies of ATHENA and long term stability of Ir/B4C, Pt/B4C, W/Si and W/B4C coatings.

  17. Interlaced X-ray diffraction computed tomography.

    PubMed

    Vamvakeros, Antonios; Jacques, Simon D M; Di Michiel, Marco; Senecal, Pierre; Middelkoop, Vesna; Cernik, Robert J; Beale, Andrew M

    2016-04-01

    An X-ray diffraction computed tomography data-collection strategy that allows, post experiment, a choice between temporal and spatial resolution is reported. This strategy enables time-resolved studies on comparatively short timescales, or alternatively allows for improved spatial resolution if the system under study, or components within it, appear to be unchanging. The application of the method for studying an Mn-Na-W/SiO2 fixed-bed reactor in situ is demonstrated. Additionally, the opportunities to improve the data-collection strategy further, enabling post-collection tuning between statistical, temporal and spatial resolutions, are discussed. In principle, the interlaced scanning approach can also be applied to other pencil-beam tomographic techniques, like X-ray fluorescence computed tomography, X-ray absorption fine structure computed tomography, pair distribution function computed tomography and tomographic scanning transmission X-ray microscopy.

  18. Influence of Basicity and MgO on Fluidity and Desulfurization Ability of High Aluminum Slag

    NASA Astrophysics Data System (ADS)

    Wang, Ping; Meng, Qing-min; Long, Hong-ming; Li, Jia-xin

    2016-08-01

    The viscosity of experimental slag, which was mixed based on the composition of a practical blast furnace slag, was measured in this paper. The influence of Al2O3 and MgO content, basicity R2 = w(CaO)/w(SiO2) on the fluidity of slag was studied. The stepwise regression analysis in SPSS was used to reveal the relationship between sulfur distribution coefficient LS and slag composition as well as furnace temperature. The results show that increasing of MgO up to 12% can decrease the slag viscosity. The w(MgO) should be controlled below 8% when there is 20% Al2O3 in the slag. Temperature of hot metal and content of CaO in slag are the two dominant factors on the desulfurization capacity of slag.

  19. Development of advanced multi-tone mask by using two different transmittance modulation materials

    NASA Astrophysics Data System (ADS)

    Kim, Sei-Min; Choi, Min-Ki; Seo, Seong-Min; Lee, Jong-Hwa; Shin, Cheol; Jeong, Woo-Gun; Jung, Sung-Mo; Nam, Kee-Soo

    2016-09-01

    Multi-tone mask (MTM) consists of more than two layers having different transmittance modulation layers. A novel method is proposed to manufacture a MTM based on two kinds of transmittance modulation materials such as chromium and molybdenum. Different modulation materials cannot be only act as etch-stopper to each other, but also they play a role as a separator between the layers consisted of MTM. Furthermore, clearly classified modulation layers contribute to define one of the targeted transmittance according to different etching process. Especially, a conventional MTM requires three mask writing processes to form three patterns whereas the proposed MTM structure makes it possible to form three patterns by using only two mask writing processes. It is found that the turnaround time of proposed MTM is remarkably decreased as value of 30% compared to that of conventional MTM. MoSi-/Cr-based tri-tone mask configuration having 37, 15, and 0% of transmittance had been demonstrated based on the optimized thin-film conditions. Optical uniformity characteristics were also carried out to evaluate the photomask performance. Consequently, the proposed MTM is not only expected to extend the variation of objective transmittance, but also it is a very promise method for achieving a high performance photo-mask by reducing its fabrication cost.

  20. Imaging performance improvement of coherent extreme-ultraviolet scatterometry microscope with high-harmonic-generation extreme-ultraviolet source

    NASA Astrophysics Data System (ADS)

    Mamezaki, Daiki; Harada, Tetsuo; Nagata, Yutaka; Watanabe, Takeo

    2017-06-01

    In extreme-ultraviolet (EUV) lithography, the development of a review apparatus for the EUV mask pattern at an exposure wavelength of 13.5 nm is required. The EUV mask is composed of an absorber pattern and a Mo/Si multilayer on a glass substrate. This mask pattern has a three-dimensional (3D) structure. The 3D structure would modulate the EUV reflection phase, which would cause focus and pattern shifts. Thus, the review of the EUV phase image is also important. We have developed a coherent EUV scatterometry microscope (CSM), which is a simple microscope without objective optics. The EUV phase and intensity images were reconstructed with diffraction images by ptychography. For a standalone mask review, the high-harmonic-generation (HHG) EUV source was employed. In this study, we updated the sample stage, pump-laser reduction system, and gas-pressure control system to reconstruct the image. As a result, an 88 nm line-and-space pattern and a cross-line pattern were reconstructed. In addition, a particle defect of 2 µm diameter was well reconstructed. This demonstrated the high capability of the standalone CSM, which can hence be used in factories, such as mask shops and semiconductor fabrication plants.

  1. Fabrication of SiC whiskers and composites

    SciTech Connect

    Hurley, G.F.; Shalek, P.D.; Gac, F.D.; Petrovic, J.J.

    1984-01-01

    The Los Alamos Structural Ceramics Program is a multi-faceted program with an overall objective of producing superior strength and fracture toughness in ceramic bodies for load bearing applications. One phase of the program is pursuing the development of silicon carbide whiskers which are used to prepare ceramic matrix composites. The purpose of this work is to investigate strengthening and toughening mechanisms in ceramic composites. In the following we describe some elements of the whisker development program in which we are endeavoring better to characterize the whisker growth process in order to scale up its production potential. We have used these whiskers in the preparation of four types of ceramic matrix representative of a range of materials. The nature and reasons for choosing these materials are described. Composites have been prepared by dry-blending followed by hot pressing which yields high density bodies. In addition we are beginning an investigation of wet processing (slip casting) to produce a silicon-silicon carbide body which will be reaction sintered in nitrogen. Composites of glass-, hot pressed silicon nitride -, and molybdenum disilicide - silicon carbide whiskers have been tested in flexure to determine strength and fracture toughness. Results have been promising, with substantial toughening exhibited in all systems, and strengthening in the glass and MoSi/sub 2/ composites. The reaction bonded silicon nitride is not yet to the testing stage.

  2. Microstructure and Properties of HVOF-Sprayed Ni-50Cr Coatings

    SciTech Connect

    Joel A. Simpson; Terry C. Totemeier; Richard N. Wright

    2006-06-01

    Thermal spray coatings represent a potential cost-effective means of protecting structural components in advanced fossil energy systems. Previous work at the INL has focused on relationships between thermal spray processing conditions, structure, and properties in alumina- and silica-forming coatings, namely Fe3Al, FeAl, and Mo-Si-B alloys. This paper describes the preparation and characterization of chromia-forming Ni-50%Cr coatings, an alloy similar to the INCOCLAD 671 cladding, which has shown excellent performance in the Niles Plant service tests. The structure and properties of Ni-50Cr coatings are similar to other HVOF-sprayed metallic coatings: a typical lamellar microstructure is observed with essentially no porosity and little oxide. The microhardness and compressive residual stress both increase with increased spray particle velocity. Corrosion tests were performed on a variety of free-standing coatings (removed from the substrate, wrought Fe3Al alloy, and Grade 91 steel in a simulated coal combustion gas (N2-10%CO-5%CO2-2%H2O-0.12%H2S) and gas-slag environments (same gas, with iron sulfide powder in contact with the coating surface). The coatings tested included Fe3Al, FeAl, and Ni-50Cr alloys sprayed at different velocities. In these tests the iron aluminides in wrought and coating form showed the best performance, with Ni-50Cr coatings slightly worse; the Grade 91 steel was severely attacked.

