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Organic phase structure plays an important role in solute extraction energetics and phase behavior of liquid-liquid extraction (LLE) systems. For a binary extractant (amphiphile)/solvent mixture of relevance to LLE, we find that the organic phase mesostructuring is consistent with extractant concentration fluctuations as the compositional isotherm traverses the Widom line above its liquid-liquid critical point. This reveals a different mechanism for the well-documented heterogeneities in LLE organic phases that are typically attributed to micellization.

The advent of high-speed x-ray photon correlation spectroscopy now allows the study of critical phenomena in fluids to much smaller length scales and over a wider range of temperatures than is possible with dynamic light scattering. We present an x-ray photon correlation spectroscopy study of critical fluctuation dynamics in a complex fluid typical of those used in liquid-liquid extraction (LLE) of ions, dodecane-DMDBTDMA with extracted aqueous $\mathrm{Ce}({\mathrm{NO}}_{3}{)}_{3}$. We observe good agreement with both static and dynamic scaling without the need for significant noncritical background corrections. Critical exponents agree with 3D Ising values, and the fluctuation dynamics are described by simple exponential relaxation. The form of the dynamic master curve deviates somewhat from the Kawasaki result, with a more abrupt transition between the critical and noncritical asymptotic behavior. The concepts of critical phenomena thus provide a quantitative framework for understanding the structure and dynamics of LLE systems and a path forward to new LLE processes.

Dissolution is critical to nanomaterial stability, especially for partially dealloyed nanoparticle catalysts. Unfortunately, highly active catalysts are often not stable in their reactive environments, preventing widespread application. Thus, focusing on the structure–stability relationship at the nanoscale is crucial and will likely play an important role in meeting grand challenges. Recent advances in imaging capability have come from electron, X-ray, and other techniques but tend to be limited to specific sample environments and/or two-dimensional images. Here, we report investigations into the defect-stability relationship of silver nanoparticles to voltage-induced electrochemical dissolution imaged in situ in three-dimensional detail by Bragg coherent diffractive imaging. We first determine the average dissolution kinetics by stationary probe rotating disk electrode in combination with inductively coupled plasma mass spectrometry, which allows in situ measurement of Ag+ ion formation. We then observe...

In unconventional shale plays, the production profile varies dramatically within an extremely short period of time. Wells often produce at extremely high rates when initially completed and deplete rapidly before reaching production plateaus. This rapidly changing production profile presents a significant challenge to engineers designing artificial lift systems. Because of the method's flexibility and tolerance to a variety of producing conditions, gas lift has become a popular artificial lift choice in these wells. To achieve optimal system performance, engineers often design gas lift installations to produce up the casing early in the well's life. This configuration minimizes pressure losses in the production string, enabling deep injection, improved drawdown, and higher flow rates. As the wells deplete and the production rates decline, the wells must be converted to tubing flow to ensure well stability. As the wells further deplete, they are often converted to intermittent gas lift. Unfortunately, it is not feasible to produce wells with tubing flow gas lift or intermittent gas lift with the typical downhole equipment configuration used in annulus flow wells. Therefore, transitioning to these late-life artificial lift configurations has required a workover rig. A novel downhole equipment configuration was developed to eliminate the need for a workover rig when transitioning from annulus flow to tubing flow gas lift. Side-pocket mandrels with a special pocket porting configuration were selected to enable annulus flow with enhanced gas passage early in the well's life. To transition from annulus flow to tubing flow, the slickline-retrievable valves were pulled and replaced with reverse-flow gas lift valves. A field trial was conducted to demonstrate and test this completion concept. While more investigation is required to justify full field implementation, the initial results have been promising. This project demonstrated that it is feasible to produce wells in annulus flow, tubing flow, and even intermittent gas lift with a single completion using readily available, off-the-shelf artificial lift equipment.

