bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Situ Study of Stresses in Ag/Cu Thin Film Multilayers During Deposition
Authors: Shull Alison L. , Zolla Howard G. , Spaepen Frans 
Published: April 2011

AbstractAg/Cu multilayers are deposited onto a thin Si(100) cantilevered substrate in ultra high vacuum. During deposition, the force per unit width (F/w) in the multilayers is measured continuously from the substrate curvature by a laser scanning technique. Mechanical stability and sample temperature are monitored continuously. The evolution of stress in the film during a layer deposition depends on the thicknesses of the layers beneath it. During deposition of thicker layers of either Cu or Ag, we observe increasing tensile F/w at the start of each layer. The F/w increases up to a few N/m at ∼20 nm layer thickness, and then decreases. When the thickness of each layer is less than 30 nm, the tensile stress sometimes continues to decrease even after a new interface is created. This result does not support a model for the origin of compressive stress that is based on coherent propagation of compressive strain.
Effect of Structure, Stress, Strain, and Alloying on the Hardness of Fe(001)/Pt(001) Epitaxial Multilayers
Authors: Daniels B. J. , Nix W. D. , Clemens B. M. 
Published: April 2011

AbstractThe hardness of epitaxial sputter-deposited Fe(001)/Pt(001) multilayers grown on single crystal MgO(001) has been previously evaluated as a function of composition wavelength, Λ. Nanoindentation results reveal that the hardness is enhanced over that expected from a simple rule of mixtures by a factor of approximately 2.5 for bilayer spacings from 20 to 125 Å. In this paper we investigate possible causes of this hardness enhancement by determining the stress, strain, and alloying in each layer of the multilayer as a function of Λ. Accurate in-plane and out-of-plane lattice parameter measurements were obtained via x-ray diffraction using synchrotron radiation. The stress state and the extent of alloying in each layer as a function of Λ was determined by using the appropriate elastic constants for each component. The stress, strain, and amount of alloying in the Pt layer were near zero for 25≤Λ≤121 Å. The Fe layer exhibited large stresses and strains which relaxed with increasing Λ for 44≤Λ≤121 Å. For Λ=25 Å, the metastable FCC structure was adopted by the Fe film. The amount of alloying also varied from approximately 11 at.% Pt for Λ=44 Å to 5 at.% Pt for Λ=121 Å. Since the structure, film stress, amount of strain relaxation, and extent of alloying vary over this range of Λ while the hardness does not, we conclude that the hardness enhancement in these films must be controlled by other factors. Nevertheless the investigation of these basic film properties has enhanced our understanding of the structure-property relationships that give rise to strengthening in multilayer thin films.
Three Dimensional Surface Waviness of an Epitaxial Layer Due to Surface Diffusion Induced by Interface Misfit Dislocations
Authors: Jonsdottir F. 
Published: April 2011

AbstractIt has been observed that, for some strained epitaxial layer systems, the surface of the layer develops roughness or waviness which correlates spatially with the positions of underlying interface misfit dislocations which partially relax the elastic mismatch strain. A model based on redistribution of mass by surface diffusion is analyzed to estimate the waviness of the three dimensional thermodynamic equilibrium surface due to intersecting arrays of interface misfit dislocations.
Effect of Mechanical Stress on Electromigration Failure Mode During Accelerated Electromigration Tests
Authors: Pramanick S. , Brown D. D. , Pham V. , Besser P. , Sanchez J. , Bui N. , Hijab R. , Yue J. T. 
Published: April 2011

AbstractThe electromigration failure mode and failure rate during accelerated electromigration testing is expected to be strongly affected by the mechanical stress state of Al lines, since tensile stress and compressive stress states favor void growth and hillock formations (extrusions), respectively. During electromigration testing, the mechanical stress state or evolution of mechanical stress of an interconnect is a function of current density and temperature, the two principal variables in electromigration testing. In our experiments, we have observed two different electromigration failure modes by varying the current density and temperatures where (i) the passivated Al lines tested at high current density and high temperatures failed by extrusion or hillock type failure and (ii) the interconnect lines tested at low current density and moderate temperature failed by voiding. A mechanical stress model which incorporates both the thermally generated stress and electromigration induced mechanical stress is invoked to explain the electromigration failure mode selection observed in our experiments.
Stress Effects in Drying Polymer Films
Authors: Tam S. Y. , Scriven L. E. , Stolarski H. K. 
Published: April 2011

