bluuebunny/crossref_metadata_2025 huggingface dataset:
Time-Resolved Luminescence of Oxygen Related Defects in Aluminum Nitride
Authors: Harris J. H. , Youngman R. A.
Published: March 2011

Abtract

A charged defect model for the formation of band-tail states, first proposed by Redfield et al. to understand the optical properties of Si doped GaAs [1], is applied to oxygen doped aluminum nitride (AIN) ceramics. In this case, oxygen substituting on a nitrogen site and (subsequently formed) aluminum vacancies comprise the charged centers. The results of optical absorption edge measurements as well as steady state and time-resolved luminescence between 10 and 300K are used to support this model. Finally, it is noted that the mixed covalent and ionic nature of bonding in AIN make it a model system for this charge defect picture, and thus explains the extremely large extent of the band-tail states in this material.
Real-Time Investigation of Solid and Liquid State Reactions In Au-Sn/Cu System
Authors: Oh Seyong , Khandros Igor Y. , Poetzinger Janet L.
Published: March 2011

A real-time x-ray analysis technique has been developed and employed for in-situ investigation of solid and liquid state reactions in Au-Sn/Cu system as a function of temperature. Typically, 1 μm eutectic Au-Sn films were deposited on 1.5 μm Cu layers on Si wafers. Phase changes in Au-Sn films on Cu from ambient to above the eutectic temperature have been investigated. Cu diffusion into Au-Sn film above 250 °C resulted in a ternary Au-Sn-Cu compound and raised the melting temperature of the structure to about 325 °C. This affects joining characteristics of the Au-Sn metallization.
Polyimide-Ceramic Substrate for Supercomputer Packaging
Authors: Kimbara K. , Dohya A. , Watari T.
Published: March 2011

This paper introduces the Polylmide-Ceramic substrate for NEC SX Supercomputers. In case of high performance system such as supercomputers and top end machines in general purpose computer, sophisticated packaging technologies are essential to achieve fastest operations as well as to use highestspeed, highly integrated LSIs.

Wiring substrate which mounts and interconnects LSIs is the key to back up LSI's higher logical-operations.

The high speed interconnection wirings and high density LSI mounting are requested for substrate.

The Polyimide-Ceramic substrate had been developed to meet these demands and have many features of high density thin film wiring, high power supply, high thermal conductivity and huge number of I/Os, in addition to high speed wiring.

25μm wide 75μm center-to-center spacing, two signal layers, 6ns/m signal transmissions, 2.5W/cm2 high power density, 2177 I/Os on a 100mm square substrate have been achieved by using this super substrate technology.

The packaging hierarchy, the first level packaging of TAB LSI, the second level of multi-chip packaging by using Polyimide-Ceramic substrate and liquid cooling module, and the third level of board assemblies are introduced.
Microstructure and Kinetics of the Interface Reaction Between Titanium Thin Films and (112) Sapphire Substrates
Authors: Selverian J.H. , Ohuchi F.S. , Notis M.R.
Published: March 2011

We studied the reactivity of titanium with the R-plane (112) surface of sapphire by transmission electron microscopy (TEM), x-ray diffraction (XRD), and Rutherford backscattering (RBS) techniques. Cross-section TEM specimens were prepared from 200–400 nm thick titanium films deposited on sapphire at 25, 525, 554, 562, 580, 630, and 663°C to observe the interfacial region. In samples deposited at 25°C, without further annealing, no reaction zone could be seen in the TEM. In all other samples titanium reduced the sapphire to form Ti0 6 7[O0 3 3] and Ti3Al[O], Ti and Ti3Al with oxygen in solid solution. An activation energy of 24.7 ± 6 kcal/deg-mole was determined for the growth of the Ti3Al[O] layer. Layer thickness measurements from the TEM and RBS studies were within 10–20% of one another.
In-Plane Residual Stresses in Filament-Evaporated Aluminum Films on Single Crystal Silicon Wafers
Authors: Park Hai-Woong , Danyluk Steven
Published: March 2011

The in-plane residual stresses of single crystal silicon wafers that were coated with filament-evaporated aluminum films have been obtained from measurements of strains produced by shadow Moir interferometry. The aluminum films were deposited as thin film layers over a 8.9cm diameter area on (100) p-type, 10.16cm diameter, 0.05cm thick single crystal silicon wafers, and the stresses were determined by an analysis that accounts for the finite dimensions of the samples. The aluminum film thicknesses varied from 70 to 78Onm. The aluminum films increased the inplane stresses of the wafers by 3 to 15MPa depending on the film thickness.
Glass-Ceramics for Electronic Packaging
Authors: Macdowell J. F. , Beall G. H.
Published: March 2011

Glass-ceramics appear to constitute a new generation in fine ceramic materials for microelectronic packaging. The distinction between glass-ceramics derived via internal nucleation and crystallization of bulk glass and those formed by sintering and surface devitrification of glass particulates is discussed.
Material Development Challenges in High Density Pakaging of Advanced VLSI Memory Devices
Authors: Prough Steven D. , Pope D. Elaine
Published: March 2011