  3. X-ray beamsplitter

    DOEpatents

    Ceglio, N.M.; Stearns, D.G.; Hawryluk, A.M.; Barbee, T.W. Jr.

    1987-08-07

    An x-ray beamsplitter which splits an x-ray beam into two coherent parts by reflecting and transmitting some fraction of an incident beam has applications for x-ray interferometry, x-ray holography, x-ray beam manipulation, and x-ray laser cavity output couplers. The beamsplitter is formed of a wavelength selective multilayer thin film supported by a very thin x-ray transparent membrane. The beamsplitter resonantly transmits and reflects x-rays through thin film interference effects. A thin film is formed of 5--50 pairs of alternate Mo/Si layers with a period of 20--250 A. The support membrane is 10--200 nm of silicon nitride or boron nitride. The multilayer/support membrane structure is formed across a window in a substrate by first forming the structure on a solid substrate and then forming a window in the substrate to leave a free-standing structure over the window. 6 figs.

  4. CD measurement point extraction from local dense patterns

    NASA Astrophysics Data System (ADS)

    Miyajima, Masaaki; Matsumoto, Hiroyuki; Takeuchi, Kanji; Naoe, Mitsufumi; Hosono, Koji; Miyauchi, Toru

    2015-07-01

    Precision control of critical dimensions (CD) in modern photomask manufacturing is conventionally accomplished by measuring of CD check patterns allocated inside photomask area. Recently, due to use of immersion and High-NA processes for ArF scanners surface of photomask is subjected to higher energy exposure. Such high energy exposure not only increases the loading effect and the flare but also brings about additional issues such as Cr migration and degradation of MoSi film quality due to its surface oxidation which become a new source of CD deviation. Such phenomenon influence both local pattern shape and its dependence on pattern density and global pattern density and arrangement. To achieve good control of CD in such global environment it is required to measure patterns in the chip device area equivalent to CD check patterns allocated on that chip. However, it is extremely difficult to accurately extract coordinates of patterns for CD measurements inside large device of the chip. We have developed a system in which firstly, using design rule check (DRC) method we extract from the chip device area simple line and space (L/S) patterns similar to CD check patterns and secondly, after bitmap transformation of the extraction result use a convolution operation approach to determine the patterns to measure. We confirmed that our method enables selection of CD measurement points with good reproducibility and stability. Next, we report on details of our method to extract CD measurement points and demonstrate its usefulness due to its excellent reproducibility and stability.

  5. Lasers, extreme UV and soft X-ray

    SciTech Connect

    Nilsen, Joseph

    2015-09-20

    Three decades ago, large ICF lasers that occupied entire buildings were used as the energy sources to drive the first X-ray lasers. Today X-ray lasers are tabletop, spatially coherent, high-repetition rate lasers that enable many of the standard optical techniques such as interferometry to be extended to the soft X-ray regime between wavelengths of 10 and 50 nm. Over the last decade X-ray laser performance has been improved by the use of the grazing incidence geometry, diode-pumped solid-state lasers, and seeding techniques. The dominant X-ray laser schemes are the monopole collisional excitation lasers either driven by chirped pulse amplification (CPA) laser systems or capillary discharge. The CPA systems drive lasing in neon-like or nickel-like ions, typically in the 10 – 30 nm range, while the capillary system works best for neon-like argon at 46.9 nm. Most researchers use nickel-like ion lasers near 14 nm because they are well matched to the Mo:Si multilayer mirrors that have peak reflectivity near 13 nm and are used in many applications. As a result, the last decade has seen the birth of the X-ray free electron laser (XFEL) that can reach wavelengths down to 0.15 nm and the inner-shell Ne laser at 1.46 nm.

  6. Dissolution de phases minérales MSiO3 ( M Cu, Co, Ni, Zn, Mg) imparfaitement cristallisées au contact de solutions d'agents complexants organiques (porphyrines, amino-acides, asphaltènes)

    NASA Astrophysics Data System (ADS)

    Bergaya, F.; Perruchot, A.; Van Damme, H.

    1983-05-01

    The kinetic and thermodynamic aspects of the dissolution of ill-organized ("gels") high surface area silicates of general formula MO- SiO2- nH2O( M = Cu, Co, Ni, Zn, Mg) in the presence of the following organic compounds have been investigated: meso-tetraphenylporphyrin (H 2TPP, water insoluble), mesotetra(N-methylpyridyl)porphyrin (H 3TMPyP, water soluble), glycine, and asphaltenes. Kinetic aspects were emphasised in the case of H 2TMPyP. The initial rate of the gross dissolution complexation process followed almost quantitatively (passing from one metal to another) the complexation rate of M2+ ions by H 2TMPyP in a purely homogeneous medium, suggesting that the rate limiting step of the overall process is not related to the chemical or physical processes occurring in the solid particles or at the solid-solution interface, but is simply the complexation, in the solution, of the M2+ ions released by the gel particles. Thermodynamic aspects were emphasised in the case of glycine. The total amount of metal which is extracted at equilibrium can be reasonably well predicted from a simple model which takes into account (i) the stability constant of the metal-glycine complex. (ii) the "solubility product" of the gel particles in water. The results obtained with asphaltones are closer to those obtained with glycine than to those obtained with porphyrins, suggesting that porphyrins represent only a minor population in the complexing functional groups of asphaltenes.

  7. Electron traps in amorphous In-Ga-Zn-O thin films studied by isothermal capacitance transient spectroscopy

    NASA Astrophysics Data System (ADS)

    Hayashi, Kazushi; Hino, Aya; Morita, Shinya; Yasuno, Satoshi; Okada, Hiroshi; Kugimiya, Toshihiro

    2012-03-01

    Electron traps in amorphous In-Ga-Zn-O (a-IGZO) thin films were studied using isothermal capacitance transient spectroscopy (ICTS). Broad peaks that shifted toward a longer elapsed time with an increase in the filling pulse width were detected from the ICTS spectra for metal-oxide-semiconductor diodes consisting of a Mo/SiO2/a-IGZO structure. The time constant of the peak position at 180 K was found to be from ˜1 m to ˜100 ms, corresponding to a range of energy level from ˜170 to ˜230 meV below the conduction band edge. The total trap density around the peak was estimated to be ˜1 × 1016 cm-3.eV-1. Further, according to the biasing voltage dependence of the ICTS signal, the density of the trap states increases by about three orders of magnitude near the interface between the a-IGZO and the gate dielectric layers. The electron transport in electronic devices using an a-IGZO could be influenced by the trap states detected in the present study.

  8. A Preliminary Investigation of the Cr3Si-Mo Pseudo-Binary Phase Diagram

    NASA Technical Reports Server (NTRS)

    Dickerson, R. M.; Raj, S. V.; Locci, I. E.