Using in situ grazing-incidence x-ray scattering, we have measured the diffuse scattering from islands that form during layer-by-layer growth of GaN by metal-organic vapor phase epitaxy on the (1010) m-plane surface. The diffuse scattering is extended in the (0001) in-plane direction in reciprocal space, indicating a strong anisotropy with islands elongated along [1 $\overline{2}$ 10] and closely spaced along [0001]. This is confirmed by atomic force microscopy of a quenched sample. Islands were characterized as a function of growth rate G and temperature. The island spacing along [0001] observed during the growth of the first monolayer obeys a power-law dependence on growth rate G$^{-n}$, with an exponent $n = 0.25 \pm 0.02$. Results are in agreement with recent kinetic Monte Carlo simulations, indicating that elongated islands result from the dominant anisotropy in step edge energy and not from surface diffusion anisotropy. The observed power-law exponent can be explained using a simple steady-state model, which gives n = 1/4., Comment: 4 pages, 5 figures, ancillary material includes Supplement material (pdf) of 4 pages, 5 figures with details of analysis

Mesoscale thermal transport is of fundamental interest and practical importance in materials such as thermoelectrics. Coherent lattice vibrations (acoustic phonons) govern thermal transport in crystalline solids and are affected by the shape, size, and defect density in nanoscale materials. The advent of hard x-ray free electron lasers (XFELs) capable of producing ultrafast x-ray pulses has significantly impacted the understanding of acoustic phonons by enabling their direct study with x-rays. However, previous studies have reported ensemble-averaged results that cannot distinguish the impact of mesoscale heterogeneity on the phonon dynamics. Here we use Bragg coherent diffractive imaging (BCDI) to resolve the 4D evolution of the acoustic phonons in a single zinc oxide rod with a spatial resolution of 50 nm and a temporal resolution of 25 picoseconds. We observe homogeneous (lattice breathing/rotation) and inhomogeneous (shear) acoustic phonon modes, which are compared to finite element simulations. We investigate the possibility of changing phonon dynamics by altering the crystal through acid etching. We find that the acid heterogeneously dissolves the crystal volume, which will significantly impact the phonon dynamics. In general, our results represent the first step towards understanding the effect of structural properties at the individual crystal level on phonon dynamics.

Bragg coherent x-ray diffractive imaging is a powerful technique for investigating dynamic nanoscale processes in nanoparticles immersed in reactive, realistic environments. Its temporal resolution is limited, however, by the oversampling requirements of three-dimensional phase retrieval. Here, we show that incorporating the entire measurement time series, which is typically a continuous physical process, into phase retrieval allows the oversampling requirement at each time step to be reduced, leading to a subsequent improvement in the temporal resolution by a factor of 2-20 times. The increased time resolution will allow imaging of faster dynamics and of radiation-dose-sensitive samples. Furthermore, this approach, which we call "chrono CDI," may find use in improving the time resolution in other imaging techniques.

In this paper we describe a setup for x-ray scattering experiments on complex fluids using a liquid jet. The setup supports Small and Wide Angle X-ray Scattering (SAXS/WAXS) geometries. The jet is formed by a gas-dynamic virtual nozzle (GDVN) allowing for diameters ranging between 1 μm and 20 μm at a jet length of several hundred μm. To control jet properties such as jet length, diameter, or flow rate, the instrument is equipped with several diagnostic tools. Three microscopes are installed to quantify jet dimensions and stability in situ. The setup has been used at several beamlines performing both SAXS and WAXS experiments. As a typical example we show an experiment on a colloidal dispersion in a liquid jet at the X-ray Correlation Spectroscopy instrument at the Linac Coherent Light Source free-electron laser.

In situ synchrotron X-ray scattering and fluorescence techniques were used to simultaneously observe the evolution of the strain and composition of a growing crystal surface in real time. Control of the X-ray incidence angle allows us to obtain high surface sensitivity. We studied metal organic chemical vapor deposition (MOCVD) of epitaxial PbZr x Ti 1-x O 3 (PZT) onto SrTiO 3 (001) substrates under various growth conditions. We observe a strong increase in Zr incorporation as strain relaxation occurs, consistent with the effect of compositional strain on the thermodynamic driving force for growth.

A multilayer nanostructure of 728 alternating WSi{sub 2} and Si layers with thicknesses gradually increasing from 10 to {approx}58 nm according to the Fresnel zone-plate formula has been fabricated using dc magnetron sputtering. This structure was analyzed with a scanning electron microscope (SEM) and tested with 19.5-keV synchrotron X-rays after sectioning and polishing. Line focus sizes as small as 30.6 nm have been achieved using a sectioned multilayer in transmission diffraction geometry.

