bluuebunny/crossref_metadata_2025_split huggingface dataset:
In-Situ Stress Control During Sputter Deposition
Authors: Kola R. R. , Miller G. L. , Celler G. K. 
Published: March 2011

AbstractSputter-deposited tungsten thin films exhibit high intrinsic stress. This stress can result in both in-plane and out-of-plane distortion when the films are deposited on thin membrane structures such as x-ray masks. To minimize these distortions, intrinsic stresses in these absorber films have to be low and reproducible. Several groups have recently reported that by precisely controlling the sputter deposition conditions, W films with low stresses can be produced. However, the reproducibility is limited. We have built a novel acoustic resonance system, in which one electrode, mounted behind the mask membrane, monitors its position and simultaneously provides an electrostatic drive to keep it vibrating at its resonant frequency. For typical membranes and deposition conditions, vibrational modes in the 1–10 kHz range are observed. During tungsten deposition, sputtering pressure is varied in response to changes in the membrane resonant frequency, so that the film stress is minimized. We have made a systematic study of the microstructure and stress of W thin films using a variety of characterization techniques. We have shown the feasibility of depositing low-stress (<10 MPa) W films by in-situ stress monitoring and control of sputtering pressure. By using a proper combination of substrate heating and sputter power density (thermal engineering), the reproducibility of in-situ stress control is greatly improved. The present experimental results of in-situ stress control during W sputter deposition are very promising for the successful utilization of low stress (<10 MPa) W films as absorbers for x-ray masks.
Ultra-Soft X-Ray Absorption Spectroscopy: A Bulk and Surface Probe of Materials
Authors: Fischer Daniel A. , Mitchell Gary E. , Dekoven Benjamin M. , Yeh Alvin T. , Gland John L. , Moodenbaugh Arnie R. 
Published: March 2011

ABSTRACTDirect comparisons between the surface and bulk of diverse materials can be made by simultaneous electron yield (5 nm depth sensitivity) and fluorescence yield (200 nm) ultra soft x-ray absorption spectroscopy measurements utilizing a rapid sample interchange apparatus. For example the orientations of functional groups have been characterized at and near the surface of a series of model polymeric materials highlighting the chemical and molecular sensitivity of ultra soft x-ray absorption spectroscopy. In addition we discuss a bulk sensitive use of fluorescence yield to non destructively study a buried metal polymer interface. A second bulk sensitive example is the use of fluorescence yield oxygen K near edge x-ray spectroscopy as a method to determine the hole state density of high Tc materials.
Molecular Level Characterization of Thin Paraffinic Films Using NEXAFS Spectroscopy
Authors: Stevens Paul A. , Martella David J. 
Published: March 2011

ABSTRACTBecause near edge X-ray absorption fine structures (NEXAFS) are due to dipole transitions from core levels to unoccupied molecular orbitals, it is an ideal technique for obtaining molecular level information about the orientations of ordered species. Such information is important in assessing the relative importance of various intermolecular forces. For example in long chain molecules with bulky functional groups it is not clear a priori whether the attractive van der Waals forces will overcome the repulsive steric interactions to allow for ordering in thin films. To investigate this we have performed C-K edge NEXAFS spectroscopy studies of thin films of the paraffinic molecules C36H74 and (C18H37)2(NCO)C6H4CO2−+NH2(C18H37)2. The films were grown on a Si(111) surface covered with a native oxide. For the normal alkane, the spectra are dominated by three resolvable (Δhυ≈0.5 eV) features: one (C-H)* peak and two σ*(C-C) peaks. The polarization dependence of these peaks indicates that sub-250 Å C36H74 films have the chains of the molecules aligned along the surface normal. For ≈ 2000 Å films the molecular axes are inclined at angle of 32° with respect to the surface normal, in agreement with the crystalline structure determined by X-ray diffraction. In addition to the major structures of the alkane chains, the C-K NEXAFS of (C18H37)2(NCO)C6H4CO2−+NH2(C18H37)2 has a distinct π* peak due to the phenyl ring. Analysis of these resonances indicates that the C-C chains are also aligned along the surface normal, while the phenyl ring is inclined at an angle of 42° with respect to the normal. In conclusion NEXAFS spectroscopy has been used to show that, for the molecules studied, the attractive van der Waals interactions dominate the repulsive forces thus allowing the molecules to orient with their chains aligned along the surface normal in thin films formed on native oxide covered Si(111).
EXAFS Study of Co/Ag Multilayers
Authors: Foiles C. L. , Loloee R. , Morrison T. I. 
Published: March 2011

