bluuebunny/crossref_metadata_2025 huggingface dataset:
Probing the Fractal Character of Pore Surfaces in Shale with Adsorption Technique
Authors: Ma Jian , Qi Hao , Wong Po-Zen
Published: April 2011

We report on an adsorption study on two shale samples that have previously been investigated by small-angle neutron scattering (SANS). The scattering data indicate that these samples can be characterized as surface fractals in length from 5 Å to 500 Å, with the fractal dimension D between 2.83 and 2.75. Using the existing models for adsorption on fractal surfaces, the values of D deduced from the adsorption data appear to be consistently lower than the SANS results. We discuss these findings.
Competing Elementary Reactions in a Capillary - Two Reaction Fronts Moving in Opposite Directions
Authors: Park Sung Hyun , Taitelbaum Haim , Kopelman Raoul
Published: April 2011

The behavior of two reaction fronts created in a system of two competing reactions has been investigated using the reaction between xylenol orange (XO) and chromium(III) ion in aqueous solution. Two reaction fronts have been shown to move in opposite directions, which is explained in terms of relative concentrations among three reactant species. This explanation was verified by the observation of only one reaction front for selected different relative concentrations, where both reaction fronts move in unison. As predicted by theory and confirmed by computer simulation, the position (xf) of each reaction front scales as t½, irrespective of the direction of motion.
Effect of Covalently Incorporated Azobenzenes on Dendrimers
Authors: McGrath D. V. , Junge D. M. , Cheng A. , D'Ambruoso G.
Published: April 2011

Several new azobenzene-containing dendritic molecules have been prepared and characterized. The photoresponsive characterization of these dendrimers illustrates the insensitivity of the photochromic behavior of the azobenzene with respect to the nature of the attached dendritic fragment.
Scalings of A + B Reaction Kinetics due to Anisotropic Confinements
Authors: Argyrakis Panos , Ahn Jaewook , Lin Anna , Kopelman Raoul
Published: April 2011

We report on the diffusion-limited A + B reaction in highly anisotropic spaces. In addition to the highly non-classical behavior of the density of reactants predicted for isotropic spaces, we observe a dimensional crossover in A + B → 0 reactions due to the geometrical compactness of the tubular 2- and 3-dimensional spaces (baguettelike structures). For slabs, we find the crossover time Tc. = Wα, which scales as , where a, b and β are given by the earlier and the late time inverse density scalings of ρ− 1 ˜-, ta and ρ−1 - tbWβ, respectively. We also obtain a critical width W, below which the chemical reaction progresses without traversing a 2- or 3-dimensional Ovchinnikov-Zeldovich reaction regime. We find that there exist different hierarchies of dimensionally forced crossovers, depending on the initial conditions and geometric restrictions. Kinetic phase diagrams are employed and exponents are given for the A + B elementary reactions in various euclidean geometries. Monte-Carlo simulations illustrate some of the kinetic hierarchies.
PE-CVD of Fluorocarbon/Silicon Oxide Composite thin Films from TFE and HMDSO
Authors: Shirafuji T. , Hayashi Y. , Nishino S.
Published: April 2011

Fluorocarbon/silicon oxide composite thin films were prepared, expecting higher thermal stability, by mixing hexamethyldisiloxane (HMDSO, (CH 3) 3-Si-O-Si-(CH 3)3) with tetrafluoroethylene (TFE, CF2=CF2) using an RF( 13.56 MHz) PE-CVD method for the purpose of application to low-k IMDs. Structure of the deposited films was investigated by XPS and FT-IR. Film composition can be changed gradually from fluorinated carbon to organic siloxane by changing the HMDSO mixing ratio. The films possessed dielectric constants less than 2.5 for HMDSO mixing ratios less than 10%. Thermal treatment of the films revealed that C-Fn, Si-O-Si, Si-(CH3)n and Si-(CH2)n-Si bonds were stable to 400°C, but C-Hn bonds were not. In situ gas-phase FT-IR spectroscopy was performed on the TFE/HMDSO plasma to help determine reaction mechanisms.
Magnetron Sputtered Ti-Basis Hard Material Coatings on Thermoplastic Polymers for Applications in Particle Sensitive Environments
Authors: Lugscheider E. , Barwulf S. , Barimani C. , Riester M. , Hilgers H.
Published: April 2011

Even under demanding environments, like clean rooms, polymers are already used in different-ranges of applications. The wear and particle generation within a specific particle size even under-mechanical stress is a limiting factor. So it was the aim to develop an innovative material-concept, that enables to apply a thermoplastic polymer coated with a thin hard material (thickness-up to 2.5 gm), which also prevents for electrostatical discharges and is usable for complex-bodies. Therefore it was necessary to improve the wear resistance and the adherence between the-polymer and the coating. To take also economic aspects into consideration a two step production-process sequence was required, consisting of the injection moulding process and then the plasma-deposition process including a plasma pre-treatment. In this investigation, poly(butyleneterephthalate)-(PBT) and poly(amide) 6.6 (PA) and polycarbonate (PC) were chosen as substrate-material. The coating materials used, which were mainly deposited by Magnetron Sputter Ion-Plating (MSIP), were on titanium basis (Ti-N). To get detailed chemical information about the-coatings and the interfacial region they were analyzed by X-Ray Photoelectron Spectroscopy-(XPS), additionally Secondary Ion Mass Spectrometry (SIMS) experiments were carried out to-confirm the results. The process parameter's influence on the microstructure, which extend from-amorphous to columnar (crystalline), and the film thickness were analyzed by SEM. It will be-shown and discussed, that it is possible to improve the coating's adherence by plasmapretreatment-as well as to reduce the particle generation after a suitable etching and coating process.
Gas Phase and Particle Diagnostic of Hmdso Plasmas by Infrared Absorption Spectroscopy
Authors: Magni D. , Deschenaux C.H. , Courteille C. , Howling A. A. , Hollenstein C.H. , Fayet P.
Published: April 2011