    1995-01-01

    An investigation was undertaken to study the phase relations in Cr3Si alloyed with Mo varying from 10 to 83.5 wt. % of the material. Specimens were prepared from arc-melted buttons that were subsequently heat treated at 1673 K for 200 h and air quenched to room temperature to structures. Alloys containing more than 20 wt. % MO were primarily two-phase materials of M3Si and M5Si3, where M is (Cr,Mo). Three alloys contained less than 5% of a third phase, which also had the M5Si3 crystal structure. Differential thermal analysis (DTA) was performed on several specimens at temperatures up to 2073 K in order to determine a solidus curve for the M3Si phase. Since only one DTA peak was observed in each alloy, the M5Si3 phase must melt above 2073 K, the maximum temperature examined. A preliminary pseudo-binary phase diagram for (Cr,Mo)3Si and a portion of the 1673 K isothermal section of the Cr-Mo-Si ternary phase diagram are presented.

  9. In situ observation of thermal expansion of tetragonal C11b phase in Zr2Cu(1-x)Odx alloys

    SciTech Connect

    Xu, Min; Ye, Y. Y.; Morris, James R; Sordelet, D. J.; Kramer, M. J.

    2010-01-01

    The C11b phase crystalline structure (structure type MoSi{sub 2}, space group I4/mmm) in the Zr{sub 2}Cu{sub (1-x)}Pd{sub x} (x = 0, 0.25, 0.5, 0.75 and 1) alloys was examined in situ using high temperature X-ray diffraction (HTXRD) and Rietveld refinement of the data obtained at a constant heating rate. While the cell volume increases with increasing Pd as expected by the larger atomic radii, the coefficients of thermal expansion (CTEs) do not follow a uniform trend. The bonding in the basal plane is more elastically rigid than along the c-axis for all compositions. The CTE is more anisotropic for Zr{sub 2}Pd than for Zr{sub 2}Cu, which is consistent with the first-principles calculations that illustrate the rigidity of c-axis relatively to a-axis to be the less for Zr{sub 2}Pd. The CTE of the a-axis for Zr{sub 2}Pd is in fact negative over the temperature range measured.

  10. Analysis of a New High-Toughness Ultra-high-Strength Martensitic Steel by Transmission Electron Microscopy and Atom Probe Tomography

    NASA Astrophysics Data System (ADS)

    Hartshorne, Matthew I.; McCormick, Caroline; Schmidt, Michael; Novotny, Paul; Isheim, Dieter; Seidman, David N.; Taheri, Mitra L.

    2016-04-01

    The microstructure of a new martensitic high-strength steel (Fe-0.40C-3.81Ni-1.31Cr-1.50Si-0.75Mn-0.52Mo-0.51Cu-0.30V) with high fracture toughness is characterized by transmission electron microscopy and atom probe tomography (APT). MC, M6C, and M23C6 precipitates form inside the martensitic lath matrix. The fracture toughness is insensitive to the dissolution of M23C6 precipitates at austenitizing temperatures above 1164 K (891 °C). APT reveals that solute segregation at the prior austenite grain boundaries (PAGB) is not uniform, with C, Mo, Si, Ni, and/or P enrichment varying at different areas of the PAGB. Si depletion is detected in the same area as the highest C enrichment. Carbon also segregates at lath boundaries. Segregation of C indicates the presence of retained austenite films at both PAGB and lath boundaries. Regions enriched in C up to 10 pct were found within the laths; however, no regions were enriched to the level expected of cementite or ɛ-carbide. The observed C distribution and high fracture toughness indicates that the tempering behavior is significantly different than that observed in 300M steel. The effect of Si, Ni, and Cu on the formation and stabilization of the regions of C enrichment and retained austenite require further study, as it may be key to the increased toughness.

  11. Effect of ion beam etching on the surface roughness of bare and silicon covered beryllium

    NASA Astrophysics Data System (ADS)

    Chkhalo, N. I.; Mikhaylenko, M. S.; Mil'kov, A. V.; Pestov, A. E.; Polkovnikov, V. N.; Salashchenko, N. N.; Strulya, I. L.; Zorina, M. V.; Zuev, S. Yu.

    2017-05-01

    In the paper is studied the main aspects of using ion-beam etching for finish polishing. It is found that 400 eV is the optimal energy for neon ion etching ensuring slight surface roughness smoothing in the range of incidence angles of +/- 40°. The deposition of 200 nm amorphous silicon films onto beryllium and their subsequent etching with the 800 eV argon ions improve the effective surface roughness integrated across the range of the spatial frequencies of 0.025-60 μm-1, from σeff=1.37 nm down to σeff=0.29 nm. The effectiveness of the smoothing technology for x-ray applications, confirmed by the results of the study the reflective properties of the Mo/Si mirrors deposited on the substrate. The reflectivity at a wavelength of 13.5 nm increased from 2% for the substrates with the surface roughness of σeff=2.3 nm (the roughness value corresponds to the as-prepared bulk Be substrates and is taken from the literature) up to 67.5% after the smoothing technology.

  12. Superconducting nanowire single photon detectors based on amorphous superconductors (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Korzh, Boris; Caloz, Misael; Renema, Jelmer; Warburton, Richard J.; Schönenberger, Christian; Zbinden, Hugo; Bussières, Félix

    2017-05-01

    Superconducting nanowire single photon detectors (SNSPD) made from amorphous superconductors have showed great promise for achieving high fabrication yields, due to the highly uniform nature of the films. We present progress on the development of SNSPD based on amorphous MoSi with a critical temperature of around 5 K, which is ideal for detector operation at temperatures of 1 - 2.5 K, accessible with widely available cryogenic systems. First generation devices have achieved a saturated internal efficiency from visible to near-infrared wavelengths, which is the first requirement for high overall system efficiency. The broadband response has allowed us to make a robust study the energy-current relation in these devices, which defines the current required for a saturated internal detection efficiency for a given incident photon energy. Contrary to previous studies with other material systems, we find a nonlinear energy-current relation, which is an important insight into the detection mechanism in SNSPDs. The latest generation devices have been embedded into an micro-cavity structure in order to increase the system detection efficiency, which has increased to over 65% at 1550 nm. The efficiency is believed to be limited by fabrication imperfections and we present ongoing progress towards improving this characteristic as well as the yield of the devices. Efforts are also being made towards increasing the maximum operating temperature of the devices.

  13. [Analysis of inorganic elements of several species from Moghania genus and M. philippinensis from different habitats].

    PubMed

    Ding, Ling; Zuo, Xu; Ren, Chao-Qin; Liu, Yuan

    2013-01-01

    To compare the contents of inorganic elements in root, stem and leaf of several species from Moghania genus and root of M. philippinensis from different habitats. Inductively Coupled Plasma Optical Emission Spectrum (ICP-OES) was used to determine twenty five inorganic elements simultaneously. The correlation analysis, principal component analysis and cluster analysis were applied for the study of inorganic elements. The content of inorganic elements from different species was difference. As for M. philippinensis from different habitats, the content sequence was Guangxi > Jiangxi > Guangdong > Sichuan. There was significant correlation between different inorganic elements. The principal component analysis results showed that V, Co, K, Fe, Cr, P, Mo, Si, Na, Ca and Mg might be the characteristic elements of these species from Moghania genus. The results of cluster analysis showed that M. philippinensis and M. strobilifera could be separated and M. philippinensis from Guangxi, Jiangxi, Guangdong and Sichuan could be separated. This experiment provided theoretical basis for distinguish and quality assessment of species from Moghania genus and M. philippinensis from different habitats.

