Grazing Incidence X-ray Diffraction (GID) and Grazing Incidence Small Angle X-ray Diffraction (GISAXS)

Diffuse scattering appears in all materials as soon as any non-periodical disorder occurs. By tuning the incident X-ray energy close to atomic absorption edge energies, the atomic scattering amplitudes are changed and consequently the contribution to the scattering contrast in multi-component systems. This method is known as the anomalous scattering technique. Combined WAXS and SAXS measurements at a set of X-ray energies within the anomalous scattering regimes allow the extraction of the partial atomic pair correlations, as well as the detailed analysis of the scattering contrast for extended length scales. Elastic diffuse scattering studies in conventional scattering geometry (transmission and reflection) are therefore fundamental to understand structural properties in materials like:

  • liquids, molecular solutions, liquid crystals;
  • amorphous materials (glassy structures, semi-amorphous films with columnar structures for the magneto-optical data recording, solar cells as deposited by chemical vapour deposition, evaporation, sputtering processes)
  • poly- and nano-crystalline materials
  • single crystals with lattice point defects (vacancies, self- and impurity interstitials, compositional local short-range-order) or with larger defect clusters (e.g. precipitates in metallic alloys, microcracks in fatigued materials, inert gas bubbles in sputtered films, voids);
  • sponge-like porous materials (aerogels, porous silicon, zeolites)
  • macromolecules containing metallic atoms or partially substituted with heavy atoms.

The energy range 5 keV < E < 35 keV is sufficient for K-edge studies of elements in the range 22 < Z < 55. For Z > 55 one must use LIII edges. Sample thicknesses for experiments will still be in the µm range for transmission experiments. Below 5 keV, transmission experiments will become difficult due to the reduction of sample thickness. However, thin film studies will still be possible.

In conclusion, ID01 is not only of interest for materials research, but also for areas requesting low energy X-rays such as:

  • polymers (e.g. ionomers, sulphur containing polymers, polyelectrolytes);
  • biological membranes (e.g. sulphur in purple membrane);
  • biological fibres (phasing);
  • biological solutions (e.g. Ferritin).

It is hoped that many of these areas will benefit from the soft part of the x-ray spectrum.
The medium-high energy part of the X-ray spectrum is extensively exploited in measurements such as:

  • strain / composition in quantum dots.
  • microfocus.
  • surfaces and interfaces studyes, in air or in high vacuum, with the future possibility of in-situ UHV preparation.