ABSTRACTCo EXAFS data for these Co/Ag multilayers exhibit no changes in basic form and obey a simple scaling with Co thickness down to 6Å. Over this same thickness range the giant magnetoresistance and the manner in which magnetization approaches saturation change substantially. These results indicate that local structural changes do not play a significant role in altering the magnetic properties of this multilayer system.
XAFS Characterization of Cu-Doped ZnO Films
Authors: Mikkelsen J. C. , Boyce J. B. , Bridges F. 
Published: March 2011

ABSTRACTThis paper describes x-ray absorption measurements made on 10 to 16-μm-thick films of ZnO, which contained 5 mol% CuO, and were grown by reactive sputtering. We compare our experimental near-edge and XAFS results to models for Cu-O phases and Cu incorporation into the ZnO lattice, and we conclude that roughly half of the Cu atoms are substitutional for Zn on the wurtzite lattice and the other half is in a highly disordered phase, which has an XAFS signature which is similar to disordered CuO. Our results are compared to other structural studies of Cu-doped ZnO materials.
Photoelectron Holography Of Platinum (111)
Authors: Petersen Barry L. , Terminello L. J. , Shirley D. A. 
Published: March 2011

ABSTRACTPlatinum atoms near a (111) single-crystal face have been imaged using photoelectron holography. Electron angular intensity patterns were collected at equally spaced wavenumbers from 6Å−1 to 12Å−1. Images of atoms near expected atomic positions are obtained from single-wavenumber analyses over the range of the data set. Positions are detected further from the emitter than we have seen previously, and we have also adopted a three dimensional means of representing the data in order to help understand the results. Twin image suppression and artifact reduction in the holographically reconstructed data set are obtained when images at different wavenumbers are correctly phase-summed. We are assessing the capability of the technique for rendering true three-dimensional structural information for unknown systems.
Phase Identification in Rapidly Solidified Al-In Alloys Using High Resolution Synchrotron Radiation Diffraction and Transmission Electron Microscopy
Authors: Tao J. , Aken D. C. Van , Bilello J. C. 
Published: March 2011

ABSTRACTA metastable (face centered) cubic form of indium has been identified in melt-spun Al-4.3at% indium using high resolution synchrotron radiation diffraction. The microstructure of the melt-spun ribbons consisted of particles of nominally pure indium dispersed in an aluminum matrix. These particles ranged in size from 10 nm to 1000 nm through the thickness of the ribbons. Only the smallest indium particles were identified as being cubic and these were observed in electron transparent regions of the as-spun ribbons. The cubic indium phase had the following orientation relationship with the matrix: [001]In′ // [001]Al and (100)In′ // (001)Al. The size distribution and average diameter of the cubic particles were obtained by quantitative analysis of the diffraction line profiles. These measurements were corroborated with transmission electron microscopy observations. The volume percent of the cubic indium phase was determined by matching simulations of the x-ray diffraction patterns with the diffracted intensities found experimentally. Approximately 10–20% of the indium is present in the cubic form and the remainder is the stable tetragonal phase.
Synchrotron X-Ray Radiation (CHESS) Study of Electric-Field Induced Changes in the Structure of Thermotropic Side-Chain Liquid Crystals
Authors: Bunning T. J. , McNamee S. G. , McHugh C. M. , Patnaik S. S. , Ober C. K. , Adams W. W. 
Published: March 2011

ABSTRACTSynchrotron radiation from the Cornell High Energy Synchrotron Source (CHESS) was used to probe the alignment kinetics of a class of thermotropic siloxane-based liquid crystals under the influence of an electric field. The high flux allows for real-time investigation of microstructural changes as a function of frequency and temperature. The packing behavior of a pentamethylcyclosiloxane ring with pendant biphenyl mesogens was thoroughly investigated. The director orientation parameter, Sd, typically increased with decreasing temperature and was not strongly affected by frequency. Electric-field induced changes in the director orientation were also monitored. Upon application of an electric field, the nematic system exhibited a tendency to pack in columns with short-range correlation of the mesogens. Column correlation lengths are examined as a function of temperature for two frequencies. At the low temperature end of the mesophase, a tendency for the mesogens to layer pack was observed.
Elucidating Structural Mechanisms for Cordierite Ceramic Formation using Synchrotron Radiation
Authors: Oversluizen Menno , Clark S. M. , Greaves G. N. 
Published: March 2011

