Grazing Incidence Techniques Research Articles

Opportunities and new developments for the study of surfaces and interfaces in soft condensed matter at the SIRIUS beamline of Synchrotron SOLEIL.

The SIRIUS beamline of Synchrotron SOLEIL is dedicated to X-ray scattering and spectroscopy of surfaces and interfaces, covering the tender to mid-hard X-ray range (1.1-13 keV). The beamline has hosted a wide range of experiments in the field of soft interfaces and beyond, providing various grazing-incidence techniques such as diffraction and wide-angle scattering (GIXD/GIWAXS), small-angle scattering (GISAXS) and X-ray fluorescence in total reflection (TXRF). SIRIUS also offers specific sample environments tailored for in situ complementary experiments on solid and liquid surfaces. Recently, the beamline has added compound refractive lenses associated with a transfocator, allowing for the X-ray beam to be focused down to 10 µm × 10 µm while maintaining a reasonable flux on the sample. This new feature opens up new possibilities for faster GIXD measurements at the liquid-air interface and for measurements on samples with narrow geometries.

Unwarping GISAXS data.

Grazing-incidence small-angle X-ray scattering (GISAXS) is a powerful technique for measuring the nanostructure of coatings and thin films. However, GISAXS data are plagued by distortions that complicate data analysis. The detector image is a warped representation of reciprocal space because of refraction, and overlapping scattering patterns appear because of reflection. A method is presented to unwarp GISAXS data, recovering an estimate of the true undistorted scattering pattern. The method consists of first generating a guess for the structure of the reciprocal-space scattering by solving for a mutually consistent prediction from the transmission and reflection sub-components. This initial guess is then iteratively refined by fitting experimental GISAXS images at multiple incident angles, using the distorted-wave Born approximation (DWBA) to convert between reciprocal space and detector space. This method converges to a high-quality reconstruction for the undistorted scattering, as validated by comparing with grazing-transmission scattering data. This new method for unwarping GISAXS images will broaden the applicability of grazing-incidence techniques, allowing experimenters to inspect undistorted visualizations of their data and allowing a broader range of analysis methods to be applied to GI data.

Diamond beamline I07: a beamline for surface andinterface diffraction.

Beamline I07 at Diamond Light Source is dedicated to the study of the structure of surfaces and interfaces for a wide range of sample types, from soft matter to ultrahigh vacuum. The beamline operates in the energy range 8-30 keV and has two endstations. The first houses a 2+3 diffractometer, which acts as a versatile platform for grazing-incidence techniques including surface X-ray diffraction, grazing-incidence small- (and wide-) angle X-ray scattering, X-ray reflectivity and grazing-incidence X-ray diffraction. A method for deflecting the X-rays (a double-crystal deflector) has been designed and incorporated into this endstation, extending the surfaces that can be studied to include structures formed on liquid surfaces or at liquid-liquid interfaces. The second experimental hutch contains a similar diffractometer with a large environmental chamber mounted on it, dedicated to in situ ultrahigh-vacuum studies. It houses a range of complementary surface science equipment including a scanning tunnelling microscope, low-energy electron diffraction and X-ray photoelectron spectroscopy ensuring that correlations between the different techniques can be performed on the same sample, in the same chamber. This endstation allows accurate determination of well ordered structures, measurement of growth behaviour during molecular beam epitaxy and has also been used to measure coherent X-ray diffraction from nanoparticles during alloying.

Advanced grazing-incidence techniques for modern soft-matter materials analysis.

The complex nano-morphology of modern soft-matter materials is successfully probed with advanced grazing-incidence techniques. Based on grazing-incidence small- and wide-angle X-ray and neutron scattering (GISAXS, GIWAXS, GISANS and GIWANS), new possibilities arise which are discussed with selected examples. Due to instrumental progress, highly interesting possibilities for local structure analysis in this material class arise from the use of micro- and nanometer-sized X-ray beams in micro- or nanofocused GISAXS and GIWAXS experiments. The feasibility of very short data acquisition times down to milliseconds creates exciting possibilities for in situ and in operando GISAXS and GIWAXS studies. Tuning the energy of GISAXS and GIWAXS in the soft X-ray regime and in time-of flight GISANS allows the tailoring of contrast conditions and thereby the probing of more complex morphologies. In addition, recent progress in software packages, useful for data analysis for advanced grazing-incidence techniques, is discussed.