AbstractA model is developed to predict the magnitude and pattern of stress due to drying of polymer films. This model combines diffusion-and-convection equation with large deformation elasto-viscoplasticity, utilizing concentration dependent elastic and viscoplastic material properties to better represent the behavior of drying thin films.The results show that the highest stress occurs at film surface where the concentration depletion is the highest. The magnitude of this stress is induced by increasing mass transfer across the film surface but reduced by increasing diffusion coefficient. The edge effect is significant but local, limited to about four film thicknesses. Similarly, change in substrate induces extra stress.
Indentation Creep of Molybdenum: Comparison Between Thin Film and Bulk Material
Authors: Yoder K. B. , Stone D. S. , Lin J. C. , Hoffmann R. A. 
Published: April 2011

AbstractIndentation creep, load relaxation, and rate-change experiments probe room temperature and 80°C creep properties of a 1.3 μm-thick molybdenum film on silicon. The film, with 0.51 GPa compressive stress, 8 GPa hardness and estimated 40 nm grain size, was deposited using steered-arc evaporation at -17V bias. Despite its small grain size and high hardness, the thin film behaves like bulk molybdenum does: the rate sensitivity of the hardness is only weakly-dependent on measurement path (as with bulk material), and activation volumes calculated based on strain rate sensitivity are consistent with those of bulk molybdenum We suspect deformation mechanisms are similar to those in bulk molybdenum under similar conditions.
Hydrogen Effects on the Fracture of Thin Tantalum Nitride Films
Authors: Moody N. R. , Venkataraman S. K. , Bastasz B. , Angelo J. E. , Gerberich W. W. 
Published: April 2011

AbstractIn this study we used nanoindentation and continuous microscratch testing to determine the effect of hydrogen on the work of adhesion and fracture toughness of thin tantalum nitride films. These films were sputter-deposited on sapphire substrates to a thickness of 600 nm followed by the heating of some films in deuterium and some in vacuum at 300°C. Deuterium was used in this study because it is much easier to detect and measure than hydrogen. Ion beam spectroscopy showed that exposure to deuterium produced a uniform internal deuterium concentration of 2000 appm. Nanoindentation showed that exposure to deuterium at 300°C and vacuum annealing at 300°C had little effect on elastic modulus and hardness values of these films at room temperature. In contrast, the microscratch tests at room temperature revealed that the work of adhesion decreased from 24.5 J/m2 after vacuum annealing to 9.1 J/m2 after deuterium charging and demonstrated that tantalum nitride films have a strong susceptibility to hydrogen embrittlement.
Influence of Aging Processes on Adhesion Properties of Metallic and Oxidic Thin Films
Authors: Ottermann C. R. , Tomita Y. , Ishiyama M. , Bange K. 
Published: April 2011

AbstractAdhesion of oxidic and metallic films with thicknesses between 40 nm and 350 nm has been investigated by means of a scratch-test method based on a vibrating diamond micro-indenter. SiO2 and TiO2 films are precipitated on fused silica substrates by sol-gel techniques (SG), reactive evaporation (RE), reactive low-voltage ion plating (IP), and plasma impulse chemical vapour deposition (PICVD), and Cr-layers are produced by rf magnetron sputtering (SP). The influence of aging effects on film adhesion is investigated in respect of several conditions, like storage under ambient surroundings with differences in relative humidity or temperature treatment. A method is presented allowing control of the long-term stability of the scratch-test conditions. Temperature treatment up to 600 °C is found to have the most significant impact on adhesion properties. Adhesion increases for some SiO2 films, whereas for TiO2 layers an opposite behavior is observed. Here, the adhesion of the originally amorphous titania films is reduced due to the phase transition to polycrystalline anatase, which correlates with a significant increase in film stress.
Die Attach Adhesion and Void Formation at the Gaas Substrate Interface
Authors: Strifas Nickolaos , Christou Aris 
Published: April 2011