FTIR spectroscopy has been applied to a radio-frequency discharge in hexamethyldisiloxane (HMDSO) diluted with oxygen and helium, as typically used for industrial SiOx, deposition. By measuring the infrared absorption of the HMDSO molecule, the gas consumption during processing can be monitored, allowing process optimization. Additional information on various infrared active radicals formed within the plasma, such as CO, CO2 and aldehydes, helps to elucidate the plasma chemistry in HMDSO plasmas. Besides information on the formation of gaseous components in the plasma, infrared transmission spectra give at the same time important data on the nature of the particle contamination.
Grain Boundary Chemical Analysis Using Intense Electron Beams
Authors: Shang P. , Keyse R. , Jones I. P , Smallman R. E.
Published: April 2011

Scanning Transmission Electron Microscope (STEM) Energy Dispersive X-Ray analysis (EDX) linescans and mapping have been used to examine the large angle grain boundary chemistry of Ni-rich Ni3AI both with and without boron. The results show that the Al content is reduced while the Ni content is unchanged at the grain boundaries in all these alloys, with the percentage of reduction of Al at the grain boundaries decreasing as boron concentration increases. This is ascribed to differential surface sputtering of the lighter Al atoms.
A Dislocation Constriction, Pinning Point Model for the Flow Stress Anomaly in Iron Aluminides
Authors: Morris David G.
Published: April 2011

Iron aluminides with compositions from Fe3A1 to FeAl show an anomalous stress rise at temperatures about 600–800K. Many models have been suggested to explain this behaviour, with the suggestion of hardening by vacancies presently receiving much attention. An alternative model is suggested here, valid for those alloys where the simultaneous reduction of DO3order does not interfere, based on the density of constrictions produced on mobile <111> superdislocations and their subsequent pinning by decomposition or by their cross slip to produce jogs. The exponential increase in stress with temperature can be related to the pinning point density and the absolute values of strengthening correspond well with those predicted by this model. The orientation dependence of the stress anomaly and the tension-compression asymmetry can be related to the role of shear stresses in assisting constriction of the dislocation partials by modifying the core configuration and by assisting the expansion of the new, decomposed dislocations.
Atypical Defects in a B2 Fe-40A1–0.7C-0.5B Alloy
Authors: Pang L. , Kumar K. S.
Published: April 2011

The nature of defects in a quaternary Fe-40A1–0.7C-0.5B alloy was examined by transmissionelectron microscopy (TEM) techniques including weak beam microscopy and z-contrast imaging.Complex {001} stacking faults were observed in certain conditions in these alloys that were not previouslynoted in a ternary Fe-40A1–0.6C alloy. These faults exhibit a 1/2<001> displacement vectorthat lies in the plane of the fault and structurally misses an aluminum layer. Six variants of this faulttype are present. These faults are absent in brine-quenched and furnace-cooled alloys, but are readilyobserved in the air-cooled condition. In addition to the usual <111> superdislocations that are APBdissociatedinto 1/2<111> superpartials, dissociated <100> dislocations (into two 1/2< 100> partials)are also observed under certain conditions. Quenched and aged alloys show dissociated <001> loops.The absence of such defects in the B-free alloy and following certain heat treatments in the B-containingalloy, suggests that boron may be segregating to the cube planes and lowering the interfacialenergy on these planes. The presence of dissociated <001> loops in the quenched and aged alloy alsosuggests the formation of B-vacancy complexes that coalesce during aging, forming such dissociatedloops.
Mechanical Anisotropy of a Gamma Titanium Aluminide Alloy After Hot Extrusion
Authors: Oehring M. , Lorenz U. , Niefanger R. , Appel F , Brokmeier H.-G. , Wagner R. , Clemens H. , Eberhardt N.
Published: April 2011

By hot extrusion below and above the α transus temperature equiaxed and predominantly lamellar microstructures were obtained in a Ti aluminide alloy. In order to examine a possible orientation dependence of mechanical properties the flow stress, the activation parameters of plastic deformation and the fracture toughness were determined parallel and perpendicular to the extrusion direction at room temperature and 700 °C. The observed anisotropy in these properties may be mainly attributed to anisotropies in the microstructures, in particular to a preferential alignment of lamellae in lamellar microstructures.
Physical and Mechanical Properties of Two-Phase Zr-Cr-Mn Alloys
Authors: Goldberg A. , Luzzi D. E.
Published: April 2011

The Zr-Cr-Mn system is used to explore the effect of a lowered SFE on the room temperature mechanical properties of a Laves phase using elements of similar atomic size. The ternary Zr-Cr-Mn diagram in the region from 0 to 12 at. % Mn is first determined and it is shown that Mn substitutes only for Cr in the Laves phase. TEM analysis of the density of stacking fault energy related defects such as annealing twins indicates that Mn substitution for Cr in ZrCr2 lowers the SFE of the cubic Laves phase. Mechanical testing of the two phase alloys is used to explore the effects of Mn content and the volume fraction of each phase on the ductility and fracture behavior in compression. It is found that the mechanical properties are well-described by a model incorporating solid solution strengthening in a ductile-brittle two phase alloy.
Annealing of Quenched Fe-Al Alloys With/Without B And Ti
Authors: Yang Y. , Baker I.
Published: April 2011

