bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Route to the Preparation of Nanophase Composites via Layered Double Hydroxides
Authors: Isupov V. P. , Tarasov K. A. , Mitrofanova R. P. , Chupakhina L. E.
Published: April 2011

A promising route to the preparation of nanophase composites with fine particles of transition metals via layered double hydroxides has been shown on the derivatives of Li-Al double hydroxide, LADH-X, where interlayer X anions are complexes of transition metals. Thermal decomposition of such materials in vacuum or an inert gas leads to dehydration and dehydroxylation of the hydroxide matrix and to the collapse red/ox process of the complex anion. The latter results in the carbonisation of the samples and in the appearance of nanoscale (20–500Å) metal particles.
The Yield Stress of the Fully-Lamellar Microstructure
Authors: Sun Y. Q.
Published: April 2011

This paper is an inquiry into the relationship between the yield stress and the two length parameters in the fully-lamellar polycrystalline microstructure, the grain-size dCB and the lamellar thickness dLM. Deformation in the multilayer structure is assumed to proceed by dislocations propagating in the formation of a succession of mutually interacting pileups, blocked at the lamellar interfaces and piled-up ultimately against the grain boundary. An important case suggested is a yield stress independent of the grain size, sensitive only to the lamellar spacing.
Fracture Toughness of Stoichiometric, Non-Stoichiometric and Ternary-Alloyed Al2Ti
Authors: Ma J. C. , Lukitsch M. J. , Ambrow C. E. , Benci J. E.
Published: April 2011

Polycrystalline stoichiometric Al2Ti was produced via casting or powder metallurgy and further processed yielding material in six conditions. The fracture toughness of the six material conditions was determined from the critical load to initiate cracks with a Vickers indenter. The results show a strong dependence on material condition. Powder processed Al2Ti exhibits the highest fracture toughness value among the material conditions studied.

Polycrystalline non-stoichiometric Al2±yTi1±y and ternary-alloyed Al2Ti + X were prepared in as-cast and cast & annealed conditions. Each material condition exhibited a multiphase microstructure. The composition of the phases present in each alloy was analyzed with SEM/EDS. Fracture toughness values of cast & annealed stoichiometric and non-stoichiometric binary alloys are 20–30% greater than as-cast stoichiometric Al2Ti. For the ternary alloys, the fracture toughness values show a strong dependence on the ternary element used and heat treatment condition. The fracture toughness values of three hot forged ternary alloys were also determined.
Nanocrystalline TiAl Compacts Prepared by Hddr and Hot Pressing
Authors: Aoki K. , Itoh Y. , Kawamura Y. , Inoue A. , Masumoto T.
Published: April 2011

Nanocrystalline TiAl powder was formed by the modified HDDR (hydrogenation-disproportion-dehydrogenaton-recombination) method utilizing ball milling in a hydrogen atmosphere. That is, TiAl compound powder decomposed into TiH2 and Al-rich TiAl powders by mechanical grinding in a hydrogen atmosphere (HD process). Dehydrogenaton-recombination (realloying) resulted in the formation of nanocrystalline TiAl powder when heated to about 700 K in an argon atmosphere (DR process). Almost fully dense nanocrystalline TiAl compacts were prepared by a combination of HDDR and hot-pressing at 873 K which is lower than the usual consolidation temperature by about 300 K. The TiAl compact thus made was brittle in the as-pressed state but showed compressive ductility after annealing.
Al-21Ti-23Cr High-Temperature Protective Coating on TiAl Intermetallic Compounds by RF Magnetron Sputtering
Authors: Park J. Y. , Lee H. N. , Park S. W. , Oh M. H. , Wee D. M.
Published: April 2011

Ti-48A1 specimens were coated with Al-21Ti-23Cr film at 200 W, 0.8 Pa and 573 K by RF magnetron sputtering. The oxidation behavior of the coated specimens was investigated through isothermal and cyclic oxidation tests, and the tensile deformation properties of the coated specimens were also investigated before and after oxidation. The isothermal and cyclic oxidation curves showed that the Al-21Ti-23Cr film was very effective in decreasing the oxidation rate of Ti-48A1. This excellent oxidation resistance is attributable to the formation of a protective Al2O3 layer on the surface of the Al-21Ti-23Cr film. It was found from the results of the tensile test that the protective Al2O3 layer on the surface of the Al-21Ti-23Cr film enabled the Ti-48A1 to maintain its tensile properties in an oxidizing environment.
Transient Creep Behavior of γ-TiAl Polycrystals
Authors: Viguier B. , Bonneville J. , Spätig P. , Martin J. L.
Published: April 2011

Two types of transient creep experiments performed along stress-strain curves are described and successfully applied to γ TiAl polycrystals at room temperature. They allow to determine activation volumes in good agreement with those measured through successive load relaxation tests. In addition, the combination of the latter method and the present ones provides relevant values of the plastic strain hardening coefficient. This latter parameter is found to exhibit similar values in transient as well as during constant strain rate tests.
Annealing of Cold-Rolled Fe-40A1 Single Crystals
Authors: Yang Y. , Baker I.
Published: April 2011