AbstractA model is constructed to consider the stresses (analytically and with Finite Element Analysis (MiA)) which result from the thermal mismatch between the die and the substrate. FHA is used to simulate thermal stresses induced from temperature cycling with voids and without voids in the die-attach at the die-substrate interface. Local stress concentration caused by voids is found to be dependent on the location of the voids. The presence of an edge void at the die-attach interface changes the local stress and creates a longitudinal stress field. It is also observed that for die-attachment without voids or some center voids there will be no cracking whereas specimens with voids near the edge of the die are likely to have vertical die cracks. Using the void growth, stress relaxation equations, the void growth is simulated yielding an exponential relationship to void grow th and a saturation of void volume w ith time. Stress relaxation and void growth during cool down are simulated, once the material parameters and cooling rates are known. It yields a time dependence of the relative void volume (exponential decay).
Shape Memory Behavior of Ti-Ni Thin Films Annealed at Various Temperatures
Authors: Ishida A. , Takei A. , Sato M. , Miyazaki S. 
Published: April 2011

AbstractTi-Ni thin films with three different types of compositions, titanium-rich Ti-Ni, near equiatomic TiNi and nickel-rich Ti-Ni were prepared by sputtering. The sputter-deposited films were annealed at various temperatures between 773 and 973K in order to crystallize. After the heat treatment, the shape memory behavior was examined with a thermomechanical tester. The shape memory behavior of the near equiatomic composition films was not affected by the heat treatment. On the other hand, the shape memory behavior of the other composition films strongly depended on the annealing temperature. As the annealing temperature increases, the martensitic and reverse martensitic transformation temperatures of the nickel-rich films decreased and those of the titanium-rich films increased. These opposite behaviors of the transformation temperatures can be explained by the opposite dependence of the precipitation of the second phase on the annealing temperature. All the nickel-rich films exhibited good shape memory effect over a wide range of stress, while all the titanium-rich films exhibited a small plastic strain only in the stress range where the shape changes associated with both the R-phase and the martensitic transformations were observed.
An Experimental Examination of Mems Microactuator Material Issues
Authors: Cooney T. G. , Glumac D. E. , Robbins W. P. , Francis L. F. 
Published: April 2011

AbstractThermally induced interactions between materials in complex microactuator structures were investigated. The device structure contained a combination of a piezoelectric layer (lead zirconate titanate - PZT) an electrode with adhesion layer (Pt/Ti), buffer layer (SiO2 or TiO2), structural material (polysilicon and/or silicon nitride), and sacrificial oxide (SiO2). The presence of a SiO2 sacrificial layer did not affect either the bottom electrode or PZT layer. XRD results showed significant platinum and titanium silicide formation in the Pt/Ti electrode at 700 °C (PZT crystallization temperature) on both polysilicon and silicon nitride structural materials when no buffer layer was used. Auger analysis shows that the Ti adhesion layer oxidizes, that measured levels of silicon increase in the electrode zone, and that electrode elements diffuse into the structural material. Buffer layers of SiO2 (0, 0.1, 0.73, 1.3, 1.5 μm) and amorphous TiO2 (0.065 μm) were inserted between the electrode and the structural material. XRD and sheet resistance measurements demonstrated that SiO2 thicknesses greater than 0.73 μm reduced pyrochlore formation in the PZT and reduced the degradation of the electrode. However, this thickness was incompatible with overall surface micromachining processes. The TiO2 layer effectively prevented pyrochlore formation and electrode degradation, while being compatible with overall actuator processing.
Electrical Characteristics of Barium Strontium Titanate-Oxide Composite Films
Authors: Sengupta S. , Sengupta L.C. , Stowell S. , Vijay D.P. , Desu S.B. 
Published: April 2011

AbstractIn a previous work. composites of BSTO combined with other nonelectrically active oxide ceramics have been formulated and have demonstrated adjustable electronic properties which can be tailored for use in various electronic devices. One application has been for use in phased array antennas and insertion has been accomplished into several working antenna systems. To further accommodate the frequencies required by these phased array antennas, thin films of the composites have been fabricated using a Krypton Fluoride excimer laser as an ablation source. The electrical properties, including the dielectric constant and the tunability (change in the dielectric constant with applied voltage) have been measured. The results have been compared to those obtained for the bulk, ceramic composites and other BSTO/oxide composite thin film structures.
Relationship Between the Ductility and Impurity Hydrogen in Ni3Al
Authors: Chikaizumi R. , Itoh G. , Kanno M. , Okada H. 
Published: April 2011