Summary A study of the metallurgy and manufacturing techniques of a group of eight astrolabes (seven from Lahore, one attributed to India) using non-destructive methods has produced the earliest evidence for systematic use of high-zinc (α + β) brass. To produce this alloy, the brass industry supplying the Lahore instrument makers must have co-melted metallic copper and zinc. This brass-making technology was previously believed to have been developed on an industrial scale in the nineteenth century in Europe. This work hypothesizes that this technology was used in Lahore on an industrial scale as early as ad 1601. In addition, this work hypothesizes that the α + β brass alloy was used specifically for its ease in manufacturing the thin sheet brass required for astrolabe-component manufacture.

In situ synchrotron X-ray scattering was used to observe both the growth of PbTiO3 films by metal-organic chemical vapour deposition and the behaviour of the ferroelectric phase transition as a function of film thickness. The dependences of growth mode and deposition rate on gas flows and substrate temperature were determined by homoepitaxial growth studies on thick films (50 nm). These studies facilitated the growth of thin coherently strained PbTiO3 films on SrTiO3 (001) substrates, with thicknesses ranging from 2 to 42 nm. Experiments on the ferroelectric phase transition as a function of film thickness were carried out in these films under controlled mechanical and electrical boundary conditions.

We have used in situ synchrotron x-ray scattering to investigate PbTiO3 films grown epitaxially on SrTiO3 (001) substrates. When the films are cooled below a thickness-dependent Curie temperature, the ferroelectric phase forms as 180° stripe domains with a well-defined period. With further cooling, the period changes fairly abruptly from a lower to a higher value, suggesting a transition between two stripe domain phases. The periods of both stripe phases are observed to depend on the square root of film thickness, in agreement with theory.

As part of a program to understand and control the structure of ferroelectric thin films grown by metal organic vapor phase epitaxy (MOVPE), we have used X-ray scattering to observe the surface structure of PbTiO 3 films during and following growth. Moderately high energy (24 keV) X-rays are used to penetrate the chamber walls for in situ measurements in the high-temperature, reactive MOVPE environment. Performing measurements in situ allows us to study the growth process in real time, to control the thickness of the films to sub-unit-cell accuracy, to observe the surface structure in equilibrium with the vapor, and to preserve film stoichiometry during high-temperature study by maintaining an overpressure of PbO. While the higher X-ray energy also permits a large volume of reciprocal space to be mapped, it presents challenges for surface scattering due to the small critical angle. Examples of results will be presented from studies of surface structure dynamics, crystal growth, and ferroelectric stripe domains in thin films.

Dealloying is a process whereby selective dissolution results in a porous, strained structure often with new properties. The process is of both intrinsic and applied interest, and recently has been used to make highly active catalysts. The porosity has been studied using electron microscopy while the dealloying-induced strain has been studied at the ensemble level using X-ray diffraction. Despite the importance of local, for example, at the individual particle or grain level, strain in controlling the properties of the dealloyed material, it remains unresolved due to the difficulty of imaging 3D strain distributions with nanometer resolution in reactive environments. This information could play an integral role in understanding and controlling lattice strain for a variety of applications. Here, 3D strain distributions in individual nanoparticles and thin film grains in silver–gold alloys undergoing nitric acid-induced dealloying are imaged by Bragg coherent diffractive imaging. Particles exhibit dramatic changes in their local strains due to dealloying but grains do not. The average lattice in both grains and particles contracts during dealloying. In general, the results reveal significant dealloying-induced strain heterogeneity at the nanoscale in both isolated and extended samples, which may be utilized to develop advanced nanostructures for a variety of important applications.

We present real-time X-ray scattering studies of the influence of silicon on the homoepitaxial growth mode of GaN grown by metal-organic vapor-phase epitaxy. Both annealing of Si-doped GaN and surface dosing of GaN with disilane are shown to change the mode of subsequent growth from step-flow to layer-by-layer. By comparing the growth behavior induced by doped layers which have been annealed to that induced by surface dosing, we extract an approximate diffusion coefficient for Si in GaN of 3.5 ×10 −18 cm 2 / s at 810°C.

Nominally 2{sup o} vicinal GaN(0001) surfaces exhibit monolayer-height steps at 990{sup o}C in the metal-organic chemical vapor deposition environment. Real-time x-ray scattering observations at 715--990{sup o}C indicate that there is a tendency for step bunching during growth. Below 850{sup o}C, step bunches nucleated during growth remain and coarsen after growth, while above 850{sup o}C, the surface reverts to monolayer-height steps after growth. Surfaces vicinal toward the {l_brace}1{bar 1}00{r_brace} and the {l_brace}11{bar 2}0{r_brace} planes exhibit similar behavior. We suggest a simple equilibrium surface orientational phase diagram for vicinal GaN(0001) that is consistent with these observations.

