bluuebunny/crossref_metadata_2025 huggingface dataset:
Micro-Mechanical Modeling of the Pull-Out Behavior of Corrugated Wiredrawn Steel Fibers from Cementitious Matrices.
Authors: Chanvillard Gilles , Aitcin Pierre-Claude
Published: March 2011

The pull-out behavior of non-straight steel fibers cannot always be analyzed solely in terms of bonding. Rather, it is necessary to take into account the mechanical anchorage provided by the fiber geometry.

It is shown in this paper, that in the case of non-straight steel fibers a strong interaction exists between bonding and anchorage. A micro-mechanical model, based on the dissipation of energy during slipping of the fiber is proposed. In this model, bonding is included on the basis of the Coulomb friction law, without reference to a bond-slip law; mechanical anchorage is modelled from plastic deformation of the fiber.

With this model, it is possible to evaluate the significance of some physical parameters such as the water/cement ratio of the matrix, the fiber's geometry and the steel properties. Moreover, this model provides a rational basis for the optimization of the fiber-cementitious matrix interaction from an energy point of view.
Fracture of Sifcon Under Combined Tensile and Shearlike Loading
Authors: Van Mier J. G. M.
Published: March 2011

In a series of preliminary experiments, the shear stiffness degradation and ’shear’ failure mechanisms of pre-cracked Slurry Infiltrated Fiber CONcrete (SIFCON) were studied. The specimens were first subjected to axial tension (in displacement control), whereafter a lateral shear was applied over the crack band. Variables in the investigation were the direction of loading with regard to the main fiber direction, and the axial crack opening before shearing. The degradation of shear stiffness resembles that of normal concrete at low crack openings, but seems governed by fiber action at larger crack openings. At low crack openings, shear failure was observed in the sense of an array of inclined tensile microcracks. At larger crack openings, inclined cracks developed through coalescence of preexisting tensile cracks.
Tensile Testing of Fiber Reinforced Cementitious Composites
Authors: El-Korchi Tahar , Toutanji Houssam , Katz R. Nathan , Leatherman Gary L. , Lucas Harald , Demers Cornelia
Published: March 2011

A novel approach in tensile testing of cementitious composites using the ASCERA® hydraulic tensile tester is described. The test specimens are cylindrical bars. Steel pistons are adhesively bonded on either end of the specimens and inserted in a pressure chamber. The pressure is increased until the specimen is pulled apart by the hydraulic pressure exerted on the pistons.

Advantages of this method are: large volume under load, self-alignment to minimize externally applied bending moments, and determination of the rupture stress exactly at the fracture initiation point.

Glass reinforced cementitious composites were tested. Results are discussed with respect to curing time and fiber volume fraction. The tensile strength values obtained by hydraulic testing are compared to values obtained by traditional uniaxial tensile strength tests. A biaxial model is adopted to verify the results.
Fiber Reinforced Alkali Activated Blended Cement Materials
Authors: Silsbee M. R. , Wolfe-Confer D. , Roy D. M.
Published: March 2011

Recently there has been renewed interest in the use of alkali activation to increase the rate of strength development in blended cements. The objective of this study was to examine the advantages-disadvantages of using alkali activated blended cement materials with fiber reinforcing. There are advantages of the rapid set for certain applications.
Toughening of MDF - OPC Composites
Authors: Park C. K. , Silsbee M. R. , Roy D. M.
Published: March 2011

Macro-Defect-Free (MDF) materials are cement-polymer composites exhibiting high flexural strengths and high toughness (for cement based systems). The incorporation of fibers into MDF composites has been found to offer the possibility of increasing both the ultimate flexural strength and toughness of MDF materials prepared using an ordinary portland cement-polyacrylamide matrix.

This paper examined the effect of fiber type and fine particles as a packing filler on the resulting mechanical properties. The incorporation of non-traditional materials (for MDF) into the MDF matrix is also discussed.
Carbon Fiber Reinforced Cement and Mortar
Authors: Linton J. R. , Berneburg P. L. , Gartner E. M. , Bentur A.
Published: March 2011

Although carbon fibers have high tensile strengths and are chemically inert, their application in cementitious composites is limited due to their brittleness. An image analysis technique employed to determine the length distribution of the reinforcing fibers before and after mixing in cement paste and mortar matrices indicates that substantial fiber breakage occurs during mixing. In paste mixtures, the average fiber length after mixing remains above the critical fiber length, but in mortar mixes the average fiber length falls below the critical fiber length resulting in no significant enhancement of composite flexural properties.
A New Type of a Glass Fiber Screen Reinforced Cementitious Board
Authors: Odler I.
Published: March 2011

A new cementitious board reinforced with resin impregnated glass fiber screens is described. The screen are located at the top and bottom of the board and guarantee a high flexural strength and fracture energy of the material. An adequate longterm performance has been proven in field experiments.
Polypropylene Fibre Reinforced Concrete Air Permeability
Authors: Sanjuan Miguel A. , Moragues A. , Bacle B. , Andrade C.
Published: March 2011

The permeability of concrete to gases is of direct importance to the durability of concrete structures, because of carbon dioxide flowing through the concrete favour lime carbonation and reinforcing steel corrosion.

Mortar with and without polypropylene fibres having water/cementitious ratios of 0.30, 0.35 and 0.40 and a cement/sand ratio of 1/1 were studied. Polypropylene dosage varied from 0.1 to 0.3% by volume of cement.