Single crystals of Fe-40A1 were cold-rolled to plastic strains in the range 5% to 48%. Discs cut from the rolled crystals at different rolling strains were heated at 10 K/min in a differential scanning calorimeter from room temperature to 973 K. Three exothermic peaks were observed in the temperature ranges of 440–550 K, 610–650 K, and 860–930 K, all the peaks shifting to lower temperatures with increasing strain. The origins of these peaks are discussed in terms of the disorder and vacancies introduced during rolling.
The Ductility of Stoichiometric and Ni-Rich Polycrystals of Ni3Al: The Effect of Strain Rate
Authors: Schulson E. M. , Xu Y.
Published: April 2011

Polycrystals of stoichiometric Ni3Ai are brittle in air at room temperature, at least at strain rates from 10-4 s-1 to 7 s-1. This is indicative of intrinsic brittle behavior. Nickel-rich (Ni24A1) polycrystals, on the other hand, undergo a brittle-to-ductile transition upon raising the strain rate to above about 10-2 s-1. It is argued that the transition reflects the suppression of environmental embrittlement, not of the intermetallic per se but of a Ni-rich solid solution that decorates the grain boundaries of the off-stoichiometric alloy.
Orientation Dependence of High Temperature Creep Strength and Internal Stress in Ni3Al Alloy Single Crystals
Authors: Miura Seiji , Peng Zhi-Lun , Mishima Yoshinao
Published: April 2011

High temperature creep behavior of a nickel-rich Ni3(Al,Ta) with the L12 structure is investigated in order to clarify the influence of crystallographic orientation with respect to the stress axis. The single crystals with four different orientations are deformed in compressive creep at temperatures ranging from ‘M 23 to 1273 K under a constant load, initial shear stress being 35 to 120 MPa for (111)[101] slip system. The results show a distinct orientation dependence of creep strength, although shape of creep curves, stress exponent and the activation energy seem to be independent of the orientation. It is shown, however, the internal stress, being measured by strain transient dip tests, is found to be orientation dependent and the creep behavior is independent on orientation if it is interpreted using the effective stress instead of the applied shear stress.
Lattice Defects Affecting Moisture-Induced Embrittlement of Ni-based L12 Ordered Intermetallics
Authors: Takasugi T. , Hanada S.
Published: April 2011

Moisture-induced embrittlement of Ll2 alloys (such as Ni3(Si,Ti) and Ni3AI) is observed by tensile test and SEM fractography. A variety of microstructures were prepared by selecting pre-deformation and heat treatment conditions. It is shown that tensile ductility and the associated fractography depend on structure as well as test atmosphere. Well-annealed specimens are susceptible to moisture-induced embrittlement while pre-deformed specimens are resistive to moisture-induced embrittlement. Also, this embrittlement is generally sensitive to the heat treatment scheme preceded by the pre-deformation. Results indicate that the embrittlement occurs when hydrogen is enriched on grain boundaries. On the other hand, the embrittlement can be suppressed when hydrogen is trapped at lattice defects such as dislocations and vacancies. These results are discussed in association with the kinetics of hydrogen in the pre-deformed microstructure.
Effect of Microstructure on the Properties of MoSi2 and its Composites
Authors: Newman A. , Jewett T. , Sampath S. , Herman H.
Published: April 2011

The effects of processing on the microstructure and properties of MoSi2 are examined. A diverse array of samples, processed through a variety of means, were investigated for their microstructural features and indentation fracture behavior. Results from this study indicate that a finely dispersed secondary phase enhances tortuous crack paths, crack branching, and microcracking, thereby improving fracture toughness. The effects of substitutional alloying (Re, Al) and composite additions (SiC) have also been investigated.
Comparison of NbCr2 and HfV2 C15 Laves Phases
Authors: Thoma D. J. , Chu F. , Wills J. M. , Mitchell T. E.
Published: April 2011

The elastic properties, phase stability, and alloying behavior of NbCr2 and HfV2 C15 Laves phases have been investigated with a combined experimental and theoretical approach. Experimental results indicate that HfV2 has anomalous elastic properties as well as a structural instability, but NbCr2 does not. In addition, ternary phase fields of NbCr2 with V and HfV2 with Nb were examined experimentally, and they have substantially different alloying behavior. In order to understand these experimental phenomena, the total energy and electronic structure of C15 NbCr2 and HfV2 were calculated using the linear muffin-tin orbital method with the atomic sphere approximation. Calculation results suggest that the phase instability of HfV2 is induced by phonon softening, and the anomalous elastic properties of HfV2 appear to be attributed to a doubly degenerate electronic energy level with a linear dispersion relation very close to the Fermi level. Finally, density of states plots indicate that for HfV2, some bonding d-states are unoccupied while for NbCr2, all bonding and some anti-bonding d-states are occupied. The bonding difference may be responsible for the alloying behavior in the two Laves phase alloys. As a result, alloy design schemes are suggested for enhanced deformability in Laves phases.
Ti-Modified Niobium-Silicide Based Directionally Solidified in-situ Composites
Authors: Bewlay B. P. , Jackson M. R. , Lipsitt H. A.
Published: April 2011

This paper examines microstructure-property relationships in high-temperature directionally solidified (DS) in-situ composites based on Nb silicides, such as Nb3Si and Nb5Si3. These in-situ composites are based on the Nb3Si-Nb binary eutectic, and are alloyed with Ti. They were prepared using cold crucible Czochralski crystal growth. Ternary Nb-Ti-Si alloys with Ti concentrations from 9 to 45%, and Si concentrations from 10 to 25%, were directionally solidified to generate aligned two- and three-phase composites containing a Nb solid solution with Nb3Si and Nb5Si3 silicides. Fracture toughness values generally greater than 10 MPa√m were measured in these composites. For a given Si concentration, the fracture toughness of the Ti-containing composites was increased ∼ 6 MPa√m over that of the binary alloy composites. The effects of Si concentration, and a range of Nb:Ti ratios, on microstructure, phase equilibria, and fracture toughness were examined.
Determining the Morphology and the Interaction Between Terminally-Anchored Polymer Layers
Authors: Balazs A. C. , Singh C.
Published: April 2011

