bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of the Synthesis Parameters on Textural and Structural Properties of MCM-41 Mesoporous Materials
Authors: Terrés E. , Ramírez S. S. , Domínguez J. M. , Montoya A. , Navarrete J. , Gómez-Cisneros M.
Published: April 2011

MCM-41 mesoporous materials were synthesized under different hydrothermal conditions using organic templates, i.e. CTMA-Br, DTMA-Br. Reaction temperature (120 to 195 °C) and reaction time (24 to 120 hr) varied and their influence on the structure properties of MCM-41 was sought i.e. d = 36 to 41.6 Å for distinct micelles diameters. Also, insertion of polyaromatics into the surfactant micelles was determinant in the final pore diameter, i.e d = 35.4 to 48.6 Å.
Emission Control Catalyst Derived from Mesoporous Molecular Sieves
Authors: Paul Partha P. , Miller Michael A. , Heimrich Martin J. , Schwab Stuart T.
Published: April 2011

A lean NOx catalyst is needed to control NOx emissions generated by oxygen-rich combustion processes to obtain higher fuel economy. We have developed such a catalyst using modified mesoporous molecular sieves (MCM-41). An iron(II)-complex impregnated MCM-41 has been synthesized which has been further treated with [Pd(NH3)4]Cl2. This treatment resulted in further exchange of Na+ ions of the molecular sieves with Pd(NH3)42+ thus forming Catalyst A. The catalytic activity towards NOx, CO and HC was studied using simulated exhaust gas, as well as engine exhaust gas.
Preparation of Microporous Films with Sub Nanometer Pores and their Characterization Using Stress and FTIR Measurements
Authors: Samuel J. , Hurd A. J. , van Swol F. , Frink L. J. Douglas , Brinker C. J. , Contakes S. C.
Published: April 2011

We have used a novel technique, measurement of stress isotherms in microporous thin films, as a means of characterizing porosity. The stress measurement was carried out by applying sol-gel thin films on a thin silicon substrate and monitoring the curvature of the substrate under a controlled atmosphere of various vapors. The magnitude of macroscopic bending stress developed in microporous films depends on the relative pressure and molar volume of the adsorbate and reaches a value of 180 MPa for a relative vapor pressure, P/Po = 0.001, of methanol. By using a series of molecules, and observing both the magnitude and the kinetics of stress development while changing the relative pressure, we have determined the pore size of microporous thin films. FTIR measurements were used to acquire adsorption isotherms and to compare pore emptying to stress development, about 80% of the change in stress takes place with no measurable change in the amount adsorbed. We show that for sol-gel films, pore diameters can be controlled in the range of 5 – 8 Å by “solvent templating”.
Synthesis and Structural Studies of Microporous Yttria-Stabilized Zirconia Ceramics
Authors: Srinivasan R. , Sparks D. E. , Milburn D. R. , Davis B. H.
Published: April 2011

Yttria-stabilized zirconia was prepared by (i) coprecipitation and (ii) alkoxide hydrolysis. The thermal and X-ray diffraction data were compared. The coprecipitation method yields microporous materials after calcination at 500°C for 4 hours with a narrow pore size distribution at a radius of 2–2.5 nm. Similar results were also seen with the alkoxide hydrolysis.
Sol-Gel Process form Heterometallic Alkoxides to Incorporate Alkaline- and Rare Earths in Alumina for automotive Applications
Authors: Narula C. K.
Published: April 2011

The high cost of materials prepared by sol-gel processing and the loss of useful surface properties at elevated temperature has prevented the application of sol-gel processed materials in automotive exhaust reduction catalyst formulations. In this report, we briefly describe the important developments needed in the next generation automotive catalysts and the role of sol-gel processed materials. We will also discuss the application of heterometallic alkoxides as sol-gel precursors to achieve the molecular distribution of lanthanides and alkaline earths in alumina matrices needed for the stabilization of alumina based materials at elevated temperatures.
Colloidal Processing of Temperature Shock Resistant SiC with Tailored Porosity
Authors: Aslan Mesut , Nass Rüdiger , Schmidt Helmut
Published: April 2011

From aqueous slurries containing SiC powder coated with nano-scaled carbon black, green bodies were prepared by slip casting. On slip cast green bodies the densification, microstructural development and mechanical properties were investigated. Depending on the sintering temperature and boron carbide content samples with different relative densities between 0.90 and 0.988 were obtained after pressureless sintering. In all samples a homogeneous microstructure (distribution of the residual pores and grain morphology) was observed. Due to this homogeneity the sintered samples showed high amount of fracture strength of about 500 MPa, even at large residual porosities of 10 %. The thermal shock resistance of samples with different porosities measured by water quenching revealed the critical temperature difference to be around 700 K.
Local Microstructural Organization in Carbogenic Molecular Sieves
Authors: Kane Michael S. , Foley Henry C.
Published: April 2011