The characterization of mortar permeability was made using cylindrical shaped samples (3 cm height and 15 cm diameter). These specimens were 28 days cured and then dried before the test.

The addition of fibres results in a decrease of air permeability. Variation of the water/cement ratio is of lesser importance than fiber addition.
Is There a Way to a Perfect Rapid Thermal Processing System?
Authors: Kakoschke R.
Published: March 2011

The temperature within a rapid thermal processing system is characterized by the intensity distributions of the lamp light and of the reabsorbed heat radiation of the wafer. The intensity to the front and back side of the wafer and to the wafer edge have to be considered for pattern induced effects and additional energy loss at the edge, respectively. Monte-Carlo simulations show that the major problems with a multi lamp arrangement with surrounding reflector are due to nonuniform irradiation by the lamps, nonuniform energy loss of the wafer, and additional energy loss at the wafer edge. The temperature influencing quantities cannot be optimized at the same time without modifications of the reflector geometry or without a subsidiary light flux which is controllable independently of the lamp light.
Improvement of Temperature Uniformity in Rapid Thermal Processing Systems Using Multivariable Control
Authors: Norman S. A. , Schaper C. D. , Boyd S. P.
Published: March 2011

During rapid thermal processing (RTP) of a semiconductor wafer, maintenance of nearuniform wafer temperature distribution is necessary. This paper addresses the problem of insuring temperature uniformity in a cylindrical RTP system with multiple concentric circular lamps.

A numerical technique is presented for optimizing steady-state temperature distribution by independently varying the power radiated by each lamp. It is shown for a simulated system, over a wide range of temperature setpoints, that the temperature uniformity achievable with multivariable (“multiple knob”) control of lamp powers is significantly better than that achievable with scalar (“single knob”) control.

The difficulties of using scalar control in RTP are more severe in the case of temperature trajectory design than in the case of steady-state temperature maintenance. For example, with scalar control the rate of temperature increase during ramping is limited because temperature nonuniformity can cause slip defects in the wafer. A numerical technique is presented for designing multivariable lamp power trajectories to obtain near-optimal temperature uniformity while wafer temperature tracks a specified ramp, resulting in slip-free ramp rates much faster than those achievable with scalar control.
Temperature Control and Temperature Uniformity During Rapid Thermal Processing
Authors: Vandenabeele Peter , Maex Karen
Published: March 2011

An overview is given of the major problems in temperature control and uniformity control. For temperature control varying emissivity due to layers, roughness, doping and chamber design are discussed, together with problems due to lamp radiation. The main way to go seems to be in-situ emissivity correction. For uniformity control, the main problems are non-uniform reflector radiation and patteren induced non-uniformity. The solution seems to be the design of a reflective chamber with uniform reflected radiation.
Thermal Effects of Gasses in Rapid Thermal Processing
Authors: Knutson K. L. , Campbell S. A. , Leighton J. D.
Published: March 2011

A numerical model has been created for a Rapid Thermal Processing (RTP) system. Experiments have been done to show the validity of the model. The simulations done examine thermal uniformity and stresses incurred by RTP during steady state operation and during short time temperature ramps. It is shown that increasing the radiant intensity at the edge of the wafer reduces stress, compared to a uniform radiant field, in steadystate operation but increases stress during short time temperature ramps.
Rapid Thermal Chemical Vapor Deposition of Germanium and Germanium/Silicon Alloys on Silicon: New Applications in the Fabrication of MOS Transistors
Authors: Öztürk M. C. , Grider D. T. , Ashburn S. P. , Sanganeria M. , Wortman J. J.
Published: March 2011

In this work, low pressure chemical vapor deposition (LPCVD) of pure Ge and SixGe1-x on Si and SiO2 has been considered for new applications in future ultra large scale integration (ULSI) technologies. Depositions were performed in a lamp heated cold-wall rapid thermal processor (rapid thermal chemical vapor deposition -RTCVD) using thermal decomposition of GeH4 and SiH2Cl2 in a carrier gas of H2. It is shown that RTCVD of Ge on Si is highly selective with no deposition occuring on SiO2. The selectivity of Ge/Si depends on the amount of germane in the gas phase. The processes are relatively low temperature/high throughput processes suitable to single wafer manufacturing. In this paper, we review potential applications of Ge and SixGe1−x in future MOS processes. Specifically, Ge and SixGe1−x have been considered for three new applications: i) fabrication of raised source/drain structures where selective Ge or SixGe1−x is used as a sacrificial layer to eliminate silicon consumption during silicide formation (by forming a germanide), ii) Formation of ultra-shallow junctions in silicon using selectively deposited and implanted polycrystalline SixGe1−x as a diffusion source, iii) Formation of MOS gate structures with SixGe1−x gate electrodes for lower dopant activation temperatures and better threshold control.
Low Temperature Epitaxial Silicon Growth in a Rapid Thermal Processor
Authors: McNeill D. W. , Gamble H. S. , Armstrong B. M.
Published: March 2011

A rapid thermal processor has been used for the study of epitaxial silicon growth. Without the need for UHV conditions, bulk contamination levels of oxygen and carbon have been reduced to 5E17 cm−3, at a growth temperature of 750°C. In-situ cleans have been assessed as substrate preparation techniques. High temperature H cleans can reduce interfacial doses of both oxygen and carbon to below 5E13 cm−2. I-owever, low temperature cleaning, using a remote fluorine-based plasma, has as yet only achieved oxygen and carbon doses of 5E14 cm−2 and 3E15 cm−2 respectively. Minority carrier lifetimes of a few micro seconds and electron carrier concentrations of about 1E15 cm−3 are typical for undoped films grown at 750°C. In-situ doping with phosphine has also been employed. Typical doping levels of 5E19 cm−3 uniformly distributed throughout the layers have been achieved. The phosphorus is electrically active in the as-grown film with typical carrier mobility estimated to be 104 cm2v−1s−1.
Growth of Epitaxial Silicon Carbide on Silicon by Rapid Thermal LPCVD
Authors: Ruddell F.H. , Armstrong B.M. , Gamble H.S.
Published: March 2011