Using a two dimensional self-consistent field theory, we investigate the interactions between two planar surfaces that are coated with terminally-anchored homopolymers. One surface is coated with A chains and the other is covered with B homopolymers. The chains are grafted at low densities and the B polymers are chosen to be solvophobic, while the A chains are relatively solvophilic. We determine the morphology of the layers and the energy of interaction asthe surfaces are compressed. Our results provide guidelines for controlling the interaction between polymer-coated colloidal particles.
The Effect of Chemical Functionality on Adhesion Hysteresis: A Study using the JKR Method
Authors: Kim Soojin , Young Choi Gun , Nezaj Jeff , Ulman Abraham , Fleischer Cathy
Published: April 2011

The adhesion of crosslinked PDMS surfaces to self-assembled monolayers with different chemical functionality was investigated using the JKR method, the contact mechanics of solids spreading their interfacial area under load. Interfacial H-bonding was shown to be an important chemical interaction causing significant adhesion hysteresis. The number of H-bonds between PDMS and silanol groups on SiO2/Si surfaces increased with time of the contact under a constant load, indicating pressure-induced reorganization of the PDMS network near the interface. The interaction between PDMS and carboxylic acid groups showed somewhat smaller hysteresis which suggests weaker H-bonding strength. The interaction between PDMS and functionalized biphenyl groups exhibited small hysteresis which is believed to be caused by dipolar interaction. whereas that between PDMS and nonpolar perfluorocarbon groups showed negligible hysteresis. The distinction in the behavior of the unloading data between H-bonding related interaction and dipolar interaction seems to indicate the difference in the nature between non-specific (van der Waals, dipolar) and specific (donor-acceptor, H-bond, acid-base) interactions.
Phase Separation Kinetics During Drying
Authors: Saraf R. F. , Ostrander S. , Feenstra R. M.
Published: April 2011

Kinetics of phase separation at air/polymer interface in a binary polymer mixture on evaporation of common solvent is studied. The lateral dimension of the highly anisotropie, pancake-like, minority phase increases with a growth exponent of 2/3 identical to ‘late-stage’ growth under (classical) thermal-quench at interface. In contrast to the thermal-quench, during drying the kinetics depends on the initial condition (i.e., initial concentration, Co) that is rescaled to obtain a master-curve.
Ancient Medical Instruments: An Overview and Case Study
Authors: Notis M. R. , Jakielski K. E.
Published: April 2011

An overview of the development of the materials used for surgical knives is presented. Because early surgical tools are hard to recognize in terms of specific function, unless they are found in context they are difficult to identify. A rare exception is the collection of Roman surgical implements found in Pompeii. In order to demonstrate the level of technology typical ofthat time, metallographic study has been performed on an object identified as a Roman surgical probe similar to those found in Pompeii. The composition, microstructure, and fabrication technology for this object is discussed in relation to its functional use.
The Design of a Monitoring Program for Iron Alloys on Underwater Historic Shipwrecks in Fathom Five National Marine Park, Ontario, Canada
Authors: Stewart John , Murdock Lome D. , Binnie Nancy
Published: April 2011

In order to design a scheme to monitor the state of preservation of iron alloys that are found on historic shipwrecks sunk in fresh water, it was first necessary to identify the predominant form of corrosion found on the wrecks. This was done by visual observation, in situ surface pH measurements, and X-ray powder diffraction of the corrosion layers. Once the form of corrosion was identified as pitting corrosion, a monitoring scheme based on photographic recording of the rust-red tubercles was designed. This scheme is simple and nondestructive, both necessary characteristics for the monitoring of submerged historic resources.
Examination of Silk Fibers from a Deep Ocean Site: SEM, EDS, & DSC
Authors: Srjnivasan R. , Jakes K. A.
Published: April 2011

The research reported herein is directed toward the determination of the microstructure of silk fibers recovered from the shipwreck site of the S.S. Central America. The structural data obtained from examination of these silk materials using SEM, EDS, and DSC was compared to data obtained from the examination of historic silk fibers (ca. 1860–1880) not exposed to the deep-ocean and of modern silk fibers. Marine silks appear more degraded than historic and modern silk when viewed under the SEM and the fiber surfaces are partially obscured by inorganic deposits. The melting endotherm of marine, historic, and modern silk fibers are comparable to each other, but the glass transition observed in the modern silk is not apparent in the DSC trace of any of the marine silks.
Fracture Surface Topography of Energetic Materials using Atomic Force Microscopy
Authors: Lanzerotti M. Y. D. , Meisel L. V. , Johnson M. A. , Wolfe A. , Thomson D. J.
Published: April 2011