The microstructure of nanoporous, carbogenic molecular sieves (CMS) was studied using high resolution electron microscopy and neutron diffraction. The narrow range of pore sizes observed in these complex materials suggests that although these materials are globally amorphous, the local microstructural features are more organized. Our work, focused on poly(furfuryl alcohol)-derived CMS, is aimed at characterizing the evolution of this microstructure. Microscopy results show that materials synthesized at low temperature have some degree of organization but that the microstructure is featureless and symmetric at longer length scales. This symmetry is broken at higher synthesis temperatures as thermodynamic driving forces lead to further organization of the carbon atoms into more ordered structures but the length scales remain short. Micrographs of high temperature CMS show a high degree of curvature and features reminiscent of fullerene. The connectivity of the carbon atoms in the CMS has been probed using powder neutron diffraction. This data suggests that the atoms in the CMS form ordered structures on the length scale of 15Å which are distinctly different from the structure of graphite. These observed changes in the microstructure directly impact the adsorptive and molecular sieving characteristics of the CMS as illustrated by the marked differences between the diffusivities of oxygen and nitrogen. This property is crucial for the very demanding separation of nitrogen from oxygen in air.
Raman Spectroscopy Studies of Reactions Between Sulfur Dioxide and Microparticles of Hydroxides
Authors: Aardahl C. L. , Davis E. J.
Published: April 2011

Gas-aerosol chemical reactions between dilute SO2 and alkali-metal hydroxides have been explored using elastic and inelastic (Raman) light scattering. Single charged particles of NaOH, KOH, and Ca(OH)2 were levitated electrodynamically in a reaction chamber and exposed to humid nitrogen. Particles that were not water soluble remained crystalline while water soluble compounds deliquesced into solution microdroplets. The resulting solids or solutions were reacted with dilute SO2 in humid N2. Elastic scattering measurements and Raman spectra were taken during the gas-aerosol reactions, and results indicate that reaction products and sorbent utilization are highly dependent on the water content of the particle.
Formal Charge Model for Predicting Structures, Acid-Base, and Ion Exchange Properties of Mixed Oxides
Authors: Bunker B. C.
Published: April 2011

The range of mixed-oxide materials used in ion exchange and catalytic materials is rapidly expanding from aluminosilicates such as zeolites and clays into materials whose structure and chemical properties are more difficult to predict and understand. A simple model based on local charge has been developed to predict distributions of local bonding configurations of both cations and anions in mixed oxides. The model, illustrated for the case of silicotitanates, provides qualitative predictions regarding both the acid-base and ion exchange properties of such materials as a function of composition.
Getting a Charge Out of Microporous Oxides: Building a Better Ultracapacitor
Authors: Liu Kuo-Chuan , Anderson Marc A.
Published: April 2011

Microporous nickel oxides consisting of nano-sized particles have been utilized as active electrode materials for ultracapacitors. Both the physical adsorption of ions near the charged surface of these particles and surface oxidation/reduction reactions play a role in the capacitative charge storing mechanism. These are therefore appropriately referred to as pseudo-capacitors since they rely on mechanisms in addition to double layer charging in order to store energy. In this study, it has been shown that surface hydration contributes to the formation of an initial compound which participates in the electrochemical reactions of ultracapacitors. The specific capacitance of this material is ranging from 60 to 120 F/g depending upon the types of electrolyte solution used in the ultracapacitor.
Silver Sorption by Manganese Oxide
Authors: Ravikumar R. , Fuerstenau D. W.
Published: April 2011

Silver-manganese oxide ores are present in western United States, Mexico, South America, and Sumatra. The amount of silver varies between a few parts per million (ppm) to thousands of ppm. However, these ores are not compatible with conventional metallurgical treatment for the extraction of silver. This research is the study of the nature of silver binding with one model manganese oxide phase, cryptomelane. Cryptomelane is widely present in the United States and in parts of Colorado, with silver-bearing cryptomelane ore bodies containing up to a maximum of 1 wt% of silver. In order to better understand the nature of silver binding in cryptomelane, synthetic samples of cryptomelane were prepared and characterized, and then used for silver sorption experiments. The silver uptake appears to be a function of the solution chemistry conditions, pH and potassium nitrate concentration. The sorption of silver was found to increase with decreasing pH and at a fixed pH value, the sorption density was higher at a lower potassium nitrate concentration. Kinetics and equilibrium sorption data from lithium and sodium nitrate background electrolyte demonstrates three main results: firstly, most of the uptake of silver is compensated by release of potassium; secondly, the exchange for silver with protons and potassium ions is almost stoichiometric; and lastly, the importance of tunnel sites for the sorption reaction in cryptomelane. An ion-exchange model for the uptake of silver onto cryptomelane will also be discussed.
Surface-Controlled Reactivity of Metal Carbonates
Authors: Brady P. V.
Published: April 2011

Metal carbonate surfaces are a common component of soils, sediments, terrestrial organisms, and many engineered structures. The surface-controlled growth and dissolution of metal carbonate minerals (e.g. calcite) often affects fluid flow in pipes (through scaling) as well as the nanoscale assembly of complex biologic structures (similar reactions control Ca levels in the oceans, and ultimately, long-term CO2 levels). Engineering metal carbonate surface chemistry to enhance or inhibit growth, dissolution, or crystal nucleation is therefore an area with obvious economic impact. Metal carbonate superstructures are rapidly altered by dissolution/re-precipitation reactions, necessitating the measurement of surface chemistry near equilibrium. Measurements of metal sorption using limited residence time reactors point to the importance of adsorbed/exchanged metal ions in controlling surface charge and electrokinetic behavior. The same reactions appear to control growth and dissolution rates as well.
The Effect of the Adsorption of Metal Ions on the Interfacial Behavior of Silicate Minerals
Authors: Huang Picheng , Fuerstenau Douglas W.
Published: April 2011

