bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural and Magnetic Study of Fe Stripes and Boxes Patterned by the  Method
Authors: Ressier L. , Jaffres H. , Schuhl A. , Nguyen Van Dau F. , Goiran M. , Redoules J.P. , Peyrade J.P. , Fert A.R.
Published: April 2011

The  method has been successfully used to cut a Fe thin film, epitaxially grown onto a (001) MgO substrate, into stripes (widths ranging from 1 μm to 100 nm) and boxes (lateral sizes ranging from 1 μm to 3 μm). A structural analysis of these magnetic structures by atomic force microscopy has shown that their geometries are controlled by the plastic strain. A magnetooptical study of the Fe stripes has revealed a surprising uniaxial magnetic anisotropy with an in-plane easy axis perpendicular to the stripes. This strong anisotropy can be explained by an anisotropie relaxation of the misfit between the starting Fe film and the MgO substrate, induced by the cutting into stripes. Magnetooptical experiments on boxes have revealed that the initial cubic symmetry is recovered since, in this case, the relaxation is similar in perpendicular directions. They have also proved that their magnetization reversal is governed by nucleation phenomena.
Magneto-Optical Properties of Ni-MgO and Co-MgO Nanocomposite Films Obtained by Partial Reduction Reactions
Authors: Smith J. A. , Limthongkul P. , Hartsuyker L. , Kim S. Y. , Sass S. L.
Published: April 2011

A new processing technique was developed to synthesize metal-ceramic films containing nano-sized Ni or Co particles embedded in a MgO matrix. Sol-gel solutions were spun on different substrates with varying coefficients of thermal expansion, oxidized by heating in air and reduced to form a metal-ceramic two phase mixture. This method allows the generation of perpendicular magnetic anisotropy by use of residual stresses arising from a coefficient of thermal expansion difference between the film and substrate. Magneto-optical measurements show that the films can have relatively large Kerr and Faraday rotations, and that the metal particles have sufficient vertical magnetic anisotropy to support perpendicular magnetization. The magneto-optical properties of the films are related to the metal particle size, film thickness and substrate choice.
Giant Magnetoresistance of Self-Assembled ErAs Islands in GaAs
Authors: Schmidt D.R. , Ibbetson J.P. , Brehmer D.E. , Palmstrøm C.J. , Allen S.J.
Published: April 2011

We have integrated nanometer-sized ErAs islands in GaAs, resulting in a nano-composite of paramagnetic particles in a semiconductor. Negative giant magnetoresistance of up to four orders of magnitude is observed at low temperatures. We can control the density and size of the ErAs islands, making this an ideal system to investigate transport in magnetic nano-structures.
Strain Effects in Superlattices of Diluted Magnetic Semiconductor ZnTe/Zn1-xMnxTe
Authors: Chen Chenjia , Chen Xi , Li Xiaoli , Li Haitiao , Wang Xuezhong , Ling Zhen , Wang Jie , Wang Xun
Published: April 2011

ZnTe/Zn1-xMnxTe superlattices were grown on GaAs (001) substrates by molecular beam epitaxy. The multi-phonon processes including overtones and combinations of optical phonons have been studied by near resonant Raman scattering in the temperature range 13 K to 300 K. The strain arising from lattice mismatch gives rise to a shift in the optical-phonon frequencies. A two-phonon interface mode of superlattice has been observed and identified for the first time. Strain-induced red shifts of exciton energies related to transitions from the conduction subband to the light-hole and heavy-hole subband have been found by photoreflectance measurements. Experimental results agree well with the calculated strain-induced shift in superlattices.
Transport Measurements of Magnetic Multilayers at Reduced Lateral Dimensions
Authors: Park Y.D. , Hudspeth H.D. , Schultz T.J. , Cabbibo A. , Caballero J. A. , Sharifi F. , Childress J.R.
Published: April 2011

Abstract We report on the fabrication and transport properties of magnetic multilayers with widths down to 100 nm. We employ e-beam processed nano-deposition masks to pattern magnetic multilayers which define nano-wires by lift-off or by a removal process such as ion-milling. Two different magnetic multilayer systems (antiferromagnetically coupled Co/Cu multilayers and NiFe/Cu/Co spin-valves) are investigated. Structures resulting from the lift-off process show high contact resistance and high resistivities while ion-milled structures show resistivities close to that of bulk. For Fe(50Å)/[Co(15Å)/Cu(20Å)]x20 /Cu(30Å), patterned nano-wire structures display no negative magnetoresistance but a positive magnetoresistance that is linear with applied field and no apparent hysteresis. For Ta(50Å)/NiFe(50Å)/Cu(35Å)/Co(20Å)/Cu(30Å), we found the resistance to decrease as the absolute value of magnetic field is decreased and found hysteresis to be present.
Stability of Nitrogen in Sputtered Iron Nitride thin films and Multilayers
Authors: Chatbi H. , Vergnat M. , Bobo J. F. , Hennet L.
Published: April 2011

Different phases of FeN thin films and Fe/FeN multilayers were prepared by reactive rf sputtering. The release of nitrogen and the crystallographic transformations during annealing were monitored by thermal desorption spectrometry and X-ray diffraction experiments. Finally, the diffusivity of nitrogen in the γ-Fe4N phase was evaluated.
Investigation of Anisotropy Effects and Interlayer Exchange Coupling by Locally Resolved Photothermally Modulated Ferromagnetic Resonance
Authors: Meckenstock R. , Pelzl J. , Frait Z.
Published: April 2011

