bluuebunny/crossref_metadata_2025 huggingface dataset:
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

Synchrotron 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

Cr2O3 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

The 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

Extended 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

This 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

Cross-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

Transmission 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

Experimental 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

The 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

Grain 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

In 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

A 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.
Recent Development in Hitachi Transmission Electron Microscope
Authors: Isakozawa Shigeto , Matsui Isao , Kamimura Shoji , Tonomura Akira
Published: March 2011

The 200 kV electron microscope has been extensively utilized as a high grade model for diversified applications. This paper reports image resolution available at present with the Hitachi 200 kV Electron Microscope Model H-800 and possible techniques for improving present resolution limit which depends on the aberrations of objective lens.
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

Wet 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

Through 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

The 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

PZT 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.
Preferred Orientations for Sol-Gel Derived Plzt Thin Layers
Authors: Tani Toshihiko , Xu Zhengkui , Payne David A.
Published: March 2011

PLZT thin layers were deposited onto various substrates by sol-gel methods, and crystallized under different conditions and substrate treatments. Relationships are given for the chemical characteristics of the substrate's surface and the preferred orientations which develop on heat treatment. A preferred (111) orientation always developed for perovskite crystallized on Pt layers which contained Ti on the surface. This was attributed to the formation of Pt3Ti and the role of heteroepitaxial nucleation and growth sites. In addition, a preferred (100) orientation was also obtained on unannealed Pt/Ti/SiO2/Si substrates which were free of Ti on the surface. This was attributed to self-textured growth with flat faces striving for minimum surface energy conditions. The results are discussed in terms of the importance of interfacial chemistry on the control of texture for crystallization of PLZT thin layers on coated substrates.
Solution Chemistry Optimization of Sol-Gel Processed Pzt Thin Films
Authors: Lockwood Steven J. , Schwartz R. W. , Tuitle B. A. , Thomas E. V.
Published: March 2011

We have optimized the ferroelectric properties and microstructural characteristics of sol-gel PZT thin films used in a CMOS-integrated, 256 bit ferroelectric non-volatile memory. The sol-gel process utilized in our work involved the reaction of Zr n-butoxide, Ti isopropoxide, and Pb (IV) acetate in a methanol/acetic acid solvent system. A 10-factor screening experiment identified solution concentration, acetic acid addition, and water volume as the solution chemistry factors having the most significant effects on the remanent polarization, coercive field, ferroelectric loop quality, and microstruntural quality. The optimal values for these factors were determined by runnig a 3-factor uniform shell design, modelling the responses, and testing the models at the predicted optimal conditions. The optimized solution chemistry generated 3-layer, 300-400 nm thick films on RuO2 coated silicon substrates with coercive fields of less than 25 kV/cm (a 40-50 % improvement over the original solution chemistry), a remanent polarization of 25-30 μC/cm, and a reduction in the pyrochlore phase content below observable levels.
Microstructural Characterization of Sol-Gel Derived Lead Titanate Deposited On Silica
Authors: Schwartz Joseph M. , Francis Lorraine Falter , Schmidt Lanny D.
Published: March 2011

The microstructural evolution of lead titanate prepared by a sol-gel method was examined using transmission electron microscopy (TEM) following treatments in air at progressively higher temperatures. TEM specimens were prepared by spin coating a film or dispersing particles onto specimen grids coated with SiO2 or SiO2 with a barrier layer. The effects of different barrier materials, thermal treatment conditions, and the addition of platinum particles were examined. Lead titanate formed crystalline perovskite at ∼550-600°C on all support materials examined. On SiO2 supports, the pyrochlore phase formed at lower temperatures and converted partially to perovskite at higher temperatures. Barrier layers of TiO2, A12O3 and polyimide prevented pyrochlore formation.
Formation of BaMgF4 Films on Pt/MgO, Si and GaAs Substrates
Authors: Aizawa Kouji , Ichiki Tatsuya , Ishiwara Hiroshi
Published: March 2011