Because of its importance in the fields of environmental and mineral engineering, the adsorption mechanism of metal ions on oxides has been studied rather extensively using such techniques as titration, adsorption isotherm determination, flotation and spectroscopy. However, limited work has been done to compare the behavior of hydrophilic silicates with those that are naturally hydrophobic. Our investigation was undertaken to provide a better understanding of the adsorption mechanism of selected metal ions at the solid/liquid interface through simultaneous measurements of zeta potentials, adsorption densities and turbidity on colloidal suspensions of two silicate minerals, quartz and talc, as a function of pH, to delineate the effect of hydrophobicity and surface heterogeniety on these processes.
Fabrication of YMnO3 Films: New Candidate for Non-Volatile Memory Devices
Authors: Fujimura Norifumi , Ishida Tadashi , Yoshimura Takeshi , Ito Taichiro
Published: April 2011

We have proposed ReMnO3 (Re:rare earth) thin films, as a new candidate for nonvolatile memory devices. In this paper, we try to fabricate (0001) oriented YMnO3 films on (111)MgO, (0001)ZnO:Al/(0001) sapphire and (111)Pt/(111)MgO using rf magnetron sputtering. We succeed in obtaining (0001) epitaxial YMnO3 films on (111) MgO and (0001)ZnO:Al/(0001)sapphire substrate, and polycrystalline films on (111)Pt/(1 11)MgO for the first time. Electrical property of the bottom electrode (ZnO:Al) changes with varying the deposition condition of YMnO3 films. However, we find an optimum deposition condition of ZnO:Al film such that it functions as a bottom electrode even after YMnO3 film deposition. The dielectric properties of the epitaxial and polycrystalline YMnO3 films are almost the same. The YMnO3 films show leaky electrical properties. This may be caused by a change in the valence electron of Mn from 3+.
Microstructure Control in Mocvd PZT Thin Films
Authors: Kim Daesig , Kim Tae-Young , Lee June Key , Tao W. , Desu Seshu B.
Published: April 2011

It was shown that Pb(ZrxTi1−x)O3 thin films (PZT) can be successfully deposited by metalorganic chemical vapor deposition (MOCVD) in a wide deposition temperature range starting from 400°C to 600°C. Variations in texture, morphology and grain size of the films as a function of process parameters were systematically investigated by x-ray diffraction (XRD) and scanning electron microscopy (SEM). The deposition temperature and gas composition in the reactor are the two key parameters that control the film microstructure. The accompanying changes in the ferroelectric properties with respect to the variations of the process parameters will also investigated. In addition, we found an interrelationship between the grain orientation and surface roughness of the films. Films with (111) preferred orientation are significantly smoother than the films with other preferred orientations. We also demonstrate, for the first time, fine grained PZT films with very low surface roughness, which show excellent electrical properties can be obtained by lowering the deposition temperature (e.g. 430°C)
Analysis of Pulsed Excimer Laser Ablation of PZT, Pb And Ti in an Oxygen Ambient Using Energy Dispersive Mass Spectrometry
Authors: Coccia L. G. , Tyrrell G. C. , Boyd I. W.
Published: April 2011

A number of factors have been identified as affecting the gas phase oxidation of cations during pulsed laser ablation of lead zirconate titanate (PZT), by using energy dispersive mass spectrometry (EDMS). These phenomena are known to be critical to the deposition of high quality thin films of PZT. However, to isolate the role of each cation species and the influence of its gas phase properties, we have also looked beyond the ablation of the PZT ceramic. In this paper, we detail our observations during pulsed laser ablation of electroceramic and metallic targets, specifically PZT, Pb and Ti. We have observed the evolution and transport of molecular species during gas phase expansion over a wide range of oxygen pressures (10−7 - 10−1 mbar) and laser fluences (0.3 -10 Jcm−2). The yields of the molecular ion species are strongly dependent upon the number density of the background gas. We propose an interpretation of the relative yields of the species based upon their respective gas phase binding energies and their ease of formation based upon the reaction thermodynamics and reaction cross-section of each species.
Integrated Decoupling Capacitors using Pb(Zr,Ti)O3 Thin Films
Authors: Dimos D. , Lockwood S.J. , Garino T.J. , Al-Shareef H.N. , Schwartz R.W.
Published: April 2011

Thin-film decoupling capacitors based on ferroelectric (Pb,La)(Zr,Ti)O3 films are being developed for use in advanced packaging applications. The increased integration that can be achieved by replacing surface-mount capacitors should lead to decreased package volume and improved high-speed performance. For this application, chemical solution deposition is an appropriate fabrication technique since it is a low-cost, high-throughput process. The use of relatively thick Pt electrodes (˜1 μm) to minimize series resistance and inductance is a unique aspect to fabricating these devices. In addition, the important electrical properties are discussed, with particular emphasis on lifetime measurements, which suggest that resistance degradation will not be a severe limitation on device performance. Finally, some of the work being done to develop methods of integrating these thin-film capacitors with ICs and MCMs is presented.
Piezoelectric Characterization of Bulk and Thin Film Ferroelectric Materials using Fiber Optics
Authors: Dawley J.T. , Teowee G. , Zelinski B.J.J. , Uhlmann D.R.
Published: April 2011