Out-of-plane structures of the GaN (0 0 0 1) surface in the metal-organic chemical vapor deposition (MOCVD) environment have been determined using in situ grazing-incidence X-ray scattering. We measured 11 2 l crystal truncation rod intensities at a variety of temperatures and ammonia partial pressures on both sides of the 1×1 to ( 3 ×2 3 ) R 30° surface phase transition. The out-of-plane structure of the ( 3 ×2 3 ) R 30° phase appears to be nearly independent of temperature below the transition, while the structure of the 1×1 phase changes increasingly rapidly as the phase transition is approached from above. A model for the structure of the 1×1 phase with a partially occupied top Ga layer agrees well with the data. The observed temperature dependence is consistent with a simple model of the equilibrium between the vapor phase and the surface coverage of Ga and N. In addition, we present results on the kinetics of reconstruction domain coarsening following a “quench” into the ( 3 ×2 3 ) R 30° phase field.

This paper presents the design of a robot-based detector manipulator for microdiffraction applications with a hard X-ray nanoprobe instrument system being constructed at the Advanced Photon Source (APS) for the Center for Nanoscale Materials (CNM) being constructed at Argonne National Laboratory (ANL). Applications for detectors weighing from 1.5 to 100 kg were discussed in three configurations.

We have fabricated partial Multilayer Laue Lens (MLL) linear zone plate structures with thousands of alternating WSi2 and Si layers and various outermost zone widths according to the Fresnel zone plate formula. Using partial MLL structures, we were able to focus hard X-rays to line foci with a width of 30 nm and below. Here, we describe challenges and approaches used to bond these multilayers to achieve line and point focusing. Bonding was done by coating two multilayers with AuSn and heating in a vacuum oven at 280–3001C. X-ray reflectivity measurements confirmed that there was no change in the multilayers after heating to 3501C. A bonded MLL was polished to a 5–25mm wedge without cracking. SEM image analyses found well-positioned multilayers after bonding. These results demonstrate the feasibility of a bonded full MLL for focusing hard X-rays. r 2007 Published by Elsevier B.V.

We present a simulation result of the focusing performance of a multilayer Laue lens (MLL) with imperfections. Imperfections we have studied correspond to deviations of sequence of layers in the fabricated structure from the zone plate law. The actual sequence of layers of the MLL is measured by scanning electron microscope (SEM), and fitted by second order polynomials. X-ray characterization of the MLL structures is performed using coherent X-rays at the Advanced Photon Source. We observe very good agreement between experiment and simulation. This demonstrates that our simulation method can serve as an efficient tool to characterize the focusing performance of MLLs with imperfections, and thereby allows us to provide feedback following deposition and fabrication of the MLL structures and optimization of focusing structures prior to X-ray characterization.

We report observations of the dynamics of the exact structure factor (speckle pattern) during phase separation in a sodium borosilicate glass, measured using intensity fluctuation spectroscopy with a coherent x-ray beam. Nonequilibrium fluctuations in the structure factor are analyzed using a two-time correlation function to extract the time-dependent and wave-number-dependent correlation time. The behavior of the correlation time is in agreement with a scaling law previously found in simulations. {copyright} {ital 1998} {ital The American Physical Society }

{ital In situ} small-angle x-ray scattering studies of the spinodal decomposition kinetics in an AlZn alloy at the critical composition have been performed with a time resolution of 10ms. The kinetics of fluctuation relaxation above the critical point merges smoothly with the early-stage kinetics of fluctuation growth below T{sub c}. Strong nonlinearities are present at the earliest times measured, even above the critical point. The nonlinear theory of Langer, Bar-on, and Miller [Phys.Rev.A {bold 11}, 1417 (1975)] quantitatively fits the data with reasonable thermodynamic and transport parameters. {copyright} {ital 1997} {ital The American Physical Society}

The phase formation sequences of Si-P alloy thin films with P concentrations between 20 and 44 at.% have been studied. The samples were annealed at progressively higher temperatures and the newly formed phases were identified both after each annealing step by ex-situ conventional X-ray diffraction (XRD) and continuously by in-situ synchrotron XRD. It was found that Si was the only phase to form in a sample with 20at.%P since the evaporation of P at the crystallization temperature prevented phosphides from forming. For a sample with 30at.%P, the Si12P5 phase formed prior to the SiP phase. For samples with 35 and 44at.%P, the formation of SiP preceded the formation of the Si12.P5 phase. The experimentally determined phase formation sequences were successfully predicted by a proposed model. According to the model, the first and second crystalline phases to form are those with the lowest and next-lowest crystallization temperatures of the competing compounds predicted by the Gibbs free-energy diagram.

