ABSTRACT
In this section, we give several experimental examples of applications of coherent X-ray diffractive imaging for different systems.
First, we present results of CXDI applied to reveal the structure of a regular part and also a part containing a defect of a colloidal 2D crystal (see Ref. [53] for details). Self-organized colloidal crystals are an attractive material for modern technological devices. They can be used as the basis for novel functional materials such as photonic crystals, which may find applications in future solar cells, LEDs, lasers, or even as the basis for circuits in optical computing and communication. For these applications, the crystal quality is crucial and monitoring the defect structure of real colloidal crystals is essential [72]. The experiment [53] was performed at the microoptics test bench at the ID06 beamline of the European Synchrotron Radiation Facility (ESRF) using an incident X-ray energy of 14 keV. The geometry of the experiment allows for rotation of the sample around the vertical axis, which is perpendicular to the incident X-ray direction (see Fig. 12.10). A 6.9 µm pinhole was positioned at a close distance in front of the colloidal crystal. The pinhole selects a highly coherent part of the beam and produces a finite illumination area. The initial orientation of the sample (with azimuthal angle j = 0°) corresponds to the direction of the incident X-rays along the [111] direction of the face-centered cubic (fcc) colloidal crystal and was perpendicular to the surface normal of the sample. Rotating the sample around the x-axis allows the measurement of different sets of diffraction planes. Particularly important was the direction of the incident X-rays along the [110] direction of the colloidal sample lattice at j = 35°, when the set of (111) planes was aligned along the incident beam. The diffraction data were recorded using a CCD with 4,005 × 2,671 pixels with a resolution of Dq = 0.16 µm-1 per pixel. In the experiment, a thin film of a colloidal crystalline sample on a glass substrate was used. It was grown by the convective assembly technique using polystyrene microspheres (diameter 425 nm, relative standard deviation 5
percent). The grown crystalline films have an fcc structure and were typically 20-30 layers thick.