The photothermally modulated ferromagnetic resonance (PM-FMR) has been successfully applied to investigate the position dependence of FMR properties of wedged Fe-samples. The temperature dependence of the surface contribution to the anisotropy could be separated from the demagnetizing field with high accuracy. The oscillating first order interlayer exchange coupling and the anisotropy fields of the Fe-films of a Fe/Cr-wedge/Fe-sample (3.0/0.7–2.8/2.0 nm) were deduced from PM-FMR spectra.
Molecular Self-Assembly of Fe3O4/Polyimide Nanocomposite Films (I)
Authors: Liu Yanjing , Wang Anbo , Claus Richard O. , Jiang Eric
Published: April 2011

Layer-by-layer molecular self-assembly of nanosized magnetite (Fe3O4) particles and polyimide precursor molecules into multilayer ultrathin films has been accomplished on single crystal silicon and quartz substrates. This process involves the alternate dipping of a substrate into an aqueous solution of cationic polymer which coats on nanoscale Fe3O4 particles as a stabilizer followed by dipping into an aqueous solution of anionie polyimide precursor (polyamic acid salt, PAATEA). The growth process and the structure have been characterized using UV-vis spectroscopy, FT-IR, and scanning electron microscopy. The results demonstrate that well-ordered uniform monolayer and multilayer magnetic films have been formed on silicon and silica surfaces.
Theoretical Investigations on the Magneto-Optical Properties of Transition Metal Multilayer and Surface Systems
Authors: Ebert H. , Perlov A. , Yaresko A. N. , Antonov V. N. , Uba S.
Published: April 2011

Results of theoretical investigations on the magneto-optical Kerr-effect in layered systems are presented that are based on a fully relativistic description of the underlying electronic structure. To investigate the importance of the various sources of the Kerr effect model calculations have been performed. Applications to multilayer systems have been done for systems with non-magnetic spacers having a relatively high (Co/Pd, Co/Pt) as well as a small induced magnetic moment (Co/Cu) and comparison with experiment is made. To investigate surface layer systems the use of auxiliary model multilayer systems is explored.
Magnetic Stripe Domains in Fe/Ni Multilayers
Authors: Donzelli O. , Vatucello G. , Nizzoli F. , Palmeri D. , Lucari F. , D'Orazio F.
Published: April 2011

Magnetic Fe/Ni multilayers, investigated by Magnetic Force Microscopy (MFM), show a stripe domains structure in which the magnetization is oriented in the film plane. This structure is attributed to the equilibrium configuration between competing in-plane anisotropy of the Ni layers and perpendicular anisotropy due to the thin Fe layers.
Magnetoresistance Effects in Granular Thin Layers Formed by High Dose Iron Implantation Into Silicon
Authors: Wong S.P. , Cheung W.Y.
Published: April 2011

High dose iron implantation into silicon substrates has been performed with a metal vapor vacuum arc ion source to doses ranging from 5×1016 to 2×1017 cm'2 at various beam current densities. The magnetoresistance (MR) effects in these implanted granular layers were studied at temperatures from 15K to 300K. A positive MR effect, i.e., an increase in the resistance at the presence of a magnetic field, was observed at temperatures lower than about 40K in samples prepared under appropriate implantation conditions. The magnitude of the MR effect, defined as ΔR/Ro ≡ (R(H)-Ro)/Ro where R(H) and Ro denote respectively the resistance value at a magnetic field intensity H and that at zero field, was found to depend not only on the implantation dose but also on the beam current density. This is attributed to the beam heating effect during implantation which affects the formation of the microstructures. The ratio δR/Ro was found to attain high values larger than 400% for some samples at low temperatures. The dependence of the MR effects on temperature, implantation dose, and beam current density will be presented and discussed in conjunction with results of transmission electron microscopy.
Observation of an Exponential FeSi Spacer Thickness Dependence of the Antiferromagnetic Exchange Coupling in Fe/Si-Based Multilayers
Authors: Kohlhepp J.T. , De Vries J.J. , Den Broeder F.J.A. , Coehoorn R. , Jungblut R.M. , Reinders A. , Strijkers G.J. , Smits A.A. , Mde Jonge W.J.
Published: April 2011

The magnetic interlayer exchange coupling in Fe/Si-based thin film structures employing sputtered multilayers with variations of Si-alloyed Fe for the magnetic layers and Fe-alloyed Si spacers, as well as wedge-shaped MBE-grown Fe/Si/Fe sandwich samples has been systematically studied. From structural and magnetic analysis it is concluded that ultrathin Si and FexSi100-x (x < 50) spacer layers transform into a crystalline iron suicide with a composition close to Fe50Si50. The exchange coupling mediated by this metallic suicide is antiferromagnetic and depends on the spacer thickness in an exponential, i.e. non-oscillatory, manner with a universial characteristic decay length of 3–4 Å at room temperature. This observation can be qualitatively explained within the framework of a recent coupling theory on the premise that the FeSi interlayer has the metastable CsCl(B2)-structure.
Giant Magnetoresistance Induced by Ultrathin Magnetic Layers
Authors: Strijkers G.J. , Swagten H.J.M. , Mettler A.H.M. , Willekens M.M.H. , De Jonge W.J.M.
Published: April 2011