A study of polymer thin-film formation on quartz substrate by X-ray grazing-incidence techniques

A study of polymer thin-film formation on quartz substrate by X-ray grazing-incidence techniques

Investigation of GaN quantum dot stacking in multilayers with X-ray grazing incidence techniques

The growth of GaN quantum dot multilayers embedded in an AlN matrix can be controlled using the Stranski–Krastanov mode. For samples grown in the wurtzite structure, we present a non-destructive statistical investigation of the structure and ordering of the GaN quantum dots, using X-ray grazing incidence techniques. With grazing incidence small-angle X-ray scattering we can quantify the strong vertical alignment of the dots. With grazing incidence diffraction, the strain in the multilayer is analyzed. We find that the GaN quantum dots are partially relaxed to a lattice parameter between the bulk value for GaN and that of the AlN lattice.

Structure and ordering of GaN quantum dot multilayer investigated by X-ray grazing incidence techniques

The growth of GaN quantum dot multilayers embedded in an AlN matrix can be controlled using the Stranski–Krastanov mode. For samples grown in the wurtzite structure, we present a non-destructive statistical investigation of the quantum dot shape, size and correlation, in both lateral and vertical directions using grazing incidence small angle X-ray scattering. In surface plane, the adjustment of the measurement leads to values for the size and the inter-dot distance that are consistent with direct characterization. In the vertical direction, the correlation length is quantified and shows the perfect vertical alignment of the dots.

Application of Grazing Incidence X-Ray Diffraction to Polymer Blends

AbstractThe physical properties of polymer blends consisting of one or more crystallizable components are affected by the microstructure of these materials. In particular, the degree of crystallinity can be influenced by processing parameters, and the crystallinity, as well as the phase distribution, may vary as a function of depth through an injection molded part. Conventional x-ray diffraction techniques can provide information regarding both phase composition and degree of crystallinity, but, because of the relative transparency of these materials to wavelengths generally available in the laboratory, these techniques provide information representative of only the bulk. By employing parallel beam optics at varying grazing incidence angles, the x-ray sampling depth can be varied without loss of resolution, This technique can be used to vary the effective analysis depth from the top several hundred angstroms for low grazing incidence to centimeters for transmission diffraction patterns, Grazing incidence techniques have found initial application in the characterization of thin metallic and ceramic films. This paper demonstrates the feasibility of using parallel beam optics to depth profile low atomic number materials. The specific application of this technique to the characterization of injection molded polymers, including a blend of bisphenol-A polycarbonate (PC) and polybutylene terephthalate (PBT), will be presented.

Multi-Spectral Solar Telescope Array

The development of multilayer optics has profound implications for soft x-ray/extreme ultraviolet (XUV) astronomy. During the October 1987 flight of the Stanford/Marshall Space Flight Center Rocket X-Ray Spectroheliograph, narrow wavelength band, low scatter soft x-ray/extreme ultraviolet spectroheliograms were obtained with -1 arcsec spatial resolution at X - 173 A (Fe IX, Fe X) and at is. - 256 A (He II Ly-3). Although the Cassegrain telescopes used in this experiment were small (63.5 mm diameter) and utilized spherical rather than paraboloidal/hyperboloidal mirrors, the images produced exceed in quality any XUV spectroheliograms previously obtained with either normal or grazing incidence techniques. We describe a new rocket spectroheliograph instrument, the Multi- Spectral Solar Telescope Array (MSSTA), that is currently being prepared for launch in August 1990. This instrumentwill utilizetrue Ritchey-Chrétien optics of 127 mm diameter and parabolic Herschelian optics of 40 mm diameter, which will allow spectroheliograms to be obtained over the soft x-ray/extreme ultraviolet/far ultraviolet spectral range (40 to 1550 A). The performance of this new instrument should definitely demonstrate the unique combination of ultrahigh spatial resolution and spectral differentiation that multilayer optics afford for astronomical observations. The MSSTA will also represent the first astronomical use of an important new optical device, the multilayer grating. The MSSTA should obtain unprecedented information regarding the structure and dynamics of the solar atmosphere in the temperature range i04 to i07 K.

Analysis of cobalt-doped iron oxide thin films by synchrotron radiation

Surface and bulk structures of as-deposited Fe 3O 4 and post-oxidized γ-Fe 2O 3 thin films were successfully identified by synchrotron diffraction analysis. A new synchrotron diffraction method which combines the Seemann-Bohlin and the grazing incidence techniques was used to record polycrystalline diffraction patterns for structure depth profiling analysis. The post-oxidized film was found to have an α-Fe 2O 3 layer at the surface and γ-Fe 2O 3 in the bulk of the film. The formation of a thermodynamically stable antiferromagnetic α-Fe 2O 3 surface caused the magnetically dead layer previously detected by neutron reflection analysis. Synchrotron diffraction results also showed that the structure of the as-deposited film remains constant throughout the thickness of the film. The presence of a superlattice (300) peak indicates the film has been oxidized beyond Fe 3O 4.