Crystalline quality of BaMgF4 films grown on Pt/MgO, Si, and GaAs substrates either by solid phase crystallization (SPC) or by molecular beam epitaxy (MBE) has been investigated. In the SPC method, the films are deposited typically at 300°C in amorphous state and subsequently crystallized at temperatures higher than 500°C. It has been found from X-ray diffraction analysis that (010)-oriented films are grown on the three substrates by the SPC method, while that (011)- and (120)-oriented films are grown on respective (100)- and (111)-oriented substrates of Si and GaAs, when the MBE method is used at substrate temperatures around 500°C. These results show that the spontaneous polarization which is generated along a-axis of a BaMgF4 crystal, is not parallel to the film surface, only when the films are grown on (111) substrates by MBE.
Epitaxial Growth of Pt(001) Thin Films on MgO(001) Under Oxidizing Conditions
Authors: Cui G. , Buskirk P. C. Van , Zhang J. , Beetz C. P. , Steinbeck J. , Wang Z. L. , Bentley J.
Published: March 2011

Epitaxial Pt(001) thin films have been grown on MgO(001) substrates using dc magnetron sputtering with an Ar/O2 mixture at 700°C. The width (FWHM) of the rocking curve of the Pt(002) peak is between 0.16° and 0.20°, which is only 0.05° wider than that of the MgO (002) peak of the cleaved substrate. The film surface roughness is about 1 nm (rms) for a 240 nm thick Pt film. No grain structure could be observed using SEM. In contrast, the films deposited at 700 °C with pure Ar, have both Pt(111) and Pt(001) oriented growth, as shown by XRD Θ - 2 Θ scans, with the Pt(111) peak having the largest intensity. BaTiO3 epitaxial films have also been deposited on Pt(001)/MgO(001). The width (FWHM) of the rocking curve of the BaTiO3(200) peak is 0.4°. The surface morphology of the epitaxial BaTiO3(100) thin films on Pt(001)/MgO(001) is featureless. XRD pole figure measurements on Pt/BaTiO3/Pt trilayer shown a very good in-plane alignment of all layers. The epitaxial growth relationship was also confirmed by TEM electron diffraction and cross-section imaging. The Pt/BaTiO3/Pt epitaxial trilayer could serve as a prototype for ferroelectric capacitors and may be able to improve the electrical properties of the capacitors.
Examination of Titanium Oxides, Lead Oxides and Lead Titanates Using X-Ray Diffraction and Raman Spectroscopy
Authors: Madsen Lynnette D. , Weaver Louise
Published: March 2011

Single oxides (with titanium or lead) deposited as thin films by low pressure metalorganic chemical vapour deposition were investigated by x-ray diffraction and Raman spectroscopy. Examination of mixed oxides (titanates) and silicates were also carried out using these techniques. The crystallographic nature of these thin films were examined and comparisons made to their bulk counterparts. The deposition and anneal conditions 600 for producing cubic PbTiO3 films are discussed briefly.
Ferroeleciric Thin Films Intended for Electronic Device Applications
Authors: Patel A. , Logan E.A. , Nicklin R. , Hasdell N.B. , Whatmore R.W. , Uren M.
Published: March 2011

The need for integrated ferroelectrics as charge storage capacitors has increased dramatically not only for use in radiation hardened and commercial non-volatile memories, but also as possible high dielectric material suitable for capacitor applications. These properties combined with a thin film format, offer the capability of forming very compact capacitor structures suitable for MCM applications through Flip-Chip Bonding, or even integrated directly onto MMIC's. In this paper, the material PbZrxTi1-xO3, where x=l, 0.53, and 0.60 has been assessed. Thin films were produced using a sol-gel technique onto metallised thermally oxidised silicon. The effects on film microstructure and crystallinity with variation in the deposition process will be described. The best films were obtained by incorporating excess lead in the starting solutions, and also by the addition of acetylacetone which was used as a solution modifier. It will be demonstrated that fully perovskite films can be readily obtained at temperatures as low as 450°C. The films were normally 0.3-0.44μm thick with grain sizes of the order of 0.2μm. These films exhibited dielectric constants and loss in the range 170-800 and 1-3% respectively. Measurements upto 3MHz, indicated useful performance with low dispersion. The measured Pr and Ec were in the range 16-22μC/cm2, and 60-120kV/cm respectively.
Electrical Properties of Sol-Gel Pzt Thin Films for decoupling Capacitor Applications
Authors: Schwartz Robert W. , Dimos D. , Lockwood S. J. , Torres V. M.
Published: March 2011