Fe-40A1, Fe-40A1–0.12B and Fe-40A1–5Ti were annealed at a variety of temperatures, water quenched to obtain different vacancy concentrations, and heated at 10 K/min to 973K in a differential scanning calorimeter. Either one or two exothermic peaks were observed, at 533–613K and 743–933K, for all the alloys, while an additional exothermic peak was observed at 653K-693K for Fe-40A1–5Ti. All the peaks shifted to lower temperature with increasing quenching temperature. It is shown that the highest temperature exothermic peak is associated with the annihilation of thermal vacancies. Analysis of this peak as a function of temperature yields vacancy formation enthalpies of 102±15kJ/mol, 104±15 kJ/mol and 81±15 kJ/mol for Fe-40A1, Fe-40A1–0.12B and Fe-40A1–5Ti, respectively. The lower temperature exothermic peaks may arise from vacancy rearrangement.
Structure and Mechanical Properties of the Engine Valves with Intermetallic Disk
Authors: Kodess B. N. , Teterin G. P. , Kommel L. A. , Ovcharov V. K.
Published: April 2011

The bimetallic valves were produced using a new technique, IFFM (Impact Fused-Forging Modeling). Distribution of the alloy components as well as phase composition across the valve section was obtained by means of energy-dispersive analysis and X-ray diffraction. Optic and electron microscopy research of macro- and microstructure was conducted. High quality of the joint between the sintermetallic (TiAl) head and the titanium (VT-9 and VT-6 alloys) stem was demonstrated. As a result of the contact of the stem with the semi-solid intermetallics at the temperature above Tc, a polymorphous transformation was obtained in the upper part of the Ti-based stem. The globular microstructure in the intermetallic head in the area near to the joint of the two alloys was achieved. The results proved that the process allows production of complex shaped parts based on advanced alloys of high quality, featuring extra wear-resistance and strength.
Observations of Orientation Dependent Creep of Ni3AI
Authors: Knobloch Carola , Glock Karin , Glatzel Uwe
Published: April 2011

The influence of crystal orientation on the high temperature creep behavior of Ni3(Al Ti Ta) was investigated by tensile creep testing under a constant load at a temperature of 1123K. The single crystals were oriented close to [001], [011], [111], [557] and [012]. The results show an increasing stationary creep rate from [111] over [011] to [001]. The evolution of the microstructure during creep deformation was studied, using transmission electron microscopy (TEM). Only few systems are active in the primary regime, whereas several slip systems operate in the secondary stage. Habit planes of dislocation pairs separated by an antiphase boundary were examined and compared with anisotropic elastic calculations, explaining the good creep response of [111] oriented single crystals.
The Katz-Gratias-De Boissieu-Elser Model Applied To The Surface Of Icosahedral A1pdMn
Authors: Papadopolos Z. , Kramer P. , Kasner G. , Burgler D. E.
Published: April 2011

The Katz-Gratias-de Boissieu-Elser (KGdeBE) model for the icosahedral quasicrystals i-AlFeCu and i-AlPdMn is studied and applied to the surface structure of i-AlPdMn.
Neutron Scattering Study Of Antiferromagnetic Correlations In The Zn-Mg-Ho Icosahedral Quasicrystal
Authors: Sato Taku J. , Takakura Hiroyuki , Tsai An Pang , Shibata Kaoru , Ohoyama Kenji , Andersen Ken H.
Published: April 2011

Magnetism in the Zn-Mg-Ho icosahedral quasicrystal has been studied by neutron scattering. Powder samples of the icosahedral and related crystalline phases were reexamined to clarify the origin of the previously-reported long-range magnetic order [Charrier et al., Phys. Rev. Lett. 78 (1997) 4637]. The long range order was found to originate from the related crystalline phase, which is a contaminant in the previously-used samples. Whereas for high-quality icosahedral phase, we could detect only magnetic diffuse scattering. This apparently shows the absence of the long range order in the icosahedral phase. The diffuse scattering was studied in detail by using a single quasicrystalline sample. It was found that the diffuse scattering appears as satellites from intense nuclear Bragg reflections. This indicates that corresponding spin correlations can be regarded as developed between spins on the six-dimensional virtual hypercubic lattice. A magnetic modulation vector for the correlations is proposed.
Ising Model Simulation Of Magnetic Structures IN A Zn-Mg-Ho Structure Model
Authors: Matsuo S. , Ishimasa T. , Nakano H.
Published: April 2011

Simulated annealing calculations were performed for Ising spins on Ho sites under Ruderman-Kittel-Kasuya-Yosida-like alternating exchange interactions for an icosahedral Zn-Mg-Ho structure model with intent to investigate the magnetic structures at low temperatures. Magnetic structures were analyzed by means of a Patterson function and diffraction patterns arising from spin-dependent scattering amplitudes. The diffraction patterns from the magnetic structure consist of spots at low temperatures in the case of an antiferromagnetic interaction for the shortest distance (3.37 Å) and a ferromagnetic interaction for the second shortest distance (5.46 Å). The Patterson maps indicate a long-range antiferromagnetic correlation. These facts mean that a long-range ordered magnetic structure is realized at low temperatures. The contrast of the diffraction patterns is different from the patterns arising from the spin-independent scattering amplitudes from the Ho sites. A reversed sign interaction, ferromagnetic for the shortest distance and antiferromagnetic for the second shortest distance, results in broad intensity minima in the magnetic diffraction at the positions of strong spots in the spin-independent diffraction by lattice sites. It corresponds to the degradation of the long-range correlation.
Dry Sliding Of Polygrained Quasicrystalline And Crystalline Al-Cu-Fe Alloys
Authors: Sordelet D. J. , Kim J. S. , Besser M. F.
Published: April 2011