  14. Novel Accident-Tolerant Fuel Meat and Cladding

    SciTech Connect

    Robert D. Mariani; Pavel G Medvedev; Douglas L Porter; Steven L Hayes; James I. Cole; Xian-Ming Bai

    2013-09-01

    A novel accident-tolerant fuel meat and cladding are here proposed. The fuel meat design incorporates annular fuel with inserts and discs that are fabricated from a material having high thermal conductivity, for example niobium. The inserts are rods or tubes. Discs separate the fuel pellets. Using the BISON fuel performance code it was found that the peak fuel temperature can be lowered by more than 600 degrees C for one set of conditions with niobium metal as the thermal conductor. In addition to improved safety margin, several advantages are expected from the lower temperature such as decreased fission gas release and fuel cracking. Advantages and disadvantages are discussed. An enrichment of only 7.5% fully compensates the lost reactivity of the displaced UO2. Slightly higher enrichments, such as 9%, allow uprates and increased burnups to offset the initial costs for retooling. The design has applications for fast reactors and transuranic burning, which may accelerate its development. A zirconium silicide coating is also described for accident tolerant applications. A self-limiting degradation behavior for this coating is expected to produce a glassy, self-healing layer that becomes more protective at elevated temperature, with some similarities to MoSi2 and other silicides. Both the fuel and coating may benefit from the existing technology infrastructure and the associated wide expertise for a more rapid development in comparison to other, more novel fuels and cladding.

  15. Fatigue crack growth of titanium rotor alloys in vacuum and air

    SciTech Connect

    McClung, R.C.; Lawless, B.H.; Gorelik, M.; Date, C.; Gill, Y.; Piascik, R.S.

    1999-07-01

    An enhanced life management system for aircraft turbine engine rotors based on probabilistic damage tolerance methods is currently under development by the engine industry and the FAA, with an initial focus on fatigue cracking at hard alpha (HA) defects in titanium. Since HA defects are usually subsurface, any resulting cracks are embedded and hence isolated from the atmosphere (i.e., vacuum-like) for at least some of their life. Fatigue crack growth (GCG) tests have been conducted in vacuum at various temperatures and stress ratios for Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo+Si rotor alloys. A brief study of vacuum levels suggests that pressures of 10{sup {minus}6} Torr are adequate to capture full vacuum effects on FCG rates. Vacuum FCG results are compared with available air data. The vacuum data demonstrate temperature and stress ratio effects comparable to air data. The vacuum and air data exhibit the same growth rates in the upper Paris regime, but apparent thresholds are significantly higher in vacuum than in air.

  16. New Fiber Reinforced Waterless Concrete for Extraterrestrial Structural Applications

    NASA Technical Reports Server (NTRS)

    Toutanji, H.; Tucker, D.; Ethridge, E.

    2005-01-01

    Commercial use of sulfur concrete on Earth is well established, particularly in corrosive, e.g., acid and salt, environments. Having found troilite (FeS) on the Moon raises the question of using extracted sulfur as a lunar construction mate: iii an attractive alternative to conventional concrete as it does not require water For the purpose of this paper it is assumed that lunar ore is mined, refined, and the raw sulfur processed with appropriate lunar regolith to form, for example, brick and beam elements. Glass fibers produced from regolith were used as a reinforcement to improve the mechanical properties of the sulfur concrete. Glass fibers and glass rebar were produced by melting the lunar regolith simulant. Lunar regolith stimulant was melted in a 25 cc Pt-Rh crucible in a Sybron Thermoline 46100 high temperature MoSi2 furnace at melting temperatures of 1450 to 1600G. The glass melt wets the ceramic rod and long continuous glass fibers were easily hand drawn. The glass fibers were immediately coated with a protective polymer to maintain the mechanical strength. The viability of sulfur concrete as a construction material for extraterrestrial application is presented. The mechanical properties of the glass fiber reinforced sulfur concrete were investigated.

  17. Performance of "Waterless Concrete"

    NASA Technical Reports Server (NTRS)

    Toutanji, H. A.; Grugel, R. N.

    2009-01-01

    Waterless concrete consists of molten elementary sulfur and aggregate. The aggregates in a lunar environment will be lunar rocks and soil. Sulfur is present on the Moon in Troilite soil (FeS) and, by oxidation of the soil, iron and sulfur can be produced. Sulfur concrete specimens were cycled between liquid nitrogen (approx.]91 C) and room temperature (^21 C) to simulate exposure to a lunar environment. Cycled and control specimens were subsequently tested in compression at room temperatures (^21 C) and ^-101 C. Test results showed that due to temperature cycling, the compressive strength of cycled specimens was 20% of those non-cycled. This reduction in strength can be attributed to the large differences in thermal coefficients of expansion of the materials constituting the concrete which promoted cracking. Similar sulfur concrete mixtures were strengthened with short and long glass fibres. The lunar regolith simulant was melted in a 25 cc Pt- Rh crucible in a Sybron Thermoline high temperature MoSi2 furnace at melting temperatures of 1450 to 1600 C for times of 30 min to i hour. Glass fibres and small rods were pulled from the melt. The glass fibres were used to reinforce sulfur concrete plated to improve the flexural strength of the sulfur concrete. Beams strengthened with glass fibres showed to exhibit an increase in the flexural strength by as much as 45%.

  18. Sintering Behavior and Microstructure Formation of Titanium Aluminide Alloys Processed by Metal Injection Molding

    NASA Astrophysics Data System (ADS)

    Soyama, Juliano; Oehring, Michael; Ebel, Thomas; Kainer, Karl Ulrich; Pyczak, Florian

    2017-04-01

    The sintering behavior of metal injection molded titanium aluminide alloys, their microstructure formation and resulting mechanical properties were investigated. As reference material, the alloy Ti-45Al-5Nb-0.2B-0.2C at.% (TNB-V5) was selected. Additionally, two other variations with Mo and Mo + Si additions were prepared: Ti-45Al-3Nb-1Mo-0.2B-0.2C at.% and Ti-45Al-3Nb-1Mo-1Si-0.2B-0.2C at.%. The results indicate that the optimum sintering temperature was slightly above the solidus line. With proper sintering parameters, very low porosities (<0.5%) and fine microstructures with a colony size <85 µm could be achieved. Considering the sintering temperatures applied, the phase transformations upon cooling could be described as L + β → β → α + β → α → α + γ → α2 + γ, which was in agreement with the microstructures observed. The effects of Mo and Si were opposite regarding the sintering behavior. Mo addition led to an increase in the optimum sintering temperature, whereas Si caused a significant decrease.

  19. Effects of gravity on combustion synthesis of functionally graded biomaterials

    NASA Astrophysics Data System (ADS)

    Moore, J.; Schowengerdt, F.; Ayers, R.; Castillo, M.; Zhang, X.; Umakoshi, U.; Yi, C.; Guigne, J.