This paper describes the growth of epitaxially aligned SiC on < 111 > and < 100 > silicon substrates at 970°C, using rapid thermal LPCVD. A growth mechanism comprising carbonation of silane adspecies has been deduced.
A New Recrystallization Technique for Large Area Thin Film Silicon on Glass Structure
Authors: Hayama Hiroshi , Mukainari Masahito , Saito Takeshi
Published: March 2011

A new recrystallization technique has been proposed, with which a large area thin film silicon on glass structure is able to be recrystallized. The technique utilizes self-heat-confinement caused by induction eddy currents, analogous to floating zone crystal refining technique. An experimental recrystallization system is shown. A recrystallized silicon layer with some hundred micron grain size was obtained with the system.
Activation of Sb in Ultra-Shallow Poly-Silicon Emitters Using Rapid Thermal Processing.
Authors: Grelsson Ö. , Söderbärg A. , Magnusson U. , Olsson J. , Mohadjeri B.
Published: March 2011

An ultra-shallow poly-silicon emitter formed by different heat treatments including RTA of an evaporated, antimony doped, poly-silicon structure is presented. The fabrication process together with electrical characterizations, resistivity measurements and SIMS analysis are given. Especially, the impact of RTA treatment on the electrical characteristics of these emitter structures is investigated. Also, the IV and Gummel characteristics of a bipolar transistor with this type of poly-silicon emitter is given.
Lateral Uniformity of Ultra-Shallow Junctions Formed by Rapid Thermal Annealing in Polysilicon-on-Silicon Systems
Authors: Batra S. , Park K. , Banerjee S. , Smith T. , Mulvaney B.
Published: March 2011

Lateral non-uniformities can be expected in the dopant diffusion front in the substrate in polysilicon-on-single crystal Si systems upon Rapid Thermal Annealing (RTA), because the grain boundaries in polysilicon act as fast diffusant pipelines and also possibly inject defects into the substrate, which can locally enhance diffusivities in the substrate due to dopant-point defect interactions. The lateral uniformity of As, B and P ultra-shallow junctions formed in the substrate by indiffusion from as-deposited amorphous or polysilicon films has been studied using concentration dependent etching and transmission electron microscopy. Due to a larger final grain size after annealing in the case of as-deposited amorphous Si films compared to asdeposited polysilicon films, there is significant lateral doping inhomogeneities in the diffusion front. However, the doping inhomogeneities are gradually smeared out as the impurities diffuse deeper into the substrate due to lateral as well as vertical diffusion.
In-Situ Temperature Estimation in Rapid Thermal Processing Systems using Extended Kalman Filtering
Authors: Cho Y.M. , Schaper C.D. , Kailath T.
Published: March 2011

An Extended Kalman Filter (EKF) is developed to provide an improved pyrometer-based estimate of temperature in rapid thermal processing systems. Models of the heat transfer characteristics, emissivity variations, and temperature measurement equipment, are used in formulating an EKF as a closed-loop observer to filter out noise, lessen the effects of processing variations, and to infer temperature at locations where no measurements are available. Extensive simulations are conducted to analyze the robustness of the EKF.
Synchrotron X-Ray Topography as a Non-Destructive Monitor of Damage Accompanying IC Processing
Authors: Dudley Michael , Wang Franklyn F.Y. , Fanning Thomas , Gordon-Smith David
Published: March 2011

Synchrotron white beam x-ray topography in transmission geometry has been used to monitor the damage accompanying a Rapid Thermal Processing (RTP) treatment of Si wafers. The behavior of low and high carbon-content Si is contrasted and discussed. The applicability of this technique to this kind of study is demonstrated, with particular emphasis being laid on its non-destructive nature. The general usefulness of the technique as a monitor for damage accompanying IC processing is discussed.
Investigation of Metal Induced Surface Defects in Czochralski Si Following Rapid Thermal Processing by Thermal Wave Modulated Reflectance Method
Authors: Hahn S. , Smith W.L , Suga H. , Park J.-G. , Lim C.-S. , Kwak Y.-S. , Meinecke R. , Kola R.R. , Rozgonyi G.A. , Kwack K.D.
Published: March 2011

Using thermal wave mapping and imaging techniques in conjunction with x-ray transmission topography and transmission electron microscopy, precipitation behavior of various fast and slowly diffusing metallic impurities such as Au, Co, Cu, Fe, Mo, Ni, Pd, Pt, W and Zn in Czochralski Si following rapid thermal processing are investigated. Our data have shown that thermal wave signal is sensitive to certain types of metal-induced surface defects (most likely metal silicides) and associated crystallographic defects. In addition, the comparison between thermal wave and x-ray imaging methods shows an interesting speciesdependent complimentary relationship.
Crystal Nucleation in Amorphous Si Films on Glass Substrate by Si+ Ion Implantation
Authors: Yamaoka Tomonori , Oyoshi Keiji , Tagami Takashi , Arima Yasunori , Tanaka Shuhei
Published: March 2011