Height profiles spaced 0.008 μm apart across the fracture surface of TNT melt-cast in polycarbonate sleeves have been obtained with an atomic force microscope (AFM). Spatial power spectra (wavelengths of 0.016 μm to 4.0 μm) have been calculated using both a prolate spheroidal data window and a Kaiser window in the horizontal space domain prior to using a fast Fourier transform algorithm. Results based on topographical profiles across the surface include the following. The power spectral density of the individual fracture surface profiles is found to decrease with increasing spatial frequency over the dimensional region examined, ≈ 1.0 μm−1 to ≈ 10.0 μm−1. The spectral amplitudes are found to have a frequency dependence proportional to f s. The determined values of s in the dimensional region 1–10 μm−1 scatter in the range -1 < s < -4. Those values of s outside the range -3 < s < -2 indicate non-fractal fracture. There is significant structure in the spectra even for those with slopes within the range of a fractal dependence. Both observations are consistent with the appearance of numerous peaks in the spectra that indicate that a substantial amount of the fracture occurs at grain boundaries in the form of large clusters of TNT. Such a fracture process is deterministic.
Atomic Structure of Interfaces in Mazed Au Bicrystals
Authors: Hetherington C.J.D. , Dahmen U. , Penisson J-M.
Published: April 2011

Thin films of {111} Au have been grown on {111} Ge substrates. The film grows epitaxially in two crystallographically equivalent orientations, (111) and (111). After annealing, the film is removed from the substrate and the resulting bicrystal appears as a maze of domains with faceted boundaries mainly of type {112}. The high density of edge-on interfaces in the films makes them well suited to electron microscopy. In the <111> orientation, the 1.44Å spacing of the {220} lattice planes tests the high resolution capabilities of the latest microscopes.

The nature of the Au {111} film contrasts with that of films grown using different materials or different substrates and was found to have a three-dimensional character with the occurrence of extensive twinning on (111) in the plane of the film. Areas were found to thin considerably in the high voltage electron microscope and interfaces in these regions were analyzed and rigid body translations across the facets measured. The existence of distinct rigid body translations across neighboring facets is of particular interest.
Read-Shockley Boundaries in Thin Films
Authors: King Alexander H.
Published: April 2011

When a grain boundary is terminated by a free surface, its behavior may be significantly different than for the same boundary either in an infinite bicrystal, or terminated by triple junctions. In this paper we describe some phenomena related to the free-surface interactions of interfacial dislocations, in thin films. We show that surface relaxation stresses can exert a powerful destabilizing influence upon the dislocation structure of many grain boundaries, and that they can only be made stable if a large lattice friction stress, or other pinning force, resists the motion of the dislocations. Finally, we will show that the only intrinsically stable grain boundary in a thin film is a tilt boundary with its rotation axis parallel to the normal of the film.
Structure and Chemistry of Ti Overlayers on α-Αl2O3(0001)
Authors: Bernath S. , Wagner T. , Hofmann S. , Rühle M.
Published: April 2011

Ti thin films were grown by molecular-beam epitaxy (MBE) on α-Al2O3(0001) substrates. During room temperature deposition, in the very initial growth stage, AES investigations revealed a chemical reaction between the Ti and the α-Al2O3substrate. An analysis of the AES data based on simple assumptions showed that ∼ 2 monolayers of Ti are oxidized. However, HRTEM analysis indicated an atomically smooth, incoherent interface, without a reaction layer. Reflection high-energy electron diffraction (RHEED) analysis revealed an epitaxial orientation relationship (0001)<2110> Ti ∥ (0001)<1010>Al2O3between Ti and α-Al2O3(0001).
Collective Modes Of Misfit Dislocations in Lattice - Mismatched Thin Films
Authors: Hovakimian L. B. , Tanaka Shun-Ichiro
Published: April 2011

We study the nature and spectrum of fundamental vibrational excitations in the assembly of misfit accomodating dislocations. The physical system considered is a Lomer array of equispaced dislocations in a lattice-mismatched interface between a substrate and a thin film with similar elastic properties. Within the framework of the isotropie elasticity theory we calculate the effective force constants of harmonic springs that establish the dynamical correlations between the oscillating dislocations. Our interest is concentrated on the case where the thickness of the overlay er is much less than the separation between the nearest-neighbor dislocations. We show how in this situation the free surface of the film exerts a profound screening influence on the dislocation-dislocation correlations; it is demonstrated that the force constants exhibit sensitive dependence not only on the lattice mismatch, but also on the film thickness. We then deduce the dispersion of collective dislocation excitations and find that the latter propagate along the interface much more slowly than the ordinary sound waves. Our results reveal the manner in which the thickness of the film controls the magnitude of the vibrational quantum that characterizes the natural oscillations of arrayed dislocations. It is shown that this anomalous energy quantum manifests itself in the low-temperature heat capacity of the misfit array.
A Thermodynamic Model for Solid State Amorphization: Application to Ni-Ti Multilayers of Different Microstructures
Authors: Böttger A. , Benedictas R. , Mittemeijer E.J.
Published: April 2011

On the basis of an assessment of both the phase-formation energies and the energies of interfaces and grain boundaries the driving force for solid state amorphization (SSA) in crystalline Ni- crystalline Ti and amorphous Ni- crystalline Ti multilayers was calculated. It followed that the structure of the interfaces and grain boundaries, and thus their energies is of crucial importance for the occurrence (or not) of SSA. The SSA behaviour of the two types of Ni-Ti multilayers upon annealing was investigated using X-ray diffraction and (high resolution) transmission electron microscopy. The crystalline Ni- crystalline Ti multilayers showed SSA at both the Ni-Ti interfaces and the Ti grain boundaries. The amorphous Ni- crystalline Ti multilayers exhibited SSA at the Ti grain boundaries only. These observations agree with the predictions from the thermodynamic model.
Ab Initio Electronic Structure Calculations of the Σ 5 (210) [001] Tilt Grain Boundary in Ni3Al
Authors: Lu Gang , Kioussis Nicholas
Published: April 2011