Dry sliding friction and wear experiments were performed with pin-on-disc techniques using WC and brass pins in contact with quasicrystalline (Al65Cu23Fe12) and crystalline (Al50Cu35Fe15and Al70Cu20Fe10) discs, which were prepared by powder metallurgy routes. The contact loads (1, 5 and 10 N) used in this study produced similar coefficients of friction 0.3-0.4 for the Al65Cu23Fe12and Al50Cu35Fe15phases. These values are higher than previously reported for quasicrystalline and related crystalline phases. Possible reasons for these differences are presented. The contrasting wear behavior between different pins and discs is discussed in terms of contact area, oxidation, material transfer mechanisms and fracture characteristics.
Potential Of Quasicrystals And Quasicrystalline Approximants For Utilization In Small Scale Thermoelectric Refrigeration And Power Generation Applications
Authors: Trrit Terry M. , Pope A. L. , Chernikov M. , Feuerbacher M. , Legault S. , Gagnon R. , Strom-Olsen J.
Published: April 2011

We have identified quasicrystals and quasicrystalline approximants as potential candidates for small scale thermoelectric power generation and refrigeration applications. A number of quasicrystalline systems have been investigated, however, the focus in this paper will be on the ALPdMn (typically Al70Pd20Mn10) system. Currently, we are systematically investigating the electrical and thermal transport properties of the AlPdMn quasicrystalline system in relation to differing sample composition, systematic addition of impurities, and different annealing conditions. Several different preparation techniques have been employed in order to determine optimal techniques for maximizing the thermal and electrical properties of this quasicrystalline system for possible thermoelectric applications. Resistivity and thermopower have been performed over a temperature range between 5K and 320K. Thermal conductivity measurements have been performed over a temperature range between 20K and 300K. In the pure, single phase nominally Al70Pd20Mn10 we have observed thermopower values as high as +85 μV/K around room temperature with resistivity values of 1.5 mΩ-cm. Thermal conductivity measurements yield values less than 3 W/m-K. We will discuss how these properties are affected by the parameters we have varied and the trends we have observed so far. We will discuss the future investigations of the electrical and thermal transport properties of quasicrystals in relation to potential thermoelectric applications.
Diffusion In Icosahedral AI-Pd-Mn Quasicrystals
Authors: Mehrer H. , Galler R.
Published: April 2011

In this paper radiotracer diffusion studies from our laboratory on monocrystals of icosahedral quasicrystalline Al-Pd-Mn (i-AlPdMn) are summarized. Diffusion of 65Zn, 54Mn, and 59Fe has been investigated as function of temperature and in the cases of 5 4Mn and 65Zn also as function of hydrostatic pressure. Diffusion of 65Zn was studied to ‘simulate’ Al diffusion. Over a very wide temperature range no deviation from Arrhenius-behaviour is found. Some preliminary results of 114m In diffusion are also reported. The diffusivities in i-AlPdMn reveal parallels to foreign atom diffusion in Al suggesting a vacancy-type mechanism of diffusion for i-AlPdMn. Signs and magnitudes of the activation volumes of +0.67 Ω (Ω = mean atomic volume) for 54Mn and of +0.74 Ω for 65Zn diffusion in Al-Pd-Mn favour a vacancy mechanism as well.

Our results will be discussed together with diffusion studies on i-AlPdMn performed by other groups. The results of Nakajima and coworkers on Mn, Ge, Co and Cr diffusion and the results of Frank and coworkers on Pd and Au diffusion in the high-temperature regime are consistent with the above mentioned conclusion. For the low temperature regime of Pd and Au diffusion the suggested possibility of a phason-related mechanism will be discussed.
Phase Diagrams And Approximants
Authors: Quiquandon M. , Calvayrac Y. , Quivy A. , Faudot F. , Gratias D.
Published: April 2011

The controled growth of large single grain of quasicrystalline phase in metallic alloys is a difficult task that requires a detailled knowledge of the corresponding phase diagram. We discuss the metallurgical specificities of the ternary systems AlCuFe and AlPdMn with respect to single icosahedral grain elaboration. We show that adding a few percents of Silicon in the AlCuFe system leads to stabilize two low order cubic approximants one, α, based on Bergman clusters with a parent F-type icosahedral phase and the other, α', based on Mackay clusters with a parent P-type icosahedral phase. A section of this quaternary phase diagram at constant Si content shows that these cubic phases have no common stability region but are located on opposite sides of an orthorhombic phase that is expected to be a complex synthetic structure mixing both Mackay and Bergman type atomic clusters.
Photoconductivity of Discotic Liquid Crystals Derived from A Long-Chain Tetraphenylporphyrin
Authors: Shimizu Y. , Monobe H. , Mima S. , Higashiyama T. , Fuchita T. , Sugino T.
Published: April 2011

Photoconductivity of a mesogenic tetraphenylporphyrin (TPP) is shown in relation to the mesomorphic phase transition behavior. The TPP mesogen shows two types of mesophases having smectic-like order (lamellar mesophases : DL and DLC phases named in this work) and the photocurrent changes stepwise at the phase transitions with non-Arrhenius dependence whilst the darkcurrent tends to be Arrhenius. The hole mobility was measured for the random domain cell and was found to be faster than 10−4 cm2v−1sec−1 in the mesophases. The cell used for the photocurrent measurements was a sandwich-type one using two ITO glass slides as electrtodes and show rectification behavior for the crystal and the low-temperature mesophase (DLC) in contrast to non-rectification of photocurrent in the high-temperature mesophase (DL). These properties of charge carrier migration as an electronic process are profoundly related to molecular order as well as molecular motions in mesophase.
Study of Electrochemical Deposition of Copper and Microstructure Evolution in Fine Lines
Authors: Grunow Stephan , Diatezua Deda , Seo Soon-Cheon , Stoner Timothy , KaloyerosI Alain E.
Published: April 2011