In this study, the use of a fiber optic technique for the measurement of the piezoelectric properties of ferroelectric bulk and thin film samples was investigated. The strain and piezoelectric properties (namely the d33 coefficients) were measured using the MTI-2000 Fotonic Sensor, which uses the principle of the optical lever to resolve very small changes in sample displacement (1 Å). Using this technique, we were able to detect the very small strains associated with the converse piezoelectric effect for PVDF films and bulk PZT samples, and correlate the results with data acquired from direct piezoelectric effect measurement. Comparison of the data sets prove that the optical lever would be a useful optical technique for measuring of the d33 values of ceramic thin films, such as BaTiO3, ZnO, and PZT.
Processing and Piezoelectric Properties of Mod Pzt Films and Pzt/Polymer Composite Coatings
Authors: Wright J.S. , Francis L.F.
Published: April 2011

Lead zirconate titanate, Pb(Zr0.53Ti0.47)O3 (PZT), coatings were prepared using a metallorganic decomposition (MOD) route with lead and titanium acetates and zirconium acetylacetonate in acetic acid and water. Films with thickness of 0.66 μm were prepared on (100) Si with a layered bottom electrode (Pt/Ti/TiO2/SiO2). Dielectric constant and loss were 1100 and 0.04 (1 kHz), respectively, and remnant polarization and coercive field were 30 μC/cm2 and 40 kV/cm. Piezoelectric coefficient (d33) of the PZT film, measured with a singlebeam laser interferometer, was 41 pm/V. Standard micromachining techniques were used to etch the PZT to form discrete PZT posts for preparation of the ceramic phase for composite coatings with a 1–3 connectivity. SEM was used to determine the dense and etched film microstructure. Preliminary ion milling results, used to etch the PZT, are also presented.
Size Effects and Domains in Ferroelectric Thin Film Actuators
Authors: Trolier-Mckinstry S. , Randall C. A. , Maria J. P. , Theis C. , Schlom D. G. , Shepard J. , Yamakawa K.
Published: April 2011

Ferroelectric thin films typically differ from bulk ceramics in terms of both the average grain size and the degree of stress imposed on the film by the substrate. Studies on bulk ceramics have demonstrated that the number of domain variants within grains depends on the grain size for sizes <˜lμm. This can diminish the poling efficiency of the material. Since most thin films show primary grain sizes well below a micron, similar effects should be observed in films. In addition, since the perovskite ferroelectrics contain ferroelastic as well as ferroelectric domains, it seems clear that stress in thin films may markedly alter the degree to which domain walls contribute to the observed properties. In this paper, the relative importance of these factors are discussed for several types of ferroelectric thin films. Films have been prepared by pulsed laser deposition, magnetron sputtering, and by sol-gel processing. It has been found that epitaxial BaTiO3 films are ferroelectric at 77K down to thicknesses as low as ˜ 60nm. Data on the low and high field electrical properties are reported as a function of temperature, the film crystallinity, and film thickness for representative perovskite films.
SrBi2Ta2O9 Capacitors for a Mega-Bit Ferroelectric Nonvolatile Memory
Authors: Amanuma Kazushi , Kunio Takemitsu , Cuchiaro Joe
Published: April 2011

SrBi2Ta2O9(SBT) capacitors were integrated to the structure for a mega-bit nonvolatile memory, and their electrical properties after metallization were investigated. Annealing above 500°C after contact-etching was necessary to obtain good electrical properties. A well saturated hysteresis loop with 2Pr of more than 15μC/cm2 was obtained for the 0.7×0.7μm capacitor. The read-out polarization was very stable in 105 sec after the write-pulse. No fatigue or imprint was observed up to 1011 cycles. These results show suitability of SBT capacitors for a mega-bit non-volatile memory.
Integration Aspects and Electrical Properties of SrBi2Ta2O9 for Non-Volatile Memory Applications
Authors: Taylor D.J. , Jones R.E. , Lii Y.T. , Zurcher P. , Chu P.Y. , Gillespie S.J.
Published: April 2011

Highlights and solutions to some of the challenges involved in integrating SrBi2Ta2O9 (SBT) capacitors with Pt electrodes on silicon wafers for non-volatile memory applications are discussed. These include the diffusion of Bi through the Pt bottom electrode during firing, capacitor patterning, and process damage that results from hydrogen containing atmospheres.

Next, studies of the temperature dependence of many of the important electrical properties of SBT are presented. These include the remanent polarization (2Pr), the non-volatile polarization (Pnv), and the coercive field (Ec) all of which are studied as functions of the pulse amplitude; fatigue resistance of 2Pr and Pnv; the retention; the small signal capacitance versus voltage behavior; and the current versus voltage behavior. These studies demonstrate that SBT looks very promising for ferroelectric non-volatile memories over the consumer application range (0 to 70 °C).
Dislocation Nucleation and Multiplication During Nanoindentation Testing
Authors: Mann A. B. , Pethica J. B.
Published: April 2011