ABSTRACTCr2O3 is a common nucleating agent useful for forming ceramics from oxide glasses. In this study we have used a variety of synchrotron radiation techniques to examine the atomic structure, crystallinity and microstructure of a magnesium alumino-silicate glass ceramic whose composition is close to that of the mineral cordierite, Mg2Al4Si5O13. X-ray Absorption spectra on the Cr K-edge have been performed with samples that were heat treated at different temperatures and times to examine the metamorphosis of the nucleating site. This study reveals that Cr3+ is always octahedrally coordinated with oxygen. In addition, the second nearest neighbour environment changes from an amorphous, single shell of Al/Si, but upon crystallisation, develops into a well ordered Al/Mg shell indicative of the formation of a dilute Cr spinel phase. Powder X-ray Diffraction (XRD) patterns, however, reveal that the major phase initially precipitated (˜900°C) is a stuffed quartz and from the lattice parameters that the composition is SiO2 -rich. With prolonged heat treatment a small quantity of a spinel phase emerges whose composition from its lattice parameter is close to MgAl2O4. Combined Small Angle X-ray Scattering (SAXS) and XRD establish that devitrification at these temperatures is associated with particles about 250 Å in size, on average. Energy dispersive powder diffraction patterns were collected in situ to observe changes in crystallinity with temperature and time. From these measurements the stuffed quartz phase identified at 900°C is found to be intermediate, being eventually replaced at higher temperatures by cordierite with a small quantity of spinel.
High-Resolution Core-Level Photoabsorption of Alkali Halides
Authors: Hudson E. , Moler E. , Zheng Y. , Kellar S. , Heimann P. , Hussain Z. , Shirley D. A. 
Published: March 2011

ABSTRACTThe X-ray Absorption Near Edge Structure (XANES) of single-crystal alkali halide salts have been measured at low temperature (T≈80 K). By employing the electron partial-yield detection technique, spectra of NaF, NaCI, and NaBr were obtained near the sodium K-edge and spectra of LiF, NaF, and KF were obtained near the fluorine K-edge. All spectra showed sharp features at the absorption threshold and broader absorption features extending 50–80 eV above threshold. The high energy resolution of the soft X-rays (ΔE/E ≈ 4000) allowed the detection of previously unobserved fine structure, particularly in the near-edge region. The narrow features below and just above threshold are attributed to core-level excitons. The intense, broader peaks further above threshold are assigned to single-electron scattering resonances. An ab initio multiple-scattering calculation is used to model the latter effect. Contributions from atomic multielectron excitations, estimated by a comparison to the K-edge photoabsorption spectrum of Ne in the gas phase, are found to be very small.
Characterization of Nanoscale Oxide and Oxyhydroxide Powders Using EXAFS Spectroscopy
Authors: Darab John G. , Linehan J. C. , Ma Y. , Matson D. W. 
Published: March 2011

ABSTRACTExtended x-ray absorption fine structure (EXAFS) spectroscopy has been used to determine the structural environment local to iron(III) and zirconium(IV) cations in respectively, nanoscale iron oxyhydroxide and nanoscale zirconium oxide powders. The iron oxyhydroxide powder, produced by the modified reverse micelle (MRM) technology, was found to have a short-range structure most similar to that of goethite (α-FeOOH). The short-range structure of the zirconium oxide powder, produced using the rapid thermal decomposition of solutes (RTDS) technology, was found to be a mixture of monoclinic zirconia and cubic zirconia environments.
Intrinsic Point Defects and Diffusion Processes in Silicon
Authors: Tan T. Y. 
Published: March 2011

ABSTRACTThis paper reviews recent progress in understanding the role of vacancies (V) and self-interstitials (I) in self and impurity diffusion in Si. Surface oxidation perturbs the thermal equilibrium concentration of point defects and analyses of the resulting effects on dopant diffusion showed that both V and I are present. Developments in experimental and theoretical works on Au diffusion in Si yielded a determination of the I-component and an estimate of the V-component of the Si self-diffusion coefficient. It is hoped that the I and V thermal equilibrium concentrations may be determined in the near future.A number of important physical aspects of the anomalous diffusion of P are now understood but a basically satisfactory model may need further work.
Structural Analyses of Metal/GaAs Contacts and Ge/GaAs and AlAs/GaAs Heterojunctions
Authors: Kuan T. S. 
Published: March 2011