    Combustion synthesis, or self-propagating, high temperature synthesis (SHS) is currently being used at the Colorado School of Mines to produce advanced materials for biomedical applications. These biomaterials include ceramic, intermetallic, and metal-matrix composites for applications ranging from structural to oxidation- and wear-resistant materials, e.g., TiC-Ti, TiC-Cr3 C2 , MoSi2 - SiC, NiAl-TiB2 , to engineered porous composites, e.g., B4 C-A l2 O3 , Ti-TiBx , Ni-Ti, Ca 3 (PO4 )2 and glass- ceramic composites, e.g., CaO-SiO2 - B a O-A l2 O3 -T i B2 . The goal of the functionally graded biomaterials project is to develop new materials, graded in porosity and composition, which will combine the desirable mechanical properties of implant, e.g., NiTi, with the bone-growth enhancement properties of porous biodegradable ceramics, e.g., Ca 3 (PO4 )2 . Recent experiments on the NASA parabolic flight (KC- 135) aircraft have shown that gravity plays an important role in controlling the structure and properties of materials produced by combustion synthesis. The results of these studies, which will be presented at the conference, will provide valuable input to the design of experiments to be done in Space-DRUMSTM, a containerless materials processing facility scheduled to be placed on the International Space Station in 2003.

  20. Adsorption and electron-induced polymerization of methyl methacrylate on Ru(1010)

    SciTech Connect

    Hedhili, M. N.; Yakshinskiy, B. V.; Wasielewski, R.; Ciszewski, A.; Madey, T. E.

    2008-05-07

    The adsorption and electron irradiation of methyl methacrylate (MMA) on a Ru(1010) surface have been studied using x-ray photoelectron spectroscopy (XPS), temperature programmed desorption (TPD), and low energy ion scattering. TPD analysis indicates that a monolayer of MMA chemisorbs and dissociates on the Ru(1010) surface. The reaction products observed upon heating include H{sub 2}, CO, CO{sub 2}, and a small amount of MMA. Physisorbed multilayers of MMA desorb at temperatures around 170 K. Electron irradiation of physisorbed MMA at 140 K leads to a modification of the MMA film: The XPS spectra show an increase in thermal stability of the film with retention of the MMA structure, and indicate that electron irradiation induces polymerization. An increase in the electron bombardment fluence induces a degradation of the formed polymerized species and leads to the accumulation of carbon on the Ru surface. These results are relevant to the accumulation of carbon on surfaces of Ru films that serve as capping layers on Mo/Si multilayer mirrors used in extreme ultraviolet lithography.

  1. Direct photo-etching of poly(methyl methacrylate) using focused extreme ultraviolet radiation from a table-top laser-induced plasma source

    SciTech Connect

    Barkusky, Frank; Peth, Christian; Bayer, Armin; Mann, Klaus

    2007-06-15

    In order to perform material interaction studies with intense extreme ultraviolet (EUV) radiation, a Schwarzschild mirror objective coated with Mo/Si multilayers was adapted to a compact laser-based EUV plasma source (pulse energy 3 mJ at {lambda}=13.5 nm, plasma diameter {approx}300 {mu}m). By 10x demagnified imaging of the plasma a pulse energy density of {approx}75 mJ/cm{sup 2} at a pulse length of 6 ns can be achieved in the image plane of the objective. As demonstrated for poly(methyl methacrylate) (PMMA), photoetching of polymer surfaces is possible at this EUV fluence level. This paper presents first results, including a systematic determination of PMMA etching rates under EUV irradiation. Furthermore, the contribution of out-of-band radiation to the surface etching of PMMA was investigated by conducting a diffraction experiment for spectral discrimination from higher wavelength radiation. Imaging of a pinhole positioned behind the plasma accomplished the generation of an EUV spot of 1 {mu}m diameter, which was employed for direct writing of surface structures in PMMA.

  2. Mechanisms of fatigue damage and crack growth in advanced materials

    NASA Astrophysics Data System (ADS)

    Ritchie, Robert O.

    2001-03-01

    In terms of in-service failures, cyclic fatigue is the most prevalent form of fracture. Despite the wealth of information on fatigue failures in traditional structural materials such as (ductile) metals and alloys, far less is understood about the susceptibility of the newer advanced materials, such as (brittle) intermetallics, ceramics and their composites. In this presentation, the mechanics and mechanisms of fatigue damage and crack propagation are examined with particular emphasis on the similarities and differences between cyclic crack growth in ductile metallic materials, and corresponding behavior in the more brittle advanced materials. This is achieved by considering the process of subcritical crack growth as a mutual competition between intrinsic mechanisms of microstructural damage ahead of the crack tip, which promote crack growth, and extrinsic mechanisms of crack-tip shielding behind the tip, which impede it. This approach is shown to be important for the understanding of the structural fatigue properties of advanced materials, such as monolithic and composite ceramics, and a range of intermetallics (e.g., TiAl, MoSi2, Nb3Al), as the mechanisms of fatigue in these brittle materials are conceptually distinct from that associated with the well known metal fatigue. Examples of the application and life-prediction methodologies for such materials in fatigue-critical situations will be given from the aerospace and bioengineering industries.

  3. The art of photomask materials for low-k1-193nm lithography

    NASA Astrophysics Data System (ADS)

    Hashimoto, Masahiro; Iwashita, Hiroyuki; Mitsui, Hideaki

    2009-04-01

    The resolution of photomask patterns were improved with a hardmask (HM) system. The system which is thin Sicompounds layer is easily etched by the hyper-thin resist (below 100nm thickness). The HM material has sufficient etching selectivity against the chrome-compounds which is the second layer chrome absorber for the phase-shifter. This hardmask layer has been completely removed during the phase-shifter etching. It means that the conventional phase-shit mask (PSM) has been made with the ultimately high-resolution without configuration changes. Below 50nm resolution of PSM was made with 90nm thickness resist on HM layer in this paper. The CD bias between a resist feature CD and a chrome feature CD was almost zero (below 1nm) in the optimized etching condition. We confirmed that the mask performances were the equal to COMS (Cr-HM on MoSi binary mask) in resolution and CD linearity. The performances of hardmask blanks will be defined by resist performance because of almost zero bias.

  4. High-temperature corrosion of UNS N10003 in molten Li2BeF4 (FLiBe) salt

    DOE PAGES

    Zheng, Guiqiu; Kelleher, Brian; He, Lingfeng; ...