Crystallization of amorphous Si films on a glass substrate using Si+ ion implantation is investigated. 100keV and 180keV Si+ ion implantations into 600nm-thick amorphous Si layers crystallize half and almost all of the film thicknesses, respectively. This result demonstrates that crystallization by ion implantation, which contains both crystal nucleation and grain growth, is due to ion-solid interaction, and not to “pure” thermal effect by ion beam heating. Furthermore, two distinct regions are observed in transmission electron microscopy investigation of grain size at different depths of crystallized Si/SiO2 multi-layer specimens. The deep region below the projected range is composed of grains smaller than in the shallow region. This result is strongly related with crystal nucleation and growth kinetics by ion implantation.
Substrate Effects on the Kinetics of Solid Phase Crystallization In a-Si
Authors: Haji L. , Joubert P. , Guendouz M. , Duhamel N. , Loisel B.
Published: March 2011

The effect of substrate nature on the solid phase crystallization at 600 °C of a-Si deposited by low pressure chemical vapor deposition is investigated by x-ray diffraction and transmission electron microscopy. The nucleation rate varies slightly resulting to a weak variation in the final grain sizes as a function of the substrate type. In all cases the grain growth mode is found to be three dimensional. In contrary, a drastic effect of the substrate is observed for films deposited by plasma enhanced CVD. Fast crystallization is obtained on indium tin oxide (ITO) resulting to small grain poly-Si, whereas the crystallization is retarded on glass leading to an increase in the grain size.
Crystallization Processes in Amorphous Hydrogenated Silicon Based Alloys
Authors: Demichelis F. , Pirri C. F. , Tresso E. , Battezzati L. , Giamello E. , Menna P.
Published: March 2011

Amorphous and microcrystalline films of silicon and silicon carbide have been deposited by means of PECVD at low substrate temperature (200°C), with reactive gases highly diluted in H2. Devices quality a-Si:H films have been annealed in vacuum at temperatures in the range 200- 1000 °C. The transition from amorphous to crystalline structure was studied by X-ray, Raman and I.R. spectroscopies, optical analysis in UV-VIS-NIR region, Transmission Electron Microscopy, Differential Scanning Calorimetry and Electron Spin Resonance measurements. By comparing the results of the two methods to obtain microcrystalline films we have deduced information on the process of growth of Si and SiC microcrystals.
Crystallization of Amorphous Si In Al/Si Multilayers
Authors: Konno Toyohiko J. , Sinclair Robert
Published: March 2011

The crystallization of amorphous Si in a Al/Si multilayer (with a modulation length of about 120Å) was investigated using transmission electron microscopy, differential scanning calorimetry and X-ray diffraction. Amorphous Si was found to crystallize at about 175 °C with the heat of reaction of 11±2(kJ/mol). Al grains grow prior to the nucleation of crystalline Si. The crystalline Si was found to nucleate within the grown Al layers. The incipient crystalline Si initially grows within the Al layer and then spreads through the amorphous Si and other Al layers. Because of extensive intermixing, the original layered structure is destroyed. The Al(111) texture is also enhanced.
Controlled Interface Roughness in GaAs/AlAs Superlattices
Authors: Miller William R. , Boettinger W. J. , Tseng W. F. , Pellegrino J. , Comas J.
Published: March 2011

We report the results of our study of controlled interface roughness in low-order GaAs/AlAs superlattices. Samples were prepared using either the interrupted growth or the migration-enhanced epitaxy (MEE) technique. The samples were prepared with m atomic planes of GaAs and m atomic planes of AlAs (m × m) per modulation wavelength and repeated p times. For this study, m = 1 or 3. The samples were studied using X-ray diffraction. The interrupted growth samples both showed a split in one diffraction line indicating layers were not of integral order while the MEE samples showed no splitting, indicating integral order layers.
Periodicities in the X-Ray Diffraction of Low Order ALAS/GAAS Superlattices
Authors: Pellegrino Joseph , Qadri S. , Tseng W. , Miller W. R. , Comas J.
Published: March 2011

In this work we examine the physical properties for the superlattice system (GaAs)n1 (AlAs)n2/GaAs(100) for low values of n1 and n2, i.e., n1 = n2 = 3, 6, 12. Normal, interrupted growth, and migration enhanced epitaxy (MEE) growth techniques were used to grow the superlattice structures in a molecular beam epitaxy system. X-ray diffraction spectra were obtained, and the major and satellite peak positions were analyzed to obtain the superlattice periodicity. An analysis of the major diffraction peaks and their associated satellites produced superlattice periodicity in good agreement with theory. Diffraction peaks were also observed in regions adjacent to the primary diffraction peaks which did not occur in the expected satellite positions. An analysis of these peaks relative to the primary peak indicate periodicities corresponding to layer thickness greater than the intended period. One possible cause for these periodicities is growth conditions that exist during the growth of the superlattice which result in the deposition of fractional monolayers. In this study we present results which suggest that an arsenic-deficient growth condition may be a contributing factor in the deposition of fractional monolayers.
Material Requirements for Reversible Phase Change Optical Recording
Authors: Rubin Kurt A.
Published: March 2011