AbstractTensile tests were carried out on B-doped and undoped Ni3Al having different hydrogen contents in order to examine whether the amount of impurity hydrogen affects the ductility of Ni3Al. Specimens were melted either in a high vacuum of ∼10−3Pa or argon, isothermally forged and finally annealed for 15hr at 430°C in an ultra high vacuum of ∼10−3Pa or in argon, respectively. Measurement of hydrogen gas evolved from the specimen during the annealing at 430°C in an ultra high vacuum of ∼10−7Pa confirmed that vacuum treated specimen had actually smaller hydrogen content than the argon treated one. The ductility of vacuum treated specimens both B-doped and undoped was found to be larger than that of argon treated ones, which means a detrimental influence of hydrogen. Hydrogen evolution behavior during the test on B-dopcd specimens in an ultra high vacuum of ∼10−8Pa revealed that the amount of hydrogen gas evolved at the moment of fracture was smaller in vacuum treated specimens than in argon treated one. Impurity hydrogen atoms were considered to move and enhance the formation and growth of voids, accelerating transgranular fracture.
Service Limitations for Oxidation Resistant Intermetallic Compounds
Authors: Smialek J. L. , Nesbitt J. A. , Brindley W. J. , Brady M. P. , Doychak J. , Dickerson R. M. , Hull D. R. 
Published: April 2011

AbstractOxidation resistant intermetallic compounds based on NiAl, TiAl, and MoSi2 are of interest for high temperature applications. Each system exhibits different life-limiting degradation modes due to oxidation. β-NiAl forms protective α-Al2O3 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. Ti3Al and TiAl compounds form less protective mixed TiO2 and A12O3 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. MoSi2 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 MoO2–SiO2 scales in pores and microcracks.
Microstructure/Oxidation/Microhardness Correlations in γ-Based And ツ-Based Ai-Ti-Cr Alloys
Authors: Brady Michael P. , Smialek J. L. , Humphrey D. L. 
Published: April 2011

AbstractThe relationships between alloy microstructure and air oxidation kinetics and alloy microstructure and microhardness in the Al-Ti-Cr system for exposures at 800°C and 1000°C were investigated. The relevant phases were identified as τ (Ll2), γ (Ll0), r-Al2Ti, TiCrAl (laves), and Cr2Al. Protective alumina formation was associated with τ, Al-rich TiCrAl, and γ/TiCrAl mixtures. Brittleness was associated with the TiCrAl phase and τ decomposition to Al2Ti + Cr2Al. It was concluded that two-phase γ + TiCrAl alloys offer the greatest potential for oxidation resistance and room temperature ductility in the Al-Ti-Cr system.
Stoichiometry and Alloying Effects on the Phase Stability and Mechanical Properties of TiCr2-Base Laves Phase Alloys
Authors: Chen Katherine C. , Allen Samuel M. , Livingston James D. 
Published: April 2011

AbstractTi-Cr alloys near the TiCr2 composition have been studied to determine the single-phase Laves field and the associated defects accompanying off-stoichiometry. A combination of metallography, x-ray diffraction, lattice parameter measurements, density measurements and electron microprobe analysis have been used to establish a narrow single-phase region extending towards Ti-rich compositions. All three Laves crystal structures (C14, C36 and C15) were found to exist at different temperatures. Hardness and fracture toughness values determined by Vickers microindentation were studied as a function of alloy composition. Effects of adding Fe, Nb, Mo, and V to TiCr2 on lattice parameter, crystal structure, hardness and fracture toughness are reported.
Numerical Simulations of Tensile Deformation Behavior in Two Phase α2 + γ Lamellar Tial Alloys
Authors: Kad Bimal K. , Dao Ming , Asaro Robert J. 
Published: April 2011