    2015-07-30

    Here, corrosion testing of Hastelloy N in molten fluoride salt was performed in purified molten 27LiF-BeF2 (66-34mol%) (FLiBe) salt at 700°C for 1000 hours, in pure nickel and graphite capsules. In the nickel capsule tests, the near-surface region of the alloy exhibited an about 200 nm porous structure, an approximately 3.5 μm chromium depleted region, and MoSi2 precipitates. In tests performed in graphite capsules, the alloy samples gained weight due to the formation of a variety of Cr3C2, Cr7C3, Mo2C and Cr23C6, carbide phases on the surface and in the subsurface regions of the alloy. A Cr depleted region wasmore » observed in the near-surface region where Mo thermally diffused toward either surface or grain boundary, which induced approximately 1.4 μm Ni3Fe alloy layer in this region. The carbide containing layer extended to about 7 μm underneath the Ni3Fe layer. The presence of graphite dramatically changes the mechanisms of corrosion attack in Hastelloy N in molten FLiBe salt. Evaluated by in terms of the depth of attack, graphite clearly accelerates corrosion, but the results appear to indicate that the formation of Cr23C6 phase might stabilize the Cr and mitigate its dissolution in molten FLiBe salt.« less

  5. Microstructural evolution and mechanical behavior of nickel-based superalloy 625 made by selective laser melting

    NASA Astrophysics Data System (ADS)

    Witkin, David B.; Adams, Paul; Albright, Thomas

    2015-03-01

    The mechanical properties and microstructures of Selective Laser Melted (SLM) alloy 625 procured from different suppliers were compared. The post-SLM process of hot isostatic pressing (HIP) led to a relatively coarse recrystallized gamma matrix phase that was similar in all the suppliers' materials, resulting in nearly identical tensile properties. These similarities obscure significant differences between them with respect to the population of second phase particles, which consisted of carbides or Laves phase. During solidification, the final liquid phase is concentrated in Nb, Mo, Si and C, and leads to L --> γ + carbide/Laves eutectic reactions. Secondary particles are very small prior to HIP and their composition has not been analyzed yet, but are limited to the fine-grained eutectic regions of the material prior to HIP. During HIP the gamma phase recrystallizes to remove the original as-solidified SLM microstructure, but secondary particles nucleate and grow where their elemental constituents first solidified, leading to a non-homogeneous distribution. Quasi-static tensile properties do not appear to be sensitive to these differences, but it is likely that other mechanical properties will be affected, especially fatigue and fracture behavior. Surface roughness, large grain size, and pores and voids left unhealed by the HIP cycle will also influence fatigue and fracture. Surface roughness and porosity in particular are features that could be improved by implementing novel approaches to laser processing in SLM.

  6. Fracture and fatigue properties of Mo-Mo{sub 3}Si-Mo{sub 5}SiB{sub 2} refractory intermetallic alloys at ambient to elevated temperatures (25-1300 degrees Centigrade)

    SciTech Connect

    Choe, Heeman; Schneibel, J.H.; Ritchie, R.O.

    2002-08-01

    The need for structural materials with high-temperature strength and oxidation resistance coupled with adequate lower-temperature toughness for potential use at temperatures above {approx} 1000 degrees C has remained a persistent challenge in materials science. In this work, one promising class of intermetallic alloys is examined, namely boron-containing molybdenum silicides, with compositions in the range Mo (bal), 12-17 at. percentSi, 8.5 at. percentB, processed using both ingot (I/M) and powder (P/M) metallurgy methods. Specifically, the oxidation (''pesting''), fracture toughness and fatigue-crack propagation resistance of four such alloys, which consisted of {approx}21 to 38 vol. percent a-Mo phase in an intermetallic matrix of Mo3Si and Mo5SiB2 (T2), were characterized at temperatures between 25 degrees and 1300 degrees C. The boron additions were found to confer superior ''pest'' resistance (at 400 degrees to 900 degrees C) as compared to unmodified molybdenum silicides, such as Mo5Si3. Moreover , although the fracture and fatigue properties of the finer-scale P/M alloys were only marginally better than those of MoSi2, for the I/M processed microstructures with coarse distributions of the a-Mo phase, fracture toughness properties were far superior, rising from values above 7 MPa sqrt m at ambient temperatures to almost 12 MPa sqrt m at 1300 degrees C.

  7. Structure and properties of composites synthesized in situ using solid state displacement reactions

    SciTech Connect

    Henager, C.H. Jr.; Brimhall, J.L.

    1993-10-01

    Solid state displacement reactions can produce in situ intermetallic and ceramic matrix composites in a process where an intermetallic or ceramic phase(s) and a potential reinforcing phase(s) are grown together during a solid state reaction. Interpenetrating and dispersed microstructures, important for desirable composite properties, have been produced by means of displacement reaction processing techniques. Two such composites have been synthesized which exhibit two distinct microstructures: MoSi{sub 2} reinforced with SiC particles, which exhibits a dispersed-phase structure, and NiAl/Ni{sub 3}Al reinforced with Al{sub 2}O{sub 3}, which exhibits an interpenetrating-phase structure. Strength in bending and chevron-notch fracture toughness have been determined as a function of temperature, and measured properties compare favorably with composites produced by other means. The measured properties are discussed with regard to the observed microstructures. The potential for displacement reaction processing is assessed, and it appears to be a cost-effective synthesis method compared to others.

  8. Performance improvement of optical fiber coupler with electric heating versus gas heating.

    PubMed

    Shuai, Cijun; Gao, Chengde; Nie, Yi; Peng, Shuping

    2010-08-20

    Gas heating has been widely used in the process of fused biconical tapering. However, as the instability and asymmetric flame temperature of gas heating exist, the performance of the optical devices fabricated by this method was affected. To overcome the problems resulting from gas combustion, an electric heater is designed and manufactured using a metal-ceramic (MoSi(2)) as a heating material. Our experimental data show that the fused-taper machine with an electric heater has improved the performance of optical devices by increasing the consistency of the extinction ratio, excess loss, and the splitting ratio over that of the previous gas heating mode. Microcrystallizations and microcracks were observed at the fused region of the polarization-maintaining (PM) fiber coupler and at the taper region with scanning electron microscopy and atomic force microscopy respectively. The distribution of the microcrystallizations and microcracks are nonuniform along the fiber with gas heating, while their distribution is rather uniform with electric heating. These findings show that the novel optical fiber coupler with an electric heater has improved the performance of optical fiber devices by affecting the consistency of the optical parameters and micromorphology of the surface of PM fiber.

  9. Micromechanisms of creep-fatigue crack growth in a silicide-matrix composite with SiC particles

    SciTech Connect

    Ramamurty, U.; Kim, A.S.; Suresh, S. ); Petrovic, J.J. )

    1993-08-01

    An experimental study has been conducted to examine the cyclic fatigue crack growth characteristics in 1,200 C air of a MoSi[sub 2]-50 mol% WSi[sub 2] alloy in the unreinforced condition and with 30 vol% SiC particles. For comparison purposes, crack growth experiments under sustained loads were also carried out in the silicide-matrix composite. Particular attention is devoted to developing an understanding of the micromechanism of subcritical crack growth by recourse to optical and electron microscopy, including transmission electron microscopy of crack-tip damage. The results indicate that enhanced viscous flow of glass films along interfaces and grain boundaries imparts pronounced levels of subcritical crack growth in the composite material; the composite exhibits a higher fatigue fracture threshold and a more extended range of stable fracture than the unreinforced alloy. The effects of glass phase in influencing fatigue crack growth in the silicide-based material are compared to the influence of in situ-formed and preexisting glass films on high-temperature cyclic fatigue crack growth in ceramics and ceramic composites. The paper concludes with a comparison of present results with the high-temperature damage tolerance of a variety of intermetallic alloys and ceramic materials.

  10. High current metal ion implantation to synthesize some conducting metal-silicides

    SciTech Connect

    Liu, B. X.; Gao, K. Y.