As computer chip technologies evolve from aluminum-based metallization schemes to their copper-based counterparts, Electrochemical Deposition (ECD) is emerging as a viable deposition technique for copper (Cu) interconnects. This paper presents the results of a first-pass study to examine the underlying mechanisms that control ECD Cu nucleation, growth kinetics, and post-deposition microstructure evolution (self-annealing), leading to the development and optimization of an ECD Cu process recipe for sub-quarter-micron device generations. The influence of bath composition, current waveform, type and texture of Cu seed layer, and device feature size (scaling effect) on the evolution of film texture, morphology, electrical properties, and fill characteristics was investigated using a manufacturing-worthy ReynoldsTech 8″ wafer plating tool. Resulting films were analyzed by X-ray Diffraction (XRD), four-point resistivity probe, Focused-Ion-Beam Scanning Electron Microscopy (FIB-SEM), and Atomic Force Microscopy (AFM). These investigations identified an optimized process window for the complete fill of aggressive device structures with pure Cu with resistivity ∼ 2.0 μΩ-cm and smooth surface morphology.
The Influence of Patterning in Co And Co/Pd Multilayer Structures
Authors: Borca C. N. , Cheng Rui-Hua , Dowben P. A.
Published: April 2011

We are studying ferromagnetic films of cobalt and cobalt - palladium heterostructures fabricated by laser assisted chemical deposition from organometalic compounds. We have developed this one-step deposition technique sufficiently to deposit pure metal features with excellent spatial resolution and in multilayer geometries. From the comparison between the continuous and patterned films we can conclude that the patterning of the films into arrays of discrete micron-scale features has a great influence on the magnetic properties of the films.
Role of Film Hardness on the Polish Rates of Metal Thin Films
Authors: Ramarajana S. , Li Y. , Hariharaputhiran M. , Her Y.S. , Babu S.V.
Published: April 2011

Nanoindentation techniques were used to determine the hardness of Cu, Ta & W metal discs and thin films on silicon substrates as a function of load or indentation depth. Cu films exposed to oxidizing solutions containing H202 exhibited a higher hardness at the surface while no such change was observed for W exposed to ferric nitrate. The implication of these measurements and their relationship to chemical-mechanical polishing rates are discussed.
Electrical Characterization of Slurry Particles and their Interactions with Wafer Surfaces
Authors: Park Jin-Goo , Lee Sang-Ho , Kim Hyoung-Gyun
Published: April 2011

The purpose of this study was to explore the interaction between slurry particles and wafer surfaces by the measurements of their zeta potentials. The zeta potentials of slurry particles such as fumed and colloidal silica, alumina, ceria and MnO2 and substrates such as silicon, TEOS, W, and Al have been measured by electrophoretic and electroosmosis method to evaluate the electrical properties of surfaces, respectively. The zeta potential of oxide and metal surfaces showed similar values to those of particles as a function of pH. The interaction energy between alumina and silica particles and TEOS, W and Al substrate were calculated based on DLVO theory. No deposition of silica particles on TEOS and the heavy deposition of alumina particles on metal substrates were observed in the particle deposition test. Experimental results were well agreed with the theoretical calculation.
Layer-By-Layer Oxidation of Silicon Surfaces
Authors: Watanabe Heiji , Miyata Noriyuki , Ichikawa Masakazu
Published: April 2011

Layer-by-layer oxidation of Si(111) and (001) surfaces has been studied by using scanning reflection electron microscopy (SREM). We found that SREM images reveal interfacial structures of the SiO2/Si system. Our results showed that the initial step structure of Si substrates was preserved at SiO2/Si interfaces and that interfacial steps did not move laterally during oxidation. We also observed a periodic reversal of terrace contrast in SREM images during the initial oxidation of Si(001) surfaces. These results indicate layer-by-layer oxidation of Si surfaces, which is promoted by the nucleation of nanometer-scale oxide islands at SiO2/Si interfaces. In addition, we investigated the kinetics of initial layer-by-layer oxidation of Si(001) surfaces. We found that a barrierless oxidation of the first subsurface layer, as well as oxygen chemisorption onto the top layer, occur at room temperature. The energy barrier of the second-layer oxidation was found to be 0.3 eV. The initial oxidation kinetics are discussed based on first-principles calculations. Moreover, we confirmed that the layer-by-layer oxidation of Si surfaces holds true for conventional furnace oxidation.
Two-Band Tunneling Currents and Stress-Induced Leakage in Ultra-Thin SiO2 Films
Authors: Okhonin S. , Ils A. , Bouvet D. , Fazan P. , Guegan G. , Deleonibus S. , Martin F.
Published: April 2011

The conduction band and valence band electron tunneling currents in ultra-thin SiO2 films at the transition from direct to Fowler-Nordheim tunneling regimes are studied. The slopes of the current voltage characteristics agree well with the simulations performed. The Stress-Induced Leakage Current (SILC) behavior is quite similar for both conduction and valence band currents even if the amplitude of the valence band SILC is much lower. We show that a linear dependence exists between the stress-induced interface trap density and both valence and conduction band SILC. A new model of SILC is also proposed.
Low Damage Nitridation of Silicon Oxide Surfaces By Remote-Plasma-Excited Nitrogen
Authors: Saito Yoji , Mori Ukyo
Published: April 2011