AbstractDeformation microstructures in γ-TiAl + α2Ti3Al based fully lamellar (FL) and nearly lamellar (NL) microstructures have been simulated using micro-mechanical methods. The deformation is extremely inhomogenous resulting in a large accumulation of hydrostatic stresses at the grain boundaries, thereby promoting intergranular fracture initiation. In particular, the increase in ductility with increasing equiaxed γ-grain volume fraction (with compliant deformation characteristics) in nearly lamellar alloys is explained by the reduction of the hydrostatic stress buildup at the boundaries, consequently mitigating fracture.
Extension of the Two Parametric Approach to Fatigue Crack Growth in Intermetallics
Authors: Sadananda K. , Vasudevan A. K. 
Published: April 2011

AbstractFatigue crack growth in intermetallics and their composites published in the literature have been examined in the light of the new concepts developed by the authors. It is shown that the two parametric approach can adequately account for the observed behavior without resorting to an extraneous factor such as crack closure. Implication of the two parametric approach in design is discussed.
The Phenomenon of Superplasticity in Feal-Ti Alloy with Large Grains
Authors: Li Dingqiang , Shan Aidang , Liu Yi , Lin Dongliang 
Published: April 2011

AbstractThe phenomenon of superplasticity in an ordered FeAl based alloy is reported in this paper for the first time. The behavior of superplastic deformation for the FeAl based alloy (Fe-36.5at.%-2at.%Ti) with large grains of above 300 μm has been examined at 1000°C in a strain rate range from 1.39×10− 4 /s to 2.78×l0−2 /s. The maximum elongation of 208% for the FeAl based alloy with large grains has been obtained and the index of strain rate sensitivity, the m value, has a range of values from 0.25 to 0.42. The reason for the large elongation is ascribed to the dynamic recovery and recrystallization during deformation in this large grained alloy at high temperatures.
Atomistic Simulation of Defect Structure in Ternary Intermetallics
Authors: Jones Chris C. , Ternes J. K. , Farkas D. 
Published: April 2011

AbstractInteratomic potentials of the Embedded Atom type were used to study defect structure in ternary intermetallics. Interatomic potentials with appropriate inner consistency were developed for the modeling of ternary systems. Alloys were considered in the Nb-Al-Ti and in the Ni-Al-Ti systems. The stability of ternary phases in these systems was studied, particularly the B2 phase in Nb rich alloys of the Nb-Al-Ti system. The effects of increasing Ti additions in these alloys were studied, as well as the APB energies in these ternary alloys.
Atomistic Study of Cleavage and Dislocation Emission in NiAl
Authors: Ludwig M. , Gumbsch P. 
Published: April 2011

AbstractThe atomistic processes during fracture of NiAl are studied using a new embedded atom (EAM) potential to describe the region near the crack tip. To provide the atomistically modeled crack tip region with realistic boundary conditions, a coupled finite element - atomistic (FEAt) technique [1] is employed. In agreement with experimental observations, perfectly brittle cleavage is observed for the (110) crack plane. In contrast, cracks on the (100) plane either follow a zig-zag path on (110) planes, or emit dislocations. Dislocation generation is studied in more detail under mixed mode I/II loading conditions.
Serrated Yield Behavior in Nial Single Crystal
Authors: Brzeski J. M. , Hack J.E. , Darolia R. 
Published: April 2011

AbstractDynamic strain aging has been characterized in standard purity NiAl single crystals during compression testing. The activation energy for the process suggests carbon and oxygen as the most likely agents. Experimental data is compared with a recent model and implications for the fracture behavior of NiAl are considered.
Characterization of Deformation Structures in B2 CoAL
Authors: Crimp M. A. , Zhang Y. 
Published: April 2011

AbstractB2 CoAl single crystals with a number of orientations have been deformed at 1300 K and 1000 K. The deformation substructures have been characterized using TEM diffraction contrast techniques supported by image simulations. While <100> slip is found to be the predominant slip mode at these temperatures, <111> and <110> dislocations have also been observed. In particular, in hard orientations <110> dislocations appear to play an active role in initiating the deformation. Additionally, <110> dislocations are often observed as junctions of <100> type dislocations. Under the conditions tested, changes in alloy stoichiometry do not result in any modifications to the dislocation slip behavior.