Small volumes of crystalline material can exhibit near theoretical lattice strengths due to the absence of pre-existing defects. We show here that careful control of experimental parameters and surface preparation are important in observing these increased stresses. In particular, tip impact kinetic energies at the initial contact of only a few eV have been found to influence events occurring at a much later stage in the loading cycle. This can be understood in terms of the energy required to deform a small number of atomic scale asperities and thus release sufficient surface energy to permit dislocation nucleation at impact. If the K.E. is not sufficient to overcome the asperities, dislocations must be nucleated at a later stage in the loading cycle, giving a apparently different mechanical property. We outline the implications for thin film systems where a hard surface layer may play a vital role, firstly, in preventing dislocation nucleation on impact and, secondly, in impeding the propagation of any such dislocations into the bulk below.
Hard Amorphous Hydrogenated Carbon Films Deposited from an Expanding Thermal Plasma
Authors: Gielen J. W. A. M. , Sanden M. C. M. Van De , Kessels W. M. M. , Schram D. C.
Published: April 2011

Diamondlike amorphous hydrogenated carbon is deposited from an expanding thermal argon/acetylene plasma. It is observed that the film quality improves with increasing deposition rate. To obtain the best material quality the admixed acetylene flow has to be of comparable magnitude as the argon ion flow from the plasma source (critical loading). A new method to determine the ion density in an argon/acetylene plasma, by probe measurements, is presented. They reveal that the deposition during critical loading is governed by radicals. It is suggested that acetylene is dissociated once and that the C2H radical is formed dominantly.
Microhardness Study Of Cathode-Mounted Amorphous Hydrogenated Boron Carbide
Authors: Lin Shu-Han , Li Dong , Feldman Bernard J.
Published: April 2011

We have grown cathode-mounted amorphous hydrogenated boron carbide thin films by rf plasma decomposition of diborane and methane. The chemical composition, infrared absorption, optical absorption, microhardness and adhesion of these thin films were measured. As a function of increasing diborane concentration in the feedstock, we observe increasing boron and decreasing hydrogen concentrations, increasing infrared absorption at 1300 cm-1 due to boron icosahedra, increasing optical band gaps, dramatically increased microhardness, and increased adhesion to the underlying substrates of these thin films. These results provide evidence that the presence of boron icosahedra increases microhardness, adhesion, and optical band gaps.
The Effect of the Passivation Material on the Stress and Stress Relaxation Behavior of Narrow Al-Si-Cu Lines
Authors: Witvrouw A. , Flinn P. , Maex K.
Published: April 2011

800 nm thick and 1μm wide Al-1wt.%Si-0.5wt.% Cu parallel lines with 1 μm spacing were passivated with PECVD oxide, oxynitride or nitride. Substrate curvature measurements as a function of temperature and XRD-measurements at room temperature were used to characterize macroscopic samples of these parallel Al-Si-Cu-lines. By using both techniques the average inplane stresses for the Al-Si-Cu lines as well as for the covering passivation material can be determined as a function of temperature. The highest and lowest stresses in the Al-Si-Cu are observed for lines with nitride and oxide passivations, respectively. Also the number of voids in the lines after a storage test at 250 °C is clearly highest for a nitride passivation and lowest for an oxide passivation.

The stress in the passivation itself and its temperature dependence is found to be very different from the stress in a blanket passivation film.
Morphological Instability of a Sic Film During Carbonization
Authors: Chiu C.-H. , Freund L. B.
Published: April 2011

A model is developed to understand the morphological stability of a SiC film on a Si substrate during carbonization where the Si substrate is exposed to a carbon precursor. The morphological stability is determined by considering the surface evolution along a slightly wavy film surface and film-substrate interface. The morphological evolution along the film surface is dominated by surface diffusion and along the interface by a chemical reaction. The kinetic analysis shows the stability is controlled by the film surface energy, the interface energy, the diffusion-reaction process of the carbon precursor, and the strain energy. At small wavelengths of the surface profiles, the two types of surface energy dominate, which results in stable morphology. The diffusion-reaction process dictates the surface stability at large wavelengths. The strain energy may cause the surfaces to become unstable at moderate wavelengths; the instability can be completely suppressed by the diffusion-reaction process and the film surface energy, while it is enhanced by a large value of interface energy.
Plastic Deformation in Thin Copper Films Determined by X-Ray Micro-Tensile Tests
Authors: Kretschmann A. , Kuschke W.-M. , Baker S. P. , Arzt E.
Published: April 2011

Plastic deformation in thin copper films has been studied at room temperature. Copper films having a thickness of 1 μm were made by sputtering onto nickel substrates with a Si3N4 underlayer and with or without a Si3N4 caplayer. Deformation experiments were conducted using a special micro-tensile tester built into a θ–θ diffractometer. The problems normally associated with tension tests of free-standing films were avoided by deforming the substrate and film together. In-situ x-ray measurements of the lattice spacings and lattice spacing distributions were used to determine both elastic and plastic strains. The effects of caplayer and annealing temperature on mechanical properties are reported.
Structural Transformations During Growth of Epitaxial Fe(001) Thin Films on Cu(001) and Pt(001)
Authors: Clemens B. M. , Hufnagel T. C. , Kautzky M. C. , Bobo J.-F.
Published: April 2011

We have used grazing incidence x-ray diffraction to observe the structural evolution during growth of sputter-deposited epitaxial Fe films on Cu(001) and Pt(001). We find that on Cu(001), Fe is fcc up to a thickness of 10–12 monolayers, whereupon bcc Fe is observed in first the Pitsch and then the Bain orientations. The fcc Fe shows some relaxation of the misfit from the Cu, as do the Pitsch orientation bcc, which is in tension, and the Bain orientation bcc, which is in compression. All three Fe variants exist in a 40 monolayer thick film. On Pt(001) the Fe grows as bcc with the Bain orientation. However, a thin (20 å) bcc Fe film is transformed to fcc Fe with cube-on-cube orientation by subsequent deposition of Pt. This behavior is consistent with intermixing of Pt into the Fe layer, which lowers the mismatch and bulk chemical energies of the fcc phase relative to that of the bcc phase.
Dynamic In-Situ Synchrotron X-Ray Topographic Observations Of Dislocations In Notched Ice Crystals
Authors: Hu X. , Baker I. , Dudley M.
Published: April 2011