We incorporated significant density of nitrogen only near the top surfaces of the thermally grown oxides by the fluorination at room temperature followed by atomic nitrogen treatment around 550°C. Average nitrogen concentration of more than 6 percent was obtained in the nitrided layer with thickness below 1 nm. We fabricated MOS devices using the nitrided oxide films without hydrogenation, and measured capacitance-voltage characteristics. The density of nitridation-induced interface defects in the MOS device was estimated to be below 2×1010 cm−2. The proposed technique identifies a unique process for obtaining high quality ultrathin dielectrics.
Bulk and Surface Electronic Properties of Oxide Dielectrics
Authors: Henrich Victor E.
Published: April 2011

The electronic properties of oxides that are candidates for high-dielectric insulators in ULSI are discussed. The theoretical models that can be used to describe them are compared, and the properties of cation oxidation state and point defects associated with non-stoichiometry in the bulk and on the surface are considered. Metal-oxide surfaces often reconstruct, with the creation of a surface dipole moment The effect of overlayers on metal-oxide surfaces is also discussed.
Transient Diffusion Effects of Sb and B In Si Induced by Medium- and High-Energy Implants of Si+ and As+ Ions
Authors: Lulli G. , Solmi S. , Bianconi M. , Napolitani E. , Carnera A.
Published: April 2011

In this work we investigate the influence of defects injected by ions of different mass and energy on the diffusion of B and Sb markers in bulk Si. MeV (Si or As) ions induce Sb transient enhanced diffusion, whose amount increases with increasing the near-surface vacancy supersaturation generated by the knock-on recoil mechanism. The enhancement effect lasts less than 2 h at 800 °C and less than 10 min at 900 °C. At higher (1000 °C) annealing temperature it appears that the influence of extra-interstitials introduced by the implants comes into play, inducing a retardation in Sb diffusion which is larger for the higher close implant. The effect of vacancy supersaturation observed in medium-energy implanted samples is considerably weaker than the one found in high-energy implanted ones. In the case of B marker high-energy implantation induces moderate enhanced diffusion, much smaller than the one observed -after medium-energy implants.
Nitrogen Implantation and Diffusion in Silicon
Authors: Adam Lahir Shaik , Law Mark E. , Dokumaci Omer , Haddara Yaser , Murthy Cheruvu , Park Heemyong , Hegde Suri , Chidambarrao Dureseti , Mollis Steve , Domenicucci Tony , Dziobkowski Chester , Jones Kevin , Wong Philip , Young Ralph , Srinivasan R.
Published: April 2011

Nitrogen implantation can be used to control gate oxide thicknesses [1,2]. This study aims at studying the fundamental behavior of nitrogen diffusion in silicon. Nitrogen at sub-amorphizing doses has been implanted as N2+ at 40 keV and 200 keV into Czochralski silicon wafers. Furnace anneals have been performed at a range of temperatures from 650°C through 1050°C. The resulting annealed profiles show anomalous diffusion behavior. For the 40 keV implants, nitrogen diffuses very rapidly and segregates at the silicon/ silicon-oxide interface. Modeling of this behavior is based on the theory that the diffusion is limited by the time to create a mobile nitrogen interstitial.
Manufacturable Large Area CdS Thin Films for Solar Cell Applications Monitored with Optical Emission Spectroscopy
Authors: Wang L. , Eisgruber I. , Hollingsworth R. , DeHart C. , Wangensteen T. , Treece R. E. , Bhat P. , Shafarman W. N. , Birkmire Robert W. , Gillespie T. J.
Published: April 2011

Manufacturable, sputtered, device-quality, CdS thin films are reported for high efficiency solar cell applications. The sputtering plasma is monitored during deposition using optical emission spectroscopy. Optical emission spectroscopy (OES) is commonly used as an end point detector in plasma etching processes, where the disappearance of the etch product wavelength signature provides an unambiguous indication of completion. OES is only now beginning to be examined for controlling deposition processes, primarily because the dependence between OES signal and film properties can frequently be a quite complex function of the electron and gas densities, the emitting species concentration, the electron impact excitation cross section, the electron energy distribution function, and the probability of inelastic collisions between plasma species. OES monitoring during CdS sputtering allows accurate determination of deposition rate. Both Cd and S emission peaks can be identified, allowing tracking of the results of preferential sputtering. The OES output has been tied directly into the chamber controls, resulting in automatic closed-loop control of deposition rate. The resulting CdS films are device-quality and well-suited to large-scale manufacturing. A photovoltaic efficiency of 12.1 % was obtained from sputtered CdS on CIGS absorber, compared to 12.9% for the traditional, but less manufacturable, chemical bath deposited CdS on the same batch of CIGS. The sputtering technique has many advantages over other deposition techniques, such as easy scaleablity to large areas, simple process control, compatibility with in-line manufacturing of layered devices and low cost. RF, or lower-cost pulsed DC, sputtering power supplies can be used with comparable deposition rates. The structure, optical, and electrical properties of the sputtered CdS thin films have been characterized.
Martensitic Nucleation in Small ZrO2 Particles
Authors: Chen I-Wei , Chiao Yi-Hung
Published: April 2011