We introduce an interface selective structure, composed of a spin-valve on top of which a thick nonmagnetic back layer is deposited as a straightforward experimental tool to measure the GMR induced by ultrathin magnetic layers. The interface selectivity of spin-dependent scattering is evidenced by calculations and illustrated in both Co/Cu/Co and Ni80Fe20/Cu/Ni80Fe20 spin-valves by an almost discontinuous behavior in the GMR ratio. The temperture dependence of the extremely short length scale associated with this discontinuity is discussed in relation to the structure of ultrathin ferromagnetic layers.
Effects of Electron Beam Exposure on Poly(Arylene Ether) Dielectric Films
Authors: Drage J. S. , Yang J. J. , Choi D. K. , Katsanes R. , Lau K. S. Y. , Wang S.-Q. , Forester L. , Schilling P. E. , Ross M.
Published: April 2011

This paper presents a study of the effects of electron beam (e-beam) exposure on the chemical and physical properties of FLARE™ 1.0X, a non-fluorinated member of the FLARE™ family of poly(arylene ether) dielectric coatings. Spin-coated films of this poly(arylene ether) were cured by large-area e-beam exposure, as well as by conventional thermal processing. Neither swelling nor dissolution was observed for the e-beam cured films after immersion in N-methylpyrrolidone (NMP) at 90 °C for 1 hour. The glass transition temperature (Tg) for films cured with a low e-beam dose is slightly higher than, or nearly the same as, the (Tg) for thermally-cured films (∼ 270 °C). However, the Tg for films cured with a high e-beam dose exceeds 400 °C. Dielectric constants of e-beam cured films and thermally cured films are nearly the same. FTIR spectra of FLARE™ films obtained before and after e-beam exposure suggest that e-beam curing does not induce any significant change in the chemical structure. Increased solvent resistance, higher Tg, and low dielectric constant are properties that make this e-beam cured poly(arylene ether) film an excellent candidate for interlevel dielectric integration processes.
Thermomechanical Properties of Hydrogen Silsesquioxanes
Authors: Shih W.-Y. , Zhao J.-H. , McKerrow A. J. , Ryan E. T. , Taylor K. J. , Ho P. S.
Published: April 2011

Using Si and GaAs substrates, the coefficient of thermal expansion (CTE) and the bi-axial modulus of thin hydrogen silsesquioxanes (HSQ) films are deduced by means of wafer curvature measurement. The same properties of plasma-enhanced CVD oxide are also reported.
Parylene Copolymers
Authors: Taylor Kelly J. , Eissa Mona , Gaynor Justin F. , Jeng Shin-Puu , Nguyen Hoan
Published: April 2011

Improvements in the properties of Parylene may enable their use in high performance integrated circuits. Parylenes are a class of polymers formed by chemical vapor deposition which nearly meet the high standards of the low-k triumvirate, namely, 1) adhesion, particularly to SiO2, 2) thermal stability above 400 Celsius, and 3) permittivity less than 2.7. Parylene-N has been incorporated into both aluminum-1 and copper-2 based metallization schemes, however, improvements in the adhesion and thermal stability are still needed to simplify and increase the robustness of the integration schemes. Additionally, a reduction in the permittivity would be beneficial from both device performance and extendibility points-of-view. We have synthesized various Parylene-N-based copolymers with improved adhesion, thermal stability, and permittivity. We discovered that a copolymer of tetravinyl-tetramethyl-cyclotetrasiloxane and Parylene-N has a permittivity of close to 2.1 and both the adhesion to SiQ2 and thermal stability are measurably improved compared to the homopolymer.
Chemical Vapor Deposited Teflon Amorphous Fluoropolymer as an Interlevel Dielectric Material for Low Power Integrated Circuits
Authors: Sharangpani R. , Singh R.
Published: April 2011

The development of materials with dielectric constant (K) less than SiO2(K=3.9) is essential to meet the stringent speed, power dissipation and crosstalk requirements that are driving the low power integrated circuit (IC) paradigm. Both the low K dielectric and the processing methodology used for it should satisfy several important criteria before the technique can be accepted in future mainstream low power IC manufacturing. We had reported earlier a chemical vapor deposition (CVD) technique for the deposition of DuPont's Teflon amorphous fluoropolymer 1600 (bulk K=1.93) using the principle of direct liquid injection. The processing was carried out with and without an ultra violet (UV) light source in a computerized rapid isothermal processing (RIP) system.

Recently, we have extensively characterized the films and examined the suitability of our technique in light of some of the requirements of the future IC industry. Our results indicate that the processed films exceed several of the established dielectric performance standards outlined in recent roadmaps for sub 0.25 μm ICs. The film properties were improved when the UV source was used during processing. CVD processed films in general demonstrated significant improvements in terms of manufacturability, throughput, cost, and dielectric properties over the same films processed by alternate techniques.
Adhesion and Dielectric Strength of Ultra-Low Dielectric Constant PTFE Thin Films
Authors: Rosenmaver C.T. , Bartz J. W. , Hammes J.
Published: April 2011

Previous work has demonstrated the potential of polytetrafluoroethylene (PTFE) thin films for ULSI applications. The films are deposited from PTFE nanoemulsions. They have an ultra-low dielectric constant of 1.7 to 2.0, a leakage current of less than 1.0 nA/cm2 @ 0.2 MV/cm and a dielectric strength of from 0.5 to 2.4 MV/cm. They are thermally stable (isothermal weight loss < 1.0 %/hr at 450 °C), uniform (thickness standard deviation < 2%), and have excellent gap-fill properties (viscosity of 1.55 cP and surface tension of 18 mN/m). The films are inert with respect to all known semiconductor process chemicals, yet they are easily etched in an oxygen plasma.