The successful development of PZT thin films for decoupling capacitor devices places stringent requirements on the dielectric and leakage properties of the films. We have characterized these properties for PZT thin films with compositions near the morphotropic phase boundary prepared by a sol-gel process. Capacitors were fabricated from films with thicknesses varying from 0.4 to 1.2 µm. For zero applied bias, the dielectric constants of these films were in the range of 800 to 1200. The room temperature dielectric constant was observed to decrease by ∼ 25% with the application of a 5 V bias. We have also characterized the interrelationships between temperature, applied bias, and dielectric constant. The capacitors exhibited asymmetry in their leakage and breakdown characteristics with bias sign, as well as non-linear I-V behavior. Breakdown fields for undoped PZT 53/47 films were typically in the range of 750 kV/cm.

We have also studied the effects of La and Nb donor doping on the leakage behavior of PZT 50/50 thin films. Doping with 2 to 5 mol % of either La or Nb resulted in a reduction in film leakage current by a factor of 103. Leakage currents of the highly doped materials were approximately 2 × 10−9 A/cm2 under an applied field of ∼ 65 kV/cm at a temperature of 125×C.
Characterization of Au-Mediated a-Si:H Crystallization by In Situ Electrical Measurements
Authors: Pasa A. A. , Achete C. A. , Losch W. , Bauer G. H.
Published: March 2011

The Au-mediated crystallization of a-Si:H has been investigated by in situ electrical measurements and scanning electron microscopy. The a-Si:H structure was prepared by evaporation of Au thin films of different thicknesses (50 - 600 Å) onto intrinsic glow discharge deposited a-Si:H layers (≈ 5000 Å). A rapid increase in the electrical resistance was associated to the nucleation and growth of Si crystals inside the Au film. The growth process promotes the accumulation of Au at the Si grain boundaries forming a metallic network. This network controls the electric resistance at the end of the crystallization reaction. The kinetics of transformation has been studied by isothermal treatments over the 140 - 180 °C temperature range. An activation energy of 2.1 eV was measured. An analysis of resistance data obtained by constant heating rate treatments suggest the rupture of the network interconnections at T ≥ 170 °C. SEM pictures showing the formation of Au clusters confirmed this suggestion.
Morphological Transformations in the Crystallization of Tese-Halide Thin Films
Authors: Blatter A. , Ortiz C. , Adam J. L.
Published: March 2011

Amorphous Te3Se4 X (X = Br,I) thin films were prepared by RF sputter deposition where the halide is used to stabilize the amorphous structure. Crystallization in the films was induced by heating with pulsed laser irradiation, with an electron beam, and in a furnace. Crystallization was achieved when the halide was depleted which became more difficult the higher its mass and concentration. As a consequence, crystallization was highly anisotropic and confined to a thin surface layer with a lateral size to thickness ratio of up to 104. We observed various stages of the process. At low temperature, a spherulitic-type growth produced a low-dimensional branching morphology by non diffusive processes such as rotation. Increasing temperature favored the formation of higher dimensions with patterns typical for aggregation processes. At the highest temperatures material flow enabled the formation of three-dimensional structures. In case of the films with Iodine, facetted single crystals grew out of the surface to sizes many times larger than the original film thickness.
Dynamics of Thin Film NiTi Cantilevers on Si
Authors: Jardine A.Peter , Mercado Peter G.
Published: March 2011

Although the thermo-mechanical properties of NiTi are well known for bulk material, its deposition and utilization as a thin film are still in their earliest stages of research. The deposition of thin-films of Shape Memory Effect NiTi onto Si(100) wafers offers several advantages over bulk NiTi, including fast response times and comparatively large transformation forces. This has made it a promising candidate material as micro-actuators for Micro-Electro-Mechanical (MEMS) systems as well as for strain measurements. The cycling time for actuation was measured for a 20 μm free standing NiTi thin film cantilever. It was demonstrated that cycling frequencies of up to 50 Hz are achievable.
Phase Equilibria under Irradiation
Authors: Bellonw P. , Soisson F. , Grandjean Y. , Martin G.
Published: March 2011

A solid under irradiation is a far-from equilibrium system, and therefore phase equilibria in such a system cannot be assessed from equilibrium thermodynamics. Starting from a kinetic description which incorporates the various processes responsible for atomic diffusion (e.g. thermally activated jumps, replacement sequences or displacement cascades), the various possible steady-states can be identified analytically or numerically, as well as their kinetic evolution on varying the control parameters of the system (e.g. temperature, average composition, irradiation flux, cascade density …). Furthermore, from stochastic versions of the kinetic model, potentials governing the stationary probability distribution of states can be derived, allowing to build dynamical equilibrium phase diagrams.