We used x-ray Bragg projection ptychography (BPP) to map spatial variations of ferroelectric polarization in thin film PbTiO3, which exhibited a striped nanoscale domain pattern on a high-miscut (001) SrTiO3 substrate. By converting the reconstructed BPP phase image to picometer-scale ionic displacements in the polar unit cell, a quantitative polarization map was made that was consistent with other characterization. The spatial resolution of 5.7 nm demonstrated here establishes BPP as an important tool for nanoscale ferroelectric domain imaging, especially in complex environments accessible with hard x rays.

In-situ X-ray diffraction during rapid thermal annealing at rates from 3 to 20°C s −1 was used to study the formation of titanium silicide phases from a thin film of Ti and doped single-crystal or undoped polycrystalline silicon substrates. In all cases, a metal-rich silicide (identified as either Ti 5 Si 4 or Ti 5 Si 3 ) was the first crystalline phase to form between 500 and 550°C, followed by C49-TiSi 2 between 575 and 600°C. The formation of C49-TiSi 2 completely consumed the metal-rich silicide before transforming into the low-resistance C54-TiSi 2 phase at approximately 800°C. These results indicate that while there is sufficient thermodynamic driving forces to nucleate both a metal-rich silicide and C49-TiSi 2 the subsequent growth of C49-TiSi 2 , is kinetically favored over the growth of Ti 5 Si 4 or Ti 5 Si 3 .

A time-resolved x-ray scattering study is presented of the faceting kinetics of a Si surface misoriented by 2.1{degree} from the cubic [113] direction towards [001]. Following a quench from a one-phase region of the phase diagram into a two-phase region, a grooved superstructure forms and subsequently coarsens in time. For times between one and several hundred seconds, the surface morphology is self-similar at different times, with a characteristic groove size ({ital L}) varying as a power law versus time ({ital t}): {ital L}={ital L}{sub 0}{ital t}{sup 0.164{plus_minus}0.021}. At later times, the groove size approaches a limiting value.

Asymmetrically cut perfect crystals, in both the Laue and Bragg geometries, are examined as single crystal monochromators for x‐ray beams that are collimated to a small fraction of the Darwin width, as is typical in experiments with coherent x rays. Both the Laue and asymmetric Bragg geometries are plagued by an inherent chromatic aberration that increases the beam divergence much beyond that of the symmetric Bragg geometry. Measurements from a recent experiment at the ESRF are presented to compare Si(220) (symmetric Bragg), diamond(111) (asymmetric Laue), and diamond(111) (symmetric Bragg inclined) geometries.

Physical review letters 109, 185502 (2012). doi:10.1103/PhysRevLett.109.185502, Published by APS, College Park, Md.

While GaAs(001) surface reconstructions have been studied extensively in the ultrahigh-vacuum environment associated with molecular-beam epitaxy (MBE), comparatively little is known of these structures in the chemically rich environment associated with organometallic vapor-phase epitaxy (OMVPE). This work presents a structural study of the [ital c](4[times]4) surface reconstruction stabilized in an arsenic-rich OMVPE environment. Measurements of the in-plane structure were performed [ital in] [ital situ] using grazing-incidence x-ray scattering with synchrotron radiation. Structural refinement confirms the presence of arsenic-arsenic dimers arranged with the [ital c](4[times]4) symmetry. In concurrence with similar studies performed in the MBE environment, it is found that the surface is a mixture of structural domains composed of two- and three-dimer variants of the [ital c](4[times]4) reconstruction. Atomic positions associated with these structures are presented. The size, aspect ratio, and orientation of the reconstructed regions are shown to be closely related to the atomic step geometry on the crystal surface.

Both double-crystal and triple-axis x-ray diffraction techniques have been used to study complex SiGe/Si structures. A novel method for measuring the nucleation activation energy of dislocations in strain relaxed SiGe/Si structures is presented to illustrate the usefulness of these techniques.