Advances in semiconductor memory storage technology are making possible the development of high density memory cards for hand held and portable product applications. This in turn is driving development of ever denser, ultra-thin component packages. Both materials and package design must be more robust in order for next generation packages to withstand surface mount reflow soldering stresses. Trade-offs among ercapsulant properties may be possible in view of new interconnect, die surface protection and leadframe design technologies which are being adopted for high density packaging. Materials and packaging engineers are challenged to capitalize on opportunities offered by these changes in order to optimize strength and moisture resistarnce in developing encapsulating materials for the new generation of packages.
Photonic Integrated Circuits
Authors: Koch T. L. , Koren U.
Published: March 2011

Recent progress in InP-based photonic integrated circuits (PIC's) is reviewed, with an emphasis on the new level of design complexity and fabrication flexibility afforded by advances in metal-organic-vapor-phase-epitaxy(MOVPE) growth techniques.
Optical Interconnect Switch
Authors: Prucnal Paul R. , Perrier Philippe A.
Published: March 2011

A novel photonic interconnect architecture is proposed which can provide extremely high dimensionality. The proposed architecture, which resembles a collapsed network, avoids the difficulties associated with the use of optical crosspoints. This is accomplished by providing a dedicated path for all input- and output-port connections on a common transmission medium. This eliminates the restrictions imposed by 2×2 switching elements in classical space-division switching architectures.
Thick Film Metallization of Aluminum Nitride
Authors: Norton M. Grant , Steele Brian C. H.
Published: March 2011

A widely used technique to metallize substrates for electronic packaging applications is thick film technology. The interaction between commercial thick film materials and aluminum nitride (AlN) has been undertaken and an in depth investigation of the glass/ceramic reactions which occur in frit bonded films. The experimental results have been correlated with thermodynamic predictions of the reaction processes. The standard glasses were found to react with the substrate causing blistering, foaming or dewetting. Following from these studies a model glass system was developed and reactions of this glass with AlN have been investigated using scanning electron microscopical techniques and hot stage microscopy. Thick film inks have been developed using this glass system which are compatible with AlN substrates.
Reactivity of Fly Ash At High pH
Authors: Pietersen Hans S. , Fraay Alex L. A. , Bijen Jan M.
Published: March 2011

The reactivity of fly ash in cementituous systems has been an object of many studies, and is only understood in broad terms. It is generally agreed that the particle size distribution of fly ash correlates with strength development. It has also been demonstrated that temperature and pH development of the blended cement paste have an effect on fly ash reactivity. It is however not clear whether ash chemistry and/or ash glass structure have an influence on its reactivity, as is the case with some blast furnace slag cements. In order to discriminate between the many variables controlling fly ash reactivity, the dissolution kinetics of class-F fly ash have been studied. The fly ash was first separated into equal size and density fractions. These were reacted with NaOH, with a pH ranging from 13.0 to 13.7 and temperatures between 20 and 40°C. If the results of the dissolution experiments are corrected for differences in glass content and particle size, the effects of temperature and pH seem to be of more importance than differences in ash chemistry. The dissolution proceeded virtually congruent. TEM micrographs of some of the ash fractions indicate that a wide variety of glasses may be encountered in fly ashes; most glasses show evidence of phase separation. The results are discussed with respect to glass structure and glass dissolution-theory.
Agglomeration of High Calcium Fly Ash for Utilization I. Physical Properties
Authors: Bergeson Kenneth L. , Kilgour Carol L , Overmohle Douglas
Published: March 2011

Inability of the Iowa fly ash industry to meet their demands for fly ash during the peak construction months led the Iowa Fly Ash Affiliates to initiate research into storage alternatives for high-calcium fly ashes. Conventional, closed storage facilities are extremely expensive and currently not cost effective. In addition, the industry is faced with the rising costs of landfill disposal. This paper presents the results of utilizing the rapid self-cementitious properties of high-calcium ashes to agglomerate them into discrete, aggregate size particles for stockpiling. The two fly ashes used in this study contained 25 to 30 percent calcium. Water was used as an agglomerating medium. Agglomeration was accomplished using three types of commercial equipment as follows: continuous rotary pan agglomerator, continuous auger agglomerator and a batch turbine agglomerator. All units produced relatively well graded aggregate material differing primarily in particle shape and texture. Research work discussed includes gradation, strength, and durability of the agglomerates. Agglomerates were also reground using a newlydeveloped, energy efficient, micronizing technique. Research results using the reground ash in concrete and soil stabilization are presented.
Agglomeration of High Calcium Fly Ash for Utilization II. Binding Mechanisms
Authors: Kilgour Carol L. , Bergeson Kenneth L , Schlorholtz Scott
Published: March 2011

Fly ashes from the Lansing and Ottumwa power plants in Iowa were agglomerated by means of a continuous pan agglomerator, a continuous auger and a batch turbine agglomerator. In order to compare agglomeration mechanisms the following parameters were determined: (a) particle size distributions of the untreated fly ashes; (b) particle size distributions of the agglomerated fly ashes; (c) pore size distribution of agglomerates; (d) crystalline hydration products by X-ray diffraction; and (e) morphological characterization by scanning electron microscopy.