Illustrating the above approach on the A2-B2 order-disorder transition, we have identified irradiation-induced two-phase state, cascade size and density effects on phase stability. By incorporating point defects, such description is well suited to study irradiation-induced segregation at sinks in concentrated alloys.
Formation of Sic Films on Silicon Field Emitters
Authors: Liu Jiang , Son U. T. , Stepanova A. N. , Christensen K. N. , Wojak G. W. , Givargizov E. I. , Bachmann K. J. , Hren John J.
Published: March 2011

Thin films of silicon carbide have been formed on silicon field emitters by chemical reaction with ethylene (C2H4) at temperatures of 850 to 950°C using ethylene gas pressures up to 5×10-3 Torr. By controlling the reaction time and temperature, we have made SiC coatings of from ∼20 A thickness to complete transformation of tips to SiC (1-2 μm). The electron diffraction pattern of the SiC layers show the expected 20% lattice mismatch with silicon and, for those emitters completely transformed, a polycrystalline 3C-SiC polytype was identified. The small radius of curvature was maintained for both the coated and completely transformed tips, although some defects and surface roughness was introduced during the treatments.
Ion Irradiated Amorphous Silicon: A Model Approach to Dynamics of Defect Creation and Annihilation
Authors: Shin Jung H. , Atwater Harry A.
Published: March 2011

The dynamics of defect annihilation and creation in amorphous silicon (a-Si) are measured in detail using defect-related changes in the electrical conductivity of a-Si A model is proposed which for the first time can track the complete time evolution of defect population across the activation energy spectrum with explicit dependence on irradiation and annealing parameters. The model is based upon experimental activation energy spectrum, bimolecular recombination kinetics, and on the notion of a maximum density of defect states beyond which no additional defects can be supported. The new model predicts transient dynamics in defect population and describes structure of the defect population in detail. Its predictions are in good qualitative agreement, and in reasonable quantitative agreement with experimental data.
Activation Energy for the C49-TO-C54 Phase Transition of Polycrystalline TiSi2 Films with under 30nm Thickness
Authors: Matsubara Y. , Noguchi K. , Okumura K.
Published: March 2011

The C49–to–C54 transition in TiSi2 was investigated by resistance measurement and x-ray diffraction technique. The resistance measurement showed that the C49–to–C54 transition has an activation energy strongly dependent on the titanium thickness. The energy increased with the thinning of the TiSi2, from 4.6±0.3 eV for TiSi2 formed with 50nm titanium, to 10.5±0.3 eV formed with 20nm titanium. Furthermore, x-ray diffraction result showed that (004)-oriented phase in C54 TiSi2 is responsible for the increase in activation energy. This orientation dependence of the activation energy probably originates from anisotropy in C54 crystal growth during the transition.
Morphology and Phase Metastability in the Al/Cu Thin Film Reaction.
Authors: McCarty E. D. , Hackney S. A.
Published: March 2011

The initial stages of the reaction between thin Al grains with an average diameter of 2 × 10−5mand sputter deposited, nanocrystalline Cu films has been studied in plan view using in situ transmission electron microscopy. At high reaction rates, the phase transformation in the Al grain resulting from the interdiffusion process is found to exhibit metastable growth morphologies characterized by negative curvature at the growth interface. The crystal structure of the initial phase formed in the Al grain under relatively high reaction rates is a metastable, orthorhombic distortion of the equilibrium body centered tetragonal θ phase. The distortion is found to vary with Al grain surface orientation. The degree of metastability can be experimentally correlated with the kinetics of the interdiffusion process as controlled by diffusion barrier thickness.
Evolution of Cubic FeSi2in Si upon Thermal Annealing
Authors: Lin X.X. , Desimoni J. , Bemas H. , Liliental-Weber Z. , Washburn J.
Published: March 2011