This paper discusses the processing technology that has been developed to process PTFE films with these properties. Specifically, it addresses two recent discoveries: 1) Good adhesion of spin-coated PTFE to SiO2 surfaces; and 2) high dielectric strength of PTFE thin films spin-coat deposited onto rigid substrates. The adhesion-promoting and thermal treatments necessary to produce these properties are detailed. Stud pull test results and test results from metal-insulator-metal (MIM) capacitor structures are given.
Thermal Stability Study of the Interconnect System with Fluorinated Silicate Glass as IMD Layers
Authors: Li Weidan , Catabay Wilbur
Published: April 2011

While fluorinated silicate glass (FSG) has been proposed for low k inter-metal dielectric (IMD) applications in a multi-level interconnect system either as the only IMD material, or as one of the materials for a multi-layer IMD system, thermal stability of the FSG film and its impact on device reliability remain a concern for this application. In this study, SIMS, SEM, and optical microscope analyses were carried out to evaluate the thermal stability of the FSG films and the possible reactions between FSG and metals. It was observed that at elevated temperatures fluorine tends to diffuse into an undoped oxide film rather than be desorbed. The data indicate that F diffuses 3.5 times faster in a silicon oxide film than in a silicon nitride film. Sub-half micron devices were processed with FSG as IMD layers. The devices were tested using an intensive thermal stability test methodology. A TiSi2 reaction with F which diffused from the FSG film was observed under optical microscopy. This reaction caused TiSi2 delamination. Electrical characterization of devices was performed before and after the thermal stability test. Although the device performance did not change greatly, the reaction certainly affects the long term device reliability (vide infra). Barrier materials were investigated to solve the F diffusion problem. With the proper diffusion barrier, the problem of the fluorine reaction with TiSi2 and subsequent metal blistering was eliminated.
Thermal Stresses, Interfacial Reactions and Microstructures of Al/Ti and Al/TiN Thin Films Encapsulated by SiOF
Authors: Tseng Wei-Tsu , Chen Li-Wen , Tu G.-C.
Published: April 2011

Variations in stress and grain size of Ti- and TiN- capped Al thin films passivated by fluorinated silicon dioxide (SiOF) during repetitive thermal cycling are investigated. The amount of stress relaxation, elastic and plastic behavior of these thin film structures are compared. Ti and TiN cap layers strengthen the single Al film significantly while the presence of SiOF induces plastic deformation of metal layers. Less grain growth is associated with a dielectric passivated Al film. The penetration of fluorine into Al upon annealing can be reduced by a TiN barrier layer.
Recent Advances in Low K Polymeric Materials
Authors: Carter K. R.
Published: April 2011

As microelectronic device dimensions decrease and functionality density increases, a change in interconnect materials, both conductors and insulators must change from currently used materials. To this end, we are actively in search of low dielectric constant materials that can be integrated into integrated circuit production. The greatest limiting factor in materials qualification are the stringent IC processing conditions (thermal stability, resistance to chemical/mechanical treatments). Current specifications for back-end-of-the-line (BEOL) thin film insulators call for materials with dielectric constants of 3.0–3.5 and turn of the century CMOS devices may require materials with dielectric constants approaching 2.0. While there are a number of possible candidates for current uses, the list of usable materials with dielectric constants <3.0 is very limited. Future low K candidates being examined include fluorinated polyimides and porous materials.
Temperature and Moisture Dependence of Dielectric Constant for Bulk Silica Aerogels
Authors: Hrubesh L.W. , Buckley S. R.
Published: April 2011

The dielectric constants of silica aerogels are among the lowest measured for any solid material. The silica aerogels also exhibit low thermal expansion and are thermally stable to temperatures exceeding 500°C. However, due to the open porosity and large surface areas for aerogels, their dielectric constants are strongly affected by moisture and temperature. This paper presents data for the dielectric constants of silica aerogels as a function of moisture content at 25 °C, and as a function of temperature, for temperatures in the range from 25 °C to 450°C. Dielectric constant data are also given for silica aerogels that are heat treated in dry nitrogen at 500°C, then cooled to 25°C for measurements in dry air. All measurements are made on bulk aerogel spheres at 22GHz microwave frequency, using a cavity perturbation method. The results of the dependence found here for bulk materials can be inferred to apply also to thin films of silica aerogels having similar nano-structures and densities.
The Small Angle Cleavage Technique: An Update
Authors: Walck Scott D. , McCaffrey John P.
Published: April 2011

The Small Angle Cleavage Technique is a relatively simple and inexpensive method of producing superior cross sectional TEM specimens. For speed of preparation, it is unsurpassed. One limitation is that the technique does require the substrate material to cleave or fracture. For this reason, it has been applied almost exclusively to semiconductor materials. Recently, the technique has been extended to other substrates such as glass, silicon carbide, quartz, sapphire, and other hard materials. It is particularly well suited for rapidly examining coatings and thin films very soon after they are deposited. Several procedures have been added or modified to the original technique developed by McCaffrey to simplify the technique. The steps are presented in a detailed pictorial outline form. A method for mounting the cleaved samples utilizing a commercially available grid is presented. In addition, the advantages that the special geometry of the prepared samples have when mounted properly in a double-tilt holder are discussed with respect to the angular range of tilting experiments that are now possible in the TEM.
An Improved Tool for Wedge-Polishing of Materials for Tem
Authors: Shaapur F. , Rimer J.
Published: April 2011