Small ZrO2 particles were studied by in-situ transmission electron microscopy and the types of events which led to martensitic nucleation were recorded. These metastable particles were single crystals of several hundred nanometers size and were supported on a carbon thin film but were otherwise free from any constraint. At room temperature, they are more than 1200°C below the equilibrium temperature. After dislocation loops were injected in-situ into the originally defect-free particles, a critical loop size was found beyond which the particle transformed spontaneously. It was also observed that Hertzian contacts between two particles led to martensitic nucleation and spontaneous transformation. These results were satisfactorily rationalized by ab-initio theoretical analysis.
Kinetics of Metallic Glass Formation by Solid State Reactions
Authors: Samwer K. , Schröder H , Moske M.
Published: April 2011

Metallic glass formation by solid state reactions has been observed in multilayer Zr-Co diffusion couples. The kinetics of the reaction are limited by the diffusion of the Co-atoms in the growing amorphous layer, at least for longer times, as shown by cross-sectional transmission electron microscopy and resistance measurements. The latter one provides the interdiffusion constant and the activation energy of about 1.1 eV. Deposition of the crystalline layers at 77 K results in an enhanced amorphization process in the first stage of the reaction and gives preliminary answers about the nucleation of the amorphous phase.
The Melting of Amorphous Si
Authors: Poate J. M. , Peercy P. S. , Thompson M. O.
Published: April 2011

The prediction by Turnbull and his colleagues that amorphous Si and Ge undergo first order melting transitions at temperatures Taℓ substantially beneath the crystalline melting temperature Tcℓ has stimulated much work. Structural, calorimet:ic and transient conductance measurements show that, for Si, Tcℓ – Taℓ lies in the range 225–250°K. Studies of the pulsed laser melting of the Si amorphous-liquid transition have resulted in the following findings, an estimate of the undercooling rate of 15°K/m/sec, an understanding of the mechanism mediating explosive crystallization, the formation of internal melts and segregation of dopants at the liquid-amorphous interface.
Ultrafast Electron Dynamics in Ge Quantum Dots
Authors: Stella A. , Tognini P. , De Silvestri S. , Nisoli M. , Stagira S. , Cheyssac P. , Kofman R.
Published: April 2011

An analysis of the ultrafast response of Ge quantum dots, with average radii of 4 nm and 16 nm, is reported here. Pump and probe experiments allowed investigation of the wavelength region between 450 and 750 nrm, characterized by the absorption peaks due to the E, and E1+Δ1 interband transitions. Two different time regimes have been identified: a first one (τ ≤ 1 ps) associated with pump-induced conduction band filling in the τ-L direction in the Brillouin zone; a second one (τ up to 100 ps) associated with band gap renormalization caused by the carrier interaction in the conduction band. Quantum confinement effects show up in terms of sizedependent blueshift of the E1+Δ1 spectral feature.
Strain in Coherent Ge Quantum Islands on Si Measured by Transmission Electron Microscopy
Authors: Liu Chuan-Pu , Miller Peter D. , Henstrom William L. , Gibson J. Murray
Published: April 2011

We describe a quantitative method for measuring the strain in small islands, and show results for coherent Ge islands on Si. The method uses dark field images from backside thinned samples in the transmission electron microscope. We show that no independent strain models are needed in the measurement, which employs an excellent “abrupt displacement” approximation. Results show that the strain in Ge domes is higher than in pyramids as expected.
Luminescent Characteristics of Pulsed Laser Deposited Epitaxial Eu-Doped Y2O3 Films
Authors: Kumar D. , Cho K. G. , Chen Zhang , Craciun V. , Holloway P. H. , Singh Rajiv K.
Published: April 2011

The growth, structural and cathodoluminescent (CL) properties of europium activated yttrium oxide (Eu:Y2O3) thin films are reported. The Eu:Y2O3 films were grown in-situ using a pulsed laser deposition technique. Our results show that Eu:Y2O3 films can grow epitaxially on (100) LaAlO3 substrates under optimized deposition parameters. The epitaxial growth of Eu:Y2O3 films on LaAlO3, which has a lattice mismatch of ∼ 60 %, is explained by matching of the atom positions in the lattices of the film and the substrate after a rotation. CL data from these films are consistent with highly crystalline Eu:Y2O3 films with an intense CL emission at 611 nm.
Spin-Dependent Transport in Manganite Trilayer Junctions
Authors: Sun Jonathan Z.
Published: April 2011

Doped manganite trilayer junction provides a model system for the study of spin-dependent transport across an artificial interface between manganites. Large interface magnetoresistance is observed in manganite trilayer junctions. Further studies reveal a strongly temperature and junction-bias dependent magnetoresistance, as well as a large interaction between the spin-polarized current and the ferromagnetic moment. The physical and materials origin of these and other junction properties are discussed in this brief review.
Epitaxial Growth of Yb2O3 Buffer Layers on Biaxially Textured-Ni (100) Substrates by Sol-Gel Process
Authors: Chirayil T. G. , Paranthaman M. , Beach D. B. , Morrelli J. S. , Sun E. Y. , Goyal A. , Williams R. K. , Lee D. F. , Martin P. M. , Kroeger D. M. , Feenstra R. , Verebelyi D. T. , Christen D. K.
Published: April 2011