Cubic FeSi2precipitates were produced in Si (001) wafers by Fe implantation at room temperature, followed by ion beam-induced crystallization at 320°C, and their stability upon thermal annealing was examined by transmission electron microscopy. We found that the cubic phase remains relatively stable for a 650°C anneal, but the precipitates tend to change from an aligned to a twinned orientation with respect to the Si matrix. For higher temperature (800 and 900°C) anneals, most of the precipitates are transformed into β-FeSi2, accompanied by substantial precipitate coarsening. For platelet-shaped precipitates, the coarsening activation energy was determined to be 3.48 eV.
Reactions in Metal-Metalloid Multilayers
Authors: Sinclair Robert , Konno Toyohiko J.
Published: March 2011

We have studied the reactions at metal-metalloid interfaces using high resolution transmission electron microscopy, including in situ observation, and differential scanning calorimetry. There is contrasting behavior depending on the affinity for interaction or segregation. For reactive systems, compound formation ultimately results, but this can be preceded by solidstate amorphization. For non-reactive systems, crystallization of the metalloid is often achieved with nucleation and growth mediated by the metal phase.
Electron Microscopy Study of Cubic Boron Nitride Thin Films Grown by Ion -Assisted Pulsed Laser Deposition
Authors: Medlin D.D. , Friedmann T.T. , Mirkarimi P.P. , Mccarty K.K. , Mills M.M.
Published: March 2011

We present a microstructural study of boron nitride films grown by ion-assisted pulsed laser deposition. Fourier transform infra-red spectroscopy, electron energy loss spectroscopy, and electron diffraction measurements indicate that within the irradiated region of the substrate, the film consists of high fraction of cBN with a small amount of the turbostratic phase; outside of the irradiated region, only the turbostratic phase is detected. Conventional and high resolution electron microscopic observations of the boron nitride microstructure indicate that the cBN is in the form of twinned crystallites, up to 30 nm in diameter. We also observe particulates, formed by the laser pulse, that reduce the yield of cBN in the irradiated regions by shadowing local areas from the ion beam.
Mechanism of Intermetallic Phase Formation in thin Liquidsolid Diffusion Couples
Authors: Bartels F. , Muschik T. , Gust W.
Published: March 2011

Thin interconnection layers entirely consisting of intermetallic phases have been produced by joining planar Cu substrates coated with thin films of Sn. The thin layers of intermetallic phases are produced at low temperatures (<300°C) and short reaction times (5-120 s) in a process similar to reflow soldering by a liquid-solid reaction between Sn and Cu. Metallographic methods and X-ray analysis have been used to characterize the initial stages of the formation of the intermetallic phases. The reaction to form intermetallic phases via Cu dissolution and diffusion in the liquid Sn is very fast in the first 10-15 s when the liquid Sn is in contact with the Cu substrate along channels of liquid Sn between grains of the intermetallic phases. The stability of these narrow channels of liquid Sn is discussed in terms of the wettability of different types of grain boundaries in the textured layer of intermetallic phases.
Phase Transformations in Cu-Zr Multilayers
Authors: Weihs T.T. , Barbee T.T. , Wall M.M.
Published: March 2011

A study of phase transformations is reported for Cu-rich, Cu-Zr multilayer foils that were synthesized using magnetron sputter deposition and annealed using a differential scanning calorimeter. The foils range in composition from 1.6 at% to 9.0 at% Zr and consist of alternate layers of polycrystalline Cu and Zr. Differential scanning calorimetry, X-ray analysis and electron microscopy were used to examine three distinct reactions in the foils: a mixing and an amorphization of the Cu and the Zr, a crystallization to the metastable intermetallic, Cu51Zr14, and a transformation of the Cu51Zr14 phase into the equilibrium phase, Cu9Zr2. The asdeposited layering remained stable during the first two reactions and then broke down in the third reaction as large grains of Cu9Zr2 encompassed the smaller Cu grains. The heats of the reactions and the activation energies of these reactions are measured and are compared to values reported for bulk samples. The measured heats support the observation that amorphous Cu-Zr alloys phase separate and provide evidence that mixing and short range ordering produce 3.5 times more heat than long range ordering when Cu and Zr react and form Cu51Zr14.
Structural Properties of Anisotropic PtCo(001) and PtFe(001) Thin Films on MgO(001)
Authors: Lairson Bruce M. , Visokay Mark R. , Brennan Sean B. , Sinclair Robert , Clemens Bruce M.
Published: March 2011