A new and improved commercial version of a tool designed originally for angle-lapping to electron-transparency has been presented in this paper. The new tool commercially known as precision angle lapper (PALTM) was originally developed and introduced in 1995. The improvements incorporated in the PAL design were conceived and implemented mainly as a result of a systematic analysis of the original tool design, the shortcomings and complications encountered during the routine hands-on use of it, requirements for major auxiliary equipment in conjunction with application of the tool and, finally, the input from other users of the tool. The basis for each added and/or improved feature of the PAL has been individually discussed and the resulting advantages have been reviewed.
A New Tripod Polisher Method For Preparing Tem Specimens of Particles and Fibers
Authors: Arlderson Ron , Klepeis Stanley J.
Published: April 2011

A tripod polisher method that extends the use of the tool to the preparation of difficult particulate and fiber specimens, sufficiently thin to permit direct TEM examination with minimal or no ion milling, is detailed. The specimen is surrounded with Si in order to take advantage of the colour changes displayed by thin Si to assess the thickness of the specimen during preparation.
Preparation of Cross-Section Tem Specimens of Semiconductors Containing Tungsten Interconnects Using Chemical Mechanical Polishing and Chemically Assisted ion Beam Milling, and Use of Afm to Evaluate the Success of These Procedures
Authors: Jamison Robert , Mardinly John , Susnitzky David , Duan Jian , Matos Carmen , Darknell Sharon
Published: April 2011

TEM of semiconductors containing tungsten interconnects is hampered by the problem of tungsten being intrinsically opaque to the electron beam, and at the same time typically being much thicker than the rest of the specimen. This work describes a technique which can predictably and reproducibly thin tungsten to electron transparency using chemical mechanical polishing (CMP). Chemically-assisted ion beam etching (CAIBE) techniques were also investigated, but found to be of little benefit. The key to development and evaluation of these methods was the AFM.
The Use of a Cold Gas Plasma for the Final Processing of Contamination-Free Tem Specimens
Authors: Fischione P. E. , Ringnada J. , Feng Y. , Krekels T. , Hayies M , Colijn H. O. , Mills M J. , Wiezorek J. M
Published: April 2011

The issue of specimen contamination becomes more important at a rate proportional to the use of high-brightness electron source Transmission Electron Microscopes (TMM). The trend in the transmission electron microscopy of materials science specimens is to use higher-voltage microscopes incorporating field emission gun technology [1]. These FEG TEMs combine smaller electron probes with increased beam current, allowing high resolution specimen imaging and enhanced analytical data collection. This is of particular importance for semiconductor specimens which demand fine-probe microanalyis.
Preparation of Multilayered Materials in Cross-Section for in-Situ Tem Tensile Deformation Studies
Authors: Wall M. A. , Barbee T. W.
Published: April 2011

The success of in-situ transmission electron microscopy experimentation is often dictated by proper specimen preparation. We report here a novel technique permitting the production of crosssectioned tensile specimens of multilayered films for in-situ deformation studies. Of primary importance in the development of this technique is the production of an electron transparent microgauge section using focused ion beam technology. This micro-gauge section predetermines the position at which plastic deformation is initiated; crack nucleation, growth and failure are then subsequently observed.
Rocking-Angle Ion-Milling of Cross-Sectional Samples for Transmission Electron Microscopy of Multi-Layer Systems
Authors: Lee Jeong Soo , Kim Hyun Ha , Jeong Young Woo
Published: April 2011

The cross-sectional transmission electron microscopy (TEM) specimens of Pt/Ti/SiO2/Si, RuO2/SiO2/Si, W/TiN/SiO2/Si, (Pb,La)TiO3/Pt/MgO, Bi4Ti3O12/Lal-xCaxMnO3/MgO, and GaN/Al2O3 were successfully made by the rocking-angle ion-milling technique. The differential thinning problems could be effectively mitigated when the rocking-angle and the ion-beam incidence angle were optimized for each heterostructure. It was found that the sputtering yield ratio between the layer milled most quickly and the layer milled most slowly is one of the important factors which determine the optimum rocking-angle ion-milling condition. The atomic force microscopy study on the surface topography of the cross-sectional Pt/Ti/SiO2/Si TEM sample after ion-milling provided quantitative information about the effects of the rocking-angle variation. A parameter which is the ratio between the layer with a minimum electron transparency and the layer with a maximum electron transparency was suggested.
Eutectic Growth in Unidirectionally Solidified Fe-Cr-Ni Alloy
Authors: Okane Toshimitsu , Umeda Takateru
Published: April 2011

In this report, transition of solidified phases for directionally solidified Fe-Cr-Ni alloys has been investigated in low growth rate range by using Bridgman type furnace. The ferrite-austenite eutectic growth has been confirmed like a plane front growth of ferrite single phase under low growth rate condition. The transition velocity between eutectic and ferrite cell growth has a good agreement with the result of calculation based on the phase selection criterion and the interface temperature calculation for ferrite, austenite and eutectic phases. These results show that the phase prediction by calculating interface temperature can be applied not only to competitive growth between single phases like peritectic systems, but also to eutectic systems. Furthermore, under the condition of eutectic coupled growth to be occurred in steady state, the changes of solidified phases and their morphologies in the initial transient are discussed.
Time-Dependent Nucleation in Partitioning Systems
Authors: Kelton K. F. , Narayan K. Lakshmi
Published: April 2011