The science and technology underlying phase change reversible optical storage, with an emphasis on the media, are reviewed. The transformation kinetics and their effect on writing (amorphization), erasing (crystallization) and long-term data stability are discussed. Phase separation is shown to affect cyclability and cause increased media noise. A readback CNR of 65.0 db was obtained by eliminating grooves as a source of media noise and using a recording layer which crystallizes into a cubic phase. Recording performance at short wavelengths is discussed.
Anomalous Point Defect Injection During Pulsed Laser Melting Processes: Direct Evidence of Gai and Asi Profiles in GaAs
Authors: Chang Yih , Sigmon Thomas W.
Published: March 2011

Significant point defect injection during a pulsed laser melt process is reported for the first time. Heteroepitaxial InxGa1-xAs/GaAs layers fabricated by a pulsed laser induced epitaxy technique are used in this study. Transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) and secondary ion mass spectrometry (SIMS) are employed to study the redistribution behavior of each species on the atomic scale. It is found that both the Si dopant species and the Ga, As, and In host atoms are injected into the underlying GaAs substrate. These species are then significantly redistributed, forming near spherical As-rich regions. Direct evidence of Asi and Gai (Ga and As interstitialcies) profiles in the GaAs substrate are also obtained for the first time. A hypothesis, based upon the combined effects of concentration impulse and large temperature gradients across the liquid-solid interface, is proposed to explain the significant solid phase diffusion observed during the pulsed laser melting process. We estimate the temperature gradient induced electric field during the process to be on the order of 104V/cm.
Nanostructure Evolution During the Transition of TiO2, PbTiO3 and PZT
from GELS to Crystalline thin Films.
Authors: Kang Z. C. , Gupta A. , Mckelvy M. J , Eyring L. , Dey S. K.
Published: March 2011

The nanostructure evolution of PZT, PT and T thin films has been studied by high-resolution electron microscopy (HREM) supported by other techniques such as thermal analysis, thermal mass spectrometric analysis and X-ray diffraction analysis. The evolution follows a common progression from amorphous film, to the development of condensed regions that develop crystalline order, to the final polycrystalline oxide thin film. If the precursor gel contains lead, the film develops fluctuating surface “blisters” that evolve to an oxide final product as well. Minor structural and compositional differences exist across the final oxide thin film.
Metastable Pyrochlore Structures in Sol Gel Spin Coated Lead Titanate Thin Films on Silicon Substrate
Authors: Lee Jeon-Kook , Jung Hyung-Jin , Kim Chong-Hee
Published: March 2011

High quality lead titanate thin films were fabricated by spin coating on a silicon substrate. The resulting dried gel layers were uniform in thickness through 2 ' area, and polycrystalline perovskite structures developed almost crack free with a heat treatment above 500°C in films with thickness above 0.36μm.

Metastable pyrochlore structures were observed in films with thickness of 0.16,μm when heat treated at 500 and 600 °C. But these structure did not appear in films with thickness of 0.36μm.The thickness dependencein crystal structure of films was studied by varing the substrate condition and analyzing the interface between the.film and. substrate. In native oxide films on silicon substrates, amorphous dried gel layers were heterogeneously nucleated. Metastable cubic pyrochlore structure could be crystallized in amorphous native oxide (cubic property in random network structure).
Oxidation Kinetics of Yba2Cu3OT7-x Thin Films in the Presence of Atomic Oxygen and Molecular Oxygen by In-Situ Resistivity Measurement
Authors: Yamamoto K. , Lairson B. M. , Bravman J. C. , Geballe T. H.
Published: March 2011

The kinetics of oxidation in Yba2Cu3O7-x thin films in the presence of molecular and atomic oxygen ambients have been studied. The resistivity of c-axis, a-axis, and mixed a+c axis oriented films, deposited in-situ by off-axis magnetron sputtering, was measured as a function of time subsequent to a change in the ambient conditions. The oxidation process is shown to be thermally activated and can be characterized by a diffusion model with an activation energy which varies from approximately 1.2eV in the presence of molecular oxygen to 0.6eV for a flux of 2×1015 oxygen atoms/cm2sec. In both cases, diffusivity is found to be insensitive to oxygen stoichiometry, but the rate of oxidation is found to be sensitive to the microstructure and orientation of the films.
Nucleation and Growth kinetics of Cu2O During Reduction of CuO Thin Films
Authors: Li Jian , Tu K. N. , Mayer J. W.
Published: March 2011

The combination of 16O(α, α)16O oxygen resonance measurement and transmission electron microscopy (TEM) provides an unique and effective method to study the kinetics of nucleation and growth of Cu2O phase during reduction. In situ TEM observation showed that isolated and large Cu2O grains emerge from the small CuO grain matrix and the growth of Cu2O grains is linear with time. We propose that the discontinuous morphology of grain growth of Cu2O is due to the migration of the Cu2O-CuO phase boundary induced by oxygen out-diffusion along the moving phase boundary. Based on the classical analysis of phase transformation by Johnson, Mehl and Avrami, the activation enthalpy of nucleation of Cu2O phase in the CuO matrix has been deduced as ΔEn=2.3 eV. The specific interfacial energy between CuO and Cu2O phases has been estimated as 0.5 eV/atom.
Nucleation and Abnormal Grain Growth of Alpha-A12O3 in Gamma-Alumina Matrix
Authors: Chou T. C. , Nieh T. G.
Published: March 2011