We report structural properties of PtFe and PtCo intermetallic compounds with perpendicular magnetic anisotropy and a preferred c-axis orientation perpendicular to the film plane, formed from initially epitaxial multilayers. These materials represent particular cases of a more general class of anisotropic magnetic compounds with the CuAu(1) natural superlattice structure. They possess high magneto-optic Kerr rotations and magnetizations, suggesting them as likely candidates for magneto-optic and perpendicular magnetic recording media.
Epitaxial Growth of Rare Earth Silicides on (111)Si
Authors: Lee T. L. , Sue W. D. , Lin J. H. , Luo C. H. , Chen L. J.
Published: March 2011

Epitaxial YSi2-x, TbSi2-x, and ErSi2-x. have been grown on (111)Si by solid phase epitaxy in ultrahigh vacuum deposited rare earth (RE) metal thin films on silicon. The evolution of vacancy ordering and defect structure in epitaxial RE silicide thin films on (111)Si have been studied by both conventional and high resolution transmission electron microscopy.

Additional superlattice spots located at 1/3 <2110> in the diffraction pattern of RESi2-x, are attributed to the formation of ordered vacancy in the Si sublattice planes. The splitting of extra diffraction spots is correlated to the formation of an out-of--step structure. Streakings of the split diffraction spots in the diffraction pattern are attributed to the presence of an out-of-step structure with a range of M values. For YSi2-x and ErSi2-x, the M was found to settle down to a constant value after high temperature and/or long time annealing. For TbSi2-x, M is equal to 5 throughout the annealing.

Planar defects in RESi2-x films were analyzed to be stacking faults on {1010} planes with 1/6<1213> displacement vectors. The size and density of stacking faults were found to increase and decrease, respectively, with annealing temperature and/or annealing time.
X-Ray Spectroscopic Studies of Organo-Metallic Vapor Phase Epitaxial Growth
Authors: Brennant S. , Fuosst P. H. , Kisker D. W. , Lamelast F. J. , Imperatori P. , Stephenson G. B.
Published: March 2011

Chemical Vapor Deposition often occurs under conditions unsuitable for simultaneous monitoring using electron-based structural probes. This is due to the near-atmospheric pressure which exists during growth. While some work has been performed using optical probes, the typically high temperatures in the reactor vessel and the vastly longer wavelength of visible light versus the features being studied has hampered its utility as a structural probe. Over the past several years x-rays from synchrotron storage rings have been used to study the surface structure of growing materials. These studies have been primarily scattering studies. In this paper we explore the use of x-ray spectroscopic studies for the analysis of film growth. We have focused on three areas: the measurement of reactor vessel profiles using x-ray fluorescence; The measurement of gas-phase Extended X-ray Absorption Fine Structure (EXAFS), and the measurement of EXAFS of adsorbed species on the substrates.
Significance of a Nucleation Layer in Inhibiting Interfacial Pitting in InAs Films Grown by Two-Step MOVCD on (100) Inp Substrates
Authors: Ballal A. K. , Salamanca-Riba L. , Partin D. L.
Published: March 2011

In this paper, we study the significance of a low temperature nucleation layer and its role in inhibiting interfacial pitting vapor deposition. Transmission electron microscopy and scanning electron microscopy studies show that severe interfacial pitting occurs for thin nucleation layers of average thicknesses of 200Å and 400Å. For these average nucleation layer thicknesses we have found that the InAs islands do not cover the entire substrate surface during the low temperature deposition. Hence, when the film is heated to a higher temperature for the growth of the remainder of the film severe pitting at the heterointerface is produced. The thermal etchpits are sources of threading dislocations, which propagate to the surface of the film. For thicker nucleation layers we observe no interfacial pitting. Our studies show that there is an optimum nucleation layer thickness for which high quality InAs films with reduced threading dislocation densities and relatively high electron mobilities are obtained. Both electrical and structural studies suggest that ∼ 800Å is an optimum thickness of the low temperature nucleation layer.
Kinetic Control of CaF2 on Si(111) Growth Morphology
Authors: Denlinger J. D. , Rotenberg Eli , Hessingert U. , Leskovar M. , Olmstead Marjorie A.
Published: March 2011