Nucleation in multi-component systems is poorly understood, particularly when the rates of long-range diffusion are comparable with the rates of attachment at the cluster interface. For illustration, measurements of the time-dependent nucleation rates in silicate and metallic glasses are discussed. A new model for nucleation in partitioning systems, which explains many of devitrification microstructural features in bulk metallic glasses, is presented.
Energetics of Stable and Metastable Low Temperature Iron Oxides and Oxyhydroxides
Authors: Laberty Ch. , Navrotsky A.
Published: April 2011

Iron oxides and oxyhydroxides are widespread in nature. Understanding the thermodynamic properties of the transformation in the iron oxide/hydroxide system permits the characterization of numerous geochemical processes including weathering, soil chemistry, and diagenesis in continental and oceanic environments. The aim of this study is to measure the energetics of a series of metastable oxides and oxyhydroxides in order to determine the effects of polymorphism, of oxidation state and of hydration. High temperature solution calorimetry using sodium molybdate as a solvent and transposed temperature drop calorimetry at 979 K were used.

Enthalpies of formation from the elements of the metastable iron oxides and oxyhydroxides were calculated from the measured values of the enthalpies of drop solution. The experiments allow an estimate of the enthalpy of formation from the elements of γFe2O3(−817.4 ± 1.2 kJ/mol for sample with tetragonal symmetry and −816.9 ± 1.2 kJ/mol for sample with cubic symmetry) and β-FeOOH (−561.3 ± 3.1 kJ/mol) which are currently unavailable in the literature.

The stability of the structure depends mostly on the degree of hydration and on the average oxidation state of iron. It depends less strongly on the topology of the structure itself and of the tunnel anion.
Refinement of Size Distributions for Primary Crystallizations
Authors: Pineda E. , Pradell T. , Crespo D. , Clavaguera N. , ZHU J. , Clavaguera-Mora M. T.
Published: April 2011

The microstructure developed in primary crystallizations is studied under realistic conditions. The primary crystallization of an amorphous alloy is modeled by considering the thermodynamics of a metastable phase transition and the kinetics of nucleation and crystal growth under isothermal annealing. A realistic growth rate, including an interface controlled growth at the beginning of the growth of each single grain and diffusion controlled growth process with soft impingement afterwards is considered. The reduction in the nucleation rate due to the compositional change in the remaining amorphous matrix is also taken into account. The microstructures developed during the transformation are obtained by using the Populational KJMA method, from the above thermodynamic and kinetic factors. Experimental data of transformed fraction, grain density, average grain size, grain size distribution and other related parameters obtained from annealed metallic glasses are modeled.
Coarsening of B2 Ordered Domains by Monte Carlo Simulations
Authors: Floc'h D. Le , Athènes M. , Bellon P.
Published: April 2011

We present results concerning the study of growth and coarsening kinetics of ordered domains in a binary alloy exhibiting a B2 ordering at the stoichiometric composition. This study has been performed within the framework of an atomistic kinetic model based on vacancy migration using Monte Carlo simulations techniques. Contrary to the standard Lifshitz-Allen-Cahn law, it is observed that the coarsening exponent is a function of the annealing temperature, and also of parameters controlling the migration of the vacancy.
Production and Study of Ca/Sn(II) Metastable Fluoride Ion Conductors
Authors: Bell Michael F. , Dénès Georges , Zhu Zhimeng
Published: April 2011

Precipitation reactions from aqueous solutions of calcium nitrate and tin(II) fluoride result in the formation of two metastable phases, depending on the reaction conditions. Crystalline CaSn2F6 and the microcrystalline Ca1-xSnxF2 solid solution are obtained, the latter crystallizing in the cubic fluorite (CaF2) type with total Ca/Sn disorder. Both phases are fluoride ion conductors. Electrical conductivity measurements versus temperature and bulk density measurements show that both phases are far from thermodynamic equilibrium at ambient conditions, and thus are metastable. Both decompose to a mixture of SnF2 and CaF2 at high temperature. In addition, CaSn2F6 is chemically unstable in an aqueous medium, in which it looses SnF2 to give the microcrystalline Ca1-xSnxF2 solid solution.
Ordered Omega Derivatives in (Zr3Al)-Nb Alloys
Authors: Tewari R. , Dey G. K. , Mukhopadhyay P. , Banerjee S. , Bendersky L. A.
Published: April 2011

Various kinds of phase transformations, viz., spinodal decomposition, omega transformation, precipitation reactions and martensitic transformation can be induced in ternary (Zr3Al) -Nb alloys in conditions far removed from equilibrium. Transformation sequences in alloys containing 3% niobium are described and rationalized in terms of some basic tendencies such as phase separation and chemical ordering in the β (bcc) phase and displacive omega and β to α (hcp) transformations. Microstructures of rapidly solidified alloy showed a distribution of cuboidal (D88 phase) particles in the β matrix. The periodic arrangement of these particles along the <100>β directions was indicative of a spinodal transformation which preceded their formation. The β → D88 transformation could be accomplished by the superimposition of three processes, namely, chemical ordering, lattice collapse akin to ω transformation and vacancy ordering. During isothermal aging the D88 phase transformed into the B82 phase. The observed lattice correspondence and transformation morphology suggested that the D88 to B82 structural change involved the replacement of structural vacancies in the former by zirconium atoms without any reconstitution of the lattice. The evolution of the equilibrium Zr3Al (L12 structure) phase during prolonged aging were also studied.
Mechanisms of Layer Structure Formation in Peritectic Alloys
Authors: Mazumder P. , Trivedi R. , Karma A.
Published: April 2011