In the batch system coalescence mechanisms were favoured. The agglomerates were fairly irregular in shape and had a rough surface texture. As residence time in the system increased breakage of agglomerates occurred, reducing the average agglomerate size. In the continuous systems layering of the fine feed particles onto established agglomerates was the predominant growth mechanism. The agglomerates were smooth and spherical. The layer structure was observed by scanning electron microscopy. Agglomerates of widely varying size, strength, and pore matrix can be produced in both systems. It is envisaged that while agglomerates could be produced with characteristics essential for their proposed end use by either method, continuous pan agglomeration would be the most versatile system to utilize.
Resistance of Fly Ash Mortars to Sulphate Attack in a Controlled Environment
Authors: Day Robert L. , Konecny Jana
Published: March 2011

Sulphate-expansion tests were performed on mortar bars manufactured with two types of subbituminous fly ash and two types of cement. One fly ash was from Alberta, Canada while the second, a high-calcium ash, was from the United States. Ordinary and sulphate-resistant cements were used in the examination.

Bars were exposed to attack when they reached a given strength level. Some bars were soaked in a mixed solution of sodium and magnesium sulphate under controlled conditions; the pH of each solution was maintained at either 7 or 9.5 by regular additions of sulphuric acid. For other bars the pH of the solution was not controlled. Behaviour of bars in water baths where pH was maintained approximately constant was also examined. Bars were soaked in individual three-bar groups so that possible correlation between amount of acid added and linear bar expansion with time could be observed. Post-expansion examinations included strength degradation, qualitative X-ray analysis and thermal analysis.

Results show some interesting correlations, or lack therof, between acid addition and sulphate attack. Mortars made with the Alberta ash performed better than the corresponding control mortars; however, in a mixed magnesium/sodium solution expansions were much greater than in previous tests where only sodium sulphate was used. Bars made with the high-calcium subbituminous ash performed very poorly under all conditions.
The Use of Transition Metal Oxides in Microwave Sintering of Coal Ash-Derived Bricks and Tiles
Authors: Bescher Eric P. , Kao Yu-Hua , Li C. Y. , Mackenzie John D.
Published: March 2011

The generation of undesirable ashes from municipal and hazardous waste incineration, and from coal-fired power plants has become a serious environmental problem. Ash contains heavy metals and/or unburned organics, and the disposal of this material is drawing increased concern from the public and government agencies. Since the leaching of a toxic constituent from a powder is proportional to the surface area of the powder, any method of consolidation is welcome. The interest of such a consolidation process would be greatly increased if, in addition to making this material safe, a commercially useful material could be produced. Conventional methods of heating such as oil-fired furnaces require large flows of air. They are also time and energy consuming because it is relatively difficult to heat up a powder. Microwave processing creates rapid heating and allows for the attainment of uniformly high temperatures; therefor, it is a viable alternative. However, most ashes will not easily absorb microwaves if they do not contain a phase that couples with the microwaves. Transition metal oxides are lossy materials when submitted to microwave radiation. If they are mixed into ashes in a sufficient amount, they will generate heat, cause sintering and reduce the surface area of the powder. In the present work, coal ash-derived bricks and tiles were successfully obtained. Details of processing, mechanical properties and chemical durability of these consolidated ceramics are presented
Use of a Database of Chemical, Mineralogical and Physical Properties of North American Fly Ash to Study the Nature of Fly Ashand Its Utilization as a Mineral Admixture in Concrete
Authors: Mccarthy G. J. , SOLEM J. K. , Manz O. E. , Hassett D. J.
Published: March 2011

A database of chemical, mineralogical and physical characteristics of North American fly ashes has been assembled by the Western Fly Ash Research, Development and Data Center. One-hundred and seventy-eight representative ashes were divided into three groups according to their analytical CaO content: low-calcium, <10%; intermediate-calcium, 10–20%; high-calcium, 20+%. Statistical analyses were performed within each of the three groups. Thirty-two plots relating chemical composition, mineralogy and physical test results are presented. Extensive discussions relating the chemistry and mineralogy of the ash to the source coal, the distribution of the chemical constituents among crystalline and glassy phases, and the reactions of these phases in concrete are given. The consistency of high-calcium fly ash generated at a Midwestern U.S. power station fired with Wyoming bituminous coal was studied using ninety-three ashes collected over a two year period. The availability of mineralogy for each ash leads to a more thorough understanding of the bulk chemical and physical test results used in evaluating fly ashes for utilization, and in modeling their behavior after disposal
Thermal Properties of Coal Ashes
Authors: Ledesma Ramona , Isaacs L. L.
Published: March 2011

The applicability of differential thermal analysis to determine the fusibility behavior of coal ashes was investigated. The technique proved useful to obtain four specific temperature points. These are: the minimum sintering temperature, the softening point, the point of complete fluidity and the reaction temperature which is tentatively identified as the eutectic temperature. In addition, differential scanning calorimetry was used to determine the heat capacity of the ash powders between 100K and 850K. Ash heat capacities were correlated with ash constitution
New Rapid Setting Alkali Activated Cement Compositions
Authors: Roy D. M. , Silsbee M. R. , Wolfe-Confer D.
Published: March 2011

The advantage of utilizing blended cements for many applications has been well documented. However, the use of these materials has been limited by the longer setting times associated with the use of these materials. This report discusses the development of formulations employing alkali activation to shorten the setting times. The results of characterization of these materials using calorimetry, microscopic, x-ray diffraction, and mechanical property techniques are discussed.
Calcium Phosphate Dental Cements
Authors: Xie Like , Monroe E. A.
Published: March 2011

Cement systems composed of tetracalcium phosphate powder or powder mixtures of tetracalcium phosphate and brushite were investigated. The liquid components for making the cements include aqueous solutions of H3PO4, Ca(OH)2, or Na2SiO3. For the tetracalcium phosphate cement, strong acidic or basic solutions must be used in order to achieve a short setting time.