ABSTRACTCross-sectional observations of interface structures at high magnification by TEM and STEM offer excellent lateral and depth resolution which are not available by other analytical techniques. This technique has recently been applied by the author to study metal/GaAs contacts and MBE-grown semiconductor heterojunctions. Specific observations on alloyed Au-Ni-Ge/GaAs and Pd/GaAs interfaces and on epitaxially grown Ge-GaAs and AlAs-GaAs superlattice structures are reviewed in this paper. The high spatial resolution of the energy dispersive x-ray analysis performed in a STEM is most useful in the studies of complicated metal/ GaAs interfacial reactions. However, to resolve on an atomic scale the compositional profile across a heterojunction, one has to rely on diffraction technique. The detailed analyses of these interfacial reactions and structures are shown to be essential to the understanding and control of the electronic behavior associated with these interfaces.
Interfacial Reactions of Nickel films on GaAs
Authors: Chen L.J. , Hsieh Y.F. 
Published: March 2011

ABSTRACTTransmission electron microscopy (TEM) and X-ray diffraction (XRD) were performed to study the interfacial reactions of Ni/GaAs contact system as a result of isothermal annealing and two step annealing. Ni2GaAs was observed to exhibit preferred orientation relationships with respect to GaAs substrate after 300–350°C annealing. The compound decomposed to NiAs and Ga-compounds after 400°C annealing. NiAs was also found to grow preferentially on GaAs. The step annealing was found to be ineffective in varying the morphological structure of interface.
The Characterisation of Interfacial Dislocation Structures
Authors: Clark W. A. T. 
Published: March 2011

ABSTRACTExperimental observation of many interfaces in metals indicate the presence of a dislocation-like structure. The geometrical basis for such a structure to exist is discussed, and the suitability of the transmission electron microscope (TEM) to characterise it considered. It is shown by reference to examples of grain and phase boundary structures in metals that such geometrical models may be used as a first step to predicting interfacial structures, and that the dislocations observed may play a role in thermo-mechanical behaviour of polycrystals. The general applicability of the applicability of the approach to non-metallic systems, such as semiconductors and ceramics is also indicated.
The Defect Structures of Fe9S10
Authors: Nguyen Thao A. , Hobbs Linn W. 
Published: March 2011

ABSTRACTThe defect structures of Fe9S10 have been studied by high-resolution transmission electron microscopy. Lattice images of the 3C and 4C superstructures and at least one other phase, which has not been previously reported, were observed. It has been found that the 4C superstructure transforms into the 3C superstructure rather than the MC phase as previously suggested. Intrinsic stacking faults in the sulfur sublattice and two different types of vacancy-ordering antiphase domains were also observed. Evidence from optical diffratograms of areas containing these defects suggests that complex features in the electron diffraction pattern may be artifactual.
Tem Observations of Grain Boundaries in Ceramics
Authors: Rühle M. 
Published: March 2011

ABSTRACTGrain boundaries in ZrO2-containing alumina, ZrO2, and in Ni1−yO (containing different impurities) were investigated by TEM including analytical studies. Quite frequently, interphases exist at the boundaries. The interphases are composed mainly by impurities present in the materials. The “width” of boundaries in Ni1-yO depends on intrinsic defects as well as on impurities; the dependency will be discussed. The observations are related to properties of the different ceramics.
Characterisation of Portland Cement Hydration by Electron Optical Techniques
Authors: Scrivener Karen L. , Pratt P. L. 
Published: March 2011

ABSTRACTIn the past the application of electron microscopy to cement hydration has been limited largely to the study of fracture surfaces in SEM, of ground cement in TEM and of polished sections in EMPA. Consequently the microstructure of bulk cement pastes is, as yet, ambiguous.The present work shows how techniques not previously used in the study of cement, an environmental cell on HVEM, preparation of ion beam thinned foils for STEM and BEI of polished surfaces in SEM, can give a more detailed view of the development of morphology in hydrating cement. Using a combination of electron optical techniques together with other methods a detailed characterisation of cement hydration can be made.
Combination of CBD and High Resolution with 400 kv
Authors: Suzuki S. , Honda T. , Kokubo Y. , Harada Y. 
Published: March 2011