The mechanisms of layer structure formation in the two phase region of peritectic systems are discussed. Under diffusive growth conditions, a banded structure is predicted within a narrow composition range in the hypoperitectic composition. Experimental studies show the formation of an oscillatory structure in the hyperperitectic region. It is shown that this structure is induced by convection in the melt, and it is a novel structure in which a large single tree-like structure of primary phase is surrounded by the peritectic phase. Basic ideas of convection that lead to this tree-like morphology are described.
Changes in Mass Density and Sound Velocity of Amorphous Pd80Si20by Low Temperature Ion Irradiation
Authors: Schumacher G. , Birtcher R. C. , Renush D. P. , Grimsditch M. , Rehn L. E.
Published: April 2011

Changes in transverse phonon sound velocity were measured during low temperature irradiation of amorphous Pd80Si20with 3.5 MeV krypton ions. The sound velocity decreases as a function of the ion fluence and shows a tendency to saturate at large fluences at a relative change of −4.7%. The changes in sound velocity were used to determine the changes in shear elastic constant and in Debye temperature both of which were in reasonable agreement with the value reported in the literature.
Diffusion-Governed-Asymmetric Growth of Amorphous Layer Under Solid-State Reaction in Ni-Zr Multilayers
Authors: Liu B. X. , Lai W. S.
Published: April 2011

A molecular-dynamics simulation with an n-body potential was performed to study solid-state amorphization in the Ni-Zr system upon annealing at medium temperatures ranging from 300 to 600 °C. The models for simulation were a Zr-Ni-Zr sandwich consisting of both hcp Zr and fcc Ni (001) atomic planes and a bilayer with a thin preset disordered interfacial layer, respectively, for revealing the detailed amorphization process and the growing kinetics of an amorphous layer upon solid-state reaction. Our simulation results demonstrated, for the first time, that the atomic process proceeded through first diffusion, then alloying and eventually amorphization. In other words, amorphization was controlled by a diffusion-limited reaction and the growth kinetics of the amorphous layer followed exactly a t1/2 law. Another interesting finding was that the growing speeds of the amorphous layer exhibited an asymmetric behavior, i.e. the amorphous layer extended faster towards Ni lattice than that directed to Zr side. Besides, it was also found that an initiation of amorphization upon annealing was dependent to the interfacial textures, i.e. amorphization could take place when the interfaces were composed of the more open atomic planes, whereas it was suppressed if the interfaces were constructed with the close-packed planes of both lattices.
Recrystallization of Si-, As- And BF2-Implanted, Bonded SOI
Authors: Tamura M. , Horiuchi M.
Published: April 2011

Conventional and high-resolution cross-sectional TEM observations have been carried out on Si-, As- and BF2-implanted, bonded 100-nm-thick (001) SOI layers having polycrystalline Si (poly-Si) masks followed by annealing at 600°C. Amorphized SOI layers by these ion implantations are recrystallized through lateral solid-phase seeding epitaxy (L-SPE) by single crystal SOI under the poly-Si mask as a seed. The recrystallization of these SOI layers is completed in the order of BF2-, Si- and As-implanted layers by <110>-directed L-SPE, although the recrystallized layers have a high-density of {111}twins due to {111} facet formation at the growth front occurring during the first 30 s of annealing, independent of implanted ions. On the other hand, in the case of <100>-directed L-SPE, the growth of {110} faceted regions progresses after annealing for a few tens of minutes before folded {111} facets are formed, resulting in a good crystal quality region of 0.1∼0.2μm remaining, measured from the mask edge.
Thermal Drag of the Antiphase Domain Boundary Motion
Authors: Umantsev A.
Published: April 2011

Antiphase domain boundary is a region in materials where ordering of atoms changes from one structural variant to another. Influence of the internal energy excess on the dynamics of such boundary is considered in the framework of the Onsager theory of linear response. The internal energy transport entails a temperature hump in the transition region and causes a drag effect. An evolution equation that takes into account the finite thermal conductivity is derived. Experimental setup to reveal the thermal drag is suggested.
Structure, Morphology and Kinetics of the C49 to C54 Phase Transformation In Tisi2 Thin Films
Authors: Bocelli S , Marabelli F. , Iannuzzi M. , Miglio L. , Grimaldi M. G. , LaVia F.
Published: April 2011

A series of fine grained C49 thin films were prepared by depositing Ti films on heated amorphous as well as crystalline silicon substrates.

Rapid thermal processing at temperatures between 700 and 775 °C was used to transform the metastable C49 phase into the stable C54. The evolution of the film structure and morphology during the transformation was investigated by sheet resistance, optical spectroscopy, diffuse reflectance and AFM measurements. One structural model which could account for our data is proposed according to crystallographic information present in the literature.
The Cubic to Hexagonal Phase Transition in Spray Deposited Tin-Doped Indium Oxide Films
Authors: Malik A. , Nunes R. , Martins R.
Published: April 2011