Our results show that the tetracalcium phosphate and brushite cement can set in a short time under suitable conditions. Humidity, particle size, and pH of liquid have a strong influence on cement setting. Solutions of Ca(OH)2 or Na2SiO3 can be used for making high pH cements and a solution of H3PO4 for a low pH setting cement. To reduce the setting time of cement, the key is to control the hydrolysis of tetracalcium phosphate. The results of hydrolysis indicate that, at 37°C, the single-phase tetracalcium phosphate can only be converted to hydroxyapatite when hydrolyzed in solutions with an H3PO4 solution concentration of ∼5% or with a high pH solution.

Both the single-phase tetracalcium phosphate cement and the mixture phase cement have good biocompatibility. Appropriate concentrations of the solutions of Na2SiO 3,Ca(OH)2, or H3P04 can be used in the cements from the perspective of both biocompatibility and cement properties.
Morphology and Long Term Behavior of Polymer Cement Concrete
Authors: Grosskurth K. P.
Published: March 2011

Polymer-modified cement concrete represents a heterogeneous material whose properties are influenced more by the properties of the polymers than by the properties of the cement component. Typical of polymeric materials are their temperature dependent behavior. This temperature dependence can be related to the glass transition temperature of the polymer. In cases where the temperature is higher than the glass transition temperature, strength decreases while deformability simultaneously increases. Polymeric films are formed in the dispersed polymer systems as a result of reactions occurring at the glass transition temperature. A styrene/acrylic modified concrete was studied at different polymer loadings. The tensile and compressive strengths of this system were studied as a function of temperature. Increasing deformability temperatures principally at higher polymer loadings near the glass transition temperature and decreasing strength occurred.
Investigations on Na-Silicate Based Binders
Authors: Odler Ivan , Hennicke U.
Published: March 2011

Water glass Na2O-SiO2 reacts in water solutions with Na2SiF6, yielding an amorphous SiO2 and NaF. This reaction, that is completed within a few days, causes setting and hardening of the system. Mortars made with this binder using appropriate fillers sustain temperatures of up to 900°C. At temperatures above 500°C, the hardened material converts gradually to tridymite quartz and sodium disilicate. Above 900°C, a sodium fluosilicate glass melt starts to be formed.
Investigations on Phosphate Cements Hardening at Room Temperature
Authors: Zurz Alfred , Odler I. , Dettki B.
Published: March 2011

Pastes prepared from diammonium orthophosphate and calcined magnesia, MgO, exhibit a fast setting and hardening associated with NH3 liberation. Struvite, MgNH4PO4.6H2O, was found to be the main reaction product. Pastes made with NaH2PO4 or Na-polyphosphate exhibit a similar hardening reaction. The hardening reaction may be retarded and the ultimate strength moderately increased by adding appropriate retarders, such as Na2B4O7 10H2O to the system. The quality of the used MgO and its fineness has a significant effect on the rate of the hardening reaction.
Physico-Mechanical Properties of Hardened Mg-Phosphate Cement
Authors: Petri Marek , Odler Ivan
Published: March 2011

In a series of test specimens made out of magnesium phosphate cement, their physico-mechanical properties–i.e., fracture toughness, Poisson's ratio, Young's modulus, and bending strength–were studied. Samples included in the study were either in their original moisture state or dried. Some of them were polished on their tension side to eliminate the effect of surface defects.
The Influence of Ion Implantation on The Near-Surface Mechanical Properties of Ceramics
Authors: McHargue C. J. , O'Hern M. E. , Joslin D. L.
Published: March 2011

Ion implantation of ceramics such as Al2O3 and SiC may produce a highly damaged but crystalline surface layer or an amorphous surface. The specific structure depends upon the implantation parameters. Studies using microindentation techniques show that a crystalline implanted surface has a higher hardness (by 10 to 50%) than the corresponding unimplanted crystal but the elastic modulus is essentially unchanged. The hardness and elastic modulus of amorphous implanted surfaces are less than those of the crystalline material. Estimates of the residual stress have been obtained from microindentation tests.
Mechanical Properties of Coatings and Interfaces
Authors: Fabes B. D. , Oliver W. C.
Published: March 2011

Silica Coatings of various thicknesses. hardnesses. and interface integrities were deposited on sapphire substrates using sol-gel techniques. The mechanical properties of the coatings were examined using a mechanical properties microprobe. The observed changes in hardness with indentation depth are explained on the basis of a model of the indentation sequence. in which three separate stages of the indentation process are described. In the first stage. the properties of the coating alone are probed: in the second stage. as the plastic field associated with the indenter extends beyond the coating into the substrate, the properties of the substrate begin to appear: and in the third stage. where the indenter penetrates into the substrate, the composite hardness is dominated by that of the substrate, although the properties of the coating are still apparent.
Determination of Elastic Constants and Viscosity of Amorphous Thin Films From Substrate Curvature
Authors: Witvrouw Ann , Spaepen Frans
Published: March 2011