The atomic and the electronic structure of the Σ 5 (210) [001] tilt grain boundary in Ni3Al have been calculated using the full potential linearized-augmented plane-wave method. The strain field normal to the boundary plane and the excess grain boundary volume are calculated and compared with the results obtained using the embedded-atom method (EAM). The interlayer strain normal to the grain boundary oscillates with increasing distance from the grain boundary. The bonding charge distributions suggest that bonding in the boundary region is significantly different from that in the bulk. The grain boundary energy and the Griffith cohesive energy are calculated and compared with the EAM results.
Stress in Ag/Ni Multilayers: A Comparison of Specimen-Curvature and X-Ray Diffraction Methods
Authors: Gergaud P. , Labat S. , Yang H. , Bottger A. , SandstrÖm P. , Svedberg Erik , Mittemeijer E.J. , Sundgren J.E. , Thomas O.
Published: April 2011

Multilayers and superlattices are of great industrial interest because of their specific properties (magnetic, electronic, tribological…). Multilayers stacking are often in a very high state of intrinsic stress (some GPa) and for reliable integrated devices to be made it is capital to control and understand these intrinsic as well as extrinsic stresses. The objective of the present work is therefore the understanding of the origin of stresses and strains in multilayered metallic materials. Of course, a comparison of the different techniques which can be used for stress determination is a necessary first step of this study. In this aim, we have studied Ag/Ni multilayers, Ag and Ni thin films and Ag/Ni bilayers obtained by sputtering. The stresses have been determined via curvature measurement using both a laser scanning method and X-ray diffraction rocking curves technique, and via X-ray diffraction measurement of several d-spacings which act as in-situ strain gauges (also called the sin2ψ method and related methods). The obtained results from these different techniques are discussed in terms of accuracy, reproducibility and advantages / drawbacks. The obtained stresses from these methods cannot be directly compared and a specific discussion is developed around the relation between the measured strains and stresses and the microstructure of the materials.
Compositional Effects on the Degradation of PVD-Tisin
Authors: McArthur W.F. , Deng F. , Ring K. , Pattison P.M. , Kavanagh K.L.
Published: April 2011

PVD-TixSiyNzfilms formed by reactive RF-magnetron co-sputtering of Ti and Si in Ar/N2are evaluated as a diffusion barrier between Cu and Si. A complete range of compositions are obtained by Ti targets inlaid with Si. Film composition is controlled by the target ratio of titanium to silicon and N2partial pressure. Electrical results versus thermal history for films of∼6–18% Si as well as the composition and microstructure as determined by Rutherford back scattering (RBS), TEM and electron diffraction are reported. These films are an amorphous matrix with imbedded nanocrystals of titanium nitride as-deposited and undergo phase separation to yield titanium nitride and silicon nitride after a 1000°C anneal. As-deposited compositions which lie above the TiN-Si3N4phase line yield crystals of TiN. Compositions below the TiN-Si3N4phase line yield crystals of Ti2N. Bulk resistivity as-deposited (<400μΩ2-cm) is acceptable for use as a contact liner/berrier material and improves with annealing. Si pn-diodes metallized with 20nm Ti40Si15N45 and Cu show no significant increase in reverse leakage current at anneal temperatures below 700°C.
Effects of Nitrogen on Preventing the Crystallization of Amorphous Ta-Si-N Diffusion Barrier
Authors: Kim Dong Joon , Jeong Soon Pil , Kim Yong Tae , Park Jong-Wan
Published: April 2011

Amorphous Ta-Si-N thin film was deposited by dc sputterring of Ta5Si3 target in (Ar+N2) atmosphere. The crystal structure and the thermal stability of Ta-Si-N thin films were investigated by XRD, RBS, AES, Nomarski microscope, and TEM. When the concentration of nitrogen in Ta-Si-N thin film was higher than 40 at.%, the Ta-Si-N thin film remained the amorphous state after the annealing at 1100°C for 60 min. In this case, the Cu diffusion was prevented by the amorphous Ta-Si-N thin film even if the annealing temperature increased up to 900°C for 30 min. Whereas, the Ta-Si-N thin film with nitrogen concentration less than 40 at. % was transformed from the amorphous to the polycrystalline TaSi2 phases after the annealing at 900°C for 60 min and failed to prevent the Cu diffusion after the annealing at 700°C for 30 min.
The Effects of Temperature Ramping on MOCVD Al Film Properties
Authors: Yang D. , Jonnalagadda R. , Mahadev V. , Cale T. S. , Hillman J. T. , Foster R. F.
Published: April 2011

