Crystal truncation rod measurements using high energy x-rays and an area detector

One area of developmental interest for the HEMD instrument is to incorporate a 2D detector into measurements of crystal truncation rods (CTRs). Because the Ewald sphere is relatively flat at high x-ray energies, it is possible to intersect a sizable region along one (or more) CTRs. Collecting data along a large section will enable real-time measurements of surface structural modifications from chemical processes, such as catalysis reactions. Pilot measurements were made on a sample with faceted, nano-particles of Pd supported on a MgO substrate. A schematic of scattered x-rays captured with a 2D image is shown in Figure 31, as well as a portion of one image shown in Figure 32.Several CTRs from the nano-crystals are captured in one image, as well as the thermal diffuse scattering near the Bragg peaks from the MgO substrate. One region of interest near the Pd(111) peak is highlighted and shown in greater detail in Figure 32. The blue vertical line is along one CTR direction and the intensity variations are visible along the CTR. The red line indicates some mosaic spreads of the Pd particles. While the test measurements proved the concept can work, it will greatly benefit from increased x-ray flux and a higher efficiency 2D detector.

Schematic of scattered x-rays captured with a 2D image.	2D image of faceted, nano-particles of Pd supported on a MgO substrate.
Image near the Pd(111) peak. The blue line is along the CTR direction. The red line is a measure of mosaic spread in the Pd particles .	Intensity variation along the CTR is plotted in blue.