The microstructures of reactive sputter-deposited alumina films have been studied by transmission electron microscopy. The as-deposited films contained γ-A12O3 phase in an amorphous alumina matrix. Annealing of the films at 1200° C for 2 h resulted in nucleation and concurrent anomalous grain growth of α-A12O3 in a polycrystaUine γ-Al2O3 matrix which exhibited a layered microstructure and was strongly textured along [001]. The grain sizes of α-A12O3 varied from 3 to 20 μm, while the average grain size of γ-A12O3 was only about 50 nm. It appears that the nucleation kinetics of a-A12O3 was slow. As a result, the abnormal grain growth of α-A12O3 proceeded by consuming surrounding γ-Al2O3 grains. An atomic model is presented to explain the origin of layered structure in γ-A12O3. The nucleation mechanism of a-A12O3 in γ-alumina matrix is suggested. Orientation relationships between γ- and α-A12O3 are reported. The anomalous grain growth of α- A12O3 is discussed in terms of γ/α interface boundary migration.
Interaction Between Dislocations and NiFe2O4 Precipitates In A NiO Matrix
Authors: Summerfelt Scott R. , Carter C. Barry
Published: March 2011

Three different types of dislocation interactions with NiFe2O4 (spinel crystal structure) precipitates in a NiO matrix have been studied. In the first, the movement of dislocations introduced by room temperature deformation is impeded by the spinel precipitates. Glide dislocations in the NiO with ½<011> Burgers vectors and {011} glide planes cannot pass through the spinel precipitates without forming stacking faults because the perfect NiO dislocations are partial dislocations in NiFe2O4. Many dislocation loops but no stacking faults were observed in the deformed samples indicating that the gliding dislocations formed the loops when they moved past the precipitates. In the second type of interactions, cusps were formed in the spinel-NiO interface at close to the dislocation loops when the sample was heat treated; the cusps indicate preferential dissolution of the spinel. In the final interaction, the dislocations were shown to act as preferential nucleation sites when spinel was precipitated from the NiO matrix. At slow nucleation rates, NiFe2O4 precipitated only on the dislocations; when the nucleation rate was increased, precipitation occurred both on and away from the dislocations. Precipitates which form at a dislocation may contain a stacking fault extending from the partial dislocation to a cusp in the spinel-NiO interface. When this occurred, the stacking faults were observed to be faceted parallel to either {111} or {011} planes.
Spin Polarized Low Energy Electron Microscopy of Surface Magnetic Structure
Authors: Altman M. S. , Pinkvos H. , Hurst J. , Poppa H. , Marx G. , Bauer E.
Published: March 2011

Spin polarized low energy electron microscopy (SPLEEM) has been developed for the high resolution imaging of surface magnetic structure. The existing LEEM ha.s been modified by the incorporation of a. GaAs-type spin polarized electron gun. Large image contrast arises due to the spin-dependent exchange scattering, whifle the st.in-orbit contribution vanishes uniquely for the normal incidence/exit geometry used here. Pixel by pixel image subtraction for incident electron beams of opposite polarization yields precisely the spatially resolved Bragg reflection asymmetry observed in spin polarized low energy electron diffraction. The shallow electron penetration depth arising from the strong coulombic interaction is advantageous for separating surface behavior from the normally overwhelning bulk. Therefore, the use of transversally polarizedI electron beams allows the determination of in-plane surface magnetization directions. Fnrthermore, the parallel illumination and detection of SPLEEM makes it possible to image quickly with a. resolution better than 500 Å in the present configuration. A useful and direct. comparison between surface magnetic, structural, and topological features is made possible by the augmentation of the unique imaging capabilities of conventional LEEM with the magnetic sensitivity of SPLEEM. In this manner, the magnetic domain structure of a Co (0001) surface and in-situ grown Co filmns on Mo(110) have been determined.
Magnetic Properties and Micromagnetic Character of RF Sputtered Co Thin Films on Thin Cr Underlayers
Authors: Yeh T. , Sivertsen J. M. , Judy J. H.
Published: March 2011

The effect of thin Cr underlayers on the coercivity, the initial susceptibility, and micromagnetic structure of RF sputtered Co/Cr thin films have been studied. A reciprocal relationship between the initial susceptibility and the coercivity of the RF sputtered Co/Cr films were observed. Micromagnetic images of these Co/Cr films obtained by Fresnel mode Lorentz TEM revealed a refinement of the micromagnetic images correlated with a simultaneous increase in coercivity and decrease in initial susceptibility. Such behavior is expected in cases where the initial magnetization and magnetization reversal are hindered by the variation of local energy with the magnetic moment distribution. The interaction of the Cr underlayers with the Co magnetic overlayer very likely induces fluctuations in local magnetic energy of the Co films. Accordingly, the initial magnetization and magnetization reversal are likely to be impeded by fluctuations of the magnetic energy resulting in the observed increase in coercivity and decrease in initial susceptibility.
Interdiffusion Kinetics and Magnetic Properties of TA-Permalloy Multilayers
Authors: Hashim I. , Atwater H. A. , Kung K. T. Y. , Valletta R. M.
Published: March 2011

The interdiffusion kinetics of ultrahigh vacuum deposited Ta/Ni81Fe19 short-period multilayers films have been investigated, and changes in microstructure were related to magnetic properties. Small angle X-ray diffraction and transmission electron microscopy were used to study layer morphology evolution and interdiffusion during post-growth isothermal annealing in the temperature range 300 – 600°C. The kinetic analysis suggests that interface roughening due to grain growth, and grain-boundary mediated diffusion of Ta occurs concurrently at early anneal times in the Ni81Fe19 films. Subsequent grainboundary and lattice diffusion of Ta lead to a reduction of magnetization and increase in coercivity of Ni81Fe19.
Dynamic Magnetic Permeability of Composite Iron Films
Authors: Antonov A. S. , Dyachkov A. L. , Lagar A. N. , Kov  , Panina L. V.
Published: March 2011