Substrate curvature measurements were used to monitor viscous flow in Pd79Si21 films at temperatures between 100 and 250°C. To determine the viscosity and the change in viscosity the elastic constants of the film were measured by depositing films on pre-bent substrates: E = 10 ± 1 1010 Pa and ν = 0.43 ± 0.04 The activation enthalpy for η is 13 ± 1 kJ/mole.
Finite Element Calculations of Thermal Stresses in Passivated and Unpassivated Lines Bonded to Substrates
Authors: Sautera Anne I. , Nix W. D.
Published: March 2011

Thermal stresses in passivated and unpassivated aluminum lines bonded to substrates have been calculated using the MARC finite element code. Stresses in the unpassivated lines increase with increasing line width, with increasing substrate rigidity, and with decreasing distance from the substrate. Edge effects become significant for small line widths. Stresses in passivated lines increase with decreasing aspect ratio, with increasing passivation thickness, and with increasing Young's modulus of the passivation. Allowing plastic deformation to occur in the lines homogenizes and reduces the stresses. The calculated stresses in passivated lines are compared to recent measurements of stresses in encapsulated aluminum lines. The measured values are about a factor of four smaller than the calculated stresses, indicating that some deformation process besides plasticity, such as voiding or cracking, must have occurred to relieve the stresses.
X-Ray Stress Studies of Passivated and Unpassivated Narrow Aluminum Metallizations
Authors: Paszkiet C. A. , Korhonen M. A. , Li Che-Yu
Published: March 2011

Stresses in thin narrow textured metal lines were measured using x-ray diffraction techniques. Arrays of 1.5μm wide, 0.32μm thick aluminum lines, both with and without a 0.32μm thick SiNx passivation layer, were heat-treated at 400°C in a hydrogen/nitrogen atmosphere. After heat treatment the lines were examined periodically using chromium radiation to monitor the relaxation of the stress developed during heat treatment. The apparent stress in both the passivated and unpassivated lines relaxed significantly over the measurement period of three days. The higher stresses present in the passivated lines may be partially responsible for the voids which were found after aging at room temperature.
Indentation Load Relaxation Experiments on Al-Si Metallizations
Authors: LaFontaine W. R. , Yost B. , Black R. D. , Li Che-Yu
Published: March 2011

Indentation load relaxation (ILR) experiments with indentation depths in the submicron range are described. The observed flow behavior of a 1μm thick A1-2%Si film deposited on a silicon substrate depended on the depth of penetration. For shallow penetration depths, the shape of the flow curves obtained from this sample are similar to those obtained from a conventional load relaxation test of a bulk specimen. For penetration depths close to the film/substrate interface, the influence of the substrate on the film's deformation behavior was observed.
Creep Behavior of Spuitered TiN Films Using Indentation Testing
Authors: Raman V. , Berriche R.
Published: March 2011

Tin films were deposited on silicon substrates by RF diode sputtering and the growth behavior of these films were characterized by scanning electron microscopy. The time dependent plastic flow behavior in these films were examined by performing indentation tests using a dcpth-scnsing hardness testing machine. Individual indentation experiments with different constant load segments were conducted and the creep characteristics of both sputtered films and bulk Sn were examined. The stress exponents determined from these tests were compared with those determined for bulk Sn from conventional creep tests. The influence of the substrate material on the creep properties of the film are described.
Studying Mechanical Properties Of Thin Films Under High Pressures
Authors: Cai B. C. , Kuhlmann-Wilsdorf D. , Nelson R. B.
Published: March 2011

Work-hardening curves of aluminum foils and of stacks of O.1μm thick 22 ct. gold foils, deformed between rotating Bridgman anvils, have been obtained for pressures up to 1533 MPa and shear strains to 400,000%. No sample thickness effect has been found between 5μm and 3μm, nor any significant difference between homogeneous foils and multi-layer foils, but heat-treatments do affect the results, as apparently does the introduction of 50nm thick sputtered copper layers between stacks of gold foils. Increases of strength with pressure appear to be due to corresponding increases of the Peierls-Nabarro stress. X-ray evidence indicates the reorientation of the foils from an initial (001) recrystallization texture after rolling to the (111) texture that was to be expected. Ordinary deformation behavior is indicated throughout, except for a tendency for slight negative work-hardening in the lower pressure range. At the extreme, assuming homogeneous deformation, the foils thinned to 60nm.
Microscratch Test for Ultra-Thin Films
Authors: Wu T. W.
Published: March 2011

In a microscratch test performed by using an upgraded microindenter, the normal load, tangential load, scratch length and acoustic emission, are monitored simultaneously during an entire scratch process for the purposes of measuring the critical load and studying the ffilure mechanisms of the deposited films. The adhesion strength, scratch hardness, fracture toughness and friction are the mechanical properties which are possible to obtain by using this technique. Results from aluminum, carbon and zirconia coatings will be discussed.
Nanotribology of Diamond Films Studied by Atomic Force Microscopy
Authors: Neubauer Gabi , Cohen Sidney R. , Mcclelland Gary M. , Seki Hajime
Published: March 2011