Experimental observations of ice single crystals strained under uniaxial tension using synchrotron X-ray topography have shown that there is far more dislocation activity around notches at high temperature, -7.8°C, than at lower temperatures (-40°C and -60°C).
Static Atomic Displacements in Crystalline Solid Solution Alloys
Authors: Ice Gene , Sparks Cullie , Robertson J. Lee , Epperson J. Ernest , Jiang Xiaogang
Published: April 2011

Atom size differences induce static displacements from an average alloy lattice and play an important role in controlling alloy phase stability and properties. The details of this role however, are difficult to study; chemical order and displacements are strongly interrelated and static displacements are hard to measure. Diffuse x-ray scattering measurements with tunable-synchrotron radiation can now measure element-specific static displacements with an accuracy of ± 0.1 pm and can simultaneously measure local chemical order out to 20 shells or more. Ideal alloys for diffuse scattering analysis with synchrotron radiation, are those that have previously been the most intractable: alloys with small Z contrast, alloys with only local order and alloys with small size differences. The combination of precise characterization of local chemical order and precise measurement of static displacement provides new information that challenges existing alloy models. We report on an ongoing systematic study of static displacements in the Fe/Ni/Cr alloys and compare the observed static displacements to the static displacements predicted by current theories. The availability of more brilliant 3rd generation hard x-ray sources will greatly enhance these measurements.
X-Ray Absorption Analysis of Electroplated Permalloys Used in Microfabrication
Authors: MOLDERS N. , SCHILLING P. J. , He J.-H. , Saile V. , Moser H. O. , Menz W.
Published: April 2011

Electroplating is a key technology in the LIGA process (German acronym for Lithographie (Lithography), Galvano (Electroplating) and Abformung (Moulding)). The electroplating process determines the physical, chemical, and mechanical properties of a device. In the macro environment, the process is empirically understood arid electroplating results are fairly well predictable. For use in the micro environment, in particular in microfabrication of LIGA components with high-aspect-ratios, effects like delamination from the substrate, inhomogeneous material distribution, pores in the material and large grain sizes have to be avoided. It is, therefore, important to investigate the structure and composition of such materials. Various electroplated Permalloy foils have been prepared, which are of interest because of their soft magnetic behaviour and use as materials for microsensors and microactuators. X-ray absorption fine structure (XAFS) and x-ray absorption near edge structure (XANES) have been recorded at the Nickel and Iron K-edges (8333 and 7112 eV respectively) for electroplated Permalloy.
Investigations on Fe Lattice Strain Relaxation in the Al/Fe/Al Trilayer
Authors: Mayanovic Robert A. , Gutierrez Carlos J. , Prinz Gary A.
Published: April 2011

We have measured polarization-dependent Fe K-edge XAFS spectra from an epitaxially-grown Al/Fe/Al/ZnSe/GaAs(001) sample using synchrotron radiation. The Fourier-transformed XAFS spectra were fit up to four coordination shells simultaneously using theoretical spectra generated with FEFF 6. Our results reveal a small tetragonal distortion of the bcc α-Fe film lattice towards a contraction in the film growth direction (c=2.863 Å and a=2.874 Å; bulk a=2.867 Å). The anomalous tetragonal distortion is consistent with a model involving substantial interdifussion of Fe and Al, leading to Fe1−xAlx alloy formation localized in the interface regions.
Grazing Incidence X-Ray Diffraction Study of A Glass-Liquid Crystal Buried Interface
Authors: Martínez Miranda L. J.
Published: April 2011

We have used Grazing Incidence X-ray Diffraction to study the structure of a liquid crystal (LC) at the buried LC-glass interface in micrometer size LC films. This measurement is done in reflection mode through the glass substrate, which consists of a grating photolithographed onto a 0.2mm slide. This experiment was performed in beamline X22B of the National Synchrotron Light Source at Brookhaven National Laboratory, using 1.3776Å X-ray radiation. We have used both the glass and LC absorption properties to control the penetration depth of the beam into the LC film bulk. The ability to measure LC interfaces in this manner is essential to study any LC device, arid its response to applied fields.
Production and Characterization of Circularly Polarized Soft X-Rays for Materials Research at the ALS
Authors: Young Anthony T. , Kortright Jeffrey B. , Hussain Zahid , Martynov Vladimir , Padmore Howard A. , Renner Tim , Smith Neville V. , Warwick Tony
Published: April 2011

The experimental program at the Advanced Light Source to produce and characterize circularly polarized x-rays is described. A number of beamlines are either operating or under construction which produce circularly polarized light. Bend magnets, multilayer phase retarders, and insertion devices which directly produce circularly polarized radiation are described. These beamlines will have capabilities for both microscopy and high resolution spectroscopy. Measurements of the linear and circular polarization of these beamlines are also described.
Silicon L2, 3-Edge Xanes Study of Platinum Silicide Thin Films
Authors: Naftel S. J. , Sham T. K. , Das S. R. , Xu D.-X.
Published: April 2011