In order to develop an alternative buffer layer architecture using the sol-gel process to produce YBCO (YBa2Cu3O7-δ) coated conductors, Yb2O3 has been chosen as the candidate material. Buffer layers of Yb2O3 were epitaxially grown on biaxially textured-Ni (100) substrates by the sol gel process for the first time. The Yb2O3 precursor solution was prepared from an alkoxide sol-gel route in 2-methoxyethanol and was deposited on textured-Ni (100) substrates by either spin coating or dip coating methods. The amorphous film was then processed at 1160°C under flowing (96%)Ar/H2(4%) gas mixture for one hour. The Yb2O3 film exhibited a strong c-axis orientation on the Ni (100) substrates. The phi and omega scans indicated good in plane and out of plane orientations. The X-ray (222) pole figure showed a cube-on-cube epitaxy. High current YBCO films were grown on the Yb2O3 sol-gel buffered-Ni substrates.
Enhancement in Electrical Properties of (Ba,Sr)TiO3 Films Using Tailored Oxide Electrodes
Authors: Choi Duck-Kyun , Park Kyung-Woong , Park Jeong-Hee , Oh Se-Hoon , Kim Boum-Seock , Lee Jae-Bok
Published: April 2011

Selection of a proper electrode for high dielectric material such as (Ba, Sr)TiO3 is a great concern because the deposition of BST requires a high temperature and an oxidizing atmosphere. In this study, we suggested the perovskite-type electrodes, which provide a structural match with the BST dielectric material, under the recognition that the high leakage current is associated with the structural mismatch between BST and the electrode. We studied the (Ca,Sr)RuO3 electrode of which the lattice parameter can be tuned to fit into BST by changing the Ca/Sr ratio. We also studied (Ba,Sr)RuO3 electrode which is not only structurally identical but also chemically similar to BST. In addition, the effect of doping in the BSR electrode was investigated to minimize the leakage current by proper modulation of the barrier height. The electrodes were directly deposited on an Si substrate and all the films in the experiments were deposited by RF magnetron sputtering technique. Electrical properties were measured from MIM structure. The main focus was to address the effect of Ca/Sr and Ba/Sr ratio variations in the electrodes on the resulting dielectric constant and the leakage current. The interface characteristics between the BST film and the electrode were examined in order to interpret the electrical properties of BST films.
First-Principles Calculations of Nonlinear Optical Response Functions in Semiconductors
Authors: Rashkeev Sergey N. , Lambrecht Walter R. L.
Published: April 2011

We present our implementation of the length-gauge formalism of Sipe and coworkers (Phys. Rev. B 48, 11705 (1993); ibid 52, 14636 (1995)) using the linearized muffin-tin orbital (LMTO) method and discuss its application to the calculation of second order response functions. The importance of gap corrections beyond LDA is discussed. As primary application, we discuss the second harmonic generation (SHG) coefficients of the SiC polytypes and of the chalcopyrites of both the II-IV-V2 and I-III-VI2 families. These examples illustrate the relation of the second order response function to the modification of the crystal structure and chemical substitutions.
The First Principles Study on Light Emitting Properties of Semiconducting Metal Silicides
Authors: Yamaguchi Kenji , Mizushima Kazuki , Sassa Koichi
Published: April 2011

Semiconducting metal silicides are potential candidates of silicon-based light emitting materials. In order to carry out screening of the candidates, we calculated the oscillator strength between the valence and excited states near the band gap for various silicides. The electronic states were obtained by the full-potential linear augmented-plane-wave method (FLAPW) based on the local density approximation (LDA). The results show Ru2Si3 and Ca2Si have direct gap at τ point, but the values of the oscillator strength across the gap are evaluated to be zero. Among the indirect gap semiconductors, β-FeSi2, OsSi, and OsSi2 have several peaks and valleys facing each other near the band gap. Among the combinations, we obtained the biggest value of oscillator strength 0.3 at X point for OsSi with the transition energy of 0.42 eV.
Simulation Of Diffuse Light Exposure Of Low Temperature Co-Fired Ceramic Tapes And The Problem Of Sidewall Morphology
Authors: Espinoza-Vallejos P. , Santiago-Aviles J. , Sola-Laguna L.
Published: April 2011

We have simulated the scattering of UV light in a photo-formable ceramic tape and experimentally measured the transport mean free path (random walk step) between scattering events. After processing the tape we have achieved features size of 70 μm in a 150 μm-thick tape. We were able to predict and control the undercut due to scattering of the light by alumina grains. The experimental verification of the model utilizes a modified version of diffuse-Transmission Spectroscopy (DTS) using the material development characteristics as a sensor. The technique involves the measurement of absorption coefficient by measuring the sample thickness as a function of energy. We also simulated the effect of changing the number density of scatter centers in side-wall morphology.
In Situ Morphological Study of The Al/SiO2 Reaction Around The eutectic Point
Authors: Allam Lévy , Fleury Vincent
Published: April 2011

In the context of the electronic industry, thin films of aluminum are deposited on silica. However, the Al/SiO2 interface is unstable. A reaction leading to oxidation of Al and reduction of SiO2 occurs. We present an in situ study of this reaction, in thin films, at temperatures above 500°C. This experiment allows to understand the essential steps of the oxidation of Al by SiO2, and it shows that thermal cycles can be used to generate nucleation centers artificially. More generally, the morphological interpretation of out-of-equilibrium growth patterns gives important insight into the coupling between the thermodynamics and morphological aspects of a thin film chemical reaction.
A DICTRA Simulation of θ – phase Dissolution in Al-Cu Alloys
Authors: Thompson Raymond G. , Malam Curt
Published: April 2011

This paper presents a comparison between the computer simulation dissolution model, DICTRA, and an experimental data set from the literature, Baty, Tanzilli and Heckel, 1970. This was undertaken to support research on the modeling of the weld heat-affected zone where grain growth and Zener pinning control materials properties. BTH present quantitative-microscopy data on the dissolution of 5 size classes in their 4.2μ particle sample and 4 size classes in their 0.44μ sample. The DICTRA example of the 3-cell calculation of cementite particles in steel was used as the model to simulate the BTH experiment.