An atomic force microscope, operated in ultra-high vacuum has been employed to study the tribological properties of diamond films under small loads (< 10−6 N) on a nanometer scale. The incidence of intermittent motion, “stick-slip”, while sliding a diamond tip across the diamond film, is detected under certain experimental conditions and is discussed with respect to the difference between static and kinetic friction, sample topography and a varying sample condition.
Diamond-Like Films as Optical and Protective Coatings
Authors: Gupta D. Das , Demichelis F. , Spagnolo R. , Tagliaferro A.
Published: March 2011

Films of amorphous carbon (a-C) and hydrogenated amorphous carbon (a-C:H) are deposited by R.F. Magnetron Sputtering and Sputter Assisted Plasma CVD respectively and their properties are compared. It is found that high optical gap, high resistivity a-C can be obtained, so indicating a large amount of sp 3 bonded C atoms. For this reason attention was mainly focused on a-C and possible application were considered.
Measurement of Interface Strength by Laser Pulse induced Spallation
Authors: Gupta V. , Argon A. S.
Published: March 2011

The strength of planar interfaces between a substrate and a thin coating (1–2 µm) can be measured quite effectively by a laser spallation technique. In this technique a laser pulse of a high energy and a predetermined length is converted into a pressure pulse of a critical amplitude and width that is sent through the substrate toward the free surface with the coating. The compressive pressure pulse is reflected into a tension pulse from the free surface of the coating and loads the coating/substrate interface in tension. The laser flux is tuned to a threshold level at which the interface comes apart. The critical stress amplitude that accomplishes the removal of the coating is determined from a computer simulation process. The simulation itself is verified by means of a piezoelectric crystal probe which is capable of mapping out the profile of the stress pulse generated by the laser pulse.
Compressive Stresses, Buckling and Spalling of Tungsten LPD Films
Authors: Borer Aidan , Derby Brian
Published: March 2011

Very large compressive stresses have been measured in thin LPD tungsten films. These stresses are responsible for the extensive buckling of the films. Buckling occurs over a wide range of radii and is accompanied by random spalling over the same range. The large compressive stresses are thought to be oxidation induced. The pattern of random buckle spalling does not fit the specific spalling criteria proposed by other workers. These criteria are examined and a further explanation for the spalling behaviour of these films proposed
Cracking and Delamination of Vapour-Deposited Tantalum Films
Authors: Fisher R. M. , Duan J. Z. , Liu J. B.
Published: March 2011

Tantalum films begin to crack and spall during vapour deposition on glass at a thickness of 180 nm. Islands and ribbons, 10 – 30 µm in size, delaminate by crack growth along the Ta/glass interface for several gIm after which the crack penetrates into the glass to a depth of 0.5–1 µm and complete spalling occurs. X-ray diffraction showed that about 50 % of the original bct, β-tantalum, phase had transformed to the bcc α-Ta phase. When Ta was deposited on glass that was first covered with 52 nm of copper, spalling was observed to begin at a thickness of 105 nm. In this case, the film first cracks and then peels along the Cu/glass interface and curls into scrolls indicating the presence of a small stress gradient. X-ray diffraction of the asdeposited film, and electron diffraction of ion-milled flakes, showed that Ta films deposited on Cu-coated glass almost completely transform to bcc α-Ta. The critical thickness for delamination along the Cu/glass interface is about 1/2 that for cracking in the glass substrate when an intermediate layer of Cu is not present. All of the above findings are in good agreement with previous observations on Cr films.
Indentation Fracture of Brittle Materials
Authors: Lucas Barry N. , Oliver W. C. , Wert J. J.
Published: March 2011

The response of four transparent materials, soda-lime glass, fused silica, single crystal (0001) A12O3, and Y2O3-ZrO2, to contact by a sharp indenter has been studied. Insitu observation and continuous monitoring of the load and displacement throughout the test allowed the indentation fracture sequence of the transparent materials to be characterized and also permitted the effects of these fracture events on the corresponding load displacement curves to be noted. It was found that if the cracks produced during indentation grew discontinuously, they manifested themselves in discontinuities in displacement on the corresponding load-displacement curve.
Properties of a Submicron-Honeycomb thin film
Authors: Furneaux R. C. , Crompton J. S. , Fitchett D. J.
Published: March 2011

A method has been developed of separating the porous film produced by anodizing aluminium from its substrate. Such films have a honeycomb morphology with pores that open at both surfaces. They are composed of essentially anhydrous alumina doped with acid anion from the anodizing electrolyte, and are electron diffraction insensitive. A geometrical model has been developed that describes how the pore morphology is determined by the anodizing voltage. Using this model, expressions are derived that relate cell dimensions to voltage-determined parameters and bulk properties such as porosity.