    1999-06-10

    High current metal-ion implantation by a metal vapor vacuum arc ion source was conducted to synthesize some conducting metal-silicides. It was found that C54-TiSi{sub 2}, ZrSi{sub 2}, NiSi{sub 2}, CoSi{sub 2}, {beta}-FeSi{sub 2}, NbSi{sub 2} and TaSi{sub 2} layers on Si wafers with good electric properties could be obtained directly after implantation. In comparison, the formation of some other silicides like {alpha}-FeSi{sub 2}, NbSi{sub 2}, TaSi{sub 2}, tetragonal-WSi{sub 2} and tetragonal-MoSi{sub 2} required an additional post-annealing to improve their crystallinity and thus their electric properties. Interestingly, the NiSi{sub 2} layers of superior electric properties were obtained at a selected Ni-ion current density of 35 {mu}A/cm{sup 2}. At this current, a beam heating raised the Si wafer to a specific temperature of 380 deg. C, at which the size difference between NiSi{sub 2} and Si lattices was nil. The resistivity of the NiSi{sub 2} layers so obtained was much lower than that of the Ni-disilicide formed by solid-state reaction at >750 deg. C. The formation mechanism of the above metal-silicides and the associated electric properties will also be discussed.

  11. Electronic structure of the Nowotny chimney-ladder silicide Ru{sub 2}Si{sub 3}

    SciTech Connect

    Wolf, W.; Bihlmayer, G.; Bluegel, S.

    1997-03-01

    We report {ital ab initio} calculations for the electronic structure of the Nowotny chimney-ladder silicide Ru{sub 2}Si{sub 3} in the orthorhombic low-temperature phase. We find Ru{sub 2}Si{sub 3} to be a semiconductor with a direct band gap of about 0.45 eV. Since this gap is a p-d gap, the oscillator strength for a direct transition is expected to be of sizable magnitude. Also, the calculated effective masses of hole and electron states suggest that Ru{sub 2}Si{sub 3} is a very promising material for various applications in semiconductor technology. The electronic structure is controlled by the hybridization of Si p states with Ru d states and shows similarities to the group-IV transition-metal disilicides (CrSi{sub 2}, MoSi{sub 2}, WSi{sub 2}) and to transition-metal-rich silicides. The calculations are based on the density-functional theory in local-density approximation and are performed by means of the full-potential linearized-augmented-plane-wave method. {copyright} {ital 1997} {ital The American Physical Society}

  12. X-ray-ultraviolet beam splitters for the Michelson interferometer.

    PubMed

    Delmotte, Franck; Ravet, Marie-Françoise; Bridou, Françoise; Varnière, Françoise; Zeitoun, Philippe; Hubert, Sébastien; Vanbostal, Laurent; Soullie, Gérard

    2002-10-01

    With the aim of realizing a Michelson interferometer working at 13.9 nm, we have developed a symmetrical beam splitter with multilayers deposited on the front and back sides of a silicon nitride membrane. On the basis of the experimental optical properties of the membrane, simulations have been performed to define the multilayer structure that provides the highest reflectivity-transmission product. Optimized Mo-Si multilayers have been successfully deposited on both sides of t he membrane by use of the ion-beam sputtering technique, with a thickness-period reproducibility of 0.1 nm. Measurements by means of synchrotron radiation at 13.9 nm and at an angle of 45 degrees provide a reflectivity of 14.2% and a transmission of 15.2% for a 60% s-polarized light, close to the simulated values. Such a beam splitter has been used for x-ray laser Michelson interferometry at 13.9 nm. The first interferogram is discussed.

  13. Mask degradation monitoring with aerial mask inspector

    NASA Astrophysics Data System (ADS)

    Tseng, Wen-Jui; Fu, Yung-Ying; Lu, Shih-Ping; Jiang, Ming-Sian; Lin, Jeffrey; Wu, Clare; Lifschitz, Sivan; Tam, Aviram

    2013-06-01

    As design rule continues to shrink, microlithography is becoming more challenging and the photomasks need to comply with high scanner laser energy, low CDU, and ever more aggressive RETs. This give rise to numerous challenges in the semiconductor wafer fabrication plants. Some of these challenges being contamination (mainly haze and particles), mask pattern degradation (MoSi oxidation, chrome migration, etc.) and pellicle degradation. Fabs are constantly working to establish an efficient methodology to manage these challenges mainly using mask inspection, wafer inspection, SEM review and CD SEMs. Aerial technology offers a unique opportunity to address the above mask related challenges using one tool. The Applied Materials Aera3TM system has the inherent ability to inspect for defects (haze, particles, etc.), and track mask degradation (e.g. CDU). This paper focuses on haze monitoring, which is still a significant challenge in semiconductor manufacturing, and mask degradation effects that are starting to emerge as the next challenge for high volume semiconductor manufacturers. The paper describes Aerial inspector (Aera3) early haze methodology and mask degradation tracking related to high volume manufacturing. These will be demonstrated on memory products. At the end of the paper we take a brief look on subsequent work currently conducted on the more general issue of photo mask degradation monitoring by means of an Aerial inspector.

  14. Thermodynamic modeling and kinetics simulation of precipitate phases in AISI 316 stainless steels

    NASA Astrophysics Data System (ADS)

    Yang, Y.; Busby, J. T.

    2014-05-01

    This work aims at utilizing modern computational microstructural modeling tools to accelerate the understanding of phase stability in austenitic steels under extended thermal aging. Using the CALPHAD approach, a thermodynamic database OCTANT (ORNL Computational Thermodynamics for Applied Nuclear Technology), including elements of Fe, C, Cr, Ni, Mn, Mo, Si, and Ti, has been developed with a focus on reliable thermodynamic modeling of precipitate phases in AISI 316 austenitic stainless steels. The thermodynamic database was validated by comparing the calculated results with experimental data from commercial 316 austenitic steels. The developed computational thermodynamics was then coupled with precipitation kinetics simulation to understand the temporal evolution of precipitates in austenitic steels under long-term thermal aging (up to 600,000 h) at a temperature regime from 300 to 900 °C. This study discusses the effect of dislocation density and difusion coefficients on the precipitation kinetics at low temperatures, which shed a light on investigating the phase stability and transformation in austenitic steels used in light water reactors.

  15. Development of a high-speed vacuum ultraviolet (VUV) imaging system for the Experimental Advanced Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Zhou, Fan; Ming, Tingfeng; Wang, Yumin; Wang, Zhijun; Long, Feifei; Zhuang, Qing; Li, Guoqiang; Liang, Yunfeng; Gao, Xiang

    2017-07-01

    A high-speed vacuum ultraviolet (VUV) imaging system for edge plasma studies is being developed on the Experimental Advanced Superconducting Tokamak (EAST). Its key optics is composed of an inverse type of Schwarzschild telescope made of a set of Mo/Si multilayer mirrors, a micro-channel plate (MCP) equipped with a P47 phosphor screen and a high-speed camera with CMOS sensors. In order to remove the contribution from low-energy photons, a Zr filter is installed in front of the MCP detector. With this optics, VUV photons with a wavelength of 13.5 nm, which mainly come from the line emission from intrinsic carbon (C vi: n = 4-2 transition) or the Ly-α line emission from injected Li iii on the EAST, can be selectively measured two-dimensionally with both high temporal and spatial resolutions. At present, this system is installed to view the plasma from the low field side in a horizontal port in the EAST. It has been operated routinely during the 2016 EAST experiment campaign, and the first result is shown in this work. To roughly evaluate the system performance, synthetic images are created. And it indicates that this system mainly measures the edge localized emissions by comparing the synthetic images and experimental data.

