Speaker
Description
Here we present our latest achievements regards diamond single crystal growth and characterization by means of X-ray diffraction. Synthetic diamond crystals were grown by the temperature gradient method using a high-pressure apparatus of the ‘‘split sphere’’ type (BARS) at P=5.7 GPa and T=1550 °C with the use of a Ni0.7Fe0.3 alloy as a solvent-catalyst. It has been shown that dislocation-free regions in these crystals occupy about 58 mm3. Two diamond plates oriented by (111) plane with 3x3 mm2 surface area were cleaved from the outer parts of two single crystals, followed by mechanical polishing from both sides. It was found that the plates contained nitrogen impurities predominantly in the form of isolated substitutional atoms (C-centers, type Ib) with concentrations in the range of 100–150 ppm.
Diamond plates were characterized by means of high-resolution rocking curve imaging (RCI) performed at P01 beamline at DESY. The samples were studied at room temperature in the Bragg geometry using monochromatic radiation with energy of 14.41 keV. The energy resolution provided by high-resolution Si (4 0 0)(10 6 4) monochromator was ∆E/E = 10-7. Rocking curves were collected from (333) reflection in a pixel-by-pixel manner by 2D-detector with 55-µm pixel size with a total surface area of 256x256 pixels. RCI showed an overall good quality of the diamond plates close to the central area. The FWHM mean value at the defect- and strain-free areas lie in scope of 0.5 µrad deviation from the theoretical value that is suitable for XFEL and 4th generation synchrotron sources optical applications like beam splitters and monochromators. Defect- and strain-free areas were found to be 1x2.2 and 1x1.6 mm2. The working area of the crystal #1 exceeds 50% of the whole crystal surface. Further improvement of the cutting in couple with polishing process will lead to the large Ib diamond crystals (more than 6 mm2) with larger working area.
