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Figure 2
A diagram illustrating the effects of orientational disorder on GIXS detector images transformed to reciprocal-space coordinate frame Qx,y,z and corrected for grazing incidence. This is a general example that can be applied regardless of the Q range collected. An atomic model is shown in the top row. The blue circles represent atomic components and the orange planes represent Bragg planes. The distance between the planes is 3 Å in this example. This distance is the only distance used to generate the example patterns, and all other Bragg planes and atomic distances are ignored for the purposes of this example. Short cylinders are used as a simplified picture for different grains in the depicted atomic model. The black arrows on the cylinders are normal to the orange Bragg planes and the orange arrows are in the plane of the Bragg plane. Below this, polycrystalline films with different extents of orientational order are shown. The axes Qx, Qy and Qz are chosen based on the substrate, with the Qz axis normal to the substrate and Qx and Qy in the plane of the substrate. Because the indium oxide films are intrinsically isotropic along the plane of the substrate, the horizontal axis may be labeled Qxy. The films range from a highly oriented film on the left to films with increasing extents of orientational disorder about the Qxy direction on the right. Directly below the different film types, the expected detector images are shown with Bragg peaks or Debye–Scherrer rings resulting from the example Bragg plane in red. Intensity in yellow represents specular reflection, which is masked (purple rectangle). The horizon line is shown in blue. In the bottom row are the transformed GIXS patterns, showing that the peak is broadened along the azimuthal axis for less oriented films. The missing wedge along the Qz direction arises from the lack of intersection between the Ewald sphere and the detection plane (Baker et al., 2010BB1). While this missing wedge is essential for oriented films, for wholly isotropic films, it is unnecessary, though it is still shown for each film to be consistent.

IUCrJ
Volume 11| Part 1| January 2024| Pages 120-128
ISSN: 2052-2525
https://doi.org/10.1107/S2052252523010357