Platinum silicide films, with a typical thickness of several hundred Å, prepared on n-type Si(100) wafers by UHV mnagnetron sputter deposition followed by rapid thermal annealing, have been studied by Si L2,3-edge X-ray absorption near edge structure (XANES) using both total electron and total fluorescence yield detection. Samples of various annealing times were studied. XANES provides information on the electronic structure and morphology of the samples. By utilizing the sampling depth difference between the two detection methods, we can clearly see XANES data from each layer (eg. surface oxide, silicide) in the sample and can estimate the thickness of the oxide layer.
Excimer Laser Fabrication of Polycrystalline ZrO2 Layers
Authors: Starbov N. , Mednikarov B. , Mankov V. , Georgiev D. G. , Hanus F. , Kolev K. , Laude L. D.
Published: April 2011

Polycrystalline zirconia layers have remarkable low thermal conductivity and thermal expansion coefficient, high melting temperature and mechanical properties which are objects of interest in materials science. In this work thin polycrystalline zirconia films were obtained by two different excimer laser treatment ways. In the first one, pulsed laser deposition (PLD) is used to obtain directly as-deposited polycrystalline layers from a sintered, partially stabilized zirconia target. In the second one, excimer laser irradiation is used to crystallize previously electron gun-deposited amorphous zirconia films. Reflection high energy electron diffraction(RHEED) and low angle X-ray diffraction(LAXRD)-techniques were used to study the structure evolution of both types of films. In both cases, it is shown that cubic polycrystalline films are readily obtained.
Surface Roughening, Columnar Growth and Intrinsic Stress Formation in Amorphous CuTi Films
Authors: Hulsen U. v. , Thiyagarajan P. , Geyer U.
Published: April 2011

The growth of amorphous CuTi films, prepared by electron beam evaporation, is investigated by Scanning Tunneling Microscopy (STM), Small Angle Neutron Scattering (SANS) and in situ measurements of intrinsic mechanical stresses (ISM). In early growth stages the films develop compressive stresses and, with increasing film thickness, a crossover to tensile stresses. In the same thickness range the STM investigations show a change in the growth mode. Our experiments suggest a transition from planar growth with statistical surface roughening to columnar growth.
Nanocharacterization of Texture and Hillock Formation in Thin Al And Al-0.2%Cu Films for Thin-Film Transistors
Authors: Takatsuji H. , Tsuji S. , Kitahara H. , Tsujimoto K. , Kuroda K. , Saka H
Published: April 2011

The relation between the nanostructure of pure Al and Al-0.2 wt.% Cu thin films on glass substrates and anti-stress migration properties were investigated. These films were deposited on liquid-crystal display (LCD) grade glass substrate (550 x 650 mm) by means of two types of dc magnetron multi-chamber sputtering apparatus.

We developed the nanoindentation techniques to accelerate the characterization time for stress migration test. By AFM and cross-sectional TEM observations, we found an unusual three-layer structure in a Al-Cu thin film with strong anti-stress migration property.
Substrate Curvature Change Due to Morphological Instability of a Strained Epitaxial Surface Film
Authors: Jonsdottir F. , Freund L. B.
Published: April 2011

The curvature induced in the substrate of a film-substrate system as a result of an epitaxial mismatch strain in a film of nonuniform thickness is considered. In particular, the change in curvature of the substrate due to a transition in film surface morphology from a fiat to a wavy profile is determined numerically. It is found that the amount of curvature relaxation accompanying the instability is within the resolution of recently refined substrate curvature measurement methodologies.
Surface Structure and Morphology Modification of Silicon Layers Induced by Nanosecond Pulsed Laser Irradiation
Authors: Demchuk A.
Published: April 2011

The results of laser induced surface structure modifications utilizing time-resolved reflectivity measurements are presented for the pulsed laser irradiation (λ. = 1.06 μm and 0.53 μm) of thin polysilicon (poly-Si) layers of 0.1 μm, 0.45 μm and 1.0 μm in thickness on silicon substrates. It was shown that when the poly-Si layer of 0.1-0.45 thickness is totally molten, during a solidification, a large-grained structure having grain sizes exceeding the thickness of the molten Si layer is formed. At the same time, the time-resolved reflectivity changes its value nonmonotonically. This nonmonotonic behavior is due to the outcropping of growing grains onto the surface before the formation of a solid crystalline front as well as to the influence of the surface phenomena on the crystallization process.
Determination of Film Growth Rate and Surface Roughness using In-Situ Pyrometry
Authors: Yina Z. , Akkerman Z. L. , Smith W. , Gat R.
Published: April 2011

A model for the infrared radiation emitted by a film/substrate system has been developed which includes both the effects of interference in the growing film and of scattering from its rough growth surface. Predictions of the model for the time-dependence of the apparent temperature Tapp of the film/substrate system measured in-situ by both one-color and two-color infrared pyrometers are presented for the case of diamond growth on Si. Using this model, the following information can be obtained from in-situ pyrometric results in real time: the true temperature of the film/substrate system, the instantaneous film growth rate, and the rms surface roughness σ of the film.
Wear Resistant Amorphous PVD B-N-C Films for Tribological Applications
Authors: Knotek O. , Lugscheider E. , Barimani C. , Siry C. W.
Published: April 2011