The flexural modulus and tensile strength of honeycombs have been modelled by considering bending moments experienced by the cell walls. Thus, the properties were expressed in terms of cell dimensions. Here, the anodic film and honeycomb models are combined. These are used to analyze the mechanical properties of the films as determined by the anodizing parameters. A critical crack size is predicted and compared with the results of microstructural examinations. Good agreement is shown. Assumptions behind these findings and the implications arising are discussed.
Mechanical Properties of Multilayered Copper-Nickel thin films Measured by Indentation Techniques
Authors: Schlesinger T. E. , Cammarata R. C. , Kim C. , Qadri S. B. , Edelstein A. S.
Published: March 2011

Artificially multilayered copper/nickel thin films with bilayer repeat lengths between 1.6 and 12 nm were produced by ion beam sputtering. The mechanical properties of these films were investigated by low load microhardness and nanoindentation (force versus depth) techniques. It was found that none of the films displayed bilayer repeat length dependent enhanced elastic behavior (the supermodulus effect) as measured during unloading in the nanoindenter. However, enhancements in hardness, as measured by both the nanoindenter and the low load microhardness tester, were observed in films with small bilayer repeat lengths. These measurements displayed a Hall-Petch-type relationship, using the individual layer thickness (equal to half the bilayer repeat length) as the characteristic “grain size.” This hardness behavior can be understood in terms of a mechanism involving dislocation pinning at the interfaces analogous to the mechanism of grain boundary hardening.
Structural Dependence of the Elastic Constants of Polymeric Langmuir-Blodgett Films Studied Using Brillouin Scattering
Authors: Lee Sukmock , Dutcher J. R. , Hillebrands B. , Stegeman G. I. , Knoll W. , Duda G. , Wegner G. , Nizzoli F.
Published: March 2011

We have used Brillouin scattering to study the dependence of the elastic constants of uniaxial polymeric Langmuir-Blodgett thin films on the thickness of the polymeric molecule monolayers. With increasing monolayer thickness, an overall decrease in the elastic constants and an increase in the refractive index n33 was observed.
In Situ Stress Measurements During the Formation of TiSi2 C49 On Si Wafers
Authors: Jongste J. F. , Janssen G. C. A. M. , Radelaar S.
Published: March 2011

In the microelectronics industry titanium disilicide (TiSi2) is used as a material for metallization and interconnection on silicon based integrated circuits. In the C54 structure (face centred orthorhombic) TiSi2 has important properties for application in electronic devices: low resistivity (16 μΩ cm), stability up to 900°C and compatibility with silicon processing. In thin films this phase is formed above approx. 700°C. However before this phase is formed, a metastable TiSi2 phase with the C49 (or ZrSi2) structure [1] is already formed at lower temperature. This C49 phase is unfavourable as metallization in IC applications because of the high resistivity (60–300 μΩ cm). From a technological point of view however it is important to realize that during the C49 formation the thin film is subject to a large change of the intrinsic stress. The occurrence of this stress can cause problems during semiconductor device fabrication. Gate oxides in MOSFETs (and other IC microstructures) may be deteriorated by stress. Also focussing problems in lithographic steps can arise because of wafer warpage. In this paper we present in situ stress measurements of the formation of TiSi2 C49 from Ti-Si multilayers. From these measurements the kinetics of the formation process is analyzed.
The Mutual Influence of Magnetic and Chemical Ordering
Authors: Inden Gerhard
Published: March 2011

It can be concluded from experiments that atomic (also called “chemical”) and magnetic ordering reactions exert a mutual influence on each other. In bcc Fe-Al alloys a strong depression of the Curie temperature is observed with the onset of atomic long range order (lro) as compared to the extrapolation of Tcfrom the random alloys, see Fig. 1. In fcc Co-Pt alloys a depression of the critical temperature of atomic lro L12→A1 is observed in the Co-rich alloys which are ferromagnetic, as compared to the Pt-rich counterparts which are paramagnetic, see Fig. 2. In this instance it should be noticed that this assymetry is not observed in Ni-Pt allovs where the Curie temperature is inferior to the critical temperatures of atomic lro [1].
Relationships Between Phase Diagrams, The To, and Tn Temperatures, Cooling Rates and Glass Forming Ability
Authors: Massalski T. B. , Woychik C. G. , Murray J. L.
Published: March 2011

The notion that it should be possible to assess the glass forming ability (GFA) of a given alloy, or alloy system, is a well established concept. If crystallization in the liquid on cooling can be prevented relatively easily, making it possible for a liquid alloy to be cooled through the glass transition temperature (Tg), while employing only a relatively slow cooling rate, the GFA is said to be large. A numerical measure of GFA is frequently expressed in terms of the reduced glass temperature ratio Trg=Tg/Tl, where Tl is the equilibrium liquidus temperature [1]. While the role of Tg in this ratio is clear, the role of Tl is less obvious. Tl can be derived from the features of the phase diagram, but attempts have also been made to calculate Tl from the heats of fusion and the melting points of the constituents involved in a given alloy [2]. At the same time, however, it must be recognized that in a crystallization process under rapid cooling conditions both the temperature of solidification and the composition and structure of the crystalline phase, or phases, which compete with glass formation, are likely to be highly nonequilibrium. Even if a suitable adjustment of the Tl value is made to allow for these features, the Tl fails to take into account the kinetic aspects involved in the glass forming process. Yet these aspects undoubtedly also influence the GFA.
Thermodynamic Factors in the Extension of Solid Solubility in Al-Based Alloys
Authors: Murray Joanne L.
Published: March 2011

Stable and metastable equilibrium diagrams and To curves are calculated for the Al-based binary systems Al-Ga, Al-Ge, Al-Fe, Al-Mg, and Al-Si. Extended solid solubilities and metastable phases have been produced by rapid solidification for each of these systems, and the calculations are compared to experimental observations.
Thermal Cycling and Amorphous-Cyrstalline Transition in the Amorphous C60-Zr40 Alloy System
Authors: Otooni M. A.
Published: March 2011