We present and discuss experiments designed to demonstrate the effects of ramping substrate temperature during the deposition of TIBA sourced aluminum on Si(100) and TiNx coated silicon (TiN) wafers. We also present results from experiments in which the precursor flow was pulsed (started and stopped) for a short time at a higher temperature followed by temperature ramp down and deposition at a lower (constant) temperature on TiN wafers. Aluminum growth rates and crystal orientation data are presented for different deposition conditions on Si(100) wafers. Aluminum nucleation densities, crystal orientation, average grain size, surface roughness, growth rate and resistivity data are presented for different deposition conditions on TiN wafers. During substrate temperature ramp down from 673 K on TiN wafers, when the precursor flow was pulsed for a short time at higher temperatures, and then resumed at a lower (constant) temperature 573 K, there was a significant increase in both deposition rates and fraction of (111) orientation. The resistivities of these films were close to that of bulk aluminum. Films deposited during substrate temperature ramp down on TiN substrates resulted in higher fractions of (111) oriention and higher resistivities as compared to the films deposited at constant substrate temperature and during the ramp up of substrate temperature. The films deposited on Si(100) wafers during substrate temperature ramp down from 673 K to 573 K had strong Al(200) orientation.
Improvement of the Long-Term Stability of Polysilicon IC-Resistors by Fluorine Doping
Authors: Rydberg Matts , Smith Ulf
Published: April 2011

In addition to exacting requirements regarding uniformity, precision and matching, thin-film polysilicon resistors for analog telecommunication circuits must be extremely stable. In this paper a new method for improving the stability of polysilicon resistors is presented. It utilizes the strength of the Si-F bond to prevent hydrogen and other impurity atoms from attaching to the dangling bonds in the grain boundaries and is based on individual control of implantation dose and annealing conditions for dopant and fluorine, respectively.

Polysilicon films, 500 nm thick, were implanted with boron at a dose of 51014 cm-2 and annealed at 1000 °C. This was followed by an implantation of fluorine and another anneal. The fluorine dose ranged up to 1·1016 cm-2 and the annealing temperature was varied between 600 °C and 1000 °C.

Resistivity measurements showed that the fluorine annealing temperature has to be higher than 700 °C to reduce implantation damage. The sensitivity of the polysilicon films to hydrogen, an important indication of their electrical stability, was investigated by annealing both in a hydrogen plasma and in a molecular hydrogen ambient. For low hydrogen sensitivity, the fluorine annealing temperature has to be less than 750 °C. The temperature was therefore set to 750 °C so as to strike a balance between a low hydrogen sensitivity and the need for a reduced implantation damage. SIMS measurements showed the amount of fluorine in the film to decrease by two orders of magnitude if the fluorine annealing temperature was 1000 °C, and to remain essentially constant if the temperature was 750 °C. Stress tests were made in order to see the effect of fluorine on the resistivity during actual operating conditions. The stability of the resistors during the stress tests was found to improve by at least a factor of two when fluorine doping was used.
Low Temperature Deposited Highly-Conductive N-type SiC Thin Films
Authors: Cheng Kuan-Lun , Cheng Huang-Chung , Lee Wen-Horng , Lee Chiapyng , Yew Tri-Rung
Published: April 2011

Low-temperature deposited highly-conductive SiC films has long been a goal for many researchers involved in hetero-junction bipolar transistor, thin-film transistor, solar cell.… etc. Here in this paper, we study the influences of the diluted PH3 flow rates on SiC film quality as well as electrical properties. PH+ was determined from residual gas analyzer to be the main dopant source. Phosphorous atoms will play a role of enhancing the SiC grain growth and resulting in a smaller film growth rate. Carrier concentrations increase monotonically with the diluted PH3 flow rates. While Hall mobility first increases than decreases with it due to a combination effect of the impurity scattering and a film quality improvement which dominates when the 1% PH3/H2 flow rate is above or below 40 seem, respectively.
Highly Supersaturated, Highly Strained Sputtered Ag-Co and Ag-Ni Layers
Authors: Velterop L. , Buis A. , Delhez R. , de Keijser Th.H. , Mittemeijer E.J. , Reefman D.
Published: April 2011

Thin Ag-Ni and Ag-Co layers with compositions of 0, 15, 22 to 28 at% Ni or Co were made by magnetron sputtering. TEM experiments revealed that the layers exhibited a {111} fiber texture with a high density of twins, always with the twinning plane parallel to the layer surface. X-ray diffraction and TEM results indicate that all Ni or Co is dissolved in the Ag, although some compositional inhomogeneity occurs: the layers are highly supersaturated with Ni or Co. Unlike the pure Ag layer, the Ag-Ni and Ag-Co layers exhibited high strains in the as prepared state.

Upon annealing Ni or Co precipitated. The Ni precipitates were small, spherical particles oriented parallel to the surrounding Ag. The strains in the Ag-Ni and Ag-Co layers after annealing were less than the calculated thermal strains, but they were larger than the strain in the pure Ag layer after an equal annealing treatment.
AFM Observations of Oxide Morphologies Formed at high Temperatures
Authors: Czerwinski F. , Szpunar J.A.
Published: April 2011

The growth surfaces of oxides formed at high temperatures on metallic substrates with different oxidation resistance were imaged using an atomic force microscope (AFM) in both contact and tapping modes. In addition to differences in morphology of NiO and TiO2 films, and their anisotropy of growth caused by the crystallographic orientation of substrate grains and by the type of substrate grain boundaries, some subtle growth features were documented. These include the nano-size steps of growth on the sidewalls of pyramidal grains of TiO2 and the nucleation at the intersection of NiO grain boundaries with NiO/gas interface. An example of a quantitative description of oxide/gas interface using roughness parameters is presented. This description is used to demonstrate the differences in evolution of oxide growth morphology for NiO doped with Ce growing by inward diffusion of oxygen anions or by outward diffusion of metal cations.
Surface Characteristics, Etching Behaviors and
Chemicalmechanical Polishing of Aluminum Alloy thin Films
Authors: Tseng Wei-Tsu , Wu Jun , Chang Yee-Shyi
Published: April 2011