Both frequency and field dependencies of the ac magnetic permeability in composite iron films were measured for different thickness of a conducting cell. Attention has been focused on additional dispersion caused by the skin effect. The data obtained are analyzed on the basis of the effective medium approximation.
Crystal Structure and Magnetic Properties of Co-Based Alloy Thin Film Prepared on Cr Underlayer With Good Crystallite Orientation
Authors: Kawanabe T. , Park J. G. , Naoe M.
Published: March 2011

Co85Cr15-xTax(x:0, 2at%)/Cr films with microscopically flat surface were investigated for high density recording media. These films were deposited on silicon wafer and glass substrates at the substrate temperature Ts of 350 °C at argon pressure as low as sub-mTorr by using Facing Targets Sputtering (FTS) apparatus. The elevating of Ts promoted the Cr(200) orientation in film plane, leading to the in-plane c-axis orientation of Co crystallites. Addition of some elements such as Si, Ge and Ta in Cr thin film was found to stabilize Cr(110) crystal orientation even at Ts of 300 °C.
The Effect of Annealing on NiFe/FeMn Thin Film Couples
Authors: Hwang Cherngye , Parker Michael A. , Howard J. Kent
Published: March 2011

The antiferromagnctic FeMn thin film has been used to stabilize the domains in NiFe films by exchange-coupling, thus eliminating the Barkhauscn noise in magnetoresistive sensor designs. T'he strength of this exchange-coupling is highly dependent on the interfacial structure, as well as the interfacial composition of this NiFe/FeMn thin film couple. We have conducted isothermal, as well as isochronal anneals of NiFe/FeMn thin film couples, and monitored their magnetic properties, in particular the strength of their exchange-coupling. The strength of exchange-coupling, measured by the shift of the B-H loop obtained from a hysteresis loop tracer, increased monotonically with annealing time for isothermal anneals between 200 and 300 °C. At higher temperatures (up to 500°C), the interdiffusion between the two layers is so extensive that the NiFe layer loses its sort-magnetic properties and the coupling strength is degraded. Composition depth-profiling by scanning Auger analysis was conducted to study the interdiffusion profiles of the annealed samples. Cross-section transmission electron microscopy (XTEM) was used to study the microstructure, crystallography, and composition of these thin films after annealing. Micro-beam composition analysis was also carried out and the compositional profile obtained was compared to the Auger depth-profile results. Transmitted electron diffraction using selected area electron diffraction (SAED) and elongated probe micro-diffraction (EPMD) of XTEM samples was used to study the crystallography of these films.
Mössbauer Analyses of FeSiAl Films Sputtered in Ar or 4%N2 Mixture Atmosphere
Authors: Inoue K. , Tatsumi M. , Sakata T. , Tanabe S. , Ozeki T. , Shibata H.
Published: March 2011

Microstructural differences between sendust(FeSiAl) films sputtered in pure Ar atmosphere and FeSiA1N films sputtered in Ar+4%N2 mixture atmosphere were measured using Mössbauer effect. These films were prepared by a conventional RF sputtering method. As a source for the Mössbauer measurement, 57Co was used.

Before annealing, there are no differences between both films in Mössbauer spectra. The both patterns are observed as simple six-line spectra from Fe atoms in a disordered structure. After annealing, both patterns are not simple six-line spectra, which indicate there are more than two types Fe site in the crystal. A tremendous difference between both films appears in the spectra. 95% Fe atoms of FeSiAl film are at the two different sites of D03 structure. However, in FeSiAlN film, only 54& Fe atoms are at the D03 sites and about 30% Fe atoms are at different sites whose hyperfine field is about-250kOe. This value of hyperfine field is expected at a D03-like site with 5 Fe nearest neighbors. This D03-like site is explained as a site that one Fe atom is substituted for one D-site Si or Al atom in a D03 unit cell.

No Fe-nitrides were observed in FeSiAlN films.
Thickness Effects on the Magnetic Hysteresis of Equiatomic CoPt Films
Authors: Tsoukatos A. , Hadjipanayis G. C. , Zhang Y. J. , Waite M. , Swann C. P. , Shah I.
Published: March 2011

The magnetic hysteresis behavior of crystalline Co50Pt50films has been studied in samples with thickness in the range of 100-2000 Å. The room temperature coercivities of the as-grown films are of the order of 100 Oe. After annealing at 650°C the coercivities vary between 400 and 4300 Oe with the higher values obtained in thicker specimens. The high coercivities obtained are attributed to the hard magnetic phase CoPt with an ordered fct structure that is formed after annealing. The variaton of coercivity with thickness is examined and related to the crystal structure evolution and to grain size effects.
A New Class of Permanent Magnets - High Temperature Superconductors
Authors: Chen In-Gann , Liu Jay , Weinstein Roy
Published: March 2011

For type II superconductors (SC), magnetic field can be trapped, or pinned due to persistent internal current. Upon magnetization, SC samples behave in some ways similar to a metallic permanent magnet. The trapped field is high and quasi-persistent, and we refer to it as a “magnet replica”. So far, nearly 1T @ 65 K, and over 0.4 T @ 77 K have been measured within small (about 1 × 1 × 0.6 cm3) melt-textured Yba2Cu3Ox (MT-Y123) samples. Based on our theoretical studies, extrapolation to larger scale magnets indicates that 2–4 Tesla in liquid Nitrogen (and even larger field at lower temperatures) is achievable with our high temperature superconductor (HTS) material. Using this effect, magnets with dipole, quadrupole, or more complicated configurations can be made of existing MT-Y123 material, thus bypassing the need for HTS wires. Two types of motors have been successfully constructed, using the trapped field in MT-Y123 samples.