Thin (0.5 to 8 triple layer) CaF2 on Si(111) films were grown using molecular beam epitaxy (MBE) and characterized using an in situ combination of x-ray photoelectron spectroscopy (XPS) and componentresolved x-ray photoelectron diffraction (XPD). We identified surface, bulk-like, and interface F and Ca core-level shifts and used the XPS shifts and XPD modulations to identify the growth modes as a function of the kinetic parameters of CaF2 flux and Si temperature. We identify 3 distinct regimes: (i) for high temperatures and flux we find a complete reacted F-Ca-Si layer, overlaid by 2 layer high islands which coalesce, followed by layer-by-layer growth, (ii) for high temperature and low flux, we find the reacted F-Ca-Si layer to be partially covered with thick islands, and (iii) for low temperatures we find an incompletely occupied F-Ca-Si layer followed by layer-by-layer growth. In all cases we find the buried interface to be structurally identical to the unburied F-Ca-Si layer
Stm Imaging of Adsorbed Trimethylgallium on GaAs(001)-(2×4)
Authors: Avery A. R. , Mayne A. J. , Goringe C. M. , Owen J. H. G. , Smith C. W. , Schweitzer M. O. , Jones T. S. , Briggs G. A. D. , Weinberg W. H.
Published: March 2011

Scanning tunnelling microscopy (STM) has been used to image the adsorption of trimethylgallium (TMGa) on GaAs(001)-(2×4) surfaces prepared in situ by molecular beam epitaxy (MBE). Filled states images of the clean surface are dominated by (2×4) unit cells containing only two As dimers. Upon exposure of this surface to TMGa at room temperature, bright oval-shaped features are observed which are centred on the arsenic dimers of the unit cell. These arise from tunnelling from Ga-C bonds of the adsorbed molecules. At low coverages, preferential adsorption on unit cells adjacent to occupied sites along the [110] direction is observed. A detailed statistical analysis of a large number of adsorption sites shows that there is an increased probability of about 24% for adsorption next to a (2×4) unit cell which is occupied relative to an unoccupied one.
Steps of Surface Etching and Carbon Deposition on the Graphite Basal Plane
Authors: Chu Xi , Chan Vincent , Schmidt Lanny D.
Published: March 2011

The reactions of O2, H2O, CO2, NO2, NO, and N2O with single crystal graphite between 400 and 700°C have been studied by STM to obtain quantitative kinetics by measuring the number and size of monolayer pits on the basal plane versus temperature and time. At low temperature the reaction initiates exclusively from the point defects on the basal plane to form monolayer pits. The shape of the monolayer pits vary from nearly triangular to hexagonal to circular depending on the rate of the reaction and the reacting gases. The sizes of the monolayer pits grow linearly with reacting time. The monolayer reaction rates follow the order of RNO2 > RN2O > RNO > RO2 > RH2O > RCO2. The activation energies for reactions with O2, H2O, NO2, NO, and N2O, are determined to be 127, 205, 60, 89, and 74 kJ/mol respectively.

Carbon deposition from hydrocarbons onto surfaces of single crystal graphite has been examined to study the fundamental steps of chemical vapor deposition. Uniform monolayer pits on graphite surface were first produced by reactive etching of freshly cleaved single crystal of graphite in oxygen and carbon was then made to deposit exclusively on these defects in the basal plane. Carbon vapor deposition forms unique structures around the monolayer steps. By measuring the sizes of structures on steps in various gases versus temperature and pressure, the kinetics of hydrocarbon decomposition and the role of surface diffusion can be determined.
Kinetics of Epitaxial Layer Growth from Silane on (100) Silicon
Authors: Greve D. W.
Published: March 2011

Low temperature growth of silicon from silane is required in devices such as germanium- silicon HBTs and multiple quantum well structures for infrared detectors. Understanding the silicon growth kinetics is an important step in developing a complete model for incorporation of other species such as germanium, boron, and phosphorus. In this paper, we show that a wide range of recent data can be well explained by a model which includes the effect of hydrogen carrier gas and is based on a simple two- step reaction sequence for silane decomposition. Gas phase reactions and gas phase transport limits appear unimportant at least up to 1 Torr total pressure.