Etching behaviors of various Al alloy thin films in
H2O2-based acidic etchants are investigated in this
study. The pH and H2O2 content in the etchant are
varied in order to simulate the case where Al thin films are subject to
chemical-mechanical polishing (CMP) using slurries of different
compositions. Corrosion current and thickness of the native oxide on
pure-Al, AI-1%Si, Al-0.5%Cu, AI-1%Si-0.5%Cu, and AI-1%Cu thin films are
determined from Tafel and ESCA analyses respectively. Comparisons between
etch rate and CMP polish rate data suggest that Al-CMP removal process
depends strongly on the chemical reactions by the oxidizer (slurry).
Mechanical abrasion by the abrasive particles plays only an auxiliary role
during Al CMP. In addition, alloy composition (% Si and % Cu) influence both
etching and polishing behaviors to a great extent. The underlying mechanisms
for etching and polishing are discussed.
Chemical Mechanical Cleaning for Post-CMP Applications: Defects
and Metals Results
Authors: Zhao E. Y. , Emami R. , Malik I. , Mishra K. , Krusell W. C. , de Larios J. , Hymes D. J.
Published: April 2011

Double-sided brush scrubbing has become a dominant method for post-CMP
cleaning applications. Chemicals delivered in-situ with brush scrubbing
greatly enhance the cleaning capabilities. In this paper, the effect of
dilute HF on reducing particulate defects and trace metal contamination on
polished oxide surface is studied using a HF-compatible double-sided
scrubber. AFM data on the interaction of dilute HF with oxide / tungsten
plug array after tungsten CMP is also presented. Scrubbing with dilute HF is
shown to be highly effective is removing slurry agglomerates that strongly
adhere to the post-CMP oxide film.
Particulate Removal from Silicon Substrates in
Megasonic-Assisted Dilute SC1 Chemistry
Authors: Kashkoush Ismail , Brause Eric , Grant Robert , Novak Rich
Published: April 2011

This paper demonstrates the use of megasonic energy to enhance particulate
removal in dilute SC1 solutions. Ideal, as well as “real world”, particles
were deposited on silicon wafers to challenge the SCl/megasonic particle
removal system. Different dilute SCI concentrations were used, e.g., 1:4:20,
1:10:120, and 1:1:100. Bath temperature was varied between 50 and 70°C with
megasonic energy kept constant at 800 W. Results showed that the megasonic
energy enhanced the particle removal even in dilute solutions. The chemical
concentrations were shown to be a significant factor and must be monitored
or controlled in dilute SC1 solutions for particle removal to take place. A
lower cost of ownership can be obtained from these techniques as a result of
using dilute chemicals and extending current bath lives.
Effect of Ultra-Dilute RCA Cleans on the Integrity of Thin Gate
Oxides
Authors: Dhayagude Tushar , Chen Weidong , Shenasa Mohsen , Nelms David , Olesen Mike
Published: April 2011

Comparative studies on the effect of Ultra-dilute RCA cleans,
chemical ratios in excess of 300:1, and Dilute RCA cleans,
chemical ratios around 50:1, on the integrity of thin gate oxides have been
performed. Ultra-dilute RCA chemistries have shown particle removal
efficiency, metallic contamination removal, surface roughness, Qbd, BVox and
defect density equivalent to those obtained using dilute RCA chemistries.
Furthermore ultra-dilute chemistries use less chemical leading to shorter
rinse times and thus increased throughput as compared to the dilute RCA
chemistries.
Study on Cu Cleaning Efficacy Depending on Initial Contamination
Method
Authors: Kim J. S. , Morita H. , Joo J. D. , Ohmi T.
Published: April 2011

We investigated a dependence of cleaning efficiency for Cu on the initial
contamination method with different initial concentration and contamination
solution. Through this study, we found that the cleaning efficiency of
typical dissoluble chemical solutions such as O3-UPW, SPM and HPM
for Cu contaminated in diluted-hydrofluoric acid (DHF) was better than for
that in ultrapure water (UPW). And, it is shown that there is a dependence
of cleaning efficiency for Cu contaminated in UPW. The different desorption
behaviors of Cu contaminated in UPW and DHF can be interpreted by the fact
that the Cu is included in metal-induced-oxide (MIO) grown during
contamination in UPW and can not be removed by only dissolution process of
O3-UPW, SPM and HPM solutions which have no etching effect on
SiO2 and Si. In contrast, a relatively low concentration Cu
contaminated in DHF which has no MIO effect can be removed below the
detection limit by only dissolution process of these chemical solutions.
However, Cu contaminated in DHF is dissolved and inserted in the chemical
oxide grown during cleaning process as the initial Cu concentration is a
relatively high. Consequently, we conclude that Cu on Si surface can be
fundamentally removed by just dissolution process of typical dissoluble
chemicals except the amount of Cu inserted in MIO grown during contamination
in UPW and chemical oxide grown in chemical solutions.
In-Situ Chemical Concentration control cor Wafer Wet
Cleaning
Authors: Kashkoush Ismail , Brause Eric , Novak Richard , Grant Robert
Published: April 2011