The spatial distribution of the trapped magnetic field on MT-Y123 materials has been studied. A phenomenological model has been developed to account for the trapped field intensity and profile in HTS samples. General features of magnet replicas by HTS will also be discussed.
Microstructure and Recording Noise of Thin Film Longitudinal Media
Authors: Yogi Tadashi , Nguyena Thao A. , Lambert Steven E. , Gorman Grace L. , Castillo Gil
Published: March 2011

The magnetic and recording characteristics of Co-based thin film media are strongly influenced by microstructure. The media microstructural characteristics, in turn, depend on sputtering conditions of underlayers and magnetic layers. The role of Cr underlayer thickness and sputtering pressure have been reported previously. The present work examines the growth morphology and recording properties of a CoPtCr alloy on Cr underlayers where the deposition conditions such as sputtering pressure and rf bias were independently varied for the Cr underlayer and the magnetic layer. We find that the growth morphology of the magnetic layer is governed primarily by the deposition condition of the Cr underlayer. In particular, increased sputtering pressure for the Cr underlayer produces columnar morphology which induces isolation of the grains in the magnetic layer. This results in a significant reduction in the recording noise due to reduced intergrain exchange coupling. On the other hand, the application of ff bias during the deposition of the magnetic layer promotes more continuous magnetic grains, thereby increasing the recording noise. The observed trends in microstructure and recording noise can be understood qualitatively in terms of Thornton's microstructure diagram and the competition between micromorphological roughness and adatom mobility during the film growth.
Influence of Interfaces on Magnetooptical Effects in Multilayers
Authors: Višňovský Štefan
Published: March 2011

The paper deals with the electromangetic theory of the optical interactions in planar multilayer (ML) structures displaying magnetic order. The main attention is focussed on the practically important configuration of normal incidence and polar magnetization in an originally isotropic medium. The procedure providing the information on the ML optical response is treated in detail. It assumes that the thickness and optical parameters in each layer entering the ML structure allong with the azimuth and ellipticity of the incident wave are given as the input data. The optical response is given in terms of the complex amplitudes of the reflected and transmitted waves from which the ML optical parameters, i.e. “Kerr” and “Faraday” effects, transmission, reflectivity, quality factor, etc., can be derived. The experience has shown that the procedure gives plausible results even for ML structures consisting of the layers the thicknesses of which are in the nanometer range, i. e. in the range where the interface effects play an important role.
Atomic Level Characterization of the Morphology of Phases in Chromindur Magnetic Alloys
Authors: Miller M. K , Camus P. P. , Hetherington M. G.
Published: March 2011

The atom probe field ion microscope has been used to characterize the morphology and determine the compositions of the iron-rich a and chromium-enriched α′ phases produced during isothermal and step cooled heat treatments in a Chromindur II ductile permanent magnet alloy. The good magnetic properties of this material are due to a combination of the composition of the two phases and the isolated nature and size of the ferromagnetic a phase. The morphology of the a phase is produced as a result of the shape of the miscibility gap and the step-cooled heat treatment and is distinctly different from that formed during isothermal heat treatments.
Substrate-Deposition-Teiimperatijre Dependence of Perpendicular Magnetic Anisotropy in (Fe/Pt) Compositionally-Modulated Films
Authors: Iwata S. , Parkin S. S. P. , Nuri H. , Suzuki T.
Published: March 2011

A systematic study on magnetic properties of (Fc/Pt) compositionally-modulated films as a function of substrate-deposition-temperature has been carried out. For films with (2.5ÅFe/18ÅPt)×40, the intrinsic perpendicular magnetic anisotropy Kuis found to increase with decreasing temperature for all the sarmples deposited at temperatures from -114 °C to 220°C during deposition. The higher the substrate-deposition-temperature, the larger the Kuvalues become. This result implies a possible contribution from the magne to-elastic effect to the total anisotropy. However, a major part responsible for the perpendicular anisotropy may be found in other mechanisms. The saturation magnetization is found to exceed the value for pure Fe at temperatures lower than 180K.
Precision Ion Milling of Layered, Multi-Element TEM Specimens with High Specimen Preparation Spatial Resolution
Authors: Anderson Ron , Benedict John
Published: March 2011

It is now a requirement in the semiconductor industry to prepare TEM specimens of pre-specified regions with a specimen preparation resolution exceeding 100nm. In other words, given the coordinates x, y, z of the location desired for TEM analysis, the TEM specimen preparation procedure must yield a thin TEM specimen containing the point x, y, z plus or minus 100nm. Preparation of failure analysis specimens in other fields of endeavor, such as: metallurgical, ceramic, composite material laboratories etc., have specimen preparation spatial resolution requirements below one micron in some cases with the likelihood that greater precision will be required in the future.
A High Resolution TEM Specimen Thinning System
Authors: Clampitt R. , Ross G. G. , Phelan M. , Davies S. A.
Published: March 2011

Improvements in specimen preparation for TEM analysis are being constantly sought, particularly in the study of microelectronics' materials and in failure analysis of devices. We describe here a compact commercial system capable of thinning (milling) selected regions of a specimen by means of a scanned focused ion beam of sub-micron spatial resolution.