This work's aim is to report for the first time the cubic to hexagonal phase transition in tindoped In2O3 films with a Sn/In atomic ratio of 0.03, fabricated at low temperature and normal pressure from alcoholic solution of InCl3 and SnCI4. The performed X-ray diffraction measurements show a difference between crystallographic symmetry of thin (100 nm) and thick (400 nm) films prepared in the same conditions: the structure of thick films can be related to high pressure In2O3 hexagonal system with a preferred orientation of c-axis parallel to the substrate surface, while thin films present a cubic symmetry with columnar (400) grain orientation. Phase transition nature is connected with non-axial tensile deformation of indium oxide grid due to insertion of chlorine ions in the position of two diagonally opposite oxygen vacancies in In2O3 network.
Pseudo-C11b Phase Formation of Titanium Disilicide During the C49 to C54 Transition
Authors: Smith Patrick L. , Ortega Richard , Brennan Bill
Published: April 2011

The formation of TiSi2 thin films using the SALICIDE process on doped and undoped silicon substrates was studied. XRD TEM, AES, RBS and four probe Rs were used to characterize the material. Unit cell parameters and energetics were determined. Results confirm electrical and chemical signatures consistent with the known C49 conversion to C54. However, XRD indicated a structurally different intermediate phase occurs during the C49 to C54 transformation. Modeling was performed based on C11b structure (14/mmm) type, with the Ti and Si atoms arranged similarly to those in MoSi2. The unit cell was determined to be a = 4.428 Å, b = 4.779 Å, c = 9.078 Å with a Fmmm space group and total pseudo-potential plane wave calculations based on crystallographic simulations of −103.96 ev/Atom.
Point Defects And The B2 To Fcc Transformation In Milled FeRh
Authors: Peng Luke S.-J. , Collins Gary S.
Published: April 2011

Mössbauer measurements were made on FeRh containing 52 atomic percent (at.%) Fe after mechanical milling for different times in a high-energy SPEX 8000 vibrator mill. Hyperfine fields are compared with fields for annealed ferromagnetic (F) samples having the B2 structure in the range 52–58 at.% Fe. For annealed F samples, hyperfine field shifts of -1.66 T and -1.12 T were detected at majority FeFC and minority FeRh probes due to FeRh antisite atoms in, respectively, the first and second atomic shells. Analysis of dipolar fields indicates that the magnetization lies along the <110> direction. The transformation from F B2 phase to a metastable paramagnetic fcc phase was observed that was half complete in 8 minutes. Analysis of spectra for the milled F B2 phase show that a second point defect was produced by milling that induces shifts of +6 T and +8.5 T, respectively, at majority and minority probes. Manyspectra fits were made under different defect models that led to the conclusion that milling produces point defects in the triple-defect configuration: 2 Fe-vacancies and 1 Fe-antisite atom. Defect concentrations were determined and show that the fractional concentration of vacancies on the Fe-sublattice increases linearly with milling time, reaching 3 at.% after 8 minutes, a very large value. The rate of transformation from B2 to fcc phase appears to be independent of the concentrations of point defects in the B2 phase, indicating that the transformation is purely stress-induced, as in a martensite transformation.
Microstructure Evolution in Al-Ag Alloys Under Severe Plastic Deformation
Authors: Haider F. , Voss H.
Published: April 2011

We present results on the microstructure evolution in an A1Ag alloy after plastic deformation under fatigue at different temperatures, strain amplitudes and strain rates. Both the dislocation structure and the precipitate morphology and size distribution were analyzed. At low temperature, particle elongation and fragmentation was observed while at higher temperature an accelerated growth due to vacancy supersaturation was observed.
Superdendrites in Directional Solidification of Polymer-Solvent Mixtures
Authors: Ragnarsson Rolf , Utter Brian , Bodenschatz Eberhard
Published: April 2011

The directional solidification of the transparent binary alloy succinonitrile-poly(ethylene oxide) was studied in an experiment in which solidification speeds of about 2 mm/sec could be reached without loss of the linear temperature gradient. The low diffusivity of the polymer solute allowed the study of the dynamics of rapid solidification using an optical microscope. For both normal and doublonic dendrites we observed a transition to large triangular “superdendrites” above a certain solidification speed and we report measurements of the primary and secondary spacing as a function of the pulling speed. Our measurements suggest that the observed triangular shape is due to a decoupling of primary and secondary growth at large undercooling.
Molecular Dynamics Calculations Of Melting and Fragmentation of Ar and Ag Clusters
Authors: Mazzone A. M.
Published: April 2011

Melting and fragmentation of Ar and Ag clusters, containing from 30 to 500 atoms, have been studied with an isothermal molecular dynamics simulation method using classical forces. The simulations describe either evaporative decay or collisional dissociation. In the first case it has been found that the increase of the temperature leads to a continuous transition from a softening of the bonds to fragmentation and,with a proper scaling of the temperature, the effect is similar in Ar and Ag. During the collisional decay a perceptible fragmentation yield is observed in Ar whereas in Ag the input energy is converted into translational energy and rigid motions.
Materials Characterization on Optically Pumped InGaN/GaN Lasers by Farfield Measurements and Fourier Analysis of the Emission Spectrum
Authors: Hofstetter D. , Thornton R. L. , Romano L. T. , Bour D. P. , Johnson N. M.
Published: April 2011

We report materials characterization on optically pumped InGaN/GaN lasers by farfield and spectral measurements. Through a comparison between measured and calculated farfield data for an In0.15Ga0.85N/In0.05Ga0.95N multi quantum well laser structure with AIGaN cladding layers, we could extract important information about the optical confinement in the transverse direction. The analysis of Fourier-transformed emission spectra of our devices allowed us to make qualitative statements about the material quality in terms of surface pits and cracks. We believe that optical pumping with these supplementary techniques is an important and powerful tool which helps to overcome critical material quality requirements in gallium-nitride.