We present in situ surface x-ray scattering measurements of PbTiO3 epitaxy by metal–organic chemical-vapor deposition. Oscillations in crystal truncation rod intensity corresponding to layer-by-layer growth are observed under a variety of growth conditions. At lower PbO overpressures, we observe a transition to step-flow growth and an increased rate of recovery after growth, indicating a higher surface mobility.

We present a synchrotron x-ray study of the equilibrium polarization structure of ultrathin PbTiO(3) films on SrRuO(3) electrodes epitaxially grown on SrTiO(3) (001) substrates, as a function of temperature and the external oxygen partial pressure (pO(2)) controlling their surface charge compensation. We find that the ferroelectric Curie temperature (T(C)) varies with pO(2) and has a minimum at the intermediate pO(2), where the polarization below T(C) changes sign. The experiments are in qualitative agreement with a model based on Landau theory that takes into account the interaction of the phase transition with the electrochemical equilibria for charged surface species. The paraelectric phase is stabilized at intermediate pO(2) when the concentrations of surface species are insufficient to compensate either polar orientation.

Physical review letters 108, 024801 (2012). doi:10.1103/PhysRevLett.108.024801, Published by APS, College Park, Md.

Time-resolved x-ray scattering has been used to study the isothermal crystallization kinetics of the binary metal-boron glasses Co 2 B, Fe 76 B 24 , and Co 3 B, for crystallization times as short as ≃1 s. For alloys which crystallize into a single phase, a simple model of the transformed volume fraction, based on steady-state homogeneous nucleation of crystallites which then grow at a constant rate, explains the results. There is no evidence for a transient in the nucleation. A one-parameter fit to the slowest diffraction data allows volume fractions as small as 10 -4 to be measured. The observed crystallization kinetics agree well with calorimetric and resistivity measurements

Time-resolved X-ray scattering has been used to study the kinetics of crystallization of amorphous metals on time scales varying from minutes to milliseconds. Measurements have been at the National Synchrotron Light Source, using a wide-bandpass monochomator and fast linear position-sensitive detector system at the IBM/MIT beamline X-20C. With this apparatus, scattering patterns from the transforming material can be acquired with 3-ms time resolution. A fast pyrometric temperature controller has been developed to change and regulate the sample temperature with microsecond response. In a typical measurement, two synchronized position-sensitive detectors provide complementaryin situ information about the transformation. The first is used for wide-angle scattering and allows us to determine which phases are present and to what extent. Changes in lattice parameter and particle size can also be deduced. The second detector measures small-angle scattering, yielding additional information about the microstructure, such as the spacing between lammellae in eutectic systems. At relatively slow transformation rates, quantitative measurements of crystal volume fractions as small as 10−4 are possible. In many systems, as the transformation rate is increased, the crystallization mechanism changes such that new metastable crystal phases are formed en route to the equilibrium structure.

We have probed the microscopic distribution of 180° domains as a function of switching history in 40 nm epitaxial films of Pb(Zr0.30Ti0.70)O3 by analyzing interference effects in the x-ray scattering profiles. These as-grown films exhibit voltage offsets (imprint) in the polarization hysteresis loops, coupled with a strongly preferred polarization direction in the virgin state. Our x-ray results are consistent with models attributing the loss of switchable polarization to the inhibition of the formation of oppositely polarized domains in a unipolar matrix. Using such model epitaxial films, we demonstrate that different microscopic ensembles of domains resulting from, for example, fatigue, may be resolved by this technique.

Multilayer Laue Lenses (MLLs) were developed by us using dynamic diffraction effects to efficiently focus hard x-rays to very small spots. Using a partial MLL we were able to focus 19.5-keV hard x-rays to a line focus of 16 nm with an efficiency of 31%. A full MLL is a complete linear MLL structure. It can be fabricated by bonding two partial MLL wafers, or by growing the full structure using magnetron sputtering without bonding. A 40-{mu}m full MLL, with a total of 5166 layers of WSi{sub 2} and Si, has been successfully grown by sputter deposition. The layer thicknesses gradually vary from 4 nm to {approx}400 nm and then back to 4 nm. Two coating runs were used to grow the full structure, one for each half. It took over 56 h for each run. A 100-{mu}m nearly-full MLL was constructed by bonding. Each 50-{mu}m half-structure has 1788 WSi{sub 2} and Si layers with 12-nm to {approx}32-nm thicknesses and {approx}32-{mu}m total thickness, followed by a thick WSi{sub 2} layer of {approx}17 {mu}m, and an AuSn layer of {approx}1 {mu}m. Both full MLL structures survived dicing and polishing. The primary results demonstrate the feasibility and potential of a full MLLmore » with a doubled numerical aperture and large beam acceptance for hard x-rays.« less