ABSTRACTA new 400 kV electron microscope has been developed. It can combine high resolution (HR) image observation and convergent beam diffraction (CBD) analysis. The instrument is provided with a specimen height control (Z-control) system to get a wide range of illumination angles. In HR image observation, a resolving power of 0.18 nm is confirmed by ODM. Illumination angle of a converged beam can be changed from 1.0 mrad. to more than 10 mrad. using the Z-control system. Specimen height control is a very useful method to combine HR observation and CBD analysis.
Chemically Assisted ion-Beam Etching of Sol-Gel Derived Pzt, Plzt And LITaO3 Thin Films for Silicon Based Device Integration
Authors: Baude P. F. , Ye C. , Polla D.L. 
Published: March 2011

AbstractWet chemical, reactive ion etching and reactive ion-beam etching of sol-gel prepared PZT (54/46) [Pb(Zr,Ti)O3], Lanthanum doped PZT [PLZT (9/65/35)] and LiTaO3 have been investigated. Wet chemical etching using an HCI-HF solution, reactive-ion etching using a SF6 plasma and chemically assisted ion-beam etching (CAIBE) using a xenon plasma and chlorine reactive gas were used. Etch rates for each method were determined and the ability to define small features in the thin film ferroelectric was investigated. It was found that for structures smaller than approximately 20 × 20 μm2, chemically assisted ion beam etching provided by far the best results. 3 × 3 μm2 capacitor and 2 μm wide optical waveguide structures in PZT, PLZT respectively, were successfully fabricated using a CAIBE system. An etch depth monitor enabled accurate in-situ etch rate monitoring of the PLZT and PZT thin films.
Oriented Lead Zirconate Titanate thin Films: Characterization of Film Crystallization
Authors: Voigt James A. , Tuitle B. A. , Headley T. J. , Eatough M. O. , Lamppa D. L. , Goodnow D. 
Published: March 2011

AbstractThrough systematic variation of film processing temperature and time, we have characterized the pyrochlore to perovskite crystallization process of solution-derived PZT 20/80 thin films. The ≈3000 Å thick films were prepared by spin deposition using <100> single crystal MgO as the film substrate. By controlled rapid thermal processing, films at different stages in the perovskite crystallization process were prepared with the tetragonal PZT 20/80 phase being <100>/<001> oriented relative to the MgO surface. An activation energy for the conversion process of 326 kJ/mole was determined by use of an Arrhenius expression using rate constants found by application of the method of Avrami. The activation energy for formation of the PZT 20/80 perovskite phase of the solution-derived films compared favorably with that calculated from data by Kwok and Desu [1] for sputter-deposited 3500 Å thick PZT 55/45 films. The similarity in activation energies indicates that the energetics of the conversion process is not strongly dependent on the method used for film deposition.
Effects of Platinum Electrode Structures on Crystallinity and Electrical Properties of Mod-Prepared Pzt Capacitors
Authors: Eichorst Dennis J. , Baron Cynthia J. 
Published: March 2011

AbstractThe most common electrode structure for lead zirconium titanate (PZT) integrated on Si is platinum with a Ti adhesion layer. However, platinum hillocks that can lead to sample shorting may form during annealing. Careful selection of the Pt/Ti electrode architecture and deposition conditions can give nearly hillock-free electrodes. The phase development and ferroelectric properties of PZT prepared by metallo-organic decomposition (MOD) were studied as a function of Pt electrode structure and PZT composition. In addition to evaporated or sputtered Pt/Ti electrodes, Pt electrode layers were also prepared by MOD. MOD Pt layers showed no hillock formation but generally resulted in greater pyrochlore content in PZT capacitors.
Electron Microscopy Study of the Influence of the Adhesion Layer for Pt Electrode on the Microstructure of Sol-Gel Crystallized Pzt
Authors: Kaushik Vidya , Maniar Papu , Campbell Andrew , Jones Robert , Moazzami Reza , Mogab C. Joseph , Hance Robert , Pyle Ronald 
Published: March 2011

AbstractPZT ferroelectric capacitors are commonly fabricated using Pt electrodes. Crystallization in an oxygen ambient of sol-gel deposited PZT films is influenced by the nature of the adhesion layer used for the Pt electrode. Here we report results of the TEM investigation of the microstructures of PZT crystallized on Pt/Ti and Pt/TiO2 substrates. PZT films on either substrate show a two-phase microstructure consisting of larger perovskite grains and finegrained (<3nm) pyrochlore matrix. The perovskite grains are dense, free of any porosity and HRTEM shows the observed domains to be 90° <101> twins. EDS spectra detect a lower Pb/Ti ratio for the pyrochlore matrix compared to the perovskite grains. Differences between the two substrates consist of the perovskite to pyrochlore ratio and more importantly the perovskite grain size.