X-ray microdiffraction is used to analyze strain and composition profiles in individual micron-sized SiGe islands grown by liquid phase epitaxy on Si͑001͒ substrates. From the variation of the scattered intensity while scanning the sample through a focused x-ray beam of few m size, an image of the island distribution on the sample is created. Using this image it is possible to identify particular islands and select them for analysis one by one. The Ge and strain distribution within each island is obtained from the intensity distribution in reciprocal space measured for several individual islands. The detailed shape of each measured island is obtained from scanning electron microscopy. Apart from truncated pyramid-shaped islands, we detect and characterize a small number of flat islands and show that they represent an earlier growth stage of the pyramidal shaped ones. This analysis is only possible by combining the local x-ray diffraction with scanning electron microscopy on exactly the same islands.

Spectrographs take snapshots of photon spectra with array detectors by dispersing photons of different energies into distinct directions and spacial locations. Spectrographs require optics with a large angular dispersion rate as the key component. In visible light optics diffraction gratings are used for this purpose. In the hard x-ray regime, achieving large dispersion rates is a challenge. Here we show that multi-crystal, multi-Bragg-reflection arrangements feature cumulative angular dispersion rates almost two orders of magnitude larger than those attainable with a single Bragg reflection. As a result, the multi-crystal arrangements become potential dispersing elements of hard x-ray spectrographs. The hard x-ray spectrograph principles are demonstrated by imaging a spectrum of photons with a record high resolution of ∆E 90 µeV in hard x-ray regime, using multi-crystal optics as dispersing element. The spectrographs can boost research using inelastic ultra-high-resolution x-ray spectroscopies with synchrotrons and seeded XFELs.A dream x-ray spectrometer is actually a spectrograph that images x-ray spectra in one shot, and with an ultimate spectral resolution. State of the art single shot x-ray spectrometers [1][2][3][4] are imaging spectra with array detectors, using Bragg's law dispersion (BD). BD links the angle of incidence θ to the energy E of photons Bragg reflected from the crystal atomic planes. However, the spectral resolution of the BD-spectrometers is always limited by the Bragg reflection (Darwin) bandwidth.Angular dispersion (AD) is one way how to overcome the Darwin width limitation and substantially improved spectral resolution of x-ray optics [5,6]. AD is a variation of the photon angle of reflection θ , for a fixed incidence angle θ, with the photon energy E. AD takes place in Bragg diffraction, albeit only if the diffracting atomic planes are at a nonzero angle η = 0 (asymmetry angle) to the entrance crystal surface [5,7,8], see Fig. 1Unlike BD, AD links θ to E for a fixed θ. AD is independent of the Darwin width, and can be therefore used to resolve much narrower spectral features. Using angular-dispersive monochromators, x-rays were already monochromatized to bandwidths (0.45 meV) almost two orders of magnitude smaller than the width of the Bragg reflections (27 meV) involved [9]. New concepts are required, however, to realize single shot angular-dispersive spectrographs.We show here that multi-Bragg-reflection arrangements feature, in theory and in experiment, cumulative angular dispersion rates almost two orders of magnitude greater than those attainable in a single Bragg reflection. An angular-dispersive x-ray spectrograph of a Czerny-Turner-type [10] is introduced with the enhanced angular-dispersive optics as a "diffraction grating". A record high spectral resolution of ∆E 90 µrad is demonstrated in the hard x-ray regime.Czerny-Turner grating spectrographs are nowadays standard in infrared, visible, and ultraviolet spectro-scopies [11,12]. In its classical arrangement, the spectrographs ...

Photon and neutron inelastic scattering spectrometers are microscopes for imaging condensed matter dynamics on very small length and time scales. Inelastic X-ray scattering permitted the first quantitative studies of picosecond nanoscale dynamics in disordered systems almost 20 years ago. However, the nature of the liquid-glass transition still remains one of the great unsolved problems in condensed matter physics. It calls for studies at hitherto inaccessible time and length scales, and therefore for substantial improvements in the spectral and momentum resolution of the inelastic X-ray scattering spectrometers along with a major enhancement in spectral contrast. Here we report a conceptually new spectrometer featuring a spectral resolution function with steep, almost Gaussian tails, sub-meV (≃620 μeV) bandwidth and improved momentum resolution. The spectrometer opens up uncharted space on the dynamics landscape. New results are presented on the dynamics of liquid glycerol, in the regime that has become accessible with the novel spectrometer.

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