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Next-generation synchrotron radiation facilities, such as the Advanced Photon Source Upgrade (APS-U), bring significant advancements in scientific research capabilities, necessitating advanced diagnostic tools. Central to these diagnostics are x-ray wavefront sensors, crucial for preserving beam properties, including brightness, coherence, and stability. This paper presents two novel wavefront sensor prototypes developed at the APS using the coded-mask-based technique. The first is a compact design tailored for specific conditions and adaptability to diverse beamline configurations. The second, an adjustable zoom version, offers flexibility to accommodate a wide range of beam conditions. Both prototypes underwent rigorous testing at the APS 28-ID-B beamline and demonstrated their effectiveness in both absolute wavefront sensing and relative metrology modes. These results highlight their promise in beamline diagnostics, potentially enabling applications such as beamline auto-alignment and real-time wavefront manipulation. [ABSTRACT FROM AUTHOR]

The stacking sequence of hexagonal close-packed and related crystals typically results in steps on vicinal {0001} surfaces that have alternating A and B structures with different growth kinetics. However, because it is difficult to experimentally identify which step has the A or B structure, it has not been possible to determine which has faster adatom attachment kinetics. Here we show that in situ microbeam surface X-ray scattering can determine whether A or B steps have faster kinetics under specific growth conditions. We demonstrate this for organo-metallic vapor phase epitaxy of (0001) GaN. X-ray measurements performed during growth find that the average width of terraces above A steps increases with growth rate, indicating that attachment rate constants are higher for A steps, in contrast to most predictions. Our results have direct implications for understanding the atomic-scale mechanisms of GaN growth and can be applied to a wide variety of related crystals. The basal-plane surfaces of hexagonal close-packed crystals typically exhibit an alternating sequence of A and B steps with different atomic structures and growth kinetics. Here the authors demonstrate a method to determine whether A or B steps have faster kinetics under specific growth conditions. [ABSTRACT FROM AUTHOR]

Solid-phase epitaxy (SPE) and other three-dimensional epitaxial crystallization processes pose challenging structural and chemical characterization problems. The concentration of defects, the spatial distribution of elastic strain, and the chemical state of ions each vary with nanoscale characteristic length scales and depend sensitively on the gas environment and elastic boundary conditions during growth. The lateral or three-dimensional propagation of crystalline interfaces in SPE has nanoscale or submicrometer characteristic distances during typical crystallization times. An in situ synchrotron hard x-ray instrument allows these features to be studied during deposition and crystallization using diffraction, resonant scattering, nanobeam and coherent diffraction imaging, and reflectivity. The instrument incorporates a compact deposition system allowing the use of short-working-distance x-ray focusing optics. Layers are deposited using radio-frequency magnetron sputtering and evaporation sources. The deposition system provides control of the gas atmosphere and sample temperature. The sample is positioned using a stable mechanical design to minimize vibration and drift and employs precise translation stages to enable nanobeam experiments. Results of in situ x-ray characterization of the amorphous thin film deposition process for a SrTiO3/BaTiO3 multilayer illustrate implementation of this instrument. [ABSTRACT FROM AUTHOR]

In anticipation of the increased use of coherent X‐ray methods and the need to upgrade beamlines to match improved source quality, here the coherence properties of the X‐rays delivered by beamline 12ID‐D at the Advanced Photon Source have been characterized. The measured X‐ray divergence, beam size, brightness and coherent flux at energies up to 26 keV are compared with the calculated values from the undulator source, and the effects of beamline optics such as a mirror, monochromator and compound refractive lenses are evaluated. Diffraction patterns from slits as a function of slit width are analyzed using wave propagation theory to obtain the beam divergence and thus coherence length. Imaging of the source using a compound refractive lens was found to be the most accurate method for determining the vertical divergence. While the brightness and coherent flux obtained without a monochromator (`pink beam') agree well with those calculated for the source, those measured with the monochromator were a factor of three to six lower than the source, primarily because of vertical divergence introduced by the monochromator. The methods described herein should be widely applicable for measuring the X‐ray coherence properties of synchrotron beamlines. [ABSTRACT FROM AUTHOR]

We describe an instrument that exploits the ongoing revolution in synchrotron sources, optics, and detectors to enable in situ studies of metal-organic vapor phase epitaxy (MOVPE) growth of III-nitride materials using coherent x-ray methods. The system includes high-resolution positioning of the sample and detector including full rotations, an x-ray transparent chamberwall for incident and diffracted beam access over a wide angular range, and minimal thermal sample motion, giving the sub-micron positional stability and reproducibility needed for coherent x-ray studies. The instrument enables surface x-ray photon correlation spectroscopy, microbeam diffraction, and coherent diffraction imaging of atomicscale surface and film structure and dynamics during growth, to provide fundamental understanding of MOVPE processes. [ABSTRACT FROM AUTHOR]

In-situ synchrotron x-ray scattering has been used to monitor and control the synthesis of LaGaO3 epitaxial thin films by 90° off-axis RF-magnetron sputtering. Films deposited from a single LaGaO3 source were compared with those prepared by alternating deposition from separate La2O3 and Ga2O3 sources. The conditions for growth of stoichiometric films were determined by real-time monitoring of secondary phase formation as well as from features in the diffuse scatter from island formation during synthesis. These results provide atomic-scale insight into the mechanisms taking place during reactive epitaxial growth and demonstrate how in-situ techniques can be utilized to achieve stoichiometric control in ultrathin films. [ABSTRACT FROM AUTHOR]

Novel X-ray imaging of structural domains in a ferroelectric epitaxial thin film using diffraction contrast is presented. The full-field hard X-ray microscope uses the surface scattering signal, in a reflectivity or diffraction experiment, to spatially resolve the local structure with 70 nm lateral spatial resolution and subnanometer height sensitivity. Sub-second X-ray exposures can be used to acquire a 14 mm 14 mm image with an effective pixel size of 20 nm on the sample. The optical configuration and various engineering considerations that are necessary to achieve optimal imaging resolution and contrast in this type of microscopy are discussed. [ABSTRACT FROM AUTHOR]

The restricted volume above and below the sample on a six-circle diffractometer can limit the size and complexity of sample environments used in surface diffraction studies. An alternative configuration of the diffractometer, where the sample normal is aligned parallel to the χ axis, allows for ample space above and below the χ circle for instrumentation. The merits of this approach are outlined and angles are derived for the diffraction condition for constant-incident-angle, constant-sample-azimuthal-angle and specular geometries. Using a version of this code written for SPEC (http://www.certif.com/content/spec/), sample specular and nonspecular crystal truncation rods measured from a 5 nm-thick thin film are presented. [ABSTRACT FROM AUTHOR]

Using in situ synchrotron measurements of total reflection x-ray fluorescence, we find evidence of strontium surface segregation in (001)-oriented La0.7Sr0.3MnO3 thin films over a wide range of temperatures (25–900 °C) and oxygen partial pressures (pO2=0.15–150 Torr). The strontium surface concentration is observed to increase with decreasing pO2, suggesting that the surface oxygen vacancy concentration plays a significant role in controlling the degree of segregation. Interestingly, the enthalpy of segregation becomes less exothermic with increasing pO2, varying from -9.5 to -2.0 kJ/mol. In contrast, the La0.7Sr0.3MnO3 film thickness and epitaxial strain state have little impact on segregation behavior. [ABSTRACT FROM AUTHOR]