We report the first time-resolved x-ray scattering study of the homoepitaxial growth of GaAs by organometallic vapor-phase epitaxy. The growth mode was determined to be layer-by-layer by observing ≃1-Hz oscillations of the x-ray intensity from the 11l crystal truncation rod near the 110 position. We show that the spatial distribution of islands can be dynamically determined by measuring the x-ray diffuse scattering near the 110. Finally, we show that significant correlations exist between the locations of islands during layer-by-layer growth

We present in situ x-ray scattering studies of surface morphology evolution during metal–organic chemical vapor deposition of GaN. Dosing the GaN(0001) surface with Si is shown to change the growth mode from step-flow to layer-by-layer over a wide temperature range. Annealing of highly doped layers causes Si to segregate to the surface, which also induces layer-by-layer growth.

By performing in situ, real-time x-ray diffraction measurements in the metalorganic chemical-vapor deposition environment, we have directly observed the emergence and evolution of wing tilt that occurs during the lateral overgrowth of GaN from stripes patterned in a SiO2 mask. This was done by repeatedly performing line scans through the 1013 peak in the direction perpendicular to the [1010]GaN stripe direction. The wing tilt developed as soon as the wings started forming, and increased slightly thereafter to reach a value of ∼1.19° after 3600 s of growth. Upon cooldown to room temperature, the tilt increased to ∼1.36°, indicating that thermally induced stresses during cooldown have only a small effect on wing tilt. However, changes in mask density, composition, and stress state during early lateral overgrowth must be considered as possible origins of wing tilt.

We demonstrate the dramatic effect of film thickness on the ferroelectric phase transition temperature Tc in strained BaTiO3 films grown on SrTiO3 substrates. Using variable-temperature ultraviolet Raman spectroscopy enables measuring Tc in films as thin as 1.6 nm, and a film thickness variation from 1.6 to 10 nm leads to Tc tuning from 70 to about 925 K. Raman data are consistent with synchrotron x-ray scattering results, which indicate the presence of 180 degrees domains below Tc, and thermodynamic phase-field model calculations of Tc as a function of thickness.

The hard X-ray nanoprobe at the Advanced Photon Source provides characterizing of composition and structure of nanoscale materials and devices with high spatial-resolution using x-ray fluorescence, diffraction and Bragg coherent diffraction, and full-field transmission imaging.

According to recent experiments and predictions, the orientation of the polarization at the surface of a ferroelectric material can affect its surface chemistry. Here we demonstrate the converse effect: the chemical environment can control the polarization orientation in a ferroelectric film. In situ synchrotron x-ray scattering measurements show that high or low oxygen partial pressure induces outward or inward polarization, respectively, in an ultrathin PbTiO3 film. Ab initio calculations provide insight into surface structure changes observed during chemical switching.

We report observations of self-sustaining spatiotemporal chemical oscillations during metal-organic chemical vapor deposition of InN onto GaN. Under constant supply of vapor precursors trimethylindium and NH{sub 3}, the condensed-phase cycles between crystalline islands of InN and elemental In droplets. Propagating fronts between regions of InN and In occur with linear, circular, and spiral geometries. The results are described by a model in which the nitrogen activity produced by surface-catalyzed NH{sub 3} decomposition varies with the exposed surface areas of GaN, InN, and In.

A high‐power proportional temperature controller, using a fast infrared pyrometer, has been developed to change and control the temperature of metallic ribbon samples with microsecond response. The apparatus provides uniform and controlled heating for time‐resolved x‐ray scattering studies of structural phase transitions. When high‐power pulse heating is used, the system is capable of increasing the sample temperature at rates in excess of 106 K/s, without overshoot and with subsequent control to ±1 K at temperatures as low as 650 K.

The kinetics of microphase separation and ordering of a diblock copolymer onto a lattice has been studied using time-resolved high-resolution small-angle x-ray scattering. The measurements show rapid formation of spherical domains after quenching and a subsequent ordering of the spheres. The results are discussed within the framework of simple models for nucleation and crystalli- zation.