Amorphous B-N-C films with a variety of properties were deposited by PVD-magnetronsputter-ion-plating. Compared to nonconductive reactive r.f. BN-targets the semiconductive behaviour of specially produced B4C-targets permitted a d.c. reactive or non-reactive mode of deposition. These films are characterized by high hardness with decreased coefficient of friction. A tribological evaluation by modified pin-on-disk outline the wear protection effects in tribosystems with metal counter part. This work was partially financed by the Commission of the European Community under Brite/EuRam contract BRE2-CT93-0451.
Effects of the Plasma Conditions on the Bonding Type in Carbon Nitride Thin Films
Authors: Mdndez J M. , Muhl S. , Gaona-Couto A. , Jiménez-Sandoval Sergio
Published: April 2011

Carbon nitride thin films have been prepared by plasma enhanced chemical vapour deposition of CH4 and N2 gas mixtures, by chemical transport from a hollow graphite cathode and by reactive sputtering of a high purity graphite target. The vibrational properties of the films have been studied by Fourier transform infrared spectroscopy (FTIR) and Raman microprobe spectroscopy. Optical emission studies from the plasmas were obtained in the range between 275 and 800 nm. Single, double and triple carbon nitrogen bonds were detected in the FTIR spectra by bands at 1230 cm-1, 1600 cm-1 and 2150 cm-1; their relative intensity being a function of the temperature of the species and the energy supplied to the plasma. A correlation was found between the nitrogen concentration in the films and the existance of strong emission lines of CN and N2+. In the sputtered samples, the substrate temperature and the amount of ion bombardment determined when the films were hard; i.e. Vicker's hardness values above 2500 HV. In the case of the sputtered samples, a temperature window was found which resulted in hard films.
Thermodynamic Analysis of Blanket and Selective Epitaxy of Sic on Si and SiO2 Masked Si
Authors: Gao Y. , Edgar J. H.
Published: April 2011

Thermodynamic analysis was conducted to determine the conditions necessary for the selective epitaxial growth (SEG) of SiC on SiO2 masked Si substrates, and these results were compared to blanket SiC epitaxy on plain Si. For blanket SiC epitaxy, proper deposition conditions leading to single phase SiC without Si or graphite codeposition were found. For SiC SEG, the additional constraint that no significant SiO2 mask etching should occur, was considered. Taken in combination, both the SiC deposition and the Si0 2 etching processes were analyzed to ensure meaningful subsequent experiments. All process parameters, i.e., temperature, C/Si, CI/Si and H2/Si in the gas mixture significantly affect the growth conditions when epitaxy is possible. Either providing more carbon than silicon in the gas sources or adding HCl helps to suppress Si codeposition. For SiC SEG, lower deposition temperature (e.g. less than 1400 K) should be used to avoid damaging the SiO2 mask.
Simultaneous Monitoring of Wafer- and Environment-States During Molecular Beam Epitaxy
Authors: Knopp K. J. , Ketterl J. R. , Christensen D. H. , Pearsall T. P. , Hill J. R.
Published: April 2011

We report the simultaneous monitoring of the environment-state and wafer-state during epitaxial crystal growth using a single real-time measurement. Atomic absorption spectroscopy (AAS) is used to monitor the incident molecular beam flux while UV reflectance (UVR) at 396 nm with an incident angle of 78° is used to monitor growth on the wafer. We have studied the utility of AAS/UVR monitoring of AlxGa1-xAs deposition: AlAs growing on GaAs, GaAs on AlAs, and superlattice growth. Additionally, optical multichannel spectroscopy (OMS) data were acquired throughout the growth of a distributed Bragg reflector (DBR). The relationship of the structure of the real-time OMS data to absorption, optical path length variation, and differential layer thickness variations is also discussed. Numerical simulations of the real-time wafer-state monitors using pseudodielectric constants, appropriate at a growth temperature of 579 °C, show good agreement with measured spectra.
Lateral grain growth in poly-Si films by gas flame high temperature annealing
Authors: Qu W. F. , Kitagawa A. , Masaki Y. , Suzuki M.
Published: April 2011

Poly-Si films with the preferential orientation to a random, a (100) and a (110) texture were annealed using a flat gas flame. Remarkable lateral grain growth of (111) grains was observed for poly-Si films with a random and a (110) texture, while in (100) texture films the growth of (100) grains predominated over other grains. There existed tensile stress in as-prepared films. Grains with different orientation were under a different tensile stresses, and such stress distributions on the orientation of grains were different for different textures. The tensile stress was found to become larger in grown grains after high temperature annealing, while the stress on shrunken grains decreased or turned to compressive stress after annealing. These results indicate that strain energy stored in grains is one of the important driving forces in secondary grain growth.
Delamination Trends of Underfill in Dca Assemblies
Authors: Sha Y. , Hui C.Y. , Kramer E. J. , Borgesen P. , Westby G.
Published: April 2011

Underfill delamination is one of the most common failure mechanisms for the Direct Chip Attach (DCA) assemblies. This paper, based on finite element and analytical analysis of stress concentrations, proposes the possible delamination trends of the underfill in the DCA assembly. The results explain well the recent experimental observations. The analysis suggests that good adhesion between underfill and solder joints might help compensate for the relatively poor adhesion of the underfill/passivation interfaces. It also suggests that voids in the underfill material may sometimes be detrimental.