  16. Influence of particle bombardment on microstructure and internal stresses of refractory metal suicides on silicon

    NASA Astrophysics Data System (ADS)

    Hardtke, Ch.; Schilling, W.; Ullmaier, H.

    1991-07-01

    First results on microstructural changes and stress relaxation in thin refractory metal suicide films (TaSi 2 and MoSi 2) caused by particle bombardment are reported. The polycrystalline films had initial tensile stresses of some 10 9 Pa. Exposed to irradiation with Ge ions of 400 keV, both suicides showed a similar stress relaxation behaviour as a function of dose. During room-temperature implantation the initial tensile stress rapidly decreased and turned into compressive stress. Continuous irradiation partly relaxed the compressive stress and resulted in a saturation value of some -10 8 Pa. With increasing implantation temperature, the buildup of compressive stress gradually vanished, leaving only the initial decrease of tensile stress which finally approached zero. Based on microstructural investigations (TEM and X-ray diffraction) it is proposed to explain this behaviour by the combined action of two processes: relaxation of tensile stress by a volume increase due to irradiation-induced amorphization, and Frenkel defect production and relaxation of compressive stress by irradiation-induced densification of amorphous regions and/or Frenkel defect elimination.

  17. Polarization dependence of multilayer reflectance in the EUV spectral range

    NASA Astrophysics Data System (ADS)

    Scholze, Frank; Laubis, Christian; Buchholz, Christian; Fischer, Andreas; Kampe, Annett; Plöger, Sven; Scholz, Frank; Ulm, Gerhard

    2007-03-01

    The Physikalisch-Technische Bundesanstalt (PTB) with its laboratory at the electron storage ring BESSY II supports the national and European industry by carrying out high-accuracy at-wavelength measurements in the EUV spectral region, particularly to support the development of EUV lithography, which holds the key to the next generation of computer technology. PTB operates an EUV reflectometry facility, designed for at-wavelength metrology of full-size EUVL optics with a maximum weight of 50 kg and a diameter of up to 550 mm and a micro-reflectometry station for reflectometry with sub 10 μm spatial resolution. An absolute uncertainty of 0.10 % is achieved for peak reflectance, with a reproducibility of 0.05 %. For the center wavelength an uncertainty of 2 pm is achieved with a long-term reproducibility of 1.1 pm and a short-term repeatability below 0.06 pm. Measurements at PTB use linearly polarized radiation, whereas EUV optics are operated with unpolarized sources and the status of polarization changes throughout the optical system. Therefore, to transfer these high-accuracy measurements to the EUV optical components under working conditions, it is essential to study the polarization dependence in detail. The degree of linear polarization in the EUV reflectometer is 97%. Representative polarization dependencies obtained on Mo/Si multilayer coatings over a wide range of angles of incidence reveal that the accuracy of calculations with the IMD-code is presently limited by the optical data available.

  18. Investigation of scum type growing defects on attenuated PSM and its prevention

    NASA Astrophysics Data System (ADS)

    Choi, Jihwan; Kim, Yongho; Lee, Dongwook; Jung, Hoyong; Kim, Snagpyo; Yim, Donggyu

    2015-10-01

    The abnormal growing defect (we called this defect 'scum haze defect') in the photomask which is generated during the wafer lithography process is very important issue on semiconductor industry. Because wafer yield loss could be caused by the mask CD variation and the transmittance loss due to the growing defects on the photomask, many studies have been done about the mechanism and the solution of the general type growing defects such as haze and Cr migration so far, However we still need to clarify some abnormal types of the growing defects such as scum haze defect. In this paper, we investigated the generation mechanism and prevention techniques of the scum haze defect on the attenuated phase shift mask. This defect composed of CrOx is caused by the increase of the accumulated exposure energy on photomask. This phenomenon is remarkably similar to the Cr migration on binary mask. But, the apparent difference is that this scum type defect is observed on the attenuated phase shift mask which mainly consists of MoSiON film, and it is difficult to control this defect because of its irregular generation characteristic. Additionally, this defect is not generally removed through the conventional wet cleaning process but it only could be removed by a kind of plasma treatment. In this study, the difference of generation mechanism between the scum haze defect and the general haze was discussed, and the optimal process for controlling scum haze defect in the mask manufacturing was described.

  19. Performance of GFIS mask repair system for various mask materials

    NASA Astrophysics Data System (ADS)

    Aramaki, Fumio; Kozakai, Tomokazu; Matsuda, Osamu; Yasaka, Anto; Yoshikawa, Shingo; Kanno, Koichi; Miyashita, Hiroyuki; Hayashi, Naoya

    2014-10-01

    We have developed a new focused ion beam (FIB) technology using a gas field ion source (GFIS) for mask repair. Meanwhile, since current high-end photomasks do not have high durability in exposure nor cleaning, some new photomask materials are proposed. In 2012, we reported that our GFIS system had repaired a representative new material "A6L2". It is currently expected to extend the application range of GFIS technology for various new materials and various defect shapes. In this study, we repaired a single bridge, a triple bridge and a missing hole on a phase shift mask (PSM) of "A6L2", and also repaired single bridges on a binary mask of molybdenum silicide (MoSi) material "W4G" and a PSM of high transmittance material "SDC1". The etching selectivity between those new materials and quartz were over 4:1. There were no significant differences of pattern shapes on scanning electron microscopy (SEM) images between repair and non-repair regions. All the critical dimensions (CD) at repair regions were less than +/-3% of those at normal ones on an aerial image metrology system (AIMS). Those results demonstrated that GFIS technology is a reliable solution of repairing new material photomasks that are candidates for 1X nm generation.

  20. Reactivity and analytical performance of oxygen as cell gas in inductively coupled plasma tandem mass spectrometry

    NASA Astrophysics Data System (ADS)

    Virgilio, Alex; Amais, Renata S.; Amaral, Clarice D. B.; Fialho, Lucimar L.; Schiavo, Daniela; Nóbrega, Joaquim A.

    2016-12-01

    The reactivity and analytical performance of O2 as cell gas in inductively coupled plasma tandem mass spectrometry was investigated. Selected analytes in a wide mass range were divided in three groups according to their reactivity: G1 represents elements with high oxygen affinity (Ce, La, P, Sc, Ti, and Y), G2 contains elements that may partially react with oxygen (As, Ba, Mo, Si, Sr, and V), and G3 comprises elements expected to be less reactive towards oxygen (Al, Bi, Cu, Mg, Pb, and Pd). On-mass and mass-shift modes were evaluated by monitoring atomic and metal oxide ions, respectively. Analytical signal profiles, oxide percentages, sensitivities and limits of detection for oxygen flow rates varying from 0.1 to 1.0 mL min- 1 were also studied. Group 1 elements plus As and V presented better sensitivities and LODs when measuring oxides, which were the major species for all flow rates evaluated. Molybdenum and Si oxides presented intermediate behavior and MoO fraction was up to 47% and limit of detection was the same as that obtained in on-mass mode. For others G2 and G3 elements, on-mass mode presented higher sensitivity and better LODs, with estimated oxide contents lower than 10%. In most cases, increasing oxygen flow rates led to lower sensitivities and worse LODs.