The transition behavior of the amorphous Cu60Zr40 alloy system during its transition to crystallinity by thermal cycling has been studied. A Differential Scanning Calorimeter (Perkin-Elmer model DSC-2) was used to record, in situ, the onset of thermal evolution of the sample during the course of transition. Analysis of DSC tracings reveal that: a. Transition occurs at a lower temperature than those transformed without thermal cycling, b. The amplitude of the exothermic rise decreases proportionally with increasing numbers of the thermal cycles and c. Details of the profile of the DSC tracing, i.e., the width of the exothermic rise and the presence of the secondary exotherm, are quite different from those transformed without thermal cycling. Preliminary high resolution electron microscopy of thermally cycled samples indicate random distribution of copper-rich precipitates at the early stages of cycling and their coalescence during the final stage of crystallization. For large number of cycles, however, the induced strains from thermal cycles contributes to the image contrast of the quenched solid thus allowing the assessment of the proposed atomic level stresses and strains, via technique of high resolution electron microscopy.
Phase Transitions and Order Parameters
Authors: White Robert M.
Published: March 2011

The usefulness of the concept of an order parameter in describing phase transitions is discussed. Examples of order parameters are given in the context of broken symmetries, and defects in the order parameters are classified in terms of these symmetries.
The Au–Pb Phase Diagram
Authors: Evans Dain S , Prince Alan
Published: March 2011

The Au–Pb system has been redetermined using dta, metallography and X-ray techniques. The compounds Au2 Pb, AuPb2 and AuPb3 are generated by peritectic reactions at 434° , 253° and 221.5°C respectively. AuPb3 and Pb form a eutectic at 84.8 at% Pb and 212°C. It is confirmed that Au2 Pb is stable down to at least 200°C.
Relative Solubility Trends in Transition-Metal Alloys
Authors: Goodman D. A. , Bennett L. H. , Watson R. E.
Published: March 2011

The prediction of terminal solubilities for a given metal solute and solvent is a formidable problem, and it remains a major unsolved question in metallurgy. In this paper we describe the relative solubilities of the transition metals in one another. After discussing the problem of defining an appropriate measure of solubility for the transition-metal alloys which have any intermediate phases, we present a map of relative solubilities for the transition metals. From this map, we delineate the trend which occurs. Both the Engel-Brewer theory and d-band transition-metal alloy theory are consistent with this trend.
The Atom as the Building Block in Crystal: The Use of Electron Charge-Density Data Base for Calculating Structural Properties of Metals
Authors: Krasko Genrich L.
Published: March 2011

We suggest a new method of calculating structural properties of metals. The method utilizes the data base of “firstprinciple” charge-density distributions in pure metals accumulated in recent years. If, for a metal, the solution to the Schrodinger equation within the atomic cell is known, the electron charge-density distribution in an orbitrary point of the crystal may be “reconstructed” within the framework of a model. Using the Density-Functional Formalism and the virial theorem, the total energy of the crystal may be found in terms of an effective interatomic potential. The latter may be used for the calculating of other structural properties, such as phonon spectra and elastic moduli. The extension of this method to alloys is briefly discussed.
Solidification Processing of NbCr2 Alloys
Authors: Thoma D. J. , Perepezko J. H.
Published: March 2011

Microstructural development in alloys bordering the NbCr2 Laves phase composition has been evaluated following solidification processing. With splat quenching of binary alloys, rapid solidification has yielded supersaturation of both Nb-rich and Cr-rich primary solid solutions as well as some solubility extension of the C15 phase during cooling as compared to as-cast structures. Ternary additions of Ti are soluble in NbCr2 along the pseudobinary NbCr2-TiCr2 section for C15 structures and completely miscible in bcc Nb and Cr solutions. In the rapid freezing of splats, modest Ti additions to NbCr2 enhance the development of an extended bcc solution during freezing and the supersaturation of the C15 phase during solid-state cooling. In the solid state, the C14–C15 transformation of the Laves phase is suppressed partially in arc-cast ingots and more completely at high cooling rates. Upon heating, thermal analysis has revealed that the retained C14 phase undergoes a decomposition sequence with at least two stages, possibly involving polytypes and associated faulting, to the stable C15 structure. The microstructural options developed by solidification processing, solid state transformations, and alloying have been observed to modify the brittle behavior of the as-cast structures.
The Effects of Cooling Rate Upon Xdt m TiAl Weld Microstructure
Authors: Robertson Erica , Hill Mary Ann , Schwarz Ricardo B.
Published: March 2011

Fusion zone microstructures of an electron beam (EB) welded XDt m Ti–48at%Al + 6.5 vol% TiB2 alloy revealed plate-like precipitates which were absent in the base metal. The volume fraction of this phase increased with increasing cooling rate and correlated with increased weld cracking frequency. To determine whether this phase was a product of solidification from the melt or a product of a solid-state transformation, the microstructures of the welds were compared to those of samples cycled in a Gleeble 1500/20 Thermal-Mechanical Test System which was programmed to simulate the solid-state portion of the weld cooling rates (as predicted by a Rosenthal analysis). The microstructures were characterized by X-ray diffraction, optical and by scanning electron microscopy. The plate-like phase found in the weld microstructures was identified as TiB2 occurring upon rapid solidification of the melted weld metal.