The continuously increasing integration of today's advanced semiconductors
requires increasingly tight process control in the IC manufacturing steps.
This paper demonstrates the use of conductivity sensors to monitor and
control the chemical concentrations of RCA cleaning and HF etching
solutions. Electrodeless conductivity sensors were used to monitor and
regulate the concentration of these process chemicals. A linear relationship
between the conductivity of the solution and the chemical concentration was
obtained within the range studied. A chemical monitoring and concentration
scheme (ICE-1™) was developed. Different concentrations of RCA and HF
solutions were investigated. Results show that these techniques are suitable
for monitoring and controlling the concentration of chemicals in the process
tanks for better process control. These techniques provide a lower cost of
ownership of the process due to longer bath lives and the use of dilute
chemicals.
Advanced Alkali Cleaning Solution for Simplification of
Semiconductor Cleaning Process
Authors: Morinaga Hitoshi , Aoki Masumi , Maeda Toshiaki , Fujisue Masaya
Published: April 2011

NH4OH/H2O2/H2O (called APM or
SC–1) cleaning combined with megasonic irradiation is found to feature
outstanding removal efficiency for various types of particulate contaminant.
The conventional APM cleaning, however, allows metallic impurity in solution
to adhere onto substrate surface, and it must be followed by acid cleaning
such as HCI/IH2O2/H2O (called HPM or SC–2)
cleaning to remove metallic impurity from substrate. The advanced APM
cleaning using MC–1 which is alkali cleaning agent containing chelating
agent has been developed, and this new cleaning is found capable for
preventing various metallic impurities including Al in solution from
contaminating substrate surface. Besides, with cleaning conditions
optimized, the advanced APM cleaning using MC–1 can also remove metallic
impurity from substrate surface. In short, this modified APM cleaning is
capable for removing particle and metallic impurity at the same time, which
is not possible with the conventional cleaning technology. The cleaning
process of semiconductor manufacturing process can be simplified if HPM
cleaning is eliminated by introducing the advanced APM cleaning using MC–1.
This leads to drastic reduction of cleaning cost and improvement of
throughput of the cleaning process.
Influence of Surface Organic Contamination on the Incubation
Time in Low-Pressure Chemical Vapor Deposition of Silicon Nitride on Silicon
Substrates
Authors: Saga Koichiro , Hattori Takeshi
Published: April 2011

Trace organic contaminants adsorbing on silicon surfaces during
transportation of wafers to a reaction chamber in an air ambient cause
incubation before film growth starts in low-pressure chemical vapor
deposition (LPCVD) of silicon nitride film on silicon substrates. The
incubation time for wafers either exposed to cleanroom air for a long period
without being stored in a box or stored in an outgassing plastic box prior
to LPCVD is longer than that for wafers transported to the CVD reactor
immediately after the previous step. It has been found that the longer
incubation time is attributed to not only extraneous oxide grown on the
silicon surface but also organic contaminants adsorbed on the surface.
Optimization of Post Sulfuric Acid/Hydrogen Peroxide Dump
Rinsing Processes
Authors: Chiarello R. P. , Parker R. , Helms C. R. , Chen W. , Tang S. , Cook L. J.
Published: April 2011

We evaluated the rate limiting steps in a post sulfuric acid/hydrogen
peroxide mix dump rinsing process. The parameters we examined include, the
pull-out velocity from the chemical bath, the draining during transport into
the rinse tank, immersion into the rinse tank, dumping, draining after a
dump cycle and flow rate during fills between dumps. Based on our
investigations an optimized dump rinsing process was developed using
programmed flow rates and dumping cycles. The quality of the optimized
rinsing process was determined by measuring sulfur residue and light point
defects on wafer surfaces that had undergone the optimized rinsing process.
This optimized process requires 5 minutes and 75 liters of water, replacing
a process that initially ran for up to 16 minutes and consumed 600 liters of
water. Our optimized rinsing process, resulted in a factor of five saving in
water consumption and two in cycle lifetime with no statistical degradation
in surface quality.
In-homogeneous precipitation of Iron from SC1
Solutions
Authors: Knotter D. Martin , de Gendt Stefan , Mertens Paul , Heyns Marc M.
Published: April 2011

It is found that Fe in a ppb level Fe-spiked SC1 solution precipitates
in-homogenous. The local high iron concentrations are difficult to rinse,
create micro-roughness, and induce weak spots in capacitors. With AFM it has
been shown that rings of 3–8 μm are etched in the silicon and that the etch
products (silicates) are deposited on one side just outside the ring. The
capacitor yield loss induced by this SC1 treatment can not be recovered
fully by a subsequent SC2 or dHCL step, while a dHF/dHCl does fully recover
the yield and removes the iron and silicate rim.
Measurement and Characterization Techniques for Thermoelectric Materials
Authors: Tritt Terry M.
Published: April 2011

Characterization of thermoelectric materials can pose many problems. A temperature difference can be established across these materials as an electrical current is passed due to the Peltier effect. The thermopower of these materials is quite large and thus large thermal voltages can contribute to many of the measurements necessary to investigate these materials. This paper will discuss the characterization techniques necessary to investigate these materials and provide an overview of some of the potential systematic errors which can arise. It will also discuss some of the corrections one needs to consider. This should provide an introduction to the characterization and measurement of thermoelectric materials and provide references for a more in depth discussion of the concepts. It should also serve as an indication of the care that must be taken while working with thermoelectric materials.